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Cui X, Wang S, Huang Y, Ding X, Wang Z, Zheng L, Bi Y, Ge F, Zhu L, Yuan M, Yalovsky S, Fu Y. Arabidopsis SYP121 acts as an ROP2 effector in the regulation of root hair tip growth. MOLECULAR PLANT 2022; 15:1008-1023. [PMID: 35488430 DOI: 10.1016/j.molp.2022.04.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 04/04/2022] [Accepted: 04/25/2022] [Indexed: 06/14/2023]
Abstract
Tip growth is an extreme form of polarized cell expansion that occurs in all eukaryotic kingdoms to generate highly elongated tubular cells with specialized functions, including fungal hyphae, animal neurons, plant pollen tubes, and root hairs (RHs). RHs are tubular structures that protrude from the root epidermis to facilitate water and nutrient uptake, microbial interactions, and plant anchorage. RH tip growth requires polarized vesicle targeting and active exocytosis at apical growth sites. However, how apical exocytosis is spatially and temporally controlled during tip growth remains elusive. Here, we report that the Qa-Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) SYP121 acts as an effector of Rho of Plants 2 (ROP2), mediating the regulation of RH tip growth. We show that active ROP2 promotes SYP121 targeting to the apical plasma membrane. Moreover, ROP2 directly interacts with SYP121 and promotes the interaction between SYP121 and the R-SNARE VAMP722 to form a SNARE complex, probably by facilitating the release of the Sec1/Munc18 protein SEC11, which suppresses the function of SYP121. Thus, the ROP2-SYP121 pathway facilitates exocytic trafficking during RH tip growth. Our study uncovers a direct link between an ROP GTPase and vesicular trafficking and a new mechanism for the control of apical exocytosis, whereby ROP GTPase signaling spatially regulates SNARE complex assembly and the polar distribution of a Q-SNARE.
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Affiliation(s)
- Xiankui Cui
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Shuwei Wang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yaohui Huang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Xuening Ding
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Zirong Wang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Lidan Zheng
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yujing Bi
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Fanghui Ge
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Lei Zhu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China; Joint Laboratory for International Cooperation in Crop Molecular Breeding, Ministry of Education, China Agricultural University, Beijing 100193, China
| | - Ming Yuan
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Shaul Yalovsky
- Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ying Fu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China; Joint Laboratory for International Cooperation in Crop Molecular Breeding, Ministry of Education, China Agricultural University, Beijing 100193, China.
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Vaidyanathan VV, Binz T. Ability of human SNAP-23 to generate high molecular weight SDS-resistant ternary SNARE complexes is influenced by C-terminal coil content. Biochem Biophys Rep 2021; 28:101150. [PMID: 34703905 PMCID: PMC8524102 DOI: 10.1016/j.bbrep.2021.101150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 08/23/2021] [Accepted: 09/21/2021] [Indexed: 11/26/2022] Open
Abstract
Using in vitro protein complex formation assay, ability of SNAP-25 isoforms to generate SDS-resistant ternary SNARE complexes with Syntaxin-1 and VAMP-2 was investigated. Major SNAP-25 family proteins were found to generate heat-resistant ternary complexes with varying efficiency. Compared to human SNAP-25, its non-neuronal counterparts SNAP-23 and SNAP-29 formed lower amounts of ternary complexes. Changing Pro182 in human SNAP-23 to Arg182 (SNAP-23 P182R) improved its ability to bind partners and form complexes. In silico analysis of C-terminal helical content in various SNAP-25 family members showed that except human SNAP-23, all others displayed secondary α-helical conformation. We also report that human SNAP-29 is resistant to the proteolytic action of botulinum neurotoxin A even when applied at large concentration. Human SNAP-23 forms reduced amounts of ternary SNARE complexes than human SNAP-25. SNAP-25 family proteins show varying levels of secondary structure at the C-terminus. C-terminal coil content influences neurotoxin sensitivity and ability to form stable ternary SNARE complexes.
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Affiliation(s)
| | - Thomas Binz
- Institute of Cellular Biochemistry, Hannover Medical School, Hannover, 30625, Germany
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3
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Boehm S. Meet Our Editorial Board Member. Curr Neuropharmacol 2020. [PMCID: PMC8033984 DOI: 10.2174/1570159x1902201231152908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Stefan Boehm
- Department of Neurophysiology and Neuropharmacology Center for Physiology and Pharmacology Medical University of Vienna Schwarzspanierstrasse 17/I, A-1090 Vienna, Austria
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Cassiano C, Eletto D, Tosco A, Riccio R, Monti MC, Casapullo A. Determining the Effect of Pterostilbene on Insulin Secretion Using Chemoproteomics. Molecules 2020; 25:E2885. [PMID: 32585851 PMCID: PMC7356329 DOI: 10.3390/molecules25122885] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/18/2020] [Accepted: 06/22/2020] [Indexed: 12/13/2022] Open
Abstract
Pterostilbene, the 3,5-dimethoxy derivative of resveratrol, is a well-known polyphenolic compound, mainly found in blueberries, grapevines, and Pterocarpus marsupium heartwood, which has recently attracted a great deal of attention due to its wide bio-pharmacological profile. Moreover, pterostilbene is more lipophilic than resveratrol, with a consequently better bioavailability and a more interesting therapeutic potential. In this work, a chemoproteomic approach, based on affinity chromatography, was applied on pterostilbene in the attempt to identify the biological targets responsible for its bioactivity. On this basis, syntaxins, a group of proteins involved in the formation of SNARE complexes mediating vesicles exocytosis, were selected among the most interesting pterostilbene interactors. In vitro and in cell assays gave evidence of the pterostilbene ability to reduce insulin secretion on glucose-stimulated pancreatic beta cells, opening the way to potential applications of pterostilbene as a supplement in the care of insulin-dependent metabolic disorders.
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Affiliation(s)
- Chiara Cassiano
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, Italy; (C.C.); (D.E.); (A.T.); (R.R.)
- Department of Pharmacy, University of Naples “Federico II”, Via D., Montesano 49, 80131 Naples, Italy
| | - Daniela Eletto
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, Italy; (C.C.); (D.E.); (A.T.); (R.R.)
| | - Alessandra Tosco
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, Italy; (C.C.); (D.E.); (A.T.); (R.R.)
| | - Raffaele Riccio
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, Italy; (C.C.); (D.E.); (A.T.); (R.R.)
| | - Maria Chiara Monti
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, Italy; (C.C.); (D.E.); (A.T.); (R.R.)
| | - Agostino Casapullo
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, Italy; (C.C.); (D.E.); (A.T.); (R.R.)
