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Ali Moussa HY, Shin KC, Ponraj J, Kim SJ, Ryu JK, Mansour S, Park Y. Requirement of Cholesterol for Calcium-Dependent Vesicle Fusion by Strengthening Synaptotagmin-1-Induced Membrane Bending. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2206823. [PMID: 37058136 DOI: 10.1002/advs.202206823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 02/09/2023] [Indexed: 05/27/2023]
Abstract
Cholesterol is essential for neuronal activity and function. Cholesterol depletion in the plasma membrane impairs synaptic transmission. However, the molecular mechanisms by which cholesterol deficiency leads to defects in vesicle fusion remain poorly understood. Here, it is shown that cholesterol is required for Ca2+ -dependent native vesicle fusion using the in vitro reconstitution of fusion and amperometry to monitor exocytosis in chromaffin cells. Purified native vesicles are crucial for the reconstitution of physiological Ca2+ -dependent fusion, because vesicle-mimicking liposomes fail to reproduce the cholesterol effect. Intriguingly, cholesterol has no effect on the membrane binding of synaptotagmin-1, a Ca2+ sensor for ultrafast fusion. Cholesterol strengthens local membrane deformation and bending induced by synaptotagmin-1, thereby lowering the energy barrier for Ca2+ -dependent fusion to occur. The data provide evidence that cholesterol depletion abolishes Ca2+ -dependent vesicle fusion by disrupting synaptotagmin-1-induced membrane bending, and suggests that cholesterol is an essential lipid regulator for Ca2+ -dependent fusion.
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Affiliation(s)
- Houda Yasmine Ali Moussa
- Neurological Disorders Research Center, Qatar Biomedical Research Institute (QBRI), Hamad Bin Khalifa University (HBKU), Qatar Foundation, Doha, Qatar
| | - Kyung Chul Shin
- Neurological Disorders Research Center, Qatar Biomedical Research Institute (QBRI), Hamad Bin Khalifa University (HBKU), Qatar Foundation, Doha, Qatar
| | | | - Soo Jin Kim
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, 790-784, Republic of Korea
| | - Je-Kyung Ryu
- Department of Physics & Astronomy, Seoul National University. 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea
| | - Said Mansour
- HBKU Core Labs, Hamad Bin Khalifa University (HBKU), Doha, Qatar
| | - Yongsoo Park
- Neurological Disorders Research Center, Qatar Biomedical Research Institute (QBRI), Hamad Bin Khalifa University (HBKU), Qatar Foundation, Doha, Qatar
- College of Health & Life Sciences (CHLS), Hamad Bin Khalifa University (HBKU), Qatar Foundation, Doha, Qatar
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2
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Dugan MP, Ferguson LB, Hertz NT, Chalkley RJ, Burlingame AL, Shokat KM, Parker PJ, Messing RO. Chemical Genetic Identification of PKC Epsilon Substrates in Mouse Brain. Mol Cell Proteomics 2023; 22:100522. [PMID: 36863607 PMCID: PMC10105488 DOI: 10.1016/j.mcpro.2023.100522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 01/25/2023] [Accepted: 02/27/2023] [Indexed: 03/04/2023] Open
Abstract
PKC epsilon (PKCε) plays important roles in behavioral responses to alcohol and in anxiety-like behavior in rodents, making it a potential drug target for reducing alcohol consumption and anxiety. Identifying signals downstream of PKCε could reveal additional targets and strategies for interfering with PKCε signaling. We used a chemical genetic screen combined with mass spectrometry to identify direct substrates of PKCε in mouse brain and validated findings for 39 of them using peptide arrays and in vitro kinase assays. Prioritizing substrates with several public databases such as LINCS-L1000, STRING, GeneFriends, and GeneMAINA predicted interactions between these putative substrates and PKCε and identified substrates associated with alcohol-related behaviors, actions of benzodiazepines, and chronic stress. The 39 substrates could be broadly classified in three functional categories: cytoskeletal regulation, morphogenesis, and synaptic function. These results provide a list of brain PKCε substrates, many of which are novel, for future investigation to determine the role of PKCε signaling in alcohol responses, anxiety, responses to stress, and other related behaviors.
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Affiliation(s)
- Michael P Dugan
- Department of Neuroscience, The University of Texas at Austin, Austin, Texas, USA
| | - Laura B Ferguson
- Department of Neuroscience, The University of Texas at Austin, Austin, Texas, USA
| | - Nicholas T Hertz
- Department of Cellular and Molecular Pharmacology and Howard Hughes Medical Institute at the University of California San Francisco, San Francisco, California, USA; Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
| | - Robert J Chalkley
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
| | - Alma L Burlingame
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
| | - Kevan M Shokat
- Department of Cellular and Molecular Pharmacology and Howard Hughes Medical Institute at the University of California San Francisco, San Francisco, California, USA
| | - Peter J Parker
- The Francis Crick Institute, London, United Kingdom; School of Cancer and Pharmaceutical Sciences, King's College London, London, United Kingdom
| | - Robert O Messing
- Department of Neuroscience, The University of Texas at Austin, Austin, Texas, USA.
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Basiglio CL, Crocenzi FA, Sánchez Pozzi EJ, Roma MG. Oxidative Stress and Localization Status of Hepatocellular Transporters: Impact on Bile Secretion and Role of Signaling Pathways. Antioxid Redox Signal 2021; 35:808-831. [PMID: 34293961 DOI: 10.1089/ars.2021.0021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Significance: Most hepatopathies are primarily or secondarily cholestatic in nature. Oxidative stress (OS) is a frequent trait among them, and impairs the machinery to generate bile by triggering endocytic internalization of hepatocellular transporters, thus causing cholestasis. This is critical, since it leads to accelerated transporter degradation, which could explain the common post-transcriptional downregulation of transporter expression in human cholestatic diseases. Recent Advances: The mechanisms involved in OS-induced hepatocellular transporter internalization are being revealed. Filamentous actin (F-actin) cytoskeleton disorganization and/or detachment of crosslinking actin proteins that afford transporter stability have been characterized as causal factors. Activation of redox-sensitive signaling pathways leading to changes in phosphorylation status of these structures is involved, including Ca2+-mediated activation of "classical" and "novel" protein kinase C (PKC) isoforms or redox-signaling cascades downstream of NADPH oxidase. Critical Issues: Despite the well-known occurrence of hepatocellular transporter internalization in human hepatopathies, the cholestatic implications of this phenomenon have been overlooked. Accordingly, no specific treatment has been established in the clinical practice for its prevention/reversion. Future Directions: We need to improve our knowledge on the pro-oxidant triggering factors and the multiple signaling pathways that mediate this oxidative injury in each cholestatic hepatopathy, so as to envisage tailor-made therapeutic strategies for each case. Meanwhile, administration of antioxidants or heme oxygenase-1 induction to elevate the hepatocellular levels of the endogenous scavenger bilirubin are promising alternatives that need to be re-evaluated and implemented. They may complement current treatments in cholestasis aimed to enhance transcriptional carrier expression, by providing membrane stability to the newly synthesized carriers. Antioxid. Redox Signal. 35, 808-831.
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Affiliation(s)
- Cecilia L Basiglio
- Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas, CONICET, U.N.R., Rosario, Argentina
| | - Fernando A Crocenzi
- Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas, CONICET, U.N.R., Rosario, Argentina
| | - Enrique J Sánchez Pozzi
- Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas, CONICET, U.N.R., Rosario, Argentina
| | - Marcelo G Roma
- Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas, CONICET, U.N.R., Rosario, Argentina
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Rahmani A, Chew YL. Investigating the molecular mechanisms of learning and memory using Caenorhabditis elegans. J Neurochem 2021; 159:417-451. [PMID: 34528252 DOI: 10.1111/jnc.15510] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 08/15/2021] [Accepted: 09/08/2021] [Indexed: 11/30/2022]
Abstract
Learning is an essential biological process for survival since it facilitates behavioural plasticity in response to environmental changes. This process is mediated by a wide variety of genes, mostly expressed in the nervous system. Many studies have extensively explored the molecular and cellular mechanisms underlying learning and memory. This review will focus on the advances gained through the study of the nematode Caenorhabditis elegans. C. elegans provides an excellent system to study learning because of its genetic tractability, in addition to its invariant, compact nervous system (~300 neurons) that is well-characterised at the structural level. Importantly, despite its compact nature, the nematode nervous system possesses a high level of conservation with mammalian systems. These features allow the study of genes within specific sensory-, inter- and motor neurons, facilitating the interrogation of signalling pathways that mediate learning via defined neural circuits. This review will detail how learning and memory can be studied in C. elegans through behavioural paradigms that target distinct sensory modalities. We will also summarise recent studies describing mechanisms through which key molecular and cellular pathways are proposed to affect associative and non-associative forms of learning.
