Author Archives: luysii

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Book Review — The Universe Speaks in Numbers

Let’s say that back in the day, as a budding grad student in chemistry you had to take quantum mechanics to see where those atomic orbitals came from.   Say further, that as the years passed you knew enough to read News and Views in Nature and Perspectives in Science concerning physics as they appeared. So you’ve heard various terms like J/Psi, Virasoro algebra, Yang Mills gauge symmetry, Twisters, gluons, the Standard Model, instantons, string theory, the Atiyah Singer theorem etc. etc.  But you have no coherent framework in which to place them.

Then “The Universe Speaks in Numbers” by Graham Farmelo is the book for you.  It will provide a clear and chronological narrative of fundamental physics up to the present.  That isn’t the main point of the book, which is an argument about the role of beauty and mathematics in physics, something quite contentious presently.  Farmelo writes well and has a PhD in particle physics (1977) giving him a ringside seat for the twists and turns of  the physics he describes.  People disagree with his thesis (http://www.math.columbia.edu/~woit/wordpress/?p=11012) , but nowhere have I seen anyone infer that any of Farmelo’s treatment of the physics described in the book is incorrect.

40 years ago, something called the Standard Model of Particle physics was developed.  Physicists don’t like it because it seems like a kludge with 19 arbitrary fixed parameters.  But it works, and no experiment and no accelerator of any size has found anything inconsistent with it.  Even the recent discovery of the Higgs, was just part of the model.

You won’t find much of the debate about what physics should go from here in the book.  Farmelo says just study more math.  Others strongly disagree — Google Peter Woit, Sabine Hossenfelder.

The phenomena String theory predicts would require an accelerator the size of the Milky Way or larger to produce particles energetic enough to probe it.  So it’s theory divorced from any experiment possible today, and some claim that String Theory has become another form of theology.

It’s sad to see this.  The smartest people I know are physicists.  Contrast the life sciences, where experiments are easily done, and new data to explain arrives weekly.

 

 

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What is legionella trying to tell us?

10 years out of Med School, a classmate in the Public Health service had to deal with the first recognized outbreak of Legionnaire’s disease, at the Bellevue Stratford hotel in Philly, about one air mile from Penn Med where we went.   The organism wasn’t known at the time and caused 182 cases with 29 deaths.  We’ve learned a lot more about Legionella Pneumophila since 1976 and the organism continues to instruct us.

The most recent lesson concerns one of the 300 or so proteins Legionella injects into a cell it attacks.  This is remarkable in itself.  The organism uses them to hijack various cellular mechanisms to build a home for itself in the cell (the LCV — Legionella Containing Vacuole).  Contrast this with diphtheria which basically uses one protein (diphtheria toxin) to kill the cell.

One of the 300 proteins is called SidJ and looks like a protein kinase (of which our genome has over 500).  However [ Science vol. 364 pp. 787 – 792 ’19 ] shows that SidJ carries out a different different reaction.SidJ is activated by host-cell calmodulin to polyglutamylate the SidE family of ubiquitin (Ub) ligases inhibiting them. Crystal structures of the SidJ-calmodulin complex reveal a protein kinase fold that catalyzes ATP-dependent isopeptide bond formation between the amino group of free glutamate and the gamma carboxyl group in the catalytic center of SidE a ubiquitin ligase.   This, instead of just esterifying the hydroxyl group of serine or threonine or tyrosine with the terminal phosphate of ATP as a kinase is supposed to do.

Why is this important? The only protein known to have polyglutamic acid added to it is tubulin, the protein from which microtubules (neurotubules to the neurologist).  The work is important because some of the 500+ protein kinases in our genome might be doing something else.  Has the chemistry each and every member of the group been studied?  Probably not..

The authors close with “In summary, our results underscore the diversity and catalytic versatility of the protein kinase superfamily. We propose that ATP-dependent ligation reactions may be a common feature among the vast diversity of eukaryotic protein kinase–like enzymes found in nature (25). There are more than 500 protein kinases in humans and our results suggest that they should be ex- amined for alternative activities.”

I couldn’t agree more.

Memorial day war stories

Tomorrow is memorial day, so it’s time for some stories about how various wars have affected family and friends.

First a still living 92 year old vet I met at Harvard Graduate Alumni day a few years ago.  He piloted a landing craft at the Normandy invasion.  After the war he entered Harvard Law, didn’t like it and got a masters in History.  Last seen a month ago, and in great shape having retired from a career that you’d never guess.

OK guess !  What do you think he did?

He was a successful football coach in the NFL — Marv Levy of the Buffalo Bills.

Second, third, fourth and fifth — family members.

Uncle #1 kept it quiet that he was on the Rutgers rifle team, was an officer in the MPs. He was stationed in India and China.  He had a weekly?/monthly? beer ration to distribute to his men and figured out a way to get them cold beer in India in the 1940’s.  Can you guess what he did?

Pilots in India would fly materiel over the hump (Himalayas) to China, in unheated airplanes.  For a cut they’d fly the beer over and back cooling it.  My wife told this story to a friend of hers at a workshop.  Her eyes got wider and wider, saying ‘the beer story’.  Her father had been one of the pilots.

Uncle #2 became an artillery officer, stationed in New Guinea and the Philippines, and later Japan.  In New Guinea one of the men thought he saw something move and fired his rifle (not a gun).  The bullet bounced off a rock coming back, and he and his men fought an hours long battle against the rocks.  He didn’t there was a Japanese soldier within miles.

He was absolutely convinced that the atomic bomb saved his life, as next up was the invasion of Japan. It would have been bloody, even 6 years ago in Kyoto and Osaka I saw little old men wearing caps of the Japanese defense forces.

Uncle #3 was a doc pushed through med school in 3 years (as they all were back then).  He was at the battle of Kasserine Pass in North Africa.  Despite what you may read about it, he said that the generals were quite frightened of Rommel, as reconnaissance was minimal and they had no idea where he was.

As is typical of men who have been in war they didn’t talk about it much.  Uncle #2 also went to Rutgers, and I saw him there in the 90s at a reunion with his roommate a very small man.  Later uncle #2 told me that the little guy had been in the Battle of the Bulge.  I found this amazing and later told uncle #3 about it, who said that he was also in the Battle of the Bulge — this 50 years or so later and the first time I’d heard of it.

The fourth family member was possibly the bravest of all.  He was a German Jew who managed to escape Europe landing in England where he was given a new identity.  He became a commando and was dropped behind enemy lines in France before the Normandy invasion.  Of course he spoke perfect German, but you can only imagine what might have happened had he been caught and they found out what he was.  He became a family member after the war as he married my father’s cousin. A very mild mannered individual.

All four led productive lives after the service, with no PTSD disability etc. etc. I think one used the GI bill.  Just as the war changed the orientation of Herman Wouk, so did it change uncle #3 who lies buried in a military cemetery.

Which brings me up to the Vietnam war.  A high school classmate who became a dentist was over there in the early years.  The country has a hot dry season and a hot wet season.  They had open air showers to remain comfortable, but it was disconcerting to him to have villagers standing around looking at how hairy we was.  Lots of hair is not a survival value in such a place and the Vietnamese are a relatively hairless lot.

I was an Air Force Captain in the Medical Corps stationed at one of the best army hospitals (Fitzsimons in Denver) because they were short of neurologists.  Now Vietnam is like Chile, a long strip of a country along a coast.  As a result, no wounded soldier was more than 20 minutes away by chopper from a fully equipped surgical field hospital, so the people surviving were far more gravely injured than those in world war II.

I thought we took very good care of our patients, far better than at the University of Colorado Medical Center where I finished up my residency after discharge.  They were fat and happy with the nearest academic medical center 500 miles away (St. Lake City, Omaha etc. etc.) resulting in no competition.

The only brave thing I did  while in the service was writing a letter to the General resigning from the officer’s club, because some little Nazi there refused to let a psych resident from Colorado who was helping us out into the club because he had a beard.  I can still see the little bastard’s smirk as he said he was ‘just following orders’.  I was sure I’d be shipped out to Plok Tic or something like it the next day, but the general (who was in the medical Corps) wrote to the resident apologizing and the rule was changed.

Now I don’t want to fight the Vietnam war again, but there is one further thing you should know.  The tour of duty in Vietnam was 1 year, but the term of service for docs was two.  (Back then I asked one of my uncles what the term of service was in WWII — what do you think it was?   Answer — until the war was over). The people coming back after one year pretty much had their pick of the best places, and many wound up at Fitzsimons.  I talked (and worked with) a lot of them.  These were not career military with an axe to grind.  Not one of them thought we were winning.  This was ’68 – ’70 when I was in.

RIPK1

The innate immune system is intrinsically fascinating, dealing with invaders long before antibodies or cytotoxic cells are on the scene.  It is even more fascinating to a chemist because it works in part by forming amyloid inside the cell.  And you thought amyloid was bad.

The system becomes even more fascinating because blocking one part of it (RIPK1) may be a way to treat a variety of neurologic diseases (ALS, MS,Alzheimer’s, Parkinsonism) whose treatment could be improved to put it mildly.

One way to deal with an invader which has made it inside the cell, is for the cell to purposely die.  More and more it appears that many forms of cell death are elaborately programmed (like taking down a stage set).

Necroptosis is one such, distinct from the better known and studied apoptosis.   It is programmed and occurs when a cytokine such as tumor necrosis factor binds to its receptor, or when an invader binds to members of the innate immune system (TLR3, TLR4).

The system is insanely complicated.  Here is a taste from a superb review — unfortunately probably behind a paywall — https://www.pnas.org/content/116/20/9714 — PNAS vol. 116 pp. 9714 – 9722 ’19.

“RIPK1 is a multidomain protein comprising an N-terminal kinase domain, an intermediate domain, and a C-terminal death domain (DD). The intermediate domain of RIPK1 contains an RHIM [receptor interacting protein (rip) homotypic interaction motif] domain which is important for interacting with other RHIM-containing proteins such as RIPK3, TRIF, and ZBP1. The C-terminal DD mediates its recruitment by interacting with other DD-containing proteins, such as TNFR1 and FADD, and its homodimerization to promote the activation of the N-terminal kinase domain. In the case of TNF-α signaling, ligand-induced TNFR1 trimerization leads to the assembly of a large receptor-bound signaling complex, termed Complex I, which includes multiple adaptors (TRADD, TRAF2, and RIPK1), and E3 ubiquitin ligases (cIAP1/2, LUBAC complex).”

