Calpain is required for macroautophagy in mammalian cells.
Ubiquitously expressed micro- and millicalpain, which both require the calpain small 1 (CAPNS1) regulatory subunit for function, play important roles in numerous biological and pathological phenomena. We have previously shown that the product of GAS2, a gene specifically induced at growth arrest, is an inhibitor of millicalpain and that its overexpression sensitizes cells to apoptosis in a p53-dependent manner (Benetti, R., G. Del Sal, M. Monte, G. Paroni, C. Brancolini, and C. Schneider. 2001. EMBO J. 20:2702-2714). More recently, we have shown that calpain is also involved in nuclear factor kappaB activation and its relative prosurvival function in response to ceramide, in which calpain deficiency strengthens the proapoptotic effect of ceramide (Demarchi, F., C. Bertoli, P.A. Greer, and C. Schneider. 2005. Cell Death Differ. 12:512-522). Here, we further explore the involvement of calpain in the apoptotic switch and find that in calpain-deficient cells, autophagy is impaired with a resulting dramatic increase in apoptotic cell death. Immunostaining of the endogenous autophagosome marker LC3 and electron microscopy experiments demonstrate that autophagy is impaired in CAPNS1-deficient cells. Accordingly, the enhancement of lysosomal activity and long-lived protein degradation, which normally occur upon starvation, is also reduced. In CAPNS1-depleted cells, ectopic LC3 accumulates in early endosome-like vesicles that may represent a salvage pathway for protein degradation when autophagy is defective.
Demarchi
Francesca
F
Laboratorio Nazionale Consorzio Interuniversitario Biotecnologie, 34012 Trieste, Italy.
Bertoli
Cosetta
C
Copetti
Tamara
T
Tanida
Isei
I
Brancolini
Claudio
C
Eskelinen
Eeva-Liisa
EL
Schneider
Claudio
C
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D002154:Calpain / Q000172:deficiency / Q000378:metabolism*; D002518:Ceramides / Q000494:pharmacology; D011992:Endosomes / Q000187:drug effects / Q000648:ultrastructure; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000648:ultrastructure; D015870:Gene Expression / Q000187:drug effects; D020868:Gene Silencing; D006801:Humans; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D010588:Phagosomes / Q000187:drug effects / Q000648:ultrastructure; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology
D002518:Ceramides; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D002154:Calpain; C410233:Capns1 protein, mouse; D020123:Sirolimus