UNC-31 (CAPS) Is Required for Dense-Core Vesicle But Not Synaptic Vesicle Exocytosis in Caenorhabditis elegans

Speese, Sean D.; Petrie, Matt; Schuske, Kim; Ailion, Michael; Ann, Kyoungsook; Iwasaki, Kouichi; Jørgensen, Erik M.; Martin, Thomas F.J.

doi:10.1523/jneurosci.1466-07.2007

Cited by 298 publications

(395 citation statements)

References 69 publications

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“…Using this system of markers, unc-43 lf mutants showed significantly higher-than-wild-type levels of secreted neuropeptide in their coelomocytes (133% of wild type), while constitutive secretion was not significantly different ( Figure 8, A and B). unc-31 null single mutants accumulated neuropeptide in their coelomocytes at 50% of wild type, consistent with the partial block in neuropeptide secretion observed in prior studies Speese et al 2007). However, in unc-43 unc-31 double mutants, secreted neuropeptide in coelomocytes was reduced by 96% relative to unc-43 single mutants ( Figure 8A).…”

supporting

confidence: 89%

A Novel CaM Kinase II Pathway Controls the Location of Neuropeptide Release fromCaenorhabditis elegansMotor Neurons

Hoover

Edwards

et al. 2014

Genetics

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Neurons release neuropeptides via the regulated exocytosis of dense core vesicles (DCVs) to evoke or modulate behaviors. We found that Caenorhabditis elegans motor neurons send most of their DCVs to axons, leaving very few in the cell somas. How neurons maintain this skewed distribution and the extent to which it can be altered to control DCV numbers in axons or to drive release from somas for different behavioral impacts is unknown. Using a forward genetic screen, we identified loss-of-function mutations in UNC-43 (CaM kinase II) that reduce axonal DCV levels by 90% and cell soma/dendrite DCV levels by 80%, leaving small synaptic vesicles largely unaffected. Blocking regulated secretion in unc-43 mutants restored near wild-type axonal levels of DCVs. Time-lapse video microscopy showed no role for CaM kinase II in the transport of DCVs from cell somas to axons. In vivo secretion assays revealed that much of the missing neuropeptide in unc-43 mutants is secreted via a regulated secretory pathway requiring UNC-31 (CAPS) and . DCV cargo levels in unc-43 mutants are similarly low in cell somas and the axon initial segment, indicating that the secretion occurs prior to axonal transport. Genetic pathway analysis suggests that abnormal neuropeptide function contributes to the sluggish basal locomotion rate of unc-43 mutants. These results reveal a novel pathway controlling the location of DCV exocytosis and describe a major new function for CaM kinase II. BOTH neurons and neuroendocrine cells rely on the controlled release of neuropeptides via dense core vesicle (DCV) exocytosis to evoke or modulate behaviors (Scheller and Axel 1984;Kupfermann 1991;T. Liu et al. 2007;Li and Kim 2008). The DCVs in neuroendocrine and PC12 cells are much more abundant and accessible to biochemical and physiological experiments than those in neurons. For example, in chromaffin and pancreatic b-cells (both neuroendocrine cells), DCVs can number in the tens of thousands per cell and can occupy 31 and 12% of the cell volume, respectively (Dean 1973;Plattner et al. 1997). Exploiting these advantages, studies in PC12 and neuroendocrine cells have revealed that DCVs arise from a regulated secretory pathway. The pathway begins in the trans Golgi, where various sorting mechanisms cause regulated secretory proteins, such as neuropeptides and their processing enzymes, to coalesce into vesicles that bud from the trans Golgi to form immature DCVs. Additional sorting of non-DCV cargos away from DCV cargos occurs as DCVs mature through this pathway (Arvan and Castle 1998;Tooze et al. 2001;Borgonovo et al. 2006).DCVs must selectively retain and protect several distinct cargos that have different physical states as they mature. These include the neuropeptide core, which is thought to be in an aggregated state, the neuropeptide-processing enzymes PC-2 convertase and carboxypeptidase E, possibly soluble cargos, and transmembrane cargos.While neurons and neuroendocrine cells share this core pathway for DCV production, neurons have evolved additional...

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supporting

confidence: 89%

A Novel CaM Kinase II Pathway Controls the Location of Neuropeptide Release fromCaenorhabditis elegansMotor Neurons

Hoover

Edwards

et al. 2014

Genetics

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“…In addition, there were no defects in the localization of VenusTUNC-6 in the muscle of the unc-13, unc-25, and unc-31 mutants (Table 2). UNC-13/Munc13, UNC-25/glutamate decarboxylase 1, and UNC-31/CAPS are, respectively, required for acetylcholine (ACh) secretion (Maruyama and Brenner 1991), GABA synthesis ( Jin et al 1999), and neuropeptide secretion (Berwin et al 1998;Speese et al 2007). These findings therefore indicate that traditional neurotransmitters such as ACh, GABA, or neuropeptides are also not involved in the UNC-18 function.…”

Section: Discussionmentioning

confidence: 99%

Genes Required for Cellular UNC-6/Netrin Localization in Caenorhabditis elegans

et al. 2010

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UNC-6/Netrin is an evolutionarily conserved, secretory axon guidance molecule. In Caenorhabditis elegans, UNC-6 provides positional information to the axons of developing neurons, probably by establishing a concentration gradient from the ventral to the dorsal side of the animal. Although the proper localization of UNC-6 is important for accurate neuronal network formation, little is known about how its localization is regulated. Here, to examine the localization mechanism for UNC-6, we generated C. elegans expressing UNC-6 tagged with the fluorescent protein Venus and identified 13 genes, which are involved in the cellular localization of VenusTUNC-6. For example, in unc-51, unc-14, and unc-104 mutants, the neurons showed an abnormal accumulation of VenusTUNC-6 in the cell body and less than normal level of VenusTUNC-6 in the axon. An aberrant accumulation of VenusTUNC-6 in muscle cells was seen in unc-18 and unc-68 mutants. unc-51, unc-14, and unc-104 mutants also showed defects in the guidance of dorso-ventral axons, suggesting that the abnormal localization of UNC-6 disturbed the positional information it provides. We propose that these genes regulate the process of UNC-6 secretion: expression, maturation, sorting, transport, or exocytosis. Our findings provide novel insight into the localization mechanism of the axon guidance molecule UNC-6/ Netrin.

