Molecular cloning of a human transmembrane-type protein tyrosine phosphatase and its expression in gastrointestinal cancers.
To determine the expression of various protein-tyrosine phosphatases (PTPs) in human gastric cancers, cDNAs encoding conserved PTP domains were amplified by reverse transcriptase polymerase chain reaction from KATO-III cell mRNA and sequenced. Among 72 polymerase chain reaction clones, one of the cDNA sequences encoded a novel potential PTP (stomach cancer-associated PTP, SAP-1). The full length (3.9 kilobases) of the SAP-1 cDNA was further isolated from the KATO-III cell cDNA library and the WiDr cell cDNA library. The predicted amino acid sequence of the SAP-1 cDNA showed that mature SAP-1 consisted of 1093 amino acids and a transmembrane-type PTP, which possessed a single PTP-conserved domain in the cytoplasmic region. The extracellular region of SAP-1 consisted of eight fibronectin type III-like structure repeats and contained multiple N-glycosylation sites. These data suggest that SAP-1 is structurally similar to HPTP beta and that SAP-1 and HPTP beta represent a subfamily of transmembrane-type PTPs. SAP-1 was mainly expressed in brain and liver and at a lower level in heart and stomach as a 4.2-kilobase mRNA, but it was not detected in pancreas or colon. In contrast, among cancer cell lines tested, SAP-1 was highly expressed in pancreatic and colorectal cancer cells. The bacterially expressed SAP-1 fusion protein had tyrosine-specific phosphatase activity. Immunoblotting with anti-SAP-1 antibody showed that SAP-1 is a 200-kDa protein. In addition, transient transfection of SAP-1 cDNA to COS cells resulted in the predominant expression of a 200-kDa protein recognized by anti-SAP-1 antibody. SAP-1 is mapped to chromosome 19 region q13.4 and might be related to carcinoembryonic antigen mapped to 19q13.2.
Matozaki
T
T
Second Department of Internal Medicine, Kobe University School of Medicine, Japan.
Suzuki
T
T
Uchida
T
T
Inazawa
J
J
Ariyama
T
T
Matsuda
K
K
Horita
K
K
Noguchi
H
H
Mizuno
H
H
Sakamoto
C
C
D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D003001:Cloning, Molecular / Q000379:methods; D017124:Conserved Sequence; D017931:DNA Primers; D018076:DNA, Complementary / Q000378:metabolism; D005770:Gastrointestinal Neoplasms / Q000201:enzymology*; D015870:Gene Expression; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000378:metabolism; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3; D011956:Receptors, Cell Surface; D017386:Sequence Homology, Amino Acid; D013274:Stomach Neoplasms / Q000201:enzymology; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D018076:DNA, Complementary; D008565:Membrane Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C431695:PTPRH protein, human; D017027:Protein Tyrosine Phosphatases; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3