It's Electric

By Karen Hopkin It’s Electric One Saturday afternoon in the lab of Erwin Neher changed the entire field of electrophysiology. © Irene Boettcher-Gajewski, MPIbpc. At first, Erwin Neher didn’t realize what he was looking at. He and his colleague Bert Sakmann—who occupied adjoining labs at the Max Planck Institute for Biophysical Chemistry in Göttingen starting in the 1970s—had been trying to perfect a technique for watch

Karen Hopkin
Feb 28, 2010

It’s Electric

One Saturday afternoon in the lab of Erwin Neher changed the entire field of electrophysiology.

© Irene Boettcher-Gajewski, MPIbpc.

At first, Erwin Neher didn’t realize what he was looking at. He and his colleague Bert Sakmann—who occupied adjoining labs at the Max Planck Institute for Biophysical Chemistry in Göttingen starting in the 1970s—had been trying to perfect a technique for watching individual ion channels do their thing. Working with isolated frog muscles and an oscilloscope, the pair had already seen what appeared to be the signature trace of channel proteins flickering open in response to the neurotransmitter acetylcholine. But the signal was anything but clean.

“With these single-channel recordings, the thing you’re always fighting is noise,” says Yale’s Fred Sigworth, who had just joined Neher’s lab as a postdoc. “So you’d approach the cell with your pipette and you’d see this very noisy current”—a reflection of the thermal...

“It was unbelievable,” says Neher. “After having worked for 4 or 5 years toward such a goal—after having tried everything we could think of without success—all of a sudden it happened by itself.” The total disappearance of the familiar, noisy signal was so startling, in fact, Neher didn’t know what to make of it at first. “We thought for some reason the tip of the pipette had clogged up,” he says. “So we would discard those readings and start a new experiment.”

Then one weekend, one of those flatline readings suddenly showed “these very nice, rectangular pulses,” he says. “The very thing we had wanted to see.” Those pulses represented the movement of ions through a single channel protein. That was a Saturday afternoon. “By Monday, we were all doing it,” says Owen Hamill of the University of Texas Medical Branch in Galveston, who was a postdoc in Sakmann’s lab at the time.

Sigworth remembers it well. “I came into lab that Monday morning and Erwin said, with a twinkle in his eye, ‘I think I know how you’re going to see sodium channels,’” he says. These channels—essential to neural communication—had proven elusive because they produce such small currents and remain open for such a short time. But thanks to the team’s new “patch-clamp” technique—and in particular, the formation of an incredibly tight seal, or “gigaseal,” between the pipette tip and the cell membrane—“seeing sodium channels suddenly became really easy,” says Sigworth, who, along with Neher, published these observations (and the first description of the tight-seal patch-clamp technique) in Nature in 1980.

“Nobody had ever seen a single channel in a biological membrane before,” notes former postdoc Henrique von Gersdorff of the Vollum Institute at Oregon Health and Science University. “Erwin and Bert were the first to observe an ion channel as it opened and closed in real time in a living cell.”

And that was just the beginning. “Electrophysiology was totally transformed by the patch-clamp technique,” says Chuck Stevens of the Salk Institute. “You could now study all kinds of channels you couldn’t study before. Everything that we’ve learned about the nervous system in the last 25 years we could not have done without patch-clamping. Erwin’s discovery of the gigaseal made all the difference in the world.”

And though Neher will forever be associated with ion channels and their observation—especially after that work earned him and Sakmann the 1991 Nobel Prize in Physiology or Medicine—he has since broadened his scope to include measurements that reveal the detailed mechanisms of neurotransmitter release and other molecular interactions that support neural communication.

EUREKA

Understanding the workings of the brain has long been on Neher’s mind. “The nerves and bioelectricity were my favorite subjects from the beginning,” he says. “It seemed the ideal combination of physics and biology, and learning about nerve signaling in the brain is an exciting problem.”

After completing his undergraduate degree in physics at the Technical University of Munich, Neher landed a Fulbright Scholarship that brought him to the University of Wisconsin, where he got his first taste of biophysics. When he returned to Germany a year later, Neher was itching to use biophysics to study the electrical impulses that transmit signals in the nervous system. “The problem,” he says: “As a physicist, I had to find a professor who would be interdisciplinary enough to accept a project recording currents in snail neurons as a physics PhD project.”

Dieter Lux fit the bill. A creative scientist with a strong interest in electrophysiology, Lux encouraged Neher to place a pipette over a small patch of membrane on a snail neuron so that he could measure the currents flowing in that region. “That was the precursor for the patch-clamp technique,” says von Gersdorff.