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5
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Ding JJ, Zou RX, He HM, Lou ZY, Xu Y, Wang HL. Pb inhibits hippocampal synaptic transmission via cyclin-dependent kinase-5 dependent Synapsin 1 phosphorylation. Toxicol Lett 2018; 296:125-131. [PMID: 30121340 DOI: 10.1016/j.toxlet.2018.08.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 08/12/2018] [Accepted: 08/14/2018] [Indexed: 12/18/2022]
Abstract
Lead (Pb) exposure impairs the nervous system, of which the injury of cognitive development is obvious. But the mechanism of Pb induced disorders of neuro-transmission remain elusive. In this study, primary hippocampal neurons were exposed to Pb at the dosage of 5 μM from days in vitro (DIV) 3 to DIV14 and the electrophysiological recordings were performed at DIV14. Sprague-Dawley (SD) rat pups were exposed to Pb from parturition to weaning indirectly from their mothers whose drinking water containing 250 ppm Pb, then directly exposed to Pb at the dosage of 250 ppm from postnatal day (PND) 21 to PND30. The results showed that Pb significantly decreased the frequency of both miniature excitatory postsynaptic current (mEPSC) and miniature inhibitory postsynaptic current (mIPSC) in cultured hippocampal neurons. Paird-pulse facilitation (PPF) recordings showed there was significant increase in Pb-exposed group. The increase of the magnitude of PPF (the ratio of second to first response amplitude) further confirmed that Pb reduced presynaptic neuro-transmission. By transmission electron microscope, it found that Pb disarranged presynaptic vesicles distribution and decreased the density of presynaptic vesicles. Moreover, it was interestingly found that phosphorylation of Synapsin1, which was phosphorylated by CDK5, has been decreased upon Pb exposure. With the treatment of R-Roscovitine (Ro), an inhibitor of CDK5, it was detected that Pb induced mEPSC and mIPSC frequency reduction have been reversed. Together, our results suggested that Pb disrupted the distribution of synaptic vesicles and impaired the neurotransmitter release, which was dependent on the phosphorylation level of Synapsin 1 via CDK5. This study will help for elucidation of environmental Pb-induced neuronal disorders.
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Affiliation(s)
- Jin-Jun Ding
- School of Food Science and Engineering, Hefei University of Technology, Hefei, Anhui 230009, PR China
| | - Rong-Xin Zou
- School of Food Science and Engineering, Hefei University of Technology, Hefei, Anhui 230009, PR China
| | - Hui-Ming He
- School of Food Science and Engineering, Hefei University of Technology, Hefei, Anhui 230009, PR China
| | - Zhi-Yi Lou
- School of Food Science and Engineering, Hefei University of Technology, Hefei, Anhui 230009, PR China
| | - Yi Xu
- School of Food Science and Engineering, Hefei University of Technology, Hefei, Anhui 230009, PR China
| | - Hui-Li Wang
- School of Food Science and Engineering, Hefei University of Technology, Hefei, Anhui 230009, PR China.
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Codding SJ, Marty N, Abdullah N, Johnson CP. Dysferlin Binds SNAREs (Soluble N-Ethylmaleimide-sensitive Factor (NSF) Attachment Protein Receptors) and Stimulates Membrane Fusion in a Calcium-sensitive Manner. J Biol Chem 2016; 291:14575-84. [PMID: 27226605 DOI: 10.1074/jbc.m116.727016] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Indexed: 11/06/2022] Open
Abstract
Resealing of tears in the sarcolemma of myofibers is a necessary step in the repair of muscle tissue. Recent work suggests a critical role for dysferlin in the membrane repair process and that mutations in dysferlin are responsible for limb girdle muscular dystrophy 2B and Miyoshi myopathy. Beyond membrane repair, dysferlin has been linked to SNARE-mediated exocytotic events including cytokine release and acid sphingomyelinase secretion. However, it is unclear whether dysferlin regulates SNARE-mediated membrane fusion. In this study we demonstrate a direct interaction between dysferlin and the SNARE proteins syntaxin 4 and SNAP-23. In addition, analysis of FRET and in vitro reconstituted lipid mixing assays indicate that dysferlin accelerates syntaxin 4/SNAP-23 heterodimer formation and SNARE-mediated lipid mixing in a calcium-sensitive manner. These results support a function for dysferlin as a calcium-sensing SNARE effector for membrane fusion events.
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Affiliation(s)
- Sara J Codding
- From the Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331
| | - Naomi Marty
- From the Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331
| | - Nazish Abdullah
- From the Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331
| | - Colin P Johnson
- From the Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331
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7
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Striz AC, Tuma PL. The GTP-bound and Sumoylated Form of the rab17 Small Molecular Weight GTPase Selectively Binds Syntaxin 2 in Polarized Hepatic WIF-B Cells. J Biol Chem 2016; 291:9721-32. [PMID: 26957544 DOI: 10.1074/jbc.m116.723353] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Indexed: 12/29/2022] Open
Abstract
A major focus for our laboratory is identifying the molecules and mechanisms that regulate polarized apical protein sorting in hepatocytes, the major epithelial cells of the liver. These trafficking pathways are regulated, in part, by small molecular weight rab GTPases. We chose to investigate rab17, whose expression is restricted to polarized epithelial cells, is enriched in liver, and has been implicated in regulating basolateral to apical transcytosis. To initiate our studies, we generated three recombinant adenoviruses expressing wild type, constitutively active (GTP bound), or dominant-negative (GDP bound) rab17. Immunoblotting revealed rab17 immunoreactive species at 25 kDa (the predicted rab17 molecular mass) and 40 kDa. We determined that mono-sumoylation of the 25-kDa rab17 is responsible for the shift in molecular mass, and that rab17 prenylation is required for sumoylation. We further determined that sumoylation selectively promotes interactions with syntaxin 2 (but not syntaxins 3 or 4) and that these interactions are nucleotide dependent. Furthermore, a K68R-mutated rab17 led to the redistribution of syntaxin 2 and 5' nucleotidase from the apical membrane to subapical puncta, whereas multidrug resistance protein 2 distributions were not changed. Together these data are consistent with the proposed role of rab17 in vesicle fusion with the apical plasma membrane and further implicate sumoylation as an important mediator of protein-protein interactions. The selectivity in syntaxin binding and apical protein redistribution further suggests that rab17 and syntaxin 2 mediate fusion of transcytotic vesicles at the apical surface.
