F-Actin Is Concentrated in Nonrelease Domains at Frog Neuromuscular Junctions

Dunaevsky, Anna; Connor, Elizabeth A.

doi:10.1523/jneurosci.20-16-06007.2000

Cited by 57 publications

(42 citation statements)

References 42 publications

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“…Similar morphologic changes were observed at synapses of the giant reticulospinal axon of the lamprey after microinjection of antibodies and peptides that disrupted synaptojanin recruitment (46). Studies of lamprey and mammalian synapses have demonstrated that synaptic vesicle clusters are surrounded by actin, suggesting that actin is the major component of the matrix present at these endocytic zones (28,29,56).…”

Section: Discussionmentioning

confidence: 63%

“…They also regulate a variety of proteins that control actin nucleation (13,25,26). Actin, in turn, is thought to play an important role in clathrin-mediated recycling by generating and organizing cytoskeletal scaffolds at endocytic zones (27)(28)(29) and, possibly, by contributing to the translocation of newly formed endocytic vesicles to the synaptic vesicle cluster (30)(31)(32)(33)(34).…”

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confidence: 99%

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Delayed reentry of recycling vesicles into the fusion-competent synaptic vesicle pool in synaptojanin 1 knockout mice

Kim

Chang

Daniell

et al. 2002

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

112

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Synaptojanin 1 is a polyphosphoinositide phosphatase implicated in synaptic vesicle recycling. We used FM1-43 imaging and electron microscopy in cultured cortical neurons from control and synaptojanin 1 knockout mice to study how the absence of this protein affects specific steps of the synaptic vesicle cycle. Exo͞endocytosis after a moderate stimulus was unchanged. However, during prolonged stimulation, the regeneration of fusion-competent synaptic vesicles was severely impaired. In stimulated nerve terminals, there was a persistent accumulation of clathrin-coated vesicles and a backup of newly reformed vesicles in the cytomatrix-rich area around the synaptic vesicle cluster. These findings demonstrate that synaptojanin 1 function is needed for the progression of recycling vesicles to the functional synaptic vesicle pool. N eurotransmission and its reliability depend on the efficient and precise recycling of synaptic vesicles in the presynaptic nerve terminal (1, 2). Vesicle fusion and neurotransmitter release are followed by rapid retrieval and repackaging of synaptic vesicle membrane components into new functional vesicles. Morphologic, biochemical, genetic, and functional evidence points to an important role of the clathrin-mediated recycling pathway in this process (1,(3)(4)(5). Alternative and parallel pathways may also participate in recycling (1, 2, 6-9).Growing evidence suggests that phosphoinositides play an important role in the synaptic vesicle cycle via their interaction with endocytic and actin regulatory proteins (10-13). Phosphoinositides, PI(4,5)P 2 in particular, bind clathrin adaptors such as AP-2 (14-16), AP180 (17,18), and epsin (19,20), as well as the GTPase dynamin (21, 22), which is critically required for the fission of endocytic vesicles (23, 24). They also regulate a variety of proteins that control actin nucleation (13,25,26). Actin, in turn, is thought to play an important role in clathrin-mediated recycling by generating and organizing cytoskeletal scaffolds at endocytic zones (27-29) and, possibly, by contributing to the translocation of newly formed endocytic vesicles to the synaptic vesicle cluster (30-34).Synaptojanin 1 is a polyphosphoinositide phosphatase highly enriched in presynaptic nerve terminals and localized to recycling intermediates in synaptosomes (35,36). Its COOHterminal proline-rich domain interacts with several accessory factors implicated in synaptic vesicle recycling, including amphiphysin (35), endophilin (37), (38), intersectin (34, 39), and syndapin͞pacsin (40, 41). Its NH 2 -terminal Sac1-like module hydrolyzes the phosphates of PI(3)P, PI(4)P, and PI(3,5)P 2 (42), whereas its central phosphatase module hydrolyzes the 5Ј phosphate of PI(4,5)P 2 and PI(3,4,5)P 3 (43,44). By means of these enzymatic activities, synaptojanin can dephosphorylate polyphosphoinositides to phosphatidylinositol and thereby function as a negative regulator of the interactions between membranes, coat proteins, and regulatory factors for actin.In mice knockout studies, the absence of ...

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Section: Discussionmentioning

confidence: 63%

mentioning

confidence: 99%

Delayed reentry of recycling vesicles into the fusion-competent synaptic vesicle pool in synaptojanin 1 knockout mice

Kim

Chang

Daniell

et al. 2002

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

112

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“…Because control of actin polymerization is downstream of GEF activity, intersectin 1L may act as a switch that links actin polymerization to an input from the endocytic pathway. Although we do not yet know the exact role played by actin polymerization during endocytosis (Qualmann et al, 2000), there is remarkable colocalization of endocytic events and actin polymerization at the synapse (Dunaevsky and Connor, 2000), and both are tightly regulated by phosphatidylinositol biosynthesis (Cremona and De Camilli, 2001). Intersectin 1L, localized to peri-active zones Roos and Kelly, 1999), is thus well positioned to switch on actin polymerization in endocytic regions only after a burst of exocytosis.…”

Section: Discussionmentioning

confidence: 99%

Intersectin 1L Guanine Nucleotide Exchange Activity Is Regulated by Adjacent src Homology 3 Domains That Are Also Involved in Endocytosis

