G-PROTEIN MODULATION OF ALPHA(1A) (P/Q) TYPE CALCIUM-CHANNEL EXPRESSED IN GH(3) CELLS

GH(3) cell lines stably expressing alpha(1A) channel were established and the modulation of this channel by G-protein through membrane-delimited pathways were studied. Wild type GH(3) cells were found to express omega-conotoxin MWC (MVIIC) sensitive Ca2+ current but this component was different from the alpha(1A) channel because of its susceptibility to G-protein modulation, suggesting MWC also blocks channels other than P/Q type. alpha(1A) channel expressed in GH(3) cells showed slowing of activation and reduction of current amplitude by the application of carbachol. Both of these effects were pertussis toxin (PTX) sensitive and voltage dependent. alpha(1A) channels were also found to be modulated through a PTX insensitive pathway, the modulations observed were similar to those in the PTX sensitive pathway. The results further suggest that these two effects are governed by a different mechanism in both PTX sensitive and insensitive pathways. (C) 1995 Academic Press, Inc.