STEMPod Leaders #8 - Dr. Robert Lefkowitz

Updated: Feb 8



Transcript



Goldrich: Welcome to STEMPod Leaders: conversations with today's great minds. My name is Nathan Goldrich, the founder of the STEMPod tutoring academic outreach program. Our guest today was born in the Bronx in 1943. His early interest in science led him to the Bronx School of Science and subsequently Colombia for undergraduate medical school. After spending a couple years at the National Institutes of Health, he moved to Durham, North Carolina, for the remainder of his career at Duke. In 2012, he won the Nobel Prize in chemistry for studies of G protein-coupled receptors. It is estimated that up to 50% of prescription drugs utilize the GPCR structure that he discovered. We are so lucky to have Dr. Robert Lefkowitz on the program and you can pre-order his memoir A Funny Thing Happened on the Way to Stockholm on Amazon. Thank you for being with us, Dr. Lefkowitz.

Dr. Lefkowitz: My pleasure indeed Nathan. I'm looking forward to talking with you.

Goldrich: What is so special about G protein-coupled receptors?

Dr. Lefkowitz: Well, this is a class of receptor molecules, and remember receptors are molecules in, or on, cells with which hormones and drugs and any kind of biologically active molecule might interact, so as to affect or influence or modulate the activities of cells and tissues and organs. We discovered quite a few years ago now, I would say about 30 years ago, that a number of these receptors share a very conserved structure. They're located in the plasma membrane the outer membrane of the cell and they weave through the membrane seven times like a snake okay. Each one of those times it passes through the membrane is called a transmembrane spanning domain, and so these are sometimes referred to as seven transmembrane spanning receptors, or seven trans or seven TR-span receptors. Now, what makes them so important is, as you suggested in your opening comment, that there are so many of these receptors. There are about a thousand different members of the family. We made our discoveries based on working with a single one called the Beta Adrenergic Receptor, which is a receptor which recognizes adrenaline, and that was sort of a model system for us. But after we discovered its structure, we and then others began to find more and more receptors that looked just like them. Essentially, they were members of what we call a gene family. This gene family in the end turned out to be one of the very largest if not the largest in the human genome. There are about a thousand different receptors in this family and what makes them so remarkable is the diversity of molecules that interact with them. For example, and I say for example only because there are a thousand of them, but in addition to adrenaline receptors, which are called adrenergic receptors, there are dopamine receptors, acetylcholine receptors, serotonin receptors, glucagon receptors, on and on and on, but it G protein-coupled receptors. For example, we smell using a huge family of hundreds, a subfamily of hundreds of G protein-coupled receptors, and the shorthand for G protein-coupled receptor just to save my breath is GPCR, so a number of our sensory modalities are mediated by that includes GPCRs and taste and, interestingly, and by taste not all modalities but in Sweden, and bitter for example, but also vision. Vision is mediated by interactions of photons of light with a GPCR called rhodopsin so at least three of our sensory systems are mediated by these GPCRs and then hundreds of different molecules and then, as you said, it turns out that these receptors, because they're so important in regulating human physiology, can serve as important targets for drugs and people estimate, as you said, anywhere from a third to a half of all FDA approved drugs that are available target these receptors. So it, their discoveries had a huge impact on clinical medicine and drug therapy

Goldrich: And how do medications that act on GPCRs work?

