Stonins—Specialized Adaptors for Synaptic Vesicle Recycling and Beyond?

Maritzen, Tanja; Podufall, Jasmin; Haucke, Volker

doi:10.1111/j.1600-0854.2009.00971.x

Cited by 46 publications

(52 citation statements)

References 58 publications

(90 reference statements)

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“…S6 A-J). Thus, either dDAB does not participate in dSYT1 sorting or sufficient redundancy is provided by interactions of SYT1 with at least two other CLATHRIN-associated adaptor proteins, AP-2 and Stonins (4,36). Furthermore, the distributions of other synaptic vesicle proteins at dab mutant synapses, including neuronal SYN-APTOBREVIN (38) and the vesicular glutamate transporter (39), were similar to those of WT (Fig.…”

Section: Discussionmentioning

confidence: 71%

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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: 71%

“…35). This motif is of great potential interest because no classic endocytosis signals have been identified previously in SYTs (36). Finally, it is of interest to consider the roles of co-AZ and non-AZ populations of dDAB (and CLATHRIN).…”

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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“…Recapturing of exocytosed synaptic vesicle proteins within the periactive zone is achieved by adaptor proteins including the heterotetrameric AP2 complex 52 , stonin 2 (also known as stoned B) 53,54 and perhaps AP180, which serve as cargo-specific sorters of select synaptic vesicle proteins 6,55 (FIG. 2).…”

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

confidence: 99%

Protein scaffolds in the coupling of synaptic exocytosis and endocytosis

2011

Self Cite

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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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“…Stonins are conserved from Caenorhabditis elegans to humans but are not found in prokaryotes or yeast (Maritzen et al, 2010). The N-terminal domain of stonins, which binds AP-2 (Walther et al, 2004), is followed by a conserved region of unknown function (the stonin homology domain) that is exclusively found in stonins.…”

Section: Cargo-binding Adaptors That Lack Lipid-and Clathrinbinding Smentioning

confidence: 99%

Endocytic adaptors – social networking at the plasma membrane

Reider

Wendland

2011

Journal of Cell Science

105

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Receptor-mediated endocytosis is a dynamic process that is crucial for maintaining plasma membrane composition and controlling cell-signaling pathways. A variety of entry routes have evolved to ensure that the vast array of molecules on the cell surface can be differentially internalized by endocytosis. This diversity has extended to include a growing list of endocytic adaptor proteins, which are thought to initiate the internalization process. The key function of adaptors is to select the proteins that should be removed from the cell surface. Thus, they have a central role in defining the physiology of a cell. This has made the study of adaptor proteins a very active area of research that is ripe for exciting future discoveries. Here, we review recent work on how adaptors mediate endocytosis and address the following questions: what characteristics define an endocytic adaptor protein? What roles do these proteins fulfill in addition to selecting cargo and how might adaptors function in clathrin-independent endocytic pathways? Through the findings discussed in this Commentary, we hope to stimulate further characterization of known adaptors and expansion of the known repertoire by identification of new adaptors.

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Stonins—Specialized Adaptors for Synaptic Vesicle Recycling and Beyond?

Cited by 46 publications

References 58 publications

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

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

Protein scaffolds in the coupling of synaptic exocytosis and endocytosis

Endocytic adaptors – social networking at the plasma membrane

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