Cleavage of beta-catenin by calpain in prostate and mammary tumor cells.
Mutations in the NH(2)-terminal regulatory domain of the beta-catenin gene lead to aberrant stabilization and accumulation of the protein and increased TCF/LEF-dependent transcription. Although these mutations are common in some cancers, they are infrequent in prostate and breast cancer. We have found that metastatic prostate cancer specimens, obtained through a rapid autopsy tissue procurement program, expressed a novel M(r) 75,000 proteolytic fragment of beta-catenin (beta-cat(75)). beta-Cat(75) was also expressed in multiple prostate and breast cancer cell lines and was closely associated with the activity of the calcium-dependent protease, calpain. In a prostate cancer cDNA microarray, m-calpain RNA levels were found to be significantly increased in metastatic disease compared with normal prostate. We showed calpain-dependent generation of beta-cat(75) in cell culture and in vitro. Molecular mapping revealed that calpain cleavage removed the NH(2)-terminal regulatory domain of the beta-catenin protein. Treatment of MCF-7 cells with ionomycin led to increased accumulation of beta-cat(75) in the nucleus and TCF-dependent transcriptional activity. Overexpression of a similar beta-catenin fragment that lacks the NH(2)-terminal 132 amino acids and has transforming potential activated TCF-dependent transcription. Given the low frequency of mutation-induced activation of beta-catenin in prostate and breast cancers, proteolytic cleavage of beta-catenin by calpain may represent a novel mechanism by which the protein is activated during tumorigenesis.
Rios-Doria
Jonathan
J
Cellular and Molecular Biology Graduate Program, Department of Urology, Michigan Urology Center, Comprehensive Cancer Center, University of Michigan, Ann Arbor, Michigan, USA.
Kuefer
Rainer
R
Ethier
Stephen P
SP
Day
Mark L
ML
D001943:Breast Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D008297:Male; D009154:Mutation; D011471:Prostatic Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D051820:TCF Transcription Factors; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors / Q000235:genetics; D014162:Transfection; D051176:beta Catenin
C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D051820:TCF Transcription Factors; C544894:TCF7L2 protein, human; D015534:Trans-Activators; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; D051176:beta Catenin; D015759:Ionomycin; D002154:Calpain; D002118:Calcium