Modulation of smooth muscle contractility by CHASM, a novel member of the smoothelin family of proteins.
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.
Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA.
Meredith A
MA
Borman
Justin A
JA
MacDonald
Timothy A J
TA
Haystead
D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000737:chemistry; D015180:Electrophoresis, Gel, Two-Dimensional; D004928:Escin / Q000378:metabolism; D066298:In Vitro Techniques; D051379:Mice; D008969:Molecular Sequence Data; D005810:Multigene Family; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009124:Muscle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011817:Rabbits; D000096985:Calponins
D000199:Actins; D002118:Calcium; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D006152:Cyclic GMP; D003598:Cytoskeletal Proteins; D004928:Escin; D009124:Muscle Proteins; D010750:Phosphoproteins; C491838:SMTNL1 protein, mouse; D000096985:Calponins; C491050:Smtn protein, mouse; C016276:8-bromocyclic GMP