TY - JOUR
T1 - Functional dissection of an AP-2 β2 appendage-binding sequence within the autosomal recessive hypercholesterolemia protein
AU - Mishra, Sanjay K.
AU - Keyel, Peter A.
AU - Edeling, Melissa A.
AU - Dupin, Amie L.
AU - Owen, David J.
AU - Traub, Linton M.
PY - 2005/5/13
Y1 - 2005/5/13
N2 - The autosomal recessive hypercholesterolemia (ARH) protein plays a critical role in regulating plasma low density lipoprotein (LDL) levels. Inherited defects in ARH lead to a hypercholesterolemia that closely phenocopies that caused by a defective LDL receptor. The elevated serum LDL-cholesterol levels typical of ARH patients and the pronounced accumulation of the LDL receptor at the cell surface of hepatocytes in ARH-null mice argue that ARH operates by promoting the internalization of the LDL receptor within clathrin-coated vesicles. ARH contains an amino-terminal phosphotyrosine-binding domain that associates physically with the LDL receptor internalization sequence and with phosphoinositides. The carbosyl-terminal half of ARH contains a clathrin-binding sequence and a separate AP-2 adaptor binding region providing a plausible mechanism for how ARH can act as an endocytic adaptor or CLASP (clathrin-associated sorting protein) to couple LDL receptors with the clathrin machinery. Because the interaction with AP-2 is highly selective for the independently folded appendage domain of the β2 subunit, we have characterized the ARH β2 appendage-binding sequence in detail. Unlike the known α appendage-binding motifs, ARH requires an extensive sequence tract to bind the β appendage with comparably high affinity. A minimal 16-residue sequence functions autonomously and depends upon ARH residues Asp253, Phe259, Leu262, and Arg266. We suggested that biased β subunit engagement by ARH and the only other β2 appendage selective adaptor, β-arrestin, promotes efficient incorporation of this mechanistically distinct subset of CLASPs into clathrin-coated buds.
AB - The autosomal recessive hypercholesterolemia (ARH) protein plays a critical role in regulating plasma low density lipoprotein (LDL) levels. Inherited defects in ARH lead to a hypercholesterolemia that closely phenocopies that caused by a defective LDL receptor. The elevated serum LDL-cholesterol levels typical of ARH patients and the pronounced accumulation of the LDL receptor at the cell surface of hepatocytes in ARH-null mice argue that ARH operates by promoting the internalization of the LDL receptor within clathrin-coated vesicles. ARH contains an amino-terminal phosphotyrosine-binding domain that associates physically with the LDL receptor internalization sequence and with phosphoinositides. The carbosyl-terminal half of ARH contains a clathrin-binding sequence and a separate AP-2 adaptor binding region providing a plausible mechanism for how ARH can act as an endocytic adaptor or CLASP (clathrin-associated sorting protein) to couple LDL receptors with the clathrin machinery. Because the interaction with AP-2 is highly selective for the independently folded appendage domain of the β2 subunit, we have characterized the ARH β2 appendage-binding sequence in detail. Unlike the known α appendage-binding motifs, ARH requires an extensive sequence tract to bind the β appendage with comparably high affinity. A minimal 16-residue sequence functions autonomously and depends upon ARH residues Asp253, Phe259, Leu262, and Arg266. We suggested that biased β subunit engagement by ARH and the only other β2 appendage selective adaptor, β-arrestin, promotes efficient incorporation of this mechanistically distinct subset of CLASPs into clathrin-coated buds.
UR - http://www.scopus.com/inward/record.url?scp=20544472067&partnerID=8YFLogxK
U2 - 10.1074/jbc.M501029200
DO - 10.1074/jbc.M501029200
M3 - Article
C2 - 15728179
AN - SCOPUS:20544472067
VL - 280
SP - 19270
EP - 19280
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 19
ER -