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Affiliation(s)
- Aelon Rahmani
- Flinders Health and Medical Research Institute, Flinders University, Adelaide, South Australia, Australia
| | - Yee Lian Chew
- Flinders Health and Medical Research Institute, Flinders University, Adelaide, South Australia, Australia
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Synapsin Is Required for Dense Core Vesicle Capture and cAMP-Dependent Neuropeptide Release. J Neurosci 2021; 41:4187-4201. [PMID: 33820857 DOI: 10.1523/jneurosci.2631-20.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 02/11/2021] [Accepted: 03/09/2021] [Indexed: 11/21/2022] Open
Abstract
Release of neuropeptides from dense core vesicles (DCVs) is essential for neuromodulation. Compared with the release of small neurotransmitters, much less is known about the mechanisms and proteins contributing to neuropeptide release. By optogenetics, behavioral analysis, electrophysiology, electron microscopy, and live imaging, we show that synapsin SNN-1 is required for cAMP-dependent neuropeptide release in Caenorhabditis elegans hermaphrodite cholinergic motor neurons. In synapsin mutants, behaviors induced by the photoactivated adenylyl cyclase bPAC, which we previously showed to depend on ACh and neuropeptides (Steuer Costa et al., 2017), are altered as in animals with reduced cAMP. Synapsin mutants have slight alterations in synaptic vesicle (SV) distribution; however, a defect in SV mobilization was apparent after channelrhodopsin-based photostimulation. DCVs were largely affected in snn-1 mutants: DCVs were ∼30% reduced in synaptic terminals, and their contents not released following bPAC stimulation. Imaging axonal DCV trafficking, also in genome-engineered mutants in the serine-9 protein kinase A phosphorylation site, showed that synapsin captures DCVs at synapses, making them available for release. SNN-1 colocalized with immobile, captured DCVs. In synapsin deletion mutants, DCVs were more mobile and less likely to be caught at release sites, and in nonphosphorylatable SNN-1B(S9A) mutants, DCVs traffic less and accumulate, likely by enhanced SNN-1 dependent tethering. Our work establishes synapsin as a key mediator of neuropeptide release.SIGNIFICANCE STATEMENT Little is known about mechanisms that regulate how neuropeptide-containing dense core vesicles (DCVs) traffic along the axon, how neuropeptide release is orchestrated, and where it occurs. We found that one of the longest known synaptic proteins, required for the regulation of synaptic vesicles and their storage in nerve terminals, synapsin, is also essential for neuropeptide release. By electrophysiology, imaging, and electron microscopy in Caenorhabditis elegans, we show that synapsin regulates this process by tethering the DCVs to the cytoskeleton in axonal regions where neuropeptides are to be released. Without synapsin, DCVs cannot be captured at the release sites and, consequently, cannot fuse with the membrane, and neuropeptides are not released. We suggest that synapsin fulfills this role also in vertebrates, including humans.
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Jia Q, Sieburth D. Mitochondrial hydrogen peroxide positively regulates neuropeptide secretion during diet-induced activation of the oxidative stress response. Nat Commun 2021; 12:2304. [PMID: 33863916 PMCID: PMC8052458 DOI: 10.1038/s41467-021-22561-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 03/17/2021] [Indexed: 12/17/2022] Open
Abstract
Mitochondria play a pivotal role in the generation of signals coupling metabolism with neurotransmitter release, but a role for mitochondrial-produced ROS in regulating neurosecretion has not been described. Here we show that endogenously produced hydrogen peroxide originating from axonal mitochondria (mtH2O2) functions as a signaling cue to selectively regulate the secretion of a FMRFamide-related neuropeptide (FLP-1) from a pair of interneurons (AIY) in C. elegans. We show that pharmacological or genetic manipulations that increase mtH2O2 levels lead to increased FLP-1 secretion that is dependent upon ROS dismutation, mitochondrial calcium influx, and cysteine sulfenylation of the calcium-independent PKC family member PKC-1. mtH2O2-induced FLP-1 secretion activates the oxidative stress response transcription factor SKN-1/Nrf2 in distal tissues and protects animals from ROS-mediated toxicity. mtH2O2 levels in AIY neurons, FLP-1 secretion and SKN-1 activity are rapidly and reversibly regulated by exposing animals to different bacterial food sources. These results reveal a previously unreported role for mtH2O2 in linking diet-induced changes in mitochondrial homeostasis with neuropeptide secretion.
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Affiliation(s)
- Qi Jia
- PIBBS program, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Derek Sieburth
- Department of Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
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Mass Spectrometric Imaging of Plasma Membrane Lipid Alteration Correlated with Amperometrically Measured Activity-Dependent Plasticity in Exocytosis. Int J Mol Sci 2020; 21:ijms21249519. [PMID: 33327662 PMCID: PMC7765135 DOI: 10.3390/ijms21249519] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 12/11/2020] [Accepted: 12/11/2020] [Indexed: 11/28/2022] Open
Abstract
The mechanism of synaptic plasticity and its link to memory formation are of interest, yet relatively obscure, especially the initial chemical change in the cell membrane following transmitter release. To understand the chemical mechanism of plasticity, we studied how repetitive stimuli regulate certain membrane lipid species to enhance exocytotic release using mass spectrometric imaging. We found that increasing high-curvature lipid species and decreasing low-curvature lipids in the cell membrane favor the formation of a longer-lasting exocytotic fusion pore, resulting in higher release fraction for individual exocytotic events. The lipid changes observed following repetitive stimuli are similar to those after exposure to the cognitive enhancing drug, methylphenidate, examined in a previous study, and offer an interesting point of view regarding the link between plasticity and memory and cognition.
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8
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Plasticity in exocytosis revealed through the effects of repetitive stimuli affect the content of nanometer vesicles and the fraction of transmitter released. Proc Natl Acad Sci U S A 2019; 116:21409-21415. [PMID: 31570594 DOI: 10.1073/pnas.1910859116] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Electrochemical techniques with disk and nano-tip electrodes, together with calcium imaging, were used to examine the effect of short-interval repetitive stimuli on both exocytosis and vesicular content in a model cell line. We show that the number of events decreases markedly with repeated stimuli suggesting a depletion of exocytosis machinery. However, repetitive stimuli induce a more stable fusion pore, leading to an increased amount of neurotransmitter release. In contrast, the total neurotransmitter content inside the vesicles decreases after repetitive stimuli, resulting in a higher average release fraction from each event. We suggest a possible mechanism regarding a link between activity-induced plasticity and fraction of release.
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9
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Roma MG, Barosso IR, Miszczuk GS, Crocenzi FA, Pozzi EJS. Dynamic Localization of Hepatocellular Transporters: Role in Biliary Excretion and Impairment in Cholestasis. Curr Med Chem 2019; 26:1113-1154. [DOI: 10.2174/0929867325666171205153204] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 09/06/2017] [Accepted: 09/07/2017] [Indexed: 12/25/2022]
Abstract
Bile flow generation is driven by the vectorial transfer of osmotically active compounds from sinusoidal blood into a confined space, the bile canaliculus. Hence, localization of hepatocellular transporters relevant to bile formation is crucial for bile secretion. Hepatocellular transporters are localized either in the plasma membrane or in recycling endosomes, from where they can be relocated to the plasma membrane on demand, or endocytosed when the demand decreases. The balance between endocytic internalization/ exocytic targeting to/from this recycling compartment is therefore the main determinant of the hepatic capability to generate bile, and to dispose endo- and xenobiotics. Furthermore, the exacerbated endocytic internalization is a common pathomechanisms in both experimental and human cholestasis; this results in bile secretory failure and, eventually, posttranslational transporter downregulation by increased degradation. This review summarizes the proposed structural mechanisms accounting for this pathological condition (e.g., alteration of function, localization or expression of F-actin or F-actin/transporter cross-linking proteins, and switch to membrane microdomains where they can be readily endocytosed), and the mediators implicated (e.g., triggering of “cholestatic” signaling transduction pathways). Lastly, we discussed the efficacy to counteract the cholestatic failure induced by transporter internalization of a number of therapeutic experimental approaches based upon the use of compounds that trigger exocytic targetting of canalicular transporters (e.g., cAMP, tauroursodeoxycholate). This therapeutics may complement treatments aimed to transcriptionally improve transporter expression, by affording proper localization and membrane stability to the de novo synthesized transporters.
