title: ABCB19/PGP19 stabilises PIN1 in membrane microdomains in Arabidopsis.
abstract: Auxin transport is mediated at the cellular level by three independent mechanisms that are characterised by the PIN-formed (PIN), P-glycoprotein (ABCB/PGP) and AUX/LAX transport proteins. The PIN and ABCB transport proteins, best represented by PIN1 and ABCB19 (PGP19), have been shown to coordinately regulate auxin efflux. When PIN1 and ABCB19 coincide on the plasma membrane, their interaction enhances the rate and specificity of auxin efflux and the dynamic cycling of PIN1 is reduced. However, ABCB19 function is not regulated by the dynamic cellular trafficking mechanisms that regulate PIN1 in apical tissues, as localisation of ABCB19 on the plasma membrane was not inhibited by short-term treatments with latrunculin B, oryzalin, brefeldin A (BFA) or wortmannin--all of which have been shown to alter PIN1 and/or PIN2 plasma membrane localisation. When taken up by endocytosis, the styryl dye FM4-64 labels diffuse rather than punctuate intracellular bodies in abcb19 (pgp19), and some aggregations of PIN1 induced by short-term BFA treatment did not disperse after BFA washout in abcb19. Although the subcellular localisations of ABCB19 and PIN1 in the reciprocal mutant backgrounds were like those in wild type, PIN1 plasma membrane localisation in abcb19 roots was more easily perturbed by the detergent Triton X-100, but not other non-ionic detergents. ABCB19 is stably associated with sterol/sphingolipid-enriched membrane fractions containing BIG/TIR3 and partitions into Triton X-100 detergent-resistant membrane (DRM) fractions. In the wild type, PIN1 was also present in DRMs, but was less abundant in abcb19 DRMs. These observations suggested a rationale for the observed lack of auxin transport activity when PIN1 is expressed in a non-plant heterologous system. PIN1 was therefore expressed in Schizosaccharomyces pombe, which has plant-like sterol-enriched microdomains, and catalysed auxin transport in these cells. These data suggest that ABCB19 stabilises PIN1 localisation at the plasma membrane in discrete cellular subdomains where PIN1 and ABCB19 expression overlaps.
authors.affiliation: Department of Horticulture, Purdue University, West Lafayette, IN 47907-2010, USA.
authors.forename: Boosaree
authors.initials: B
authors.lastname: Titapiwatanakun
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Blakeslee
authors.forename: Anindita
authors.initials: A
authors.lastname: Bandyopadhyay
authors.forename: Haibing
authors.initials: H
authors.lastname: Yang
authors.forename: Jozef
authors.initials: J
authors.lastname: Mravec
authors.forename: Michael
authors.initials: M
authors.lastname: Sauer
authors.forename: Yan
authors.initials: Y
authors.lastname: Cheng
authors.forename: Jiri
authors.initials: J
authors.lastname: Adamec
authors.forename: Akitomo
authors.initials: A
authors.lastname: Nagashima
authors.forename: Markus
authors.initials: M
authors.lastname: Geisler
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sakai
authors.forename: Jiri
authors.initials: J
authors.lastname: Friml
authors.forename: Wendy Ann
authors.initials: WA
authors.lastname: Peer
authors.forename: Angus S
authors.initials: AS
authors.lastname: Murphy
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D021962:Membrane Microdomains / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000378:metabolism; D013261:Sterols / Q000378:metabolism
chemical_list: C532604:ABCB19 protein, Arabidopsis; D018528:ATP-Binding Cassette Transporters; D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; C519873:PGP19 protein, Arabidopsis; C116363:PIN1 protein, Arabidopsis; D013261:Sterols