Drug discovery takes a long time. Most readers of the SLAS Electronic Laboratory Neighborhood would agree with the statement above. No surprises there. But, those working in the ion channel field might also add – we're moving faster than we did just a few years back.
Ion channel biologists feel that advanced technology is propelling them into more effective investigation – and they look forward to helping move things more quickly through the drug discovery pipeline.
Claire Townsend, manager of the Cellular Targets and Electrophysiology Group at GlaxoSmithKline, Research Triangle Park, NC, and speaker for the SLAS Ion Channel Assays three-part virtual course (Sept. 8, 15, 22), is one such scientist.
"Ion channel biology requires unique tools, products and instruments," she says. "It is such an important area of discovery, as ion channels regulate the excitability of cells throughout the body, not just in the nervous system."
A 1997 article in the New England Journal of Medicine by Michael J. Ackerman, M.D., Ph.D., and David E. Clapham, M.D., Ph.D. begins:
"Ion channels constitute a class of proteins that is ultimately responsible for generating and orchestrating the electrical signals passing through the thinking brain, the beating heart, and the contracting muscle. Using the methods of molecular biology and patch-clamp electrophysiology, investigators have recently cloned, expressed, and characterized the genes encoding many of these proteins. Ion-channel proteins are under intense scrutiny in an effort to determine their roles in pathophysiology and as potential targets for drugs."
Understanding the basics of ion channel biophysics is critical for those wishing to design ion channel assays, Townsend says. Among the questions asked in ion channel biophysics is why do these proteins transport different ions?
Peter Miu, Ph.D., senior scientist in Lead Discovery at Amgen, Inc., Thousand Oaks, CA, and also a speaker for the SLAS Ion Channel Assays virtual course, adds that one must first understand the basic role of ion channels in normal physiology to understand how and why different ion channels go wrong in disease states.
"Throughout my career, I've come to appreciate that ion channels participate in many therapeutic areas," Miu states. "Their involvement goes beyond neurological disorders."
"The field truly exploded in the late 1980s and early 1990s with gene cloning and the increased development of assays for drug development," Townsend adds. "Expression and screening technologies blossomed in the late 1990s; a new fluorescence reader, FLIPR (fluorescent imaging plate reader), allowed screening for ion channels on a large scale."
But, Townsend indicates, the field really took off in 2002 when the first automated electrophysiology technology platform hit the market. That's when not only the quantity of experiments could increase but the quality of the data being produced improved dramatically.
Miu concurs and provides additional background. "Historically, ion channels have been a very difficult topic to study. Back in the early days, we didn't know a lot about different families of ion channels for example. In the ‘60s and ‘70s we used pharmacological agents to characterize the function of different ion channels in normal physiological processes such as pain perception or muscle contraction. The discovery of patch clamp technology and molecular biology in the late ‘80s provided a better understanding of different families of ion channels and their function in normal physiology and pathophysiology."
Development of patch clamp technology also led to a Nobel Prize in Physiology or Medicine for its creators Bert Sakmann and Erwin Neher in 1991.
Better technology led to more efficient assays and increased discoveries, but biologists working in the field wanted – and needed – more.
"In the early 1990s, the discovery of specific mutations of proteins led to a better understanding of ion channel function," Miu explains. "Later, we learned how mutated channels can cause diseases."
According to MedicineNet.com, an ion channel "is a protein that acts as a pore in a cell membrane and permits the selective passage of ions (such as potassium ions, sodium ions, and calcium ions), by means of which electrical current passes in and out of the cell. Ion channels also serve many other critically important functions including chemical signaling, transcellular transport, regulation of pH, and regulation of cell volume. Malfunction of ion channels can cause diseases in many tissues. The array of human diseases associated with defects in ion channels is growing. These diseases are called channelopathies."
"Now, we seek potential therapeutic agents that can correct the mistakes of an ion channel," Miu summarizes.
As with all medical research, scientists are trying to close the gap between discoveries at the bench and resulting therapies for the patient. "Conducting in vitro experiments are, of course, more simplistic than in vivo experiments," Miu expounds. "However, in vitro experiments do not actually mimic the disease process. Furthermore, it is always a challenge to come up with a valid in vivo animal model to mirror a human disorder. Therefore there is a big jump from the bench to treating patients."