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Affiliation(s)
- Marcelo G. Roma
- Instituto de Fisiologia Experimental (IFISE) - Facultad de Ciencias Bioquimicas y Farmaceuticas (CONICET - U.N.R.), S2002LRL, Rosario, Argentina
| | - Ismael R. Barosso
- Instituto de Fisiologia Experimental (IFISE) - Facultad de Ciencias Bioquimicas y Farmaceuticas (CONICET - U.N.R.), S2002LRL, Rosario, Argentina
| | - Gisel S. Miszczuk
- Instituto de Fisiologia Experimental (IFISE) - Facultad de Ciencias Bioquimicas y Farmaceuticas (CONICET - U.N.R.), S2002LRL, Rosario, Argentina
| | - Fernando A. Crocenzi
- Instituto de Fisiologia Experimental (IFISE) - Facultad de Ciencias Bioquimicas y Farmaceuticas (CONICET - U.N.R.), S2002LRL, Rosario, Argentina
| | - Enrique J. Sánchez Pozzi
- Instituto de Fisiologia Experimental (IFISE) - Facultad de Ciencias Bioquimicas y Farmaceuticas (CONICET - U.N.R.), S2002LRL, Rosario, Argentina
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10
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Trexler AJ, Taraska JW. Regulation of insulin exocytosis by calcium-dependent protein kinase C in beta cells. Cell Calcium 2017; 67:1-10. [PMID: 29029784 DOI: 10.1016/j.ceca.2017.07.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 12/27/2022]
Abstract
The control of insulin release from pancreatic beta cells helps ensure proper blood glucose level, which is critical for human health. Protein kinase C has been shown to be one key control mechanism for this process. After glucose stimulation, calcium influx into beta cells triggers exocytosis of insulin-containing dense-core granules and activates protein kinase C via calcium-dependent phospholipase C-mediated generation of diacylglycerol. Activated protein kinase C potentiates insulin release by enhancing the calcium sensitivity of exocytosis, likely by affecting two main pathways that could be linked: (1) the reorganization of the cortical actin network, and (2) the direct phosphorylation of critical exocytotic proteins such as munc18, SNAP25, and synaptotagmin. Here, we review what is currently known about the molecular mechanisms of protein kinase C action on each of these pathways and how these effects relate to the control of insulin release by exocytosis. We identify remaining challenges in the field and suggest how these challenges might be addressed to advance our understanding of the regulation of insulin release in health and disease.
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Affiliation(s)
- Adam J Trexler
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - Justin W Taraska
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States.
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11
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Hanes CM, D'Amico AE, Ueyama T, Wong AC, Zhang X, Hynes WF, Barroso MM, Cady NC, Trebak M, Saito N, Lennartz MR. Golgi-Associated Protein Kinase C-ε Is Delivered to Phagocytic Cups: Role of Phosphatidylinositol 4-Phosphate. THE JOURNAL OF IMMUNOLOGY 2017; 199:271-277. [PMID: 28539432 DOI: 10.4049/jimmunol.1700243] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 04/28/2017] [Indexed: 11/19/2022]
Abstract
Protein kinase C-ε (PKC-ε) at phagocytic cups mediates the membrane fusion necessary for efficient IgG-mediated phagocytosis. The C1B and pseudosubstrate (εPS) domains are necessary and sufficient for this concentration. C1B binds diacylglycerol; the docking partner for εPS is unknown. Liposome assays revealed that the εPS binds phosphatidylinositol 4-phosphate (PI4P) and PI(3,5)P2 Wortmannin, but not LY294002, inhibits PKC-ε concentration at cups and significantly reduces the rate of phagocytosis. As Wortmannin inhibits PI4 kinase, we hypothesized that PI4P mediates the PKC-ε concentration at cups and the rate of phagocytosis. PKC-ε colocalizes with the trans-Golgi network (TGN) PI4P reporter, P4M, suggesting it is tethered at the TGN. Real-time imaging of GFP-PKC-ε-expressing macrophages revealed a loss of Golgi-associated PKC-ε during phagocytosis, consistent with a Golgi-to-phagosome translocation. Treatment with PIK93, a PI4 kinase inhibitor, reduces PKC-ε at both the TGN and the cup, decreases phagocytosis, and prevents the increase in capacitance that accompanies membrane fusion. Finally, expression of the Golgi-directed PI4P phosphatase, hSac1-K2A, recapitulates the PIK93 phenotype, confirming that Golgi-associated PI4P is critical for efficient phagocytosis. Together these data are consistent with a model in which PKC-ε is tethered to the TGN via an εPS-PI4P interaction. The TGN-associated pool of PKC-ε concentrates at the phagocytic cup where it mediates the membrane fusion necessary for phagocytosis. The novelty of these data lies in the demonstration that εPS binds PI4P and PI(3,5)P2 and that PI4P is necessary for PKC-ε localization at the TGN, its translocation to the phagocytic cup, and the membrane fusion required for efficient Fc [γ] receptor-mediated phagocytosis.
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Affiliation(s)
- Cheryl M Hanes
- Department of Regenerative and Cancer Cell Biology, Albany Medical College, Albany, NY 12208
| | - Anna E D'Amico
- Department of Regenerative and Cancer Cell Biology, Albany Medical College, Albany, NY 12208
| | - Takehiko Ueyama
- Biosignal Research Center, Kobe University, Kobe 657-8501, Japan
| | - Alexander C Wong
- Department of Regenerative and Cancer Cell Biology, Albany Medical College, Albany, NY 12208
| | - Xuexin Zhang
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033
| | - W Frederick Hynes
- College of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, NY 12203; and
| | - Margarida M Barroso
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, NY 12208
| | - Nathaniel C Cady
- College of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, NY 12203; and
| | - Mohamed Trebak
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033
| | - Naoaki Saito
- Biosignal Research Center, Kobe University, Kobe 657-8501, Japan
| | - Michelle R Lennartz
- Department of Regenerative and Cancer Cell Biology, Albany Medical College, Albany, NY 12208;
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12
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Abstract
Exocytosis is a fundamental cellular process whereby secreted molecules are packaged into vesicles that move along cytoskeletal filaments and fuse with the plasma membrane. To function optimally, cells are strongly dependent on precisely controlled delivery of exocytotic cargo. In mammalian cells, microtubules serve as major tracks for vesicle transport by motor proteins, and thus microtubule organization is important for targeted delivery of secretory carriers. Over the years, multiple microtubule-associated and cortical proteins have been discovered that facilitate the interaction between the microtubule plus ends and the cell cortex. In this review, we focus on mammalian protein complexes that have been shown to participate in both cortical microtubule capture and exocytosis, thereby regulating the spatial organization of secretion. These complexes include microtubule plus-end tracking proteins, scaffolding factors, actin-binding proteins, and components of vesicle docking machinery, which together allow efficient coordination of cargo transport and release.
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Affiliation(s)
- Ivar Noordstra
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, Netherlands
| | - Anna Akhmanova
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, Netherlands
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13
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Steuer Costa W, Yu SC, Liewald JF, Gottschalk A. Fast cAMP Modulation of Neurotransmission via Neuropeptide Signals and Vesicle Loading. Curr Biol 2017; 27:495-507. [PMID: 28162892 DOI: 10.1016/j.cub.2016.12.055] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2016] [Revised: 12/06/2016] [Accepted: 12/27/2016] [Indexed: 02/02/2023]
Abstract
Cyclic AMP (cAMP) signaling augments synaptic transmission, but because many targets of cAMP and protein kinase A (PKA) may be involved, mechanisms underlying this pathway remain unclear. To probe this mechanism, we used optogenetic stimulation of cAMP signaling by Beggiatoa-photoactivated adenylyl cyclase (bPAC) in Caenorhabditis elegans motor neurons. Behavioral, electron microscopy (EM), and electrophysiology analyses revealed cAMP effects on both the rate and on quantal size of transmitter release and led to the identification of a neuropeptidergic pathway affecting quantal size. cAMP enhanced synaptic vesicle (SV) fusion by increasing mobilization and docking/priming. cAMP further evoked dense core vesicle (DCV) release of neuropeptides, in contrast to channelrhodopsin (ChR2) stimulation. cAMP-evoked DCV release required UNC-31/Ca2+-dependent activator protein for secretion (CAPS). Thus, DCVs accumulated in unc-31 mutant synapses. bPAC-induced neuropeptide signaling acts presynaptically to enhance vAChT-dependent SV loading with acetylcholine, thus causing increased miniature postsynaptic current amplitudes (mPSCs) and significantly enlarged SVs.
