title: Cyclase-associated protein is essential for the functioning of the endo-lysosomal system and provides a link to the actin cytoskeleton.
abstract: Data from mutant analysis in yeast and Dictyostelium indicate a role for the cyclase-associated protein (CAP) in endocytosis and vesicle transport. We have used genetic and biochemical approaches to identify novel interacting partners of Dictyostelium CAP to help explain its molecular interactions in these processes. Cyclase-associated protein associates and interacts with subunits of the highly conserved vacuolar H(+)-ATPase (V-ATPase) and co-localizes to some extent with the V-ATPase. Furthermore, CAP is essential for maintaining the structural organization, integrity and functioning of the endo-lysosomal system, as distribution and morphology of V-ATPase- and Nramp1-decorated membranes were disturbed in a CAP mutant (CAP bsr) accompanied by an increased endosomal pH. Moreover, concanamycin A (CMA), a specific inhibitor of the V-ATPase, had a more severe effect on CAP bsr than on wild-type cells, and the mutant did not show adaptation to the drug. Also, the distribution of green fluorescent protein-CAP was affected upon CMA treatment in the wildtype and recovered after adaptation. Distribution of the V-ATPase in CAP bsr was drastically altered upon hypo-osmotic shock, and growth was slower and reached lower saturation densities in the mutant under hyper-osmotic conditions. Taken together, our data unravel a link of CAP with the actin cytoskeleton and endocytosis and suggest that CAP is an essential component of the endo-lysosomal system in Dictyostelium.
authors.affiliation: Center for Biochemistry and Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, 50931 Köln, Germany.
authors.forename: Hameeda
authors.initials: H
authors.lastname: Sultana
authors.forename: Francisco
authors.initials: F
authors.lastname: Rivero
authors.forename: Rosemarie
authors.initials: R
authors.lastname: Blau-Wasser
authors.forename: Stephan
authors.initials: S
authors.lastname: Schwager
authors.forename: Alessandra
authors.initials: A
authors.lastname: Balbo
authors.forename: Salvatore
authors.initials: S
authors.lastname: Bozzaro
authors.forename: Michael
authors.initials: M
authors.lastname: Schleicher
authors.forename: Angelika A
authors.initials: AA
authors.lastname: Noegel
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000378:metabolism; D027682:Cation Transport Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D048430:Cell Shape; D003572:Cytochalasins / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D004023:Dictyostelium / Q000166:cytology / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology; D011992:Endosomes / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism; D053778:Thiazolidines; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism; D014882:Water-Electrolyte Balance; D000099173:Natural Resistance-associated Macrophage Protein 1
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D027682:Cation Transport Proteins; D018797:Cell Cycle Proteins; D003572:Cytochalasins; D049452:Green Fluorescent Proteins; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D013844:Thiazoles; D053778:Thiazolidines; D025262:Vacuolar Proton-Translocating ATPases; D000099173:Natural Resistance-associated Macrophage Protein 1; C031218:cytochalasin A; C037068:latrunculin B