Wnt-5a Promotes Neural Development and Differentiation by Regulating CDK5 via Ca2+/Calpain Pathway

Background/Aims: The Wnt signaling pathway has essential functions in the central nervous system, where it regulates the major physiological functions of neurons, including development, differentiation, and plasticity. Wnt signaling controls these cellular events; however, how Wnt pathways integrate into a coherent developmental program remains unclear. Methods: The expression and secretion of different WNT ligands (Wnt-1, Wnt-3a, Wnt-4, Wnt-5a, Wnt-11), and the levels and activities of cyclin-dependent kinases (CDK2, CDK4, CDK6/cyclin D, cyclin E) or CDK5 (CDK5/p35 and p25) were measured in Rat cortex at different embryonic stages, and in RA/BDNF-induced differentiated SH-SY5Y cell model, by Quantitative real-time PCR (qPCR), western blotting, ELISA, and in vitro CDK5 kinase assays. MAP2-BrdU double staining was used to assess cell differentiation and cell cycle exit in an RA/BDNF-induced differentiated SH-SY5Y cell model. The effects of CDK5 and Ca 2+ /calpain signaling were assessed using specific chemical inhibitors. Results: We found that Wnt-1 was unchanged and Wnt-3a was attenuated, whereas Wnt-4, Wnt-5a, and Wnt-11 were markedly up-regulated, during the development of neurons and differentiated SH-SY5Y cells. Simultaneously, the activity of CDK5 was elevated. Furthermore, we describe crosstalk between non-canonical Wnt signaling and CDK5 in the development of neurons and differentiated SH-SY5Y cells. Wnt-5a, a non-canonical Wnt ligand, regulated CDK5 via Ca 2+ /calpain signaling in both neuronal development and differentiation. Inhibition of Wnt-5a diminished CDK5 kinase activity via the Ca 2+ /calpain pathway, thereby attenuating RA-BDNF induced SH-SY5Y cell differentiation. Conclusion: Wnt-5a signaling is a significant regulator of neuronal development and differentiation and upregulates CDK5 kinase activity via Ca 2+ /calpain signaling.