1
|
Rysiewicz B, Błasiak E, Dziedzicka-Wasylewska M, Polit A. The polybasic region in Gαi proteins: Relevant or not? Insights from Gαi 3 research. Cell Signal 2024; 118:111138. [PMID: 38467243 DOI: 10.1016/j.cellsig.2024.111138] [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: 09/25/2023] [Revised: 02/18/2024] [Accepted: 03/08/2024] [Indexed: 03/13/2024]
Abstract
Heterotrimeric G proteins are responsible for signal transduction from G-protein-coupled receptors (GPCRs) to intracellular effectors. This process is only possible when G proteins are located on the inner side of the cell membrane due to the specific localization of GPCR receptors. The Gα subunit is directed to the cell membrane through several signals, including modification by fatty acid moieties, interaction with the Gβγ complex, and, as observed in some Gα proteins, the presence of basic amino acid residues in the N-terminal region. In this work, we focused on investigating the influence of the polybasic region on the localization and function of a representative member of the Gαi family, Gαi3. Through the use of confocal microscopy and fluorescence lifetime microscopy, we showed that, in the case of this protein, neutralizing the positive charge does not significantly affect its abundance in the cell membrane. However, it does affect its spatial arrangement concerning the dopamine D2 receptor and influences inhibitory effect of Gαi3 on intracellular cAMP production triggered by D2 receptor stimulation. Moreover, in this work, we have shown, for the first time, that nonlipidated Gαi3 binds to negatively charged lipids through electrostatic interactions, and membrane fluidity plays a significant role in this interaction.
Collapse
Affiliation(s)
- Beata Rysiewicz
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
| | - Ewa Błasiak
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
| | - Marta Dziedzicka-Wasylewska
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
| | - Agnieszka Polit
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
| |
Collapse
|
2
|
Chung YK, Wong YH. Re‐examining the ‘Dissociation Model’ of G protein activation from the perspective of Gβγ signaling. FEBS J 2020; 288:2490-2501. [DOI: 10.1111/febs.15605] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Revised: 10/14/2020] [Accepted: 10/19/2020] [Indexed: 12/27/2022]
Affiliation(s)
- Yin Kwan Chung
- Division of Life Science and Biotechnology Research Institute Hong Kong University of Science and Technology Hong Kong China
| | - Yung Hou Wong
- Division of Life Science and Biotechnology Research Institute Hong Kong University of Science and Technology Hong Kong China
- State Key Laboratory of Molecular Neuroscience the Molecular Neuroscience Center Hong Kong University of Science and Technology Kowloon China
| |
Collapse
|
3
|
van den Bos E, Ambrosy B, Horsthemke M, Walbaum S, Bachg AC, Wettschureck N, Innamorati G, Wilkie TM, Hanley PJ. Knockout mouse models reveal the contributions of G protein subunits to complement C5a receptor-mediated chemotaxis. J Biol Chem 2020; 295:7726-7742. [PMID: 32332099 DOI: 10.1074/jbc.ra119.011984] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 04/22/2020] [Indexed: 01/20/2023] Open
Abstract
G protein-coupled receptor signaling is required for the navigation of immune cells along chemoattractant gradients. However, chemoattractant receptors may couple to more than one type of heterotrimeric G protein, each of which consists of a Gα, Gβ, and Gγ subunit, making it difficult to delineate the critical signaling pathways. Here, we used knockout mouse models and time-lapse microscopy to elucidate Gα and Gβ subunits contributing to complement C5a receptor-mediated chemotaxis. Complement C5a-mediated chemokinesis and chemotaxis were almost completely abolished in macrophages lacking Gnai2 (encoding Gαi2), consistent with a reduced leukocyte recruitment previously observed in Gnai2 -/- mice, whereas cells lacking Gnai3 (Gαi3) exhibited only a slight decrease in cell velocity. Surprisingly, C5a-induced Ca2+ transients and lamellipodial membrane spreading were persistent in Gnai2 -/- macrophages. Macrophages lacking both Gnaq (Gαq) and Gna11 (Gα11) or both Gna12 (Gα12) and Gna13 (Gα13) had essentially normal chemotaxis, Ca2+ signaling, and cell spreading, except Gna12/Gna13-deficient macrophages had increased cell velocity and elongated trailing ends. Moreover, Gnaq/Gna11-deficient cells did not respond to purinergic receptor P2Y2 stimulation. Genetic deletion of Gna15 (Gα15) virtually abolished C5a-induced Ca2+ transients, but chemotaxis and cell spreading were preserved. Homozygous Gnb1 (Gβ1) deletion was lethal, but mice lacking Gnb2 (Gβ2) were viable. Gnb2 -/- macrophages exhibited robust Ca2+ transients and cell spreading, albeit decreased cell velocity and impaired chemotaxis. In summary, complement C5a-mediated chemotaxis requires Gαi2 and Gβ2, but not Ca2+ signaling, and membrane protrusive activity is promoted by G proteins that deplete phosphatidylinositol 4,5-bisphosphate.
