VMP1-mediated autophagy is regulated by ubiquitination in pancreatic cancer cells

RENNA, F. J.; ENRIQUÉ STEINBERG, J.; TADIC, M.; ORQUERA, T.; VECINO, C.; ALEJANDRO JAVIER ROPOLO; ROSSI, M.; VACCARO, M. I.

Ciudad Autónoma de Buenos Aires

Congreso; VI International Congress in Translational Medicine; 2023

Universidad de Buenos Aires - Embajada de Alemania - Centro Universitario Argentino Alemán - Universidad Nacional de Cuyo

Autophagy constitutes a tightly controlled breakdown process engaged in the degradation and renewal of proteins and cellular components. The orchestration of autophagy heavily relies on ubiquitination. A fundamental participant in autophagy is Vacuole Membrane Protein 1 (VMP1). In instances of pancreatic cancer stem cells bearing the activated Kirsten rat sarcoma viral oncogene homolog (KRAS), VMP1 expression sparks autophagy and fosters resilience against therapeutic interventions. Through a combination of biochemical and cellular methods, we have pinpointed ubiquitination as a post-translational adjustment occurring in the initial stages of autophagosome generation for VMP1. The ubiquitination of VMP1 endures throughout the autophagic process, enveloping VMP1 within the autophagosome membrane until the creation of autolysosomes. Notably, this ubiquitination doesn't prompt VMP1 degradation, whether through autophagy or the ubiquitin-proteasomal system. By employing mass spectrometry and immunoprecipitation, we've established that the cell division cycle protein cdt2 (Cdt2), a key component of the E3 ligase complex named cullin-RING ubiquitin ligase complex 4 (CRL4) linked with cancer, interacts with VMP1 in an unprecedented manner, thus participating in VMP1's ubiquitination process. This ubiquitination of VMP1 wanes when exposed to the CRL inhibitor MLN4924 but intensifies when Cdt2 is overexpressed. In addition, the inhibition of CRL significantly impacts VMP1's recruitment and the formation of autophagosomes. Furthermore, we discovered that inhibiting VMP1 ubiquitination with MLN4924 treatment significantly reduces therapeutic resistance in pancreatic cancer cells. These findings underscore the innovative nature of ubiquitination as a post-translational alteration of VMP1 during autophagy in pancreatic cancer cells. The ubiquitination of VMP1 might hold clinical significance in the context of tumor cell therapy resistance.