Got that?  Here’s a bit more

“RIPK1 is regulated by multiple posttranslational modifications, but one of the most critical regulatory mechanisms is via ubiquitination. The E3 ubiquitin ligases cIAP1/2 are recruited into Complex I with the help of TRAF2 to mediate RIPK1 K63 ubiquitination. K63 ubiquitination of RIPK1 by cIAP1/2 promotes the recruitment and activation of TAK1 kinase through the polyubiquitin binding adaptors TAB2/TAB3. K63 ubiquitination also facilitates the recruitment of the LUBAC complex, which in turn performs M1- type ubiquitination of RIPK1 and TNFR1. M1 ubiquitination of Complex I is important for the recruitment of the trimeric IκB kinase complex (IKK) through a polyubuiquitin-binding adaptor subunit IKKγ/NEMO . The activation of RIPK1 is inhibited by direct phosphorylation by TAK1, IKKα/β, MK2, and TBK1. cIAP1 was also found to mediate K48 ubiquitination of RIPK1, inhibiting its catalytic activity and promoting degradation.”

So why should you plow through all this?  Because inhibiting RIPK1 reduces oxygen/glucose deprivation induced cell death in neurons, and reduced infarct size in experimental middle cerebral artery occlusion.

RIPK1 is elevated in MS brain, and inhibition of it helps an animal model (EAE).  Mutations in optineurin, and TBK1 leading to familial ALS promote the onset of RIPK1 necroptosis

Inflammation is seen in a variety of neurologic diseases (Alzheimer’s, MS) and RIPK1 is elevated in them.

Inhibitors of RIPK1 are available and do get into the brain.  As of now two RIPK1 inhibitors have made it through phase I human safety trials.

So it’s time to try RIPK1 inhibitors in these diseases.  It is an entirely new approach to them.  Even if it works only in one disease it would be worth it.

Now a dose of cynicism.  Diseased cells have to die one way or another.  RIPK1 may help this along, but it tells us nothing about what caused RIPK1 to become activated.  It may be a biomarker of a diseased cell.  The animal models are suggestive (as they always are) but few of them have panned out when applied to man.

 

At a funeral

As I sat at a funeral for a friend’s wife 8 days ago, I thought how little the congregation (and most people) comprehend about we’ve been given.  The service was about eternal life and faith in it.  Faith isn’t easy apparently, and requires work to achieve and maintain.  While acquiring the chemistry, physics and math to understand molecular biology requires work, seeing it make accurate predictions and accepting the truth of the conceptual schemata required to even think of the experiments requires no faith at all

A bit about the deceased.  A lovely, talented, intelligent very beautiful woman who married a college classmate.  3 sons, 4 granddaughters as beautiful tall and graceful as she was. So she clearly has continuing (if not eternal) life.  When I first met her at our 50th college reunion, she appeared so young and so beautiful, that I immediately put my foot in my mouth and asked her if she was XXX’s second wife.

So I’m sitting there thinking about Duchenne dystrophy, and the transcription of the 2 million basepair gene for dystrophin with removal of 99.5% of the transcript before the mRNA is sent out the cytoplasm, wondering why we’re not all in wheelchairs, and how the congregation has no clue about any of this, as they sit there making and consuming their body weight in ATP over the course of a day.

Theodicy would no longer be a problem for the religious if they had any conception of just how miraculous our existence is.

Do molecular biologists have faith?  I think most do, since most appear to believe that intricate cellular metabolism and the molecular machines that make life possible just arose by random events with selection of the fittest.  Actually I don’t think that most think about these matters at all.  They certainly don’t publish about it, and doing so when I was a blogger for Nature Chemistry, got me bounced.

The more we find out about how we work internally, the more miraculous it becomes (to me at least) providing evidence for a creator.  It’s back to reverend Paley and the found watch.

I’ll close with this

It was pretty hard to be a doc back in the 60s and 70s watching good people suffer and die, and still conceive of a benevolent creator. “The Plague” by Camus with its hideous death scene of a child pretty much sums up the argument against one.

And yet, now that we know so much more molecular biology, cellular and organismal biochemistry and physiology, our existence seems totally miraculous. I at least have achieved a sense of peace about illness, suffering and death. These things seem natural. What is truly miraculous is that we are well and functional for so long.

You can take or leave the argument from design of Reverend Paley — here it is

“”In crossing a heath, suppose I pitched my foot against a stone, and were asked how the stone came to be there; I might possibly answer, that, for anything I knew to the contrary, it had lain there forever: nor would it perhaps be very easy to show the absurdity of this answer. But suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place; I should hardly think of the answer I had before given, that for anything I knew, the watch might have always been there. … There must have existed, at some time, and at some place or other, an artificer or artificers, who formed [the watch] for the purpose which we find it actually to answer; who comprehended its construction, and designed its use. … Every indication of contrivance, every manifestation of design, which existed in the watch, exists in the works of nature; with the difference, on the side of nature, of being greater or more, and that in a degree which exceeds all computation.”

The more chemistry and biochemistry I know about what’s going on inside us, the harder I find it to accept that this arose by chance.