Collapse
Affiliation(s)
- Esther van den Bos
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Benjamin Ambrosy
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Markus Horsthemke
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Stefan Walbaum
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Anne C Bachg
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Nina Wettschureck
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Giulio Innamorati
- Department of Surgical Sciences, Dentistry, Gynecology and Pediatrics, University of Verona, Verona, Italy
| | - Thomas M Wilkie
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Peter J Hanley
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| |
Collapse
|
4
|
Greenwood IA, Stott JB. The Gβ1 and Gβ3 Subunits Differentially Regulate Rat Vascular Kv7 Channels. Front Physiol 2020; 10:1573. [PMID: 31992990 PMCID: PMC6971187 DOI: 10.3389/fphys.2019.01573] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 12/16/2019] [Indexed: 11/17/2022] Open
Abstract
Within the vasculature Kv7 channels are key regulators of basal tone and contribute to a variety of receptor mediated vasorelaxants. The Kv7.4 isoform, abundant within the vasculature, is key to these processes and was recently shown to have an obligatory requirement of G-protein βγ subunits for its voltage dependent activity. There is an increasing appreciation that with 5 Gβ subunits and 12 Gγ subunits described in mammalian cells that different Gβxγx combinations can confer selectivity in Gβγ effector stimulation. Therefore, we aimed to characterize the Gβ subunit(s) which basally regulate Kv7.4 channels and native vascular Kv7 channels. In Chinese Hamster Ovary cells overexpressing Kv7.4 and different Gβx subunits only Gβ1, Gβ3, and Gβ5 enhanced Kv7.4 currents, increasing the activation kinetics and negatively shifting the voltage dependence of activation. In isolated rat renal artery myocytes, proximity ligation assay detected an interaction of Kv7.4 with Gβ1 and Gβ3 subunits, but not other isoforms. Morpholino directed knockdown of Gβ1 in rat renal arteries did not alter Kv7 dependent currents but reduced Kv7.4 protein expression. Knockdown of Gβ3 in rat renal arteries resulted in decreased basal K+ currents which were not sensitive to pharmacological inhibition of Kv7 channels. These studies implicate the Gβ1 subunit in the synthesis or stability of Kv7.4 proteins, whilst revealing that the Gβ3 isoform is responsible for the basal activity of Kv7 channels in native rat renal myocytes. These findings demonstrate that different Gβ subunits have important individual roles in ion channel regulation.
Collapse
Affiliation(s)
- Iain A Greenwood
- Vascular Biology Research Centre, Institute of Molecular and Clinical Sciences, St George's University of London, London, United Kingdom
| | - Jennifer B Stott
- Vascular Biology Research Centre, Institute of Molecular and Clinical Sciences, St George's University of London, London, United Kingdom
| |
Collapse
|
5
|
Targeting G protein-coupled receptor signaling at the G protein level with a selective nanobody inhibitor. Nat Commun 2018; 9:1996. [PMID: 29777099 PMCID: PMC5959942 DOI: 10.1038/s41467-018-04432-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2017] [Accepted: 04/25/2018] [Indexed: 01/06/2023] Open
Abstract
G protein-coupled receptors (GPCRs) activate heterotrimeric G proteins by mediating a GDP to GTP exchange in the Gα subunit. This leads to dissociation of the heterotrimer into Gα-GTP and Gβγ dimer. The Gα-GTP and Gβγ dimer each regulate a variety of downstream pathways to control various aspects of human physiology. Dysregulated Gβγ-signaling is a central element of various neurological and cancer-related anomalies. However, Gβγ also serves as a negative regulator of Gα that is essential for G protein inactivation, and thus has the potential for numerous side effects when targeted therapeutically. Here we report a llama-derived nanobody (Nb5) that binds tightly to the Gβγ dimer. Nb5 responds to all combinations of β-subtypes and γ-subtypes and competes with other Gβγ-regulatory proteins for a common binding site on the Gβγ dimer. Despite its inhibitory effect on Gβγ-mediated signaling, Nb5 has no effect on Gαq-mediated and Gαs-mediated signaling events in living cells.
