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| CHANNELING
Philip Jensik, who earned his master’s degree in physiology last year, has received the SIU Alumni Association’s Outstanding Thesis award for 2002. His work focused on proteins in cell membranes that act as channels regulating the flow of important chemicals in the body. Understanding how such proteins work has a bearing on heart disease, kidney disease, and other disorders. To function properly in changing circumstances (for instance, exertion or injury), the body must control the movement of ions, such as potassium, sodium, and calcium ions, into and out of its cells. Without the right controls, body systems can get dangerously out of balance, causing irregular heart rhythm or other problems. What governs the flow of ions? Various chemicals cause receptor proteins in the cell membrane— channels—to open. This creates a route for ions to enter the cell. Physiology professor Thomas Cox, Jensik’s mentor, studies a kind of channel important in controlling the flow of potassium and sodium ions in the heart, kidney tubules, and blood vessels. Such channels, found in vertebrates as diverse as fish and humans, are regulated by a basic cell chemical called ATP. For his master’s research, Jensik discovered and studied an unusual, closely related kind of channel in the skin of frog tadpoles that's thought to play a role in sensory processes. Jensik cloned the DNA that directs cells to make the channel protein. From the DNA sequence, he determined the protein’s amino acid composition. By studying the behavior of the channel in the cell membrane, he discovered (among other things) that repeated exposure to ATP causes enzymes to break down the protein, eventually destroying the channel. Jensik’s findings about the structure and properties of this channel, which have been published in the American Journal of Physiology, are already helping other scientists to better understand how these crucial body regulators function and to compare them across species. —Marilyn Davis
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