ARGINYLATED CALRETICULIN: A PRO-APOPTOTIC PROTEIN?

LOPEZ SAMBROOKS, CECILIA; CARPIO, MARCOS A.; HALLAK, MARTA E

FLORENCIA

Congreso; 8th IBRO WORLD CONGRESS OF NEUROSCIENCE; 2011

Post-translational modifications of proteins are important for the regulation of cell functions; one of these modifications is post-translational arginylation. In the present study, we demonstrated that a pool of CRT undergoes retrotranslocation from the ER to the cytosol, because in CRT-knockout cells transfected with full-length CRT, cytoplasmic CRT appears as a consequence of its expression and processing in the ER. Furthermore, R-CRT associates with SGs in neurons treated with several stressors (20 min) that lead to a reduction of intracellular Ca2+ levels. However, in the presence of stressors that do not affect Ca2+ levels, R-CRT is not recruited to these loci despite the fact that SGs are formed, demonstrating Ca2+-dependent R-CRT association to SGs in neurons. Moreover, we show by flow cytometry that cells lacking of Ate1 enzyme are significantly resistant to apoptosis compared to WT cells using different apoptostic inducers a longer treatment times (2 hours). Moreover cells that express CRT-EYFP and RCRT-EYFP were incubated in the presence of the proteasomal inhibitor MG132 and analyzed by WB, immunocytochemistry and flow cytometry. Treatment of these cells with MG132 induced the accumulation of RCRT. Moreover, CRT showed an increased rate of degradation with respect to RCRT in the presence of MG132. Thus, these results indicate that change in protein arginylation regulate protein fate and cell survival and support the idea that posttranslational arginylation of CRT seems to regulate its cytosolic function when the cells are not in exposed to environmental stress conditions.