title: Mortalin is a novel mediator of erythropoietin signaling.
abstract: Erythropoietin (EPO) stimulates erythroid growth by enhancing the proliferation, maturation and survival of late-stage erythroid progenitor cells. However, the entire process of EPO stimulation remains undetermined. To further clarify the intracellular mechanisms by which EPO affects the growth of erythroid progenitor cells, we analyzed proteins obtained from purified human erythroid colony-forming cells (ECFCs) cultured with or without EPO, and one of the proteins apparently related with EPO stimuli was identified as mortalin (mthsp70/PBP74/Grp75/mot-2), which is a member of the heat shock protein 70 family of chaperones. The amount of mortalin mRNA in ECFCs increased in an EPO dose-dependent manner, and ECFC growth was dependent on the amount of mortalin. Furthermore, expression of mortalin in ECFCs was suppressed by a phosphatidylinositol 3-kinase inhibitor. Finally, we analyzed gene expression patterns in ECFCs cultured with or without EPO after treatment with mortalin small interfering RNA (siRNA) using a DNA microarray. When ECFCs treated with mortalin siRNA were cultured with EPO, the expression of several genes overlapped with the profile seen in control ECFCs cultured without EPO. Our data suggest that mortalin is involved in the mediation of EPO signaling and plays an important role in stimulating the growth of erythroid progenitor cells.
authors.affiliation: Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Ohtsuka
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Abe
authors.forename: Tomomi
authors.initials: T
authors.lastname: Fujii
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Junji
authors.initials: J
authors.lastname: Nishimura
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Takayanagi
authors.forename: Koichiro
authors.initials: K
authors.lastname: Muta
mesh_terms: D015536:Down-Regulation; D015180:Electrophoresis, Gel, Two-Dimensional; D015672:Erythroid Precursor Cells / Q000187:drug effects / Q000378:metabolism; D004921:Erythropoietin / Q000494:pharmacology*; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D020411:Oligonucleotide Array Sequence Analysis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D015854:Up-Regulation
chemical_list: D018840:HSP70 Heat-Shock Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C080352:mortalin; D004921:Erythropoietin; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt