CX3CL1 homo-oligomerization drives cell-to-cell adherence

Mariano A Ostuni,Frédéric Pincet,Julie Guellec,Noëlline Guillou,Patrick Fuchs,Patricia Hermand,Olivier Lequin,Philippe Deterre,Soria Iatmanen-Harbi,Audrey Coens,Christophe Combadière,Jean-Jacques Lacapere,Elodie Desuzinges-Mandon,Claude Hattab,Emeline Saindoy,Anass Jawhari

doi:10.1038/s41598-020-65988-w

Abstract

During inflammatory response, blood leukocytes adhere to the endothelium. This process involves numerous adhesion molecules, including a transmembrane chemokine, CX3CL1, which behaves as a molecular cluster. How this cluster assembles and whether this association has a functional role remain unknown. The analysis of CX3CL1 clusters using native electrophoresis and single molecule fluorescence kinetics shows that CX3CL1 is a homo-oligomer of 3 to 7 monomers. Fluorescence recovery after photobleaching assays reveal that the CX3CL1-transmembrane domain peptide self-associates in both cellular and acellular lipid environments, while its random counterpart (i.e. peptide with the same residues in a different order) does not. This strongly indicates that CX3CL1 oligomerization is driven by its intrinsic properties. According to the molecular modeling, CX3CL1 does not associate in compact bundles but rather with monomers linearly assembled side by side. Finally, the CX3CL1 transmembrane peptide inhibits both the CX3CL1 oligomerization and the adhesive function, while its random counterpart does not. This demonstrates that CX3CL1 oligomerization is mandatory for its adhesive potency. Our results provide a new direction to control CX3CL1-dependent cellular adherence in key immune processes.

Highlights

During inflammatory response, blood leukocytes adhere to the endothelium
The CX3CL1-EYFP was immune-purified before native electrophoresis
We investigated the potential aggregation of the TM24 and SCR24 peptides by FRAP after peptide incorporation in Giant Unilamelar Vesicles (GUVs) of egg phosphatidyl choline (EggPC)

Summary

Introduction

This process involves numerous adhesion molecules, including a transmembrane chemokine, CX3CL1, which behaves as a molecular cluster. How this cluster assembles and whether this association has a functional role remain unknown. The CX3CL1 chemokine, with its unique CX3CR1 receptor[16], is involved in adherence to the endothelium of the inflammatory monocyte population (CD14hi CD16– CX3CR1+ CCR2+ in humans, Ly6Chi CX3CR1+ CCR2+ in mice)[12,17,18,19,20] likely through interaction with platelets[21,22]. Using the TM domain peptide alone, we were able to modulate the CX3CL1-CX3CR1 dependent cellular adherence, opening the way to a new class of inhibitors able to antagonize the function of the CX3CL1 membrane form without affecting the role of the CX3CL1 soluble form

Methods

Results

Conclusion