616 / 2019-04-24 10:00:19

Two Arabidopsis protein quality control regulators, E3 ubiquitin ligase MPSR1 and molecular chaperone HSP90.1, are under the reciprocal suppressive regulation

Protein quality control,MSPR1,HSP90.1

全体主题 > Abiotic Stress

MPSR1 (Misfolded Protein Sensing RING protein 1) is an Arabidopsis E3 ubiquitin (Ub) ligase that eliminates misfolded proteins arising from proteotoxic stress. HSP90.1 is a well-characterized molecular chaperone that is also critical to maintain protein homeostasis under proteotoxic condition. In this report, we show that two protein quality regulators MPSR1 and HSP90.1 are under the reciprocal suppressive regulation in the progress of proteotoxicity. At the early stage of proteotoxicity, the levels of MPSR1 increased, while cellular levels of HSP90.1 stayed unchanged despite the upregulated transcription. As the proteotoxic stress continued, however, the cellular levels of HSP90.1 increased, while the levels of MPSR1 decreased. Induction of HSP90.1 resulted in the decreased MPSR1 protein levels under proteotoxic condition. Bacterially expressed HSP90.1 interrupted in vitro binding of MPSR1 and its target misfolded protein ∆2GFP and restored self-ubiquitination activity of MPSR1. Overexpression or knock-down of MPSR1 repressed or promoted, respectively, the accumulation of HSP90.1 under proteotoxic stress without transcriptional changes. Collectively, we propose that MPSR1 suppresses translation of HSP90.1 at the early stage of proteotoxicity and HSP90.1 promotes self-ubiquitination and degradation of MPSR1 at the later step.