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“…In addition to the pleckstrin homology and C2 domains that have been identified as essential for CAPS function (5,19,51), this study characterizes a functionally important N-terminal phosphorylation domain in CAPS.…”

Section: Discussionmentioning

confidence: 99%

“…CAPS-1 2 (also known as Cadps1) is a 1289-residue protein that reconstitutes Ca 2ϩ -triggered dense-core vesicle exocytosis in permeable neuroendocrine cells at a priming step (2)(3)(4). CAPS is required for secretion of a subset of transmitters in Caenorhabditis elegans (5) and Drosophila melanogaster (6) and for priming dense-core vesicle exocytosis in neuroendocrine cells (7) and synaptic vesicle exocytosis in neurons (8). Vesicle priming reactions are extensively modulated during physiological demand (9), but mechanisms that regulate CAPS function remain to be identified.…”

mentioning

confidence: 99%

CAPS Activity in Priming Vesicle Exocytosis Requires CK2 Phosphorylation

Nojiri

Loyet²,

Klenchin

et al. 2009

Journal of Biological Chemistry

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CAPS (Ca 2؉ -dependent activator protein for secretion) functions in priming Ca 2؉ -dependent vesicle exocytosis, but the regulation of CAPS activity has not been characterized. Here we show that phosphorylation by protein kinase CK2 is required for CAPS activity. Dephosphorylation eliminated CAPS activity in reconstituting Ca 2؉ -dependent vesicle exocytosis in permeable and intact PC12 cells. Ser-5, -6, and -7 and Ser-1281 were identified by mass spectrometry as the major phosphorylation sites in the 1289 residue protein. Ser-5, -6, and -7 but not Ser-1281 to Ala substitutions abolished CAPS activity. Protein kinase CK2 phosphorylated CAPS in vitro at these sites and restored the activity of dephosphorylated CAPS. CK2 is the likely in vivo CAPS protein kinase based on inhibition of phosphorylation by tetrabromo-2-benzotriazole in PC12 cells and by the identity of in vivo and in vitro phosphorylation sites. CAPS phosphorylation by CK2 was constitutive, but the elevation of Ca 2؉ in synaptosomes increased CAPS Ser-5 and -6 dephosphorylation, which terminates CAPS activity. These results identify a functionally important N-terminal phosphorylation site that regulates CAPS activity in priming vesicle exocytosis.Regulated neurotransmitter secretion is central to intercellular communication in the nervous system. Two types of secretory vesicles mediate neurotransmitter release; that is, synaptic vesicles that release transmitters such as glutamate at synapses and dense-core vesicles that release modulatory transmitters and neuropeptides at non-synaptic sites. Both types of secretory vesicles are recruited to docking sites on the plasma membrane where they are primed to a ready release state to undergo fusion in response to Ca 2ϩ elevations. Many of the proteins that mediate the targeting, docking, priming, and Ca 2ϩ -dependent fusion of vesicles with the plasma membrane function in both synaptic vesicle and dense-core vesicle pathways (1). CAPS-1 2 (also known as Cadps1) is a 1289-residue protein that reconstitutes Ca 2ϩ -triggered dense-core vesicle exocytosis in permeable neuroendocrine cells at a priming step (2-4). CAPS is required for secretion of a subset of transmitters in Caenorhabditis elegans (5) and Drosophila melanogaster (6) and for priming dense-core vesicle exocytosis in neuroendocrine cells (7) and synaptic vesicle exocytosis in neurons (8). Vesicle priming reactions are extensively modulated during physiological demand (9), but mechanisms that regulate CAPS function remain to be identified.Reversible protein phosphorylation is a major mechanism for the regulation of cellular processes including vesicle exocytosis. Many proteins that function in evoked vesicle exocytosis are phosphoproteins (10, 11). The neuronal SNARE proteins syntaxin 1A, VAMP-2, and SNAP-25 are phosphorylated by several protein kinases in vitro (12)(13)(14). Protein kinase C and protein kinase A sites on SNAP-25 affect refilling rates and size, respectively, of the primed pool of vesicles in chromaffin cells (15,16). Several SNARE...

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UNC-31 (CAPS) Is Required for Dense-Core Vesicle But Not Synaptic Vesicle Exocytosis in Caenorhabditis elegans

Cited by 298 publications

References 69 publications

A Novel CaM Kinase II Pathway Controls the Location of Neuropeptide Release fromCaenorhabditis elegansMotor Neurons

A Novel CaM Kinase II Pathway Controls the Location of Neuropeptide Release fromCaenorhabditis elegansMotor Neurons

Genes Required for Cellular UNC-6/Netrin Localization in Caenorhabditis elegans

CAPS Activity in Priming Vesicle Exocytosis Requires CK2 Phosphorylation

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