GTPase-mediated regulation of the Unfolded Protein Response in C. elegans is dependent on the AAA⁺ ATPase CDC-48

Dept of Surgery, McGill University, Montreal, Qc, Canada; INSERM, U889, Team Avenir, Bordeaux, France; Dept of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada; Innovation Centre, McGill University, Montreal, Qc, Canada; Faculty of Pharmacy, University of Montreal, Montreal, Qc, Canada; University Bordeaux 2, Bordeaux, France

^* To whom correspondence should be addressed. Email: eric.chevet{at}u-bordeaux2.fr.

	Abstract

When Endoplasmic Reticulum (ER) homeostasis is perturbed, an adaptive mechanism is triggered and named the Unfolded Protein Response (UPR). Thus far, three known UPR signaling branches (IRE-1, PERK, ATF6) mediate the re-establishment of ER functions, but can also lead to apoptosis if ER stress is not alleviated. However, the understanding of the molecular mechanisms integrating the UPR to other ER functions such as membrane traffic or endomembrane signaling, remains incomplete. We consequently sought to identify new regulators of UPR-dependent transcriptional mechanisms and focused on a family of proteins known to mediate, amongst other, ER-related functions: the small GTP-binding proteins of the RAS super-family. To this end, we used transgenic UPR-reporter C. elegans strains as a model to specifically silence small GTPases expression. We show that the Rho subfamily member CRP-1 is an essential component of UPR-induced transcriptional events through its physical and genetic interactions with the AAA⁺ ATPase CDC-48. In addition, we describe a novel signaling module involving CRP-1 and CDC-48 which may directly link the UPR to DNA remodeling and transcription control.