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Calponin and the Smooth Muscle Thin Filament
Sponsored by APS Muscle Biology Group
Cell Physiology Track

Calponin was first found in smooth muscle over 20 years ago as a potential thin filament regulatory protein analogous to striated muscle troponin. After two decades of extensive research, calponin is now known as a family of homologous actin filament-associated proteins of 292-330 amino acids expressed in both smooth muscle and non-muscle cells. Through high affinity binding to F-actin, calponin inhibits the actin-activated MgATPase of smooth muscle myosin and modulates contractility. A hypothesis is that calponin may represent a thin filament regulatory system in smooth muscle, like troponin in striated muscles. Calponin is also found in non-muscle cells. Emerging evidence indicates that calponin may play a role in regulating the actin cytoskeleton during cell migration and proliferation. Despite calponin’s broad distribution and abundance in cells, its physiological function remains to be established.

The goal of the proposed symposium is to review the history of calponin studies, discuss the recent progresses in calponin studies, and catalyze new ideas for future investigation. The speakers are chosen to cover a wide spectrum of the filed. Thomas Nosek will give a brief introduction to the session. The lectures will start with an overview of the smooth muscle thin filament by Robert Moreland. Katsuhito Takahashi will present the history and current status of smooth muscle calponin studies. Edward Egelman will present a lecture on calponin’s localization and interactions in the actin filament. J.-P. Jin will then conclude the session with a presentation on the mechanical force regulation and function of calponin.