Besides hobnobbing with musical greats as an electric guitarist, Len Kaczmarek has fine-tuned the picture of how phosphorylation can alter neurons' electrical properties.
According to a former student, Len Kaczmarek is fond of noting: "Eric Clapton and I used to play the same clubs. Then our careers diverged." And it's true. Kaczmarek opened for Eric Clapton at Eel Pie Island and played guitar at the Royal Albert Hall. But then he swapped his guitar for a pipette—at least for a living—to help launch the field of neuromodulation, demonstrating for the first time that phosphorylation can change the electrical properties of ion channels and, ultimately, neuronal activity and animal behavior.
"The field of neuromodulation has become gigantic, and has led to all sorts of discoveries about how the brain works," says Yale's Elizabeth Jonas, a colleague and collaborator. "And Len is...
"The field of neuromodulation has become gigantic, and has led to all sorts of discoveries about how the brain works," says Yale's Elizabeth Jonas, a colleague and collaborator. "And Len is at its apex."
Kaczmarek's detour into science was largely happenstance. "At the time of my O-levels, which are taken when you're around 16, I happened to be doing better in my science classes," he says. "So the die was set." He was steered into taking chemistry and physics—not that he was any good at it. "As a teenager I was a terrible student," he says. "I remember telling my careers counselor that I was interested in biological things. He said, 'Well, you might try biochemistry. It's nowhere near as competitive as chemistry, so you might actually be able to get in.'"
Kaczmarek actually followed that advice and did his graduate work at the University of London, studying the amino acid taurine's role as a neurotransmitter. But in England the PhDs are very short—only three years from start to finish. "And at the end, I was still very young and naïve." So Kaczmarek decided to do multiple postdocs, which allowed him to really broaden his training. "As a postdoc, you're free to work on anything you like. And if you do three—as I did—you can explore different areas," he says.
During his first postdoc—with Russ Adey at University of California, Los Angeles—Kaczmarek learned how to do electrophysiology. "My PhD had been all biochemistry. And biochemistry's approach to understanding the brain is to smash it into little pieces. That approach been an amazingly productive, but I wanted to learn a more dynamic way of looking at what's going on in a living brain." After three years spent studying the release of neurotransmitters during epileptic seizures in the late 1970s, Kaczmarek decided to try his hand at some modeling. "I had read some papers about people doing mathematical models of how neurons fire. So I went to work with Ilya Prigogine in Brussels to start making neural network models."
"That training is now proving to be invaluable," says former postdoc Arin Bhattacharjee of the State University of New York in Buffalo. "So Len is doing a lot of simulations—putting in empirical information and playing with parameters—and using these programs to predict neuronal behavior—which is I think where a lot of neurobiology is going."
"Computer models were great," Kaczmarek says, "but you need to have something concrete to model." So for his third postdoc, he went to work on the sea slug Aplysia with Felix Strumwasser at Caltech. "For the first time, I was able to study a group of neurons where you could do it all," he says. "You could isolate them from other neurons, put them in a dish, and at the same time figure out what they were doing for the behavior of the animals." In particular, Kaczmarek was working with the so-called bag cell neurons that, when activated, release neurotransmitters that prompt the slugs to lay eggs.
"That's one of the great things about neuroscience: You can go from a molecule to a behavior," says Bhattacharjee. "And Len is that type of scientist. He's interested in the behavior, and in the molecules and cells that make that behavior happen. But he doesn't get lost in the details. He never loses sight of the big picture, of the larger goals of neuroscience."
It was during that final postdoc that Kaczmarek got his first glimpse of neuromodulation at work. It was 1980, and phosphorylation was all the rage. Everyone was tossing protein kinases into their favorite protein preps. So Kaczmarek got in touch with Rockefeller's Paul Greengard and borrowed a cup of cyclic AMP–dependent protein kinase, which he injected into his bag cell neurons. And he discovered that phosphorylation changed the ionic currents—or action potentials—produced by these cells. "At the time it wasn't an obvious experiment," says Kaczmarek. "People thought that neurons just generated these impulses and that there was no reason for biochemistry to get involved. Biochemistry was there to build the cell and make the neurotransmitters, not to mess with its electrical activity. So I think that study, along with others that were going on at the time, changed the way people looked at the excitability of neurons."
"You learn in school that an action potential is supposed to be all or none," says Jonas. "And this completely flies in the face of that dogma. Len was instrumental in making the first discovery that protein phosphorylation of ion channels could change the shape of an action potential and the firing pattern of a neuron."
As a faculty member at Yale, Kaczmarek went on to show which channels were involved in those changes and how phosphorylation altered their activities. "Len chose a very interesting system to study and then worked to reduce the problem to its molecular underpinnings," says former student William Joiner of the University of Pennsylvania School of Medicine. "I think that model of doing science has enabled his success. He has a good nose for the questions that are worth following."
