title: Cain, a novel physiologic protein inhibitor of calcineurin.
abstract: Calcineurin is a widely distributed protein phosphatase regulated by calcium and calmodulin. It mediates the immunosuppressive actions of drugs such as cyclosporin and FK506, and has been implicated in a number of calcium-sensitive pathways in the nervous system, including regulation of neurotransmitter release and modulation of long-term changes in synaptic plasticity. Calcineurin associates physiologically with other proteins, including calmodulin, FKBP12 (FK506-binding protein), the ryanodine receptor, and the inositol 1,4,5-trisphosphate receptor. We now report the identification, molecular cloning, and functional characterization of a novel protein, cain (calcineurin inhibitor), that interacts with and inhibits calcineurin. The full-length cain cDNA predicts a 240-kDa protein with no significant homology to any known protein. Cain associates with calcineurin both in vitro and in vivo, leading to a non-competitive inhibition of calcineurin activity. The putative calcineurin-binding domain of cain, a 38-amino acid region defined by mutational analysis, is highly basic. Like calcineurin, cain has a prominent neuronal expression and a wide tissue distribution. Cain's expression pattern in the brain closely resembles that of calcineurin, indicating a physiologic association between the two proteins.
authors.affiliation: Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Lai
authors.forename: P E
authors.initials: PE
authors.lastname: Burnett
authors.forename: H
authors.initials: H
authors.lastname: Wolosker
authors.forename: S
authors.initials: S
authors.lastname: Blackshaw
authors.forename: S H
authors.initials: SH
authors.lastname: Snyder
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D065095:Calcineurin Inhibitors; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D002384:Catalysis; D002460:Cell Line; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D015723:Gene Library; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010957:Plasmids; D011485:Protein Binding; D051381:Rats; D012441:Saccharomyces cerevisiae; D016559:Tacrolimus / Q000494:pharmacology; D022021:Tacrolimus Binding Proteins
chemical_list: D051017:Apoptosis Regulatory Proteins; C113573:Cabin1 protein, rat; D065095:Calcineurin Inhibitors; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D006360:Heat-Shock Proteins; D022021:Tacrolimus Binding Proteins; D016559:Tacrolimus