Biochimica et Biophysica Acta 2014-01-01

CD1d favors MHC neighborhood, GM1 ganglioside proximity and low detergent sensitive membrane regions on the surface of B lymphocytes.

Dilip Shrestha, Mark A Exley, György Vereb, János Szöllősi, Attila Jenei

Index: Biochim. Biophys. Acta 1840(1) , 667-80, (2014)

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Abstract

Cluster of differentiation 1 (CD1) represents a family of proteins which is involved in lipid-based antigen presentation. Primarily, antigen presenting cells, like B cells, express CD1 proteins. Here, we examined the cell-surface distribution of CD1d, a subtype of CD1 receptors, on B lymphocytes.Fluorescence labeling methods, including fluorescence resonance energy transfer (FRET),were employed to investigate plasma membrane features of CD1d receptors.High FRET efficiency was observed between CD1d and MHC I heavy chain (MHC I-HC), β2-microglobulin(β2m) and MHC II proteins in the plasma membrane. In addition, overexpression of CD1d reduced the expression of MHC II and increased the expression of MHC I-HC and β2m proteins on the cell-surface. Surprisingly, β2m dependent CD1d isoform constituted only ~15% of the total membrane CD1d proteins. Treatment of B cells with methyl-β-cyclodextrin (MβCD) / simvastatin caused protein rearrangement; however, FRET demonstrated only minimal effect of these chemicals on the association between CD1d and GM1 ganglioside on cell-surface.Likewise, a modest effect was only observed in a co-culture assay between MβCD/simvastatin treated C1R–CD1d cells and invariant natural killer T cells on measuring secreted cytokines (IFNγ and IL4). Furthermore,CD1d rich regions were highly sensitive to low concentration of Triton X-100. Physical proximity between CD1d, MHC and GM1 molecules was also detected in the plasma membrane.An intricate relationship between CD1d, MHC, and lipid species was found on the membrane of human B cells.Organization of CD1d on the plasma membrane might be critical for its biological functions.