Membrane changes in lipopolysaccharide-stimulated murine B lymphocytes associated with cell activation.
The lateral diffusion of the fluorescent lipid analog 3,3'-dioctadecylindocarbocyanine iodide (DiI) was measured in the membranes of murine B lymphocytes treated with the B cell mitogen lipopolysaccharide (LPS). The mobility of DiI, as measured by fluorescence photobleaching recovery (FPR) techniques, was temperature-dependent with a value of 6.1.10(-9) cm2 s-1 at 37 degrees C. Untreated cells exhibited this diffusion coefficient over 72 h in culture. In contrast, DiI mobility decreased to 2.0.10(-9) cm2 s-1 at 37 degrees C in membranes of LPS-stimulated lymphocytes 24 h following LPS exposure. Interestingly, this decreased lipid lateral diffusion was not accompanied by any change in surface immunoglobulin lateral diffusion which remained essentially unchanged at 3.6-4.3.10(-11) cm2 s-1 over 72 h. To determine whether LPS effects on lipid lateral diffusion were due to insertion of LPS into the cell plasma membrane, we examined TRITC-LPS diffusion in B lymphocytes from LPS-responsive Balb/c and C3Heb/FeJ mice and from hypo-responsive C3H/HeJ mice. DiI and TRITC-LPS mobility decreased more than 50% in LPS-stimulated Balb/c and C3Heb/FeJ cells by 72 h. On C3H/HeJ lymphocytes, there was no change in DiI or TRITC-LPS lateral diffusion throughout the incubation period. These data indicate that B lymphocyte membrane composition is altered in LPS-activated lymphoblasts and that the decreased lateral diffusion of lipid probes does not result from membrane perturbation by LPS insertion into the lipid bilayer. Further, similarities between TRITC-LPS and DiI lateral diffusion suggest that most LPS molecules interact non-specifically with B cell membranes, presumably by acyl chain insertion of the lipid A moiety.
Department of Chemistry, Colorado State University, Ft. Collins 80523.
J A
JA
Printen
S L
SL
Woodard
J R
JR
Herman
D A
DA
Roess
B G
BG
Barisas
D000818:Animals; D001402:B-Lymphocytes / Q000737:chemistry* / Q000187:drug effects; D002232:Carbocyanines / Q000737:chemistry; D002462:Cell Membrane / Q000737:chemistry*; D005260:Female; D008070:Lipopolysaccharides; D008213:Lymphocyte Activation; D008560:Membrane Fluidity; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D012235:Rhodamines; D013696:Temperature
D002232:Carbocyanines; D008070:Lipopolysaccharides; D012235:Rhodamines; C024286:3,3'-dioctadecylindocarbocyanine; C009434:tetramethylrhodamine isothiocyanate