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Affiliation(s)
- Wagner Steuer Costa
- Buchmann Institute for Molecular Life Sciences, Goethe University, Max-von-Laue-Strasse 15, 60438 Frankfurt, Germany; Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University, Max-von-Laue-Strasse 9, 60438 Frankfurt, Germany
| | - Szi-Chieh Yu
- Buchmann Institute for Molecular Life Sciences, Goethe University, Max-von-Laue-Strasse 15, 60438 Frankfurt, Germany; Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University, Max-von-Laue-Strasse 9, 60438 Frankfurt, Germany
| | - Jana F Liewald
- Buchmann Institute for Molecular Life Sciences, Goethe University, Max-von-Laue-Strasse 15, 60438 Frankfurt, Germany; Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University, Max-von-Laue-Strasse 9, 60438 Frankfurt, Germany
| | - Alexander Gottschalk
- Buchmann Institute for Molecular Life Sciences, Goethe University, Max-von-Laue-Strasse 15, 60438 Frankfurt, Germany; Department of Biochemistry, Chemistry and Pharmacy, Institute for Biophysical Chemistry, Goethe University, Max-von-Laue-Strasse 9, 60438 Frankfurt, Germany.
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Obis T, Besalduch N, Hurtado E, Nadal L, Santafe MM, Garcia N, Tomàs M, Priego M, Lanuza MA, Tomàs J. The novel protein kinase C epsilon isoform at the adult neuromuscular synapse: location, regulation by synaptic activity-dependent muscle contraction through TrkB signaling and coupling to ACh release. Mol Brain 2015; 8:8. [PMID: 25761522 PMCID: PMC4348107 DOI: 10.1186/s13041-015-0098-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 01/16/2015] [Indexed: 12/03/2022] Open
Abstract
Background Protein kinase C (PKC) regulates a variety of neural functions, including neurotransmitter release. Although various PKC isoforms can be expressed at the synaptic sites and specific cell distribution may contribute to their functional diversity, little is known about the isoform-specific functions of PKCs in neuromuscular synapse. The present study is designed to examine the location of the novel isoform nPKCε at the neuromuscular junction (NMJ), their synaptic activity-related expression changes, its regulation by muscle contraction, and their possible involvement in acetylcholine release. Results We use immunohistochemistry and confocal microscopy to demonstrate that the novel isoform nPKCε is exclusively located in the motor nerve terminals of the adult rat NMJ. We also report that electrical stimulation of synaptic inputs to the skeletal muscle significantly increased the amount of nPKCε isoform as well as its phosphorylated form in the synaptic membrane, and muscle contraction is necessary for these nPKCε expression changes. The results also demonstrate that synaptic activity-induced muscle contraction promotes changes in presynaptic nPKCε through the brain-derived neurotrophic factor (BDNF)-mediated tyrosine kinase receptor B (TrkB) signaling. Moreover, nPKCε activity results in phosphorylation of the substrate MARCKS involved in actin cytoskeleton remodeling and related with neurotransmission. Finally, blocking nPKCε with a nPKCε-specific translocation inhibitor peptide (εV1-2) strongly reduces phorbol ester-induced ACh release potentiation, which further indicates that nPKCε is involved in neurotransmission. Conclusions Together, these results provide a mechanistic insight into how synaptic activity-induced muscle contraction could regulate the presynaptic action of the nPKCε isoform and suggest that muscle contraction is an important regulatory step in TrkB signaling at the NMJ.
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Affiliation(s)
- Teresa Obis
- Unitat d'Histologia i Neurobiologia (UHN). Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Sant Llorenç 21, 43201, Reus, Spain.
| | - Núria Besalduch
- Unitat d'Histologia i Neurobiologia (UHN). Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Sant Llorenç 21, 43201, Reus, Spain.
| | - Erica Hurtado
- Unitat d'Histologia i Neurobiologia (UHN). Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Sant Llorenç 21, 43201, Reus, Spain.
| | - Laura Nadal
- Unitat d'Histologia i Neurobiologia (UHN). Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Sant Llorenç 21, 43201, Reus, Spain.
| | - Manel M Santafe
- Unitat d'Histologia i Neurobiologia (UHN). Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Sant Llorenç 21, 43201, Reus, Spain.
| | - Neus Garcia
- Unitat d'Histologia i Neurobiologia (UHN). Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Sant Llorenç 21, 43201, Reus, Spain.
| | - Marta Tomàs
- Unitat d'Histologia i Neurobiologia (UHN). Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Sant Llorenç 21, 43201, Reus, Spain.
| | - Mercedes Priego
- Unitat d'Histologia i Neurobiologia (UHN). Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Sant Llorenç 21, 43201, Reus, Spain.
| | - Maria A Lanuza
- Unitat d'Histologia i Neurobiologia (UHN). Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Sant Llorenç 21, 43201, Reus, Spain.
| | - Josep Tomàs
- Unitat d'Histologia i Neurobiologia (UHN). Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Sant Llorenç 21, 43201, Reus, Spain.
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15
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Abstract
Bile acids, synthesized from cholesterol, are known to produce beneficial as well as toxic effects in the liver. The beneficial effects include choleresis, immunomodulation, cell survival, while the toxic effects include cholestasis, apoptosis and cellular toxicity. It is believed that bile acids produce many of these effects by activating intracellular signaling pathways. However, it has been a challenge to relate intracellular signaling to specific and at times opposing effects of bile acids. It is becoming evident that bile acids produce different effects by activating different isoforms of phosphoinositide 3-kinase (PI3K), Protein kinase Cs (PKCs), and mitogen activated protein kinases (MAPK). Thus, the apoptotic effect of bile acids may be mediated via PI3K-110γ, while cytoprotection induce by cAMP-GEF pathway involves activation of PI3K-p110α/β isoforms. Atypical PKCζ may mediate beneficial effects and nPKCε may mediate toxic effects, while cPKCα and nPKCδ may be involved in both beneficial and toxic effects of bile acids. The opposing effects of nPKCδ activation may depend on nPKCδ phosphorylation site(s). Activation of ERK1/2 and JNK1/2 pathway appears to mediate beneficial and toxic effects, respectively, of bile acids. Activation of p38α MAPK and p38β MAPK may mediate choleretic and cholestatic effects, respectively, of bile acids. Future studies clarifying the isoform specific effects on bile formation should allow us to define potential therapeutic targets in the treatment of cholestatic disorders.
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Affiliation(s)
- Mohammed Sawkat Anwer
- Department of Biomedical Sciences, Cummings School of Veterinary Medicine at Tufts University, 200 Westboro Road, North Grafton, MA, USA
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16
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Zhao Z, Webb BT, Jia P, Bigdeli TB, Maher BS, van den Oord E, Bergen SE, Amdur RL, O'Neill FA, Walsh D, Thiselton DL, Chen X, Pato CN, Riley BP, Kendler KS, Fanous AH. Association study of 167 candidate genes for schizophrenia selected by a multi-domain evidence-based prioritization algorithm and neurodevelopmental hypothesis. PLoS One 2013; 8:e67776. [PMID: 23922650 PMCID: PMC3726675 DOI: 10.1371/journal.pone.0067776] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 05/28/2013] [Indexed: 01/06/2023] Open
Abstract
Integrating evidence from multiple domains is useful in prioritizing disease candidate genes for subsequent testing. We ranked all known human genes (n = 3819) under linkage peaks in the Irish Study of High-Density Schizophrenia Families using three different evidence domains: 1) a meta-analysis of microarray gene expression results using the Stanley Brain collection, 2) a schizophrenia protein-protein interaction network, and 3) a systematic literature search. Each gene was assigned a domain-specific p-value and ranked after evaluating the evidence within each domain. For comparison to this ranking process, a large-scale candidate gene hypothesis was also tested by including genes with Gene Ontology terms related to neurodevelopment. Subsequently, genotypes of 3725 SNPs in 167 genes from a custom Illumina iSelect array were used to evaluate the top ranked vs. hypothesis selected genes. Seventy-three genes were both highly ranked and involved in neurodevelopment (category 1) while 42 and 52 genes were exclusive to neurodevelopment (category 2) or highly ranked (category 3), respectively. The most significant associations were observed in genes PRKG1, PRKCE, and CNTN4 but no individual SNPs were significant after correction for multiple testing. Comparison of the approaches showed an excess of significant tests using the hypothesis-driven neurodevelopment category. Random selection of similar sized genes from two independent genome-wide association studies (GWAS) of schizophrenia showed the excess was unlikely by chance. In a further meta-analysis of three GWAS datasets, four candidate SNPs reached nominal significance. Although gene ranking using integrated sources of prior information did not enrich for significant results in the current experiment, gene selection using an a priori hypothesis (neurodevelopment) was superior to random selection. As such, further development of gene ranking strategies using more carefully selected sources of information is warranted.
