title: Overexpression of frequenin, a modulator of phosphatidylinositol 4-kinase, inhibits biosynthetic delivery of an apical protein in polarized madin-darby canine kidney cells.
abstract: Polyphosphoinositides regulate numerous steps in membrane transport. The levels of individual phosphatidylinositols are controlled by specific lipid kinases, whose activities and localization are in turn regulated by a variety of effectors. Here we have examined the effect of overexpression of frequenin, a modulator of phosphatidylinositol 4-kinase activity, on biosynthetic and postendocytic traffic in polarized Madin-Darby canine kidney cells. Endogenous frequenin was identified in these cells by polymerase chain reaction, Western blotting, and indirect immunofluorescence. Adenoviral-mediated overexpression of frequenin had no effect on early Golgi transport of membrane proteins, as assessed by acquisition of resistance to endoglycosidase H. However, delivery of newly synthesized influenza hemagglutinin from the trans-Golgi network to the apical cell surface was severely inhibited in cells overexpressing frequenin, whereas basolateral delivery of the polymeric immunoglobulin receptor was unaffected. Overexpression of frequenin did not affect postendocytic trafficking steps including apical and basolateral recycling and basal-to-apical transcytosis. We conclude that frequenin, and by inference, phosphatidylinositol 4-kinase, plays an important and selective role in apical delivery in polarized cells.
authors.affiliation: Laboratory of Epithelial Cell Biology, Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA. weisz@msx.dept-med.pitt.edu
authors.forename: O A
authors.initials: OA
authors.lastname: Weisz
authors.forename: G A
authors.initials: GA
authors.lastname: Gibson
authors.forename: S M
authors.initials: SM
authors.lastname: Leung
authors.forename: J
authors.initials: J
authors.lastname: Roder
authors.forename: A
authors.initials: A
authors.lastname: Jeromin
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase / Q000378:metabolism*; D000256:Adenoviridae; D000818:Animals; D001921:Brain / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D016764:Cell Polarity; D004285:Dogs; D019084:Fluorescent Antibody Technique, Indirect; D005822:Genetic Vectors; D006056:Golgi Apparatus / Q000378:metabolism; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000096:biosynthesis* / Q000235:genetics; D007668:Kidney; D007700:Kinetics; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D014162:Transfection
chemical_list: D002135:Calcium-Binding Proteins; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D009419:Nerve Tissue Proteins; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides; D011994:Recombinant Proteins; C101464:frequenin calcium sensor proteins; D019870:1-Phosphatidylinositol 4-Kinase