Dr. Lefkowitz: Well, in general they work in two different ways. They can either mimic what the endogenous agonist does, I’ll explain that more in a moment, or they can block it. So what do I mean by an endogenous agonist? Well there are basically two types two ways that molecules can interact with a receptor. One is, as an agonist that means it stimulates the receptor. The other is an antagonist that would mean it doesn't stimulate the receptor but it is like a lock. When the key fits into the lock, which you can only do if it has exactly the right complementary structure and it turns the key, the lock opens and now you get physiological things happening in the cell. For an antagonist you might picture a key sticking into the lock and then breaking off, so now you can't turn it. It can't stimulate anything but it blocks the ability of an agonist to get in there, that's an antagonist. Now mostly, almost exclusively actually, the various molecules in our body which interact with GPCRs are agonists. They would be things like adrenaline, histamine, serotonin, dopamine, things like that. Drugs which mimic those actions are used in a number of situations in clinical medicine. Just to give you an example, we would actually give adrenaline, or a number of synthetic congeners of adrenaline, to patients with asthma to dilate their airways. On the other hand, sometimes we want to block the actions of an endogenous. That means, something which we form in our own bodies, sometimes we want to block those actions. For example, let's say you develop a an allergic reaction to something and you're breaking out in hives. That's due to the release of histamine in your body from cells called mast cells, and those histamine molecules that are released interact with a histamine receptors and then set off a pathway of events that leads to all sorts of bad things. So what do we do? We give an antihistamine. An antihistamine is something, which, it's a drug which binds competitively to the histamine receptor like that broken off key, and blocks the ability of endogenous histamine to work, and many of the most useful GPCR directed drugs are antagonists. For example in the adrenergic system, that means the system related to adrenaline, so-called beta blockers, which is shorthand for beta adrenergic receptor blocker, it's the beta adrenergic receptor, the receptor which I studied for many, many years. Beta adrenergic receptors are found in blood vessels and the heart, amongst many other places, and when they are stimulated as, for example, if you are hiking uh in the woods and come upon a bear who then takes off after you, your adrenal glands release a lot of adrenaline and that makes your heart pump faster and stronger and you can get the hell out of there. So in a case like that, you're glad that you have that adrenaline pumping in your system and stimulating your receptors including the so-called beta adrenergic receptor. But in some people, even small amounts of adrenaline are raising their blood pressure and leading to heart trouble and elevated blood pressure. So for such patients, we want to block the effects of adrenaline and we give an antagonist, the so-called beta blocker, and there are quite a few of those that are available. So both types of drugs have their utilities.

Goldrich: Are agonists typically harder to design than antagonists?

Dr. Lefkowitz: No absolutely not, and one of the things that has made the GPCRs such a useful target as a group is that, for whatever reason, it seems to be relatively easy to find molecules which can bind into the receptor to have effects either as agonists or antagonists.

Goldrich: And if a receptor is mutated such that it's always active or it is unable to generate any secondary messenger processes what can drugs do in that type of situation?

Dr. Lefkowitz: Well, that's a very good question. There are examples of both congenital and acquired mutations in GPCRs which can lead to diseases. For example, you mentioned receptors which are active all by themselves, we have a name for that. We call those constitutively active receptors. There are a number of diseases which can be caused by such constitutively active receptors, let me give you a couple of examples. There's a receptor for what's called a gonadotropic hormone called the luteinizing hormone, or LH receptor. That receptor, together with another one called the FSH receptor - for follicle stimulating hormone receptor - are involved crucially in sexual development and certainly in in the process of going through puberty, but in young boys who have a constitutively activating mutation in the LH receptor, that means, normally that receptor wouldn't be stimulated until their pituitary gland starts making and releasing enough luteinizing hormone, or LH, to lead to puberty. But in these young boys, due to a congenital mutation, the receptor is active even though there's no, you know, there aren't high levels of LH circulating, and so they go through puberty at age two or three, which is a real problem. So in a case like that, you might want to give an antagonist that could basically shut the receptor down altogether, so that would be an example of that. There are also examples of receptors, which are defective for one reason or another, and in cases like that, the approach to treatment will very much depend on the specifics of what's going on. For example, if a receptor is only modestly impaired, then you might be able to get away by giving a high dose of an agonist. If it's totally impaired, then you got problems, and depending on how crucial the functioning of that receptor is, you might have a very sick patient. There are all kinds of other interesting mutations. For example, there are mutations, and some GPCRs, which do not negate or reduce their activity, but instead lead them to be internalized or taken up into the cell where, of course, they can't function because they need to function at the cell surface. So in in such cases, if you could just find a way of getting the receptor back out to the cell surface, it would be fine, and there are cases where such molecules, which are referred to as molecular chaperones, which bind to the receptor and then help it to be ushered back out to the plasma membrane where they can function, have been developed, and so those are, you know, several different examples of mechanisms by which drugs can overcome specific receptor mutations.

Goldrich: And as you were beginning to study receptors at Massachusetts General Hospital, what was it about beta adrenergic receptors that was so interesting to you?

