title: A single β adaptin contributes to AP1 and AP2 complexes and clathrin function in Dictyostelium.
abstract: The assembly of clathrin-coated vesicles is important for numerous cellular processes, including nutrient uptake and membrane organization. Important contributors to clathrin assembly are four tetrameric assembly proteins, also called adaptor proteins (APs), each of which contains a β subunit. We identified a single β subunit, named β1/2, that contributes to both the AP1 and AP2 complexes of Dictyostelium. Disruption of the gene encoding β1/2 resulted in severe defects in growth, cytokinesis and development. Additionally, cells lacking β1/2 displayed profound osmoregulatory defects including the absence of contractile vacuoles and mislocalization of contractile vacuole markers. The phenotypes of β1/2 null cells were most similar to previously described phenotypes of clathrin and AP1 mutants, supporting a particularly important contribution of AP1 to clathrin pathways in Dictyostelium cells. The absence of β1/2 in cells led to significant reductions in the protein amounts of the medium-sized subunits of the AP1 and AP2 complexes, establishing a role for the β subunit in the stability of the medium subunits. Dictyostelium β1/2 could resemble a common ancestor of the more specialized β1 and β2 subunits of the vertebrate AP complexes. Our results support the essential contribution of a single β subunit to the stability and function of AP1 and AP2 in a simple eukaryote.
authors: Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
authors: R Thomas
authors: RT
authors: Sosa
authors: Michelle M
authors: MM
authors: Weber
authors: Yujia
authors: Y
authors: Wen
authors: Theresa J
authors: TJ
authors: O'Halloran
mesh_terms: D033961:Adaptor Protein Complex 1 / Q000235:genetics / Q000378:metabolism*; D033962:Adaptor Protein Complex 2 / Q000235:genetics / Q000378:metabolism*; D033965:Adaptor Protein Complex alpha Subunits / Q000235:genetics / Q000378:metabolism; D033966:Adaptor Protein Complex beta Subunits / Q000235:genetics / Q000378:metabolism*; D033983:Adaptor Protein Complex mu Subunits / Q000235:genetics / Q000378:metabolism; D034002:Adaptor Protein Complex sigma Subunits / Q000235:genetics; D000595:Amino Acid Sequence / Q000502:physiology; D002449:Cell Aggregation / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D002633:Chemotaxis / Q000502:physiology; D002966:Clathrin / Q000235:genetics / Q000378:metabolism*; D033922:Clathrin Heavy Chains / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D048749:Cytokinesis / Q000502:physiology; D004023:Dictyostelium / Q000166:cytology / Q000502:physiology*; D048690:Fruiting Bodies, Fungal / Q000166:cytology / Q000502:physiology; D055786:Gene Knockout Techniques; D006056:Golgi Apparatus / Q000378:metabolism; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000502:physiology; D054730:Protein Interaction Domains and Motifs / Q000502:physiology; D014617:Vacuoles / Q000502:physiology; D014882:Water-Electrolyte Balance / Q000502:physiology
chemical_list: D033961:Adaptor Protein Complex 1; D033962:Adaptor Protein Complex 2; D033965:Adaptor Protein Complex alpha Subunits; D033966:Adaptor Protein Complex beta Subunits; D033983:Adaptor Protein Complex mu Subunits; D034002:Adaptor Protein Complex sigma Subunits; D002966:Clathrin; D033922:Clathrin Heavy Chains