| First Author | Hypolite JA | Year | 2009 |
| Journal | Am J Physiol Renal Physiol | Volume | 296 |
| Issue | 3 | Pages | F658-65 |
| PubMed ID | 19052105 | Mgi Jnum | J:145542 |
| Mgi Id | MGI:3835214 | Doi | 10.1152/ajprenal.90221.2008 |
| Citation | Hypolite JA, et al. (2009) Deletion of SM-B, the high ATPase isoform of myosin, upregulates the PKC-mediated signal transduction pathway in murine urinary bladder smooth muscle. Am J Physiol Renal Physiol 296(3):F658-65 |
| abstractText | Detrusor smooth muscle (DSM) hypertrophy induced by partial bladder outlet obstruction (PBOO) is associated with changes in the NH(2)-terminal myosin heavy chain isoform from predominantly SM-B to SM-A, alteration in the Ca(2+) sensitization pathway, and the contractile characteristics from phasic to tonic in rabbits. We utilized the SM-B knockout (KO) mouse to determine whether a shift from SM-B to SM-A without PBOO is associated with changes in the signal transduction pathway mediated via PKC and CPI-17, which keeps the myosin phosphorylation (MLC(20)) level high by inhibiting the myosin phosphatase. DSM strips from SM-B KO mice generated more force in response to electrical field stimulation, KCl, carbachol, and phorbol 12,13-dibutyrate than that of age-matched wild-type mice. There was no difference in the ED(50) for carbachol but the maximum response was greater for the SM-B KO mice. DSM from SM-B KO mice revealed increased mass and hypertrophy. The KO mice also showed an overexpression of PKC-alpha, increased levels of phospho-CPI-17, and an elevated level of IP(3) and DAG upon stimulation with carbachol. Two-dimensional gel electrophoresis revealed an increased level of MLC(20) phosphorylation in response to carbachol. Together, these changes may be responsible for the higher level of force generation and maintenance by the DSM from the SM-B KO bladders. In conclusion, our data show that ablation of SM-B is associated with alteration of PKC-mediated signal transduction and CPI-17-mediated Ca(2+) sensitization pathway that regulate smooth muscle contraction. Interestingly, similar changes are also present in PBOO-induced DSM compensatory response in the rabbit model in which SM-B is downregulated. |