Dr. Lefkowitz: That's a very good question, you know, in research, in scientific research the choice of what's called your model system is very, very important. If you choose a good model system, it may make it easier for you to make important discoveries, but if you choose a bad model system, it may slow or completely block your ability to make progress and one only knows whether one's chosen a good model system in retrospect, and it turned out that choosing the beta adrenergic receptor was one of the best scientific decisions I ever made. I couldn't know that at the time, so why did I choose that model system? Well, in my earlier work at the NIH, I had worked with trying to develop a way of studying a receptor for a molecule called ACTH, which stands for adrenocorticotropic hormone. That's a polypeptide hormone, molecular weight about 4,500, which stimulates the adrenal cortex to produce steroid hormones, like cortisone for example, and although that work eventually met with some success, it was very limited by the fact that there were no analogues of ACTH. So I had ACTH and that was it but I didn't have any other molecules that looked like ACTH. So when I got to the Mass. General and I was looking for a new model system and two very different lines of approach drew me to the beta adrenergic receptor, the one was that, there were dozens if not hundreds of chemical congeners and analogs of adrenaline, as well as dozens of antagonist molecules. Most of them had never been put into humans but from the point of view of trying to develop from scratch a whole system to study these things, I knew that I would not. Being a chemist myself, I knew I would be helped if I had access to many different structures which I could derivatize to, for example, try to develop radio ligands, which are radioactively labeled forms of drugs that I could use to study the receptors and various other things. So that was the practical reason for choosing it, but the emotional reason for choosing it is I was in the process of becoming a clinical cardiologist, and so I wanted to study a receptor for something which was relevant to cardiovascular disease, which ACTH is not as an example, but nothing could be more relevant than adrenaline and beta blockers, so that was the emotional reason. I was a young aspiring academic cardiologist and it seemed like it would tie in with my clinical work to be studying something more closely tied to the cardiovascular system, so there was both an emotional and a very practical reason for choosing it and you know, looking back with now almost 50 years of hindsight, I'm glad I did.

Goldrich: You mentioned that you use radio-like and binding assays to help study these receptors, but how were computer-based analytical models also able to help contribute to your discovery of new receptor subtypes?

Dr. Lefkowitz: Well that's an excellent question. So we had been working, we had developed these radiology and binding approaches which were really the key to opening up the whole field because prior to developing radio ligand binding methods, there was really no way to study a receptor and in fact, when I began my work 50 years ago, there was a lot of skepticism that there was any such thing as a receptor, certainly in terms of whether there was any physical chemical reality to a receptor molecule. So breaking the field open required the development of radio ligands and initially we were very happy to use those probes for things like counting the number of receptors on cells and how that varied with various diseases and interventions, or using it to tag the receptors as we began the difficult work of purify, isolating them, purifying them, finding out what they were, but then as we continued to study them, we began seeing unexpected features in the binding curves that we were getting. And it's kind of technical to get into so I won't, but agonists and antagonists were behaving differently in the binding studies. We didn't know what to make of it and I was able to recruit to my laboratory a young scientist named Andre de Leon, who was a real computer whiz. He was an M.D. Ph.D. and he was very adept even all those years ago at computer modeling of this kind of data, and so I recruited him to my lab specifically to look at these anomalous findings that we were getting that we didn't understand, and over a period of several years, he and I together developed certain models to explain the behavior and those models turned out to be completely general and very important, and led us to a whole new level of understanding of how the receptors worked and how in particular they functioned in relation to another protein called the G protein. And so you may wonder why do we call it G protein-coupled receptors, and the reason is that all of these receptors mediate their actions by binding to or interacting with another molecule called the G protein. The G stands for GTP, which is a guanine nucleotide and so it's really “guanine nucleotide regulatory protein” that the G stands for, so it's, GPCR is where that term comes from

Goldrich: By the time that you were 13 years old, you had completed Churchill's The Second World War and Sandberg's Abraham Lincoln Biography. As an avid reader from a young age, what is something valuable that you can get out of a book that you can't get out of a Google search?

