Calpain mobilizes Atg9/Bif-1 vesicles from Golgi stacks upon autophagy induction by thapsigargin

: Marcassa Elena, Raimondi Marzia, Anwar Tahira, Eskelinen Eeva-Liisa, Myers Michael P., Triolo Gianluca, Schneider Claudio, Demarchi Francesca

Publisher: COMPANY OF BIOLOGISTS LTD

: 2017

: Biology Open

: BIOLOGY OPEN

: BIOL OPEN

: 6

: 5

: 551

: 562

: 12

: 2046-6390

DOI: https://doi.org/10.1242/bio.022806

: https://research.utu.fi/converis/portal/Publication/30914987

CAPNS1 is essential for stability and function of the ubiquitous calcium-dependent proteases micro- and milli-calpain. Upon inhibition of the endoplasmic reticulum Ca2+ ATPase by 100 nM thapsigargin, both micro- calpain and autophagy are activated in human U2OS osteosarcoma cells in a CAPNS1- dependent manner. As reported for other autophagy triggers, thapsigargin treatment induces Golgi fragmentation and fusion of Atg9/Bif-1-containing vesicles with LC3 bodies in control cells. By contrast, CAPNS1 depletion is coupled with an accumulation of LC3 bodies and Rab5 early endosomes. Moreover, Atg9 and Bif-1 remain in the GM130positive Golgi stacks and Atg9 fails to interact with the endocytic route marker transferrin receptor and with the core autophagic protein Vps34 in CAPNS1-depleted cells. Ectopic expression of a Bif-1 point mutant resistant to calpain processing is coupled to endogenous p62 and LC3-II accumulation. Altogether, these data indicate that calpain allows dynamic flux of Atg9/Bif-1 vesicles from the Golgi toward the budding autophagosome.

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