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Gao J, Zhang S, Deng P, Wu Z, Lemaitre B, Zhai Z, Guo Z. Dietary L-Glu sensing by enteroendocrine cells adjusts food intake via modulating gut PYY/NPF secretion. Nat Commun 2024; 15:3514. [PMID: 38664401 PMCID: PMC11045819 DOI: 10.1038/s41467-024-47465-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 03/28/2024] [Indexed: 04/28/2024] Open
Abstract
Amino acid availability is monitored by animals to adapt to their nutritional environment. Beyond gustatory receptors and systemic amino acid sensors, enteroendocrine cells (EECs) are believed to directly percept dietary amino acids and secrete regulatory peptides. However, the cellular machinery underlying amino acid-sensing by EECs and how EEC-derived hormones modulate feeding behavior remain elusive. Here, by developing tools to specifically manipulate EECs, we find that Drosophila neuropeptide F (NPF) from mated female EECs inhibits feeding, similar to human PYY. Mechanistically, dietary L-Glutamate acts through the metabotropic glutamate receptor mGluR to decelerate calcium oscillations in EECs, thereby causing reduced NPF secretion via dense-core vesicles. Furthermore, two dopaminergic enteric neurons expressing NPFR perceive EEC-derived NPF and relay an anorexigenic signal to the brain. Thus, our findings provide mechanistic insights into how EECs assess food quality and identify a conserved mode of action that explains how gut NPF/PYY modulates food intake.
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Affiliation(s)
- Junjun Gao
- Department of Medical Genetics, School of Basic Medicine, Institute for Brain Research, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Song Zhang
- Department of Medical Genetics, School of Basic Medicine, Institute for Brain Research, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Pan Deng
- State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, PR China
- Department of Mechanical Engineering, University of British Columbia, Vancouver, British Columbia, Canada
| | - Zhigang Wu
- State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, PR China
| | - Bruno Lemaitre
- Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Zongzhao Zhai
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Sciences, Hunan Normal University, Changsha, Hunan, PR China.
| | - Zheng Guo
- Department of Medical Genetics, School of Basic Medicine, Institute for Brain Research, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
- Cell Architecture Research Center, Huazhong University of Science and Technology, Wuhan, Hubei, China.
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2
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Li J, Dang P, Li Z, Zhao T, Cheng D, Pan D, Yuan Y, Song W. Peroxisomal ERK mediates Akh/glucagon action and glycemic control. Cell Rep 2023; 42:113200. [PMID: 37796662 DOI: 10.1016/j.celrep.2023.113200] [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: 04/05/2023] [Revised: 06/18/2023] [Accepted: 09/15/2023] [Indexed: 10/07/2023] Open
Abstract
The enhanced response of glucagon and its Drosophila homolog, adipokinetic hormone (Akh), leads to high-caloric-diet-induced hyperglycemia across species. While previous studies have characterized regulatory components transducing linear Akh signaling promoting carbohydrate production, the spatial elucidation of Akh action at the organelle level still remains largely unclear. In this study, we find that Akh phosphorylates extracellular signal-regulated kinase (ERK) and translocates it to peroxisome via calcium/calmodulin-dependent protein kinase II (CaMKII) cascade to increase carbohydrate production in the fat body, leading to hyperglycemia. The mechanisms include that ERK mediates fat body peroxisomal conversion of amino acids into carbohydrates for gluconeogenesis in response to Akh. Importantly, Akh receptor (AkhR) or ERK deficiency, importin-associated ERK retention from peroxisome, or peroxisome inactivation in the fat body sufficiently alleviates high-sugar-diet-induced hyperglycemia. We also observe mammalian glucagon-induced hepatic ERK peroxisomal translocation in diabetic subjects. Therefore, our results conclude that the Akh/glucagon-peroxisomal-ERK axis is a key spatial regulator of glycemic control.
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Affiliation(s)
- Jiaying Li
- Department of Hepatobiliary and Pancreatic Surgery, Frontier Science Center for Immunology and Metabolism, Medical Research Institute, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, Hubei 430071, China; TaiKang Center for Life and Medical Sciences, Wuhan University, Wuhan, Hubei 430071, China
| | - Peixuan Dang
- Department of Hepatobiliary and Pancreatic Surgery, Frontier Science Center for Immunology and Metabolism, Medical Research Institute, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, Hubei 430071, China; TaiKang Center for Life and Medical Sciences, Wuhan University, Wuhan, Hubei 430071, China
| | - Zhen Li
- Department of Hepatobiliary and Pancreatic Surgery, Frontier Science Center for Immunology and Metabolism, Medical Research Institute, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, Hubei 430071, China
| | - Tujing Zhao
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
| | - Daojun Cheng
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
| | - Dingyu Pan
- Department of Hepatobiliary and Pancreatic Surgery, Frontier Science Center for Immunology and Metabolism, Medical Research Institute, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, Hubei 430071, China.
| | - Yufeng Yuan
- Department of Hepatobiliary and Pancreatic Surgery, Frontier Science Center for Immunology and Metabolism, Medical Research Institute, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, Hubei 430071, China; TaiKang Center for Life and Medical Sciences, Wuhan University, Wuhan, Hubei 430071, China.
| | - Wei Song
- Department of Hepatobiliary and Pancreatic Surgery, Frontier Science Center for Immunology and Metabolism, Medical Research Institute, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, Hubei 430071, China; TaiKang Center for Life and Medical Sciences, Wuhan University, Wuhan, Hubei 430071, China.
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3
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Velagala V, Soundarrajan DK, Unger MF, Gazzo D, Kumar N, Li J, Zartman J. The multimodal action of G alpha q in coordinating growth and homeostasis in the Drosophila wing imaginal disc. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.08.523049. [PMID: 36711848 PMCID: PMC9881979 DOI: 10.1101/2023.01.08.523049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Background G proteins mediate cell responses to various ligands and play key roles in organ development. Dysregulation of G-proteins or Ca 2+ signaling impacts many human diseases and results in birth defects. However, the downstream effectors of specific G proteins in developmental regulatory networks are still poorly understood. Methods We employed the Gal4/UAS binary system to inhibit or overexpress Gαq in the wing disc, followed by phenotypic analysis. Immunohistochemistry and next-gen RNA sequencing identified the downstream effectors and the signaling cascades affected by the disruption of Gαq homeostasis. Results Here, we characterized how the G protein subunit Gαq tunes the size and shape of the wing in the larval and adult stages of development. Downregulation of Gαq in the wing disc reduced wing growth and delayed larval development. Gαq overexpression is sufficient to promote global Ca 2+ waves in the wing disc with a concomitant reduction in the Drosophila final wing size and a delay in pupariation. The reduced wing size phenotype is further enhanced when downregulating downstream components of the core Ca 2+ signaling toolkit, suggesting that downstream Ca 2+ signaling partially ameliorates the reduction in wing size. In contrast, Gαq -mediated pupariation delay is rescued by inhibition of IP 3 R, a key regulator of Ca 2+ signaling. This suggests that Gαq regulates developmental phenotypes through both Ca 2+ -dependent and Ca 2+ -independent mechanisms. RNA seq analysis shows that disruption of Gαq homeostasis affects nuclear hormone receptors, JAK/STAT pathway, and immune response genes. Notably, disruption of Gαq homeostasis increases expression levels of Dilp8, a key regulator of growth and pupariation timing. Conclusion Gαq activity contributes to cell size regulation and wing metamorphosis. Disruption to Gαq homeostasis in the peripheral wing disc organ delays larval development through ecdysone signaling inhibition. Overall, Gαq signaling mediates key modules of organ size regulation and epithelial homeostasis through the dual action of Ca 2+ -dependent and independent mechanisms.