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Affiliation(s)
- Zhongming Zhao
- Department of Biomedical Informatics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Psychiatry, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Bradley T. Webb
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Center for Biomarker Research and Personalized Medicine, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Peilin Jia
- Department of Biomedical Informatics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - T. Bernard Bigdeli
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Brion S. Maher
- Department of Mental Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Edwin van den Oord
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Center for Biomarker Research and Personalized Medicine, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Sarah E. Bergen
- Psychiatric and Neurodevelopmental Genetics Unit, Center for Human Genetics Research, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Richard L. Amdur
- Washington VA Medical Center, Washington, DC, United States of America
| | | | | | - Dawn L. Thiselton
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Xiangning Chen
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Department of Psychiatry, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Carlos N. Pato
- Department of Psychiatry, Keck School of Medicine of the University of Southern California, Los Angeles, California, United States of America
| | | | - Brien P. Riley
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Department of Psychiatry, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Kenneth S. Kendler
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Department of Psychiatry, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Ayman H. Fanous
- Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Washington VA Medical Center, Washington, DC, United States of America
- Department of Psychiatry, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Department of Psychiatry, Georgetown University School of Medicine, Washington, DC, United States of America
- Department of Psychiatry, Keck School of Medicine of the University of Southern California, Los Angeles, California, United States of America
- * E-mail:
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17
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Schonhoff CM, Webster CRL, Anwer MS. Taurolithocholate-induced MRP2 retrieval involves MARCKS phosphorylation by protein kinase Cϵ in HUH-NTCP Cells. Hepatology 2013; 58:284-92. [PMID: 23424156 PMCID: PMC3681903 DOI: 10.1002/hep.26333] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 02/01/2013] [Indexed: 12/28/2022]
Abstract
UNLABELLED Taurolithocholate (TLC) acutely inhibits the biliary excretion of multidrug-resistant associated protein 2 (Mrp2) substrates by inducing Mrp2 retrieval from the canalicular membrane, whereas cyclic adenosine monophosphate (cAMP) increases plasma membrane (PM)-MRP2. The effect of TLC may be mediated via protein kinase Cϵ (PKCϵ). Myristoylated alanine-rich C kinase substrate (MARCKS) is a membrane-bound F-actin crosslinking protein and is phosphorylated by PKCs. MARCKS phosphorylation has been implicated in endocytosis, and the underlying mechanism appears to be the detachment of phosphorylated myristoylated alanine-rich C kinase substrate (pMARCKS) from the membrane. The aim of the present study was to test the hypothesis that TLC-induced MRP2 retrieval involves PKCϵ-mediated MARCKS phosphorylation. Studies were conducted in HuH7 cells stably transfected with sodium taurocholate cotransporting polypeptide (HuH-NTCP cells) and in rat hepatocytes. TLC increased PM-PKCϵ and decreased PM-MRP2 in both HuH-NTCP cells and hepatocytes. cAMP did not affect PM-PKCϵ and increased PM-MRP2 in these cells. In HuH-NTCP cells, dominant-negative (DN) PKCϵ reversed TLC-induced decreases in PM-MRP2 without affecting cAMP-induced increases in PM-MRP2. TLC, but not cAMP, increased MARCKS phosphorylation in HuH-NTCP cells and hepatocytes. TLC and phorbol myristate acetate increased cytosolic pMARCKS and decreased PM-MARCKS in HuH-NTCP cells. TLC failed to increase MARCKS phosphorylation in HuH-NTCP cells transfected with DN-PKCϵ, and this suggested PKCϵ-mediated phosphorylation of MARCKS by TLC. In HuH-NTCP cells transfected with phosphorylation-deficient MARCKS, TLC failed to increase MARCKS phosphorylation or decrease PM-MRP2. CONCLUSION Taken together, these results support the hypothesis that TLC-induced MRP2 retrieval involves TLC-mediated activation of PKCϵ followed by MARCKS phosphorylation and consequent detachment of MARCKS from the membrane.
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Affiliation(s)
| | - Cynthia R. L. Webster
- Department of Clinical Sciences, Tufts Cummings School of Veterinary Medicine, 200 Westboro Road, North Grafton, MA, USA
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18
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Wood TR, Chow RY, Hanes CM, Zhang X, Kashiwagi K, Shirai Y, Trebak M, Loegering DJ, Saito N, Lennartz MR. PKC-ε pseudosubstrate and catalytic activity are necessary for membrane delivery during IgG-mediated phagocytosis. J Leukoc Biol 2013; 94:109-22. [PMID: 23670290 DOI: 10.1189/jlb.1212634] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
In RAW 264.7 cells, PKC-ε regulates FcγR-mediated phagocytosis. BMDM behave similarly; PKC-ε concentrates at phagosomes and internalization are reduced in PKC-ε⁻/⁻ cells. Two questions were asked: what is the role of PKC-ε? and what domains are necessary for PKC-ε concentration? Function was studied using BMDM and frustrated phagocytosis. On IgG surfaces, PKC-ε⁻/⁻ macrophages spread less than WT. Patch-clamping revealed that the spreading defect is a result of the failure of PKC-ε⁻/⁻ macrophages to add membrane. The defect is specific for FcγR ligation and can be reversed by expression of full-length (but not the isolated RD) PKC-ε in PKC-ε⁻/⁻ BMDM. Thus, PKC-ε function in phagocytosis requires translocation to phagosomes and the catalytic domain. The expression of chimeric PKC molecules in RAW cells identified the εPS as necessary for PKC-ε targeting. When placed into (nonlocalizing) PKC-δ, εPS was sufficient for concentration, albeit to a lesser degree than intact PKC-ε. In contrast, translocation of δ(εPSC1B) resembled that of WT PKC-ε. Thus, εPS and εC1B cooperate for optimal phagosome targeting. Finally, cells expressing εK437W were significantly less phagocytic than their PKC-ε-expressing counterparts, blocked at the pseudopod-extension phase. In summary, we have shown that εPS and εC1B are necessary and sufficient for targeting PKC-ε to phagosomes, where its catalytic activity is required for membrane delivery and pseudopod extension.
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Affiliation(s)
- Tiffany R Wood
- Centers for Cell Biology and Cancer Researchnces, Albany Medical College, Albany, New York, USA
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19
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Trkov S, Stenovec M, Kreft M, Potokar M, Parpura V, Davletov B, Zorec R. Fingolimod--a sphingosine-like molecule inhibits vesicle mobility and secretion in astrocytes. Glia 2012; 60:1406-16. [PMID: 22639011 PMCID: PMC3675637 DOI: 10.1002/glia.22361] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 05/03/2012] [Indexed: 12/22/2022]
Abstract
In the brain, astrocytes signal to the neighboring cells by the release of chemical messengers (gliotransmitters) via regulated exocytosis. Recent studies uncovered a potential role of signaling lipids in modulation of exocytosis. Hence, we investigated whether sphingosine and the structural analog fingolimod/FTY720, a recently introduced therapeutic for multiple sclerosis, affect (i) intracellular vesicle mobility and (ii) vesicle cargo discharge from cultured rat astrocytes. Distinct types of vesicles, peptidergic, glutamatergic, and endosomes/lysosomes, were fluorescently prelabeled by cell transfection with plasmids encoding atrial natriuretic peptide tagged with mutant green fluorescent protein and vesicular glutamate transporter tagged with enhanced green fluorescent protein or by LysoTracker staining, respectively. The confocal and total internal reflection fluorescence microscopies were used to monitor vesicle mobility in the cytoplasm and near the basal plasma membrane, respectively. Sphingosine and FTY720, but not the membrane impermeable lipid analogs, dose-dependently attenuated vesicle mobility in the subcellular regions studied, and significantly inhibited stimulated exocytotic peptide and glutamate release. We conclude that in astrocytes, cell permeable sphingosine-like lipids affect regulated exocytosis by attenuating vesicle mobility, thereby preventing effective vesicle access/interaction with the plasma membrane docking/release sites.
