Enhanced binding of low and high density lipoproteins to human adipocyte plasma membranes: effects of temperature and proteases.
The specific binding of 125I-labelled low density lipoprotein ([125I]LDL to human adipocyte plasma membranes was higher at 37 than at 0 degree C. Prior treatment of membranes with pronase had no effect on LDL binding measured at 0 degree C but consistently stimulated binding at 37 degrees C. Plasmin was similar to pronase in enhancing LDL-specific binding, but thrombin was not as effective. 125I-labelled high density lipoprotein ([125I]HDL2) specific binding to human adipocyte plasma membranes was similarly sensitive to temperature and pronase treatment. Addition of the protease inhibitor aprotinin in the adipocyte membrane binding assay significantly reduced [125I]LDL binding at 37 degrees C (p less than 0.05), suggesting the involvement of a protease activity intrinsic to the lipoproteins and (or) membranes. These data demonstrate that both LDL and HDL binding in human adipocyte plasma membranes can be "up-regulated" by specific proteolytic perturbations in a temperature-dependent manner.
D000273:Adipose Tissue / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005341:Fibrinolysin / Q000378:metabolism; D006801:Humans; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism*; D011402:Pronase / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D013696:Temperature; D013917:Thrombin / Q000378:metabolism
D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D011480:Protease Inhibitors; D010447:Peptide Hydrolases; D013917:Thrombin; D005341:Fibrinolysin; D011402:Pronase