Ruolo della PLC?1 e della PKC? nel differenziamento miogenico

Phospholipase C (PLC) has been known to be a key effector protein in signal transduction pathway for cell proliferation and differentiation. Studies on signalling through the insulin/IGF-1 receptors in muscle differentiation have revealed that PLC?1 is involved during this process and that both mRNA and protein levels were increased during myogenesis. Based on increasing signal transduction pathways that required both PLC?1 and PKC?, we investigated its role in insulin stimulation of skeletal muscle differentiation. The precise effects of insulin on specific PKC isoforms are as yet unknown. Insulin stimulation produced a gradual increase in PKC? expression and activation of PKC? through skeletal muscle differentiation. By immunoprecipitation we have demonstrated that endogenous PLC?1 and PKC? belong to the same immunocomplex that increase during through myogenic differentiation. Furthermore, the SH domain of PLC?1 is involved in the protein complex and that its confine to the Golgi membrane. PLC?1 has been involved in cyclin D3 up-regulation. By overexpression and silencing approach we have evidenced that PKC? modulate the espression of cyclin D3; the kinase dead form of PKC? doesn't maintain the same ability. Using a reporter hGH vector we proved that PKC? acts at transcriptional level by affecting the -37 region of cyclin D3 promoter, as has been described previous for PLC?1. In summary this data proved the involvement of PKC? in the regulation of cyclin D3 expression, together with PLC?1.