Published under exclusive license by The American Society for Biochemistry and Molecular Biology, Inc. Macrophage fusion leading to the formation of multinucleated giant cells is a hallmark of chronic inflammation. Several membrane proteins have been implicated in mediating cell- cell attachment during fusion, but their binding partners remain unknown. Recently, we demonstrated that interleukin-4 (IL-4)- induced fusion of mouse macrophages depends on the integrin macrophage antigen 1 (Mac-1). Surprisingly, the genetic deficiency of intercellular adhesion molecule 1 (ICAM-1), an established ligand of Mac-1, did not impair macrophage fusion, suggesting the involvement of other counter-receptors. Here, using various approaches, including signal regulatory protein α (SIRPα) knockdown, recombinant proteins, adhesion and fusion assays, biolayer interferometry, and peptide libraries, we show that SIRPα, which, similar to ICAM-1, belongs to the Ig superfamily and has previously been implicated in cell fusion, interacts with Mac-1. The following results support the conclusion that SIRPα is a ligand of Mac-1: (a) recombinant ectodomain of SIRPα supports adhesion of Mac-1-expressing cells; (b) Mac-1-SIRPα interaction is mediated through the ligand-binding αMI-domain of Mac-1; (c) recognition of SIRPα by the αMIdomain conforms to general principles governing binding of Mac-1 to many of its ligands; (d) SIRPα reportedly binds CD47; however, anti-CD47 function-blocking mAb produced only a limited inhibition of macrophage adhesion to SIRPα; and (e) co-culturing of SIRPα- and Mac-1-expressing HEK293 cells resulted in the formation of multinucleated cells. Taken together, these results identify SIRPα as a counter-receptor for Mac-1 and suggest that the Mac-1-SIRPα interaction may be involved in macrophage fusion.
| Identifer | oai:union.ndltd.org:ETSU/oai:dc.etsu.edu:etsu-works-11240 |
| Date | 10 May 2019 |
| Creators | Podolnikova, Nataly P., Hlavackova, Marketa, Wu, Yifei, Yakubenko, Valentin P., Faust, James, Balabiyev, Arnat, Wang, Xu, Ugarova, Tatiana P. |
| Publisher | Digital Commons @ East Tennessee State University |
| Source Sets | East Tennessee State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | ETSU Faculty Works |
| Rights | http://creativecommons.org/licenses/by/4.0/ |
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