This does not make me an anti-evoloutionist. One of the best arguments for evolution, is the evidence for descent with modification, one of its major tenets. The fact that we can use one of our proteins to replace one on yeast using our present genetic technology is hard to explain any other way.

Actually to me now, the existence or nonexistence of a creator is irrelevant. The facts of how we are built is not something you need faith about. The awe about it all comes naturally the more we know and the more we find out.

Forgotten but not gone — take III

It’s pretty clear that life originated in the RNA world.  Consumed by thinking of proteins, enzymes, DNA etc. we tend to forget that there is a lot of RNA out there doing things we didn’t suspect.  Here are two more examples, one of which may explain why even genes coding  for proteins are relatively free of codons transcribed into amino acids.  The champ of course is dystrophin, discussed in the last post — https://luysii.wordpress.com/2019/05/05/duchenne-muscular-dystrophy-a-novel-genetic-treatment/.  The gene is a monster with  2,220,233 nucleotides coding for just 3,685 amino acids, meaning that less than 1/200th of the gene is actually coding for protein. The work below should make us think about just what else the 199/200th of dystrophin might be doing,

Unsuspected use of RNA #1.   [ Neuron vol. 102 pp. 507 – 509, 553 – 563 ’19 ]  The Tumor protein p53 inducible nuclear protein 2 (Tp53inp2) gene codes for a low complexity protein of 222 amino acids, all in one exon.  However the ‘3 untranslated region (3’UTR)  of the RNA for it is nearly 5 times longer (3,121 nucleotides) vs. 666 amino acid coding nucleotides.  The protein is made from the mRNA in some cells, but not in sympathetic neurons, even though the mRNA for Tp53inp2 is the most abundant RNA in the axons of these neurons.

Why do animals lick their wounds?  Because their saliva contains nerve growth factor (NGF) among other things.  NGF is crucial for the growth of sympathetic neuron axons, and their very survival in embryonic life.  It is a protein, which binds to a receptor for it (TrkA) on the axon membrane.  The receptor/NGF complex is then internalized and transported back to the nucleus turning on the genes necessary for axon growth and cell survival.

Even though the mRNA for Tp53inp2 is NOT translated into protein in the axon, it is crucial for the internalization of TrkA/NGF.

People have studied proteins whose function it is to bind RNA for years.  They are called RBPs (RNA Binding Proteins), and our genome has 750 of them.  200 RBPs are associated with genetic disease.  This work turns everthing on its head.  Here is an RNA whose function it is to bind a protein (e.g. TrkA).

How many more mRNAs have nonCoding (for protein) parts with other functions?

Unsuspected use of RNA #2. Circular RNAs had been missed for years (although known since 1976).  The classic sequencing methods isolate only RNAs with characteristic tails (such as polyAdenine).  Circular RNAs don’t have any.    They are formed by back splicing of 3′ end of exon N to the 5′ end of exon N.  Fortunately this is only 1% as efficient as the normal way.

So what?  Circular RNAs are crucial in the innate immune response to microbial invaders.  Double stranded DNA belongs inside the nucleus.  When it gets into the cytoplasm when some organism brings it there,it binds to Protein Kinase R (PKR) activating it so it phosphorylates eukaryotic initiation factor 2 (eiF2) bringing protein synthesis to a screeching halt.

This means that the cell needs a mechanism to keep PKR quiet.  This is where circular RNAs come in   [ Cell vol. 177 pp. 797 – 799, 865 – 880 ’19 ].  If the nucleotides in the circle can reach across the circle and base pair with each other forming a duplex of any length, it will bind to PKR inhibiting it.  Most circular RNAs are expressed at only a handful of copies/cell, the cell containing just 10,000 of them.

The work found that overexpression of a single circular RNA able to form duplexes (dsRNA) inhibits PKR.  Over expression of linear RNA of the same sequence does not, nor does overexpression of circular RNA which can’t form dsRNA.

So when an invader with dsDNA or dsRNA gets into the cell, RNAase L, a cytoplasmic endonuclease is activated, cleaving circular RNA, and uninhibiting PKR.

So it’s back to the drawing board for mRNA and those parts (introns, 3’UTRs) we didn’t think were doing anything.  Perhaps that’s why there are so many of them, and why they take up more room in mRNA and genes than the ones coding for amino acids.  Also it’s time to look at RNAs as protein binders and modifiers, rather than the other way around as we have been doing.

Here’s a link to an earlier member of the series — https://luysii.wordpress.com/2019/04/15/forgotten-but-not-gone-take-ii/xa

Duchenne muscular dystrophy — a novel genetic treatment

Could the innumerable genetic defects underlying Duchenne muscular dystrophy all be treated the same way?  Possibly.  Paradoxically, the treatment involves actually making the gene  even worse.

Understanding how and why this might work involves a very deep dive into molecular biology.  You might start by looking at the series of five background articles I wrote — start at https://luysii.wordpress.com/2010/07/07/molecular-biology-survival-guide-for-chemists-i-dna-and-protein-coding-gene-structure/ and follow the links.

I have a personal interest in Duchenne muscular dystrophy because I ran such a clinic from ’72 to ’87 watching young boys and adolescents die from it.  The major advance during that time, was NOT medical or anything I did, but lighter braces, so the boys could stay ambulatory longer.  Things have improved as survival has improved by a decade so they die in their late 20s.