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4
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Gu Q, Wu J, Tian Y, Cheng S, Zhang ZC, Han J. Gαq splice variants mediate phototransduction, rhodopsin synthesis, and retinal integrity in Drosophila. J Biol Chem 2020; 295:5554-5563. [PMID: 32198182 PMCID: PMC7186184 DOI: 10.1074/jbc.ra120.012764] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 03/19/2020] [Indexed: 11/06/2022] Open
Abstract
Heterotrimeric G proteins mediate a variety of signaling processes by coupling G protein-coupled receptors to intracellular effector molecules. In Drosophila, the Gαq gene encodes several Gαq splice variants, with the Gαq1 isoform protein playing a major role in fly phototransduction. However, Gαq1 null mutant flies still exhibit a residual light response, indicating that other Gαq splice variants or additional Gq α subunits are involved in phototransduction. Here, we isolated a mutant fly with no detectable light responses, decreased rhodopsin (Rh) levels, and rapid retinal degeneration. Using electrophysiological and genetic studies, biochemical assays, immunoblotting, real-time RT-PCR, and EM analysis, we found that mutations in the Gαq gene disrupt light responses and demonstrate that the Gαq3 isoform protein is responsible for the residual light response in Gαq1 null mutants. Moreover, we report that Gαq3 mediates rhodopsin synthesis. Depletion of all Gαq splice variants led to rapid light-dependent retinal degeneration, due to the formation stable Rh1-arrestin 2 (Arr2) complexes. Our findings clarify essential roles of several different Gαq splice variants in phototransduction and retinal integrity in Drosophila and reveal that Gαq3 functions in rhodopsin synthesis.
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Affiliation(s)
- Qiuxiang Gu
- School of Life Science and Technology, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu 210096, China
| | - Jinglin Wu
- School of Life Science and Technology, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu 210096, China
| | - Yao Tian
- School of Life Science and Technology, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu 210096, China
| | - Shanshan Cheng
- School of Life Science and Technology, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu 210096, China
| | - Zi Chao Zhang
- School of Life Science and Technology, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu 210096, China; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu 226001, China.
| | - Junhai Han
- School of Life Science and Technology, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu 210096, China; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu 226001, China.
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5
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Vajente N, Norante R, Redolfi N, Daga A, Pizzo P, Pendin D. Microtubules Stabilization by Mutant Spastin Affects ER Morphology and Ca 2+ Handling. Front Physiol 2019; 10:1544. [PMID: 31920731 PMCID: PMC6933510 DOI: 10.3389/fphys.2019.01544] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 12/05/2019] [Indexed: 01/21/2023] Open
Abstract
The endoplasmic reticulum (ER) extends as a network of interconnected tubules and sheet-like structures in eukaryotic cells. ER tubules dynamically change their morphology and position within the cells in response to physiological stimuli and these network rearrangements depend on the microtubule (MT) cytoskeleton. Store-operated calcium entry (SOCE) relies on the repositioning of ER tubules to form specific ER-plasma membrane junctions. Indeed, the tips of polymerizing MTs are supposed to provide the anchor for ER tubules to move toward the plasma membrane, however the precise role of the cytoskeleton during SOCE has not been conclusively clarified. Here we exploit an in vivo approach involving the manipulation of MT dynamics in Drosophila melanogaster by neuronal expression of a dominant-negative variant of the MT-severing protein spastin to induce MT hyper-stabilization. We show that MT stabilization alters ER morphology, favoring an enrichment in ER sheets at the expense of tubules. Stabilizing MTs has a negative impact on the process of SOCE and results in a reduced ER Ca2+ content, affecting the flight ability of the flies. Restoring proper MT organization by administering the MT-destabilizing drug vinblastine, chronically or acutely, rescues ER morphology, SOCE and flight ability, indicating that MT dynamics impairment is responsible for all the phenotypes observed.
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Affiliation(s)
- Nicola Vajente
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Rosa Norante
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Nelly Redolfi
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Andrea Daga
- Laboratory of Molecular Biology, Scientific Institute IRCCS E. Medea, Lecco, Italy
| | - Paola Pizzo
- Department of Biomedical Sciences, University of Padua, Padua, Italy.,Neuroscience Institute-Italian National Research Council (CNR), Padua, Italy
| | - Diana Pendin
- Department of Biomedical Sciences, University of Padua, Padua, Italy.,Neuroscience Institute-Italian National Research Council (CNR), Padua, Italy
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6
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Balasubramanian V, Srinivasan B. Genetic analyses uncover pleiotropic compensatory roles for Drosophila Nucleobindin-1 in inositol trisphosphate-mediated intracellular calcium homeostasis. Genome 2019; 63:61-90. [PMID: 31557446 DOI: 10.1139/gen-2019-0113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nucleobindin-1 is an EF-hand calcium-binding protein with a distinctive profile, predominantly localized to the Golgi in insect and wide-ranging vertebrate cell types, alike. Its putative involvements in intracellular calcium (Ca2+) homeostasis have never been phenotypically characterized in any model organism. We have analyzed an adult-viable mutant that completely disrupts the G protein α-subunit binding and activating (GBA) motif of Drosophila Nucleobindin-1 (dmNUCB1). Such disruption does not manifest any obvious fitness-related, morphological/developmental, or behavioral abnormalities. A single copy of this mutation or the knockdown of dmnucb1 in restricted sets of cells variously rescues pleiotropic mutant phenotypes arising from impaired inositol 1,4,5-trisphosphate receptor (IP3R) activity (in turn depleting cytoplasmic Ca2+ levels across diverse tissue types). Additionally, altered dmNUCB1 expression or function considerably reverses lifespan and mobility improvements effected by IP3R mutants, in a Drosophila model of amyotrophic lateral sclerosis. Homology modeling-based analyses further predict a high degree of conformational conservation in Drosophila, of biochemically validated structural determinants in the GBA motif that specify in vertebrates, the unconventional Ca2+-regulated interaction of NUCB1 with Gαi subunits. The broad implications of our findings are hypothetically discussed, regarding potential roles for NUCB1 in GBA-mediated, Golgi-associated Ca2+ signaling, in health and disease.
