title: The receptor tyrosine phosphatase-like protein ICA512 binds the PDZ domains of beta2-syntrophin and nNOS in pancreatic beta-cells.
abstract: Islet cell autoantigen (ICA) 512 of type I diabetes is a receptor tyrosine phosphatase-like protein associated with the secretory granules of neurons and endocrine cells including insulin-secreting beta-cells of the pancreas. Here we show that in a yeast two-hybrid assay its cytoplasmic domain binds beta2-syntrophin, a modular adapter which in muscle cells interacts with members of the dystrophin family including utrophin, as well as the signaling molecule neuronal nitric oxide synthase (nNOS). The cDNA isolated by two-hybrid screening corresponded to a novel beta2-syntrophin isoform with a predicted molecular mass of 28 kDa. This isoform included the PDZ domain, but not the C-terminal region, which in full-length beta2-syntrophin is responsible for binding dystrophin-related proteins. In vitro binding of the beta2-syntrophin PDZ domain to ICA512 required both ICA512's C-terminal region and an internal polypeptide preceding its tyrosine phosphatase-like domain. Immunomicroscopy and co-immunoprecipitations from insulinoma INS-1 cells confirmed the occurrence of ICA512-beta2-syntrophin complexes in vivo. ICA512 also interacted in vitro with the PDZ domain of nNOS and ICA512-nNOS complexes were co-immunoprecipitated from INS-1 cells. Finally, we show that INS-1 cells, like muscle cells, contain beta2-syntrophin-utrophin oligomers. Thus, we propose that ICA512, through beta2-syntrophin and nNOS, links secretory granules with the actin cytoskeleton and signaling pathways involving nitric oxide.
authors.affiliation: Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
authors.forename: T
authors.initials: T
authors.lastname: Ort
authors.forename: E
authors.initials: E
authors.lastname: Maksimova
authors.forename: R
authors.initials: R
authors.lastname: Dirkx
authors.forename: A M
authors.initials: AM
authors.lastname: Kachinsky
authors.forename: S
authors.initials: S
authors.lastname: Berghs
authors.forename: S C
authors.initials: SC
authors.lastname: Froehner
authors.forename: M
authors.initials: M
authors.lastname: Solimena
mesh_terms: D000483:Alleles; D017398:Alternative Splicing / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D001324:Autoantigens; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D016384:Consensus Sequence; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D016189:Dystrophin / Q000378:metabolism; D049029:Dystrophin-Associated Proteins; D015870:Gene Expression / Q000502:physiology; D007340:Insulinoma; D007515:Islets of Langerhans / Q000166:cytology / Q000201:enzymology*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D019001:Nitric Oxide Synthase / Q000737:chemistry / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D017434:Protein Structure, Tertiary; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D051381:Rats; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques; D000099160:LexA Repressor Protein
chemical_list: D001324:Autoantigens; D001426:Bacterial Proteins; D016189:Dystrophin; D049029:Dystrophin-Associated Proteins; D008565:Membrane Proteins; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D017027:Protein Tyrosine Phosphatases; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein; C091824:syntrophin; C496322:Nos1 protein, rat; C516864:Ptprn protein, rat