Collapse
|
6
|
|
7
|
Meena NP, Kimmel AR. Chemotactic network responses to live bacteria show independence of phagocytosis from chemoreceptor sensing. eLife 2017; 6. [PMID: 28541182 PMCID: PMC5476428 DOI: 10.7554/elife.24627] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 05/24/2017] [Indexed: 12/21/2022] Open
Abstract
Aspects of innate immunity derive from characteristics inherent to phagocytes, including chemotaxis toward and engulfment of unicellular organisms or cell debris. Ligand chemotaxis has been biochemically investigated using mammalian and model systems, but precision of chemotaxis towards ligands being actively secreted by live bacteria is not well studied, nor has there been systematic analyses of interrelationships between chemotaxis and phagocytosis. The genetic/molecular model Dictyostelium and mammalian phagocytes share mechanistic pathways for chemotaxis and phagocytosis; Dictyostelium chemotax toward bacteria and phagocytose them as food sources. We quantified Dictyostelium chemotaxis towards live gram positive and gram negative bacteria and demonstrate high sensitivity to multiple bacterially-secreted chemoattractants. Additive/competitive assays indicate that intracellular signaling-networks for multiple ligands utilize independent upstream adaptive mechanisms, but common downstream targets, thus amplifying detection at low signal propagation, but strengthening discrimination of multiple inputs. Finally, analyses of signaling-networks for chemotaxis and phagocytosis indicate that chemoattractant receptor-signaling is not essential for bacterial phagocytosis. DOI:http://dx.doi.org/10.7554/eLife.24627.001
Collapse
Affiliation(s)
- Netra Pal Meena
- Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, The National Institutes of Health, Bethesda, United States
| | - Alan R Kimmel
- Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, The National Institutes of Health, Bethesda, United States
| |
Collapse
|
8
|
Somatostatin activates Ras and ERK1/2 via a G protein βγ-subunit-initiated pathway in thyroid cells. Mol Cell Biochem 2015; 411:253-60. [PMID: 26472731 DOI: 10.1007/s11010-015-2587-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 10/08/2015] [Indexed: 10/22/2022]
Abstract
Somatostatin (SST) is one of the main regulators of thyroid function. It acts by binding to its receptors, which lead to the dissociation of G proteins into Gαi and Gβγ subunits. However, much less is known about the function of Gβγ in thyroid cells. Here, we studied the role of SST and Gβγ dimers released upon SST stimulation on the Ras-ERK1/2 pathway in FTRL-5 thyroid cells. We demonstrate that SST activates Ras through Gi proteins, since SST-induced Ras activation is inhibited by pertussis toxin. Moreover, the specific sequestration of Gβγ dimers decreases Ras-GTP and phosphorylated ERK1/2 levels, and overexpression of Gβγ increases ERK1/2 phosphorylation induced by SST, indicating that Gβγ dimers released after SST treatment mediate activation of Ras and ERK1/2. On the other hand, SST treatment does not modify the expression of the thyroid differentiation marker sodium/iodide symporter (NIS) through ERK1/2 activation. However, SST increases AKT activation and the inhibition of the Src/PI3K/AKT pathway increases NIS levels in SST-treated cells. Thus, we conclude that, in thyroid cells, signalling from SST receptors to ERK1/2 involves a Gβγ-mediated signal acting on a Ras-dependent pathway. Moreover, we demonstrate that SST might regulates NIS expression through a Src/PI3K/AKT-dependent mechanism, but not through ERK1/2 signalling, showing the main role of this hormone in thyroid function.
Collapse
|
9
|
Khan SM, Min A, Gora S, Houranieh GM, Campden R, Robitaille M, Trieu P, Pétrin D, Jacobi AM, Behlke MA, Angers S, Hébert TE. Gβ 4 γ 1 as a modulator of M3 muscarinic receptor signalling and novel roles of Gβ 1 subunits in the modulation of cellular signalling. Cell Signal 2015; 27:1597-608. [DOI: 10.1016/j.cellsig.2015.04.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 04/16/2015] [Accepted: 04/17/2015] [Indexed: 01/01/2023]
|
10
|
Kamato D, Thach L, Bernard R, Chan V, Zheng W, Kaur H, Brimble M, Osman N, Little PJ. Structure, Function, Pharmacology, and Therapeutic Potential of the G Protein, Gα/q,11. Front Cardiovasc Med 2015; 2:14. [PMID: 26664886 PMCID: PMC4671355 DOI: 10.3389/fcvm.2015.00014] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 03/11/2015] [Indexed: 11/19/2022] Open
Abstract
G protein coupled receptors (GPCRs) are one of the major classes of cell surface receptors and are associated with a group of G proteins consisting of three subunits termed alpha, beta, and gamma. G proteins are classified into four families according to their α subunit; Gαi, Gαs, Gα12/13, and Gαq. There are several downstream pathways of Gαq of which the best known is upon activation via guanosine triphosphate (GTP), Gαq activates phospholipase Cβ, hydrolyzing phosphatidylinositol 4,5-biphosphate into diacylglycerol and inositol triphosphate and activating protein kinase C and increasing calcium efflux from the endoplasmic reticulum. Although G proteins, in particular, the Gαq/11 are central elements in GPCR signaling, their actual roles have not yet been thoroughly investigated. The lack of research of the role on Gαq/11 in cell biology is partially due to the obscure nature of the available pharmacological agents. YM-254890 is the most useful Gαq-selective inhibitor with antiplatelet, antithrombotic, and thrombolytic effects. YM-254890 inhibits Gαq signaling pathways by preventing the exchange of guanosine diphosphate for GTP. UBO-QIC is a structurally similar compound to YM-254890, which can inhibit platelet aggregation and cause vasorelaxation in rats. Many agents are available for the study of signaling downstream of Gαq/11. The role of G proteins could potentially represent a novel therapeutic target. This review will explore the range of pharmacological and molecular tools available for the study of the role of Gαq/11 in GPCR signaling.
Collapse
Affiliation(s)
- Danielle Kamato
- Discipline of Pharmacy, Diabetes Complications Group, School of Medical Sciences, Health Innovations Research Institute, RMIT University , Bundoora, VIC , Australia
| | - Lyna Thach
- Discipline of Pharmacy, Diabetes Complications Group, School of Medical Sciences, Health Innovations Research Institute, RMIT University , Bundoora, VIC , Australia
| | - Rebekah Bernard
- Discipline of Pharmacy, Diabetes Complications Group, School of Medical Sciences, Health Innovations Research Institute, RMIT University , Bundoora, VIC , Australia
| | - Vincent Chan
- Discipline of Pharmacy, Diabetes Complications Group, School of Medical Sciences, Health Innovations Research Institute, RMIT University , Bundoora, VIC , Australia
| | - Wenhua Zheng
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Centre , Guangzhou , China ; Faculty of Health Sciences, University of Macau , Macau , China
| | - Harveen Kaur
- Department of Chemistry, University of Auckland , Auckland , New Zealand
| | - Margaret Brimble
- Department of Chemistry, University of Auckland , Auckland , New Zealand
| | - Narin Osman
- Discipline of Pharmacy, Diabetes Complications Group, School of Medical Sciences, Health Innovations Research Institute, RMIT University , Bundoora, VIC , Australia
| | - Peter J Little
- Discipline of Pharmacy, Diabetes Complications Group, School of Medical Sciences, Health Innovations Research Institute, RMIT University , Bundoora, VIC , Australia
| |
Collapse
|
11
|
Canonical and noncanonical g-protein signaling helps coordinate actin dynamics to promote macrophage phagocytosis of zymosan. Mol Cell Biol 2014; 34:4186-99. [PMID: 25225330 DOI: 10.1128/mcb.00325-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Both chemotaxis and phagocytosis depend upon actin-driven cell protrusions and cell membrane remodeling. While chemoattractant receptors rely upon canonical G-protein signaling to activate downstream effectors, whether such signaling pathways affect phagocytosis is contentious. Here, we report that Gαi nucleotide exchange and signaling helps macrophages coordinate the recognition, capture, and engulfment of zymosan bioparticles. We show that zymosan exposure recruits F-actin, Gαi proteins, and Elmo1 to phagocytic cups and early phagosomes. Zymosan triggered an increase in intracellular Ca(2+) that was partially sensitive to Gαi nucleotide exchange inhibition and expression of GTP-bound Gαi recruited Elmo1 to the plasma membrane. Reducing GDP-Gαi nucleotide exchange, decreasing Gαi expression, pharmacologically interrupting Gβγ signaling, or reducing Elmo1 expression all impaired phagocytosis, while favoring the duration that Gαi remained GTP bound promoted it. Our studies demonstrate that targeting heterotrimeric G-protein signaling offers opportunities to enhance or retard macrophage engulfment of phagocytic targets such as zymosan.
