Complex glycans are readily accessible on the endothelium and on cell and plasma components. They interact with glycan-binding proteins which translate their structure into function. Advanced ...analytical tools are available to investigate their structure and functional interactions. Modifications to glycan structures which alter their capacity to bind proteins are particularly relevant in atherosclerosis. We summarize the regulatory role of glycans and their binding partners in the development of the disease. Given their complexity, accessibility, and important functional role, glycans and glycan-binding proteins represent promising diagnostic tools and therapeutic targets.
Chemokines and galectins are simultaneously upregulated and mediate leukocyte recruitment during inflammation. Until now, these effector molecules have been considered to function independently. ...Here, we tested the hypothesis that they form molecular hybrids. By systematically screening chemokines for their ability to bind galectin‐1 and galectin‐3, we identified several interacting pairs, such as CXCL12 and galectin‐3. Based on NMR and MD studies of the CXCL12/galectin‐3 heterodimer, we identified contact sites between CXCL12 β‐strand 1 and Gal‐3 F‐face residues. Mutagenesis of galectin‐3 residues involved in heterodimer formation resulted in reduced binding to CXCL12, enabling testing of functional activity comparatively. Galectin‐3, but not its mutants, inhibited CXCL12‐induced chemotaxis of leukocytes and their recruitment into the mouse peritoneum. Moreover, galectin‐3 attenuated CXCL12‐stimulated signaling via its receptor CXCR4 in a ternary complex with the chemokine and receptor, consistent with our structural model. This first report of heterodimerization between chemokines and galectins reveals a new type of interaction between inflammatory mediators that can underlie a novel immunoregulatory mechanism in inflammation. Thus, further exploration of the chemokine/galectin interactome is warranted.
Synopsis
Chemokines and galectins are simultaneously upregulated during inflammation and mediate leukocyte recruitment. A systematic screen now demonstrates their physical interaction as heterodimers, identifying several novel interacting pairs.
Chemokines and galectins can engage in cross talk by pairing, as exemplified by galectin‐3 and CXCL12.
The association of CXCL12 with galectin‐3 appears to have potential for modulating chemokine activity.
Galectin‐3 inhibits CXCL12‐induced chemotaxis of leukocytes and their recruitment to inflammation sites.
Galectin‐3 attenuates CXCL12‐stimulated signaling via its receptor CXCR4 in a ternary complex.
Chemokines and galectins are simultaneously upregulated during inflammation and mediate leukocyte recruitment. A systematic screen now demonstrates their physical interaction as heterodimers, identifying several novel interacting pairs.
Chemokines orchestrate leukocyte trafficking and function in health and disease. Heterophilic interactions between chemokines in a given microenvironment may amplify, inhibit, or modulate their ...activity; however, a systematic evaluation of the chemokine interactome has not been performed. We used immunoligand blotting and surface plasmon resonance to obtain a comprehensive map of chemokine-chemokine interactions and to confirm their specificity. Structure-function analyses revealed that chemokine activity can be enhanced by CC-type heterodimers but inhibited by CXC-type heterodimers. Functional synergism was achieved through receptor heteromerization induced by CCL5-CCL17 or receptor retention at the cell surface via auxiliary proteoglycan binding of CCL5-CXCL4. In contrast, inhibitory activity relied on conformational changes (in CXCL12), affecting receptor signaling. Obligate CC-type heterodimers showed high efficacy and potency and drove acute lung injury and atherosclerosis, processes abrogated by specific CCL5-derived peptide inhibitors or knock-in of an interaction-deficient CXCL4 variant. Atheroprotective effects of CCL17 deficiency were phenocopied by a CCL5-derived peptide disrupting CCL5-CCL17 heterodimers, whereas a CCL5 α-helix peptide mimicked inhibitory effects on CXCL12-driven platelet aggregation. Thus, formation of specific chemokine heterodimers differentially dictates functional activity and can be exploited for therapeutic targeting.
Protein–protein interactions (PPIs) govern most processes in living cells. Current drug development strategies are aimed at disrupting or stabilizing PPIs, which require a thorough understanding of ...PPI mechanisms. Examples of such PPIs are heteromeric chemokine interactions that are potentially involved in pathological disorders such as cancer, atherosclerosis, and HIV. It remains unclear whether this functional modulation is mediated by heterodimer formation or by the additive effects of mixed chemokines on their respective receptors. To address this issue, we report the synthesis of a covalent RANTES‐PF4 heterodimer (termed OPRAH) by total chemical synthesis and oxime ligation, with an acceleration of the final ligation step driven by PPIs between RANTES and PF4. Compared to mixed separate chemokines, OPRAH exhibited increased biological activity, thus providing evidence that physical formation of the heterodimer indeed mediates enhanced function.
Kissing chemokines: Heteromeric chemokine interactions are implicated in various inflammatory diseases. Because it is unclear whether pathological effects are caused by heterodimerization or by additive effects of separate chemokines, a covalent oxime‐linked chemokine heterodimer was synthesized. Oxime ligation was accelerated by interactions between the chemokines, and the heterodimer showed enhanced function compared to mixed chemokines.
Protein–protein interactions (PPIs) govern most processes in living cells. Current drug development strategies are aimed at disrupting or stabilizing PPIs, which require a thorough understanding of ...PPI mechanisms. Examples of such PPIs are heteromeric chemokine interactions that are potentially involved in pathological disorders such as cancer, atherosclerosis, and HIV. It remains unclear whether this functional modulation is mediated by heterodimer formation or by the additive effects of mixed chemokines on their respective receptors. To address this issue, we report the synthesis of a covalent RANTES‐PF4 heterodimer (termed OPRAH) by total chemical synthesis and oxime ligation, with an acceleration of the final ligation step driven by PPIs between RANTES and PF4. Compared to mixed separate chemokines, OPRAH exhibited increased biological activity, thus providing evidence that physical formation of the heterodimer indeed mediates enhanced function.
Heteromere Chemokin‐Wechselwirkungen werden im Zusammenhang verschiedener Entzündungskrankheiten diskutiert. Da unklar ist, ob pathologische Wirkungen von der Heterodimerisierung oder von additiven Effekten separater Chemokine ausgehen, wurde ein Chemokin‐Heterodimer mit kovalenter Oxim‐Bindung synthetisiert. Die Oximligation wird durch Wechselwirkungen zwischen den Chemokinen beschleunigt, und das Heterodimer war wirksamer als Chemokin‐Mischungen.
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