title: The novel skeletal muscle sarcoplasmic reticulum JP-45 protein. Molecular cloning, tissue distribution, developmental expression, and interaction with alpha 1.1 subunit of the voltage-gated calcium channel.
abstract: JP-45 is a novel integral protein constituent of the skeletal muscle sarcoplasmic reticulum junctional face membrane. We identified its primary structure from a cDNA clone isolated from a mouse skeletal muscle cDNA library. Mouse skeletal muscle JP-45 displays over 86 and 50% identity with two hypothetical NCBI data base protein sequences from mouse tongue and human muscle, respectively. JP-45 is predicted to have a cytoplasmic domain, a single transmembrane segment followed by an intralumenal domain enriched in positively charged amino acids. Northern and Western blot analyses reveal that the protein is mainly expressed in skeletal muscle. The mRNA encoding JP-45 appears in 17-day-old mouse embryos; expression of the protein peaks during the second month of postnatal development and then decreases approximately 3-fold during aging. Double immunofluorescence of adult skeletal muscle fibers demonstrates that JP-45 co-localizes with the sarcoplasmic reticulum calcium release channel. Co-immunoprecipitation experiments with a monoclonal antibody against JP-45 show that JP-45 interacts with the alpha1.1 subunit voltage-gated calcium channel and calsequestrin. These results are consistent with the localization of JP-45 in the junctional sarcoplasmic reticulum and with its involvement in the molecular mechanism underlying skeletal muscle excitation-contraction coupling.
authors.affiliation: Department of Anesthesia, Zentrum Für Lehr und Forschung Kantonsspital Basel, Hebelstrasse 20, 4031 Basel, Switzerland.
authors.forename: Ayuk A
authors.initials: AA
authors.lastname: Anderson
authors.forename: Susan
authors.initials: S
authors.lastname: Treves
authors.forename: Donatella
authors.initials: D
authors.lastname: Biral
authors.forename: Romeo
authors.initials: R
authors.lastname: Betto
authors.forename: Doriana
authors.initials: D
authors.lastname: Sandonà
authors.forename: Michel
authors.initials: M
authors.lastname: Ronjat
authors.forename: Francesco
authors.initials: F
authors.lastname: Zorzato
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000254:growth & development / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
chemical_list: D020746:Calcium Channels, L-Type; D018076:DNA, Complementary; C485996:JP-45 protein, mouse; C418633:JSRP1 protein, human; D008565:Membrane Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins