The <i>unc‐18</i> Gene Encodes a Novel Protein Affecting the Kinetics of Acetylcholine Metabolism in the Nematode <i>Caenorhabditis elegans</i>

Hosono, Ryuji; Hekimi, Siegfried; Kamiya, Yushi; Sassa, Toshihiro; Murakami, Seishi; Nishiwaki, Kiyoji; Miwa, Johji; Taketo, Akira; Kodaira, Ken-Ichi

doi:10.1111/j.1471-4159.1992.tb11373.x

Cited by 173 publications

(117 citation statements)

References 34 publications

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“…Because all proteins under investigation are highly conserved evolutionarily, these experiments were conducted in C. elegans, an organism that has been extensively used to study axonal transport (24). Mutations in each of the four proteins are known to result in an uncoordinated phenotype typical for most defects in synaptic transmission (25)(26)(27)(28)(29), with the orthologs being UNC-18 (Munc18), UNC-76 (FEZ1), UNC-64 (Stx), and UNC-116 (Kinesin-1).…”

Section: Mutation Of Unc-76 In C Elegans Impairs Axonal Transport Ofmentioning

confidence: 99%

Phosphorylation-regulated axonal dependent transport of syntaxin 1 is mediated by a Kinesin-1 adapter

Chua

Butkevich

Worseck

et al. 2012

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

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Presynaptic nerve terminals are formed from preassembled vesicles that are delivered to the prospective synapse by kinesin-mediated axonal transport. However, precisely how the various cargoes are linked to the motor proteins remains unclear. Here, we report a transport complex linking syntaxin 1a (Stx) and Munc18, two proteins functioning in synaptic vesicle exocytosis at the presynaptic plasma membrane, to the motor protein Kinesin-1 via the kinesin adaptor FEZ1. Mutation of the FEZ1 ortholog UNC-76 in Caenorhabditis elegans causes defects in the axonal transport of Stx. We also show that binding of FEZ1 to Kinesin-1 and Munc18 is regulated by phosphorylation, with a conserved site (serine 58) being essential for binding. When expressed in C. elegans, wild-type but not phosphorylationdeficient FEZ1 (S58A) restored axonal transport of Stx. We conclude that FEZ1 operates as a kinesin adaptor for the transport of Stx, with cargo loading and unloading being regulated by protein kinases. T he formation and maintenance of presynaptic boutons are intricate but highly efficient processes during which the machinery for exocytosis and recycling of synaptic vesicles is assembled from preformed units. These units are delivered to the nascent synapse via molecular motor proteins of the kinesin superfamily (reviewed in Ref. 1).Although Kinesin-3 appears to be the main motor transporting synaptic vesicle precursors, recent evidence suggests that Kinesin-1 (KIF5) is also involved. In Drosophila, deletion of UNC-76/ fasciculation and elongation protein zeta 1 (FEZ1), a specific adaptor for Kinesin-1, left synaptic vesicles stranded in the axon (2, 3), showing that Kinesin-1 is needed at least during later phases of axonal transport. Transport of the synaptic vesicle protein synaptotagmin by the UNC-76/Kinesin-1 complex requires phosphorylation of UNC-76 by the UNC-51/ATG1 kinase, a prerequisite for UNC-76 to bind synaptotagmin (3). Deletion of this kinase phenocopies deletion of UNC-76. Indeed, phosphorylation-regulated interactions between cargo, adaptors, and kinesins have also been observed for other transport complexes such as the kinesin light chain/JIP1 (c-Jun N-terminal kinase-interacting protein 1) complex (4). This suggests that phosphorylation is a common mechanism for the regulation of kinesin-based transport complexes (5).Less is known about the involvement of Kinesin-1 in the transport of other classes of synaptic precursor vesicles. Transport of syntaxin 1a (Stx), an essential component of the exocytotic release apparatus residing in the presynaptic plasma membrane, is clearly distinct from synaptic vesicle precursors and appears to involve a complex between Kinesin-1 and the Stx-binding protein syntabulin (6, 7). Down-regulation or expression of dominant-negative syntabulin reduces but does not abolish membrane delivery of Stx, indicating the existence of other transport mechanisms (6). Moreover, proper intracellular trafficking of Stx and its function in exocytosis depends on Munc18 coexpression (8-14). Stx tra...

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Section: Mutation Of Unc-76 In C Elegans Impairs Axonal Transport Ofmentioning

confidence: 99%

Phosphorylation-regulated axonal dependent transport of syntaxin 1 is mediated by a Kinesin-1 adapter

Chua

Butkevich

Worseck

et al. 2012

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

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“…exocytosis in mice (1,2), Drosophila (3), and Caenorhabditis elegans (4). The precise modality of the contribution of Munc18-1 to exocytosis has been extensively studied in recent years through rescue assays with Munc18-1-deficient neurons (5,6), chromaffin cells (7) and Munc18-1/2 double knockdown neuroendocrine PC12 cells (8 -12), as well as through liposome fusion assays (13)(14)(15)(16)(17).…”

mentioning

confidence: 99%

A Pivotal Role for Pro-335 in Balancing the Dual Functions of Munc18-1 Domain-3a in Regulated Exocytosis

Han

Park

Bin

et al. 2014

Journal of Biological Chemistry

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Background: Munc18-1 has multiple roles in neuronal exocytosis by regulating SNARE proteins. Results: Mutations within domain-3a of Munc18-1 perturb syntaxin-1 chaperoning function and exocytosis. Conclusion: Domain-3a plays a crucial role in syntaxin-1 chaperoning in addition to the priming function, and Pro-335 is pivotal in regulating the balance between these two functions. Significance: This work provides mechanistic insights about how Munc18-1 controls exocytosis.

