title: Activation of p38 MAP kinase and JNK but not ERK is required for erythropoietin-induced erythroid differentiation.
abstract: p38 MAP kinase (p38) and JNK have been described as playing a critical role in the response to a variety of environmental stresses and proinflammatory cytokines. It was recently reported that hematopoietic cytokines activate not only classical MAP kinases (ERK), but also p38 and JNK. However, the physiological function of these kinases in hematopoiesis remains obscure. We found that all MAP kinases examined, ERK1, ERK2, p38, JNK1, and JNK2, were rapidly and transiently activated by erythropoietin (Epo) stimulation in SKT6 cells, which can be induced to differentiate into hemoglobinized cells in response to Epo. Furthermore, p38-specific inhibitor SB203580 but not MEK-specific inhibitor PD98059 significantly suppressed Epo-induced differentiation and antisense oligonucleotides of p38, JNK1, and JNK2, but neither ERK1 nor ERK2 clearly inhibited Epo-induced hemoglobinization. However, in Epo-dependent FD-EPO cells, inhibition of either ERKs, p38, or JNKs suppressed cell growth. Furthermore, forced expression of a gain-of-function MKK6 mutant, which specifically activated p38, induced hemoglobinization of SKT6 cells without Epo. These results indicate that activation of p38 and JNKs but not of ERKs is required for Epo-induced erythroid differentiation of SKT6 cells, whereas all of these kinases are involved in Epo-induced mitogenesis of FD-EPO cells.
authors.affiliation: Tsukuba Life Science Center, The Institute of Physical and Chemical Research (RIKEN), Ibaraki, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Nagata
authors.forename: N
authors.initials: N
authors.lastname: Takahashi
authors.forename: R J
authors.initials: RJ
authors.lastname: Davis
authors.forename: K
authors.initials: K
authors.lastname: Todokoro
mesh_terms: D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism* / Q000502:physiology; D002454:Cell Differentiation; D004789:Enzyme Activation; D004912:Erythrocytes / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D004921:Erythropoietin / Q000502:physiology*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D004915:Leukemia, Erythroblastic, Acute; D051379:Mice; D048056:Mitogen-Activated Protein Kinase 9; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D006454:Hemoglobins; D004921:Erythropoietin; D011494:Protein Kinases; D048056:Mitogen-Activated Protein Kinase 9; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases