KLF4 is required for suppression of histamine synthesis by polyamines during bone marrow-derived mast cell differentiation.

Kazuhiro Nishimura,Toshihiko Toida,Toshio Mizuta,Moemi Okamoto,Kazuei Igarashi,Tetsuhiko Yoshino,Rina Shibue,Toru Shibayama,Satoshi Tanaka,Teruki Murakami,Masashi Yamaguchi,Sakamuri V Reddy

doi:10.1371/journal.pone.0229744

Abstract

Mast cells have secretory granules containing chemical mediators such as histamine and play important roles in the immune system. Polyamines are essential factors for cellular processes such as gene expression and translation. It has been reported that secretory granules contain both histamine and polyamines, which have similar chemical structures and are produced from the metabolism of cationic amino acids. We investigated the effect of polyamine depletion on mast cells using bone marrow-derived mast cells (BMMCs). Polyamine depletion was induced using α-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase. DFMO treatment resulted in a significant reduction of cell number and abnormal secretory granules in BMMCs. Moreover, the cells showed a 2.3-fold increase in intracellular histamine and up-regulation of histidine decarboxylase (HDC) at the transcriptional level during BMMC differentiation. Levels of the transcription factor kruppel-like factor 4 (KLF4) greatly decreased upon DFMO treatment; however, Klf4 mRNA was expressed at levels similar to controls. We determined the translational regulation of KLF4 using reporter genes encoding Klf4-luc2 fusion mRNA, for transfecting NIH3T3 cells, and performed in vitro translation. We found that the efficiency of KLF4 synthesis in response to DFMO treatment was enhanced by the existence of a GC-rich 5'-untranslated region (5'-UTR) on Klf4 mRNA, regardless of the recognition of the initiation codon. Taken together, these results indicate that the enhancement of histamine synthesis by DFMO depends on the up-regulation of Hdc expression, achieved by removal of transcriptional suppression of KLF4, during differentiation.

Highlights

Polyamines are small basic molecules with multiple amino groups and are involved in cell proliferation and differentiation [1, 2]
To evaluate the effect of DFMO treatment during bone marrow-derived mast cells (BMMCs) differentiation, bone marrow cells were cultured in the absence or presence of 5 mM DFMO, as shown in previous reports [17, 27], all cells died before maturation
The degranulation rates of BMMCs were unaffected by DFMO treatment (Fig 1F). These results indicated that the effect of 0.1 mM DFMO treatment during BMMC differentiation was similar to that of 5 mM DFMO treatment

Summary

Introduction

Polyamines are small basic molecules with multiple amino groups and are involved in cell proliferation and differentiation [1, 2]. The term ‘polyamine modulon’, is used to describe genes encoding proteins regulated by polyamines at the translational level [7]. Mast cells are present in connective and submucosal tissues of mammals and are known to be involved in immunological processes contributing to both innate and adaptive immunity in defense against pathogens [9, 10]. They contain many secretory granules with serglycin proteoglycans (PGs) and important chemical mediators [11]. We demonstrated that KLF4 synthesis is regulated at the translational level by polyamines and is involved in histamine synthesis in mast cells

Materials and methods

Results

Discussion