PTEN 2, a Golgi-associated testis-specific homologue of the PTEN tumor suppressor lipid phosphatase.
The tumor suppressor PTEN is a phosphatidylinositol phospholipid phosphatase, which indirectly down-regulates the activity of the protein kinase B/Akt survival kinases. Examination of sequence data bases revealed the existence of a highly conserved homologue of PTEN. This homologue, termed PTEN 2, contained an extended amino-terminal domain having four potential transmembrane motifs, a lipid phosphatase domain, and a potential lipid-binding C2 domain. Transcript analysis demonstrated that PTEN 2 is expressed only in testis and specifically in secondary spermatocytes. In contrast to PTEN, PTEN 2 was localized to the Golgi apparatus via the amino-terminal membrane-spanning regions. Molecular modeling suggested that PTEN 2 is a phospholipid phosphatase with potential specificity for the phosphate at the 3 position of inositol phosphates. Enzymatic analysis of PTEN 2 revealed substrate specificity that is similar to PTEN, with a preference for the dephosphorylation of the phosphatidylinositol 3,5-phosphate phospholipid, a known mediator of vesicular trafficking. Together, these data suggest that PTEN 2 is a Golgi-localized, testis-specific phospholipid phosphatase, which may contribute to the terminal stages of spermatocyte differentiation.
Wu
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Y
Department of Molecular Oncology, Genentech, Inc., South San Francisco, California 94080, USA.
Dowbenko
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D
Pisabarro
M T
MT
Dillard-Telm
L
L
Koeppen
H
H
Lasky
L A
LA
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D017124:Conserved Sequence; D004622:Embryo, Mammalian; D020224:Expressed Sequence Tags; D016147:Genes, Tumor Suppressor; D006056:Golgi Apparatus / Q000201:enzymology*; D006801:Humans; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009928:Organ Specificity; D051059:PTEN Phosphohydrolase; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017027:Protein Tyrosine Phosphatases; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013737:Testis / Q000201:enzymology*; D014158:Transcription, Genetic; D014162:Transfection; D025521:Tumor Suppressor Proteins
D008565:Membrane Proteins; D011994:Recombinant Proteins; D025521:Tumor Suppressor Proteins; D010744:Phosphoric Monoester Hydrolases; D017027:Protein Tyrosine Phosphatases; C446603:TPTE protein, human; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human