ARGINYLATION OF CRT REGULATES PROTEIN FATE OUTSIDE DE ER.

LÓPEZ SAMBROOKS, CECILIA; GOITEA, VICTOE E.; CARPIO, MARCOS; HALLAK, MARTA

Washington DC

Congreso; ANNUAL MEETING SOCIETY FOR NEUROSCIENCE 2011; 2011

Post-translational modifications of proteins are significant for the regulation of cell functions; one of these is post-translational arginylation. In the present study (using fibroblasts and neuronal cultures) we demonstrated that a pool of calreticulin (CRT) undergoes retrotranslocation from the ER to the cytosol, because in CRT-knockout cells transfected with full-length CRT (that is expressed and processed solely in the ER); CRT appears arginylated in the cytoplasm. Furthermore in neurons treated with several stressors that lead to a reduction of cytosolic Ca2+ levels, (after 20 min application) the arginylated form of CRT (R-CRT) associates with stress granules (SGs).  However, in the presence of stressors that do not change Ca2+ levels, R-CRT is not recruited in the SGs despite the fact that they are formed, demonstrating the Ca2+-dependence of R-CRT association to SGs. Moreover using different apoptotic inducers (after 2 hours treatment), cells lacking of arginyl-tRNA protein transferase are more resistant to apoptosis than the WT cells. In cells that express CRT-EYFP and R-CRT-EYFP incubated in the presence MG132 (a proteosomal inhibitor) there is an accumulation of R-CRT. Moreover in these treated cells with MG132, CRT shows an increased rate of degradation with respect to R-CRT. Thus, these results indicate that protein arginylation participates in cell survival and suggest that post-translational arginylation of CRT regulates protein fate and its function outside the ER.