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Affiliation(s)
- Vidhya Balasubramanian
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai 600036, India.,Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai 600036, India
| | - Bharath Srinivasan
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai 600036, India.,Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai 600036, India
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7
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Brusich DJ, Spring AM, James TD, Yeates CJ, Helms TH, Frank CA. Drosophila CaV2 channels harboring human migraine mutations cause synapse hyperexcitability that can be suppressed by inhibition of a Ca2+ store release pathway. PLoS Genet 2018; 14:e1007577. [PMID: 30080864 PMCID: PMC6095605 DOI: 10.1371/journal.pgen.1007577] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 08/16/2018] [Accepted: 07/20/2018] [Indexed: 11/28/2022] Open
Abstract
Gain-of-function mutations in the human CaV2.1 gene CACNA1A cause familial hemiplegic migraine type 1 (FHM1). To characterize cellular problems potentially triggered by CaV2.1 gains of function, we engineered mutations encoding FHM1 amino-acid substitutions S218L (SL) and R192Q (RQ) into transgenes of Drosophila melanogaster CaV2/cacophony. We expressed the transgenes pan-neuronally. Phenotypes were mild for RQ-expressing animals. By contrast, single mutant SL- and complex allele RQ,SL-expressing animals showed overt phenotypes, including sharply decreased viability. By electrophysiology, SL- and RQ,SL-expressing neuromuscular junctions (NMJs) exhibited enhanced evoked discharges, supernumerary discharges, and an increase in the amplitudes and frequencies of spontaneous events. Some spontaneous events were gigantic (10-40 mV), multi-quantal events. Gigantic spontaneous events were eliminated by application of TTX-or by lowered or chelated Ca2+-suggesting that gigantic events were elicited by spontaneous nerve firing. A follow-up genetic approach revealed that some neuronal hyperexcitability phenotypes were reversed after knockdown or mutation of Drosophila homologs of phospholipase Cβ (PLCβ), IP3 receptor, or ryanodine receptor (RyR)-all factors known to mediate Ca2+ release from intracellular stores. Pharmacological inhibitors of intracellular Ca2+ store release produced similar effects. Interestingly, however, the decreased viability phenotype was not reversed by genetic impairment of intracellular Ca2+ release factors. On a cellular level, our data suggest inhibition of signaling that triggers intracellular Ca2+ release could counteract hyperexcitability induced by gains of CaV2.1 function.
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Affiliation(s)
- Douglas J. Brusich
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, IA, United States of America
| | - Ashlyn M. Spring
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, IA, United States of America
- Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, IA, United States of America
| | - Thomas D. James
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, IA, United States of America
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA, United States of America
| | - Catherine J. Yeates
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, IA, United States of America
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA, United States of America
| | - Timothy H. Helms
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, IA, United States of America
| | - C. Andrew Frank
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, IA, United States of America
- Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, IA, United States of America
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA, United States of America
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8
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Jayakumar S, Hasan G. Neuronal Calcium Signaling in Metabolic Regulation and Adaptation to Nutrient Stress. Front Neural Circuits 2018; 12:25. [PMID: 29674958 PMCID: PMC5895653 DOI: 10.3389/fncir.2018.00025] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 03/02/2018] [Indexed: 01/13/2023] Open
Abstract
All organisms can respond physiologically and behaviorally to environmental fluxes in nutrient levels. Different nutrient sensing pathways exist for specific metabolites, and their inputs ultimately define appropriate nutrient uptake and metabolic homeostasis. Nutrient sensing mechanisms at the cellular level require pathways such as insulin and target of rapamycin (TOR) signaling that integrates information from different organ systems like the fat body and the gut. Such integration is essential for coordinating growth with development. Here we review the role of a newly identified set of integrative interneurons and the role of intracellular calcium signaling within these neurons, in regulating nutrient sensing under conditions of nutrient stress. A comparison of the identified Drosophila circuit and cellular mechanisms employed in this circuit, with vertebrate systems, suggests that the identified cell signaling mechanisms may be conserved for neural circuit function related to nutrient sensing by central neurons. The ideas proposed are potentially relevant for understanding the molecular basis of metabolic disorders, because these are frequently linked to nutritional stress.
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Affiliation(s)
- Siddharth Jayakumar
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| | - Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
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9
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Abstract
Intracellular calcium signals in neurons frequently derive from the stimulation of G protein-coupled receptors (GPCR) by neurotransmitters, neuropeptides, and neurohormones. GPCR stimulation in neurons leads to generation of inositol 1,4,5-trisphosphate (IP3), which in turn activates endoplasmic reticulum (ER)-localized IP3 receptors. The IP3 receptor (IP3R) is a ligand-gated Ca2+ channel, which releases Ca2+ from ER stores. In Drosophila neurons it has been shown that depletion of ER Ca2+ store is followed by store-operated Ca2+ entry (SOCE) through STIM and Orai, the ER Ca2+ sensor and the plasma membrane Ca2+ channel respectively. The elucidation of this Ca2+ signaling pathway in neurons has in part been possible due to the ease of genetic manipulation in Drosophila, which has allowed neuron-specific knockdown of various proteins of interest. This has been followed by standardization of conditions for culturing neurons from dissected brains of the relevant genotypes, such that they could be used for robust Ca2+ measurements by imaging with standard Ca2+ indicator dyes. Protocols for measurement of IP3-mediated Ca2+ release, passive depletion of ER Ca2+ store, and SOCE in primary cultures of Drosophila neurons are described here.
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10
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Megha , Hasan G. Control of protein translation by IP 3R-mediated Ca 2+ release in Drosophila neuroendocrine cells. Fly (Austin) 2017; 11:0. [PMID: 28949794 PMCID: PMC5721944 DOI: 10.1080/19336934.2017.1384103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 09/18/2017] [Accepted: 09/20/2017] [Indexed: 12/25/2022] Open
Abstract
The inositol 1,4,5-trisphosphate receptor (IP3R) is one of two Ca2+ channels that gates Ca2+ release from ER-stores. The ligand IP3, generated upon specific G-protein coupled receptor activation, binds to IP3R to release Ca2+ into the cytosol. IP3R also mediates ER-store Ca2+ release into the mitochondria, under basal as well as stimulatory conditions; an activity that influences cellular bioenergetics and thus, cellular growth and proliferation. In Drosophila neuroendocrine cells expressing a hypomorphic mutant of IP3R, we observed reduced protein translation levels. Here, we discuss the possible molecular mechanism for this observation. We hypothesise that the cellular energy sensor, AMPK connects IP3R mediated Ca2+ release into the mitochondria, to protein translation, via the TOR pathway.
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Affiliation(s)
- Megha
- National Centre for Biological Sciences-TIFR, GKVK Campus, Bangalore, India
| | - Gaiti Hasan
- National Centre for Biological Sciences-TIFR, GKVK Campus, Bangalore, India
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11
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Deb BK, Pathak T, Hasan G. Store-independent modulation of Ca(2+) entry through Orai by Septin 7. Nat Commun 2016; 7:11751. [PMID: 27225060 PMCID: PMC4894974 DOI: 10.1038/ncomms11751] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 04/26/2016] [Indexed: 01/07/2023] Open
Abstract
Orai channels are required for store-operated Ca2+ entry (SOCE) in multiple cell types. Septins are a class of GTP-binding proteins that function as diffusion barriers in cells. Here we show that Septin 7 acts as a ‘molecular brake’ on activation of Orai channels in Drosophila neurons. Lowering Septin 7 levels results in dOrai-mediated Ca2+ entry and higher cytosolic Ca2+ in resting neurons. This Ca2+ entry is independent of depletion of endoplasmic reticulum Ca2+ stores and Ca2+ release through the inositol-1,4,5-trisphosphate receptor. Importantly, store-independent Ca2+ entry through Orai compensates for reduced SOCE in the Drosophila flight circuit. Moreover, overexpression of Septin 7 reduces both SOCE and flight duration, supporting its role as a negative regulator of Orai channel function in vivo. Septin 7 levels in neurons can, therefore, alter neural circuit function by modulating Orai function and Ca2+ homeostasis. Orai channels are well known to mediate store-operated calcium entry. Here authors show that in neurons of the Drosophila flight circuit, Septin 7 acts as a negative regulator of Orai channels, surprisingly, by modulating store-independent calcium entry through Orai.