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Affiliation(s)
- Anneliese C Striz
- From the Department of Biology, The Catholic University of America, Washington, D. C. 20064
| | - Pamela L Tuma
- From the Department of Biology, The Catholic University of America, Washington, D. C. 20064
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Gao J, Hirata M, Mizokami A, Zhao J, Takahashi I, Takeuchi H, Hirata M. Differential role of SNAP-25 phosphorylation by protein kinases A and C in the regulation of SNARE complex formation and exocytosis in PC12 cells. Cell Signal 2015; 28:425-437. [PMID: 26721188 DOI: 10.1016/j.cellsig.2015.12.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Revised: 12/15/2015] [Accepted: 12/21/2015] [Indexed: 11/30/2022]
Abstract
The final step of regulated exocytosis, membrane fusion, is mediated by formation of the SNARE complex by syntaxin, SNAP-25 (synaptosomal-associated protein of 25 kDa), and VAMP (vesicle-associated membrane protein). Phosphorylation of SNARE and accessory proteins contributes to regulation of exocytosis. We previously identified residues of SNAP-25 phosphorylated by protein kinase A (PKA) and PKC. However, the physiological role of SNAP-25 phosphorylation in exocytosis, in particular with regard to SNARE complex formation, has remained elusive. SNARE complex formation by purified recombinant SNAP-25, syntaxin-1, and VAMP-2 in vitro was inhibited or promoted as a result of the phosphorylation at Thr(138) by PKA or at Ser(187) by PKC, respectively. SNARE complex formation in intact PC12 cells was similarly inhibited by forskolin (activator of PKA) and promoted by phorbol 12-myristate 13-acetate (PMA, activator of PKC). Noradrenaline secretion from PC12 cells induced by a high K(+) concentration was enhanced by forskolin or PMA. Stable depletion of SNAP-25 inhibited high-K(+)-induced noradrenaline secretion. Forced expression of WT SNAP-25 restored the secretory response of the SNAP-25-depleted cells to high-K(+), and this response was enhanced by forskolin or PMA. Expression of the nonphosphorylatable T138A or S187A mutants of SNAP-25 similarly rescued the secretory response to high-K(+), but the augmentation of this response by forskolin was more pronounced in the cells expressing SNAP-25 (T138A) than in those expressing SNAP-25 (WT), whereas that by PMA was less pronounced in those expressing SNAP-25 (S187A). Our results thus suggest that SNAP-25 phosphorylation by PKA or PKC contributes differentially to the control of exocytosis in PC12 cells by regulating SNARE complex formation.
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Affiliation(s)
- Jing Gao
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Makiko Hirata
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan; Section of Orthodontics, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Akiko Mizokami
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Jin Zhao
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Ichiro Takahashi
- Section of Orthodontics, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Hiroshi Takeuchi
- Division of Applied Pharmacology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580, Japan
| | - Masato Hirata
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
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Yang Y, Kim J, Kim HY, Ryoo N, Lee S, Kim Y, Rhim H, Shin YK. Amyloid-β Oligomers May Impair SNARE-Mediated Exocytosis by Direct Binding to Syntaxin 1a. Cell Rep 2015; 12:1244-51. [PMID: 26279571 DOI: 10.1016/j.celrep.2015.07.044] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 06/17/2015] [Accepted: 07/22/2015] [Indexed: 12/28/2022] Open
Abstract
Alzheimer's disease (AD) is closely associated with synaptic dysfunction, and thus current treatments often aim to stimulate neurotransmission to improve cognitive impairment. Whereas the formation of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex is essential for synaptic transmission, the correlation between SNAREs and AD neuropathology is unknown. Here, we report that intracellular amyloid-β (Aβ) oligomers directly inhibit SNARE-mediated exocytosis by impairing SNARE complex formation. We observe abnormal reduction of SNARE complex levels in the brains of APP/PS1 transgenic (TG) mice compared to age-matched wild-types. We demonstrate that Aβ oligomers block SNARE complex assembly through the direct interaction with a target membrane (t)-SNARE syntaxin 1a in vitro. Furthermore, the results of the in vitro single-vesicle content-mixing assay reveal that Aβ oligomers inhibit SNARE-mediated fusion pores. Thus, our study identifies a potential molecular mechanism by which intracellular Aβ oligomers hamper SNARE-mediated exocytosis, likely leading to AD-associated synaptic dysfunctions.
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Affiliation(s)
- Yoosoo Yang
- Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Seoul 136-791, Republic of Korea
| | - Jaewook Kim
- Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Seoul 136-791, Republic of Korea; Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - Hye Yun Kim
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 136-791, Republic of Korea
| | - Nayeon Ryoo
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 136-791, Republic of Korea
| | - Sejin Lee
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 136-791, Republic of Korea
| | - YoungSoo Kim
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 136-791, Republic of Korea
| | - Hyewhon Rhim
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 136-791, Republic of Korea; Department of Neuroscience, University of Science and Technology (UST), Daejon 305-333, Republic of Korea.
| | - Yeon-Kyun Shin
- Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Seoul 136-791, Republic of Korea; Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA 50011, USA.