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Affiliation(s)
- Saša Trkov
- Celica d.o.o., Biomedical Center, Technology Park 24, Ljubljana, Slovenia
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20
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Kang N, Won JH, Park YM. Annexin I stimulates insulin secretion through regulation of cytoskeleton and PKC activity. Anim Cells Syst (Seoul) 2010. [DOI: 10.1080/19768354.2009.9647190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Affiliation(s)
- Na‐na Kang
- a Department of Biological Sciences and Institute for Basic Sciences , Sungkyunkwan University , Suwon, 440–746, Korea
| | - Jong Hak Won
- b Department of Pharmacology and Physiology , University of Rochester , Rochester, New York, 14642, USA
| | - Young Min Park
- c Department of Biological Sciences and Institute for Basic Sciences , Sungkyunkwan University , Suwon, 440–746, Korea Phone: Fax: E-mail:
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21
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Abstract
IQGAP1, an effector of CDC42p GTPase, is a widely conserved, multifunctional protein that bundles F-actin through its N-terminus and binds microtubules through its C-terminus to modulate the cell architecture. It has emerged as a potential oncogene associated with diverse human cancers. Therefore, IQGAP1 has been heavily investigated; regardless, its precise cellular function remains unclear. Work from yeast suggests that IQGAP1 plays an important role in directed cell growth, which is a conserved feature crucial to morphogenesis, division axis, and body plan determination. New evidence suggests a conserved role for IQGAP1 in protein synthesis and membrane traffic, which may help to explain the diversity of its cellular functions. Membrane traffic mediates infections by intracellular pathogens and a range of degenerative human diseases arise from dysfunctions in intracellular traffic; thus, elucidating the mechanisms of cellular traffic will be important in order to understand the basis of a wide range of inherited and acquired human diseases. Recent evidence suggests that IQGAP1 plays its role in cell growth through regulating the conserved mTOR pathway. The mTOR signaling cascade has been implicated in membrane traffic and is activated in nearly all human cancers, but clinical response to the mTOR-specific inhibitor rapamycin has been disappointing. Thus, understanding the regulators of this pathway will be crucial in order to identify predictors of rapamycin sensitivity. In this review, I discuss emerging evidence that supports a potential role of IQGAP1 in regulating membrane traffic via regulating the mTOR pathway.
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Affiliation(s)
- Mahasin Osman
- Department of Molecular Pharmacology, Physiology and Biotechnology, Division of Biology and Medicine, Alpert School of Medicine, Brown University, Providence, RI, USA.
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22
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Dysbindin regulates the transcriptional level of myristoylated alanine-rich protein kinase C substrate via the interaction with NF-YB in mice brain. PLoS One 2010; 5:e8773. [PMID: 20098743 PMCID: PMC2808252 DOI: 10.1371/journal.pone.0008773] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Accepted: 12/09/2009] [Indexed: 01/21/2023] Open
Abstract
Background An accumulating body of evidence suggests that Dtnbp1 (Dysbindin) is a key susceptibility gene for schizophrenia. Using the yeast-two-hybrid screening system, we examined the candidate proteins interacting with Dysbindin and revealed one of these candidates to be the transcription factor NF-YB. Methods We employed an immunoprecipitation (IP) assay to demonstrate the Dysbindin-NF-YB interaction. DNA chips were used to screen for altered expression of genes in cells in which Dysbindin or NF-YB was down regulated, while Chromatin IP and Reporter assays were used to confirm the involvement of these genes in transcription of Myristoylated alanine-rich protein kinase C substrate (MARCKS). The sdy mutant mice with a deletion in Dysbindin, which exhibit behavioral abnormalities, and wild-type DBA2J mice were used to investigate MARCKS expression. Results We revealed an interaction between Dysbindin and NF-YB. DNA chips showed that MARCKS expression was increased in both Dysbindin knockdown cells and NF-YB knockdown cells, and Chromatin IP revealed interaction of these proteins at the MARCKS promoter region. Reporter assay results suggested functional involvement of the interaction between Dysbindin and NF-YB in MARCKS transcription levels, via the CCAAT motif which is a NF-YB binding sequence. MARCKS expression was increased in sdy mutant mice when compared to wild-type mice. Conclusions These findings suggest that abnormal expression of MARCKS via dysfunction of Dysbindin might cause impairment of neural transmission and abnormal synaptogenesis. Our results should provide new insights into the mechanisms of neuronal development and the pathogenesis of schizophrenia.
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Xue R, Zhao Y, Su L, Ye F, Chen P. PKC epsilon facilitates recovery of exocytosis after an exhausting stimulation. Pflugers Arch 2009; 458:1137-49. [PMID: 19593582 DOI: 10.1007/s00424-009-0697-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 06/22/2009] [Accepted: 06/26/2009] [Indexed: 01/18/2023]
Abstract
It has been well documented that protein kinase Cs (PKCs) play multifaceted roles in regulating exocytosis of neurotransmitters and hormones. But the isoform-specific PKC effects are still poorly elucidated mainly because of the large variety of PKC isoforms and the dubious specificity of the commonly used pharmacological agents. In the present study, based on overexpression of wild-type or dominant negative PKC epsilon, we demonstrate in neuroendocrine PC12 cells that PKC epsilon, but not PKC alpha, facilitates recovery of exocytosis after an exhausting stimulation. Specifically, PKC epsilon mediates fast recovery of the extent of exocytosis in a phosphatidylinositol biphosphate-dependent manner, likely through enhancing the rate of vesicle delivery and reorganization of cortical actin network. In addition, PKC epsilon promotes fast recovery of vesicle release kinetics that is slowed after a strong stimulation. These experimental results may suggest a PKC-dependent mechanism relevant to the short-term plasticity of exocytosis in both neurons and neuroendocrine cells.
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Affiliation(s)
- Renhao Xue
- Division of Bioengineering, Nanyang Technological University, Singapore, 637457, Singapore
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24
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Hikima T, Araki R, Ishizuka T, Yawo H. beta-Phorbol ester-induced enhancement of exocytosis in large mossy fiber boutons of mouse hippocampus. J Physiol Sci 2009; 59:263-74. [PMID: 19340534 PMCID: PMC10717968 DOI: 10.1007/s12576-009-0031-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Accepted: 02/10/2009] [Indexed: 11/28/2022]
Abstract
beta-Phorbol esters (BPE), synthetic analogues of diacylglycerol (DAG), induce the potentiation of transmission in many kinds of synapses through activating the C(1) domain-containing receptors. However, their effects on synaptic vesicle exocytosis have not yet been investigated. Here, we evaluated the vesicular exocytosis directly from individual large mossy fiber boutons (LMFBs) in hippocampal slices from transgenic mice that selectively express synaptopHluorin (SpH). We found that the activity-dependent increment of SpH fluorescence (DeltaSpH) was enhanced by 4beta-phorbol 12,13-diacetate (PDAc), one of the BPEs, without influencing the recycled component of SpH. These PDAc effects on DeltaSpH were almost completely inhibited by staurosporine, a non-selective antagonist of protein kinases. However, intermittent synaptic transmission was still potentiated through a staurosporine-resistant mechanism. The staurosporine-sensitive cascade may facilitate the vesicle replenishment, thus maintaining the fidelity of transmission at a high level during repetitive firing of the presynaptic neuron.
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Affiliation(s)
- Takuya Hikima
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, 2-1 Seiryo-machi, Aoba-ku, Sendai, 980-8575 Japan
- Tohoku University Basic and Translational Research Centre for Global Brain Science, Sendai, 980-8575 Japan
| | - Rikita Araki
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, 2-1 Seiryo-machi, Aoba-ku, Sendai, 980-8575 Japan
| | - Toru Ishizuka
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, 2-1 Seiryo-machi, Aoba-ku, Sendai, 980-8575 Japan
| | - Hiromu Yawo
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, 2-1 Seiryo-machi, Aoba-ku, Sendai, 980-8575 Japan
- Tohoku University Basic and Translational Research Centre for Global Brain Science, Sendai, 980-8575 Japan
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Park Y, Kim KT. Dominant role of lipid rafts L-type calcium channel in activity-dependent potentiation of large dense-core vesicle exocytosis. J Neurochem 2009; 110:520-9. [PMID: 19457106 DOI: 10.1111/j.1471-4159.2009.06148.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Calcium influx triggers exocytosis by promoting vesicle fusion with the plasma membrane. However, different subtypes of voltage-gated calcium channel (VGCC) have distinct roles in exocytosis. We previously reported that repetitive stimulation induces activity-dependent potentiation (ADP) which represents the increase of neurotransmitter release. Here, we show that L-type VGCC have a dominant role in ADP of large dense-core vesicle (LDCV) exocytosis. Repetitive stimulation activating VGCC can induce ADP, whereas activation of bradykinin (BK) G protein-coupled receptors or purinergic P2X cation channels can not. L-type VGCC has the dominant role in ADP of LDCV exocytosis by regulating Protein Kinase C (PKC)-epsilon translocation and phosphorylation of myristoylated alanine-rich C kinase substrate (MARCKS), a target molecule of PKC-epsilon. We provide evidence that L-type VGCC, PKC-epsilon, and MARCKS, but not Q-type VGCC, are selectively located in lipid rafts. Also, PKC-epsilon translocation induced by L-type VGCC activation occurs in lipid rafts. Disruption of lipid rafts abolishes ADP of LDCV exocytosis and changes the fusion pore kinetics without affecting the first stimulation-induced exocytosis, showing that lipid rafts are involved in the potentiation process. Taken together, we suggest that L-type VGCC in lipid rafts selectively mediates ADP of LDCV exocytosis by regulating PKC-epsilon translocation and MARCKS phosphorylation.
