Animal Science Cell and Molecular Biology LDL cholesterol question LDL cholester
ID: 226279 • Letter: A
Question
Animal Science Cell and Molecular Biology
LDL cholesterol question
LDL cholesterol (the "bad" cholesterol) binds to the scavenger receptor LDLR. It is then removed from the blood and prevented from causing atherosclerosis via endocytosis of the LDLR and degradation of the LDL in the lysosomes inside the cell. Endocytosis of LDLR is controlled by NXPY motifs in its cytoplasmic tail. (i) What does the NXPY motif in the LDLR normally bind to that allows the LDLR and its bound LDL to be endocytosed? (ii) What happens to the LDL cholesterol levels in the blood in a person heterozygous for the Y807C mutation in the NXPY motif? (iii) How is this linked to the development of high blood pressure?Explanation / Answer
i) NXPY motif in LDLR binds to clathtrin coated pits so that LDLR-LDL complex gets internalized .
2) Their blood LDL levels will be higher than those carrying two copies of wild type allele, but lower than those carrying two copies of mutant allele.
3) This mutation prevents the internalization of LDLR resulting increase of LDL concentration in blood. This is called Hypercholesterolemia. Hypercholesterolemia leads to high blood pressure by increasing sodium retention. Cholesterol accumulation in kidney cells increases retention of sodium, which in turn increase blood volume. Increase in blood volume increases blood pressure. In addition, higher blood pressure increases deposition of LDLs into the artery wall.