Macrophage Fusion Is Controlled by the Cytoplasmic Protein Tyrosine Phosphatase PTP-PEST/PTPN12

Abstract

dMacrophages can undergo cell-cell fusion, leading to the formation of multinucleated giant cells and osteoclasts. This process is believed to promote the proteolytic activity of macrophages toward pathogens, foreign bodies, and extracellular matrices. Here, we examined the role of PTP-PEST (PTPN12), a cytoplasmic protein tyrosine phosphatase, in macrophage fusion. Using a macrophage-targeted PTP-PEST-deficient mouse, we determined that PTP-PEST was not needed for macrophage differentiation or cytokine production. However, it was necessary for interleukin-4-induced macrophage fusion into multinucleated giant cells in vitro. It was also needed for macrophage fusion following implantation of a foreign body in vivo. Moreover, in the RAW264.7 macrophage cell line, PTP-PEST was required for receptor activator of nuclear factor kappa-B ligand (RANKL)-triggered macrophage fusion into osteoclasts. PTP-PEST had no impact on expression of fusion mediators such as ␤-integrins, E-cadherin, and CD47, which enable macrophages to become fusion competent. However, it was needed for polarization of macrophages, migration induced by the chemokine CC chemokine ligand 2 (CCL2), and integrin-induced spreading, three key events in the fusion process. PTP-PEST deficiency resulted in specific hyperphosphorylation of the protein tyrosine kinase Pyk2 and the adaptor paxillin. Moreover, a fusion defect was induced upon treatment of normal macrophages with a Pyk2 inhibitor. Together, these data argue that macrophage fusion is critically dependent on PTP-PEST. This function is seemingly due to the ability of PTP-PEST to control phosphorylation of Pyk2 and paxillin, thereby regulating cell polarization, migration, and spreading.

Transposon mutagenesis identifies genes and cellular processes driving epithelial-mesenchymal transition in hepatocellular carcinoma

“…PTPN12 tyrosine phosphatase was originally identified in a genetic screen for tumor suppressors in triple-negative breast cancers, where it inhibits multiple oncogenic tyrosine kinases, including HER2 and EGFR (49). In addition, studies of Ptpn12-deficient mice have shown that Ptpn12 regulates the migration of endothelial cells, dendritic cells, and macrophages, probably through dephosphorylation of Prk2, FAK, Cas, and paxillin (50)(51)(52). These antimigratory functions of PTPN12 also have been observed in several types of human cancers, including breast, ovary, and prostate cancers (53)(54)(55).…”

PSTPIP2, a Protein Associated with Autoinflammatory Disease, Interacts with Inhibitory Enzymes SHIP1 and Csk

“…2C). Mice deficient in PEP or PTP-PEST do not develop typical signs of autoinflammatory disorder (43)(44)(45)(46), and thus it seems that the major functions of these PTPs are not related to their binding to PSTPIP2. However, if there is a redundancy among the PEST-PTPs that are associated with PSTPIP2, single family member deficiencies would probably not reveal any relevant phenotype.…”

Control of Dendritic Cell Migration, T Cell-Dependent Immunity, and Autoimmunity by Protein Tyrosine Phosphatase PTPN12 Expressed in Dendritic Cells

“…Cell purity was Ͼ90% (data not shown). Bone marrow-derived macrophages were produced as described elsewhere (13).…”

“…Data acquisition was done on a BD BioSciences FACSCalibur cytometer using CellQuest software (BD BioSciences), and data were analyzed using the FlowJo software program (Trees Star Inc., Ashland, OH). Rabbit antibodies against PTPN12, Pyk2, Csk, signal regulatory protein alpha (SIRP␣), proline-serine-threonine phosphatase-interacting protein 1 (PSTPIP-1), and Syk have been described (7,13,16,17). Antiphosphotyrosine monoclonal antibody (MAb) 4G10 was purchased from Millipore (Billerica, CA).…”

“…PTPN12 is also critical for secondary T cell activation responses as a result of the capacity to promote adhesion between activated T cells (7). Moreover, it is essential for fusion of macrophages into multinucleated giant cells and osteoclasts (13). Last, there is evidence that PTPN12 is a tumor suppressor (12).…”