Inhibition of synaptophysin ubiquitination may improve the intelligent drop due to high glucose and hypoxia.

Synaptophysin (SYP) is a synaptic vesicle membrane protein and involved in the release of neurotransmitters, synaptic plasticity, and formation and recycling of synaptic vesicles. SYP may serve as a specific marker of synaptic proteins. Our results showed high glucose and hypoxia could significantly impair the intelligence and the SYP level was positively related to the degree of intelligence in animals. Ubiquitination may influence the SYP expression. In our study, an ubiquitination inhibitor (MG-132) was injected intraperitoneally. Results showed this could increase SYP expression in the brain to improve the intelligent drop due to high glucose and hypoxia in animals. SYP ubiquitination is closely associated with E3 ubiquitin ligase, a mammalian homologue of seven in absentia. In our study, lentivirus expressing siah shRNA was injected into the cerebral ventricle to down-regulate siah expression, and results showed the SYP expression in the brain increased markedly. In addition, we also found that VitK3 could increase the SYP expression in the brain to improve the intelligent drop due to high glucose and hypoxia.