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Affiliation(s)
- Bipan Kumar Deb
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore 560065, India
| | - Trayambak Pathak
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore 560065, India.,Manipal University, Manipal, Karnataka 576104, India
| | - Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore 560065, India
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12
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Dean DM, Maroja LS, Cottrill S, Bomkamp BE, Westervelt KA, Deitcher DL. The wavy Mutation Maps to the Inositol 1,4,5-Trisphosphate 3-Kinase 2 (IP3K2) Gene of Drosophila and Interacts with IP3R to Affect Wing Development. G3 (BETHESDA, MD.) 2015; 6:299-310. [PMID: 26613949 PMCID: PMC4751550 DOI: 10.1534/g3.115.024307] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 11/24/2015] [Indexed: 12/31/2022]
Abstract
Inositol 1,4,5-trisphosphate (IP3) regulates a host of biological processes from egg activation to cell death. When IP3-specific receptors (IP3Rs) bind to IP3, they release calcium from the ER into the cytoplasm, triggering a variety of cell type- and developmental stage-specific responses. Alternatively, inositol polyphosphate kinases can phosphorylate IP3; this limits IP3R activation by reducing IP3 levels, and also generates new signaling molecules altogether. These divergent pathways draw from the same IP3 pool yet cause very different cellular responses. Therefore, controlling the relative rates of IP3R activation vs. phosphorylation of IP3 is essential for proper cell functioning. Establishing a model system that sensitively reports the net output of IP3 signaling is crucial for identifying the controlling genes. Here we report that mutant alleles of wavy (wy), a classic locus of the fruit fly Drosophila melanogaster, map to IP3 3-kinase 2 (IP3K2), a member of the inositol polyphosphate kinase gene family. Mutations in wy disrupt wing structure in a highly specific pattern. RNAi experiments using GAL4 and GAL80(ts) indicated that IP3K2 function is required in the wing discs of early pupae for normal wing development. Gradations in the severity of the wy phenotype provide high-resolution readouts of IP3K2 function and of overall IP3 signaling, giving this system strong potential as a model for further study of the IP3 signaling network. In proof of concept, a dominant modifier screen revealed that mutations in IP3R strongly suppress the wy phenotype, suggesting that the wy phenotype results from reduced IP4 levels, and/or excessive IP3R signaling.
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Affiliation(s)
- Derek M Dean
- Department of Biology, Williams College, Williamstown, Massachusetts 01267
| | - Luana S Maroja
- Department of Biology, Williams College, Williamstown, Massachusetts 01267
| | - Sarah Cottrill
- Department of Biology, Williams College, Williamstown, Massachusetts 01267
| | - Brent E Bomkamp
- Department of Biology, Williams College, Williamstown, Massachusetts 01267
| | | | - David L Deitcher
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853
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Narciso C, Wu Q, Brodskiy P, Garston G, Baker R, Fletcher A, Zartman J. Patterning of wound-induced intercellular Ca(2+) flashes in a developing epithelium. Phys Biol 2015; 12:056005. [PMID: 26331891 DOI: 10.1088/1478-3975/12/5/056005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Differential mechanical force distributions are increasingly recognized to provide important feedback into the control of an organ's final size and shape. As a second messenger that integrates and relays mechanical information to the cell, calcium ions (Ca(2+)) are a prime candidate for providing important information on both the overall mechanical state of the tissue and resulting behavior at the individual-cell level during development. Still, how the spatiotemporal properties of Ca(2+) transients reflect the underlying mechanical characteristics of tissues is still poorly understood. Here we use an established model system of an epithelial tissue, the Drosophila wing imaginal disc, to investigate how tissue properties impact the propagation of Ca(2+) transients induced by laser ablation. The resulting intercellular Ca(2+) flash is found to be mediated by inositol 1,4,5-trisphosphate and depends on gap junction communication. Further, we find that intercellular Ca(2+) transients show spatially non-uniform characteristics across the proximal-distal axis of the larval wing imaginal disc, which exhibit a gradient in cell size and anisotropy. A computational model of Ca(2+) transients is employed to identify the principle factors explaining the spatiotemporal patterning dynamics of intercellular Ca(2+) flashes. The relative Ca(2+) flash anisotropy is principally explained by local cell shape anisotropy. Further, Ca(2+) velocities are relatively uniform throughout the wing disc, irrespective of cell size or anisotropy. This can be explained by the opposing effects of cell diameter and cell elongation on intercellular Ca(2+) propagation. Thus, intercellular Ca(2+) transients follow lines of mechanical tension at velocities that are largely independent of tissue heterogeneity and reflect the mechanical state of the underlying tissue.
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Affiliation(s)
- Cody Narciso
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, 182 Fitzpatrick Hall, Notre Dame, IN 46556, USA
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14
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Brusich DJ, Spring AM, Frank CA. A single-cross, RNA interference-based genetic tool for examining the long-term maintenance of homeostatic plasticity. Front Cell Neurosci 2015; 9:107. [PMID: 25859184 PMCID: PMC4374470 DOI: 10.3389/fncel.2015.00107] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 03/09/2015] [Indexed: 11/15/2022] Open
Abstract
Homeostatic synaptic plasticity (HSP) helps neurons and synapses maintain physiologically appropriate levels of output. The fruit fly Drosophila melanogaster larval neuromuscular junction (NMJ) is a valuable model for studying HSP. Here we introduce a genetic tool that allows fruit fly researchers to examine the lifelong maintenance of HSP with a single cross. The tool is a fruit fly stock that combines the GAL4/UAS expression system with RNA interference (RNAi)-based knock down of a glutamate receptor subunit gene. With this stock, we uncover important new information about the maintenance of HSP. We address an open question about the role that presynaptic CaV2-type Ca2+ channels play in NMJ homeostasis. Published experiments have demonstrated that hypomorphic missense mutations in the CaV2 α1a subunit gene cacophony (cac) can impair homeostatic plasticity at the NMJ. Here we report that reducing cac expression levels by RNAi is not sufficient to impair homeostatic plasticity. The presence of wild-type channels appears to support HSP—even when total CaV2 function is severely reduced. We also conduct an RNAi- and electrophysiology-based screen to identify new factors required for sustained homeostatic signaling throughout development. We uncover novel roles in HSP for Drosophila homologs of Cysteine string protein (CSP) and Phospholipase Cβ (Plc21C). We characterize those roles through follow-up genetic tests. We discuss how CSP, Plc21C, and associated factors could modulate presynaptic CaV2 function, presynaptic Ca2+ handling, or other signaling processes crucial for sustained homeostatic regulation of NMJ function throughout development. Our findings expand the scope of signaling pathways and processes that contribute to the durable strength of the NMJ.
