Protein tyrosine phosphatase non-receptor Type 2 regulates IFN-γ-induced cytokine signaling in THP-1 monocytes.
BACKGROUND
We have previously shown that the Crohn's disease (CD)-associated gene protein tyrosine phosphatase non-receptor Type 2 (PTPN2) regulates interferon gamma (IFN-γ)-induced signaling and barrier function in intestinal epithelial cells. Overactivation of immature immune cells has been demonstrated in CD and elevated levels of proinflammatory cytokines, such as IFN-γ, play an important pathophysiological role in this disease. Here we studied the role of PTPN2 in the regulation of IFN-γ-induced signaling in THP-1 monocytic cells.


METHODS
Protein analysis was performed by Western blotting, PTPN2 knockdown was induced by siRNA, and cytokine levels were measured by enzyme-linked immunosorbent assay (ELISA).


RESULTS
We demonstrated that IFN-γ (1000 U/mL) treatment of THP-1 cells elevates PTPN2 protein, reaching a peak by 24 hours. Increased PTPN2 expression, in turn, correlated with decreased activity of the signaling molecules, signal transducer and activator of transcription (STAT) 1 and STAT3. Loss of PTPN2 potentiated IFN-γ-induced phosphorylation of both of the STATs and of the mitogen-activated protein kinase (MAPK) family member, p38. However, PTPN2 loss did not affect the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 or c-Jun N-terminal kinase. As a functional consequence, PTPN2 knockdown elevated the IFN-γ-induced secretion of the proinflammatory cytokines interleukin-6 (IL-6) and macrophage chemoattractant protein 1 (MCP-1).


CONCLUSIONS
Our data demonstrate that IFN-γ enhances PTPN2 protein in THP-1 cells and loss of PTPN2 promotes IFN-γ-induced STAT signaling and secretion of IL-6 and MCP-1. Therefore, we show that PTPN2 regulates inflammation-related events and PTPN2 dysregulation may contribute to the onset as well as to the perpetuation of inflammatory events associated with CD.
Scharl
Michael
M
Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, California, USA.
Hruz
Petr
P
McCole
Declan F
DF
D015153:Blotting, Western; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2 / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D011994:Recombinant Proteins; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction
D016207:Cytokines; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D050796:STAT3 Transcription Factor; D007371:Interferon-gamma; D020928:Mitogen-Activated Protein Kinases; C516649:PTPN2 protein, human; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2