title: V-ATPase V0 sector subunit a1 in neurons is a target of calmodulin.
abstract: The V(0) complex forms the proteolipid pore of a vesicular ATPase that acidifies vesicles. In addition, an independent function in membrane fusion has been suggested in vacuolar fusion in yeast and synaptic vesicle exocytosis in fly neurons. Evidence for a direct role in secretion has also recently been presented in mouse and worm. The molecular mechanisms of how the V(0) components might act or are regulated are largely unknown. Here we report the identification and characterization of a calmodulin-binding site in the large cytosolic N-terminal region of the Drosophila protein V100, the neuron-specific V(0) subunit a1. V100 forms a tight complex with calmodulin in a Ca(2+)-dependent manner. Mutations in the calmodulin-binding site in Drosophila lead to a loss of calmodulin recruitment to synapses. Neuronal expression of a calmodulin-binding deficient V100 uncovers an incomplete rescue at low levels and cellular toxicity at high levels. Our results suggest a vesicular ATPase V(0)-dependent function of calmodulin at synapses.
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, Texas 77030.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Physiology and Green Center Division for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390.
authors.forename: Dong
authors.initials: D
authors.lastname: Wang
authors.affiliation: Department of Physiology and Green Center Division for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390.
authors.forename: Elzi
authors.initials: E
authors.lastname: Volk
authors.affiliation: Departments of Molecular and Human Genetics and Neuroscience and Howard Hughes Medical Institute, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: Hugo J
authors.initials: HJ
authors.lastname: Bellen
authors.affiliation: Department of Physiology and Green Center Division for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390. Electronic address: robin.hiesinger@utsouthwestern.edu.
authors.forename: Peter Robin
authors.initials: PR
authors.lastname: Hiesinger
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, Texas 77030. Electronic address: faq@bcm.tmc.edu.
authors.forename: Florante A
authors.initials: FA
authors.lastname: Quiocho
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D002850:Chromatography, Gel; D004330:Drosophila / Q000166:cytology / Q000378:metabolism; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009474:Neurons / Q000378:metabolism*; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D013569:Synapses / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D002147:Calmodulin; D029721:Drosophila Proteins; D014364:Tryptophan; D025262:Vacuolar Proton-Translocating ATPases; D002118:Calcium