Zamanian

Kelly

2003

MBoC

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Intersectin 1L is a scaffolding protein involved in endocytosis that also has guanine nucleotide exchange activity for Cdc42. In the context of the full-length protein, the catalytic exchange activity of the DH domain is repressed. Here we use biochemical methods to dissect the mechanism for this inhibition. We demonstrate that the intersectin 1L SH3 domains, which bind endocytic proteins, directly inhibit the activity of the DH domain in assays for both binding and exchange of Cdc42. This inhibitory mechanism seems to act through steric hindrance of Cdc42 binding by an intramolecular interaction between the intersectin 1L SH3 domain region and the adjacent DH domain. Surprisingly, the mode of SH3 domain binding is other than through the proline peptide binding pocket. The dual role of the SH3 domains in endocytosis and repression of exchange activity suggests that the intersectin 1L exchange activity is regulated by endocytosis. We show that the endocytic protein, dynamin, competes for binding to the SH3 domains with the neural Wiskott-Aldrich Syndrome protein, an actin filament nucleation protein that is a substrate for activated Cdc42. Swapping of SH3 domain binding partners might act as a switch controlling the actin nucleation activity of intersectin 1L. INTRODUCTIONRho family guanine nucleotide exchange factors (GEFs) are critical regulatory proteins of cellular pathways that require regulation of actin cytoskeleton rearrangements (for review see Zheng, 2001;Hoffman and Cerione, 2002). Their conserved catalytic domain, the Dbl homology (DH) domain (Hart et al., 1991(Hart et al., , 1994 catalyzes the release of GDP from Rho GTPases and thus subsequent activation by GTP binding. DH domains are invariably found upstream and adjacent to pleckstrin homology (PH) domains, which are thought to influence their activity (Liu et al., 1998;Das et al., 2000) and membrane localization (Whitehead et al., 1999). The noncatalytic parts of the structurally complex GEFs link the exchange activity to cellular processes and inhibit the DH domain exchange activity (Zheng, 2001;Hoffman and Cerione, 2002). Cellular inputs, such as protein (Hart et al., 1998;Scita et al., 1999;Innocenti et al., 2002) and phospholipid binding to (Han et al., 1998;Nimnual et al., 1998;Crompton et al., 2000;Das et al., 2000;Russo et al., 2001), and phosphorylation of (Crespo et al., 1997;Han et al., 1997;Schuebel et al., 1998;Aghazadeh et al., 2000) these regulatory regions derepress exchange activity. Integration of cellular signals by Rho GEFs can focus GTPase activity to allow temporal and spatially localized activation of actin cytoskeletal rearrangements.Intersectin 1L, a neuronal splice variant of the endocytic scaffolding protein intersectin 1, is a Rho family GEF that is composed of two N-terminal EH domains (EH1, EH2), a large region of putative coiled-coils, five SH3 domains (SH3A, B, C, D, and E; Roos and Kelly, 1998;Yamabhai et al., 1998;Okamoto et al., 1999;Sengar et al., 1999), followed by the DH and PH domains and a carboxyl-terminal ...

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“…Actin and myosin are localized to presynaptic sites (Drenckhahn and Kaiser, 1983;Dunaevsky and Connor, 2000;Morales et al, 2000). In sympathetic neurons, inhibiting myosin II decreases synaptic transmission (Mochida et al, 1994;Takagishi et al, 2005), whereas in hippocampal neurons, MLCK inhibitors, 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine⅐HCl (ML-7) and 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine⅐HCl (ML-9), reduce the access to the reserve SV pool during repetitive stimulation (Ryan, 1997).…”

Section: Introductionmentioning

confidence: 99%

Myosin Light Chain Kinase Is Not a Regulator of Synaptic Vesicle Trafficking during Repetitive Exocytosis in Cultured Hippocampal Neurons

Tokuoka

Goda²

2006

J. Neurosci.

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The mechanism by which synaptic vesicles (SVs) are recruited to the release site is poorly understood. One candidate mechanism for trafficking of SVs is the myosin-actin motor system. Myosin activity is modulated by myosin light chain kinase (MLCK), which in turn is activated by calmodulin. Ca 2ϩ signaling in presynaptic terminals, therefore, may serve to regulate SV mobility along actin filaments via MLCK. Previous studies in different types of synapses have supported such a hypothesis. Here, we further investigated the role of MLCK in neurotransmitter release at glutamatergic synapses in cultured hippocampal neurons by examining the effects of two MLCK inhibitors, 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine⅐HCl (ML-7) and wortmannin. Bath application of ML-7 enhanced shortterm depression of EPSCs to repetitive stimulation, whereas it reduced presynaptic release probability. However, ML-7 also inhibited action potential amplitude and voltage-gated Ca 2ϩ channel currents. These effects were not mimicked by wortmannin, suggesting that ML-7 was not specific to MLCK in hippocampal neurons. When SV exocytosis was directly triggered by a Ca 2ϩ ionophore, calcimycin, to bypass voltage-gated Ca 2ϩ channels, ML-7 had no effect on neurotransmitter release. Furthermore, when SV exocytosis elicited by electrical field stimulation was monitored by styryl dye, FM1-43 [N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl) pyridinium dibromide], the unloading kinetics of the dye was not altered in the presence of wortmannin. These data indicate that MLCK is not a major regulator of presynaptic SV trafficking during repetitive exocytosis at hippocampal synapses.

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F-Actin Is Concentrated in Nonrelease Domains at Frog Neuromuscular Junctions

Cited by 57 publications

References 42 publications

Delayed reentry of recycling vesicles into the fusion-competent synaptic vesicle pool in synaptojanin 1 knockout mice

Delayed reentry of recycling vesicles into the fusion-competent synaptic vesicle pool in synaptojanin 1 knockout mice

Intersectin 1L Guanine Nucleotide Exchange Activity Is Regulated by Adjacent src Homology 3 Domains That Are Also Involved in Endocytosis

Myosin Light Chain Kinase Is Not a Regulator of Synaptic Vesicle Trafficking during Repetitive Exocytosis in Cultured Hippocampal Neurons

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