The Role of the E3-ubiquitin Ligase Trim17 in the Mitochondrial Cell Death Pathway

Abstract

The upregulation of apoptosis is a hallmark of several neurodegenerative disorders including ischemic stroke. In neurons, as in other cell types, Bax and tBid are critical regulators of the intrinsic pathway upstream of mitochondrial outer membrane permeabilization (MOMP) and caspase activation. The characterization of the molecular events that occur during the early stages is therefore extremely important from a therapeutic standpoint. Here I show that two independent genetic pilot screens looking for novel regulators of Bax activation identified a common hit in the E3 ubiquitin ligase Trim17. Knockdown of Trim17 was found to protect against tBid-induced death in primary cortical neurons and allowed for the maintenance of mitochondrial function and oxidative phosphorylation under this apoptotic stress. The RING-domain of Trim17 was found to interact with Opa1 in mouse brain extracts. Furthermore, Opa1 co-immunoprecipitated with exogenously expressed full-length Trim17 from HEK293 cells. Knockdown of Trim17 in neurons increased Opa1 protein levels under steady-state conditions. These results suggest that Trim17 regulates Bax-dependent apoptosis in neurons via the modulation of Opa1 levels.