LAUSR

In C. elegans, the behavioral response to touch and the underlying molecular actors are thoroughly studied. However, it is still debated which and how many of several co-expressed pore-forming subunits assemble into a functional, multimeric mechano-electrical transduction (MeT) channel in vivo. Two members of the DEG/ENaC channel family, MEC-4 and MEC-10, are important to convert touch into behavioral responses. MEC-4 is required to form native MeT channels, whereas MEC-10 plays a regulatory role. Recently, a third homologous protein and potential subunit, DEGT-1, was identified; its role in touch sensation remains incompletely understood. Given that DEG/ENaC proteins are thought to assemble as trimers, the presence of a third, homologous protein opens new questions regarding the composition of native MeT channels. A key outstanding question is which of these homologous proteins co-assemble to form the channels responsible for touch sensation. With the gentle touch assay, we detected a more severe defect in touch sensation if both MEC-10 and DEGT-1 were removed simultaneously than we did by removing them individually. This genetic enhancement suggests that DEGT-1 is part of the native MeT channel complex. To investigate this further, we are analyzing the contribution of DEGT-1 to native MeT channels and to channel activity in Xenopus oocytes. Using in vivo patch clamp recordings of wild type and mutant touch receptor neurons lacking individual subunits or expressing proteins with altered pore domains, we seek to delineate how DEGT-1 contributes to the mechanosensitivity, voltage-dependence and adaptation of the native MeT current. In Xenopus oocytes, we find that DEGT-1 is unable to form homomeric channels on its own, but can assemble into functional channels in the presence of MEC-4. This finding suggests that, like MEC-10, DEGT-1 plays a regulatory role in channel formation.