Collapse
|
12
|
Khan SM, Sleno R, Gora S, Zylbergold P, Laverdure JP, Labbé JC, Miller GJ, Hébert TE. The expanding roles of Gβγ subunits in G protein-coupled receptor signaling and drug action. Pharmacol Rev 2013; 65:545-77. [PMID: 23406670 DOI: 10.1124/pr.111.005603] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Gβγ subunits from heterotrimeric G proteins perform a vast array of functions in cells with respect to signaling, often independently as well as in concert with Gα subunits. However, the eponymous term "Gβγ" does not do justice to the fact that 5 Gβ and 12 Gγ isoforms have evolved in mammals to serve much broader roles beyond their canonical roles in cellular signaling. We explore the phylogenetic diversity of Gβγ subunits with a view toward understanding these expanded roles in different cellular organelles. We suggest that the particular content of distinct Gβγ subunits regulates cellular activity, and that the granularity of individual Gβ and Gγ action is only beginning to be understood. Given the therapeutic potential of targeting Gβγ action, this larger view serves as a prelude to more specific development of drugs aimed at individual isoforms.
Collapse
Affiliation(s)
- Shahriar M Khan
- Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir-William-Osler, Room 1303, Montréal, Québec H3G 1Y6, Canada
| | | | | | | | | | | | | | | |
Collapse
|
13
|
Mahmoud S, Yun JK, Ruiz-Velasco V. Gβ2 and Gβ4 participate in the opioid and adrenergic receptor-mediated Ca2+ channel modulation in rat sympathetic neurons. J Physiol 2012; 590:4673-89. [PMID: 22711958 DOI: 10.1113/jphysiol.2012.237644] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Cardiac function is regulated in part by the sympathetic branch of the autonomic nervous system via the stellate ganglion (SG) neurons. Neurotransmitters, such as noradrenaline (NA), and neuropeptides, including nociceptin (Noc), influence the excit ability of SG neurons by modulating Ca(2+) channel function following activation of the adrenergic and nociceptin/orphanin FQ peptide (NOP) opioid receptors, respectively. The regulation of Ca(2+) channels is mediated by Gβγ, but the specific Gβ subunit that modulates the channels is not known. In the present study, small interference RNA (siRNA) was employed to silence the natively expressed Gβ proteins in rat SG tissue and to examine the coupling specificity of adrenergic and NOP opioid receptors to Ca(2+) channels employing the whole-cell variant of the patch-clamp technique.Western blotting analysis showed that Gβ1, Gβ2 and Gβ4 are natively expressed. The knockdown of Gβ2 or Gβ4 led to a significant decrease of the NA- and Noc-mediated Ca(2+)current inhibition, while Gβ1 silencing was without effect. However, sustaining low levels of Gβ2 resulted in an increased expression of Gβ4 and a concomitant compensation of both adrenergic and opioid signalling pathways modulating Ca(2+) channels. Conversely, Gβ4-directed siRNA was not accompanied with a compensation of the signalling pathway. Finally, the combined silencing of Gβ2 and Gβ4 prevented any additional compensatory mechanisms.Overall, our studies suggest that in SG neurons, Gβ2 and Gβ4 normally maintain the coupling of Ca(2+) channels with the receptors, with the latter subtype responsible for maintaining the integrity of both pathways.
