Role of Calcium-Sensing Receptor (CaSR) in Mechanotransduction of Hair Cell

Functional studies of inner ear hair cells of mammals, birds, and other vertebrates are limited by the difficulty in accessing the inner ear which is embedded in the temporal bone. Zebrafish lateral line was recently reported to be a useful in vivo model for studying hair cells and ototoxicity. We have demonstrated that the scanning ion-electrode technique (SIET) to be a sensitive approach for functionally assaying mechanotransducer channel (MET channel) in zebrafish. We also showed that ototoxin (neomycin and gentamicin) effectively block MET channel mediated Ca2+ influx within 10 min. In this project, we will extend our study to investigate role of Ca2+ sensing receptor (CaSR) in mechanism of mechanotransduction. This proposal will be designed as a three years project: The first year: Does MET channel sense extracellular Ca2+ level through CaSR? The prupose in the first year is to examine if function of MET channel is adjusted according to different extracellular Ca2+ levels, which is detected by CaSR. The expression level of CaSR in zebrafish embryo will also be examined. The second year: Does antibiotics (or high Ca2+) inhibit (or protect) function of MET channel through CaSR ? Previous studies showed that both Ca2+ and antibiotics (neomycin, gentamicin) are ligands of CaSR. The purpose in the second year is to examine if CaSR mediated the inhibition (or protection) of antibiotics (or high extracellular Ca2+). The third year: Does CaSR regulate function of MET channel (or PMCA) through secondary messenger? The purpose in the third year is to examine if CaSR regulate function of MET channel and PMCA (plasma membrane Ca2+ ATPase) through 2nd messenger.