title: ABCB4 exports phosphatidylcholine in a sphingomyelin-dependent manner.
abstract: ABCB4, which is specifically expressed on the canalicular membrane of hepatocytes, exports phosphatidylcholine (PC) into bile. Because SM depletion increases cellular PC content and stimulates PC and cholesterol efflux by ABCA1, a key transporter involved in generation of HDL, we predicted that SM depletion also stimulates PC efflux through ABCB4. To test this prediction, we compared the lipid efflux activity of ABCB4 and ABCA1 under SM depletion induced by two different types of inhibitors for SM synthesis, myriocin and (1R,3S)-N-(3-hydroxy-1-hydroxymethyl-3-phenylpropyl)dodecanamide, in human embryonic kidney 293 and baby hamster kidney cells. Unexpectedly, SM depletion exerted opposite effects on ABCB4 and ABCA1, suppressing PC efflux through ABCB4 while stimulating efflux through ABCA1. Both ABCB4 and ABCA1 were recovered from Triton-X-100-soluble membranes, but ABCB4 was mainly recovered from CHAPS-insoluble SM-rich membranes, whereas ABCA1 was recovered from CHAPS-soluble membranes. These results suggest that a SM-rich membrane environment is required for ABCB4 to function. ABCB4 must have evolved to exert its maximum activity in the SM-rich membrane environment of the canalicular membrane, where it transports PC as the physiological substrate.
authors.affiliation: Institute for integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Laboratory of Cellular Biochemistry, Division of Applied Life Sciences, Kyoto University Graduate School of Agriculture, Kyoto 606-8502, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Ishigami
authors.affiliation: Institute for integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Kohjiro
authors.initials: K
authors.lastname: Nagao
authors.affiliation: Department of Biochemistry & Cell Biology, National Institute of Infectious Diseases, 1-23-1, Toyama, Shinjuku-ku, Tokyo 162-8640, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Hanada
authors.affiliation: Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Nozomu
authors.initials: N
authors.lastname: Kono
authors.affiliation: Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Arai
authors.affiliation: Laboratory of Cellular Biochemistry, Division of Applied Life Sciences, Kyoto University Graduate School of Agriculture, Kyoto 606-8502, Japan.
authors.forename: Michinori
authors.initials: M
authors.lastname: Matsuo
authors.affiliation: Laboratory of Cellular Biochemistry, Division of Applied Life Sciences, Kyoto University Graduate School of Agriculture, Kyoto 606-8502, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kioka
authors.affiliation: Institute for integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8502, Japan; Laboratory of Cellular Biochemistry, Division of Applied Life Sciences, Kyoto University Graduate School of Agriculture, Kyoto 606-8502, Japan. Electronic address: uedak@kais.kyoto-u.ac.jp.
authors.forename: Kazumitsu
authors.initials: K
authors.lastname: Ueda
mesh_terms: D064286:ATP Binding Cassette Transporter 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D018435:ATP Binding Cassette Transporter, Subfamily B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D006224:Cricetinae; D057809:HEK293 Cells; D006801:Humans; D010713:Phosphatidylcholines / Q000235:genetics / Q000378:metabolism*; D013109:Sphingomyelins / Q000235:genetics / Q000378:metabolism*
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018435:ATP Binding Cassette Transporter, Subfamily B; D010713:Phosphatidylcholines; D013109:Sphingomyelins; C095122:multidrug resistance protein 3
keywords: (1R,3S)-N-(3-hydroxy-1-hydroxymethyl-3-phenylpropyl)dodecanamide; ATP binding cassette protein; ATP binding cassette transporter A1; bile acid; cholesterol; high density lipoprotein; myriosin