Matrix Metalloproteinase Processing of CXCL11/I-TAC Results in Loss of Chemoattractant Activity and Altered Glycosaminoglycan Binding

Abstract

The CXCR3 chemokine receptor regulates the migration of Th1 lymphocytes and responds to three ligands: CXCL9/MIG, CXCL10/IP-10, and CXCL11/I-TAC. We screened for potential regulation of T cell responses by matrix metalloproteinase (MMP) processing of these important chemokines. The most potent of the CXCR3 ligands, CXCL11, was identified by matrixassisted laser desorption ionization time-of-flight mass spectrometry as a substrate of the PMN-specific MMP-8, macrophage-specific MMP-12, and the general leukocyte MMP-9. The 73-amino acid residue CXCL11 is processed at both the amino and carboxyl termini to generate CXCL11-(5-73), -(5-63), and -(5-58) forms. NH 2 -terminal truncation results in loss of agonistic properties, as shown in calcium mobilization and chemotaxis experiments using CXCR3 transfectants and human T lymphocytes. Moreover, CXCL11-(5-73) is a CXCR3 antagonist and interestingly shows enhanced affinity to heparin. However, upon COOH-terminal truncation to position 58 there is loss of antagonist activity and heparin binding. Together this highlights an unexpected site for receptor interaction and that the carboxyl terminus is critical for glycosaminoglycan binding, an essential function for the formation of chemokine gradients in vivo. Hence, MMP activity might regulate CXCL11 tissue gradients in two ways. First, the potential of CXCL11-(5-73) to compete active CXCL11 from glycosaminoglycans might lead to the formation of an antagonistic haptotactic chemokine gradient. Second, upon further truncation, MMPs disperse the CXCL11 gradients in a novel way by proteolytic loss of a COOH-terminal GAG binding site. Hence, these results reveal potential new roles in down-regulating Th1 lymphocyte chemoattraction through MMP processing of CXCL11.Chemokines are a superfamily of low molecular weight chemotactic cytokines that function in directing the migration of leukocytes and other cell types in a multitude of processes including development, lymphocyte homing, inflammation, and wound repair (1). Chemokines form haptotactic gradients in vivo through associations with proteoglycan glycosaminoglycans (2). Upon interaction with 7-transmembrane G proteincoupled receptors, chemokines induce a chemotactic response. The expression and secretion of inducible chemokines is stimulated during infection or injury to promote rapid and efficient inflammatory and immune responses. Conversely, dampening of inflammation, a critical event in allowing tissue repair to continue unimpeded and in preventing excessive tissue damage and autoimmunity, is known to involve coordinated down-regulation of chemokine expression (3), receptor internalization (4), scavenger receptors (5), and proteolytic mechanisms of inactivation and conversion to antagonists (6).Specific and limited proteolysis, termed processing (7), of chemokines results in altered bioactivity with functional consequences such as increased or decreased receptor binding (8), conversion of an agonist to an antagonist (6, 9), shedding of membrane-anchored chemokines (10, 11),...

Evidence for an antagonist form of the chemokine CXCL10 in patients chronically infected with HCV

“…In addition, several chemokines are substrates for MMPs. Regarding CXCL10, it may be cleaved at its C-terminus by MMP9 and MMP12 (18,33); however, the cleavage product produced remains an agonist for CXCR3 (18). One important and biologically relevant unknown is the action of MMP2 on CXCL10.…”

Evidence for Immune Cell Involvement in Decidual Spiral Arteriole Remodeling in Early Human Pregnancy

“…40 MMP-2 and Ϫ9 also alter chemokine bioactivity, thereby influencing leukocyte migration. [41][42][43] In this way they could potentially mediate tight regulation of leukocyte trafficking during vascular remodeling. Furthermore, recent work by ourselves and others demonstrates that EVTs migrate in response to chemokines.…”

The extracellular matrix in myocardial injury, repair, and remodeling

“…MMPs regulate inflammatory responses through proteolytic processing of cytokines, chemokines, and growth factors (20)(21)(22)(23)(24) or by degrading glycosaminoglycan binding sites, thus interfering with a molecular step that is critical for chemokine immobilization on the endothelial cell surface and subsequent interaction with leukocytes (25). MMPs also have intracellular targets, degrading cardiomyocyte proteins, such as myosin, α-actinin, and titin (26)(27)(28).…”