Synaptotagmin I is necessary for compensatory synaptic vesicle endocytosis in vivo

Poskanzer, Kira E.; Marek, Kurt W.; Sweeney, Sean T.; Davis, Graeme W.

doi:10.1038/nature02184

Cited by 255 publications

(207 citation statements)

References 30 publications

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“…SYT1 proteins play an important role in synaptic transmission by serving as a calcium sensor for neurotransmitter release (reviewed in ref. 33) and also function in synaptic vesicle endocytosis (4,34). The dSYT1 NP×Y motif (residues 387-390; NPYY), which is identical in mammalian SYT1 proteins and conserved in other SYTs, is located within the C2B domain near a basic region previously implicated in SYT1-AP-2 interactions (figure 2 in ref.…”

Section: Discussionmentioning

confidence: 99%

The DISABLED protein functions in CLATHRIN-mediated synaptic vesicle endocytosis and exoendocytic coupling at the active zone

Kawasaki

Iyer

Posey

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Members of the DISABLED (DAB) family of proteins are known to play a conserved role in endocytic trafficking of cell surface receptors by functioning as monomeric CLATHRIN-associated sorting proteins that recruit cargo proteins into endocytic vesicles. Here, we report a Drosophila disabled mutant revealing a novel role for DAB proteins in chemical synaptic transmission. This mutant exhibits impaired synaptic function, including a rapid activitydependent reduction in neurotransmitter release and disruption of synaptic vesicle endocytosis. In presynaptic boutons, Drosophila DAB and CLATHRIN were highly colocalized within two distinct classes of puncta, including relatively dim puncta that were located at active zones and may reflect endocytic mechanisms operating at neurotransmitter release sites. Finally, broader analysis of endocytic proteins, including DYNAMIN, supported a general role for CLATHRIN-mediated endocytic mechanisms in rapid clearance of neurotransmitter release sites for subsequent vesicle priming and refilling of the release-ready vesicle pool.I ntensive study of chemical synaptic transmission has led to detailed molecular models of synaptic vesicle endocytosis (1-4). Ongoing efforts seek to define the underlying molecular components and interactions further as well as their spatial organization with respect to neurotransmitter release sites. The present study reveals novel molecular mechanisms and interactions in synaptic vesicle endocytosis involving a member of the DISABLED family of Phosphotyrosine Binding (PTB) domain proteins. In Drosophila, the disabled (dab) gene, the founding member of the dab gene family, was first identified in a screen for genetic modifiers of abelson (5). Although putative dab mutations were subsequently mapped to a different gene (6), recent studies have established functional interactions of Drosophila DISABLED (dDAB) and ABELSON (7). Proteins closely related to dDAB, including mouse DAB-2 (mDAB-2) and the single Caenorhabditis elegans family member ceDAB-1, function as CLATHRIN-associated adaptors in endocytic trafficking of cell surface receptors (8-10). These DABs have been shown to interact with CLATHRIN, the α-ADAPTIN (AP-2) adaptor complex, and other components of the endocytic machinery through conserved binding motifs (8-10) (Fig. 1A). Notably, mDAB-2, ceDAB-1, and dDAB share a PTB/DAB Homology (DH) domain near the N terminus (Fig. 1B), which interacts with specific vesicle cargo proteins and phosphatidylinositol-4,5-diphosphate (11, 12). Neither DAB proteins nor PTB domain interactions have been previously implicated in synaptic vesicle trafficking.The present study reveals a role for DAB proteins in synaptic vesicle endocytosis and extends previous work on interactions of endocytic and exocytic mechanisms in neurotransmitter release. Here, we use a glutamatergic neuromuscular synapse of the Drosophila adult as a model for genetic analysis of molecular mechanisms determining conserved properties of glutamatergic synapse function (13,14). Previous analysis i...