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Nagano K, Takeuchi H, Gao J, Mori Y, Otani T, Wang D, Hirata M. Tomosyn is a novel Akt substrate mediating insulin-dependent GLUT4 exocytosis. Int J Biochem Cell Biol 2015; 62:62-71. [PMID: 25725259 DOI: 10.1016/j.biocel.2015.02.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2014] [Revised: 01/31/2015] [Accepted: 02/18/2015] [Indexed: 12/28/2022]
Abstract
Insulin triggers glucose uptake into skeletal muscle and adipose tissues by gaining the available number of glucose transporter 4 (GLUT4) on the cell surface. GLUT4-loaded vesicles are targeted to plasma membrane from the intracellular reservoir through multiple trafficking and fusion processes that are mainly regulated by Akt. However, it is still largely unknown how GLUT4 expression in the cell surface is promoted by insulin. In the present study, we identified tomosyn at Ser-783 as a possible Akt-substrate motif and examined whether the phosphorylation at Ser-783 is involved in the regulation of GLUT4 expression. Both Akt1 and Akt2 phosphorylated the wild-type tomosyn, but not the mutant tomosyn in which Ser-783 was replaced with Ala. Phosphorylation of tomosyn at Ser-783 was also observed in the intact cells by insulin stimulation, which was blocked by PI3K inhibitor, LY294002. In vitro pull-down assay showed that phosphorylation of tomosyn at Ser-783 by Akt inhibited the interaction with syntaxin 4. Insulin stimulation increased GLUT4 in the cell surface of CHO-K1 cells to promote glucose uptake, however exogenous expression of the mutant tomosyn attenuated the increase by insulin. These results suggest that Ser-783 of tomosyn is a target of Akt and is implicated in the interaction with syntaxin 4.
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Affiliation(s)
- Koki Nagano
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Hiroshi Takeuchi
- Division of Applied Pharmacology, Kyushu Dental University, Kitakyushu 803-8580, Japan.
| | - Jing Gao
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Yoshihide Mori
- Section of Oral and Maxillofacial Surgery, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Takahito Otani
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - DaGuang Wang
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Masato Hirata
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
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11
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Wetzell BB, Muller MM, Cobuzzi JL, Hurwitz ZE, DeCicco-Skinner K, Riley AL. Effect of age on methylphenidate-induced conditioned taste avoidance and related BDNF/TrkB signaling in the insular cortex of the rat. Psychopharmacology (Berl) 2014; 231:1493-501. [PMID: 24563186 DOI: 10.1007/s00213-014-3500-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 02/07/2014] [Indexed: 12/29/2022]
Abstract
RATIONALE Drug use and abuse is thought to be a function of the balance between its rewarding and aversive effects, such that the rewarding effects increase the likelihood of use while the drug's dissociable aversive effects limit it. Adolescents exhibit a shift in this balance toward reward, which may ultimately lead to increased use. Importantly, recent work shows that adolescents are also protected from the aversive effects of many abusable drugs as measured by conditioned taste avoidance (CTA). However, such effects of methylphenidate (MPH, widely prescribed to adolescents with ADHD) have not been characterized. OBJECTIVES The effect of age on MPH-induced CTA was assessed. In addition, MPH-induced changes in brain-derived neurotrophic factor (BDNF) activity in the insular cortex (IC) and central nucleus of the amygdala (CeA), known to be important to CTA, were examined and related to CTAs in adolescents and adults. METHODS CTAs induced by MPH (0, 10, 18, and 32 mg/kg) were assessed in adolescent (n = 34) and adult (n = 33) male Sprague Dawley rats. Following MPH CTA, IC and CeA tissue was probed for differences in BDNF and tropomyosin-related kinase receptor-B (TrkB) using Western blots. RESULTS Blunted expression of MPH CTA was observed in the adolescents versus adults, which correlated with generally attenuated adolescent BDNF/TrkB activity in the IC, but the drug effects ran contrary to the expression of CTA. CONCLUSIONS Adolescents are protected from the aversive effects of MPH versus adults, but further work is needed to characterize the possible involvement of BDNF/TrkB.
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Affiliation(s)
- B Bradley Wetzell
- Psychopharmacology Laboratory, Department of Psychology, American University, 4400 Massachusetts Avenue NW, Washington, DC, 20016, USA,
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12
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Kosiorek M, Zylinska L, Zablocki K, Pikula S. Calcineurin/NFAT signaling represses genes Vamp1 and Vamp2 via PMCA-dependent mechanism during dopamine secretion by Pheochromocytoma cells. PLoS One 2014; 9:e92176. [PMID: 24667359 PMCID: PMC3965406 DOI: 10.1371/journal.pone.0092176] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 02/19/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Plasma membrane Ca(2+)-ATPases (PMCA) extrude Ca(2+) ions out of the cell and contribute to generation of calcium oscillations. Calcium signaling is crucial for transcriptional regulation of dopamine secretion by neuroendocrine PC12 cells. Low resting [Ca(2+)]c in PC12 cells is maintained mainly by two Ca(2+)-ATPases, PMCA2 and PMCA3. Recently, we found that Ca(2+) dependent phosphatase calcineurin was excessively activated under conditions of experimental downregulation of PMCA2 or PMCA3. Thus, the aim of this study was to explain if, via modulation of the Ca(2+)/calcineurin-dependent nuclear factor of activated T cells (NFAT) pathway, PMCA2 and PMCA3 affect intracellular signaling in pheochromocytoma/neuronal cells/PC12 cells. Secondly, we tested whether this might influence dopamine secretion by PC12 cells. RESULTS PMCA2- and PMCA3-deficient cells displayed profound decrease in dopamine secretion accompanied by a permanent increase in [Ca(2+)]c. Reduction in secretion might result from changes in NFAT signaling, following altered PMCA pattern. Consequently, activation of NFAT1 and NFAT3 transcription factors was observed in PMCA2- or PMCA3-deficient cells. Furthermore, chromatin immunoprecipitation assay indicated that NFATs could be involved in repression of Vamp genes encoding vesicle associated membrane proteins (VAMP). CONCLUSIONS PMCA2 and PMCA3 are crucial for dopamine secretion in PC12 cells. Reduction in PMCA2 or PMCA3 led to calcium-dependent activation of calcineurin/NFAT signaling and, in consequence, to repression of the Vamp gene and deterioration of the SNARE complex formation in PC12 cells.
