Beta-amyloid-mediated induction and activation of p19INK4d involves Ca2+-dependent signaling

OGARA M.F.; SIRKIN P.F.; PREGI N.; CÁNEPA, E.T.

Villa Carlos Paz

Congreso; XLIV REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN EN BIOQUÍMICA Y BIOLOGÍA MOLECULAR (SAIB); 2008

SOCIEDAD ARGENTINA DE INVESTIGACIÓN EN BIOQUÍMICA Y BIOLOGÍA MOLECULAR (SAIB)

Beta-amyloid, a key player in neurodegenerative diseases and the main component of senile plaques, acts by causing oxidative stress, lipid and protein oxidation and DNA damage. In response to genotoxic stress, p19INK4d, a member of the INK4 family of cell cycle inhibitors, becomes transcriptionally induced and phosphorylated. p19 improves DNA repair and reduces apoptosis. However, the mechanism leading to p19 induction and activation in response to beta-amyloid remains unknown. Our working hypothesis is that beta-amyloid, by increasing intracellular Ca2+ levels, activates calpains, which  convert CDK5 regulatory subunit p35 to its active form, p25. CDK5, in turn, is one of the kinases responsible for p19 phosphorylation. We used SH-SY5Y cells differentiated with retinoic acid as a neuronal model. By Northern blot and metabolic labeling with 32P, beta-amyloid treatment of both differentiated and undifferentiated cells induced the expression and phosphorylation of p19 in a dose-dependent manner, as well as the expression of p35. Similar results were obtained with A23187, a Ca2+ ionophore. Antisense downregulation of CDK5 prevented the beta-amyloid induced phosphorylation of p19. Our results show that Ca2+-dependent signaling becomes activated upon beta-amyloid treatment and appears to be involved in the induction and activation of p19INK4d.