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Section: Discussionmentioning

confidence: 99%

The DISABLED protein functions in CLATHRIN-mediated synaptic vesicle endocytosis and exoendocytic coupling at the active zone

Kawasaki

Iyer

Posey

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…Endocytic defects are also observed in mice lacking the synaptotagmin 1-associated synaptic vesicle proteins synaptic vesicle glycoprotein 2A and synaptic vesicle glycoprotein 2B 79 . Even more dramatic changes occur upon acute photoinactivation of synaptotagmin 1 at fly neuromuscular junctions, with a near complete loss of stimulus-evoked synaptopHluorin retrieval 80 . Collectively, these data suggest a crucial role of certain synaptic vesicle proteins in coupling the exocytic and endocytic limbs of the vesicle cycle.…”

Section: Box 1 | Presynaptic Organization -Exocytic and Endocytic Zonesmentioning

confidence: 99%

Protein scaffolds in the coupling of synaptic exocytosis and endocytosis

2011

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Communication between nerve cells largely occurs at chemical synapses -specialized sites of cell-cell contact where electrical signals trigger the exocytic release of neurotransmitter, which in turn activates postsynaptic receptor channels. The efficacy with which such chemical signals are transmitted is crucial for the functioning of the nervous system. Modulation of neurotransmission enables nerve cells to respond to a vast range of stimulus patterns. Synaptic activity can also be tremendously diverse; from the fast synapses of the hippocampus, to slow neuropeptide-containing synapses. Indeed, some signalling pathways are active in the absence of stimulation, such as those involved in the processing of sensory information, which transmit tonically at high rates of up to 100 Hz or more 1,2 .Intriguing questions arise from these facts, including how high rates of neurotransmission can be maintained over long periods of time, and what limits the ability of a given synapse to release neurotransmitter during sustained periods of activity. Recent data indicate that in many synapses, exocytosis of neurotransmitter is coupled to endocytosis, and that synapses have evolved a specialized apparatus of scaffolding proteins to comply with these demands. Such scaffolds aid the temporal and spatial coupling of exocytosis and endocytosis, and are crucial for maintaining rapid neurotransmission during sustained activity 3 .Exocytosis of neurotransmitter is triggered by stimulusinduced calcium influx into the nerve terminal 4,5 and the subsequent fusion of synaptic vesicles with the presynaptic plasma membrane at specialized regions called active zones (BOX 1). Exocytosed synaptic vesicle membrane proteins and lipids in turn are recycled at the endocytic or periactive zone (BOX 1) that surrounds the release site, to restore functional synaptic vesicle pools for reuse and to ensure long-term functionality of the synapse 6-8 (FIG. 1). Depending on the type of synapse and the stimulation frequency, several modes of endocytosis with different time constants -for example, fast and slow endocytosisseem to operate 7,9,10 . Clathrin-mediated endocytosis arguably represents the main pathway of synaptic vesicle endocytosis 6,8,11 , although other modes -for example, fast kiss-and-run exocytosis and endocytosis -could operate in parallel.Although the machineries for exocytic membrane fusion 12,13 and for endocytic retrieval of synaptic vesicle membranes have been studied separately in some detail 6,14 , comparatively little is known about the coupling between exocytosis and endocytosis. Here we synthesize recent data from physiological, morphological and biochemical studies in several model systems into hypothetical models for scaffold-based mechanisms underlying exocytic-endocytic coupling.The synaptic vesicle cycle Synaptic vesicle pools. Some defining features of chemical synapses are the presence of one or several clusters of synaptic vesicles in the presynaptic nerve terminal, and ultrastructural specializations at the pre-and postsy...

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“…The pHluorin signal decreases again as endocytosis and vesicle acidification occur. This experimental strategy has revealed the kinetics and retrieval of vesicle dynamics (Granseth et al, 2006), vesicle fusion events in motor neurons in Drosophila larvae (Denker et al, 2011), and endocytosis in situ (Poskanzer, Marek, Sweeney, & Davis, 2003).…”

Section: Subcellular Ph Measurementsmentioning

confidence: 99%

“…For our analyses, we used an inverted, spinning disk confocal microscope system that was built for live-cell imaging (Poskanzer et al, 2003;Stehbens, Pemble, Murrow, & Wittmann, 2012). For imaging mammalian cells, it is important to have temperature control and to have a constant CO 2 gas supply to support pH homeostasis for the duration of the experiment.…”

Section: Ratiometric Imagingmentioning

confidence: 99%