Protein Arginine Methyltransferase 1 Interacts with and Activates p38α to Facilitate Erythroid Differentiation

Wei-Kai Hua,Yuan-I Chang,Chao-Ling Yao,Chung-Yi Chang,Shiaw-Min Hwang,Wey-Jinq Lin,Reiko Sugiura

doi:10.1371/journal.pone.0056715

Abstract

Protein arginine methylation is emerging as a pivotal posttranslational modification involved in regulating various cellular processes; however, its role in erythropoiesis is still elusive. Erythropoiesis generates circulating red blood cells which are vital for body activity. Deficiency in erythroid differentiation causes anemia which compromises the quality of life. Despite extensive studies, the molecular events regulating erythropoiesis are not fully understood. This study showed that the increase in protein arginine methyltransferase 1 (PRMT1) levels, via transfection or protein transduction, significantly promoted erythroid differentiation in the bipotent human K562 cell line as well as in human primary hematopoietic progenitor CD34+ cells. PRMT1 expression enhanced the production of hemoglobin and the erythroid surface marker glycophorin A, and also up-regulated several key transcription factors, GATA1, NF-E2 and EKLF, which are critical for lineage-specific differentiation. The shRNA-mediated knockdown of PRMT1 suppressed erythroid differentiation. The methyltransferase activity-deficient PRMT1G80R mutant failed to stimulate differentiation, indicating the requirement of arginine methylation of target proteins. Our results further showed that a specific isoform of p38 MAPK, p38α, promoted erythroid differentiation, whereas p38β did not play a role. The stimulation of erythroid differentiation by PRMT1 was diminished in p38α- but not p38β-knockdown cells. PRMT1 appeared to act upstream of p38α, since expression of p38α still promoted erythroid differentiation in PRMT1-knockdown cells, and expression of PRMT1 enhanced the activation of p38 MAPK. Importantly, we showed for the first time that PRMT1 was associated with p38α in cells by co-immunoprecipitation and that PRMT1 directly methylated p38α in in vitro methylation assays. Taken together, our findings unveil a link between PRMT1 and p38α in regulating the erythroid differentiation program and provide evidence suggesting a novel regulatory mechanism for p38α through arginine methylation.

Highlights

Circulating red blood cells are derived from hematopoietic progenitors through an intricate process of erythropoiesis which is essential for maintaining a vital physiological condition
We found in our preliminary examination that the cellular profile of protein arginine methylation significantly changed during erythroid differentiation of K562 cells
Since protein arginine methyltransferase 1 (PRMT1) is the predominant protein arginine methyltransferase, we investigated the role of PRMT1 in erythroid differentiation

Summary

Introduction

Circulating red blood cells are derived from hematopoietic progenitors through an intricate process of erythropoiesis which is essential for maintaining a vital physiological condition. Erythropoietin (EPO) is the primary cytokine regulating various stages of erythropoiesis in our body. Intracellular signaling pathways such as the JAK/STAT [3], mitogen-activated protein kinase (MAPK) [4] and PI3 kinase/Akt [5] cascades have been shown to mediate these extracellular signals. Activation of the p38 MAPK pathway contributes critically to the erythroid differentiation of leukemia cell lines induced by various agents [6,7] and of primary CD34+ hematopoietic progenitors induced by EPO [8]. Some downstream effectors of p38 MAPK, such as activating transcription factor-2 (ATF-2) and cyclic AMP response element binding protein (CREB), have been reported to participate in the induction of the c-globin gene [9], the detailed upstream regulatory events and downstream effectors of the p38 MAPK pathway during erythroid differentiation are yet to be elucidated

Methods

Results

Conclusion