PLASMA-MEMBRANE CA2-BRAIN - PATTERNS OF ALTERNATIVE SPLICES SEEN BY ISOFORM-SPECIFIC ANTIBODIES( PUMP IN RAT)

The expression at the protein level of plasma membrane calcium pump (P MCA) isoforms in rat brain was detected by new antibodies that disting uished the four gene products and their alternatively spliced variants . All four gene products were distributed throughout hippocampus, cort ex, and cerebellum, but the alternate splices showed more distinct dis tribution patterns. The b splice of isoform 1 was not detectable in an y of the brain regions, which makes it unlikely that this isoform perf orms an essential housekeeping role as is frequently proposed. The b s plices of isoforms 3 and 4, although expressed in all three regions, s howed evidence of proteolysis, which removed a portion of the carboxyl terminus, In contrast, isoform 2b retained its full length, indicatin g that PMCA2b is more resistant to proteolysis than the other b forms, Whereas substantial amounts of isoforms 1a, 2a, and 3a were expressed in all regions, 4a was found only in frontal cortex. The distinct pat terns of expression of the PMCA isoforms in brain suggest that some of them play a special role in intracellular Ca regulation.