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P2X(7) receptor and polykarion formation
S Falzoni1, P Chiozzi, D Ferrari
1Department of Experimental and Diagnostic Medicine, Section of General Pathology, University of Ferrara, Ferrara, Italy.
Abstract:
Cell fusion is a central phenomenon during the immune response that leads to formation of large elements called multinucleated giant cells (MGCs) of common occurrence at sites of granulomatous inflammation. We have previously reported on the involvement in this event of a novel receptor expressed to high level by mononuclear phagocytes, the purinergic P2X(7) receptor. Herein, we show that blockade of this receptor by a specific monoclonal antibody prevents fusion in vitro. In contrast, cell fusion is stimulated by addition of enzymes that destroy extracellular ATP (i.e., apyrase or hexokinase). Experiments performed with phagocytes selected for high (P2X(7) hyper) or low (P2X(7) hypo) P2X(7) expression show that fusion only occurs between P2X(7) hyper/P2X(7) hyper and not between P2X(7) hyper/P2X(7) hypo or P2X(7) hypo/P2X(7) hypo. During MGCs formation we detected activation of caspase 3, an enzyme that is powerfully stimulated by P2X(7). Finally, we observed that during MGCs formation, the P2X(7) receptor is preferentially localized at sites of cell-to-cell contact. These findings support the hypothesis originally put forward by our group that the P2X(7) receptor participates in multinucleated giant cell formation.
Insights
The purinergic P2X(7) receptor is crucial for forming multinucleated giant cells (MGCs) during inflammation. Blocking this receptor prevents cell fusion, highlighting its role in immune responses.
Area of Science:
- Immunology
- Cell Biology
- Inflammation Research
Background:
- Cell fusion is vital in immune responses, forming multinucleated giant cells (MGCs) at inflammation sites.
- The purinergic P2X(7) receptor, highly expressed by mononuclear phagocytes, was previously implicated in this process.
Purpose of the Study:
- To investigate the role of the purinergic P2X(7) receptor in multinucleated giant cell formation.
- To determine if P2X(7) receptor blockade affects in vitro cell fusion.
Main Methods:
- Utilized a specific monoclonal antibody to block the P2X(7) receptor.
- Assessed cell fusion in phagocytes with varying P2X(7) receptor expression levels.
- Measured caspase 3 activation and P2X(7) receptor localization during MGC formation.
Main Results:
- Monoclonal antibody blockade of P2X(7) receptor prevented in vitro cell fusion.
- Enzymatic destruction of extracellular ATP stimulated fusion.
- Cell fusion occurred exclusively between phagocytes with high P2X(7) receptor expression.
- Caspase 3 activation and preferential P2X(7) receptor localization at cell contact sites were observed during MGC formation.
Conclusions:
- The P2X(7) receptor plays a significant role in multinucleated giant cell formation.
- Findings support the hypothesis that P2X(7) receptor mediates MGC development in granulomatous inflammation.