Calpain mediates activation of p19INK4d in response to genotoxic stress

OGARA M.F.; SONZOGNI S. V.; CÁNEPA, E.T.

San Miguel de Tucumán

Congreso; XLV REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN EN BIOQUÍMICA Y BIOLOGÍA MOLECULAR (SAIB); 2009

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

p19INK4d, a member of the INK4 family, stimulates DNA repairand reduces apoptosis in cells exposed to a variety of genotoxicagents. We have demonstrated that, in neuronal cells, the p19 gene isinduced and the protein is phosphorylated in a CDK5-dependentmanner in the presence of beta-amyloid peptide.The beta-amyloidpeptide causes an increase in intracellular Ca2+ levels, activating thecalpain protease, with in turn stimulates CDK5 activity. Therefore,Ca2+-signaling could be involved in the induction andphosphorylation of p19. The aim of this work is to determine themechanism that activates p19 and allows it to execute its protectiverole in neurons. The experiments were carried out in differentiatedSH-SY5Y, Neuro-2A and HN9 cells and in cultures of hippocampalneurons. Treatment with beta-amyloid peptide, a Ca2+ ionophore orneocarzinostatin caused an upregulation of p19 mRNA level andphosphorylation of the protein. However, not only p19 proteinlevels did not increase, but in some cases they were reducedfollowing these treatments. Our hypothesis is that p19 wouldbecome cleaved and degraded by Ca2+-activated calpain. Additionof calpeptin, a calpain-specific inhibitor, reduced p19phosphorylation and prevented the increase in CDK5 activity inresponse to all genotoxic drugs. These results suggest that calpaincould be involved in the activation of p19 following genotoxic stress