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Affiliation(s)
- Michalina Kosiorek
- Department of Biochemistry, Nencki Institute of Experimental Biology, PAS, Warsaw, Poland
- Laboratory of Neurogenetics, Department of Neurodegenerative Disorders, Mossakowski Medical Research Centre PAS, Warsaw, Poland
- * E-mail: (MK); (SP)
| | - Ludmila Zylinska
- Department of Molecular Neurochemistry, Medical University, Lodz, Poland
| | - Krzysztof Zablocki
- Department of Biochemistry, Nencki Institute of Experimental Biology, PAS, Warsaw, Poland
| | - Slawomir Pikula
- Department of Biochemistry, Nencki Institute of Experimental Biology, PAS, Warsaw, Poland
- * E-mail: (MK); (SP)
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13
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Meng J, Dolly JO, Wang J. Selective cleavage of SNAREs in sensory neurons unveils protein complexes mediating peptide exocytosis triggered by different stimuli. Mol Neurobiol 2014; 50:574-88. [PMID: 24604356 DOI: 10.1007/s12035-014-8665-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 02/20/2014] [Indexed: 11/28/2022]
Abstract
Oligomerisation of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes is required for synaptic vesicle fusion and neurotransmitter release. How these regulate the release of pain peptides elicited by different stimuli from sensory neurons has not been established. Herein, K(+) depolarization was found to induce multiple sodium dodecyl sulfate (SDS)-resistant SNARE complexes in sensory neurons exposed to botulinum neurotoxins (BoNTs), with molecular weights ranging from 104-288 k (large) to 38-104 k (small). Isoform 1 of vesicle-associated membrane protein 1 (VAMP 1) assembled into stable complexes upon depolarisation and was required for the participation of intact synaptosome-associated protein of relative molecular mass 25 k (SNAP-25) or BoNT/A-truncated form (SNAP-25A) in the large functional and small inactive SDS-resistant SNARE complexes. Cleaving VAMP 1 decreased SNAP-25A in the functional complexes to a much greater extent than the remaining intact SNAP-25. Syntaxin 1 proved essential for the incorporation of intact and SNAP-25A into the large complexes. Truncation of syntaxin 1 by BoNT/C1 caused /A- and/or /C1-truncated SNAP-25 to appear in non-functional complexes and blocked the release of calcitonin gene-related peptide (CGRP) elicited by capsaicin, ionomycin, thapsigargin or K(+) depolarization. Only the latter two were susceptible to /A. Inhibition of CGRP release by BoNT/A was reversed by capsaicin and/or ionomycin, an effect overcome by BoNT/C1. Unlike BoNT/B, BoNT/D cleaved VAMP 1 in addition to 2 and 3 in rat sensory neurons and blocked both CGRP and substance P release. Thus, unlike SNAP-25, syntaxin 1 and VAMP 1 are more suitable targets to abolish functional SNARE complexes and pain peptide release evoked by any stimuli.
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Affiliation(s)
- Jianghui Meng
- International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Ireland
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14
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Lalioti VS, Vergarajauregui S, Villasante A, Pulido D, Sandoval IV. C6orf89 encodes three distinct HDAC enhancers that function in the nucleolus, the golgi and the midbody. J Cell Physiol 2013; 228:1907-21. [PMID: 23460338 DOI: 10.1002/jcp.24355] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 02/12/2013] [Indexed: 11/06/2022]
Abstract
We report here that C6orf89, which encodes a protein that interacts with bombesin receptor subtype-3 and accelerates cell cycle progression and wound repair in human bronchial epithelial cells (Liu et al., 2011, PLoS ONE 6: e23072), encodes one soluble and two type II membrane proteins that function as histone deacetylases (HDAC) enhancers. Soluble 34/64sp is selectively targeted to the nucleolus and is retained in nucleolar organiser regions (NORs) in mitotic cells. Nucleolar 34/64sp is integrated into the ribosomal gene transcription machinery, colocalises and coimmunoprecipitates with the Pol I transcription factor UBF, and undergoes a dramatic relocalisation to the nucleolus upon the arrest of rDNA transcription, protein synthesis and PI3K/mTORC2 signalling. Membrane 42/116mp localises to the Golgi and the midbody, and its controlled ectopic expression provokes the disruption of the Golgi cisternae and hinders the separation of daughter cells and the completion of mitosis. The latter effect is also produced by the microinjection of an affinity-purified amfion antibody. The identification of C60rf89 as a gene that encodes three distinct proteins with the capacity to enhance the activity of histone deacetylases (HDACs) in the nucleolus, the Golgi and the midbody provides new information regarding the components of the acetylome and their capacity to interact with different functional groups in the cell.
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Affiliation(s)
- Vasiliki S Lalioti
- Centro de Biología Molecular Severo Ochoa, CSIC, Universidad Autónoma de Madrid, Departamento Biología Celular e Inmunología, Cantoblanco, Madrid, Spain.
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15
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Zhang Z, Takeuchi H, Gao J, Wang D, James DJ, Martin TFJ, Hirata M. PRIP (phospholipase C-related but catalytically inactive protein) inhibits exocytosis by direct interactions with syntaxin 1 and SNAP-25 through its C2 domain. J Biol Chem 2013; 288:7769-7780. [PMID: 23341457 DOI: 10.1074/jbc.m112.419317] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Membrane fusion for exocytosis is mediated by SNAREs, forming trans-ternary complexes to bridge vesicle and target membranes. There is an array of accessory proteins that directly interact with and regulate SNARE proteins. PRIP (phospholipase C-related but catalytically inactive protein) is likely one of these proteins; PRIP, consisting of multiple functional modules including pleckstrin homology and C2 domains, inhibited exocytosis, probably via the binding to membrane phosphoinositides through the pleckstrin homology domain. However, the roles of the C2 domain have not yet been investigated. In this study, we found that the C2 domain of PRIP directly interacts with syntaxin 1 and SNAP-25 but not with VAMP2. The C2 domain promoted PRIP to co-localize with syntaxin 1 and SNAP-25 in PC12 cells. The binding profile of the C2 domain to SNAP-25 was comparable with that of synaptotagmin I, and PRIP inhibited synaptotagmin I in binding to SNAP-25 and syntaxin 1. It was also shown that the C2 domain was required for PRIP to suppress SDS-resistant ternary SNARE complex formation and inhibit high K(+)-induced noradrenalin release from PC12 cells. These results suggest that PRIP inhibits regulated exocytosis through the interaction of its C2 domain with syntaxin 1 and SNAP-25, potentially competing with other SNARE-binding, C2 domain-containing accessory proteins such as synaptotagmin I and by directly inhibiting trans-SNARE complex formation.
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Affiliation(s)
- Zhao Zhang
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan; Stomatological Hospital of Hebei Medical University, Shijiazhuang 050017, China
| | - Hiroshi Takeuchi
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan; Division of Applied Pharmacology, Kyushu Dental College, Kitakyushu 803-8580, Japan.
| | - Jing Gao
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - DaGuang Wang
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Declan J James
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Thomas F J Martin
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Masato Hirata
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan.
