Functional divergence between 2 chemokines is conferred by single amino acid change

Abstract

CXCL4 and CXCL4L1 are 2 closely related CXC chemokines that exhibit potent antiangiogenic activity. Because interactions with glycosaminoglycans play a crucial role in chemokines activity, we determined the binding parameters of CXCL4 and CXCL4L1 for heparin, heparan sulfate, and chondroitin sulfate B. We further demonstrated that the Leu67/His67 substitution is critical for the decrease in glycan binding of CXCL4L1 but also for the increase of its angiostatic activities. Using a set of mutants, we show that glycan affinity and angiostatic properties are not completely related. These data are reinforced using a monoclonal antibody that specifically recognizes structural modifications in CXCL4L1 due to the presence of His67 and that blocks its biologic activity. In vivo, half-life and diffusibility of CXCL4L1 compared with CXCL4 is strongly increased. As opposed to CXCL4L1, CXCL4 is preferentially retained at its site of expression. These findings establish that, despite small differences in the primary structure, CXCL4L1 is highly distinct from CXCL4.

Dual Roles for CXCL4 Chemokines and CXCR3 in Angiogenesis and Invasion of Pancreatic Cancer

“…CXCL4L1 and CXCL4 exhibit only 34% differences in the amino terminus encoding the signal sequence and 4.3% difference in the mature protein. CXCL4L1 has been shown to be more potent than CXCL4 at inhibiting cell proliferation and migration (2,3). Furthermore, inhibition of tumor development was observed in tumors derived from implantation of A549, LLC, and B16 cells in mice, treated with recombinant CXCL4L1 (1).…”

“…In addition, the secretion and processing mechanisms of CXCL4L1 and CXCL4 are different (4). However, both chemokines are secreted with similar efficiency (3). CXCL4L1 has much lower glycanbinding affinity and better diffusibility in vitro and in vivo (3).…”

“…CXCL4L1 has much lower glycanbinding affinity and better diffusibility in vitro and in vivo (3). These differences are caused by single amino acid changes, which confer a unique structure to the molecule (3,5). CXCL4L1 is not only expressed in the platelet megakaryocytic lineage but also in immune cells and in other cell types as well, such as smooth muscle cells and endothelial cells (4).…”

Alternative C-Terminal Helix Orientation Alters Chemokine Function

“…CXCL4 secreted from stimulated platelet exhibits a wide range of functions such regulation of hematopoiesis (19) and atherosclerosis (20 -22), antiangiogenesis (22)(23)(24)(25), chemotaxis (10,17), thrombocytopenia (26,27), anti-microbial activity (28,29), and inhibition of HIV-1 infection (30,31). G-protein-coupled receptors and cell surface glycosaminoglycans (GAGs) (14,32,33) are implicated in the aforementioned functions.…”

PF4V1 (Platelet Factor 4 Variant 1)

“…CXCL4 exerts its action through many different mechanisms, including binding to GAG and heteromultimerisation with other chemokines and growth factors, whereas in the case of CXCL4L1 its distorted structure and unique protruding Cterminal helix are assumed to conflict with this mode of action. The open formation characteristic of CXCL4L1 decreases GAG-binding, however simultaneously enhancing anti-angiogenic and antitumoral effects (Dubrac et al, 2010;Kuo et al, 2013). Additionally, CXCL4L1 forms more stable homodimers due to a loss in positive charge.…”