So lets start.  Duchenne muscular dystrophy is caused by a mutation in the gene coding for dystrophin, a large (3,685 amino acids) protein which ties the contractile apparatus of the muscle cell (actin and myosin) to the cell membrane. Although it isn’t the largest protein we have — titin, another muscle protein with 34,350 amino acids is, the gene for dystrophin is the largest we have, weighing in at 2,220,233 nucleotides.  This is why Duchenne is one of the most common diseases due to a defect in a single gene, the gene is so large that lots of things can (and do) go wrong with it.

The gene comes in 79 pieces (exons) which account for under 1/200 of the nucleotides of the gene.  The rest must be spliced out and discarded.  Have a look at http://www.dmd.nl.  to see what can go wrong — the commonest is deletion of parts of the gene (60 – 70% of cases), followed by duplication of other parts (10% of cases) with the rest being mutations that change one amino acid to another.

Duchenne isn’t like cystic fibrosis where some 600 different mutations in the causative CFTR gene were known by 2003 but with 90% of cases due to just one.  So any genetic treatment for that young boy sitting in front of you had better be personalized to his particular mutation.

Or should it?

Possibly not.  We’ll need to discuss 3 things first

l. Nonsense Mediated Decay (NMD)

2. Nonsense Induced Transcriptional Compensation (NITC).

3. The MDX mouse model of Duchenne muscular dystrophy

Nonsense mediated decay.  Nonsense is a poor term, because the 3 nonSense codons (out of 64 possible) tell the ribosome to stop translating mRNA into protein and drop off the mRNA.  That isn’t nonsense.  I prefer stop codon, or termination codon

An an incredibly clever piece of business tells the ribosome (which is after all an inanimate object) when a stop codon occurs too early in the mRNA when there are a bunch of codons afterwards needed to make up the whole protein.

Lets go back to dystrophin and its 79 exons, and the fact that 99.5% of the gene is made of introns which are spliced out.   Remember the mRNA starts at the 5′ end and ends at the 3′ end.  The ribosome reads and translates it from 5′ to 3′. When an intron is spliced out, a protein complex of several proteins is placed on the mRNA some 20 – 24 basepairs 5′ to the splice site (this happens in the nucleus way before the mRNA gets near a ribosome in the cytoplasm).  The complex is called the Exon Junction Complex (EJC). The ribosome then happily munches along the mRNA from 5′ to 3′ knocking off the EJCs as it moves, until it hits a termination codon and drops off.

Over 95% of  genes do not have introns after the termination codon.  What happens if it does? Well then it is called a premature termination codon (PTC) and there is usually an EJC 3′ (downstream) to it.  If a termination codon is present 50 -55 nucleotides 5′ (upstream) to an EJC then NMD occurs.

Whenever any termination codon is reached, release protein factors (eRF1, eRF3, SMG1) bind to the mRNA.  It there is an EJC around (which there shouldn’t be) the interaction between the two complexes triggers phosphorylation of one of EJC proteins, triggering NMD.

So that’s how NMD happens, when there is a PTC.  Clever no?

Nonsense Induced Transcriptional Compensation (NITC).  I realize that this is a lot to throw at you, but a treatment for Duchenne is worth the effort (not to mention other genetic diseases in which the mechanism to be described also applies).

NITC is something I never heard about until two papers appearing in the 13 April Nature (vol. 568 pp. 179 – 180 (editorial), 193 – 197, 259 – 263).  Ever since we could knock out by placing a PTC early (near the 5′ end) of the gene we’ve been surprised by some of the results –e.g. knocking out some genes thought to be crucial had little or no effect.  Other technologies which didn’t affect the gene, but which decreased the expression of the mRNA (such as RNA interference, aka Post-Transcriptional gene silencing — PTGS) did have big phenotypic effects.

This turns out to be due NITC, which turns out to be due to increased transcription of genes which are ancestrally related to the mutant. Gene.  Hard to believe.

Time to go back to NMD.  It doesn’t break mRNA down nucleotide by nucleotide, but fragments it.  These fragments get into the nucleus, and bind to complementary genomic sequences of the PTC gene, and also to genes ancestrally related to the mutant gene (so they’ll have similar nucleotide sequences). Then epigenetics takes over because the fragments recruit the COMPASS complex which catalyzes the formation of H3K4Me3 which is part of the histone code which helps turn on transcription of the gene.  The sequence similarity of ancestrally related genes, allows them and only them to be turned on by NITC.  Even cleverer than finding a PTC by the ribosome.

Something so incredible needs evidence.  Well heterozygotic zebrafish can bemade to have one normal gene and one with a PTC. What do you think happens?  The normal gene is upregulated (e.g. more is made).  Pretty good.

Finally the Mdx mouse.  I’ve been reading about it for years.  It has a PTC in exon 23 of the dystrophin gene, resulting in a protein only 27% as long as it should be.  All sorts of therapeutic maneuvers have been tried on it.  Now any drug development chemist will tell you that animal models are lousy, but they’re all we’ve got.

The remarkable thing about the mdx mouse, is that they don’t get weak.  They do have muscle pathology.  All the verbiage above probably explains why.

