PAX6, modified by SUMOylation, plays a protective role in corneal endothelial injury.

Treating corneal endothelial diseases tends to be challenging as human corneal endothelial cells (CECs) do not proliferate in vivo. The pathogenesis or mechanisms underlying injured CECs need further studies. The abnormal expression of PAX6, which is an essential transcription factor for corneal homeostasis, exhibits corneal endothelial defects. However, the effects of PAX6 protein involved in corneal endothelial wound process are still unknown. Here, we found the upregulated protein levels of PAX6 in human corneal endothelial monolayer after injury; the expression of PAX6 also increased in murine and rat corneal endothelium injury models. Enforced PAX6 expression could alleviate the damages to CECs via regulating permeability by prompting cellular tight junction. In addition, SUMOylation mainly happened on both K53 and K89 residues of 48-kD PAX6 (the longest and main isoform expressed in cornea), and de-SUMOylation promoted the stability of PAX6 protein in vitro. In CECs of SENP1+/- mice, increased SUMOylation levels leading to instability and low expression of PAX6, delayed the repair of CECs after injury. Furthermore, overexpression of PAX6 accelerated the rate of corneal endothelial repair of SENP1+/- mice. Our findings indicate that SENP1-mediated de-SUMOylation improving the stability of PAX6, amplifies the protective effects of PAX6 on corneal endothelial injuries, highlighting potentials of PAX6 and/or SUMOylation to be used as a treatment target for corneal endothelial disorders.

Forebrain excitatory neuron-specific SENP2 knockout mouse displays hyperactivity, impaired learning and memory, and anxiolytic-like behavior.

Sentrin/SUMO-specific protease 2 (SENP2) is a member of SENPs family involved in maturation of SUMO precursors and deSUMOylation of specific target, and is highly expressed in the central nervous system (CNS). Although SENP2 has been shown to modulate embryonic development, fatty acid metabolism, atherosclerosis and epilepsy, the function of SENP2 in the CNS remains poorly understood. To address the role of SENP2 in the CNS and its potential involvement in neuropathology, we generated SENP2 conditional knockout mice by crossing floxed SENP2 mice with CaMKIIα-Cre transgenic mice. Behavioral tests revealed that SENP2 ablation induced hyper-locomotor activity, anxiolytic-like behaviors, spatial working memory impairment and fear-associated learning defect. In line with these observations, our RNA sequencing (RNA-seq) data identified a variety of differential expression genes that are particularly enriched in locomotion, learning and memory related biologic process. Taken together, our results indicated that SENP2 plays a critical role in emotional and cognitive regulation. This SENP2 conditional knockout mice model may help reveal novel mechanisms that underlie a variety of neuropsychiatric disorders associated with anxiety and cognition.

PKC SUMOylation inhibits the binding of 14-3-3τ to GluK2.

Phosphorylation and SUMOylation of the kainate receptor (KAR) subunit GluK2 have been shown to regulate KAR surface expression, trafficking and synaptic plasticity. In addition, our previous study has shown that a phosphorylation-dependent interaction of 14-3-3τ and GluK2a-containing receptors contributes to the slow decay kinetics of native KAR-EPSCs. However, it is unknown whether SUMOylation participates in the regulation of the interaction between 14-3-3τ and GluK2a-containing receptors. Here we report that SUMOylation of PKC, but not GluK2, represses the binding of 14-3-3τ to GluK2a via decreasing the phosphorylation level of GluK2a. These results suggest that PKC SUMOylation is an important regulator of the 14-3-3 and GluK2a protein complex and may contribute to regulate the decay kinetics of KAR-EPSCs.

SUMO-specific protease 1 protects neurons from apoptotic death during transient brain ischemia/reperfusion.

SUMO-specific protease 1 (SENP1) deconjugates SUMO from modified proteins. Although post-ischemic activation of SUMO conjugation was suggested to be neuroprotective against ischemia/reperfusion (I/R) injury, the function of SENP1 in this process remained unclear. Here we show that transient middle cerebral artery occlusion in mice followed by 6, 12 and 24 h reperfusion significantly enhanced SENP1 levels in the affected brain area, independent of transcription. Consistent with the increase in SENP1, the levels of SUMO1-conjugated proteins were decreased by I/R in cortical neurons of control littermate mice, but unchanged in that of animals with conditional ablation of SENP1 gene from adult principal neurons, the SENP1flox/flox:CamKIIα-Cre (SENP1 cKO) mice. The SENP1 cKO mice exhibited a significant increase in infarct volume in the cerebral cortex and more severe motor impairment in response to I/R as compared with the control littermates. Cortical neurons from I/R-injured SENP1 cKO mice became more apoptotic than that from control littermates, as indicated by both TUNEL staining and caspase-3 activation. Overexpression of SENP1 in somatosensory cortices of adult wild-type (WT) mice suppressed I/R-induced neuronal apoptosis. We conclude that SENP1 plays a neuroprotective role in I/R injury by inhibiting apoptosis through decreasing SUMO1 conjugation. These findings reveal a novel mechanism of neuroprotection by protein desumoylation, which may help develop new therapies for mitigating brain injury associated with ischemic stroke.