Take, for example, his work on the MinK potassium channel protein in the late 1980s. "I was writing some questions for a physiology exam," says Kaczmarek, "and I read in a textbook about how estrogen generates action potentials in uterine smooth muscle." And because estrogen promotes protein synthesis, he thought maybe the hormone switched on production of an ion channel or two. So Kaczmarek prepared some mRNA from the uteri of estrogen-treated rats and injected it into Xenopus oocytes. "He saw this slowly activating potassium current that just didn't make a lot of sense," says Penn's Irwin Levitan, who has coauthored books on neuromodulation and neuronal biology with Kaczmarek. "A lot of people, me included, thought it was an artifact and would have let it go. But Len had the good sense to follow it up." And he isolated an RNA that encoded a protein that regulates the activity of an ion channel whose absence is responsible for some forms of heart failure.
"Len pays attention when something doesn't really fit, doesn't work the way he expects," says former student Julie Kauer of Brown University. "And he chases it down no matter where it leads—which is where I think the best science comes from."
His work on potassium channels was made possible by a sabbatical in Cambridge, where Kaczmarek learned how to clone genes from John Marshall, who was a graduate student at the time. "He showed me what to do every day," says Kaczmarek. "At the end of each day, I knew much more than I had the day before."
Back at Yale, that sabbatical experience launched what Joiner calls "the golden age of ion channel cloning" and made Kaczmarek "one of the first people to do molecular studies on mammalian potassium channels." Throughout the 80s and 90s, Kaczmarek and his lab cloned and characterized a cavalcade of key channels whose activities shape the behavior of the neurons in which they occur. "Some neurons fire spontaneously, some fire rhythmically, some you have to stimulate," says Bhattacharjee. "But this diversity of neuronal behavior basically all boils down to which ion channels the cells are expressing."
One channel they cloned, called Kv3.1, is present in high concentrations in the auditory system—a fact that was not lost on Kaczmarek. "Len instantly appreciated the potential importance of this particular channel in allowing auditory neurons to send signals very quickly," says Marshall, now a full professor at Brown. That sort of precise, rapid-fire communication allows animals—including humans—to localize sounds and to recognize different pitches. "When you play a tone at 440 Hz, there are neurons that are firing at exactly 440 Hz," says Kaczmarek. "When you switch to 445, they'll fire at 445. The action potentials will be timed very precisely to that sound." People who are musically trained or have finely tuned neurons can tell the two apart—which Kaczmarek likes to demonstrate during his seminars. "He'll take out his guitar and play two different pitches and ask the audience if they can hear the difference," says Jonas.
These channels also alter their activity in response to the ambient environment. Exposing rats to loud music—for example, a CD of Kaczmarek's biorock band Cellmates—phosphorylates Kv3.1 channels and, ultimately, changes the excitability of auditory neurons (results published in Nature Neuroscience in 2005).
"That really was stunning," says Ian Forsythe of the MRC Toxicology Unit at the University of Leicester, a colleague and collaborator. "When we looked at the immunohistochemistry and saw these cells had changed their staining depending on noise exposure, it was just so clear that this was going to be a really interesting story."
And Kaczmarek is good at telling scientific stories. "He communicates very effectively, which to my mind is really important," says Levitan. "You can do great experiments, but if you can't write about them or talk about them, they're useless to the community."
Music from "The Cellmates"
- 1. She's a Knockout
- 2. It's Just My Brain
- 3. Mitosis
Download Flash player to listen to The Cellmates
Forsythe agrees. "If I had one wish, I'd want to be able to write like Len does. His papers are always a pleasure to read. His arguments are clear and he's able to present his ideas and his work in a way that engages people and describes how the findings enhance our understanding of nervous system function. He definitely has a way with words—maybe because he's so keen on lyrics."
But Kaczmarek doesn't limit himself to lyrics. The Cellmates' most recent CD includes Kaczmarek's instrumental ode to potassium channels. And if you're wondering how one writes an instrumental about a potassium channel, Kaczmarek says, "you write an instrumental and then name it after a potassium channel."
If his music isn't exactly driven by his science, at least the two don't interfere, says Kaczmarek, who still performs in bars around Connecticut. "The music starts at 9 on Friday night and finishes up at 2 or 3 in the morning," he says. "I wouldn't be doing much science during those hours, anyway." And playing helps him regain his focus. "It's nice to have something that you do that isn't science," says Kaczmarek. "My brain gets depleted if I obsess and try to do too much work. I reach a dead end and I just can't think. Playing music refreshes my mind so I can start again fresh the next morning." Now that's neuromodulation.