Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.12 (PKG)
 2,515 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cyclic nucleotides acting through their associated protein kinases, the cGMP- and cAMP-dependent protein kinases, can relax smooth muscles without a change in free intracellular calcium concentration ([Ca2+]i), a phenomenon referred to as Ca2+ desensitization. The molecular mechanisms by which these kinases bring about Ca2+ desensitization are unknown and an understanding of this phenomenon may lead to better therapies for treating diseases involving defects in the contractile response of smooth muscles such as hypertension, bronchospasm, sexual dysfunction, gastrointestinal disorders and glaucoma. Utilizing a combination of real-time proteomics and smooth muscle physiology, we characterized a distinct subset of protein targets for cGMP-dependent protein kinase in smooth muscle. Among those phosphoproteins identified was calponin homology-associated smooth muscle (CHASM), a novel protein that contains a calponin homology domain and shares sequence similarity with the smoothelin family of smooth muscle specific proteins. Recombinant CHASM was found to evoke relaxation in a concentration dependent manner when added to permeabilized smooth muscle. A co-sedimentation assay with actin demonstrated that CHASM does not possess actin binding activity. Our findings indicate that CHASM is a novel member of the smoothelin protein family that elicits Ca2+ desensitization in smooth muscle.
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PMID:Modulation of smooth muscle contractility by CHASM, a novel member of the smoothelin family of proteins. 1532 99

Relaxation of smooth muscle can occur through agonists (such as nitric oxide) that activate guanylyl cyclase and stimulate the production of cGMP, activating its target, cGMP-dependent protein kinase (PKG). This kinase can raise the Ca2+ threshold for contraction, thus causing Ca2+ desensitization, but the mechanism for this event is not completely understood. Ca2+ sensitization/desensitization pathways are essential for maintenance of normal smooth muscle tone, and abnormalities in these pathways have been shown to be key components in the pathogenesis of diseases such as hypertension and asthma in humans. Our laboratory has devised a proteomic method to specifically address the question of what proteins are early phosphorylation targets in calcium desensitization. Using ileum smooth muscle, we metabolically labeled the muscle with (32P)-orthophosphate, permeabilized the muscle, established constant calcium concentrations, and stimulated with 8-bromo-cGMP, which activates PKG. Proteins whose phosphorylation state changed in response to cGMP at constant levels of calcium were separated with two-dimensional gel electrophoresis, identified by autoradiography, and sequenced with nanospray mass spectrometry. Using this technique, we identified a previously uncharacterized PKG phosphoprotein, which we have termed CHASM (Calponin Homology Smooth Muscle protein). Using physiological muscle bath contraction studies, we have validated CHASM as a component of calcium desensitization pathways in smooth muscle.
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PMID:Real-time in vivo proteomic identification of novel kinase substrates in smooth muscle. 1717 92