Calreticulin-dimerization Induced by Post-translational Arginylationis is Critical for Stress Granules Scaffolding

MARCOS A. CARPIO; MARÍA B. DECCA; CECILIA LOPEZ SAMBROOKS; EDITH S. DURAND; GUILLERMO G. MONTICH; MARTA E. HALLAK

INTERNATIONAL JOURNAL OF BIOCHEMISTRY AND CELLULAR BIOLOGY

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2013 vol. 45 p. 1223 - 1235

1357-2725

Protein arginylation mediated by arginyl-tRNA protein transferase is a post-translational modificationthat occurs widely in biology, it has been shown to regulate protein and properties and functions. Post-translational arginylation is critical for embryogenesis, cardiovascular development and angiogenesisbut the molecular effects of proteins arginylated in vivo are largely unknown. In the present study, wedemonstrate that arginylation reduces CRT (calreticulin) thermostability and induces a greater degree ofdimerization and oligomerization. R-CRT (arginylated calreticulin) forms disulfide-bridged dimers thatare increased in low Ca2+conditions at physiological temperatures, a similar condition to the cellularenvironment that it required for arginylation of CRT. Moreover, R-CRT self-oligomerizes through non-covalent interactions that are enhanced at temperatures above 40◦C, condition that mimics the heat shocktreatment where R-CRT is the only isoespecies of CRT that associates in cells to SGs (stress granules). Weshow that in cells lacking CRT the scaffolding of larger SGs is impaired; the transfection with CRT (henceR-CRT expression) restores SGs assembly whereas the transfection with CRT mutated in Cys146 doesnot. Thus, R-CRT disulfide-bridged dimers (through Cys146) are essential for the scaffolding of larger SGsunder heat shock, although these dimers are not required for R-CRT association to SGs. The alteration inSGs assembly is critical for the normal cellular recover of cells after heat induced stress.We conclude that R-CRT is emerging as a novel protein that has an impact on the regulation of SGsscaffolding and cell survival.