Cytosolic domain regulates the calcium sensitivity and surface expression of BEST1 channels in the HEK293 cells

BEST family is a class of Ca2+-activated Cl-channels evolution-ary well conserved from bacteria to human. The human BEST paralogs (BEST1-BEST4) share significant amino acid sequence homology in the N-terminal region, which forms the trans -membrane helicases and contains the direct calcium-binding site, Ca2+-clasp. But the cytosolic C-terminal region is less conserved in the paralogs. Interestingly, this domain-specific sequence conservation is also found in the BEST1 orthologs. However, the functional role of the C-terminal region in the BEST channels is still poorly understood. Thus, we aimed to understand the functional role of the C-terminal region in the human and mouse BEST1 channels by using electrophysio-logical recordings. We found that the calcium-dependent acti-vation of BEST1 channels can be modulated by the C-terminal region. The C-terminal deletion hBEST1 reduced the Ca2+- dependent current activation and the hBEST1-mBEST1 chimera showed a significantly reduced calcium sensitivity to hBEST1 in the HEK293 cells. And the C-terminal domain could regu-late cellular expression and plasma membrane targeting of BEST1 channels. Our results can provide a basis for under-standing the C-terminal roles in the structure-function of BEST family proteins. [BMB Reports 2023; 56(3): 172-177]