Identification of phospholipase C β isoforms and their location in cultured vascular smooth muscle cells of pig, human and rat

Four phospholipase C (PLC) beta isoforms have been described in pig aortic vascular smooth muscle. The aim was to determine if all four PLC beta isoforms are commonly expressed in vascular smooth muscle cells (VSMC) of three species, i.e. pig, human and rat, and if the individual isoforms had distinctive intracellular distributions. Vascular smooth muscle cell cultures were derived from explants of porcine and rat aorta and a human renal artery cell line. PLC beta isoform content was resolved using Western blotting. Intracellular location was determined by immunocytochemistry and confocal microscopy. All three species expressed PLCs, beta 1, beta 2, beta 3 and beta 4. In all species, PLC beta 1 demonstrated foci of concentration throughout the cytoplasm; PLC beta 2 demonstrated a punctate pattern that was principally at the cell periphery or was in the Golgi, depending upon the antibody used; PLC beta 3 was also cytoplasmic but showed a different pattern from PLC beta 1 and PLC beta 4 was cytoplasmic, except in pig quiescent cells, where it was associated with filamentous structures at the intersection with the plasma membrane. VSMCs of three different species express all four PLC beta isoforms. Each isoform has a unique and consistent signature of distribution that is generally common to all species.