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16
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Oh E, Kalwat MA, Kim MJ, Verhage M, Thurmond DC. Munc18-1 regulates first-phase insulin release by promoting granule docking to multiple syntaxin isoforms. J Biol Chem 2012; 287:25821-33. [PMID: 22685295 DOI: 10.1074/jbc.m112.361501] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Attenuated levels of the Sec1/Munc18 (SM) protein Munc18-1 in human islet β-cells is coincident with type 2 diabetes, although how Munc18-1 facilitates insulin secretion remains enigmatic. Herein, using conventional Munc18-1(+/-) and β-cell specific Munc18-1(-/-) knock-out mice, we establish that Munc18-1 is required for the first phase of insulin secretion. Conversely, human islets expressing elevated levels of Munc18-1 elicited significant potentiation of only first-phase insulin release. Insulin secretory changes positively correlated with insulin granule number at the plasma membrane: Munc18-1-deficient cells lacked 35% of the normal component of pre-docked insulin secretory granules, whereas cells with elevated levels of Munc18-1 exhibited a ∼20% increase in pre-docked granule number. Pre-docked syntaxin 1-based SNARE complexes bound by Munc18-1 were detected in β-cell lysates but, surprisingly, were reduced by elevation of Munc18-1 levels. Paradoxically, elevated Munc18-1 levels coincided with increased binding of syntaxin 4 to VAMP2 at the plasma membrane. Accordingly, syntaxin 4 was a requisite for Munc18-1 potentiation of insulin release. Munc18c, the cognate SM isoform for syntaxin 4, failed to bind SNARE complexes. Given that Munc18-1 does not pair with syntaxin 4, these data suggest a novel indirect role for Munc18-1 in facilitating syntaxin 4-mediated granule pre-docking to support first-phase insulin exocytosis.
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Affiliation(s)
- Eunjin Oh
- Department of Pediatrics, Herman B. Wells Center, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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17
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Lippé R. Deciphering novel host-herpesvirus interactions by virion proteomics. Front Microbiol 2012; 3:181. [PMID: 22783234 PMCID: PMC3390586 DOI: 10.3389/fmicb.2012.00181] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 04/27/2012] [Indexed: 12/15/2022] Open
Abstract
Over the years, a vast array of information concerning the interactions of viruses with their hosts has been collected. However, recent advances in proteomics and other system biology techniques suggest these interactions are far more complex than anticipated. One particularly interesting and novel aspect is the analysis of cellular proteins incorporated into mature virions. Though sometimes considered purification contaminants in the past, their repeated detection by different laboratories suggests that a number of these proteins are bona fide viral components, some of which likely contribute to the viral life cycles. The present mini review focuses on cellular proteins detected in herpesviruses. It highlights the common cellular functions of these proteins, their potential implications for host–pathogen interactions, discusses technical limitations, the need for complementing methods and probes potential future research avenues.
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Affiliation(s)
- Roger Lippé
- Department of Pathology and Cell biology, University of Montreal Montreal, QC, Canada
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18
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Khoo KHP, Able AJ, Chataway TK, Able JA. Preliminary characterisation of two early meiotic wheat proteins after identification through 2D gel electrophoresis proteomics. FUNCTIONAL PLANT BIOLOGY : FPB 2012; 39:222-235. [PMID: 32480776 DOI: 10.1071/fp11253] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 12/24/2011] [Indexed: 06/11/2023]
Abstract
Various genetic-based approaches including mutant population screens, microarray analyses, cloning and transgenesis have broadened our knowledge of gene function during meiosis in plants. Nonetheless, these genetic tools are not without inherent limitations. One alternative approach to studying plant meiosis, especially in polyploids such as Triticum aestivum L. (bread wheat), is proteomics. However, protein-based approaches using proteomics have seldom been described, with only two attempts at studying early plant meiosis reported. Here, we report the investigation of early bread wheat meiosis using proteomics. Five differentially expressed protein spots were identified using 2D gel electrophoresis (2DGE) on protein extracts from four pooled stages of meiosis and three genotypes (Chinese Spring wild-type, ph1b and ph2a wheat mutant lines). Tandem mass spectrometry (MS/MS) identification of peptides from these protein spots led to the isolation and characterisation of the full-length clones of a wheat Speckle-type POZ protein, an SF21-like protein and HSP70, and a partial coding sequence of a hexose transporter. Significantly, the putative functions of the Speckle-type POZ protein and HSP70 were confirmed using in vitro DNA binding assays. Through the use of a 2DGE proteomics approach, we show that proteomics is a viable alternative to genetic-based approaches when studying meiosis in wheat. More significantly, we report a potential role for a Speckle-type POZ protein and a HSP70 in chromosome pairing during the early stages of meiosis in bread wheat.
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Affiliation(s)
- Kelvin H P Khoo
- School of Agriculture, Food and Wine, Waite Research Institute, The University of Adelaide, Waite Campus, PMB1, Glen Osmond, SA 5064, Australia
| | - Amanda J Able
- School of Agriculture, Food and Wine, Waite Research Institute, The University of Adelaide, Waite Campus, PMB1, Glen Osmond, SA 5064, Australia
| | - Timothy K Chataway
- Proteomics Laboratory, School of Medicine, Flinders University, Bedford Park, SA 5042, Australia
| | - Jason A Able
- School of Agriculture, Food and Wine, Waite Research Institute, The University of Adelaide, Waite Campus, PMB1, Glen Osmond, SA 5064, Australia
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19
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Elias EV, Quiroga R, Gottig N, Nakanishi H, Nash TE, Neiman A, Lujan HD. Characterization of SNAREs determines the absence of a typical Golgi apparatus in the ancient eukaryote Giardia lamblia. J Biol Chem 2008; 283:35996-6010. [PMID: 18930915 DOI: 10.1074/jbc.m806545200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Giardia is a eukaryotic protozoal parasite with unusual characteristics, such as the absence of a morphologically evident Golgi apparatus. Although both constitutive and regulated pathways for protein secretion are evident in Giardia, little is known about the mechanisms involved in vesicular docking and fusion. In higher eukaryotes, soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) of the vesicle-associated membrane protein and syntaxin families play essential roles in these processes. In this work we identified and characterized genes for 17 SNAREs in Giardia to define the minimal set of subcellular organelles present during growth and encystation, in particular the presence or not of a Golgi apparatus. Expression and localization of all Giardia SNAREs demonstrate their presence in distinct subcellular compartments, which may represent the extent of the endomembrane system in eukaryotes. Remarkably, Giardia SNAREs, homologous to Golgi SNAREs from other organisms, do not allow the detection of a typical Golgi apparatus in either proliferating or differentiating trophozoites. However, some features of the Golgi, such as the packaging and sorting function, seem to be performed by the endoplasmic reticulum and/or the nuclear envelope. Moreover, depletion of individual genes demonstrated that several SNAREs are essential for viability, whereas others are dispensable. Thus, Giardia requires a smaller number of SNAREs compared with other eukaryotes to accomplish all of the vesicle trafficking events that are critical for the growth and differentiation of this important human pathogen.
