title: A phosphatidylinositol 3-kinase class III sub-complex containing VPS15, VPS34, Beclin 1, UVRAG and BIF-1 regulates cytokinesis and degradative endocytic traffic.
abstract: The mammalian class III phosphatidylinositol 3-kinase (PI3K-III) complex regulates fundamental cellular functions, including growth factor receptor degradation, cytokinesis and autophagy. Recent studies suggest the existence of distinct PI3K-III sub-complexes that can potentially confer functional specificity. While a substantial body of work has focused on the roles of individual PI3K-III subunits in autophagy, functional studies on their contribution to endocytic receptor downregulation and cytokinesis are limited. We therefore sought to elucidate the specific nature of the PI3K-III complexes involved in these two processes. High-content microscopy-based assays combined with siRNA-mediated depletion of individual subunits indicated that a specific sub-complex containing VPS15, VPS34, Beclin 1, UVRAG and BIF-1 regulates both receptor degradation and cytokinesis, whereas ATG14L, a PI3K-III subunit involved in autophagy, is not required. The unanticipated role of UVRAG and BIF-1 in cytokinesis was supported by a strong localisation of these proteins to the midbody. Importantly, while the tumour suppressive functions of Beclin 1, UVRAG and BIF-1 have previously been ascribed to their roles in autophagy, these results open the possibility that they may also contribute to tumour suppression via downregulation of mitogenic signalling by growth factor receptors or preclusion of aneuploidy by ensuring faithful completion of cell division.
authors.affiliation: Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway. sigrid.thoresen@rr-research.no
authors.forename: Sigrid B
authors.initials: SB
authors.lastname: Thoresen
authors.forename: Nina Marie
authors.initials: NM
authors.lastname: Pedersen
authors.forename: Knut
authors.initials: K
authors.lastname: Liestøl
authors.forename: Harald
authors.initials: H
authors.lastname: Stenmark
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D064127:Aurora Kinases; D000071183:Autophagy-Related Proteins; D000071186:Beclin-1; D058546:Class III Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D048749:Cytokinesis / Q000502:physiology*; D022083:Cytoplasmic Structures / Q000378:metabolism; D015536:Down-Regulation / Q000502:physiology; D004705:Endocytosis / Q000502:physiology*; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D058571:Vacuolar Sorting Protein VPS15 / Q000235:genetics / Q000378:metabolism*
chemical_list: C539000:ATG14 protein, human; D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D051017:Apoptosis Regulatory Proteins; D000071183:Autophagy-Related Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D034741:RNA, Small Interfering; C429293:SH3GLB1 protein, human; D025521:Tumor Suppressor Proteins; C408122:UVRAG protein, human; D004815:Epidermal Growth Factor; D058546:Class III Phosphatidylinositol 3-Kinases; C512478:EGFR protein, human; D066246:ErbB Receptors; D064127:Aurora Kinases; C546851:PIK3R4 protein, human; D017346:Protein Serine-Threonine Kinases; D058571:Vacuolar Sorting Protein VPS15