CDK5 knockdown in astrocytes provide neuroprotection as a trophic source via Rac1

• Published in: Molecular and cellular neuroscience 2015-09, Vol.68, p.151-166
• Main Authors: Posada-Duque, Rafael Andrés, Palacio-Castañeda, Valentina, Cardona-Gómez, Gloria Patricia
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Astrocytes; Astrocytes - drug effects; Astrocytes - physiology; CDK5 RNAi; Cells, Cultured; Cerebral Cortex - cytology; Coculture Techniques; Cyclin-Dependent Kinase 5 - genetics; Cyclin-Dependent Kinase 5 - metabolism; Embryo, Mammalian; Excitatory Amino Acid Agonists - toxicity; Excitotoxicity; Glioma - pathology; Glutamic Acid - toxicity; Mutation - genetics; Nerve Tissue Proteins - metabolism; Neurons - drug effects; Neurons - physiology; Neuroprotection; Neuroprotection - physiology; Protein Kinase Inhibitors - pharmacology; Purines - pharmacology; Rac1; rac1 GTP-Binding Protein - metabolism; Rats; Rats, Wistar; rhoA GTP-Binding Protein - genetics; rhoA GTP-Binding Protein - metabolism; Time Factors
• ISSN: 1044-7431; 1095-9327
• DOI: 10.1016/j.mcn.2015.07.001

Astrocytes perform metabolic and structural support functions in the brain and contribute to the integrity of the blood–brain barrier. Astrocytes influence neuronal survival and prevent gliotoxicity by capturing glutamate (Glu), reactive oxygen species, and nutrients. During these processes, astrocytic morphological changes are supported by actin cytoskeleton remodeling and require the involvement of Rho GTPases, such as Rac1. The protein cyclin-dependent kinase 5 (CDK5) may have a dual effect on astrocytes because it has been shown to be involved in migration, senescence, and the dysfunction of glutamate recapture; however, its role in astrocytes remains unclear. Treating a possible deregulation of CDK5 with RNAi is a strategy that has been proposed as a therapy for neurodegenerative diseases. Models of glutamate gliotoxicity in the C6 astroglioma cell line, primary cultures of astrocytes, and co-cultures with neurons were used to analyze the effects of CDK5 RNAi in astrocytes and the role of Rac1 in neuronal viability. In C6 cells and primary astrocytes, CDK5 RNAi prevented the cell death generated by glutamate-induced gliotoxicity, and this finding was corroborated by pharmacological inhibition with roscovitine. This effect was associated with the appearance of lamellipodia, protrusions, increased cell area, stellation, Rac1 activation, BDNF release, and astrocytic protection in neurons that were exposed to glutamate excitotoxicity. Interestingly, Rac1 inhibition in astrocytes blocked BDNF upregulation and the astrocyte-mediated neuroprotection. Actin cytoskeleton remodeling and stellation may be a functional phenotype for BDNF release that promotes neuroprotection. In summary, our findings suggest that CDK5− knockdown in astrocytes acts as a trophic source for neuronal protection in a Rac1-dependent manner. •CDK5 RNAi prevents glutamate gliotoxicity.•Suppression of CDK5 promotes Rac1 activation and cell stellation.•CDK5 RNAi increases astrocyte-induced neuroprotection.•Rac1 is required for astrocyte-induced neuroprotection.