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Affiliation(s)
- Eliana V Elias
- Laboratory of Biochemistry and Molecular Biology, School of Medicine, Catholic University of Cordoba/National Council for Science and Technology, Cordoba CP X5004ASK, Argentina
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20
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Tie JK, Zheng MY, Hsiao KLN, Perera L, Stafford DW, Straight DL. Transmembrane domain interactions and residue proline 378 are essential for proper structure, especially disulfide bond formation, in the human vitamin K-dependent gamma-glutamyl carboxylase. Biochemistry 2008; 47:6301-10. [PMID: 18498174 DOI: 10.1021/bi800235r] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We used recombinant techniques to create a two-chain form (residues 1-345 and residues 346-758) of the vitamin K-dependent gamma-glutamyl carboxylase, a glycoprotein located in the endoplasmic reticulum containing five transmembrane domains. The two-chain carboxylase had carboxylase and epoxidase activities similar to those of one-chain carboxylase. In addition, it had normal affinity for the propeptide of factor IX. We employed this molecule to investigate formation of the one disulfide bond in carboxylase, the transmembrane structure of carboxylase, and the potential interactions among the carboxylase's transmembrane domains. Our results indicate that the two peptides of the two-chain carboxylase are joined by a disulfide bond. Proline 378 is important for the structure necessary for disulfide formation. Results with the P378L carboxylase indicate that noncovalent bonds maintain the two-chain structure even when the disulfide bond is disrupted. As we had previously proposed, the fifth transmembrane domain of carboxylase is the last and only transmembrane domain in the C-terminal peptide of the two-chain carboxylase. We show that the noncovalent association between the two chains of carboxylase involves an interaction between the fifth transmembrane domain and the second transmembrane domain. Results of a homology model of transmembrane domains 2 and 5 suggest that not only do these two domains associate but that transmembrane domain 2 may interact with another transmembrane domain. This latter interaction may be mediated at least in part by a motif of glycine residues in the second transmembrane domain.
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Affiliation(s)
- Jian-Ke Tie
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
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21
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Garbelli R, Inverardi F, Medici V, Amadeo A, Verderio C, Matteoli M, Frassoni C. Heterogeneous expression of SNAP-25 in rat and human brain. J Comp Neurol 2008; 506:373-86. [PMID: 18041776 DOI: 10.1002/cne.21505] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Synaptosomal associated protein of 25 kDa (SNAP-25) is a SNARE component of the exocytotic apparatus involved in the release of neurotransmitter. We used multiple-labeling immunofluorescence, confocal microscopy, and ultrastructural immunocytochemistry to examine the expression of SNAP-25 in excitatory and inhibitory terminals from different rat and human brain areas. Glutamatergic and GABAergic terminals were identified by staining for the vesicular glutamate transporter (vGLUT1), glutamic acid decarboxylase (GAD67), or the vesicular GABA transporter (vGAT). In all examined areas GABAergic terminals did not display detectable levels of SNAP-25, whereas glutamatergic terminals expressed the protein to a variable extent. Codistribution analysis revealed a high colocalization between pixels detecting SNAP-25 labeling and pixels detecting vGLUT1 immunoreactivity. On the contrary, a low degree of pixel colocalization, comparable to that between two unrelated antigens, was detected between SNAP-25 and vGAT, thus suggesting a random overlap of immunofluorescence signals. Our immunofluorescence evidence was supported by ultrastructural data, which clearly confirmed that SNAP-25 was undetectable in GABAergic terminals identified by both their typical morphology and specific staining for GABA. Interestingly, our ultrastructural results confirmed that a subset of glutamatergic synapses do not contain detectable levels of SNAP-25. The present study extends our previous findings obtained in rodent hippocampus and provides evidence that SNAP-25 expression is highly variable between different axon terminals both in rat and human brain. The heterogeneous distribution of SNAP-25 may have important implications not only in relation to the function of the protein as a SNARE but also in the control of network excitability.
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Affiliation(s)
- Rita Garbelli
- Clinical Epileptology and Experimental Neurophysiology Unit, Fondazione IRCCS, Istituto Neurologico C Besta, via Celoria 11, Milano, Italy
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22
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Autoregulation in PC12 cells via P2Y receptors: Evidence for non-exocytotic nucleotide release from neuroendocrine cells. Purinergic Signal 2007; 3:367-75. [PMID: 18404450 PMCID: PMC2072914 DOI: 10.1007/s11302-007-9062-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Accepted: 07/11/2007] [Indexed: 11/01/2022] Open
Abstract
Nucleotides are released not only from neurons, but also from various other types of cells including fibroblasts, epithelial, endothelial and glial cells. While ATP release from non-neural cells is frequently Ca(2+) independent and mostly non-vesicular, neuronal ATP release is generally believed to occur via exocytosis. To evaluate whether nucleotide release from neuroendocrine cells might involve a non-vesicular component, the autocrine/paracrine activation of P2Y(12) receptors was used as a biosensor for nucleotide release from PC12 cells. Expression of a plasmid coding for the botulinum toxin C1 light chain led to a decrease in syntaxin 1 detected in immunoblots of PC12 membranes. In parallel, spontaneous as well as depolarization-evoked release of previously incorporated [(3)H]noradrenaline from transfected cells was significantly reduced in comparison with the release from untransfected cells, thus indicating that exocytosis was impaired. In PC12 cells expressing the botulinum toxin C1 light chain, ADP reduced cyclic AMP synthesis to the same extent as in non-transfected cells. Likewise, the enhancement of cyclic AMP synthesis either due to the blockade of P2Y(12) receptors or due to the degradation of extracellular neucleotides by apyrase was not different between non-transfected and botulinum toxin C1 light chain expressing cells. However, the inhibition of cyclic AMP synthesis caused by depolarization-evoked release of endogenous nucleotides was either abolished or greatly reduced in cells expressing the botulinum toxin C1 light chain. Together, these results show that spontaneous nucleotide release from neuroendocrine cells may occur independently of vesicle exocytosis, whereas depolarization-evoked nucleotide release relies predominantly on exocytotic mechanisms.