Neher ended up characterizing the properties of a current that’s key to some cells’ ability to act as a pacemaker. “But the issue of molecular mechanisms was always on our mind,” he says. As doctoral students at the Max Planck Institute in Munich, Neher and Sakmann both contemplated whether cells’ electrical currents were generated by channels that open to allow ions to stream across the membrane, or by transporter proteins that grab ions on one side of the membrane and personally escort them to the other side. When they met again in Gottingen during their postdoctoral years, the duo decided that to answer these questions, they needed to focus on just the small spot of membrane through which the ions passed. Sakmann, the biologist, concentrated on getting the cleanest possible cell preparation: muscle cells stripped of nerves and connective tissue—or grown in cell culture. And Neher strove to dampen the noise and boost the signal by getting “as good a seal between the pipette and the membrane as possible,” he says.

“Everything that we’ve learned about the nervous system in the last 25 years we could not have done without patch-clamping. Erwin’s discovery of the gigaseal made all the difference in the world.” —Chuck Stevens

In the mid-70s, the two honed their technique to the point where they could see traces of channel activity: those telltale waves riding atop a sea of noise. And during a stint as a research associate in the Stevens lab (then at Yale), Neher recorded signals from acetylcholine-activated channels that he found convincing—as did the reviewers of a paper he and Sakmann published in Nature in 1976. But he still wanted something cleaner. The big breakthrough came in 1980, when Neher realized that the intimate union of instrument and membrane required a pristine pipette. Used pipettes, even those that are carefully cleaned, inevitably collect membrane fragments and other materials that prevent the formation of a tight seal. “Erwin had figured out how to mass produce pipettes,” says Sigworth. “Before that, they were so hard to make, you would keep a pipette and use it for weeks. But it turns out that the only way you can get a gigaseal is if you use a brand-new pipette.”

You also needed to suck. “You had to apply a little bit of suction in order to pull some membrane into the orifice of the pipette,” says Neher. “If you did it the right way, it worked.” At least for Neher. “There was a weird period where we could no longer get gigaseals,” recalls Hamill. “Then Bert suggested you have to blow before you suck.” Gently blowing a solution through the pipette as it approaches the surface of the cell keeps the tip from picking up debris during the descent. Between the blowing and the sucking, Hamill says, “our efficiency went up to 99 percent.”

“And patch-clamping has not gotten much better since its invention,” says Christian Rosenmund of the Charité University of Medicine in Berlin. Labs around the world quickly adopted the technique, and “it has been state-of-the-art for the past 20 years.” Peter Jonas of the University of Freiburg agrees. “It’s quite remarkable that many of the procedures reported in the original paper are still followed quite precisely,” he says. “So it really was the final word on the technique at the time.”

GUIDING LIGHT

After chasing ion channels, Neher adapted the technique to study neurotransmitter secretion. When vesicles containing hormones or neurotransmitters fuse with the cell membrane to release their cargo, they change the membrane’s surface area—which alters the electrical properties of the membrane, and thus can also be monitored by patch-clamping. “This was a big breakthrough,” says Sigworth, “because now you had a way to look at events underlying neurotransmitter release and the whole secretory process, which were totally mysterious at the time.”

Neher now focuses his attention on secretion of hormones and neurotransmitters—and on the molecular events that drive membrane fusion. “Even after his Nobel Prize, he managed to do experiments himself,” says von Gersdorff. Because at heart, Neher is a consummate experimentalist. “More than anything, he loves sitting down at the experimental setup and solving all those problems to get the cell or whatever he’s working on to give him an answer to his question,” says Sigworth.

And his physics background doesn’t hurt. “He thinks in terms of making measurements,” says Stevens. “His style is to say, ‘what measurement do I need to make to learn something new—something we can’t learn now.’” To top it off, von Gersdorff adds, “he’s fearless when it comes to developing or refining new technologies.”

And though he’s not necessarily at the bench every day, he’s still working hard. “There’s no coasting with Erwin Neher. Erwin does not coast,” says Sam Young of the new Max Planck Florida Institute, another former postdoc. “He has questions he wants answered—and the questions he’s asking now are just as difficult to answer as the ones he asked when he was starting out.” Jonas agrees. “He really publishes outstanding work at a continuous pace,” he says. “And if you look at his most recent papers, they’re just as interesting as his early work. He’s always moving in new directions.”

Most recently, Neher has set his sights on boosting fluorescence image analysis. “Each photon you detect is worth something,” he says. “And you have to make good use of it.” Although he hasn’t yet decided what he’ll do when he retires in 2011, Neher says he “will not stop. That’s quite clear.”

And his work will continue through the young scientists he’s trained. “You get the sense that he feels his success is built not only on what he’s done, but on what the people who come through his lab will ultimately accomplish,” says Young. Rosenmund agrees: “When he watches his students or young colleagues giving a presentation, he looks just like a proud father.”

“Erwin is a model of what every scientist should aspire to be,” adds Young. “You’re not going to meet too many people like Erwin Neher in this world.”