Calpain mediates activation of p19INK4d in response to genotoxic stress

MARÍA F. OGARA; SILVINA V. SONZOGNI; EDUARDO T. CÁNEPA

San Miguel de Tucum¨¢n

Congreso; XLV Reuni¨®n Anual de la Sociedad Argentina de Investigaci¨®n en Bioqu¨ªmica y Biolog¨ªa Molecular; 2009

Sociedad Argentina de Investigaci¨®n en Bioqu¨ªmica y Biolog¨ªa Molecular

CALPAIN MEDIATES ACTIVATION OF p19INK4d IN RESPONSE TO GENOTOXIC STRESS M. Florencia Ogara, Silvina V. Sonzogni and Eduardo T. C¨¢nepa Laboratorio de Biolog¨ªa Molecular-Depto Qu¨ªmica Biol¨®gica-FCEN-UBA-Ciudad Universitaria-Buenos Aires  p19INK4d, a member of the INK4 family, stimulates DNA repair and reduces apoptosis in cells exposed to a variety of genotoxic agents. We have demonstrated that, in neuronal cells, the p19 gene is induced and the protein is phosphorylated in a CDK5-dependent manner in the presence of ¦Â-amyloid peptide.The ¦Â-amyloid peptide causes an increase in intracellular Ca2+ levels, activating the calpain protease, with in turn stimulates CDK5 activity. Therefore, Ca2+-signaling could be involved in the induction and phosphorylation of p19. The aim of this work is to determine the mechanism that activates p19 and allows it to execute its protective role in neurons. The experiments were carried out in differentiated SH-SY5Y, Neuro-2A and HN9 cells and in cultures of hippocampal neurons. Treatment with ¦Â-amyloid peptide, a Ca2+ ionophore or neocarzinostatin caused an upregulation of p19 mRNA level and phosphorylation of the protein. However, not only did p19 protein levels not increase, but in some cases they were reduced following these treatments. Our hypothesis is that p19 would become cleaved and degraded by Ca2+-activated calpain. Addition of calpeptin, a calpain-specific inhibitor, reduced p19 phosphorylation and prevented the increase in CDK5 activity in response to all genotoxic drugs. These results suggest that calpain could be involved in the activation of p19 following genotoxic stress