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PKC-1 regulates secretion of neuropeptides

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Abstract

The secretion of neurotransmitters and neuropeptides is mediated by distinct organelles—synaptic vesicles (SVs) and dense-core vesicles (DCVs), respectively. Relatively little is known about the factors that differentially regulate SV and DCV secretion. Here we show that protein kinase C-1 (PKC-1), which is most similar to the vertebrate PKC η and ε isoforms, regulates exocytosis of DCVs in Caenorhabditis elegans motor neurons. Mutants lacking PCK-1 activity had delayed paralysis induced by the acetylcholinesterase inhibitor aldicarb, whereas mutants with increased PKC-1 activity had more rapid aldicarb-induced paralysis. Imaging and electrophysiological assays indicated that SV release occurred normally in pkc-1 mutants. By contrast, genetic analysis of aldicarb responses and imaging of fluorescently tagged neuropeptides indicated that mutants lacking PKC-1 had reduced neuropeptide secretion. Similar neuropeptide secretion defects were found in mutants lacking unc-31 (encoding the protein CAPS) or unc-13 (encoding Munc13). These results suggest that PKC-1 selectively regulates DCV release from neurons.

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Figure 1: pkc-1 encodes an isoform of PKCη and PKCε.
Figure 2: Agonist- and voltage-activated muscle responses were normal in pkc-1 mutants.
Figure 3: Expression pattern and site of action of PKC-1.
Figure 4: The effects of phorbol esters on aldicarb responses are mediated in part by PKC-1.
Figure 5: Stimulus-evoked and spontaneous EPSC responses of pkc-1 mutant synapses.
Figure 6: Genetic interactions between PKC-1 and the neuropeptide pathway.
Figure 7: NLP-21 neuropeptide secretion in pkc-1 mutants.
Figure 8: Dense-core vesicle distribution in axons of pkc-1 mutants.

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  • 10 December 2006

    Affiliation changed for two authors

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Acknowledgements

We thank the C. elegans stock center for strains, and I. Mori and Y. Okochi for nj3 mutants, for pYOS49 and for sharing unpublished results. We thank members of the Kaplan lab for advice and for critically reading the manuscript, Q. Ch'ng for reagents and for writing the coelomocyte fluorescence software and J. Dittman for developing punctal fluorescence analysis software. This work was supported by postdoctoral fellowships from the Damon Runyon Cancer Research Foundation (D.S.), the US National Institutes of Health (1F32NS10310) and the American Cancer Society (PF-98-065-01-DDC) (J.M.) and by research grants from the US National Institutes of Health (J.K.).

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Correspondence to Joshua M Kaplan.

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Supplementary information

Supplementary Fig. 1

To verify that ACh activated currents were cholinergic, d-Tubocurare, an acetylcholine receptor antagonist, was shown to block the response to pressure ejection of acetylcholine onto body wall muscles in both (a) wild type (n = 2) and (b) pkc-1(nj3) (n = 2). (PDF 682 kb)

Supplementary Fig. 2

The aldicarb resistance of unc-31 CAPS mutants was not enhanced by either egl-3 PC2 or egl-21 CPE mutants. (PDF 324 kb)

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Sieburth, D., Madison, J. & Kaplan, J. PKC-1 regulates secretion of neuropeptides. Nat Neurosci 10, 49–57 (2007). https://doi.org/10.1038/nn1810

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