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Updated: May 12, 2026
Highly Efficient Transfection of Human THP-1 Macrophages by Nucleofection
Published on: September 2, 2014
Macrophage fusion is controlled by the cytoplasmic protein tyrosine phosphatase PTP-PEST/PTPN12
Inmoo Rhee1, Dominique Davidson, Cleiton Martins Souza
1Laboratory of Molecular Oncology, Clinical Research Institute of Montréal, Montréal, Québec, Canada.
Abstract:
Macrophages 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 β-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.
Insights
Protein tyrosine phosphatase PTP-PEST is essential for macrophage fusion into multinucleated giant cells and osteoclasts. It regulates cell polarization and migration by controlling Pyk2 and paxillin phosphorylation.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Macrophages are immune cells capable of cell-cell fusion, forming multinucleated giant cells and osteoclasts.
- This fusion process is crucial for pathogen clearance, foreign body removal, and extracellular matrix remodeling.
- The precise molecular mechanisms regulating macrophage fusion remain incompletely understood.
Purpose of the Study:
- To investigate the role of cytoplasmic protein tyrosine phosphatase PTP-PEST (PTPN12) in macrophage fusion.
- To determine if PTP-PEST is required for the formation of multinucleated giant cells and osteoclasts.
- To elucidate the molecular pathways through which PTP-PEST influences macrophage fusion.
Main Methods:
- Utilized a macrophage-targeted PTP-PEST-deficient mouse model.
- Performed in vitro studies using RAW264.7 macrophage cell line.
- Assessed macrophage differentiation, cytokine production, and fusion in response to stimuli like interleukin-4 and RANKL.
- Analyzed the expression of fusion mediators and key signaling proteins (Pyk2, paxillin).
Main Results:
- PTP-PEST is dispensable for macrophage differentiation and cytokine production.
- PTP-PEST is essential for interleukin-4-induced multinucleated giant cell formation in vitro.
- PTP-PEST is required for in vivo macrophage fusion around foreign bodies and RANKL-induced osteoclastogenesis.
- PTP-PEST deficiency leads to hyperphosphorylation of Pyk2 and paxillin, impacting cell polarization, migration, and spreading.
Conclusions:
- Macrophage fusion into multinucleated giant cells and osteoclasts is critically dependent on PTP-PEST.
- PTP-PEST regulates macrophage fusion by controlling the phosphorylation of Pyk2 and paxillin.
- These signaling events are vital for macrophage polarization, migration, and spreading, which are key for fusion competence.
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