Collapse
Affiliation(s)
- Saifeldin Mahmoud
- Department of Anesthesiology, Penn State College of Medicine, Hershey, PA 17033-0850, USA
| | | | | |
Collapse
|
14
|
Abstract
Opioid analgesics elicit their effects via activation of the mu-opioid receptor (MOR), a G protein-coupled receptor known to interact with Gα(i/o)-type G proteins. Work in vitro has suggested that MOR couples preferentially to the abundant brain Gα(i/o) isoform, Gα(o). However, studies in vivo evaluating morphine-mediated antinociception have not supported these findings. The aim of the present work was to evaluate the contribution of Gα(o) to MOR-dependent signaling by measuring both antinociceptive and biochemical endpoints in a Gα(o) null transgenic mouse strain. Male wild-type and Gα(o) heterozygous null (Gα(o) ⁺/⁻) mice were tested for opioid antinociception in the hot plate test or the warm-water tail withdrawal test as measures of supraspinal or spinal antinociception, respectively. Reduction in Gα(o) levels attenuated the supraspinal antinociception produced by morphine, methadone, and nalbuphine, with the magnitude of suppression dependent on agonist efficacy. This was explained by a reduction in both high-affinity MOR expression and MOR agonist-stimulated G protein activation in whole brain homogenates from Gα(o) ⁺/⁻ and Gα(o) homozygous null (Gα(o)⁻/⁻) mice, compared with wild-type littermates. On the other hand, morphine spinal antinociception was not different between Gα(o) ⁺/⁻ and wild-type mice and high-affinity MOR expression was unchanged in spinal cord tissue. However, the action of the partial agonist nalbuphine was compromised, showing that reduction in Gα(o) protein does decrease spinal antinociception, but suggesting a higher Gα(o) protein reserve. These results provide the first in vivo evidence that Gα(o) contributes to maximally efficient MOR signaling and antinociception.
Collapse
|
15
|
Zhang Y, Tang W, Jones MC, Xu W, Halene S, Wu D. Different roles of G protein subunits beta1 and beta2 in neutrophil function revealed by gene expression silencing in primary mouse neutrophils. J Biol Chem 2010; 285:24805-14. [PMID: 20525682 PMCID: PMC2915716 DOI: 10.1074/jbc.m110.142885] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 06/03/2010] [Indexed: 11/06/2022] Open
Abstract
Neutrophils play important roles in host innate immunity and various inflammation-related diseases. In addition, neutrophils represent an excellent system for studying directional cell migration. However, neutrophils are terminally differentiated cells that are short lived and refractory to transfection; thus, they are not amenable for existing gene silencing techniques. Here we describe the development of a method to silence gene expression efficiently in primary mouse neutrophils. A mouse stem cell virus-based retroviral vector was modified to express short hairpin RNAs and fluorescent marker protein at high levels in hematopoietic cells and used to infect mouse bone marrow cells prior to reconstitution of the hematopoietic system in lethally irradiated mice. This method was used successfully to silence the expression of Gbeta(1) and/or Gbeta(2) in mouse neutrophils. Knockdown of Gbeta(2) appeared to affect primarily the directionality of neutrophil chemotaxis rather than motility, whereas knockdown of Gbeta(1) had no significant effect. However, knockdown of both Gbeta(1) and Gbeta(2) led to significant reduction in motility and responsiveness. In addition, knockdown of Gbeta(1) but not Gbeta(2) inhibited the ability of neutrophils to kill ingested bacteria, and only double knockdown resulted in significant reduction in bacterial phagocytosis. Therefore, we have developed a short hairpin RNA-based method to effectively silence gene expression in mouse neutrophils for the first time, which allowed us to uncover divergent roles of Gbeta(1) and Gbeta(2) in the regulation of neutrophil functions.
