title: Unconventional secretion of AcbA in Dictyostelium discoideum through a vesicular intermediate.
abstract: The acyl coenzyme A (CoA) binding protein AcbA is secreted unconventionally and processed into spore differentiation factor 2 (SDF-2), a peptide that coordinates sporulation in Dictyostelium discoideum. We report that AcbA is localized in vesicles that accumulate in the cortex of prespore cells just prior to sporulation. These vesicles are not observed after cells are stimulated to release AcbA but remain visible after stimulation in cells lacking the Golgi reassembly stacking protein (GRASP). Acyl-CoA binding is required for the inclusion of AcbA in these vesicles, and the secretion of AcbA requires N-ethylmaleimide-sensitive factor (NSF). About 1% of the total cellular AcbA can be purified within membrane-bound vesicles. The yield of vesicles decreases dramatically when purified from wild-type cells that were stimulated to release AcbA, whereas the yield from GRASP mutant cells was only modestly altered by stimulation. We suggest that these AcbA-containing vesicles are secretion intermediates and that GRASP functions at a late step leading to the docking/fusion of these vesicles at the cell surface.
authors.affiliation: Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Cabral
authors.forename: Christophe
authors.initials: C
authors.lastname: Anjard
authors.forename: Vivek
authors.initials: V
authors.lastname: Malhotra
authors.forename: William F
authors.initials: WF
authors.lastname: Loomis
authors.forename: Adam
authors.initials: A
authors.lastname: Kuspa
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism; D002498:Centrifugation; D003902:Detergents / Q000494:pharmacology; D004023:Dictyostelium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins; D052066:N-Ethylmaleimide-Sensitive Proteins / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D015800:Protozoan Proteins / Q000378:metabolism*; D022142:Secretory Vesicles / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D000214:Acyl Coenzyme A; D003902:Detergents; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D015800:Protozoan Proteins; C484455:SDF-2 protein, Dictyostelium discoideum; D005680:gamma-Aminobutyric Acid; D052066:N-Ethylmaleimide-Sensitive Proteins
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