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“…In particular, the mammalian Munc18 proteins are homologous to the Saccharomyces cerevisiae n-Sec1/rbSec1, Caenorhabditis elegans unc18, and Drosophila melanogaster Rop proteins (19 -23). These proteins bind with high affinity to their cognate plasma membrane syntaxins, and null mutations in these genes cause dramatic reduction in vesicle exocytosis, suggesting that these proteins are essential for normal v-and t-SNARE function (24,25). In mammals, the Munc18a isoform is predominantly expressed in neurons, where it inhibits the association of VAMP1 and SNAP25 with syntaxin 1 (21,26).…”

mentioning

confidence: 99%

Regulation of Insulin-stimulated GLUT4 Translocation by Munc18c in 3T3L1 Adipocytes

Thurmond¹,

Ceresa²,

Okada

et al. 1998

Journal of Biological Chemistry

216

237

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Insulin stimulates glucose transporter (GLUT) 4 vesicle translocation from intracellular storage sites to the plasma membrane in 3T3L1 adipocytes through a VAMP2-and syntaxin 4-dependent mechanism. We have observed that Munc18c, a mammalian homolog of the yeast syntaxin-binding protein n-Sec1p, competed for the binding of VAMP2 to syntaxin 4. Consistent with an inhibitory function for Munc18c, expression of Munc18c, but not the related Munc18b isoform, prevented the insulin stimulation of GLUT4 and IRAP/vp165 translocation to the plasma membrane without any significant effect on GLUT1 trafficking. As expected, overexpressed Munc18c was found to co-immunoprecipitate with syntaxin 4 in the basal state. However, these complexes were found to dissociate upon insulin stimulation. Furthermore, endogenous Munc18c was predominantly localized to the plasma membrane and its distribution was not altered by insulin stimulation. Although expression of enhanced green fluorescent protein-Munc18c primarily resulted in a dispersed cytosolic distribution, co-expression with syntaxin 4 resulted in increased localization to the plasma membrane. Together, these data suggest that Munc18c inhibits the docking/fusion of GLUT4-containing vesicles by blocking the binding of VAMP2 to syntaxin 4. Insulin relieves this inhibition by inducing the dissociation of Munc18c from syntaxin 4 and by sequestering Munc18c to an alternative plasma membrane binding site.The binding of insulin to its heterotetrameric integral-membrane receptor activates its intracellular tyrosine kinase domain and thereby triggers a signaling cascade resulting in the translocation and fusion of intracellular GLUT4 1 isoform-containing vesicles to the plasma membrane (1-3). Although most cell types also constitutively express the GLUT1 isoform at the cell surface, the insulin-stimulated increase in plasma membrane-associated GLUT4 protein accounts for the majority of post-prandial glucose disposal in both muscle and adipose tissue (4).The insulin-stimulated translocation of these GLUT4-containing vesicles has several features in common with the regulated exocytosis pathway of synaptic vesicle trafficking in neurotransmitter release (5). The machinery involved in the regulation of synaptic vesicle priming/docking/fusion entails the pairing of protein complexes in the vesicle compartment (v-SNAREs, for vesicle SNAP receptors) with their cognate receptor complexes at the target membrane (t-SNAREs, for target membrane SNAP receptors). Recently, several of the vand t-SNARE proteins have been identified that specifically participate in the insulin-regulated docking and fusion of GLUT4 vesicles with the adipocyte plasma membrane. GLUT4 vesicles co-purify with both the VAMP2 and VAMP3 v-SNARE isoforms and specific proteolytic cleavage of VAMP2, expression of a dominant-interfering VAMP2 mutant or inhibitory peptides impairs insulin-stimulated GLUT4 translocation (6 -11). In addition, transferrin-horseradish peroxidase ablation of recycling endosomes resulted in a selective loss ...

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The unc‐18 Gene Encodes a Novel Protein Affecting the Kinetics of Acetylcholine Metabolism in the Nematode Caenorhabditis elegans

Cited by 173 publications

References 34 publications

Phosphorylation-regulated axonal dependent transport of syntaxin 1 is mediated by a Kinesin-1 adapter

Phosphorylation-regulated axonal dependent transport of syntaxin 1 is mediated by a Kinesin-1 adapter

A Pivotal Role for Pro-335 in Balancing the Dual Functions of Munc18-1 Domain-3a in Regulated Exocytosis

Regulation of Insulin-stimulated GLUT4 Translocation by Munc18c in 3T3L1 Adipocytes

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