title: BIG1, a brefeldin A-inhibited guanine nucleotide-exchange protein modulates ATP-binding cassette transporter A-1 trafficking and function.
abstract: OBJECTIVE
  Cell-surface localization and intracellular trafficking are essential for the function of ATP-binding cassette transporter A-1 (ABCA1). However, regulation of these activities is still largely unknown. Brefeldin A, an uncompetitive inhibitor of brefeldin A-inhibited guanine nucleotide-exchange proteins (BIGs), disturbs the intracellular distribution of ABCA1, and thus inhibits cholesterol efflux. This study aimed to define the possible roles of BIGs in regulating ABCA1 trafficking and cholesterol efflux, and further to explore the potential mechanism.
  
  
  RESULTS
  By vesicle immunoprecipitation, we found that BIG1 was associated with ABCA1 in vesicles preparation from rat liver. BIG1 depletion reduced surface ABCA1 on HepG2 cells, and inhibited by 60% cholesterol release. In contrast, BIG1 overexpression increased surface ABCA1 and cholesterol secretion. With partial restoration of BIG1 through overexpression in BIG1-depleted cells, surface ABCA1 was also restored. Biotinylation and glutathione cleavage revealed that BIG1 small interfering RNA dramatically decreased the internalization and recycling of ABCA1. This novel function of BIG1 was dependent on the guanine nucleotide-exchange activity and achieved through activation of ADP-ribosylation factor 1.
  
  
  CONCLUSIONS
  BIG1, through its ability to activate ADP-ribosylation factor 1, regulates cell-surface levels and function of ABCA1, indicating a transcription-independent mechanism for controlling ABCA1 action.
authors.affiliation: Laboratory of Pharmacology and Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, No. 132, East Wai-Huan Rd, College Town, Guangzhou 510006, PR China.
authors.forename: Sisi
authors.initials: S
authors.lastname: Lin
authors.forename: Chun
authors.initials: C
authors.lastname: Zhou
authors.forename: Edward
authors.initials: E
authors.lastname: Neufeld
authors.forename: Yu-Hua
authors.initials: YH
authors.lastname: Wang
authors.forename: Suo-Wen
authors.initials: SW
authors.lastname: Xu
authors.forename: Liang
authors.initials: L
authors.lastname: Lu
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Zhi-Ping
authors.initials: ZP
authors.lastname: Liu
authors.forename: Dong
authors.initials: D
authors.lastname: Li
authors.forename: Cuixian
authors.initials: C
authors.lastname: Li
authors.forename: Shaorui
authors.initials: S
authors.lastname: Chen
authors.forename: Kang
authors.initials: K
authors.lastname: Le
authors.forename: Heqing
authors.initials: H
authors.lastname: Huang
authors.forename: Peiqing
authors.initials: P
authors.lastname: Liu
authors.forename: Joel
authors.initials: J
authors.lastname: Moss
authors.forename: Martha
authors.initials: M
authors.lastname: Vaughan
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Shen
mesh_terms: D020823:ADP-Ribosylation Factor 1 / Q000378:metabolism; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism; D019921:Biotinylation; D002462:Cell Membrane / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D056945:Hep G2 Cells; D006801:Humans; D047468:Immunoprecipitation; D008077:Lipoproteins, LDL / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D021381:Protein Transport; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014162:Transfection
chemical_list: C577836:ABCA1 protein, human; C505693:APOA1 protein, human; C119087:ARFGEF1 protein, human; C578854:ARFGEF1 protein, rat; C119088:ARFGEF2 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D016632:Apolipoprotein A-I; D020662:Guanine Nucleotide Exchange Factors; D008077:Lipoproteins, LDL; C099252:oxidized low density lipoprotein; D002784:Cholesterol; D020823:ADP-Ribosylation Factor 1; D005978:Glutathione