Collapse
Affiliation(s)
- Yong Zhang
- From the Program in Vascular Biology and Therapeutics and Department of Pharmacology and
| | - Wenwen Tang
- From the Program in Vascular Biology and Therapeutics and Department of Pharmacology and
| | - Matthew C. Jones
- From the Program in Vascular Biology and Therapeutics and Department of Pharmacology and
| | - Wenwen Xu
- From the Program in Vascular Biology and Therapeutics and Department of Pharmacology and
| | - Stephanie Halene
- Section of Hematology, Department of Medicine, Yale School of Medicine, New Haven, Connecticut 06520
| | - Dianqing Wu
- From the Program in Vascular Biology and Therapeutics and Department of Pharmacology and
| |
Collapse
|
16
|
Jernigan KK, Cselenyi CS, Thorne CA, Hanson AJ, Tahinci E, Hajicek N, Oldham WM, Lee LA, Hamm HE, Hepler JR, Kozasa T, Linder ME, Lee E. Gbetagamma activates GSK3 to promote LRP6-mediated beta-catenin transcriptional activity. Sci Signal 2010; 3:ra37. [PMID: 20460648 PMCID: PMC3088111 DOI: 10.1126/scisignal.2000647] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Evidence from Drosophila and cultured cell studies supports a role for heterotrimeric guanosine triphosphate-binding proteins (G proteins) in Wnt signaling. Wnt inhibits the degradation of the transcriptional regulator beta-catenin. We screened the alpha and betagamma subunits of major families of G proteins in a Xenopus egg extract system that reconstitutes beta-catenin degradation. We found that Galpha(o), Galpha(q), Galpha(i2), and Gbetagamma inhibited beta-catenin degradation. Gbeta(1)gamma(2) promoted the phosphorylation and activation of the Wnt co-receptor low-density lipoprotein receptor-related protein 6 (LRP6) by recruiting glycogen synthase kinase 3 (GSK3) to the membrane and enhancing its kinase activity. In both a reporter gene assay and an in vivo assay, c-betaARK (C-terminal domain of beta-adrenergic receptor kinase), an inhibitor of Gbetagamma, blocked LRP6 activity. Several components of the Wnt-beta-catenin pathway formed a complex: Gbeta(1)gamma(2), LRP6, GSK3, axin, and dishevelled. We propose that free Gbetagamma and Galpha subunits, released from activated G proteins, act cooperatively to inhibit beta-catenin degradation and activate beta-catenin-mediated transcription.
Collapse
Affiliation(s)
- Kristin K. Jernigan
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee, 37232, USA
| | - Christopher S. Cselenyi
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee, 37232, USA
| | - Curtis A. Thorne
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee, 37232, USA
| | - Alison J. Hanson
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee, 37232, USA
| | - Emilios Tahinci
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee, 37232, USA
| | - Nicole Hajicek
- Department of Pharmacology, University of Illinois, Chicago, Illinois, 60612, USA
- Research Center for Advanced Science and Technology, The University of Tokyo, 153- 8904, Japan
| | - William M. Oldham
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, 37232, USA
| | - Laura A. Lee
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee, 37232, USA
| | - Heidi E. Hamm
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, 37232, USA
| | - John R. Hepler
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia, 30322, USA
| | - Tohru Kozasa
- Department of Pharmacology, University of Illinois, Chicago, Illinois, 60612, USA
- Research Center for Advanced Science and Technology, The University of Tokyo, 153- 8904, Japan
| | - Maurine E. Linder
- Department of Molecular Medicine, Cornell University, Ithaca, New York, 14853, USA
| | - Ethan Lee
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee, 37232, USA
- Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee, 37232, USA
| |
Collapse
|
17
|
Lee SH, Koo KH, Park JW, Kim HJ, Ye SK, Park JB, Park BK, Kim YN. HIF-1 is induced via EGFR activation and mediates resistance to anoikis-like cell death under lipid rafts/caveolae-disrupting stress. Carcinogenesis 2010; 30:1997-2004. [PMID: 19789263 DOI: 10.1093/carcin/bgp233] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The plasma membrane microdomains, lipid rafts, are involved in regulation of cellular functions such as cell survival and adhesion. Cholesterol is a critical component of lipid rafts in terms of their integrity and functions and rafts disruption by cholesterol depletion can induce detachment-induced cell death. Hypoxia inducible factor-1 (HIF-1) alpha is stabilized in hypoxia and transactivates numerous genes required for cellular adaptation to hypoxia. It is also induced by non-hypoxic stimuli and contributes to cell survival. Because hypoxia inhibits cholesterol synthesis and HIF-1alpha plays a role in this process, we here explored a possible connection between lipid rafts and HIF-1alpha. We investigated whether HIF-1alpha is regulated during cholesterol depletion/rafts disruption in A431 cells in normoxic conditions. Methyl-beta cyclodextrin (MbetaCD), which induces cholesterol depletion, upregulated HIF-1alpha even under normoxic conditions and this upregulation required epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase 1 and 2 activation, but not Akt activation. MbetaCD treatment induced HIF-1alpha upregulation at both the transcriptional and translational levels but not at the posttranslational levels. In addition, MbetaCD robustly induced vascular endothelial growth factor production and stimulated an hypoxia response element-driven luciferase reporter activity under normoxic conditions, indicating that MbetaCD-induced HIF-1alpha is functionally activated. Both EGFR activity and HIF-1alpha expression were higher in the attached cells than in the detached cells after MbetaCD treatment. Furthermore, inhibition of HIF-1alpha by RNA interference accelerated cell detachment, thus increasing cell death, indicating that HIF-1alpha expression attenuates MbetaCD-induced anoikis-like cell death. These data suggest that, depending on cholesterol levels, lipid rafts or membrane fluidity are probably to regulate HIF-1alpha expression in normoxia by modulating rafts protein activities such as EGFR, and this connection between lipid rafts and HIF-1alpha regulation may provide cell survival under membrane-disturbing stress.
