Molecular cloning and characterization of the human transmembrane protein tyrosine phosphatase homologue, phogrin, an autoantigen of type 1 diabetes.
A 4.7 kb cDNA of tyrosine phosphatase-like protein, phogrin, was isolated from a human islet cDNA library. Sequencing of the resulting clone identified a 3,045 residue open-reading frame encoding a 1,015 amino acid polypeptide with predicted molecular mass of 111,303 daltons. Phogrin's amino acid sequence has a single transmembrane region and one putative tyrosine phosphatase catalytic domain. Phogrin is 74% identical to the ICA512/IA-2 autoantigen of type 1 diabetes in the cytoplasmic domain, but only 29% in the luminal domain. It showed > 90% identity to rat phogrin and mouse IA-2 beta. Autoantibody radioassays utilizing full-length and the cytoplasmic domain of phogrin were compared. With positivity defined above the 99th percentile of 105 normal control subjects, 37 (48%) and 47 (61%) of sera from 77 new-onset patients with type 1 diabetes were positive for autoantibodies to full-length and the cytoplasmic domain of phogrin, respectively. The assay utilizing cytoplasmic human phogrin gave higher sensitivity with identical specificity to the assay utilizing the full-length molecule primarily due to lower "background" binding. Phogrin is an additional major autoantigen for type 1 diabetes and the isolation of the cDNA of this molecule from human islets will aid in studies of the pathogenesis of type 1 diabetes.
Kawasaki
E
E
Barbara Davis Center for Childhood Diabetes, University of Colorado, Health Sciences Center, Denver 80262, USA.
Hutton
J C
JC
Eisenbarth
G S
GS
D000595:Amino Acid Sequence; D000818:Animals; D000936:Antigen-Antibody Complex; D001323:Autoantibodies; D001324:Autoantigens / Q000096:biosynthesis* / Q000737:chemistry; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D003922:Diabetes Mellitus, Type 1 / Q000201:enzymology / Q000276:immunology*; D006801:Humans; D007515:Islets of Langerhans / Q000201:enzymology / Q000276:immunology; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000737:chemistry; D016366:Open Reading Frames; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis* / Q000737:chemistry; D051381:Rats; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D017386:Sequence Homology, Amino Acid
D000936:Antigen-Antibody Complex; D001323:Autoantibodies; D001324:Autoantigens; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; C516862:PTPRN protein, human; C102889:PTPRN2 protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases; C516863:Ptprn protein, mouse; C516864:Ptprn protein, rat; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8