Reduction of AHSP synthesis in hemin-induced K562 cells and EPO-induced CD34(+) cells leads to alpha-globin precipitation, impairment of normal hemoglobin production, and increased cell death

Autor(es)

Pinho, Flavia Oliveira ; Albuquerque, Dulcineia Martins de ; Saad, Sara Teresinha Olalla ; Costa, Fernando Ferreira ^[4]

• Tipo de documento: Artigo Científico
• Fonte: Experimental Hematology; v. 36, n. 3, p. 265-272, Mar. 2008.
• Área do conhecimento: Ciências da Saúde - Medicina
• Assunto(s): Morte celular Apoptose Proteínas sanguíneas Globinas beta Células eritroides Eritropoese

Resumo

alpha-Hemoglobin stabilizing protein (AHSP) binds alpha-hemoglobin (Hb), avoiding its precipitation and its pro-oxidant activity. In the presence of beta Hb, the alpha Hb-AHSP complex is dismembered and beta Hb displaces AHSP to generate the quaternary structure of Hb. The relationship between Hb formation and alterations in AHSP expression, which may affect human erythropoiesis, has not yet been described in human cells. Hence, in this study, we examined the effects of AHSP knockdown in hemin-induced K562 and erythropoietin-induced CD34(+) cells with particular reference to cellular aspects and gene expression. Short-hairpin RNA expression vectors aimed at the AHSP mRNA target sequence were cloned and transfected into K562 and CD34(+) cells. K562 and CD34(+) cells were stimulated to erythroid differentiation. Cells were examined in terms of gene expression using quantitative real-time polymerase chain reaction; reactive oxygen species (ROS) production, apoptosis, and Hb production through flow cytometry assays; and immunofluorescence assays for globin chains. RNA interference-mediated knockdown of AHSP expression resulted in considerable alpha Hb precipitation, as well as in a significant decrease in HbF formation. AHSP-knockdown cells demonstrated an increased ROS production and increased rate of apoptosis. These findings strengthen the hypothesis that AHSP stabilizes the alpha Hb chain, avoiding its precipitation and its ability to generate ROS, which implicate in cell death. Moreover, data indicate that AHSP may be highly significant for human hemoglobin formation and suggest that AHSP is a key chaperone protein during human erythropoiesis. (AU)

• Processo FAPESP: 02/13801-7 - Alterações hereditárias das hemoglobinas: genética molecular, aspectos da evolução clínica e produção de animais transgênicos
• Beneficiário: Fernando Ferreira Costa
• Modalidade de apoio: Auxílio à Pesquisa - Temático