FIGURE 11. Signaling pathways for generating the three types of contractions in colonic circular smooth muscle cells.

FIGURE 11

Signaling pathways for generating the three types of contractions in colonic circular smooth muscle cells. The electromechanical coupling initiated by slow-wave depolarization induces an influx of Ca2+ through voltage-gated calcium channels (L-type or Cav1.2b channels). The binding of ACh to muscarinic M3 receptors initiates multiple signaling pathways that induce further Ca2+ influx through receptor-gated Ca2+ channels; release intracellular Ca2+ from IP3-sensitive stores; inhibit MLCP; and increase the phosphorylation of MLC20 via PKC, ROK, and release of AA to enhance the amplitude and/or duration of contraction, resulting in the generation of three types of contractions. GEFs = guanine nucleotide exchange factors; CaM = calmodulin; MYPT1 and PP1c = regulatory and catalytic subunits, respectively, of MLCP (myosin light chain phosphatase); CPI-17 = PKC-potentiated inhibitor protein of 17 kDa; AA = arachidonic acid; PKC = protein kinase C; DAG = diacylglycerol; SR = sarcoplasmic reticulum; PIP2 = phosphatidyl inositon 4,5,-biphosphate; PLC = phospholipase C; IP3 = inositol 1,4,5-triphosphate; cPLA2 = cytosolic phospholipase A2; MLCK = myosin light chain kinase; RhoGDI = GDP dissociation inhibitor; ROK = Rho kinase; ACh = acetylcholine.

From: Regulatory Mechanisms

Cover of Colonic Motility
Colonic Motility: From Bench Side to Bedside.
Sarna SK.
San Rafael (CA): Morgan & Claypool Life Sciences; 2010.
Copyright © 2010 by Morgan & Claypool Life Sciences.

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