Dr. Lefkowitz: Oh that's a wonderful question! You're right, I was a precocious reader as a child and I loved non-fiction. I guess, versus a Google search, when you're reading a good book, it's just so much deeper. There's so many more layers and color to it and in addition to all of the non-fiction I read, which is what you just mentioned as a youngster, I loved reading novels about doctors and in particular, I conceived the idea of becoming a physician at a very young age. I would say I was about eight years old. I was inspired by my family physician, a man named Joseph Fybush who made house calls in the Bronx, a general practitioner, and I just worshiped the guy and he would let me play with his stethoscope and stuff like that. But so, I took to reading novels about physicians and I found them very inspirational and for any of your students who might be listening to this, I would recommend several books that I read as a child, and not when I was eight years old but maybe in junior high school or high school, which portray physicians often in a heroic role and often functioning as physician scientists, which is what I am. One of these is called Arrowsmith by Sinclair Lewis and I believe it won a Pulitzer Prize. This was probably published in the 20s or the 30s and it still has resonance today. In fact, let's say I read it when I was 15, I'm now 77. Last year, I reread it. I rarely reread a book but I just wanted to see what it was about it that I found so inspirational. Another one is called The Citadel and I don't remember who wrote that. Another one, which is actually non-fiction, is called Microbe Hunters by Paul de Cruiff, and that's a series of vignettes about famous microbiologists like Pasteur and I found those books very, very inspirational in a way that I rarely find Google entries to be.

Goldrich: And you do mention that your interest in medicine was also sparked to some capacity by your family physician, what was it about the idea of performing physicals and writing illegible prescriptions that got you excited?

Dr. Lefkowitz: It was, so I think there were several things. One is I was always very curious and I loved to read and I came from a family background where knowledge was prized above all things. So here was a guy who, first of all, knew all kinds of things that other people didn't know. It's like he had access to secret stuff and then better yet, he could take all this secret knowledge that he had and apply it to make people feel better, to cure people. You know, I'd have a tummy ache or I would have diarrhea or a sore throat and you know, he could come in, lay on hands, and very quickly come to some rapid diagnosis, prescribe a medicine, and in no time at all I'd be feeling better, and it just seems to me, what could be better than that? To acquire all this special information and then be able to use it to make people feel better. So as I said, I was hooked, I figured this is as good as it gets.

Goldrich: And you also took to science pretty early on as you conducted your own observational research with solutions and microscopes. For people who are stuck at home right now, can you think of any fun experiment that you could perform out of your own home?

