Mechanical forces such as focused pressure or membrane stretch play central, but poorly understood, roles in biology. What types of molecules mediate mechanical signaling? Elegant electrophysiological studies have implicated a class of mechanically-gated ion channels in mechanotransduction. A recent breakthrough in this field is that analyses of C. elegans have identified members of a family of eukaryotic ion channels postulated to play central roles in mechanical signaling. In specialized touch sensory neurons, MEC-4 and MEC-10 channel subunits mediate touch transduction. A related subunit, UNC-8, modulates locomotion and is proposed to be involved in nematode proprioception (how an organism maintains a sense of where its different parts are and coordinates their motions). The identification of candidate mechanically-gated channels in C. elegans has now laid the groundwork for deciphering molecular mechanisms of mechanical signaling. Here the principal investigator proposes to combine genetic, molecular and biochemical approaches to deduce the molecular compositions and identify regulators of two mechanosensitive complexes. The specific goals are: 1) to test and extend models of channel/cytoskeleton interaction by defining protein interactions mediated by MEC-4 and MEC-10 intracellular domains; 2) to characterize the UNC-8 candidate proprioception channel by identification of subcellular localization, cellular site of action, and additional channel subunits; and 3) to clone and characterize 4 identified loci that genetically interact with unc-8 and to deduce the mechanisms by which they influence UNC-8 channel function. This work will test, refine and extend working models for molecular mechanisms of mechanotransduction, a significant issue because so little is understood of mechanical signaling and so many biological processes (ranging from cell volume regulation to the senses of touch, hearing and balance) depend upon it. In addition, the MEC-4/MEC-10 and UNC-8 channels are related to human ENaC channels that mediate Na+ readsorption and are essential for maintenance of electrolyte balance, blood pressure regulation, and clearing of fluid from neonatal lungs. Analyses of nematode and mammalian channels to date indicates that they work in fundamentally similar ways and thus data we generate in this work from a unique experimental perspective are expected to provide similar insight into general working of the channel class and hold implications for betterment of human health.