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Affiliation(s)
- Yongsoo Park
- Department of Life Science, Pohang University of Science and Technology, Korea
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26
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Involvement of PKCα in PMA-induced facilitation of exocytosis and vesicle fusion in PC12 cells. Biochem Biophys Res Commun 2009; 380:371-6. [DOI: 10.1016/j.bbrc.2009.01.105] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Accepted: 01/12/2009] [Indexed: 11/18/2022]
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Park Y, Kim KT. Short-term plasticity of small synaptic vesicle (SSV) and large dense-core vesicle (LDCV) exocytosis. Cell Signal 2009; 21:1465-70. [PMID: 19249357 DOI: 10.1016/j.cellsig.2009.02.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Accepted: 02/17/2009] [Indexed: 10/21/2022]
Abstract
Synaptic plasticity results from changes in the strength of synaptic transmission upon repetitive stimulation. The amount of neurotransmitter released from presynaptic terminals can regulate short-term plasticity that lasts for a few minutes. This review focuses on short-term plasticity of small synaptic vesicle (SSV) and large dense-core vesicle (LDCV) exocytosis. Whereas SSVs contain classical neurotransmitters and activate ion channels, LDCVs contain neuropeptides and hormones which primarily activate G protein-coupled receptors (GPCRs). Thus, LDCV exocytosis is mainly associated with modulation of synaptic activity and cannot induce synaptic activity by itself. As in SSV exocytosis, repetitive stimulation leads to short-term enhancement of LDCV exocytosis: i.e., activity-dependent potentiation (ADP) which represents potentiation of neurotransmitter release. Short-term plasticity of SSV exocytosis results from Ca2+ accumulation, but ADP of LDCV exocytosis does not. Here, we review the signaling mechanisms and differences of short-term plasticity in exocytotic processes of SSV and LDCV.
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Affiliation(s)
- Yongsoo Park
- Department of Life Science, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea
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28
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Abstract
Beta-cells in pancreatic islets form complex syncytia. Sufficient cell-to-cell electrical coupling seems to ensure coordinated depolarization pattern and insulin release that can be further modulated by rich innervation. The complex structure and coordinated action develop after birth during fast proliferation of the endocrine tissue. These emergent properties can be lost due to various reasons later in life and can lead to glucose intolerance and diabetes mellitus. Pancreas slice is a novel method of choice to study the physiology of beta-cells still embedded in their normal cellulo-social context. I present major advantages, list drawbacks and provide an overview on recent advances in our understanding of the physiology of beta-cells using the pancreas slice approach.
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Affiliation(s)
- M Rupnik
- Faculty of Medicine, Institute of Physiology, University of Maribor, Maribor, Slovenia.
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29
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Park YS, Ha Choi Y, Park CH, Kim KT. Nongenomic glucocorticoid effects on activity-dependent potentiation of catecholamine release in chromaffin cells. Endocrinology 2008; 149:4921-7. [PMID: 18583423 PMCID: PMC2734489 DOI: 10.1210/en.2007-1798] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Adrenal medulla chromaffin cells are neuroendocrine and modified sympathetic ganglion cells. Catecholamines released from chromaffin cells mediate the fight-or-flight response or alert reaction against dangerous conditions. Here we report that short-term treatment with glucocorticoids, released from adrenal cortex cells in response to chronic stress, inhibits activity-dependent potentiation (ADP) of catecholamine release. First, short-term treatment with dexamethasone (DEX), a synthetic glucocorticoid, reduces ADP in a concentration-dependent manner (IC50 324.2+/-54.5 nM). The inhibitory effect of DEX is not reversed by RU-486 treatment, suggesting that the rapid inhibitory effect of DEX on ADP of catecholamine release is independent of glucocorticoid receptors. Second, DEX treatment reduces the frequency of fusion between vesicles and plasma membrane without affecting calcium influx. DEX disrupts activity-induced vesicle translocation and F-actin disassembly, thereby leading to inhibition of the vesicle fusion frequency. Third, we provide evidence that DEX reduces F-actin disassembly via inhibiting phosphorylation and translocation of myristoylated alanine-rich C kinase substrate and its upstream kinase protein kinase Cepsilon. Altogether, we suggest that glucocorticoids inhibit ADP of catecholamine release by decreasing myristoylated alanine-rich C kinase substrate phosphorylation, which inhibits F-actin disassembly and vesicle translocation.
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Affiliation(s)
- Yong-Soo Park
- Department of Life Science, Pohang University of Science and Technology, San 31, Hyoja Dong, Pohang 790-784, Republic of Korea
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30
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Abstract
Major advances in understanding regulated mucin secretion from airway goblet cells have been made in the past decade in the areas of pharmacology and basic cell biology. For instance, it is now appreciated that nucleotide agonists acting locally through P2Y purinoceptors on apical membranes of surface goblet cells provide the major regulatory system for mucin secretion. Similarly, Clara cells, the primary secretory cell in the mouse airways (and human small airways), are now recognized as major mucin-secreting cells. In Clara cells, the relative lack of staining for mucosubstances reflects essentially equal baseline rates of mucin synthesis and secretion, with little to no accumulation of mucin granules in storage pools. During mucous metaplasia induced under inflammatory conditions, mucin synthesis is massively upregulated in Clara cells, and stored mucin granules come to dominate the secretory cell phenotype. More importantly, we have seen a transition in the past few years from a pharmacological focus on regulated mucin secretion to a more molecular mechanistic focus that has great promise going forward. In part, these advances are occurring through the use of well-differentiated primary human bronchial epithelial cell cultures, but recent work in mouse models perhaps has had the most important impact. Emerging data from Munc13-2- and synaptotagmin 2-deficient mouse models represent the first direct, molecular-level manipulations of proteins involved in regulated secretory cell mucin secretion. These new data indicate that Munc13-2 is responsible for regulating a baseline mucin secretory pathway in the airways and is not essential for purinergic agonist-induced mucin secretion. In contrast, synaptotagmin 2, a fast Ca2+ sensor for the SNARE complex, is essential for regulated secretion. Interestingly, these early results suggest that there are two pathways for excocytic mucin release from goblet cells.
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Affiliation(s)
- C William Davis
- Cystic Fibrosis/Pulmonary Research & Treatment Center, University of North Carolina, Chapel Hill, NC 27599-7248, USA.
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31
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Zhang E, Xue R, Soo J, Chen P. Effects of phorbol ester on vesicle dynamics as revealed by total internal reflection fluorescence microscopy. Pflugers Arch 2008; 457:211-22. [PMID: 18343946 DOI: 10.1007/s00424-008-0485-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 02/14/2008] [Accepted: 02/27/2008] [Indexed: 11/24/2022]
Abstract
Exocytosis of neurotransmitter or hormone-filled vesicles is a highly dynamic process regulated by various proteins and lipids. As mainly revealed indirectly by the electrophysiological methods, exocytosis is believed to involve multiple kinetic steps in which vesicles transit from one state to another. Using total internal reflection fluorescence microscopy which enables direct visualization of individual vesicles, we developed an analytical framework to track and analyze vesicle dynamics. We demonstrated that all subplasmalemmal vesicles generally undergo constant and caged Brownian motion. And they can be classified into three populations that differ in their motion characteristics and fusion competence. Furthermore, we showed that these vesicle pools are differentially modulated by phorbol-12-myristate-13-acetate, a phorbol ester analog to endogenous diacylglycerol, through both protein-kinase-C-dependent and -independent pathways.
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Affiliation(s)
- Enming Zhang
- Division of Bioengineering, Nanyang Technological University, Singapore 637457, Singapore
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32
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Huang L, Cheng HC, Isom R, Chen CS, Levine RA, Pauli BU. Protein kinase Cepsilon mediates polymeric fibronectin assembly on the surface of blood-borne rat breast cancer cells to promote pulmonary metastasis. J Biol Chem 2008; 283:7616-27. [PMID: 18184652 DOI: 10.1074/jbc.m705839200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Malignant breast cancer cells that have entered the blood circulation from primary mammary fat pad tumors or are grown in end-over-end suspension culture assemble a characteristic, multi-globular polymeric fibronectin (polyFn) coat on their surfaces. Surface polyFn is critical for pulmonary metastasis, presumably by facilitating lung vascular arrest via endothelial dipeptidylpeptidase IV (CD26). Here, we show that cell-surface polyFn assembly is initiated by the state of suspension, is dependent upon the synthesis and secretion of cellular Fn, and is augmented in a dose- and time-dependent manner by plasma Fn. PolyFn assembly is regulated by protein kinase Cepsilon (PKCepsilon), which translocates rapidly and in increasing amounts from the cytosol to the plasma membrane and is phosphorylated. PolyFn assembly is impeded by select inhibitors of this kinase, i.e. bisindolylmaleimide I, Ro-32-0432, Gö6983, and Rottlerin, by the phorbol 12-myristate 13-acetate-mediated and time-dependent loss of PKCepsilon protein and decreased plasma membrane translocation, and more specifically, by stable transfection of lung-metastatic MTF7L breast cancer cells with small interfering RNA-PKCepsilon and dominant-negative PKCepsilon constructs (e.g. RD-PKCepsilon). The inability to assemble a cell surface-associated polyFn coat by knockdown of endogenous Fn or PKCepsilon impedes cancer cells from metastasis to the lungs. The present studies identify a novel regulatory mechanism for polyFn assembly on blood-borne breast cancer cells and depict its effect on pulmonary metastasis.
