Membranal cholesterol is not required for L-selectin adhesiveness in primary lymphocytes but controls a chemokine-induced destabilization of L-selectin rolling adhesions

J Immunol. 2007 Jul 15;179(2):1030-8. doi: 10.4049/jimmunol.179.2.1030.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Cell Adhesion / physiology*
  • Chemokine CXCL12
  • Chemokine CXCL13
  • Chemokines / immunology
  • Chemokines / metabolism*
  • Chemokines, CXC / immunology
  • Chemokines, CXC / metabolism
  • Cholesterol / immunology
  • Cholesterol / metabolism*
  • Flow Cytometry
  • Fluorescent Antibody Technique
  • Humans
  • L-Selectin / immunology
  • L-Selectin / metabolism*
  • Leukocyte Rolling / physiology*
  • Lymphocytes / chemistry
  • Lymphocytes / immunology
  • Lymphocytes / metabolism
  • Membrane Microdomains / immunology
  • Membrane Microdomains / metabolism*
  • Membrane Proteins / immunology
  • Membrane Proteins / metabolism
  • Microscopy, Fluorescence

Substances

  • Actins
  • CXCL12 protein, human
  • CXCL13 protein, human
  • Chemokine CXCL12
  • Chemokine CXCL13
  • Chemokines
  • Chemokines, CXC
  • Membrane Proteins
  • L-Selectin
  • Cholesterol