DYNAMICS AND SELECTIVE ASOCIATION OF ARGINYLATED CALRETICULIN TO STRESS GRANULES IN CELLS

CARPIO, MARCOS A.; LOPEZ SAMBROOKS, CECÍLIA; HALLAK, MARTA

Búzios, Río de Janeiro, Brasil

Congreso; I CONGRESO IBRO/LARC DE NEUROCIENCIAS DE AMERICA LATINA, CARIBE E PENINSULA IBÉRICA; 2008

IBRO/LARC

The post-translational arginylation of proteins consists in the covalent union of arginine in acidic amino acid at the N-terminal position. We demonstrated that in-vitro and ?in vivo? calreticulin (CRT) is substratum of this modification. Arginylated calreticulin (R-CRT) showed a different subcellular localization from described for CRT within the endoplasmic reticulum. (Decca, et.al jbc 2007). We determined that the variation of the cytosolic calcium levels in neurons cells increase the levels of R-CRT, and this protein is aggregate and associated in cytoplasmatic focus called stress granules (SGs ).In this work we show that R-CRT is associated at the SGs in cells exposed to oxidative stress and heat shock. However R-CRT is not involved in SGs in cells treated with UV radiation. By measurements of intracellular calcium we observed that both oxidative stress and heat shock conditions modified the levels of intracellular calcium, while the UV radiation does not alter the calcium homeostasis in the cells.Moreover, in studies about the dynamics of these structures, measuring the reversibility of SGs we observed a different rate of disassemble between TIA-1 (SGs marker) and R-CRT when the environmental stress disappears. This effect is related to the ability of cell by to restore the calcium homeostasis in relation to the severity of the effects caused by the stress effectors. In conclusion, R-CRT participates selectively in SGs under different stress conditions. This association with SGs is dependent on the variation of the intracellular calcium levels Knowing that SGs are highly dynamic structures, which are in constant interaction between the polysome and the RNAm degradation system, and that has been described for CRT a capacity of RNAm binding, R-CRT could participate in a selective and specifies regulation of the translation of certain RNAm in different environmental stress conditions.