Elevated post-ischemic ubiquitination results from suppression of deubiquitinase activity and not proteasome inhibition.

Elevated post-ischemic ubiquitination results from suppression of deubiquitinase activity and not proteasome inhibition.
Cell Mol Life Sci. 2020 Sep 05;:
Authors: Kahles T, Poon C, Qian L, Palfini V, Srinivasan SP, Swaminathan S, Blanco I, Rodney-Sandy R, Iadecola C, Zhou P, Hochrainer K
Abstract
Cerebral ischemia-reperfusion increases intraneuronal levels of ubiquitinated proteins, but the factors driving ubiquitination and whether it results from altered proteostasis remain unclear. To address these questions, we used in vivo and in vitro models of cerebral ischemia-reperfusion, in which hippocampal slices were transiently deprived of oxygen and glucose to simulate ischemia followed by reperfusion, or the middle cerebral artery was temporarily occluded in mice. We found that post-ischemic ubiquitination results from two key steps: restoration of ATP at reperfusion, which allows initiation of protein ubiquitination, and free radical production, which, in the presence of sufficient ATP, increases ubiquitination above pre-ischemic levels. Surprisingly, free radicals did not augment ubiquitination through inhibition of the proteasome as previously believed. Although reduced proteasomal activity was detected after ischemia, this was neither caused by free radicals nor sufficient in magnitude to induce appreciable accumulation of proteasomal target proteins or ubiquitin-proteasome reporters. Instead, we found that ischemia-derived free r...

Source: Cellular and Molecular Life Sciences : CMLS - September 4, 2020 Category: Cytology Authors: Kahles T, Poon C, Qian L, Palfini V, Srinivasan SP, Swaminathan S, Blanco I, Rodney-Sandy R, Iadecola C, Zhou P, Hochrainer K Tags: Cell Mol Life Sci Source Type: research