So to treat ALL forms of Duchenne put in a premature termination codon (PTC) in exon #23 of the human gene. It should work as there are  4 dystrophin related proteins scattered around the genome — their names are — utrophin, dystrophin related protein 2 (DRP2), alpha dystrobrevin, and beta dystrobrevin

There is an even better way to look for a place to put a PTC in the dystrophin gene.  Our genomes are filled with errors — for details see — https://luysii.wordpress.com/2018/05/01/how-badly-are-thy-genomes-oh-humanity-take-ii/.

There are lots of very normal people around with supposedly lethal mutations (including PTCs) in their genomes.  Probably scattered about various labs are at least 1,000,000 exome sequences in presumably normal people.  I’m not sure how much clinical information about them is available (other than that they are normal).  Hopeful their sex is.  Look at the dystrophin gene of normal males (females can be perfectly healthy carrying a mutant dystrophin gene as it is found on the X chromosome and they have 2) and see if PTCs are to be found.  You can’t have a better animal model than that.

At over 1,000 words this is the longest post I’ve written, and hopefully the most useful.

Why drug development is hard #32 and #33

The bloodbath among drug chemists continues (see Derek’s recent posts — https://blogs.sciencemag.org/pipeline/archives/2019/04/22/big-pharma-cuts-current-and-coming) because drug development is very hard and success is rare. Two nearly back to back papers in PNAS show just how hard drug development is (and why).

Animal models of human disease have a poor track record in pointing to new drugs.  One reason is that humans have new genes that animals don’t. One example is the horribly named CHRFAM7A, a dominant negative inhibitor of the alpha7 nicotinic cholinergic receptor [ PNAS vol. 116 pp. 7932 – 7940 ’16 ].

Alpha7 is found on macrophages where it exerts an anti-inflammatory action. Alpha7 agonists work beautifully in rodent inflammatory disease models.  They crashed and burned in human trials.  Why?  Because CHRFAM7A  binds to Alpha7 blocking the ability of acetyl choline to bind to it.  It is a totally new gene for man. It arose when 5 exons of the UL kinase 4 gene on chromosome #3 translocated nd then fused with the Dupa gene, which itself originated with 5 exons partially duplicated from the 10 exon alpha7 gene on the forward strand of chromosome #15.  So CHRFAM7A in close proximity to alpha7 (about which much more in the next post) and structurally similar to it.

[ PNAS vol. 116 pp. 7957 – 7962 ’19 ] Practically next door is a paper about MI-2, a drug thought to be useful in a (fortunately) rare brain tumor of childhood — diffuse intrinsic pontine glioma (maybe 3 cases in 38 years of practice).  Menin is a tumor suppressor lacking in a less rare syndrome (Type I Multiple Endocrine Neoplasia). MI-2 inhibits menin, but this paper shows that this isn’t its mechanism of action. Rather it inhibits an enzyme on the biosynthetic route to cholesterol (lanosterol synthetase).  So even when you think you know what a drug should be doing (which is probably why MI-2 was developed), that may not be how it works.

Forgotten but not gone — take II

The RNA world from whence we sprang strikes again, this time giving us a glimpse into its own internal dynamic.  18 months ago I wrote the following post — which will give you the background to follow the latest (found at the end after the (***)

Life is said to have originated in the RNA world.  We all know about the big 3 important RNAs for the cell, mRNA, ribosomal RNA and transfer RNA.  But just like the water, sewer, power and subway systems under Manhattan, there is another world down there in the cell which doesn’t much get talked about.  These areRNAs, whose primary (and possibly only) function is to interact with other RNAs.

Start with microRNAs (of which we have at least 1,500 as of 12/12).  Their function is to bind to messenger RNA (mRNA) and inhibit translation of the mRNA into protein.  The effects aren’t huge, but they are a more subtle control of protein expression, than the degree of transcription of the gene.

Then there are ceRNAs (competitive endogenous RNAs) which have a large number of binding sites for microRNAs — humans have a variety of them all with horrible acronyms — HULC, PTCSC3 etc. etc. They act as sponges for microRNAs keeping them bound and quiet.

Then there are circular RNAs.  They’d been missed until recently, because typical RNA sequencing methods isolate only RNAs with characteristic tails, and a circular RNA doesn’t have any.  One such is called CiRS7/CDR1) which contain 70 binding sites for one particular microRNA (miR-7).  They are unlike to be trivial.  They are derived from 15% of actively transcribed genes.  They ‘can be’ 10 times as numerous as linear RNAs (like mRNA and everything else) — probably because they are hard to degrade < Science vol. 340 pp. 440 – 441 ’17 >. So some of them are certainly RNA sponges — but all of them?

The latest, and most interesting class are the nonCoding RNAs found in viruses. Some of them function to attack cellular microRNAs and help the virus survive. Herpesvirus saimiri a gamma-herpes virus establishes latency in the T lymphocytes of New World primates, by expressing 7 small nuclear uracil-rich nonCoding RNAs (called HSURs).  They associate with some microRNAs, and rather than blocking their function act as chaperones < Nature vol. 550 pp. 275 – 279 ’17 >.  They HSURs also bind to some mRNAs inhibiting their function — they do this by helping miR-16 bind to their targets — so they are chaperones.  So viral Sm-class RNAs may function as microRNA adaptors.

Do you think for one minute, that the cell isn’t doing something like this.