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Liu J, Guo T, Wu J, Bai X, Zhou Q, Sui SF. Overexpression of complexin in PC12 cells inhibits exocytosis by preventing SNARE complex recycling. BIOCHEMISTRY (MOSCOW) 2007; 72:439-44. [PMID: 17511609 DOI: 10.1134/s0006297907040116] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Complexin is an important protein that functions during Ca2+-dependent neurotransmitter release. Substantial evidence supports that complexin performs its role through rapid interaction with SNARE complex with high affinity. However, alpha-SNAP/NSF, which can disassemble the cis-SNARE complex in the presence of MgATP, competes with complexin to bind to SNARE complex. In addition, injection of alpha-SNAP into chromaffin cells enhances the size of the readily releasable pool, and mutation disrupting the ATPase activity of NSF results in the accumulation of SNARE complex. Thus, whether high concentrations of complexin could result in a reverse result is unclear. In this paper, we demonstrate that when stably overexpressed in PC12 cells, high levels of complexin result in the accumulation of SNARE complex. This in turn leads to a reduction in the size of the readily releasable pool of large dense core vesicles. These results suggest that high levels of complexin seem to prevent SNARE complex recycling, presumably by displacing NSF and alpha-SNAP from SNARE complex.
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Affiliation(s)
- Jingguo Liu
- Department of Biological Sciences and Biotechnology, State-Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua University, Beijing 100084, China
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24
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Kubista H, Boehm S. Molecular mechanisms underlying the modulation of exocytotic noradrenaline release via presynaptic receptors. Pharmacol Ther 2006; 112:213-42. [PMID: 16730801 DOI: 10.1016/j.pharmthera.2006.04.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2006] [Accepted: 04/10/2006] [Indexed: 10/24/2022]
Abstract
The release of noradrenaline from nerve terminals is modulated by a variety of presynaptic receptors. These receptors belong to one of the following three receptor superfamilies: transmitter-gated ion channels, G protein-coupled receptors (GPCR), and membrane receptors with intracellular enzymatic activities. For representatives of each of these three superfamilies, receptor activation has been reported to cause either an enhancement or a reduction of noradrenaline release. As these receptor classes display greatly diverging structures and functions, a multitude of different molecular mechanisms are involved in the regulation of noradrenaline release via presynaptic receptors. This review gives a short overview of the presynaptic receptors on noradrenergic nerve terminals and summarizes the events involved in vesicle exocytosis in order to finally delineate the most important signaling cascades that mediate the modulation via presynaptic receptors. In addition, the interactions between the various presynaptic receptors are described and the underlying molecular mechanisms are elucidated. Together, these presynaptic signaling mechanisms form a sophisticated network that precisely adapts the amount of noradrenaline being released to a given situation.
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Affiliation(s)
- Helmut Kubista
- Institute of Pharmacology, Centre of Biomolecular Medicine and Pharmacology, Medical University of Vienna, Waehringer Strasse 13a, A-1090 Vienna, Austria
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25
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Breidenbach MA, Brunger AT. New insights into clostridial neurotoxin-SNARE interactions. Trends Mol Med 2005; 11:377-81. [PMID: 16006188 DOI: 10.1016/j.molmed.2005.06.012] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2005] [Revised: 06/10/2005] [Accepted: 06/27/2005] [Indexed: 11/29/2022]
Abstract
Botulinum neurotoxin serotype A (BoNT/A) has achieved a dichotomous status in modern medicine; it is both a versatile treatment for several neurological disorders and a lethal poison responsible for causing the neuroparalytic syndrome botulism. The extent of paralysis largely depends on the dosage of toxin received. The toxins block neurotransmitter release by delivering their Zn(2+)-dependent protease components to the presynaptic side of chemical synapses. These highly specialized enzymes exclusively hydrolyze peptide bonds within SNARE (soluble N-ethylmaleiamide-sensitive factor attachment protein receptor) proteins. Recently, the structural basis for the highly specific interaction between BoNT/A and its target SNARE, SNAP-25 (synaptosomal-associated protein of 25kDa), was elucidated. New details regarding the nature of the toxin-SNARE interactions could be exploited for novel inhibitor design.
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Affiliation(s)
- Mark A Breidenbach
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA
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26
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Kikuta T, Ohara-Imaizumi M, Nakazaki M, Nishiwaki C, Nakamichi Y, Tei C, Aguilar-Bryan L, Bryan J, Nagamatsu S. Docking and fusion of insulin secretory granules in SUR1 knock out mouse beta-cells observed by total internal reflection fluorescence microscopy. FEBS Lett 2005; 579:1602-6. [PMID: 15757648 DOI: 10.1016/j.febslet.2005.01.074] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2004] [Revised: 01/30/2005] [Accepted: 01/31/2005] [Indexed: 11/27/2022]
Abstract
To explore how the sulfonylurea receptor (SUR1) is involved in docking and fusion of insulin granules, dynamic motion of single insulin secretory granules near the plasma membrane was examined in SUR1 knock-out (Sur1KO) beta-cells by total internal reflection fluorescence microscopy. Sur1KO beta-cells exhibited a marked reduction in the number of fusion events from previously docked granules. However, the number of docked granules declined during stimulation as a consequence of the release of docked granules into the cytoplasm vs. fusion with the plasma membrane. Thus, the impaired docking and fusion results in decreased insulin exocytosis from Sur1KO beta-cells.
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Affiliation(s)
- Toshiteru Kikuta
- Department of Biochemistry, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo 181-8611, Japan
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