Molecular characterization of human tensin.
Tensin is a focal-adhesion molecule that binds to actin filaments and interacts with phosphotyrosine-containing proteins. To analyse tensin's function in mammals, we have cloned tensin cDNAs from human and cow. The isolated approx. 7.7-kb human cDNA contains an open reading frame encoding 1735 amino acid residues. The amino acid sequence of human tensin shares 60% identity with chicken tensin, and contains all the structural features described previously in chicken tensin. This includes the actin-binding domains, the Src homology domain 2, and the region similar to a tumour suppressor, PTEN. Two major differences between human and chicken tensin are (i) the lack of the first 54 residues present in chicken tensin, and (ii) the addition of 34- and 38-residue inserts in human and bovine tensin. In addition, our interspecies sequencing data have uncovered the presence of a glutamine/CAG repeat that appears to have expanded in the course of evolution. Northern-blot analysis reveals a 10-kb message in most of the human tissues examined. An additional 9-kb message is detected in heart and skeletal muscles. The molecular mass predicted from the human cDNA is 185 kDa, although both endogenous and recombinant human tensin migrate as 220-kDa proteins on SDS/PAGE. The discrepancy is due to the unusually low electrophoretic mobility of the central region of the tensin polypeptide (residues 306-981). A survey of human prostate and breast cancer cell lines by Western-blot analysis shows a lack of tensin expression in most cancer cell lines, whereas these lines express considerable amounts of focal-adhesion molecules such as talin and focal-adhesion kinase. Finally, tensin is rapidly cleaved by a focal-adhesion protease, calpain II. Incubation of cells with a calpain inhibitor, MDL, prevented tensin cleavage and induced morphological change in these cells, suggesting that cleavage of tensin and other focal-adhesion constituents by calpain disrupts maintenance of normal cell shape.
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Center for Tissue Regeneration and Repair, Department of Orthopaedic Surgery, The University of California-Davis, 4635 Second Avenue, Sacramento, CA 95817, USA.
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D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism; D002417:Cattle; D002645:Chickens; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D015723:Gene Library; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D008840:Microfilament Proteins / Q000737:chemistry* / Q000235:genetics*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011471:Prostatic Neoplasms / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D000070876:Tensins; D013997:Time Factors; D014018:Tissue Distribution; D014162:Transfection; D014407:Tumor Cells, Cultured
D018076:DNA, Complementary; D008840:Microfilament Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D000070876:Tensins; D005982:Glutathione Transferase; D002154:Calpain