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Affiliation(s)
- Douglas J Brusich
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa Iowa City, IA, USA
| | - Ashlyn M Spring
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa Iowa City, IA, USA ; Interdisciplinary Graduate Program in Genetics, University of Iowa Iowa City, IA, USA
| | - C Andrew Frank
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa Iowa City, IA, USA ; Interdisciplinary Programs in Genetics, Neuroscience, and MCB, University of Iowa Iowa City, IA, USA
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15
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Agrawal T, Sadaf S, Hasan G. A genetic RNAi screen for IP₃/Ca²⁺ coupled GPCRs in Drosophila identifies the PdfR as a regulator of insect flight. PLoS Genet 2013; 9:e1003849. [PMID: 24098151 PMCID: PMC3789835 DOI: 10.1371/journal.pgen.1003849] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 08/18/2013] [Indexed: 01/12/2023] Open
Abstract
Insect flight is regulated by various sensory inputs and neuromodulatory circuits which function in synchrony to control and fine-tune the final behavioral outcome. The cellular and molecular bases of flight neuromodulatory circuits are not well defined. In Drosophila melanogaster, it is known that neuronal IP3 receptor mediated Ca2+ signaling and store-operated Ca2+ entry (SOCE) are required for air-puff stimulated adult flight. However, G-protein coupled receptors (GPCRs) that activate intracellular Ca2+ signaling in the context of flight are unknown in Drosophila. We performed a genetic RNAi screen to identify GPCRs that regulate flight by activating the IP3 receptor. Among the 108 GPCRs screened, we discovered 5 IP3/Ca2+ linked GPCRs that are necessary for maintenance of air-puff stimulated flight. Analysis of their temporal requirement established that while some GPCRs are required only during flight circuit development, others are required both in pupal development as well as during adult flight. Interestingly, our study identified the Pigment Dispersing Factor Receptor (PdfR) as a regulator of flight circuit development and as a modulator of acute flight. From the analysis of PdfR expressing neurons relevant for flight and its well-defined roles in other behavioral paradigms, we propose that PdfR signaling functions systemically to integrate multiple sensory inputs and modulate downstream motor behavior. A majority of behavioral patterns in flying insects depend upon their ability to modulate flight. In Drosophila melanogaster, mutations in the IP3 receptor gene lead to loss of voluntary flight in response to a natural stimulus like a gentle air-puff. From previous genetic and cellular studies it is known that the IP3R in Drosophila is activated by G-protein coupled receptors (GPCRs). However, GPCRs that act upstream of the IP3R in the context of flight are not known. Therefore, we performed a genetic RNAi screen to identify GPCRs which regulate flight. This screen was followed by a secondary suppressor screen that assessed the role of each identified GPCR in activating IP3/Ca2+ signaling. We found 5 such GPCRs. Our results demonstrate that these GPCRs are required during flight circuit development and during adult flight. One flight-regulating receptor identified was the Pigment Dispersing Factor Receptor (PdfR). This receptor is known to regulate behaviors such as circadian rhythms, geotaxis and reproduction. A spatio-temporal analysis of PdfR flight function indicates that it regulates both flight circuit development and acute flight through multiple neurons. We postulate that PdfR signaling could modulate and integrate multiple behavioral inputs in Drosophila and other flying insects.
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Affiliation(s)
- Tarjani Agrawal
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| | - Sufia Sadaf
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| | - Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
- * E-mail:
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16
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Badsha F, Kain P, Prabhakar S, Sundaram S, Padinjat R, Rodrigues V, Hasan G. Mutants in Drosophila TRPC channels reduce olfactory sensitivity to carbon dioxide. PLoS One 2012; 7:e49848. [PMID: 23185459 PMCID: PMC3501451 DOI: 10.1371/journal.pone.0049848] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Accepted: 10/14/2012] [Indexed: 12/05/2022] Open
Abstract
BACKGROUND Members of the canonical Transient Receptor Potential (TRPC) class of cationic channels function downstream of Gαq and PLCβ in Drosophila photoreceptors for transducing visual stimuli. Gαq has recently been implicated in olfactory sensing of carbon dioxide (CO(2)) and other odorants. Here we investigated the role of PLCβ and TRPC channels for sensing CO(2) in Drosophila. METHODOLOGY/PRINCIPAL FINDINGS Through behavioral assays it was demonstrated that Drosophila mutants for plc21c, trp and trpl have a reduced sensitivity for CO(2). Immuno-histochemical staining for TRP, TRPL and TRPγ indicates that all three channels are expressed in Drosophila antennae including the sensory neurons that express CO(2) receptors. Electrophysiological recordings obtained from the antennae of protein null alleles of TRP (trp(343)) and TRPL (trpl(302)), showed that the sensory response to multiple concentrations of CO(2) was reduced. However, trpl(302); trp(343) double mutants still have a residual response to CO(2). Down-regulation of TRPC channels specifically in CO(2) sensing olfactory neurons reduced the response to CO(2) and this reduction was obtained even upon down-regulation of the TRPCs in adult olfactory sensory neurons. Thus the reduced response to CO(2) obtained from the antennae of TRPC RNAi strains is not due to a developmental defect. CONCLUSION These observations show that reduction in TRPC channel function significantly reduces the sensitivity of the olfactory response to CO(2) concentrations of 5% or less in adult Drosophila. It is possible that the CO(2) receptors Gr63a and Gr21a activate the TRPC channels through Gαq and PLC21C.
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Affiliation(s)
- Farhath Badsha
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka, India
| | - Pinky Kain
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka, India
| | - Sunil Prabhakar
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka, India
| | | | - Raghu Padinjat
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka, India
| | - Veronica Rodrigues
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka, India
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, Maharashtra, India
| | - Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka, India
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17
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IP3R, store-operated Ca2+ entry and neuronal Ca2+ homoeostasis in Drosophila. Biochem Soc Trans 2012; 40:279-81. [DOI: 10.1042/bst20110618] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The IP3R (inositol 1,4,5-trisphosphate receptor) releases Ca2+ from the ER (endoplasmic reticulum) store upon binding to its ligand InsP3, which is thought to be generated by activation of certain membrane-bound G-protein-coupled receptors in Drosophila. Depletion of Ca2+ in the ER store also activates SOCE (store-operated Ca2+ entry) from the extracellular milieu across the plasma membrane, leading to a second rise in cytosolic Ca2+, which is then pumped back into the ER. The role of the IP3R and SOCE in mediating Ca2+ homoeostasis in neurons, their requirement in neuronal function and effect on neuronal physiology and as a consequence behaviour, are reviewed in the present article.
