CaSR與PMCA1a在斑馬魚側線毛細胞上扮演之功能

Abstract

哺乳動物的內耳毛細胞扮演偵測聲音的功能，當音波的震動傳入內耳，會使纖毛束彎曲並進而開啟機械性通道產生聽覺。毛細胞的機械性通道位於纖毛的頂端是一種對鈣離子具有高通透性的陽離子通道。近年來，斑馬魚的側線系統被廣泛研究，且側線毛細胞被做為活體研究的新指標。本篇研究利用掃描式離子選擇電極技術(SIET)，以活體的狀況下測量斑馬魚仔魚側線毛細胞機械性通道的功能，進一步觀察PMCA與CaSR在毛細胞的表現以及對機械性通道功能的影響。在本篇實驗中證實PMCA1a與CaSR的蛋白質表現在受精後第96小時斑馬魚仔魚毛細胞靜纖毛的位置。以Morpholino knock down、PMCA抑制劑 (o-vanadate, Eosin-Y)、CaSR促進劑(R568)處理，發現機械性通道的鈣離子流受到抑制，表明了PMCA1a與CaSR對於機械性通道功能的重要性。此外，給予仔魚短期高鈣的環境也會抑制機械性通道鈣離子的流入，顯示環境鈣離子變化時機械性通道的功能會受到調節，而調節機械性通道的功能可能與PMCA1a以及CaSR參與有關。The sensory hair cells in mammalian inner ear are responsible for sound transduction. Sound waves deflect hair bundles and open the mechanotransducer (MET) channels, which initiate mechanotransduction. The MET channels expressed in stereocilia are cation channels with high Ca2+ permeability. Zebrafish lateral line is recently reported to be a useful in vivo model for studying hair cells. We have demonstrated the scanning ion-electrode technique (SIET) to be a sensitive approach for functionally assaying MET channel in zebrafish. In this study, expression and function of plasma membrane Ca2+ ATPase (PMCA) and calcium-sensing receptor (CaSR) were investigated. The protein expressions of PMCA1a and CaSR were showed in stereocilia of lateral line hair cell of 96 hpf zebrafish larvae. The MET channel mediated Ca2+ influx detected by SIET was suppressed by treatment of PMCA inhibitor (o-vanadate, Eosin Y) and CaSR activator (R568). These results indicated that PMCA1a and CaSR was critical for maintaining the function of MET channel. Furthermore, function of MET channel was decreased in larvae incubated in high Ca2+ water. These results revealed that function of MET channel is altered in different environmental Ca2+ levels. This functional regulation of MET channel may be required the participation of PMCA1a and CaSR.