Role of G proteins and ERK activation in hemin-induced erythroid differentiation of K562 cells

Department of Biophysics, Marmara University, İstanbul, Istanbul, Turkey
Life Sciences (Impact Factor: 2.7). 03/2006; 78(11):1217-24. DOI: 10.1016/j.lfs.2005.06.041
Source: PubMed


Heterotrimeric G proteins which couple extracellular signals to intracellular effectors play a central role in cell growth and differentiation. The pluripotent erythroleukemic cell line K562 that acquires the capability to synthesize hemoglobin in response to a variety of agents can be used as a model system for erythroid differentiation. Using Western blot analysis and RT-PCR, we studied alterations in G protein expression accompanying hemin-induced differentiation of K562 cells. We demonstrated the presence of G(alpha s), G(alpha i2) and G(alpha q) and the absence of G(alpha i1), G(alpha o) and G(alpha 16) in K562 cells. We observed the short form of G(alpha s) to be expressed predominantly in these cells. Treatment of K562 cells with hemin resulted in an increase in the levels of G(alpha s) and G(alpha q). On the other hand, the level of G(alpha i2) was found to increase on the third day after induction with hemin, followed by a decrease to levels lower of those of uninduced cells. The mitogen-activated protein kinase ERK1/2 pathway is crucial in the control of cell proliferation and differentiation. Both Gi- and Gq-coupled receptors stimulate MAPK activation. We therefore examined the phosphorylation of ERK1/2 during hemin-induced differentiation of K562 cells. Using anti-ERK1/2 antibodies, we observed that ERK2 was primarily phosphorylated in K562 cells. ERK2 phosphorylation increased gradually until 48 h and returned to basal values by 96 h following hemin treatment. Our results suggest that changes in G protein expression and ERK2 activity are involved in hemin-induced differentiation of K562 cells.

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Available from: Bahire Küçükkaya, Oct 11, 2015
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    • "As previously reported, G protein expression and MAPKs are involved in hemin-induced erythroid differentiation, another γ-globin stimulator [19]. Hydroxycarbamide increased phosphorylation of p38 in erythroid differentiation [18]. "
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    • "In order to stimulate hemoglobinization, K562 cells were treated with hemin, which we added to cell cultures alone or in combination with adrenergic drugs. In accordance to data in the literature [21] [22] [23], hemin induces the appearance of benzidine positive K562 cells during 72 h cultivation (image in Fig. 5D). 20 μM hemin does not significantly interfere with the growth behavior of K562 cells, but induces a slight increase of benzidine positive cells (Supplementary Information, Figs. "
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