Expression of (Pro)renin Receptor During Rapamycin-Induced Erythropoiesis in K562 Erythroleukemia Cells and Its Possible Dual Actions on Erythropoiesis

Expression of (Pro)renin Receptor During Rapamycin-Induced Erythropoiesis in K562 Erythroleukemia Cells and Its Possible Dual Actions on Erythropoiesis

KIRIKO KANEKO,^1,2 KOJI OHBA,¹ TAKUO HIROSE,³ KAZUHITO TOTSUNE,⁴ KAZUMICHI FURUYAMA² and KAZUHIRO TAKAHASHI¹

¹Department of Endocrinology and Applied Medical Science, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
²Department of Molecular Biochemistry, Iwate Medical University School of Medicine, Morioka, Iwate, Japan
³Mechanisms and therapeutic strategies of chronic kidney diseases, Institut Necker Enfants Malades (INEM)/Inserm U1151/CNRS UMR8253/Hpital Necker, Paris, France
⁴Department of Social Welfare, Faculty of Synthetic Welfare, Tohoku Fukushi University, Sendai, Miyagi, Japan

(Pro)renin receptor ((P)RR), a specific receptor for renin and prorenin, is expressed in erythroblastic cells. (P)RR has multiple biological actions: prorenin activation, stimulation of the intracellular signaling including extracellular signal-regulated kinases, and functional complex formation with vacuolar H⁺-ATPase (v-ATPase). However, the functional implication of (P)RR in erythroblast cells has not been clarified. The aim of the present study was to clarify changes of (P)RR expression during erythropoiesis and a role of (P)RR in the heme synthesis. (P)RR expression was studied during rapamycin-induced erythropoiesis in a human erythroleukemia cell line, K562. Treatment with rapamycin (100 nM) for 48 hours significantly increased %number of hemoglobin-producing cells, γ-globin mRNA levels, erythroid specific 5-aminolevulinate synthase (ALAS2) mRNA levels, and heme content in K562 cells. Both (P)RR protein and mRNA levels increased about 1.4-fold during rapamycin-induced erythropoiesis. Suppression of (P)RR expression by (P)RR-specific small interference RNA increased ALAS2 mRNA levels about 1.6-fold in K562 cells, compared to control using scramble RNA, suggesting that (P)RR may down-regulate ALAS2 expression. By contrast, treatment with bafilomycin A1, an inhibitor of v-ATPase, decreased greatly % number of hemoglobin-producing cells and heme content in K562 cells, indicating that the v-ATPase function is essential for hemoglobinization and erythropoiesis. Treatment with bafilomycin A1 increased (P)RR protein and mRNA levels. In conclusion, we propose that (P)RR has dual actions on erythropoiesis: the promotion of erythropoiesis via v-ATPase function and the down-regulation of ALAS2 mRNA expression. Thus, (P)RR may contribute to the homeostatic control of erythropoiesis.

keywords —— erythropoiesis; heme; prorenin; (pro)renin receptor; rapamycin

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Tohoku J. Exp. Med., 2017, 241, 35-43

Correspondence: Kazuhiro Takahashi, M.D., Ph.D., Department of Endocrinology and Applied Medical Science, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan.

e-mail: ktaka-md@med.tohoku.ac.jp