title: Lateral mobility of individual integrin nanoclusters orchestrates the onset for leukocyte adhesion.
abstract: Integrins are cell membrane adhesion receptors involved in morphogenesis, immunity, tissue healing, and metastasis. A central, yet unresolved question regarding the function of integrins is how these receptors regulate both their conformation and dynamic nanoscale organization on the membrane to generate adhesion-competent microclusters upon ligand binding. Here we exploit the high spatial (nanometer) accuracy and temporal resolution of single-dye tracking to dissect the relationship between conformational state, lateral mobility, and microclustering of the integrin receptor lymphocyte function-associated antigen 1 (LFA-1) expressed on immune cells. We recently showed that in quiescent monocytes, LFA-1 preorganizes in nanoclusters proximal to nanoscale raft components. We now show that these nanoclusters are primarily mobile on the cell surface with a small (ca. 5%) subset of conformational-active LFA-1 nanoclusters preanchored to the cytoskeleton. Lateral mobility resulted crucial for the formation of microclusters upon ligand binding and for stable adhesion under shear flow. Activation of high-affinity LFA-1 by extracellular Ca(2+) resulted in an eightfold increase on the percentage of immobile nanoclusters and cytoskeleton anchorage. Although having the ability to bind to their ligands, these active nanoclusters failed to support firm adhesion in static and low shear-flow conditions because mobility and clustering capacity were highly compromised. Altogether, our work demonstrates an intricate coupling between conformation and lateral diffusion of LFA-1 and further underscores the crucial role of mobility for the onset of LFA-1 mediated leukocyte adhesion.
authors.affiliation: BioNanophotonics group, Institute for Bioengineering of Catalonia and Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Baldiri Reixac 15-21, 08028 Barcelona, Spain.
authors.forename: Gert Jan
authors.initials: GJ
authors.lastname: Bakker
authors.forename: Christina
authors.initials: C
authors.lastname: Eich
authors.forename: Juan A
authors.initials: JA
authors.lastname: Torreno-Pina
authors.forename: Ruth
authors.initials: R
authors.lastname: Diez-Ahedo
authors.forename: Gemma
authors.initials: G
authors.lastname: Perez-Samper
authors.forename: Thomas S
authors.initials: TS
authors.lastname: van Zanten
authors.forename: Carl G
authors.initials: CG
authors.lastname: Figdor
authors.forename: Alessandra
authors.initials: A
authors.lastname: Cambi
authors.forename: Maria F
authors.initials: MF
authors.lastname: Garcia-Parajo
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002448:Cell Adhesion; D002460:Cell Line; D002465:Cell Movement; D016000:Cluster Analysis; D004058:Diffusion; D005110:Extracellular Space / Q000378:metabolism; D006801:Humans; D016169:Lymphocyte Function-Associated Antigen-1 / Q000737:chemistry / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology* / Q000378:metabolism*; D053758:Nanoparticles / Q000737:chemistry*; D021381:Protein Transport; D012212:Rheology; D013314:Stress, Mechanical
chemical_list: D016169:Lymphocyte Function-Associated Antigen-1; D002118:Calcium