CDK5-Induced BAG3 Phosphorylation Affects Disorder Of Cell Cycle In The OGD Models

CDK5 is a special member of the cyclin dependent kinase family proteins, highly expressed in the central nervous system. The previous study showed that CDK5 was activated in the middle cerebral artery occlusion models, and neurons entered into cell cycle and underwent apoptosis. BAG3/Bis (athanogene Bcl2-associated 3) protein is a member of the BAG family. BAG3 level increased after ischemic stress stimulation. However, very little is known regarding the biological function of the CDK5-BAG3 signaling regulation. Here, we studied the effect of Cdk5-Bag3 signaling regulation on cell cycle disorder and apoptosis in the oxygen-glucose deprivation models of primary astrocytes and neuron cells, to explore new mechanisms and new targets underlying ischemic injury and to build the theoretical basis for further drug development.The experimental results show that primary astrocytes and neurons are successfully isolated and available in the following experiments. Oxygen-glucose deprivation models are successfully constructed by the CoCl2 and three gas incubator methods. In the oxygen-glucose deprivation models, the primary astrocytes are activated and undergo reactive proliferation and then apoptosis or death. Cell immunofluorescence stainings show that CDK5 and BAG3 are exported from nucleus to cytoplasm in primary astrocytes, while there is no significant change of CDK5 and BAG3 localization in neurons. The CDK5 kinase activity is decreased while its protein level is not changed.In conclusion, these findings suggest that the CDK5 kinase activity is decreased and BAG3 level is increased, and the pS291-BAG3 protein level is significantly decreased in the cell oxygen-glucose deprivation models. These results suggest that CDK5-induced BAG3 phosphorylation in astrocytes inhibits cells from entering into cell cycle, prevents the excessive cell proliferation and maintains the cell normal state in order to exert the normal physiological function.