Elucidation of the importance of different structural domains of the Na+-Ca2+ exchanger (NCX) in its functional expression. About 15 years ago our laboratory has cloned three isoforms of the rat NCX1 gene (1,2). By introducing defined changes in NCX protein structure using site directed mutagenesis, we are examining the impact of these changes on NCX function and protein expression. This approach led to elucidation of the role of different NCX domains (N-terminus, C-terminus and the large cytoplasmic loop) in maturation, trafficking to the cell surface and acquisition of function competence (3, 5,6). The role of disulfide bridges (6) and importance of individual cysteine residues is studies by SCAM and modification with membrane permeable and non permeable covalent probes.
NCX expression, CsA and [Ca2+] regulation: Exposure of cells expressing NCX to Cyclosporin A (CsA)- an immunosupressive agent given to patients after organ transplantation, led to down regulation of NCX1, NCX2 and NCX3 surface expression (7,8) in a post translational manner. Cyclophilins, the family of cellular receptors for CsA play a role in protein folding (chaperon action) and acquisition of function competent conformation via peptide X-Pro bond cis-trans isomerization. The ongoing research involves: elucidation of the mode of action of CsA on NCX expression, identification of the structurally important proline residues of the protein for determination of its conformation, studying the effect of CsA on the expression pattern NCX in cell lines expressing the protein endogenously (heart, smooth and skeletal muscle, nerve and glia) and examining the connection between CsA treatment, NCX surface expression and intracellular [Ca2+] regulati