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18
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Chorna T, Hasan G. The genetics of calcium signaling in Drosophila melanogaster. Biochim Biophys Acta Gen Subj 2011; 1820:1269-82. [PMID: 22100727 DOI: 10.1016/j.bbagen.2011.11.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 10/31/2011] [Accepted: 11/02/2011] [Indexed: 01/13/2023]
Abstract
BACKGROUND Genetic screens for behavioral and physiological defects in Drosophila melanogaster, helped identify several components of calcium signaling of which some, like the Trps, were novel. For genes initially identified in vertebrates, reverse genetic methods have allowed functional studies at the cellular and systemic levels. SCOPE OF REVIEW The aim of this review is to explain how various genetic methods available in Drosophila have been used to place different arms of Ca2+ signaling in the context of organismal development, physiology and behavior. MAJOR CONCLUSION Mutants generated in genes encoding a range of Ca2+ transport systems, binding proteins and enzymes affect multiple aspects of neuronal and muscle physiology. Some also affect the maintenance of ionic balance and excretion from malpighian tubules and innate immune responses in macrophages. Aspects of neuronal physiology affected include synaptic growth and plasticity, sensory transduction, flight circuit development and function. Genetic interaction screens have shown that mechanisms of maintaining Ca2+ homeostasis in Drosophila are cell specific and require a synergistic interplay between different intracellular and plasma membrane Ca2+ signaling molecules. GENERAL SIGNIFICANCE Insights gained through genetic studies of conserved Ca2+ signaling pathways have helped understand multiple aspects of fly physiology. The similarities between mutant phenotypes of Ca2+ signaling genes in Drosophila with certain human disease conditions, especially where homologous genes are causative factors, are likely to aid in the discovery of underlying disease mechanisms and help develop novel therapeutic strategies. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signalling.
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Affiliation(s)
- Tetyana Chorna
- National Center for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
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19
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Kumar S, Dey D, Hasan G. Patterns of gene expression in Drosophila InsP3 receptor mutant larvae reveal a role for InsP3 signaling in carbohydrate and energy metabolism. PLoS One 2011; 6:e24105. [PMID: 21901161 PMCID: PMC3162032 DOI: 10.1371/journal.pone.0024105] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 08/04/2011] [Indexed: 11/18/2022] Open
Abstract
Background The Inositol 1,4,5-trisphosphate receptor (InsP3R) is an InsP3 gated intracellular Ca2+-release channel. Characterization of Drosophila mutants for the InsP3R has demonstrated that InsP3-mediated Ca2+ release is required in Drosophila larvae for growth and viability. Methodology/Principal Findings To understand the molecular basis of these growth defects a genome wide microarray analysis has been carried out with larval RNA obtained from a strong InsP3R mutant combination in which 1504 independent genes were differentially regulated with a log2 of fold change of 1 or more and P<0.05. This was followed by similar transcript analyses from InsP3R mutants where growth defects were either suppressed by introduction of a dominant suppressor or rescued by ectopic expression of an InsP3R transgene in the Drosophila insulin like peptide-2 (Dilp2) producing cells. Conclusions/Significance These studies show that expression of transcripts related to carbohydrate and amine metabolism is altered in InsP3 receptor mutant larvae. Moreover, from a comparative analysis of genes that are regulated in the suppressed and rescued conditions with the mutant condition, it appears that the organism could use different combinations of pathways to restore a ‘normal’ growth state.
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Affiliation(s)
- Satish Kumar
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka, India
| | - Debleena Dey
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka, India
| | - Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka, India
- * E-mail:
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20
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Pinal N, Pichaud F. Dynamin- and Rab5-dependent endocytosis is required to prevent Drosophila photoreceptor degeneration. J Cell Sci 2011; 124:1564-70. [PMID: 21486953 DOI: 10.1242/jcs.082115] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Drosophila photoreceptors, Rhodopsin 1 (ninaE, Rh1) is required for proper morphogenesis and maintenance of the apical light-gathering organelle, the rhabdomere. It has been proposed that Rh1, coupled to the Rho GTPases Rac1 and Cdc42, promotes the morphogenesis of a sub-rhabdomeric F-actin meshwork or rhabdomere terminal web (RTW). The RTW provides mechanical support to the apical microvilli and is likely to guide Rab11-dependent delivery of Rh1-rich membrane to the rhabdomere from the trans Golgi network. However, the nature and function of the molecular pathway involved in RTW morphogenesis remains incomplete. Here, we show that Rh1 function in promoting RTW morphogenesis is light-independent and is conserved throughout evolution. This Rh1 function does not require G(q)α(e), which is required for phototransduction. Finally, we show that interfering with Dynamin- and Rab5-dependent endocytosis leads to a phenotype that is undistinguishable from that of the ninaE-null mutant. Importantly, the corresponding endocytic activity is essential to prevent early onset of rhabdomere degeneration. In conclusion, we propose that Rh1 function in promoting RTW morphogenesis is not only needed to sustain apical membrane delivery but is also required for proper rhabdomeric membrane endocytosis and turnover.
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Affiliation(s)
- Noelia Pinal
- MRC Laboratory for Molecular Cell Biology and Cell Biology Unit, University College London, London, UK
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21
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Tessier CR, Broadie K. The fragile X mental retardation protein developmentally regulates the strength and fidelity of calcium signaling in Drosophila mushroom body neurons. Neurobiol Dis 2011; 41:147-59. [PMID: 20843478 PMCID: PMC2982942 DOI: 10.1016/j.nbd.2010.09.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Revised: 08/17/2010] [Accepted: 09/03/2010] [Indexed: 11/20/2022] Open
Abstract
Fragile X syndrome (FXS) is a broad-spectrum neurological disorder characterized by hypersensitivity to sensory stimuli, hyperactivity and severe cognitive impairment. FXS is caused by loss of the fragile X mental retardation 1 (FMR1) gene, whose FMRP product regulates mRNA translation downstream of synaptic activity to modulate changes in synaptic architecture, function and plasticity. Null Drosophila FMR1 (dfmr1) mutants exhibit reduced learning and loss of protein synthesis-dependent memory consolidation, which is dependent on the brain mushroom body (MB) learning and memory center. We targeted a transgenic GFP-based calcium reporter to the MB in order to analyze calcium dynamics downstream of neuronal activation. In the dfmr1 null MB, there was significant augmentation of the calcium transients induced by membrane depolarization, as well as elevated release of calcium from intracellular organelle stores. The severity of these calcium signaling defects increased with developmental age, although early stages were characterized by highly variable, low fidelity calcium regulation. At the single neuron level, both calcium transient and calcium store release defects were exhibited by dfmr1 null MB neurons in primary culture. Null dfmr1 mutants exhibit reduced brain mRNA expression of calcium-binding proteins, including calcium buffers calmodulin and calbindin, predicting that the inability to appropriately sequester cytosolic calcium may be the common mechanistic defect causing calcium accumulation following both influx and store release. Changes in the magnitude and fidelity of calcium signals in the absence of dFMRP likely contribute to defects in neuronal structure/function, leading to the hallmark learning and memory dysfunction of FXS.
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Affiliation(s)
- Charles R Tessier
- Department of Biological Sciences, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37232, USA
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22
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Hull JJ, Lee JM, Matsumoto S. Gqalpha-linked phospholipase Cbeta1 and phospholipase Cgamma are essential components of the pheromone biosynthesis activating neuropeptide (PBAN) signal transduction cascade. INSECT MOLECULAR BIOLOGY 2010; 19:553-566. [PMID: 20546038 DOI: 10.1111/j.1365-2583.2010.01013.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Sex pheromone production for most moths is regulated by pheromone biosynthesis activating neuropeptide (PBAN). In Bombyx mori, PBAN binding triggers the opening of store-operated Ca(2+) channels, suggesting the involvement of a receptor-activated phospholipase C (PLC). In this study, we found that PLC inhibitors U73122 and compound 48/80 reduced sex pheromone production and that intracellular levels of (3)H-inositol phosphate species increased following PBAN stimulation. In addition, we amplified cDNAs from pheromone glands corresponding to PLCbeta1, PLCbeta4, PLCgamma and two G protein alpha subunits, Go and Gq. In vivo RNA interference-mediated knockdown analyses revealed that BmPLCbeta1, BmGq1, and unexpectedly, BmPLCgamma, are part of the PBAN signal transduction cascade.
