Cell-specific constraints to the lateral diffusion of a membrane glycoprotein.
We have previously shown that the lateral diffusion, D, of the class I Major Histocompatibility Complex (MHC) glycoprotein H-2Ld is constrained by its glycosylation, when expressed in mouse L-cells. Removal of one or more of the 3 N-linked oligosaccharides of H-2Ld glycoproteins results in an increase in D. In order to further examine the influence of glycosylation on D, we compared lateral diffusion of H-2Ld expressed in wild-type CHO cells with lateral diffusion of the same molecule expressed in mutant CHO cells with aberrant surface glycosylation. In addition, we compared lateral diffusion of wild-type and unglycosylated H-2Ld antigens in these cells. In contrast to the large effect of glycosylation state on lateral diffusion of H-2Ld in mouse L-cells, there was little effect of glycosylation on lateral diffusion of H-2Ld in any of the CHO cells. This, together with similar results on hamster class I antigens, indicates that the constraints to D of H-2Ld and other class I MHC molecules are different in CHO cells than in L-cells. Measurements of lateral diffusion after treatment of cells with cytochalasin D make it clear that interactions between MHC class I molecules and a cytoskeleton are important in reducing the mobile fraction of diffusing molecules, R, though they cannot be shown to directly affect the diffusion coefficient, D.
Barbour
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Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218.
Edidin
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D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D015638:Cytochalasin D / Q000494:pharmacology; D004058:Diffusion; D015870:Gene Expression; D005805:Genes, MHC Class I; D006031:Glycosylation; D006681:HLA-D Antigens / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D009928:Organ Specificity; D010641:Phenotype; D011233:Precipitin Tests; D011973:Receptors, LDL / Q000378:metabolism; D012995:Solubility
D006681:HLA-D Antigens; D008562:Membrane Glycoproteins; D011973:Receptors, LDL; D015638:Cytochalasin D