Karnam S Murthy

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Phosphorylation of Ser19 on the 20-kDa regulatory light chain of myosin II (MLC20) by Ca2+/calmodulin-dependent myosin light-chain kinase (MLCK) is essential for initiation of smooth muscle contraction. The initial [Ca2+]i transient is rapidly dissipated and MLCK inactivated, whereas MLC20 and muscle contraction are well maintained. Sustained contraction(More)
Single-transmembrane natriuretic peptide clearance receptor (NPR-C), which is devoid of a cytoplasmic guanylyl cyclase domain, interacts with pertussis toxin (PTx)-sensitive G proteins to activate endothelial nitric oxide synthase (eNOS) expressed in gastrointestinal smooth muscle cells. We examined the ability of NPR-C to activate other effector enzymes in(More)
Signalling via m3 and m2 receptors in smooth muscles involved activation of two G-protein-dependent pathways by each receptor. m2 receptors were coupled via Gbetagammai3 with activation of phospholipase C-beta3, phosphoinositide 3-kinase and Cdc42/Rac1 (where Cdc stands for cell division cycle) and p21-activated kinase 1 (PAK1), resulting in phosphorylation(More)
We have shown recently that the 37-amino acid intracellular domain of the single-transmembrane, natriuretic peptide clearance receptor, NPR-C, which is devoid of kinase and guanylyl cyclase activities, activates selectively Gi1 and Gi2 in gastric and tenia coli smooth muscle. In this study, we have used synthetic peptide fragments of the N-terminal,(More)
P2 receptor subtypes and their signaling mechanisms were characterized in dispersed smooth muscle cells. UTP and ATP stimulated inositol 1,4,5-triphosphate formation, Ca2+ release, and contraction that were abolished by U-73122 and guanosine 5'-O-(3-thio)diphosphate, and partly inhibited (50-60%) by pertussis toxin (PTX). ATP analogs (adenosine 5'-(alpha,(More)
In COS-7 cells, all five cloned somatostatin receptors are coupled via inhibitory G proteins to activation of an unidentified phospholipase C-beta (PLC-beta) isozyme and inhibition of adenylyl cyclase. In the present study, intestinal smooth muscle cells (SMC) that express only one receptor type, sstr3, and possess a full complement of G proteins and(More)
Bile acids act as signaling molecules and stimulate the G protein coupled receptor, TGR5, in addition to nuclear farnesoid X receptor to regulate lipid, glucose and energy metabolism. Bile acid induced activation of TGR5 in the enteroendocrine cells promotes glucagon like peptide-1 (GLP-1) release, which has insulinotropic effect in the pancreatic β cells.(More)
In gastrointestinal smooth muscle, the neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) induce relaxation by interacting with VIP2/PACAP3 receptors coupled via Gs to adenylyl cyclase and with distinct receptors coupled via Gi1 and/or Gi2 to a smooth muscle endothelial nitric oxide synthase(More)
The role of RhoA in myosin light-chain (MLC)(20) dephosphorylation and smooth muscle relaxation by PKA and PKG was examined in freshly dispersed and cultured smooth muscle cells expressing wild-type RhoA, constitutively active Rho(V14), and phosphorylation site-deficient Rho(A188). Activators of PKA (5,6-dichloro-1-beta-ribofuranosyl benzimidazole(More)
The regulation of cGMP-specific phosphodiesterase (PDE) 5 and soluble guanylate cyclase (GC) by cGMP- and cAMP-dependent protein kinases (PKG and PKA respectively) was examined in gastric smooth muscle. The NO donor, sodium nitroprusside (SNP), stimulated PDE5 phosphorylation and activity, which was blocked by the selective PKG inhibitor, KT5823, resulting(More)