SEQUENTIAL ERK PHOSPHORYLATION IN TYROSINE AND THREONINE DETERMINES ITS CELLULAR DISTRIBUTION

RICARDO GELPI; CECILIA PODEROSO; KATIA E. HELFENBERGER; CRISTINA PAZ; NERINA VILLALBA; JUAN JOSÉ PODEROSO

Córdoba

Congreso; LII Reunión Anual de la Sociedad Argentina de Bioquímica y Biología Molecular; 2016

SAIB

The canonical ERK1/2 cascade is stimulated upon the binding of growth factors to their receptors; then MEK phosphorylates ERK at threonine (pThr) and tyrosine (pTyr) residues. pThr183 and pTyr185 fully activate ERK2 (2pERK) which translocates to the nucleus. Reactive oxygen species,such as H2O2, control ERK oxidation state and function. Low H2O2 (1μM) promotes cell proliferation while high H2O2 (50μM) arrests the cell cycle, a consequence of differential ERK translocation to the mitochondria and the nucleus, inLP07 lung tumor cells. The aim of this work is to study mechanisms involved in ERK intracellular traffic under different redox conditions in LP07 cells. Low oxidant status prompts a fast cytosolic pTyr185 and a later appearance in mitochondria, seen by immunoblot against pTyr. 2pERK transiently augments in mitochondria with a decrease at 60 min of H2O2 treatment to shuttle to the nucleus, promoting cell proliferation. In contrast, at high oxidative conditions, 2pERK accumulates in mitochondria with little passage to the nucleus. We showed by confocal microscopy that the ERK2 mutant Y185A (Tyr replaced by Ala) does not overlap with mitochondria but T183A (Thr by Ala) accumulates in the organelle, meaning that pThr183 is needed for ERK to leave mitochondria. These results suggest that under proliferative redox conditions, pTyr185 allows ERK to interact with mitochondria achieving pThr183to drive ERK to the nucleus.