Oligomerization of CXCL10 Is Necessary for Endothelial Cell Presentation and In Vivo Activity

Abstract

The chemokine IFN-γ-inducible protein of 10 kDa (IP-10; CXCL10) plays an important role in the recruitment of activated T lymphocytes into sites of inflammation by interacting with the G protein-coupled receptor CXCR3. IP-10, like other chemokines, forms oligomers, the role of which has not yet been explored. In this study, we used a monomeric IP-10 mutant to elucidate the functional significance of oligomerization. Although monomeric IP-10 had reduced binding affinity for CXCR3 and heparin, it was able to induce in vitro chemotaxis of activated T cells with the same efficacy as wild-type IP-10. However, monomeric IP-10 was unable to induce recruitment of activated CD8+ T cells into the airways of mice after intratracheal instillation. Use of a different IP-10 mutant demonstrated that this inability was due to lack of oligomerization rather than reduced CXCR3 or heparin binding. Molecular imaging demonstrated that both wild-type and monomeric IP-10 were retained in the lung after intratracheal instillation. However, in vitro binding assays indicated that wild-type, but not monomeric, IP-10 was retained on endothelial cells and could induce transendothelial chemotaxis of activated T cells. We therefore propose that oligomerization of IP-10 is required for presentation on endothelial cells and subsequent transendothelial migration, an essential step for lymphocyte recruitment in vivo.

Altered Distribution of H60 Minor H Antigen-Specific CD8 T Cells and Attenuated Chronic Vasculopathy in Minor Histocompatibility Antigen Mismatched Heart Transplantation in Cxcr3−/− Mouse Recipients

“…It has been shown that immobilized chemokines (including IP-10 and RANTES) presented by endothelial cells are critical for haptotaxis (55,56). More recently, oligomeric but not monomeric CXCL10 presented by endothelial cells via GAG was found to be essential for effector T cell recruitment (57). In this study, retention of alloreactive CD8 T cells in the peripheral blood might represent less efficient arresting of alloreactive CD8 T cells on site of extravasation without Cxcr3.…”

The emerging role of CXCL10 in cancer (Review)

“…This unusual structural characteristic of CXCL10 provides an explanation for the ability of CXCL10 to bind to both CXCR3 and CCR3 receptors (33). Another stereotypical oligomerization of CXCL10 provides an additional source of structural diversity (3) which is essential for CXCL10 to recruit activated T cells that bind to endothelial cells and subsequently trans-migrate in vivo (34). This hypothesis was supported by Campanella et al (34), who determined that CXCL10 knockout mice lose their ability to recruit activated CD8+ T cells into their airways due to the presence of the N-methyl group disrupting the interaction of hydrogen bonds between the main chains, preventing the formation of dimers and oligomerization.…”

“…Another stereotypical oligomerization of CXCL10 provides an additional source of structural diversity (3) which is essential for CXCL10 to recruit activated T cells that bind to endothelial cells and subsequently trans-migrate in vivo (34). This hypothesis was supported by Campanella et al (34), who determined that CXCL10 knockout mice lose their ability to recruit activated CD8+ T cells into their airways due to the presence of the N-methyl group disrupting the interaction of hydrogen bonds between the main chains, preventing the formation of dimers and oligomerization. In vitro, the N-methylated Leu27 monomeric mutants were capable of inducing CXCR3 internalization and the chemotaxis of CD8+ T cells expressing CXCR3, but this induction required at least ten times higher concentrations than wild-type CXCL10; heparin and CXCR3 binding were noted, but at greatly reduced efficacy.…”

Chemokines in Wound Healing and as Potential Therapeutic Targets for Reducing Cutaneous Scarring

“…163 They help to establish a chemotactic gradient, protect chemokines from proteolytic cleavage, and have a role in oligomerization. [164][165][166][167] It has been postulated that interfering with GAG-chemokine interactions could be a potential therapeutic target, however, inherent complexities of this system has prevented significant progress. 25 While not affecting their ability to bind to their receptor(s), the truncation of the N terminus eliminates the signaling potential of many chemokines.…”