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Affiliation(s)
- J J Hull
- Molecular Entomology Laboratory, RIKEN Advanced Science Institute, Wako, Saitama, Japan.
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23
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Inositol 1,4,5-trisphosphate receptor and dSTIM function in Drosophila insulin-producing neurons regulates systemic intracellular calcium homeostasis and flight. J Neurosci 2010; 30:1301-13. [PMID: 20107057 DOI: 10.1523/jneurosci.3668-09.2010] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Calcium (Ca(2+)) signaling is known to regulate the development, maintenance and modulation of activity in neuronal circuits that underlie organismal behavior. In Drosophila, intracellular Ca(2+) signaling by the inositol 1,4,5-trisphosphate receptor and the store-operated channel (dOrai) regulates the formation and function of neuronal circuits that control flight. Here, we show that restoring InsP(3)R activity in insulin-producing neurons of flightless InsP(3)R mutants (itpr) during pupal development can rescue systemic flight ability. Expression of the store operated Ca(2+) entry (SOCE) regulator dSTIM in insulin-producing neurons also suppresses compromised flight ability of InsP(3)R mutants suggesting that SOCE can compensate for impaired InsP(3)R function. Despite restricted expression of wild-type InsP(3)R and dSTIM in insulin-producing neurons, a global restoration of SOCE and store Ca(2+) is observed in primary neuronal cultures from the itpr mutant. These results suggest that restoring InsP(3)R-mediated Ca(2+) release and SOCE in a limited subset of neuromodulatory cells can influence systemic behaviors such as flight by regulating intracellular Ca(2+) homeostasis in a large population of neurons through a non-cell-autonomous mechanism.
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Kain P, Badsha F, Hussain SM, Nair A, Hasan G, Rodrigues V. Mutants in phospholipid signaling attenuate the behavioral response of adult Drosophila to trehalose. Chem Senses 2010; 35:663-73. [PMID: 20543015 DOI: 10.1093/chemse/bjq055] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In Drosophila melanogaster, gustatory receptor genes (Grs) encode putative G-protein-coupled receptors (GPCRs) that are expressed in gustatory receptor neurons (GRNs). One of the Gr genes, Gr5a, encodes a receptor for trehalose that is expressed in a subset of GRNs. Although a role for the G protein, Gsα, has been shown in Gr5a-expressing taste neurons, there is the residual responses to trehalose in Gsα mutants which could suggest additional transduction mechanisms. Expression and genetic analysis of the heterotrimeric G-protein subunit, Gq, shown here suggest involvement of this Gα subunit in trehalose perception in Drosophila. A green fluorescent protein reporter of Gq expression is detected in gustatory neurons in the labellum, tarsal segments, and wing margins. Animals heterozygous for dgq mutations and RNA interference-mediated knockdown of dgq showed reduced responses to trehalose in the proboscis extension reflex assay and feeding behavior assay. These defects were rescued by targeted expression of the wild-type dgqα transgene in the GRNs. These data together with observations from other mutants in phospholipid signaling provide insights into the mechanisms of taste transduction in Drosophila.
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Affiliation(s)
- Pinky Kain
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore 560065, India
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25
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Abstract
A central question in insect chemoreception is whether signaling occurs via G-proteins. Two families of seven-transmembrane-domain chemoreceptors, the odor (Or) and gustatory receptor (Gr) families, have been identified in Drosophila (Clyne et al., 1999, 2000; Vosshall et al., 1999). Ors mediate odor responses, whereas two Grs, Gr21a and Gr63a, mediate CO2 response (Hallem et al., 2004; Jones et al., 2007; Kwon et al., 2007). Using single-sensillum recordings, we systematically investigate the role of Galpha proteins in vivo, initially with RNA interference constructs, competitive peptides, and constitutively active Galpha proteins. The results do not support a role for Galpha proteins in odor sensitivity. In parallel experiments, manipulations of Galpha(q), but not other Galpha proteins, affected CO2 response. Transient, conditional, and ectopic expression analyses consistently supported a role for Galpha(q) in the response of CO2-sensing neurons, but not odor-sensing neurons. Genetic mosaic analysis confirmed that odor responses are normal in the absence of Galpha(q). Ggamma30A is also required for normal CO2 response. The simplest interpretation of these results is that Galpha(q) and Ggamma30A play a role in the response of CO2-sensing neurons, but are not required for Or-mediated odor signaling.
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26
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Hasan G, Venkiteswaran G. The enigma of store-operated ca-entry in neurons: answers from the Drosophila flight circuit. Front Neural Circuits 2010; 4:10. [PMID: 20407638 PMCID: PMC2856631 DOI: 10.3389/fncir.2010.00010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Accepted: 03/18/2010] [Indexed: 12/22/2022] Open
Abstract
In neurons a well-defined source of signaling Ca2+ is the extracellular medium. However, as in all metazoan cells, Ca2+ is also stored in endoplasmic reticular compartments inside neurons. The relevance of these stores in neuronal function has been debatable. The Orai gene encodes a channel that helps refill these stores from the extracellular medium in non-excitable cells through a process called store-operated Ca2+ entry or SOCE. Recent findings have shown that raising the level of Orai or its activator STIM, and consequently SOCE in neurons, can restore flight to varying extents to Drosophila mutants for an intracellular Ca2+-release channel – the inositol 1,4,5-trisphosphate receptor (InsP3R). Both intracellular Ca2+-release and SOCE appear to function in neuro-modulatory domains of the flight circuit during development and acute flight. These findings raise exciting new possibilities for the role of SOCE in vertebrate motor circuit function and the treatment of neurodegenerative disorders where intracellular Ca2+ signaling has been implicated as causative.
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Affiliation(s)
- Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute of Fundamental Research Bangalore, India
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27
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Intracellular Ca2+ signaling and store-operated Ca2+ entry are required in Drosophila neurons for flight. Proc Natl Acad Sci U S A 2009; 106:10326-31. [PMID: 19515818 DOI: 10.1073/pnas.0902982106] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Neuronal Ca(2+) signals can affect excitability and neural circuit formation. Ca(2+) signals are modified by Ca(2+) flux from intracellular stores as well as the extracellular milieu. However, the contribution of intracellular Ca(2+) stores and their release to neuronal processes is poorly understood. Here, we show by neuron-specific siRNA depletion that activity of the recently identified store-operated channel encoded by dOrai and the endoplasmic reticulum Ca(2+) store sensor encoded by dSTIM are necessary for normal flight and associated patterns of rhythmic firing of the flight motoneurons of Drosophila melanogaster. Also, dOrai overexpression in flightless mutants for the Drosophila inositol 1,4,5-trisphosphate receptor (InsP(3)R) can partially compensate for their loss of flight. Ca(2+) measurements show that Orai gain-of-function contributes to the quanta of Ca(2+)-release through mutant InsP(3)Rs and elevates store-operated Ca(2+) entry in Drosophila neurons. Our data show that replenishment of intracellular store Ca(2+) in neurons is required for Drosophila flight.
