Cleavage of MAGI-1, a tight junction PDZ protein, by caspases is an important step for cell-cell detachment in apoptosis |
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Authors: | Uroš Gregorc Saška Ivanova Miranda Thomas Ernesto Guccione Britt Glaunsinger Ron Javier Vito Turk Lawrence Banks Boris Turk |
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Affiliation: | (1) Department of Biochemistry and Molecular Biology, J. Stefan Institute, Ljubljana, Slovenia;(2) International Centre for Genetic Engineering and Biotechnology, Padriciano 99, I-34012 Trieste, Italy;(3) Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA |
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Abstract: | MAGI-1, a member of the MAGUK family of proteins, is shown to be rapidly cleaved during Fas-induced apoptosis in mouse 3T3 A31 cells, and in UV irradiation- and staurosporine-induced apoptosis in HaCaT cells. This generates a 97 kDa N-terminal fragment that dissociates from the cell membrane; a process that is largely prevented in the presence of the caspase inhibitor Z-VAD-fmk. In addition, we show that in vitro translated radiolabelled MAGI-1 is efficiently cleaved into 97 kDa and 68 kDa fragments by caspases-3 and -7 at physiological concentrations and mutating the MAGI-1 Asp761 to Ala completely abolished the caspase-induced cleavage. Moreover, in HaCaT cells overexpressing the MAGI-1 Asp761Ala mutant the disruption of cell-cell contacts was delayed during apoptosis, whereas other caspase-dependent processes such as nuclear condensation were not affected, suggesting that cell detachment is parallel to them. Thus, MAGI-1 cleavage appears to be an important step in the disassembly of cell-cell contacts during apoptosis. |
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Keywords: | Apoptosis Caspase MAGI-1 PDZ Tight junction |
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