Cypher, a striated muscle-restricted PDZ and LIM domain-containing protein, binds to alpha-actinin-2 and protein kinase C.
We have cloned and characterized a novel striated muscle-restricted protein (Cypher) that has two mRNA splice variants, designated Cypher1 and Cypher2. Both proteins contain an amino-terminal PDZ domain. Cypher1, but not Cypher2, contains three carboxyl-terminal LIM domains and an amino acid repeat sequence that exhibits homology to a repeat sequence found in the largest subunit of RNA polymerase II. cypher1 and cypher2 mRNAs exhibited identical expression patterns. Both are exclusively expressed in cardiac and striated muscle in embryonic and adult stages. By biochemical assays, we have demonstrated that Cypher1 and Cypher2 bind to alpha-actinin-2 via their PDZ domains. This interaction has been further confirmed by immunohistochemical studies that demonstrated co-localization of Cypher and alpha-actinin at the Z-lines of cardiac muscle. We have also found that Cypher1 binds to protein kinase C through its LIM domains. Phosphorylation of Cypher by protein kinase C has demonstrated the functional significance of this interaction. Together, our data suggest that Cypher1 may function as an adaptor in striated muscle to couple protein kinase C-mediated signaling, via its LIM domains, to the cytoskeleton (alpha-actinin-2) through its PDZ domain.
Department of Medicine, UCSD-Salk Program in Molecular Medicine, University of California at San Diego, School of Medicine, La Jolla, California 92093-0613, USA.
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Martone
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D000185:Actinin / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins; D003001:Cloning, Molecular; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins; D006801:Humans; D060588:LIM Domain Proteins; D051379:Mice; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000737:chemistry / Q000235:genetics*; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D016415:Sequence Alignment
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018398:Homeodomain Proteins; C120696:LDB3 protein, human; D060588:LIM Domain Proteins; C485639:Ldb3 protein, mouse; D009124:Muscle Proteins; D012333:RNA, Messenger; D000185:Actinin; D011493:Protein Kinase C