Biology subjects

Ugarova, T. P.

Publications and source records attributed to Ugarova, T. P..

4 recordsLinked to original sources

bioRxiv2023

PLATELET FACTOR 4 (PF4) IMPROVES SURVIVAL IN A MURINE MODEL OF ANTIBIOTIC-SUSCEPTIBLE AND METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS PERITONITIS

The complement receptor CR3, also known as integrin Mac-1 (CD11b/CD18), is one of the major phagocytic receptors on the surface of neutrophils and macrophages. We previously demonstrated that in its protein ligands, Mac-1 binds sequences enriched in basic and hydrophobic residues and strongly disfavors negatively charged sequences. The avoidance by Mac-1 of negatively charged surfaces suggests that the bacterial wall and bacterial capsule possessing net negative electrostatic charge may repel Mac-1 and that the cationic Mac-1 ligands can overcome this evasion by acting as opsonins. Indeed, we previously showed that opsonization of Gram-negative Escherichia coli with several cationic peptides, including PF4 (Platelet Factor 4), strongly augmented phagocytosis by macrophages. Here, we investigated the effect of recombinant PF4 (rPF4) on phagocytosis of Gram-positive Staphylococcus aureus in vitro and examined its impact in a mouse model of S. aureus peritonitis. Characterization of the interaction of rPF4 with nonencapsulated and encapsulated S. aureus showed that rPF4 localizes on the bacterial surface, thus making it available for Mac-1. Furthermore, rPF4 did not have direct bactericidal and bacteriostatic activity and was not toxic to host cells. rPF4 enhanced phagocytosis of S. aureus bioparticles by various primary and cultured Mac-1-expressing leukocytes by several folds. It also increased phagocytosis of live nonencapsulated and encapsulated bacteria. Notably, the augmentation of phagocytosis by rPF4 did not compromise the intracellular killing of S. aureus by macrophages. Using a murine S. aureus peritonitis model, we showed that treatment of infected mice with rPF4 caused a significant increase in the clearance of antibiotic-susceptible S. aureus and its methicillin-resistant (MRSA) variant and markedly improved survival. These findings indicate that rPF4 binding to the bacterial surface circumvents its antiphagocytic properties, improving host defense against antibiotic-susceptible and antibiotic-resistant bacteria.

cell biology↗

bioRxiv2022

THE ASSOCIATION OF CD47 WITH INTEGRIN Mac-1 REGULATES MACROPHAGE RESPONSES BY STABILIZING THE EXTENDED INTEGRIN CONFORMATION

CD47 is a ubiquitously expressed cell surface integrin-associated protein. Recently, we have demonstrated that integrin Mac-1 (M{beta}2, CD11b/CD18, CR3), the major adhesion receptor on the surface of myeloid cells, can be coprecipitated with CD47. However, the molecular basis for the CD47-Mac-1 interaction and its functional consequences remain unclear. Here, we demonstrated that CD47 regulates macrophage functions directly interacting with Mac-1. In particular, adhesion, spreading, migration, phagocytosis, and fusion of CD47-deficient macrophages were significantly decreased. The functional link between CD47 and Mac-1 was validated by co-immunoprecipitation analysis using various Mac-1-expressing cells. In HEK293 cells expressing individual M and {beta}2 integrin subunits, CD47 has been found to bind both subunits. Interestingly, the amount of CD47 recovered with the free {beta}2 subunit was higher than in the complex with the whole integrin. Furthermore, activating Mac-1-expressing HEK293 cells with PMA, Mn2+, and activating antibody increased CD47 in complex with Mac-1, suggesting greater stability of the complex with integrin in the extended conformation. Notably, on the surface of cells lacking CD47, fewer Mac-1 molecules could convert into an extended conformation in response to activation. The binding site in CD47 for Mac-1 was identified in its constituent IgV domain. The complementary binding sites for CD47 in Mac-1 were localized in integrin epidermal growth factor-like domains 3 and 4 of the {beta}2 and calf-1 and calf-2 domains of the subunits. These results indicate that Mac-1 forms a lateral complex with CD47, which regulates essential macrophage functions by stabilizing the extended integrin conformation.

cell biology↗

bioRxiv2021

FIBRIN POLYMER ON THE SURFACE OF BIOMATERIAL IMPLANTS DRIVES THE FOREIGN BODY REACTION

ABSTRACTImplantation of biomaterials and medical devices in the body triggers the foreign body reaction (FBR) which is characterized by macrophage fusion at the implant surface leading to the formation of foreign body giant cells and the development of the fibrous capsule enveloping the implant. While adhesion of macrophages to the surface is an essential step in macrophage fusion and implanted biomaterials are known to rapidly acquire a layer of host proteins, a biological substrate that is responsible for this process in vivo is unknown. Here we show that mice with genetically-imposed fibrinogen deficiency display a dramatic reduction of macrophage fusion on implanted biomaterials and are protected from the formation of fibrin-containing granulation tissue, a precursor of the fibrous capsule. Furthermore, macrophage fusion on biomaterials implanted in FibAEK mice that express a mutated form of fibrinogen incapable of thrombin-mediated polymerization was strongly reduced. Surprisingly, despite the lack of fibrin, the capsule was formed in FibAEK mice, although it had a different composition and distinct mechanical properties than that in wild-type mice. Specifically, while mononuclear -SMA-expressing macrophages embedded in the capsule of both strains of mice secreted collagen, the amount of collagen and its density in the tissue of FibAEK mice was reduced. These data identify fibrin polymer as a key biological substrate driving the development of the FBR.

immunology↗

bioRxiv2020

TRANSITION OF PODOSOMES INTO ZIPPER-LIKE STRUCTURES INMACROPHAGE-DERIVED MULTINUCLEATED GIANT CELLS

Macrophage fusion resulting in the formation of multinucleated giant cells (MGCs) is a multistage process that requires many adhesion-dependent steps and involves the rearrangement of the actin cytoskeleton. The diversity of actin-based structures and their role in macrophage fusion is poorly understood. In this study, we revealed hitherto unrecognized actin-based zipper-like structures (ZLSs) that arise between MGCs formed on the surface of implanted biomaterials. We established an in vitro model for the induction of these structures in mouse macrophages undergoing IL-4- mediated fusion. Using this model, we show that over time MGCs develop cell-cell contacts containing ZLSs. Live-cell imaging using macrophages isolated from mRFP- or GFP-Lifeact mice demonstrated that ZLSs are dynamic formations undergoing continuous assembly and disassembly and that podosomes are precursors of these structures. Immunostaining experiments showed that vinculin, talin, integrin M{beta}2, and other components of podosomes are present in ZLSs. Macrophages deficient in WASp or Cdc42, two key molecules involved in actin core organization in podosomes, as well as cells treated with the inhibitors of the Arp2/3 complex failed to form ZLSs. Furthermore, E-cadherin and nectin-2 were found between adjoining membranes, suggesting that the transition of podosomes into ZLSs is induced by bridging plasma membranes by junctional proteins.

cell biology↗