I have a tendency to think of RNAs as always binding to other RNAs by classic Watson Crick base pairing — this is wrong as a look at any transfer RNA structure will show. https://en.wikipedia.org/wiki/Transfer_RNA.  Far more complicated structures may be involved, but we’ve barely started to look.

Then there are the pseudogenes, which may also have a function, which is to be transcribed and sop up microRNAs and other things — I’ve already written about this — https://luysii.wordpress.com/2010/07/14/junk-dna-that-isnt-and-why-chemistry-isnt-enough/.  Breast cancer cells think one (PTEN1) is important enough to stop it from being transcribed, even though it can’t be translated into protein.

*****

[ Proc. Natl. Acad. Sci. vol. 116 pp. 7455 – 7464 ’19 ] The work reports a fascinating example of that early world in which the function of one denizen (a circular RNA called cPWWP2A) binds to another denizen of that world (microRNA 579 aka miR-579) acting as a sponge sopping up so it can’t bind to the mRNAs for angiopoetitin1, occludin and SIRT1.

So what you say?  Well it may lead to a way to treat diabetic retinopathy. How did they find cPWWP2A?  They used the Shanghai BIotechnology Company Mouse Circular RNA microArray which measures circular RNAs.  They found that 400 or so that were upregulated in diabetic retinopathy and another 400 or so that were downregulated.  cPWWP2A was on of the 3 top upregulated circular RNAs in diabetic retinopathy.  cPWWP2A comes from (what else?) PWWP2A, a gene coding for a protein which specifically binds the histone protein H2A.Z.

Overexpression of cPWW2PA or inhibition of miR-579 improves retinal vascular dysfunction in experimental diabetes.

So here is all this stuff going on way down there in the RNA world, first interacting with other players in this world and eventually reaching up to the level we thought we knew about and controlling gene expression.  It’s sort of like DOS (Disc Operating System) still being important in Windows.

How much more stuff like this is to be discovered controlling gene expression in us is anyone’s guess

How complicated can neuropharmacology be?

A revolution is occurring in our thinking about the neurochemistry and treatment of depression.  Spectacular therapeutic results with ketamine imply that neurotransmission with glutamic acid is involved (see the older post below for the background)  In addition gamma amino butyric acid (GABA) may also be a player.  That’s why a recent review [ Neuron vol. 102 pp. 75 – 94 ’19 ] is worth a careful reading.

Like all new fields, early results are particularly confusing. In particular the statement was made that in addition to NMDA receptor blockers (such as ketamine) positive allosteric modifiers (PAMs) of the NMDAR also are therapeutic in depression (the latter in animal models only, a phase III trial in depression having failed).

So I wrote the lead author ”

Great review, but how do you reconcile the rapid antidepressant action of the NMDAR blocker ketamine and friends and an NMDAR PAM (positive allosteric modifier)”

I got the following back —

We have data indicating that ketamine blocks NMDA receptors on GABA neurons resulting in disinhibition and increased synaptic activity of principle neurons, whereas the PAM (rapastinel) acts directly on NMDA receptors on principle neurons to produce a similar downstream effect

It didn’t make sense that drugs having opposite effects on the same therapeutic target (the NMDAR) would have the same therapeutic effect.

So I wrote

If I understand you correctly, this implies that the subunit composition of the NMDARs at the two sites (GABA interneurons and principal neurons) is different.

I got the following back, which is positively Talmudic in its logical intricacy.

It could be the same receptor complex; because ketamine is an open channel blocker the GABA neurons, which are more active, would be more sensitive because activity is required to remove the Mg+2 block in the channel and thereby allow ketamine to enter and block the channel. The PAM does not require activity and could act at directly on principle neurons.

If this is correct, a lot of neuropharmacology on drug effects will require rethinking.  What does the readership think?

Stock tip — update

The FDA approved esketamine (Spravato) last week (see copy of original post at the end).  I had recommended buying Johnson and Johnson if the FDA approved it.  I think it’s a good long term buy, but there is no rush for the following reason — Esketamine is not a drug you can get a prescription for and take on you own. Because of the psychiatric side effects it must be administered in a SPRAVATO REMS.

Risk Evaluation and Mitigation Strategy (REMS): SPRAVATO™ is available only through a restricted program called the SPRAVATO™ REMS because of the risks of serious adverse outcomes from sedation, dissociation, and abuse and misuse.

Important requirements of the SPRAVATO™ REMS include the following:

  • Healthcare settings must be certified in the program and ensure that SPRAVATO™ is:
    • Only dispensed in healthcare settings and administered to patients who are enrolled in the program.
    • Administered by patients under the direct observation of a healthcare provider and that patients are monitored by a healthcare provider for at least 2 hours after administration of SPRAVATO™.
  • Pharmacies must be certified in the REMS and must only dispense SPRAVATO™ to healthcare settings that are certified in the program.

So you can’t go to some shady practitioner who’ll say you have treatment resistant depression and get some (e.g. the pill pushers for opiates, ‘medical’ marihuana  etc. etc.)

So there aren’t going to be hordes of users right away, although the stuff I’ve read implies that there will be eventually.

If you have a subscription to Cell have a look at vol. 101 pp. 774 – 778 ’19 by the guys at Yale who did some of the original work.  If not content yourself with this.

