Hearing is a sensory percept that is triggered by mechanical stimuli. Mechanosensitive channels, a type of ion channel that converts mechanical force into an electrical impulse, are central to hearing in both vertebrates and invertebrates. However, the identity of mechanosensitive channels responsible for hearing remains a mystery. While a wealth of circumstantial evidence implicates transient receptor potential (TRP) channel proteins in mammalian hearing, other studies argue against this model. The controversy mainly arises from the fact that most studies were carried out in heterologous systems;yet the proper function of mechanosensitive channels require the channel to be anchored to the extracellular matrix and intracellular cytoskeleton, a physiological setting that is difficult to recapitulate in heterologous expression systems. This suggests that it is necessary to investigate the function of these channels in an in vivo setting. Recently, our lab has developed an electrophysiological recording protocol to characterize mechanosensitive TRP channels in vivo. Using this approach, we have recently reported that the C. elegans TRPN protein TRP-4 is a pore-forming subunit of a native mechanosensitive channel, showing for the first time that TRP channels can function as mechanosensitive channels in vivo. This has also raised the possibility that other TRP channels may form mechanosensitive channels. While the TRPN channel family is conserved throughout invertebrates and lower vertebrates, they are not found in mammals, indicating that other mechanosensitive channels must underlie mechanotransduction in mammals. Notably, TRPV channels are well conserved from worms to humans. Our preliminary data indicate that C. elegans TRPV channels are required for mechanosensitive channel activity in a mechanosensory neuron in vivo, suggesting that TRPV channels may function as mechanosensitive channels. Here we propose that TRPV channels can function as mechanosensitive channels in vivo. To test this hypothesis, we will dissect the function and regulation of TRPV channels in mechanosensation in C. elegans using our newly developed in vivo electrophysiological recording protocol in conjunction with molecular genetic tools. As TRPV channels are well conserved from worms to humans, this work will provide novel insights into the molecular identity of the elusive mechanosensitive channels mediating hearing in humans.
Deafness and hearing deficits significantly reduce the quality of human life and caring for individuals with hearing disorders is a major economic and emotional burden for families. We know that our ears are mechanosensitive, detecting vibrations in the air as sound waves, but we have not identified the molecules responsible for detecting those sound waves. This application examines the role of a type of mechanosensitive protein, which will provide novel insights into the understanding of hearing loss and related human diseases.
|Wescott, Seth A; Ronan, Elizabeth A; Xu, X Z Shawn (2016) Insulin signaling genes modulate nicotine-induced behavioral responses in Caenorhabditis elegans. Behav Pharmacol 27:44-9|