title: Myosin VI regulates endocytosis of the cystic fibrosis transmembrane conductance regulator.
abstract: The cystic fibrosis transmembrane conductance regulator (CFTR) is a cyclic AMP-regulated Cl(-) channel expressed in the apical plasma membrane in fluid-transporting epithelia. Although CFTR is rapidly endocytosed from the apical membrane of polarized epithelial cells and efficiently recycled back to the plasma membrane, little is known about the molecular mechanisms regulating CFTR endocytosis and endocytic recycling. Myosin VI, an actin-dependent, minus-end directed mechanoenzyme, has been implicated in clathrin-mediated endocytosis in epithelial cells. The goal of this study was to determine whether myosin VI regulates CFTR endocytosis. Endogenous, apical membrane CFTR in polarized human airway epithelial cells (Calu-3) formed a complex with myosin VI, the myosin VI adaptor protein Disabled 2 (Dab2), and clathrin. The tail domain of myosin VI, a dominant-negative recombinant fragment, displaced endogenous myosin VI from interacting with Dab2 and CFTR and increased the expression of CFTR in the plasma membrane by reducing CFTR endocytosis. However, the myosin VI tail fragment had no effect on the recycling of endocytosed CFTR or on fluid-phase endocytosis. CFTR endocytosis was decreased by cytochalasin D, an actin-filament depolymerizing agent. Taken together, these data indicate that myosin VI and Dab2 facilitate CFTR endocytosis by a mechanism that requires actin filaments.
authors.affiliation: Dartmouth Medical School, Department of Physiology, Hanover, New Hampshire 03755, USA. Agnieszka.Swiatecka-Urban@Dartmouth.edu
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Swiatecka-Urban
authors.forename: Cary
authors.initials: C
authors.lastname: Boyd
authors.forename: Bonita
authors.initials: B
authors.lastname: Coutermarsh
authors.forename: Katherine H
authors.initials: KH
authors.lastname: Karlson
authors.forename: Roxanna
authors.initials: R
authors.lastname: Barnaby
authors.forename: Laura
authors.initials: L
authors.lastname: Aschenbrenner
authors.forename: George M
authors.initials: GM
authors.lastname: Langford
authors.forename: Tama
authors.initials: T
authors.lastname: Hasson
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Stanton
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins; D001483:Base Sequence; D002460:Cell Line; D002966:Clathrin / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000502:physiology*; D017931:DNA Primers; D004705:Endocytosis / Q000502:physiology*; D016147:Genes, Tumor Suppressor; D006801:Humans; D018995:Myosin Heavy Chains / Q000502:physiology*; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014132:Trachea / Q000166:cytology / Q000378:metabolism; D025521:Tumor Suppressor Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D051017:Apoptosis Regulatory Proteins; C505032:CFTR protein, human; D002966:Clathrin; C102885:DAB2 protein, human; D017931:DNA Primers; D025521:Tumor Suppressor Proteins; C089785:myosin VI; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D018995:Myosin Heavy Chains