A novel putative protein-tyrosine phosphatase contains a BRO1-like domain and suppresses Ha-ras-mediated transformation.
To investigate a potential role of protein-tyrosine phosphatases (PTPases) in myocardial growth and signaling, a degenerate primer-based reverse transcription-polymerase chain reaction approach was used to isolate cDNAs for proteins that contain a PTPase catalytic domain. Among the 16 cDNA clones isolated by reverse transcription-polymerase chain reaction from total neonatal rat cardiomyocyte RNA, one, designated PTP-TD14, was unique. Subsequent isolation and sequencing of a full-length PTP-TD14 cDNA confirmed that it encodes a novel 164-kDa protein, p164(PTP-TD14). The C-terminal region contains the PTP-like domain, whereas the N-terminal region shows no homology to any known mammalian protein. However, this region is homologous to a yeast protein, BRO1, that is involved in the mitogen-activated protein kinase signaling pathway. Like BRO1, p164(PTP-TD14) contains a proline-rich region with two putative SH3-domain binding sites. By Northern blot analysis, PTP-TD14 is expressed as a 5.3-kilobase pair transcript, not only in neonatal heart but also in many adult rat tissues. When expressed in either COS-7 or NIH-3T3 cells, p164(PTP-TD14) localizes to the cytoplasm in association with vesicle-like structures. Expression of p164(PTP-TD14) in NIH-3T3 cells inhibits Ha-ras-mediated transformation more than 3-fold. This inhibitory activity is localized to the C-terminal PTPase homology domain, since no inhibition of Ha-ras-mediated focus formation was observed with a PTP-TD14 mutant, in which the putative catalytic activity was presumably inactivated by a point mutation. These findings indicate that PTP-TD14 encodes a novel protein that may be critically involved in regulating Ha-ras-dependent cell growth.
Victor Chang Cardiac Research Institute, St. Vincent's Hospital, Darlinghurst, NSW 2010, Australia.
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Cao
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Zhang
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Ruiz-Lozano
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Yang
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Chien
R M
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Graham
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Zhou
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D018076:DNA, Complementary; D011905:Genes, ras; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009206:Myocardium / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054558:Protein Tyrosine Phosphatases, Non-Receptor; D051381:Rats; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D017027:Protein Tyrosine Phosphatases; D054558:Protein Tyrosine Phosphatases, Non-Receptor; C520791:Ptpn23 protein, rat