Dr. Lefkowitz: Oh that's a very good question! You know, I really don't know what kind of toys are available today, but when I was a youngster growing up, anybody like me who was interested in medicine or science would have two toys. One was what was called the chemistry set. I don't even know if such things exist, do they, I mean is there such a thing as a chemistry set? You never heard of it? These were toys that you would get for the holiday, I mean, it would come in a box and it was sort of like crayons. There was always a bigger one, right? I mean, you know, so depending on how much money your parents had, you have a little chemistry set that was tiny or you could have a huge one and they came with little bottles of reagents and books of instructions with experiments to perform. And you know, it was of course very elementary stuff you know, you would take two clear solutions of salts and pour them together and it would turn red, okay? Well you would take two clear solutions, you'd put them together, and you'd get a precipitate, okay? But I mean, for a ten-year-old kid, this was like, oh my God! The other great toy that we all had, it was a microscope because you could get [one] very cheap. It's actually toy microscopes, but they were real and so you know, you'd smash a bug and then you pull off its wing and you'd look at that, or uh you know, you would dig up some earth and try to see if you could find some kind of microorganisms growing in the dirt. These kinds of things, but today, I don't really know of any simple experiments that one could do. But you know the interesting thing about my early years, and by early I don't just mean as a youngster and a teenager, I mean right through medical school with [is ??] that, although I am, as I said, a physician and a scientist, but most people know me as a scientist. I mean, I won the Nobel Prize in chemistry, but until I was relatively late in my formal education, I had absolutely no interest in doing research and in fact, it did none, in fact I avoided doing research. Now, that might seem usual for somebody who had such a self-professed interest and passion for science especially the biological sciences, but also chemistry, but the thing is, I was so focused on the goal of becoming a practicing physician that I didn't want to waste time doing research, so when I was in college and I was in medical school and I had elective times when I could have done research, I didn't do it. In particular, in medical school we had assigned elective periods and when I was encouraged to do research, but I didn't do it. Instead, every elective period I used to take additional clinical training because I wanted to proceed directly to being a practicing doctor, so to me, I loved the science, I loved learning it but it was part of that special knowledge that I talked about which I wanted to then leverage to make people feel better. I wrote an autobiographical essay several years ago, your listeners may want to look it up, who's called “A Serendipitous Scientist.” It was published in the annual review of Pharmacology. So why do I describe myself as a serendipitous scientist? Well, there was a giant piece of serendipity which occurred in my life, without which, I never would have become a scientist and that was, believe it or not, the Vietnam War. So I graduated from medical school in 1966, at that time, the Vietnam War was raging and that was a vastly unpopular war. Many of us felt that it was an immoral, even illegal, war and many of us did not want to support it. In fact, it was a very controversial war that you may have read in your studies about how there were riots and demonstrations and all kinds of things. Now at the time, there was a lottery draft for all men over 18. That meant you were assigned the number and you got a draft card and then they would literally pull numbers out of a hat, and if your number came up, you were drafted, sent to Vietnam. And if your number didn't come up, then you were in the clear. But for physicians, there was a doctor draft that meant there was no lottery, everybody went in. So you were deferred through medical school and then you were drafted upon graduation. You were given a one or two year further deferral to get some additional clinical training as an intern, and maybe a year or two of residency, and then you went into one of the branches of the military for two years, and you served one of those two years in Vietnam almost without exception. Now that was not very popular as you can imagine and so everybody was scurrying around trying to figure out, how in the world am I going to avoid spending a year in Vietnam supporting a war that I think is wrong? Well, as they say there were very few legal options. One of them was to gain a commission as an officer in the United States Public Health Service. The United States Public Health Service was at the time, and it exists to this day, considered one of the military branches. So if you could gain a commission in the USPHS, that counted as your military draft in two years service. Now why was that desirable? Well, many of the assignments in the united states public health service were stateside because they staffed things like the prison system. They staffed the NIH, they staffed the CDC and many other research medical research installations. Well, as you can imagine it was very, very competitive to get such commissions. Everybody wanted them, so they were able to get the best and the brightest in a competitive process. I was fortunate because I had always done well academically, I was a top of my class and so I got that commission and was assigned to the NIH. At the NIH, you had two duties. For about 20% of your time you took care of the patients who were undergoing clinical trials at the clinical center of the NIH. But with 80% of your time, you were assigned to a research laboratory, okay. You were essentially a postdoctoral fellow working with, generally, a fairly talented principal investigator and so I did that for two years. Now, I was not there because I was dying to learn how to be a scientist. The only reason I was there was because I didn't want to go to Vietnam and I did- I had already by that time begun to fancy the idea of being an academic physician, and I had seen that, you know, those who seem to be successful were people who had some sort of laboratory activity. So I said, well okay, I’ll go for two years but it was not because, as I say, I was dying to be a scientist and in fact the one thing that I felt I learned with certainty during my first year there was I was not destined to be a scientist. I mean, nothing worked and that was very difficult for me because I had never really encountered much failure in my life, much less sustained failure that went on for more than a year and I was kind of really depressed with it. And so I decided, well research is not for me and since, as you know, you've got to always be making your plans a good year in advance. By the end of the first year, I had decided I was going to be done with this. A year ends and so I made arrangements to go to the Massachusetts General Hospital in Boston to finish my clinical training in internal medicine and cardiology, with the plan being to be a practicing clinical cardiologist. During the second year, as luck would have it, I began to meet with some success and in particular, during the final six months, my project really took off. I got to write a few papers, kind of caught the bug a little bit, but really not enough to change my plans, and so I went off to Boston. That's where I really had my epiphany. It was during the first six months at the Mass General as a senior medical room as I intensively threw myself back into acute clinical medicine at which, one I was very good, and two, which I always loved. But I realized after a few months that something was missing. Something was missing from my life and I was feeling kind of unfulfilled, which surprised me and then I realized what it was. I missed the stimulation of doing laboratory research. I missed the daily challenge of designing experiments, looking at data, figuring out why it didn't work, designing a better experiment, etc. And so at the end of those first six months at the Mass General, I made the realization that, look, I'm going to have to incorporate research in some way at some level into my career plans, and in fact, I found myself a mentor at the Mass General and for the remaining two and a half years, I was there. I did part-time research in his laboratory while completing my clinical studies and then I moved to Duke, as you said in 1973, as a young faculty member with appointments in medicine and biochemistry. And I was still at that point undecided as to exactly how my career was going to play out. I, at that point, considered myself a physician scientist but in terms of, you know, my career ahead and at the time [that] I arrived at Duke, I was only 30 years of age. In terms of how much of my time I was going to spend doing clinical work and how much I was going to spend doing research, I really didn't know, but I set out and I would say during the first year I might have spent 60 percent of my time in the lab and 40 doing clinical work. But then toward the end of the first year the research started to really take off and I found myself, without consciously making the decision, spending more and more time in the laboratory, 70/30, 80/20. I would say within three to five years I was already spending 80% of the time in the lab and then you know, within the first six or seven years I was probably down to 10% clinical work, 90% in the lab and that really persisted throughout my career. So sometimes when I talk about my career to students, I will title the talk A Tale Of Two Callings. Now, you know what a calling is. We normally associate a calling with clergy but you can feel a calling to any occupation or activity. It simply means that at some deep seated level, not necessarily rational at all, you feel that it is your destiny to do whatever and I certainly felt a calling to the practice of medicine when I was eight years old and I felt it the rest of my life. But I ultimately felt a calling to be a scientist, which one would have to say, in the end, was at least the straw if not stronger, because I wound up spending a lot more time doing it and if anybody would have told me as a youngster, as a college student, or even a medical student or as a house officer, that I would wind up spending the bulk of my career as a scientist and, God help us, win the Nobel Prize in chemistry, I would have said, what are you smoking! I mean, that makes no sense to me at all and so, I think the message for students listening to this is you have no idea what lies in your future, and that's one of the great wonderful things about life, is that even when you think you know exactly what you're going to be doing, which is certainly what I thought, it may turn out very, very different.

