Maintaining 26S proteasome activity under diverse physiological conditions is a fundamental requirement in order to maintain cellular proteostasis. Several quantitative and qualitative mechanisms have evolved to ensure that ubiquitin-proteasome system (UPS) substrates do not accumulate and lead to promiscuous protein-protein interactions that, in turn, lead to cellular malfunction. In this report, we demonstrate that Arsenite Inducible Regulatory Particle-Associate Protein (AIRAP), previously reported as a proteasomal adaptor required for maintaining proteasomal flux during arsenite exposure, can directly bind arsenite molecules. We further show that arsenite inhibits Psmd14/Rpn11 metalloprotease deubiquitination activity by substituting zinc binding to the MPN/JAMM domain. The proteasomal adaptor AIRAP is able to directly relieve PSMD14/Rpn11 inhibition. A possible metal relay between arsenylated PSMD14/Rpn11 and AIRAP may serve as a cellular mechanism that senses proteasomal inhibition to restore Psmd14/Rpn11 activity.
Keywords: AIRAP; PSMD14/RPN11; arsenite; proteasome; protein misfolding; proteostasis.