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28
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Kain P, Chandrashekaran S, Rodrigues V, Hasan G. Drosophila mutants in phospholipid signaling have reduced olfactory responses as adults and larvae. J Neurogenet 2008; 23:303-12. [PMID: 19089787 DOI: 10.1080/01677060802372494] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
In this paper, we show that mutants in the gene stambhA (stmA), which encodes a putative phosphatidylinositol 4,5 bisphosphate-diacylglycerol lipase, exhibit a significant reduction in the amplitudes of odor-evoked responses recorded from the antennal surface of adult Drosophila. This lends support to previously published findings that olfactory transduction in Drosophila requires a phospholipid intermediate. Mutations in stmA also affect the olfactory behavior response of larvae. Moreover, there is a requirement for G(q)alpha and phospholipase Cbeta function in larval olfaction. The results suggest that larval olfactory transduction, like that of the adult, utilizes a phospholipid second messenger, generated by the activation of G(q)alpha and Plcbeta21c, and modulated by the stmA gene product.
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Affiliation(s)
- Pinky Kain
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
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Kain P, Chakraborty TS, Sundaram S, Siddiqi O, Rodrigues V, Hasan G. Reduced odor responses from antennal neurons of G(q)alpha, phospholipase Cbeta, and rdgA mutants in Drosophila support a role for a phospholipid intermediate in insect olfactory transduction. J Neurosci 2008; 28:4745-55. [PMID: 18448651 PMCID: PMC3844817 DOI: 10.1523/jneurosci.5306-07.2008] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Revised: 04/02/2008] [Accepted: 04/02/2008] [Indexed: 11/21/2022] Open
Abstract
Mechanisms by which G-protein-coupled odorant receptors transduce information in insects still need elucidation. We show that mutations in the Drosophila gene for G(q)alpha (dgq) significantly reduce both the amplitude of the field potentials recorded from the whole antenna in responses to odorants as well as the frequency of evoked responses of individual sensory neurons. This requirement for G(q)alpha is for adult function and not during antennal development. Conversely, brief expression of a dominant-active form of G(q)alpha in adults leads to enhanced odor responses. To understand signaling downstream of G(q)alpha in olfactory sensory neurons, genetic interactions of dgq were tested with mutants in genes known to affect phospholipid signaling. dgq mutant phenotypes were further enhanced by mutants in a PLCbeta (phospholipase Cbeta) gene, plc21C. Interestingly although, the olfactory phenotype of mutant alleles of diacylglycerol kinase (rdgA) was rescued by dgq mutant alleles. Our results suggest that G(q)alpha-mediated olfactory transduction in Drosophila requires a phospholipid second messenger the levels of which are regulated by a cycle of phosphatidylinositol 1,4-bisphosphate breakdown and regeneration.
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Affiliation(s)
- Pinky Kain
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India, and
| | - Tuhin Subra Chakraborty
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India, and
| | - Susinder Sundaram
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai 400005, India
| | - Obaid Siddiqi
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India, and
| | - Veronica Rodrigues
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India, and
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai 400005, India
| | - Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India, and
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Xia S, Tully T. Segregation of odor identity and intensity during odor discrimination in Drosophila mushroom body. PLoS Biol 2008; 5:e264. [PMID: 17914903 PMCID: PMC1994992 DOI: 10.1371/journal.pbio.0050264] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2006] [Accepted: 08/09/2007] [Indexed: 01/12/2023] Open
Abstract
Molecular and cellular studies have begun to unravel a neurobiological basis of olfactory processing, which appears conserved among vertebrate and invertebrate species. Studies have shown clearly that experience-dependent coding of odor identity occurs in “associative” olfactory centers (the piriform cortex in mammals and the mushroom body [MB] in insects). What remains unclear, however, is whether associative centers also mediate innate (spontaneous) odor discrimination and how ongoing experience modifies odor discrimination. Here we show in naïve flies that Gαq-mediated signaling in MB modulates spontaneous discrimination of odor identity but not odor intensity (concentration). In contrast, experience-dependent modification (conditioning) of both odor identity and intensity occurs in MB exclusively via Gαs-mediated signaling. Our data suggest that spontaneous responses to odor identity and odor intensity discrimination are segregated at the MB level, and neural activity from MB further modulates olfactory processing by experience-independent Gαq-dependent encoding of odor identity and by experience-induced Gαs-dependent encoding of odor intensity and identity. Considerable progress has been made in understanding how olfaction works as the receptor proteins, sensory neurons, and brain circuitry responsible have become increasingly well-characterized. However, olfactory processing in higher brain centers, where neuronal activity is assembled into the perception of odor quality, is poorly understood. Here, we have addressed how the mushroom body (MB)—a secondary olfactory center—is involved in olfactory discrimination. We manipulated the MB by ablation, disruption of synaptic transmission, and interruption of key cellular signaling molecules in naïve flies and in flies trained to discriminate odors. We first show that although both odor identity and intensity are encoded in the MB, only the former requires Gαq-dependent signaling and is necessary for naïve flies to spontaneously discriminate different odors. We then show that training flies to alter their olfactory response requires Gαs-mediated signaling in MB for both odor intensity and odor identity. We have thus identified (i) segregation of odor identity and odor intensity at the MB level in naïve flies and (ii) different G-protein-dependent signaling pathways for spontaneous versus experience-dependent olfactory discrimination. Experience-dependent modification of odor identity and intensity occurs in the mushroom body (MB) of flies exclusively via Gαs-mediated signaling. In contrast, Gαq-mediated signaling in MB modulates spontaneous discrimination of odor identity but not odor intensity.
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Affiliation(s)
- Shouzhen Xia
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - Tim Tully
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
- * To whom correspondence should be addressed. E-mail:
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Nair S, Agrawal N, Hasan G. Homeostasis of glutamate neurotransmission is altered in Drosophila Inositol 1,4,5-trisphosphate receptor mutants. INVERTEBRATE NEUROSCIENCE 2007; 7:137-47. [PMID: 17492321 DOI: 10.1007/s10158-007-0048-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Accepted: 04/25/2007] [Indexed: 12/01/2022]
Abstract
Mutants in the Drosophila InsP3R gene (itpr) are flight defective. Expression of the wild-type InsP3R in aminergic interneurons rescues flight. However, molecular and cellular changes in the central nervous system of InsP3R mutants that lead to flightless behavior remain unknown. To understand the molecular basis of flight phenotypes in Drosophila InsP3R mutants a microarray screen was done with RNA isolated from adult heads and thoraces. We found down-regulation of several genes that affect the excitability of neurons and muscles. Among these the role of glutamine synthetase 2 was investigated further. This enzyme reduces glutamate levels at the synapse. Our results show that Gs2 (glutamine synthetase 2) transcripts and glutamate levels correspond precisely but inversely, with InsP3R phenotypes, which can be rescued by a mutant allele for Gs2, namely, Gs2(m13). From measuring axonal branches and synapse number at a glutamatergic synapse--the adult flight neuromuscular junction--of InsP3R mutants, we conclude that glutamate homeostasis is altered through a cell non-autonomous mechanism, and is likely to be an important basis for the observed flight defects.
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Affiliation(s)
- Shalima Nair
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore, 560065, India
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