Membranal cholesterol is not required for L-selectin adhesiveness in primary lymphocytes but controls a chemokine-induced destabilization of L-selectin rolling adhesions.
Cholesterol-enriched lipid microdomains regulate L-selectin signaling, but the role of membrane cholesterol in L-selectin adhesion is unclear. Arrest chemokines are a subset of endothelial chemokines that rapidly activate leukocyte integrin adhesiveness under shear flow. In the absence of integrin ligands, these chemokines destabilize L-selectin-mediated leukocyte rolling. In the present study, we investigated how cholesterol extraction from the plasma membrane of peripheral blood T or B cells affects L-selectin adhesions and their destabilization by arrest chemokines. Unlike the Jurkat T cell line, whose L-selectin-mediated adhesion is cholesterol dependent, in primary human PBLs and in murine B cells and B cell lines, cholesterol depletion did not impair any intrinsic adhesiveness of L-selectin, consistent with low selectin partitioning into lipid rafts in these cells. However, cholesterol raft disruption impaired the ability of two arrest chemokines, CXCL12 and CXCL13, but not of a third arrest chemokine, CCL21, to destabilize L-selectin-mediated rolling of T lymphocytes. Actin capping by brief incubation with cytochalasin D impaired the ability of all three chemokines to destabilize L-selectin rolling. Blocking of the actin regulatory phosphatidylinositol lipid, phosphatidylinositol 4,5-bisphosphate, did not affect chemokine-mediated destabilization of L-selectin adhesions. Collectively, our results suggest that L-selectin adhesions are inhibited by actin-associated, cholesterol-stabilized assemblies of CXCL12- and CXCL13-binding receptors on both T and B lymphocytes. Thus, the regulation of L-selectin by cholesterol-enriched microdomains varies with the cell type as well as with the identity of the destabilizing chemokine.
Dwir
Oren
O
Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.
Grabovsky
Valentin
V
Pasvolsky
Ronit
R
Manevich
Eugenia
E
Shamri
Revital
R
Gutwein
Paul
P
Feigelson
Sara W
SW
Altevogt
Peter
P
Alon
Ronen
R
D000199:Actins / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology*; D054377:Chemokine CXCL12; D054382:Chemokine CXCL13; D018925:Chemokines / Q000276:immunology / Q000378:metabolism*; D019743:Chemokines, CXC / Q000276:immunology / Q000378:metabolism; D002784:Cholesterol / Q000276:immunology / Q000378:metabolism*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D019041:L-Selectin / Q000276:immunology / Q000378:metabolism*; D036904:Leukocyte Rolling / Q000502:physiology*; D008214:Lymphocytes / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D021962:Membrane Microdomains / Q000276:immunology / Q000378:metabolism*; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism; D008856:Microscopy, Fluorescence
D000199:Actins; C515255:CXCL12 protein, human; C110663:CXCL13 protein, human; D054377:Chemokine CXCL12; D054382:Chemokine CXCL13; D018925:Chemokines; D019743:Chemokines, CXC; D008565:Membrane Proteins; D019041:L-Selectin; D002784:Cholesterol