Reading the literature gives one hope that we are closing the gap daily. For example, the work of Igor Efimov, Ph.D., a biomedical engineer at Washington University in St. Louis, captures the differences between the distribution of potassium-ion-channel variants in the mouse heart and in the human heart in research published in the Journal of Molecular and Cellular Cardiology.
Miu points to electrophysiology as the technique that helps them fully study how ion channels behave both in normal state and when applying pharmacological agents to modify their function in a disease state. He says in the last five to seven years, there have been advances in the technology where they can perform the same types of electrophysiology experiments as before but with greater efficiency.
"For example, using traditional patch clamp technology, it would take one full day, if not two, to determine the potency of one compound with a reasonable sample size for statistical analysis," he shares.
Scientists using first generation automated patch clamp platforms, which study ion channel activities in the same manor as traditional patch clamp, were able to study 16 cells simultaneously. The next generation of patch clamp instruments tripled that capacity and today we're seeing patch clamp instruments that study 384 cells simultaneously, Miu adds.
Townsend leads a team at GlaxoSmithKline that is developing reagents and assay techniques for ion channels. They are making great strides, but there is much more ahead in this relatively young field.
"There is a very diverse family of ion channels, and some are more tractable than others," she instructs. "Those expressed at the cell surface, of course, are more accessible than those located in intracellular organelles."
How is the scientific research community responding to the need for improved tools? Several LabAutomation2011 and SBS 2011 exhibitors displayed ion channel products and more are expected at SLAS2012, February 4-8, in San Diego. One partner, TEFLabs, was an SBS 2011 New Product Awards designee for its Asante NaTRIUM Green and Asante Potassium Green Ion Channel Dyes.
According to the TEFLabs website, "Asante NaTRIUM Green 1 is a visible wavelength fluorescent indicator with a useful dynamic range for measuring cytosolic Na+ concentrations. The importance of the potassium ion (K+) is coupled to the sodium ion (Na+), because the cell expends a major part of its metabolic energy maintaining the concentrations of Na+ and K+ within the cell. Asante Potassium Green helps with these techniques."
Ronald J. Knox, Ph.D., Bristol-Myers Squibb Research, shows progress in tools and techniques for ion channel drug discovery during module two of the SLAS virtual course – Impact of Technology Evolution on Ion Channel Drug Discovery.
"Two examples that figure prominently in both modern cardiovascular medicine, and in the development of technology strategies for prosecuting ion channel targets broadly, are the quinidine class of Na+-channel blockers, and the dihydropyridine class of Ca++-channel blockers," Knox explains.
Recognizing the growth in this field and the need for more information, SLAS offers the Ion Channel Assays virtual course – a three-module series to be held on three Thursdays in September.
September 8, 2011 — Module One
Claire Townsend, Ph.D., GlaxoSmithKline
September 15, 2011 — Module Two
Ronald J. Knox Ph.D., Bristol-Myers Squibb Research
September 22, 2011 — Module Three
Peter Miu, Ph.D., Amgen
"SLAS virtual courses are designed to provide meaningful scientific material from topic experts; most companies could not present such an extensive course on their own," states Steve Hamilton, Ph.D., SLAS director of education. "Registrants who choose to participate in the live, online course modules can interact in real time with the speaker and other attendees. Or, they may choose to purchase the recordings for later use."
Register today to take advantage of discounts for members, academics and those registering for all three modules at once. This SLAS virtual course is presented as a live, real-time event as well as a streaming online video recording or on CD.
"I hope that with this SLAS virtual course, we can provide a good foundation for scientists new to ion channels," Townsend summarizes. "Personally, I hope that I can help bring safer drugs to patients more quickly by the work we are doing here at GSK. As technologies evolve and tools become even better, we have a lot more control on how we study these channels and test compounds."
Townsend, Knox and Miu encourage you to join with them in the SLAS virtual course and explore this fascinating area of research.
August 24, 2011