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Molecular characterization of human tensin
1Center for Tissue Regeneration and Repair, Department of Orthopaedic Surgery, The University of California-Davis, 4635 Second Avenue, Sacramento, CA 95817, USA.
The Biochemical Journal
|October 12, 2000
Summary
Researchers cloned human and cow tensin cDNAs, revealing structural differences from chicken tensin. Tensin is often absent in cancer cells and its cleavage by calpain II impacts cell shape.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Tensin is a focal-adhesion molecule crucial for cell structure, interacting with actin filaments and phosphotyrosine proteins.
- Understanding tensin's mammalian function requires detailed molecular analysis and interspecies comparison.
Purpose of the Study:
- To clone and analyze tensin cDNAs from human and bovine sources to elucidate its mammalian function.
- To compare mammalian tensin structure with its chicken counterpart and investigate its expression and regulation.
Main Methods:
- Cloning of human and bovine tensin cDNAs.
- Amino acid sequence analysis and comparison with chicken tensin.
- Northern-blot analysis for tissue-specific expression.
- SDS/PAGE and Western-blot analysis for protein migration and expression in cancer cell lines.
- Calpain II inhibition studies using MDL.
Main Results:
- Human tensin cDNA encodes a 1735-amino acid protein with conserved structural features (actin-binding domains, SH2 domain, PTEN-like region) but lacks N-terminal residues and has unique inserts compared to chicken tensin.
- A glutamine/CAG repeat expansion was observed across species.
- Tensin is expressed as a 10-kb message in most human tissues, with an additional 9-kb message in muscle tissues. Predicted 185 kDa protein migrates as 220 kDa due to central region's low electrophoretic mobility.
- Tensin expression is significantly reduced or absent in most human prostate and breast cancer cell lines, unlike other focal-adhesion molecules.
- Calpain II rapidly cleaves tensin; inhibition of calpain II prevents cleavage and induces cell morphological changes.
Conclusions:
- Mammalian tensin exhibits structural variations from avian tensin, including sequence insertions and repeat expansions, suggesting evolutionary adaptation.
- The absence of tensin in many cancer cell lines indicates a potential role in tumor suppression.
- Calpain II-mediated cleavage of tensin disrupts focal adhesions and cell shape maintenance, highlighting its role in cellular integrity.