They are refreshingly honest.

Was the Discovery of Ketamine’s Antidepressant Serendipitous?Of course. However, its discovery emerged from the testing of a novel mechanistic hypothesis related to the pathophysiology of depression.”

Basically the authors rejected the regnant theory of depression, namely that the cause was to be found in monoamine neurotransmission (e.g. by dopamine, norepinephrine, serotonin).  There was some evidence that the cerebral cortex was involved in depression (not just the monamine nuclei of the brainstem), so they looked at the two major neurotransmitters in brain (glutamic acid, and GABA), and chose to see what would happen if they blocked one of the many receptors for glutamic acid, the NMDA receptor.  They chose ketamine to do this.
Here’s what they found,  A single dose of ketamine produced antidepressant effects that began within hours peaked in 24 – 72 hours and dissipated within 2 weeks (if ketamine wasn’t repeated).  This was in 50 – 75% people with treatment resistant depression.  Remarkable 1/3 of treated patients went into remission.    There simply has never been anything like this, which is why I thought the drug would be a blockbuster.
There is a lot of speculation about just which effect of esketamine is crucial (increase in glutamic acid release with AMPAR stimulation, brain derived neurotrophic factor (BDNF) release, TrkB receptor stimulation, mTORC1 activation, local protein synthesis, restoration of functional connectivity in functional MRI.   In animals one sees a rapid proliferation of dendritic spines.
As promised – here’s a copy of the first post

Stock tip

The past performance of stock recommendations is no guarantee that it will continue — which is fortunate as my first tip (ONTX) was a disaster.  I knew it was a 10 to one shot but with a 100 to 1 payoff.  People play the lottery with worse odds.  Anyway ONTX had a rationale — for the gory details see — https://luysii.wordpress.com/2016/06/01/in-a-gambling-mood/

For those brave souls who followed this recommendation (including yours truly) here’s another.

On 4 March 2019 if the FDA approves esketamine for depression, buy Johnson and Johnson.  Why?  Some people think that no drug for depression works that well, as big Pharma in the past only was reporting positive studies.  The following is from Nature 21 February 2019.

Depression drug A form of the hallucinogenic party drug ketamine has cleared one of the final hurdles towards clinical use as an antidepressant. During a 12 February meeting at the US Food and Drug Administration (FDA) in Silver Spring, Maryland,an independent advisory panel voted 14 to 2 in favour of recommending a compound known as esketamine for use in treating depression.

What’s so hot about esketamine?  First its mechanism of action is completely different than the SSRIs, Monoamine oxidase inhibitors, or tricyclic antidepressants.

As you likely know, antidepressants usually take a few weeks to work at least in endogenous depression.  My clinical experience as a neurologist is slightly different, as I only used it for patients with disease I couldn’t help (end stage MS etc. etc.) where the only normal response to the situation was depression.  They often helped patients within a week.

I was staggered when I read the following paper back in the day.  But there was no followup essentially.

archives of general psychiatry volume 63 pp. 856 – 864 2006
The paper is not from St. Fraudulosa Hospital in Plok Tic, but from the Mood Disorders Research Unit at the National Institute of Mental Health.
Here are the basics from the paper

Patients  Eighteen subjects with DSM-IV major depression (treatment resistant).

Interventions  After a 2-week drug-free period, subjects were given an intravenous infusion of either ketamine hydrochloride (0.5 mg/kg) or placebo on 2 test days, a week apart. Subjects were rated at baseline and at 40, 80, 110, and 230 minutes and 1, 2, 3, and 7 days postinfusion.

Main Outcome Measure  Changes in scores on the primary efficacy measure, the 21-item Hamilton Depression Rating Scale.

Results  Subjects receiving ketamine showed significant improvement in depression compared with subjects receiving placebo within 110 minutes after injection, which remained significant throughout the following week. The effect size for the drug difference was very large (d = 1.46 [95% confidence interval, 0.91-2.01]) after 24 hours and moderate to large (d = 0.68 [95% confidence interval, 0.13-1.23]) after 1 week. Of the 17 subjects treated with ketamine, 71% met response and 29% met remission criteria the day following ketamine infusion. Thirty-five percent of subjects maintained response for at least 1 week.

Read this again: showed significant improvement in depression compared with subjects receiving placebo within 110 minutes after injection, which remained significant throughout the following week.

This is absolutely unheard of.  Yet the paper essentially disappeared.

What is esketamine?  It’s related to ketamine (a veterinary anesthetic and drug of abuse) in exactly the same way that a glove for your left hand is related to a right handed glove.  The two drugs are optical isomers of each other.

What’s so important about the mirror image?  It means that esketamine may well act rather differently than ketamine (the fact that ketamine worked is against this).  The classic example is thalidomide, one optical isomer of which causes horrible malformations (phocomelia) while the other is a sedative used in the treatment of multiple myeloma and leprosy.

If toxic side effects can be avoided, the market is enormous.  It is estimated that 25% of women and 10% of men will have a major depression at some point in their lives.

Initially, Esketamine ( SPRAVATOTM)  will likely be limited to treatment resistant depression.  But depressed people will find a way to get it and  their docs will find a way to give it.  Who wants to wait three weeks.  Just think of the extremely sketchy ‘medical indications’ for marihuana.