Goldrich: One thing that was interesting to me is you indicated that your commission allowed you to work at the NIH instead of being recruited to Vietnam. Do you think that, if this is, probably, an impossible question, but do you think that if you were recruited to Vietnam, you would still have eventually found your calling in science?

Dr. Lefkowitz: No, I think that, and then you make a very important point there, Nathan, is that in order to experience a calling, I think you need to be exposed to a particular activity and to role models and were it not for my exposure at the NIH, and the serendipity of that, I think I would have gone on to spend my life. And if I had gone to Vietnam, I would have spent my career happily practicing medicine. Now what I know, because of the way things turned out, as much as I would have enjoyed that, there's no way it would have been as gratifying for me as the dual career that I’ve had as a physician scientist, and I would like to put in a plug to students listening to this who think they want to be physicians, or others who think they want to be scientists, to give serious thought to combining the two activities. I can't imagine a more gratifying career than I have had as a physician scientist these past 50 years. You have the satisfaction of carrying out one of the most humane activities there is, bringing relief to the suffering and on occasion, saving a life. But on the other hand, you have the satisfaction of creating new knowledge. Knowledge which in and of itself can lead to treatments, which alleviates suffering, so it's really kind of two shots on goal in terms of alleviation of suffering. But it's also two shots on goal in terms of deriving job satisfaction from two totally different types of activities.

Goldrich: For people who are interested in learning about chemistry or biology or some form of physics, but lack of formal education from an undergraduate school or from a medical school, what is a good first step that can be taken today during COVID?

Dr. Lefkowitz: Well, I think that reading, to me, has always been the key to everything. Knowledge, knowledge is power and to me, the more you learn about things, the better. So if you're stuck at home and many of us are, I mean alas, I have not been to my laboratory since March but I continue to run the lab and all the exciting research via Zoom meetings, etc. But I suggest reading. I know that your generation and younger, I mean, love to read stuff online but I continue to put in a plug for reading books. One you might start with is this new memoir of mine that you might’ve mention in the beginning, A Funny Thing Happened on the Way to Stockholm. It's going to be published on February 2nd, but it's available for order now on Amazon. You can look it up but I think your students will find it inspirational in terms of how I came to find my way into medicine and science, and I think, I hope, they'll also find it very amusing because it's a funny book because I'm kind of a funny guy.


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