LOCALIZATION OF RAB24 IN K562 HUMAN LEUKEMIC CELLS IN BOTH CONTROL AND STARVATION CONDITIONS

CALLIGARIS SD; FADER CM, SAITTA L AND COLOMBO MI

Mar del Plata. Buenos Aires. Argentina.

Congreso; XLIII reunión anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2007

The Rab family of small GTPase plays an important role in the regulation of membrane trafficking among the endo/lysosomal an secretory pathway. The exact role or Rab24 is currently unknow. We have previouly reported the colocalization the GFP-Rab24 with autophagic vesicles in nutrient-starved CHO cells, suggesting that Rab24 may participate in macroautophagy. During the maturation of erythroid cells, autophagy of organells such as mitochondria is necessary for erythrocyte generation.K562 human leukemic cells have a default high level expression of LC3 (autophagy markers) and Rab24.In order to investigate the possible role of Rab24 in K562, cells cotransfected with different GFP-chimeric proteins and labeled with fluorescet compounds were analyzed by confocal microscopy. Initially, we confirmed that LC3 and Rab24 colocalization increases under starvation conditions.We have also observed a partial colocalization of Rab24 with lysotracker-red an DQ-BSA, markers of acidic and lysosomal/degradative compartments, respectivelly. In addition, there was a considerable colocalization with Rab7, a protein that labels late  endosomes /lysosome, which is also recruited to autophagicvacuoles. In contrast, no colocalization with markers of multivesicular bodies was observed.These data suggest that in K562 cells Rab24 localize in a compartment with autolysosomal features.