Related Experiment Video
Updated: May 28, 2026

Applications of Spatio-temporal Mapping and Particle Analysis Techniques to Quantify Intracellular Ca2+ Signaling In Situ
Published on: January 7, 2019
Synchronous phosphorylation of CPI-17 and MYPT1 is essential for inducing Ca(2+) sensitization in intestinal smooth
1Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, the University of Tokyo, Tokyo, Japan.
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 (1μmolL(-1) ) accompanied with muscle contraction. The PKC inhibitor Go6976 (1μmol L(-1) ) inhibited the carbachol-induced phosphorylation of CPI-17, whereas the Rho-associated kinase (ROCK) inhibitor, Y-27632 (10μmol 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.
Related Concept Videos
Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
Smooth Muscle Contraction
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
IP3/DAG Signaling Pathway
Feedback Regulation of Calcium Concentration
Various transmembrane receptors, such as G protein-coupled receptors (GPCRs), elicit a response to extracellular signals by increasing cytosolic calcium. Activated GPCRs...
Phosphoinositides and PIPs
Different phosphoinositides are synthesized and recruited on the cytosolic face of the plasma membrane. The localization of specific phosphoinositides concentrated in separate membrane...
Excitation-Contraction Coupling in Skeletal Muscles
When an action potential...

