Localization of Rab24 in K562 human leukemic cells in both control and starvation conditions

CALLIGARIS, S.D.; FADER, C.M.; SAITTA, L.; COLOMBO, M. I.

Mar del Plata

Congreso; XLIII Reunión anual Sociedad Argentina de Investigación en Bioquímica y Biología molecular; 2007

Sociedad Argentina de Investigación en Bioquímica y Biología molecular

The Rab family of small GTPases plays an important role in the regulation of membrane trafficking along the endo/lysosomal and secretory pathways. The exact role of Rab24 is currently unknown. We have previously reported a partial colocalization of GFP-Rab24 with autophagic vacuoles in nutrient-starved CHO cells, suggesting that Rab24 may participate in macroautophagy. During the maturation of erythroid cells, autophagy of organelles such as mitochondria is necessary for erythrocyte generation. K562 human leukemic cells  have a default high level expression of LC3 (autophagy marker) and Rab 24. In order to investigate the possible role of Rab24 in K562, cells cotransfected with different GFP-chimeric proteins and labeled with fluorescent compounds were analyzed by confocal microscopy. Initially, we confirmed that the Rab24 and LC3 colocalization increases under starvation conditions. We have also observed a partial colocalization of Rab24 with Lysotracker-Red and DQ-BSA, markers of acidic and lysosomal/degradative compartments, respectively. In addition, there was a considerable colocalization with Rab7, a protein that labels late endosome/lysosomes, which is also recruited to autophagic vacuoles. In contrast, no colocalization with markers of multivesicular bodies was observed. These data suggest that in K562 cells Rab24 localizes in a compartment with autolysosomal features.