Inserm U895, Team 2: Cell Death Differentiation and Cancer, Nice, France.
Autophagy. 2009 Nov;5(8):1092-8. doi: 10.4161/auto.5.8.9889. Epub 2009 Nov 24.
Autophagy is a highly conserved catabolic process for the elimination and recycling of organelles and macromolecules, characterized by the formation of double-membrane vesicles called autophagosomes. To date, the function of autophagy in cell differentiation is poorly documented. Here, we investigated the possibility that megakaryocytic differentiation of the Chronic Myelogenous Leukemia (CML) cell line K562, a process known to be accompanied by accumulation of vacuoles inside the cells, might involve autophagy. Using various complementary approaches, we show that the combination of the phorbol ester PMA and the p38(MAPK) inhibitor SB202190 (SB), which engaged a majority of K562 cells towards the megakaryocytic lineage, also triggered vacuolization and autophagy. The combination of PMA + SB appears to induce both increase in autophagic fluxes and an autophagic degradation blockage. Induction of autophagy was accompanied also by increased expression of Beclin 1 and p62/SQSTM1 and was found to precede the onset of megakaryocytic differentiation. Moreover, knockdown of LC3 and Beclin 1 by specific siRNAs impaired PMA + SB-mediated vacuolization, LC3-II accumulation and megakaryocytic differentiation, as well. To the best of our knowledge, this is the first description that induction of autophagy is involved in megakaryocytic differentiation of K562 CML cells.
自噬是一种高度保守的溶酶体途径，通过形成双层膜囊泡自噬体来实现细胞内成分的降解与回收。自噬在细胞分化中的作用目前知之甚少。本研究旨在探讨慢性髓系白血病（CML）细胞株 K562 的巨核细胞分化过程是否与自噬有关。众所周知，该过程伴随着细胞内空泡的积累。我们采用多种互补方法，证明 PMA 和 p38（MAPK）抑制剂 SB202190（SB）联合诱导大多数 K562 细胞向巨核细胞系分化，同时触发了空泡化和自噬。PMA+SB 联合处理似乎增加了自噬流并导致自噬降解受阻。自噬的诱导伴随着 Beclin 1 和 p62/SQSTM1 表达的增加，并先于巨核细胞分化的发生。此外，特异性 siRNAs 敲低 LC3 和 Beclin 1 可损害 PMA+SB 介导的空泡化、LC3-II 积累和巨核细胞分化。据我们所知，这是首次描述自噬的诱导参与了 K562 CML 细胞的巨核细胞分化。
