MUTATIONAL ANALYSIS OF THE CYSTEINES IN THE EXTRACELLULAR DOMAIN OF THE HUMAN CA2- EFFECTS ON CELL-SURFACE EXPRESSION, DIMERIZATION AND SIGNAL-TRANSDUCTION( RECEPTOR )

Mammalian calcium receptors (CaRs) share with the metabotropic glutama te receptors (mGluRs) the relative positions of 16 cysteine residues i n the amino-terminal extracellular domain. To investigate the role of these cysteines, a series of mutants in the extracellular domain of th e human CaR was prepared in which each of these 16 cysteine residues a nd three others not conserved in the mGluRs were replaced by serines, Wild-type and mutant CaR cDNAs were expressed in HEK-293 cells, and ev aluated for expression and response to extracellular calcium, Mutation of three non-conserved cysteines and of two conserved cysteines produ ced proteins with near wild-type phenotype, In contrast, mutation of t he other conserved cysteines gave proteins that showed drastic reducti on in cell surface expression and/or failed to respond to calcium, We identified 14 cysteines essential for proper trafficking and function of the receptor, two of which may be involved in formation of a disulf ide-linked dimer, (C) 1998 Federation of European Biochemical Societie s.