Distinction in the mode of receptor-mediated endocytosis between high density lipoprotein and acetylated high density lipoprotein: evidence for high density lipoprotein receptor-mediated XXXX transfer.

@entity29947 @entity16374 @entity406 @entity1234 @entity376 @entity35 @entity165 @entity597
The interactions of high density lipoprotein (HDL) and acetylated high density lipoprotein ( @entity16374 -HDL) with isolated @entity35 sinusoidal liver cells have been investigated. Cellular binding of 125I- @entity16374 -HDL at 0 degrees C demonstrated the presence of a specific, saturable membrane-associated receptor. This receptor was affected neither by @entity406 -treated albumin nor by low density lipoprotein modified either by acetylation or @entity1234 , ligands known to undergo receptor-mediated endocytosis by the cells, indicating that the receptor for @entity16374 -HDL constitutes a distinct class among the scavenger receptors for chemically modified proteins. Parallel binding experiments using 125I-HDL also revealed the presence on these cells of a receptor for unmodified HDL. The ligand specificities of these two receptors were similar to each other except that the @entity16374 -HDL receptor was sensitive to polyanions such as dextran @entity597 and @entity29947 . Interaction of HDL with the cells at 37 degrees C was totally different from that of @entity16374 -HDL. Cellular binding of HDL was not accompanied by subsequent intracellular degradation of its apoprotein moiety, whereas its @entity165 moiety was significantly transferred to the cells. In contrast, @entity16374 -HDL was endocytosed and underwent lysosomal degradation as a holoparticle. This shift in receptor-recognition from the HDL receptor to the @entity16374 -HDL receptor was accomplished by acetylation of approximately 8% of the total @entity376 residues of HDL apoprotein. This unique difference in endocytic behavior between HDL and @entity16374 -HDL suggests a potential link of the HDL receptor to HDL-mediated @entity165 transfer in sinusoidal liver cells.
