title: The clathrin adaptor proteins ARH, Dab2, and numb play distinct roles in Niemann-Pick C1-Like 1 versus low density lipoprotein receptor-mediated cholesterol uptake.
abstract: The uptake of circulating low density lipoproteins (LDL) is mediated by LDL receptor (LDLR) through clathrin-dependent endocytosis. At the early stage of this process, adaptor proteins ARH and Dab2 specifically bind the endocytic signal motif in LDLR and recruit clathrin/AP2 to initiate internalization. On the other hand, intestinal cholesterol is absorbed by Niemann-Pick C1-Like 1 (NPC1L1) through clathrin-dependent endocytosis. Another adaptor protein, Numb recognizes the endocytic motif in NPC1L1 C terminus and couples NPC1L1 to endocytic machinery. The ARH, Dab2, and Numb proteins contain a homogeneous phosphotyrosine binding (PTB) domain that directly binds endocytic motifs. Because ARH, Dab2, and Numb are all PTB domain family members, the emerging mystery is whether these adaptors act complementally in LDLR and NPC1L1 endocytosis. Here, we found that ARH and Dab2 did not bind NPC1L1 and were not required for NPC1L1 internalization. Similarly, Numb lacked the ability to interact with the LDLR C terminus and was dispensable for LDL uptake. Only the Numb isoforms with shorter PTB domain could facilitate NPC1L1 endocytosis. Besides the reported function in intestinal cholesterol absorption, Numb also mediated cholesterol reabsorption from bile in liver. We further identified a Numb variant with G595D substitution in humans of low blood LDL-cholesterol. The G595D substitution impaired NPC1L1 internalization and cholesterol reabsorption, due to attenuating affinity of Numb to clathrin/AP2. These results demonstrate that Numb specifically regulates NPC1L1-mediated cholesterol absorption both in human intestine and liver, distinct from ARH and Dab2, which selectively participate in LDLR-mediated LDL uptake.
authors.affiliation: From the State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031.
authors.forename: Jian
authors.initials: J
authors.lastname: Wei
authors.affiliation: the Department of Cardiovascular Medicine, First Affiliated Hospital of Xinjiang Medical University, Urumqi 830054, and.
authors.forename: Zhen-Yan
authors.initials: ZY
authors.lastname: Fu
authors.affiliation: From the State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031.
authors.forename: Pei-Shan
authors.initials: PS
authors.lastname: Li
authors.affiliation: From the State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031.
authors.forename: Hong-Hua
authors.initials: HH
authors.lastname: Miao
authors.affiliation: From the State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031.
authors.forename: Bo-Liang
authors.initials: BL
authors.lastname: Li
authors.affiliation: the Department of Cardiovascular Medicine, First Affiliated Hospital of Xinjiang Medical University, Urumqi 830054, and myt-xj@163.com.
authors.forename: Yi-Tong
authors.initials: YT
authors.lastname: Ma
authors.affiliation: From the State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, the College of Life Sciences, Wuhan University, Wuhan 430072, China blsong@whu.edu.cn.
authors.forename: Bao-Liang
authors.initials: BL
authors.lastname: Song
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D019943:Amino Acid Substitution; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D001693:Biological Transport, Active / Q000502:physiology; D045744:Cell Line, Tumor; D008078:Cholesterol, LDL / Q000235:genetics / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D020125:Mutation, Missense; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011973:Receptors, LDL / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D008078:Cholesterol, LDL; C102885:DAB2 protein, human; C573412:LDLR protein, human; C469745:LDLRAP1 protein, human; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C410800:NPC1L1 protein, human; D009419:Nerve Tissue Proteins; C113026:NUMB protein, human; D011973:Receptors, LDL; D025521:Tumor Suppressor Proteins
keywords: ARH; Cholesterol; Dab2; Endocytosis; Lipid Absorption; Lipoprotein Receptor; Low-density Lipoprotein (LDL); NPC1L1; Numb