title: Disruption of F-actin stimulates hypertonic activation of the BGT1 transporter in MDCK cells.
abstract: Many membrane transport systems are altered by changes in the state of the actin cytoskeleton. Although an intact microtubule network is required for hypertonic activation of the betaine transporter (BGT1), the possible role of the actin cytoskeleton is unknown. BGT1 function in Madin-Darby canine kidney cell monolayers was assessed as Na(+)-dependent uptake of GABA, following disassembly of F-actin by cytochalasin D (1.0 microM) or latrunculin A (0.6 microM). Both drugs significantly increased (P < 0.001) the activation of BGT1 transport by 24-h hypertonicity (500 mosmol/kgH(2)O). In contrast, the hypertonic upregulation of Na(+)-dependent alanine uptake remained unaltered by cytochalasin D. Disruption of F-actin did not interfere with downregulation of BGT1 transport when cells were transferred from hypertonic to isotonic medium. Immunofluorescence staining revealed colocalization of BGT1 and F-actin at the plasma membrane of hypertonic cells. Surface biotinylation revealed no major change in BGT1 protein abundance after cytochalasin D action, suggesting that stimulation of hypertonic activation of BGT1 transport is due to increased activity of existing BGT1 transporters.
authors.affiliation: Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5120, USA.
authors.forename: Jeremy L
authors.initials: JL
authors.lastname: Bricker
authors.forename: Shaoyou
authors.initials: S
authors.lastname: Chu
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Kempson
mesh_terms: D000199:Actins / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002352:Carrier Proteins / Q000187:drug effects* / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D015638:Cytochalasin D / Q000494:pharmacology; D004285:Dogs; D050485:GABA Plasma Membrane Transport Proteins; D006982:Hypertonic Solutions / Q000494:pharmacology*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D014018:Tissue Distribution; D015854:Up-Regulation
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002352:Carrier Proteins; D050485:GABA Plasma Membrane Transport Proteins; D006982:Hypertonic Solutions; D019384:Nucleic Acid Synthesis Inhibitors; D013844:Thiazoles; D053778:Thiazolidines; C072207:betaine plasma membrane transport proteins; D015638:Cytochalasin D; C037067:latrunculin A