PSD-93 Interacts with SynGAP and Promotes SynGAP Ubiquitination and Ischemic Brain Injury in Mice.

Qingxiu Zhang, Hui Yang, Hong Gao, Xiaomei Liu, Qingjie Li, Rong Rong, Zhenqian Liu, Xiu-E Wei, Liping Kong, Yun Xu, Liangqun Rong

Translational stroke research 2020 Oct

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Postsynaptic density protein-93 (PSD-93) plays an important role in ischemic brain injury through N-methyl-D-aspartate receptor (NMDAR)-triggered neurotoxicity. GTPase-activating protein for Ras (SynGAP) is a GAP specifically expressed in the central nervous system to regulate nerve development and synaptic plasticity. However, the link between PSD-93 and SynGAP and their role in ischemic brain injury remain elusive. Here, we showed that PSD-93 interacted with SynGAP and mediated SynGAP ubiquitination and degradation following ischemic brain injury. Proteasome inhibitor MG-132 could reverse the decrease of SynGAP protein level in wild-type mice following cerebral ischemia reperfusion through inhibiting SynGAP ubiquitination. Furthermore, NMDA receptor inhibitor MK801 could increase SynGAP protein level in wild-type mice following cerebral ischemia reperfusion. However, in PSD-93 knockout mice, MG-132 or NMDAR inhibitor had no significant effect on SynGAP expression. Both MG-132 and PSD-93 knockout reduced infarct volume and improved neurological deficit in mice at different time points after cerebral ischemia reperfusion. Furthermore, we identified that 670-685 amino acid sequence of SynGAP was essential to the binding of SynGAP to PSD-93, and designed a fusion peptide Tat-SynGAP (670-685aa) that could attenuate ischemic brain damage in wild-type mice. In conclusion, we provide the first evidence that PSD-93 directly interacts with SynGAP and mediates its ubiquitination and degradation to aggravate ischemic brain damage. Tat-SynGAP (670-685aa) may be considered as a candidate for treatment of acute ischemic stroke.

Citation

Qingxiu Zhang, Hui Yang, Hong Gao, Xiaomei Liu, Qingjie Li, Rong Rong, Zhenqian Liu, Xiu-E Wei, Liping Kong, Yun Xu, Liangqun Rong. PSD-93 Interacts with SynGAP and Promotes SynGAP Ubiquitination and Ischemic Brain Injury in Mice. Translational stroke research. 2020 Oct;11(5):1137-1147