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Synchronous phosphorylation of CPI‐17 and MYPT1 is essential for inducing Ca 2+ sensitization in intestinal smooth muscle
Author(s) -
Mori D.,
Hori M.,
Murata T.,
Ohama T.,
Kishi H.,
Kobayashi S.,
Ozaki H.
Publication year - 2011
Publication title -
neurogastroenterology and motility
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.489
H-Index - 105
eISSN - 1365-2982
pISSN - 1350-1925
DOI - 10.1111/j.1365-2982.2011.01799.x
Subject(s) - phosphorylation , carbachol , contraction (grammar) , myosin light chain phosphatase , biology , muscle contraction , rho kinase inhibitor , protein kinase c , rho associated protein kinase , stimulation , sensitization , microbiology and biotechnology , medicine , endocrinology , chemistry , neuroscience
Background Myosin phosphatase activity is regulated by mechanisms involving the phosphorylation of CPI‐17 and MYPT1, primarily based on studies with tonic‐type vascular smooth muscles. This study examined how these mechanisms contribute to the regulation of contraction of a phasic‐type intestinal smooth muscle. Methods Phosphorylation levels, tension, and Ca 2+ sensitization was detected in rat ileal smooth muscle. Key Results In rat ileal smooth muscle, phosphorylation level of CPI‐17 at Thr 38 and MYPT1 at Thr 853 , but not MYPT1 at Thr 696 , were increased with carbachol (1 μ mol L −1 ) accompanied with muscle contraction. The PKC inhibitor Go6976 (1 μ mol L −1 ) inhibited the carbachol‐induced phosphorylation of CPI‐17, whereas the Rho‐associated kinase (ROCK) inhibitor, Y‐27632 (10 μ mol L −1 ) inhibited the carbachol‐induced phosphorylation of both CPI‐17 and MYPT1. Application of Go6976 or Y‐27632 alone inhibited the carbachol‐induced contraction; however, the combined application of these inhibitors did not inhibit the contraction in an additive manner. In β‐escin‐permeabilized ileal strip, treatment with antiphosphorylated antibodies for CPI‐17 at Thr 38 and MYPT1 at Thr 853 and Thr 696 alone almost completely abolished the Ca 2+ sensitization due to carbachol with GTP. Conclusions & Inferences In conclusion, receptor stimulation increases the Ca 2+ sensitivity of contractile elements through CPI‐17 phosphorylation via the PKC/ROCK pathways and MYPT1 phosphorylation via the ROCK pathway, when these mechanisms operate cooperatively and/or synchronously in intestinal smooth muscle.