title: Phosphatidylinositol-4-kinase type II alpha is a component of adaptor protein-3-derived vesicles.
abstract: A membrane fraction enriched in vesicles containing the adaptor protein (AP) -3 cargo zinc transporter 3 was generated from PC12 cells and was used to identify new components of these organelles by mass spectrometry. Proteins prominently represented in the fraction included AP-3 subunits, synaptic vesicle proteins, and lysosomal proteins known to be sorted in an AP-3-dependent way or to interact genetically with AP-3. A protein enriched in this fraction was phosphatidylinositol-4-kinase type IIalpha (PI4KIIalpha). Biochemical, pharmacological, and morphological analyses supported the presence of PI4KIIalpha in AP-3-positive organelles. Furthermore, the subcellular localization of PI4KIIalpha was altered in cells from AP-3-deficient mocha mutant mice. The PI4KIIalpha normally present both in perinuclear and peripheral organelles was substantially decreased in the peripheral membranes of AP-3-deficient mocha fibroblasts. In addition, as is the case for other proteins sorted in an AP-3-dependent way, PI4KIIalpha content was strongly reduced in nerve terminals of mocha hippocampal mossy fibers. The functional relationship between AP-3 and PI4KIIalpha was further explored by PI4KIIalpha knockdown experiments. Reduction of the cellular content of PI4KIIalpha strongly decreased the punctate distribution of AP-3 observed in PC12 cells. These results indicate that PI4KIIalpha is present on AP-3 organelles where it regulates AP-3 function.
authors.affiliation: Department of Cell Biology, Emory University, Atlanta, GA 30322, USA.
authors.forename: Gloria
authors.initials: G
authors.lastname: Salazar
authors.forename: Branch
authors.initials: B
authors.lastname: Craige
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Wainer
authors.forename: Jun
authors.initials: J
authors.lastname: Guo
authors.forename: Pietro
authors.initials: P
authors.lastname: De Camilli
authors.forename: Victor
authors.initials: V
authors.lastname: Faundez
mesh_terms: D033963:Adaptor Protein Complex 3 / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D006624:Hippocampus / Q000378:metabolism; D051379:Mice; D046529:Microscopy, Electron, Transmission; D015778:Minor Histocompatibility Antigens; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D040901:Proteomics; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats
chemical_list: D033963:Adaptor Protein Complex 3; D015778:Minor Histocompatibility Antigens; D034741:RNA, Small Interfering; D017853:Phosphotransferases (Alcohol Group Acceptor); C402182:phosphatidylinositol phosphate 4-kinase