Role of Protein Tyrosine Phosphatase Non-Receptor Type 7 in the Regulation of TNF-α Production in RAW 264.7 Macrophages

Huiyun Seo,Do Hee Lee,Sayeon Cho,Sung Goo Park,In-Seon Lee,Byoung Chul Park,Jae Eun Park,Irving Coy Allen

doi:10.1371/journal.pone.0078776

Abstract

Protein tyrosine phosphatases play key roles in a diverse range of cellular processes such as differentiation, cell proliferation, apoptosis, immunological signaling, and cytoskeletal function. Protein tyrosine phosphatase non-receptor type 7 (PTPN7), a member of the phosphatase family, specifically inactivates mitogen-activated protein kinases (MAPKs). Here, we report that PTPN7 acts as a regulator of pro-inflammatory TNF-α production in RAW 264.7 cells that are stimulated with lipopolysaccharide (LPS) that acts as an endotoxin and elicits strong immune responses in animals. Stimulation of RAW 264.7 cells with LPS leads to a transient decrease in the levels of PTPN7 mRNA and protein. The overexpression of PTPN7 inhibits LPS-stimulated production of TNF-α. In addition, small interfering RNA (siRNA) analysis showed that knock-down of PTPN7 in RAW 264.7 cells increased TNF-α production. PTPN7 has a negative regulatory function to extracellular signal regulated kinase 1/2 (ERK1/2) and p38 that increase LPS-induced TNF-α production in macrophages. Thus, our data presents PTPN7 as a negative regulator of TNF-α expression and the inflammatory response in macrophages.

Highlights

Protein phosphorylation is a critical event in signal transduction, which regulates fundamental cellular processes such as differentiation, cell proliferation, apoptosis, immunological signaling, and cytoskeletal function [1]
Signaling pathways in innate immune cells are rapidly activated by phosphorylation, inducing a pro-inflammatory cytokine response to LPS of gram-negative bacteria, and are downregulated by the dephosphorylation of signaling components, suggesting that phosphatases are involved in the regulation of inflammation
Using real-time-polymerase chain reaction (PCR), we further examined the kinetics of Protein tyrosine phosphatase non-receptor type 7 (PTPN7) mRNA suppression upon exposure to LPS

Summary

Introduction

Protein phosphorylation is a critical event in signal transduction, which regulates fundamental cellular processes such as differentiation, cell proliferation, apoptosis, immunological signaling, and cytoskeletal function [1]. MAPKs like p38, JNK, and ERK have been shown to target this ARE to increase TNF-a expression in response to LPS stimulation [9]. We show that PTPN7 expression changes upon stimulation with LPS and that PTPN7 regulates TNF-a production in RAW 264.7 cells.

Results

Conclusion