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Affiliation(s)
- Lynn Huang
- Cancer Cell Biology Laboratories, Department of Molecular Medicine, Cornell University, Ithaca, New York 14853, USA
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Choi BH, Kim W, Wang QC, Kim DC, Tan SN, Yong JWH, Kim KT, Yoon HS. Kinetin riboside preferentially induces apoptosis by modulating Bcl-2 family proteins and caspase-3 in cancer cells. Cancer Lett 2007; 261:37-45. [PMID: 18162289 DOI: 10.1016/j.canlet.2007.11.014] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2007] [Revised: 10/31/2007] [Accepted: 11/05/2007] [Indexed: 01/05/2023]
Abstract
Here, we demonstrate that kinetin riboside (KR), a cytokinin analog, induces apoptosis in HeLa and mouse melanoma B16F-10 cells. KR disrupted the mitochondrial membrane potential and induced the release of cytochrome c and activation of caspase-3. Bad were upregulated while Bcl-2 was down-regulated under KR exposure. A tumor growth in mice was dramatically suppressed by KR. In contrast, human skin fibroblast CCL-116 and bovine primary fibroblast cells show resistances to KR and no significant changes in Bad, Bcl-X(L,) and cleaved PARP were observed. Our data suggest that KR selectively induces apoptosis in cancer cells through the classical mitochondria dependent apoptosis pathway.
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Affiliation(s)
- Bo-Hwa Choi
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637511, Singapore
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Ehre C, Zhu Y, Abdullah LH, Olsen J, Nakayama KI, Nakayama K, Messing RO, Davis CW. nPKCepsilon, a P2Y2-R downstream effector in regulated mucin secretion from airway goblet cells. Am J Physiol Cell Physiol 2007; 293:C1445-54. [PMID: 17728398 DOI: 10.1152/ajpcell.00051.2007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Airway goblet cell mucin secretion is controlled by agonist activation of P2Y(2) purinoceptors, acting through Gq/PLC, inositol-1,4,5-trisphosphate (IP(3)), diacylglycerol, Ca(2+) and protein kinase C (PKC). Previously, we showed that SPOC1 cells express cPKCalpha, nPKCdelta, nPKCepsilon, and nPKCeta; of these, only nPKCdelta translocated to the membrane in correlation with mucin secretion (Abdullah LH, Bundy JT, Ehre C, Davis CW. Am J Physiol Lung Physiol 285: L149-L160, 2003). We have verified these results and pursued the identity of the PKC effector isoform by testing the effects of altered PKC expression on regulated mucin release using SPOC1 cell and mouse models. SPOC1 cells overexpressing cPKCalpha, nPKCdelta, and nPKCeta had the same levels of ATPgammaS- and phorbol-1,2-myristate-13-acetate (PMA)-stimulated mucin secretion as the levels in empty retroviral vector expressing cells. Secretagogue-induced mucin secretion was elevated only in cells overexpressing nPKCepsilon (14.6 and 23.5%, for ATPgammaS and PMA). Similarly, only SPOC1 cells infected with a kinase-deficient nPKCepsilon exhibited the expected diminution of stimulated mucin secretion, relative to wild-type (WT) isoform overexpression. ATPgammaS-stimulated mucin secretion from isolated, perfused mouse tracheas was diminished in P2Y(2)-R null mice by 82% relative to WT mice, demonstrating the utility of mouse models in studies of regulated mucin secretion. Littermate WT and nPKCdelta knockout (KO) mice had nearly identical levels of stimulated mucin secretion, whereas mucin release was nearly abolished in nPKCepsilon KO mice relative to its WT littermates. We conclude that nPKCepsilon is the effector isoform downstream of P2Y(2)-R activation in the goblet cell secretory response. The translocation of nPKCdelta observed in activated cells is likely not related to mucin secretion but to some other aspect of goblet cell biology.
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Affiliation(s)
- Camille Ehre
- CCystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina 27599-7248, USA
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35
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Abstract
The Goto Kakizaki (GK) rat is a widely used animal model to study defective glucose-stimulated insulin release in type-2 diabetes (T2D). As in T2D patients, the expression of several proteins involved in Ca(2+)-dependent exocytosis of insulin-containing large dense-core vesicles is dysregulated in this model. So far, a defect in late steps of insulin secretion could not be demonstrated. To resolve this apparent contradiction, we studied Ca(2+)-secretion coupling of healthy and GK rat beta cells in acute pancreatic tissue slices by assessing exocytosis with high time-resolution membrane capacitance measurements. We found that beta cells of GK rats respond to glucose stimulation with a normal increase in the cytosolic Ca(2+) concentration. During trains of depolarizing pulses, the secretory activity from GK rat beta cells was defective in spite of upregulated cell size and doubled voltage-activated Ca(2+) currents. In GK rat beta cells, evoked Ca(2+) entry was significantly less efficient in triggering release than in nondiabetic controls. This impairment was neither due to a decrease of functional vesicle pool sizes nor due to different kinetics of pool refilling. Strong stimulation with two successive trains of depolarizing pulses led to a prominent activity-dependent facilitation of release in GK rat beta cells, whereas secretion in controls was unaffected. Broad-spectrum inhibition of PKC sensitized Ca(2+)-dependent exocytosis, whereas it prevented the activity-dependent facilitation in GK rat beta cells. We conclude that a decrease in the sensitivity of the GK rat beta-cell to depolarization-evoked Ca(2+) influx is involved in defective glucose-stimulated insulin secretion. Furthermore, we discuss a role for constitutively increased activity of one or more PKC isoenzymes in diabetic rat beta cells.
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Affiliation(s)
- Tobias Rose
- European Neuroscience Institute-Göttingen, 37073 Göttingen, Germany
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36
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Bauer CS, Woolley RJ, Teschemacher AG, Seward EP. Potentiation of exocytosis by phospholipase C-coupled G-protein-coupled receptors requires the priming protein Munc13-1. J Neurosci 2007; 27:212-9. [PMID: 17202488 PMCID: PMC6672273 DOI: 10.1523/jneurosci.4201-06.2007] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The vesicle priming protein Munc13-1 is regulated by diacylglycerol (DAG) and is therefore hypothesized to play a role in the control of neurotransmitter release by phospholipase C (PLC)-coupled receptors. We combined voltage-clamp recordings of voltage-gated Ca2+ channels (VGCCs) and high-resolution capacitance measurements to investigate the mechanism of receptor-mediated modulation of exocytosis in bovine chromaffin cells. Activation of endogenous H1 G(q)-protein-coupled receptors (G(q)PCRs) by histamine potentiated stimulus-coupled secretion despite concurrently inhibiting Ca2+ influx through VGCCs. Histamine increased the size of the readily releasable pool of vesicles and in particular a subpool of fusion-competent vesicles localized in close proximity to VGCCs. Pharmacological characterization showed that potentiation of exocytosis depended on the activation of PLC but not protein kinase C. Overexpression of wild-type Munc13-1 by adenoviral infection had no effect on histamine-induced potentiation per se, whereas DAG-insensitive Munc13-1(H567K) completely abolished it. This is the first endogenous mammalian G(q)PCR signaling pathway identified that engages Munc13-1 to increase stimulus-coupled secretion by recruiting vesicles to the immediately releasable pool. G(q)PCRs are therefore able to control exocytosis at the level of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complex formation to produce rapid, short-term potentiation of the secretory output of neurons and endocrine cells.
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Affiliation(s)
- Claudia S. Bauer
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom, and
| | - Robert J. Woolley
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom, and
| | - Anja G. Teschemacher
- Department of Pharmacology, University of Bristol, Bristol BS3 1TD, United Kingdom
| | - Elizabeth P. Seward
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom, and
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