Deletion of SM-B, the high ATPase isoform of myosin, upregulates the PKC-mediated signal transduction pathway in murine urinary bladder smooth muscle

摘要

Changes in the myosin isoforms in hypertrophy associated with various disease processes have been reported in cardiac (30, 37), skeletal (19, 45), and smooth muscle (15, 50). Partial bladder outlet obstruction (PBOO)-induced hypertrophy in both rabbits and mice causes a shift in the NH2-terminal MHC isoform from predominantly SM-B to SM-A (2, 15). Concomitant with a decrease in SM-B (the high ATPase isoform) and an increase in SM-A (low ATPase isoform), there is a decrease in maximum shortening velocity and the hypertro-phied detrusor smooth muscle (DSM) reveals contractile characteristics typical of tonic smooth muscle compared with the phasic contraction shown by normal DSM (46). In addition, PBOO-induced DSM hypertrophy also shows an upregulation of Rho-kinase (5) which is implicated in calcium sensitization of muscle contraction and an increase in the resting myosin light chain (MLC2o) phosphorylation level (8, 10, 44).