title: Fife, a Drosophila Piccolo-RIM homolog, promotes active zone organization and neurotransmitter release.
abstract: Neuronal communication depends on the precisely orchestrated release of neurotransmitter at specialized sites called active zones (AZs). A small number of scaffolding and cytoskeletal proteins comprising the cytomatrix of the active zone (CAZ) are thought to organize the architecture and functional properties of AZs. The majority of CAZ proteins are evolutionarily conserved, underscoring the fundamental similarities in neurotransmission at all synapses. However, core CAZ proteins Piccolo and Bassoon have long been believed exclusive to vertebrates, raising intriguing questions about the conservation of the molecular mechanisms that regulate presynaptic properties. Here, we present the identification of a piccolo-rim-related gene in invertebrates, together with molecular phylogenetic analyses that indicate the encoded proteins may represent Piccolo orthologs. In accordance, we find that the Drosophila homolog, Fife, is neuronal and localizes to presynaptic AZs. To investigate the in vivo function of Fife, we generated a deletion of the fife locus. We find that evoked neurotransmitter release is substantially decreased in fife mutants and loss of fife results in motor deficits. Through morphological analysis of fife synapses, we identify underlying AZ abnormalities including pervasive presynaptic membrane detachments and reduced synaptic vesicle clustering. Our data demonstrate the conservation of a Piccolo-related protein in invertebrates and identify critical roles for Fife in regulating AZ structure and function. These findings suggest the CAZ is more conserved than previously thought, and open the door to a more complete understanding of how CAZ proteins regulate presynaptic structure and function through genetic studies in simpler model systems.
authors.affiliation: Cell and Molecular Biology Training Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Bruckner
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Gratz
authors.forename: Jessica K
authors.initials: JK
authors.lastname: Slind
authors.forename: Richard R
authors.initials: RR
authors.lastname: Geske
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Cummings
authors.forename: Samantha E
authors.initials: SE
authors.lastname: Galindo
authors.forename: Laura K
authors.initials: LK
authors.lastname: Donohue
authors.forename: Kate M
authors.initials: KM
authors.lastname: O'Connor-Giles
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001921:Brain / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism*; D013569:Synapses / Q000235:genetics / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology; D013572:Synaptic Vesicles / Q000235:genetics / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; D029721:Drosophila Proteins; C578333:Fife protein, Drosophila; D009419:Nerve Tissue Proteins; D009479:Neuropeptides