The role of calpain in the proteolytic cleavage of E-cadherin in prostate and mammary epithelial cells.
The E-cadherin protein mediates Ca(2+)-dependent interepithelial adhesion. Association of E-cadherin with the catenin family of proteins is critical for the maintenance of a functional adhesive complex. We have identified a novel truncated E-cadherin species of 100-kDa (E-cad(100)) in prostate and mammary epithelial cells. E-cad(100) was generated by treatment of cells with ionomycin or TPA. Cell-permeable calpain inhibitors prevented E-cad(100) induction by ionomycin. Immunoblotting for spectrin and mu-calpain confirmed calpain activation in response to ionomycin treatment. Both the mu- and m-isoforms of calpain efficiently generated E-cad(100) in vitro. The E-cad(100) fragment was unable to bind to beta-catenin, gamma-catenin, and p120, suggesting that this cleavage event would disrupt the E-cadherin adhesion complex. Mutational analysis localized the calpain cleavage site to the cytosolic domain upstream of the beta- and gamma-catenin binding motifs of E-cadherin. Because E-cadherin is inactivated in many adenocarcinomas we hypothesized that calpain may play a role in prostate tumorigenesis. A prostate cDNA microarray data base was analyzed for calpain expression in which it was found that m-calpain was up-regulated in localized prostate cancer, and to an even higher degree in metastatic prostate cancer compared with normal prostate tissue. Furthermore, we examined the cleavage of E-cadherin in prostate cancer specimens and found that E-cad(100) accumulated in both localized and metastatic prostate tumors, supporting the cDNA microarray data. These findings demonstrate a novel mechanism by which E-cadherin is functionally inactivated through calpain-mediated proteolysis and suggests that E-cadherin is targeted by calpain during the tumorigenic progression of prostate cancer.
Rios-Doria
Jonathan
J
Department of Urology, University of Michigan, Ann Arbor 48109, USA.
Day
Kathleen C
KC
Kuefer
Rainer
R
Rashid
Michael G
MG
Chinnaiyan
Arul M
AM
Rubin
Mark A
MA
Day
Mark L
ML
D000595:Amino Acid Sequence; D001940:Breast / Q000378:metabolism*; D015820:Cadherins / Q000737:chemistry / Q000378:metabolism*; D002154:Calpain / Q000502:physiology*; D002460:Cell Line; D004847:Epithelial Cells / Q000378:metabolism; D018604:Epitope Mapping; D005260:Female; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D008297:Male; D008969:Molecular Sequence Data; D011467:Prostate / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism; D011493:Protein Kinase C / Q000502:physiology
D015820:Cadherins; D015759:Ionomycin; D011493:Protein Kinase C; D002154:Calpain