Collapse
Affiliation(s)
- Seong-Hee Lee
- Pediatric Oncology Branch, Division of Translational & Clinical Research II, National Cancer Center, 809 Madu 1-dong, Ilsan-gu Goyang-si, Gyeonggi-do, 411-769, Korea
| | | | | | | | | | | | | | | |
Collapse
|
18
|
The interaction of nucleoside diphosphate kinase B with Gbetagamma dimers controls heterotrimeric G protein function. Proc Natl Acad Sci U S A 2009; 106:16269-74. [PMID: 19805292 DOI: 10.1073/pnas.0901679106] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Heterotrimeric G proteins in physiological and pathological processes have been extensively studied so far. However, little is known about mechanisms regulating the cellular content and compartmentalization of G proteins. Here, we show that the association of nucleoside diphosphate kinase B (NDPK B) with the G protein betagamma dimer (Gbetagamma) is required for G protein function in vivo. In zebrafish embryos, morpholino-mediated knockdown of zebrafish NDPK B, but not NDPK A, results in a severe decrease in cardiac contractility. The depletion of NDPK B is associated with a drastic reduction in Gbeta(1)gamma(2) dimer expression. Moreover, the protein levels of the adenylyl cyclase (AC)-regulating Galpha(s) and Galpha(i) subunits as well as the caveolae scaffold proteins caveolin-1 and -3 are strongly reduced. In addition, the knockdown of the zebrafish Gbeta(1) orthologs, Gbeta(1) and Gbeta(1like), causes a cardiac phenotype very similar to that of NDPK B morphants. The loss of Gbeta(1)/Gbeta(1like) is associated with a down-regulation in caveolins, AC-regulating Galpha-subunits, and most important, NDPK B. A comparison of embryonic fibroblasts from wild-type and NDPK A/B knockout mice demonstrate a similar reduction of G protein, caveolin-1 and basal cAMP content in mammalian cells that can be rescued by re-expression of human NDPK B. Thus, our results suggest a role for the interaction of NDPK B with Gbetagamma dimers and caveolins in regulating membranous G protein content and maintaining normal G protein function in vivo.
Collapse
|
19
|
Dupré DJ, Robitaille M, Rebois RV, Hébert TE. The role of Gbetagamma subunits in the organization, assembly, and function of GPCR signaling complexes. Annu Rev Pharmacol Toxicol 2009; 49:31-56. [PMID: 18834311 DOI: 10.1146/annurev-pharmtox-061008-103038] [Citation(s) in RCA: 212] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The role of Gbetagamma subunits in cellular signaling has become well established in the past 20 years. Not only do they regulate effectors once thought to be the sole targets of Galpha subunits, but it has become clear that they also have a unique set of binding partners and regulate signaling pathways that are not always localized to the plasma membrane. However, this may be only the beginning of the story. Gbetagamma subunits interact with G protein-coupled receptors, Galpha subunits, and several different effector molecules during assembly and trafficking of receptor-based signaling complexes and not simply in response to ligand stimulation at sites of receptor cellular activity. Gbetagamma assembly itself seems to be tightly regulated via the action of molecular chaperones and in turn may serve a similar role in the assembly of specific signaling complexes. We propose that specific Gbetagamma subunits have a broader role in controlling the architecture, assembly, and activity of cellular signaling pathways.
Collapse
Affiliation(s)
- Denis J Dupré
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada.
| | | | | | | |
Collapse
|
20
|
Intracellular trafficking and assembly of specific Kir3 channel/G protein complexes. Cell Signal 2009; 21:488-501. [DOI: 10.1016/j.cellsig.2008.11.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Revised: 11/13/2008] [Accepted: 11/15/2008] [Indexed: 12/27/2022]
|
21
|
RNAi methodologies for the functional study of signaling molecules. PLoS One 2009; 4:e4559. [PMID: 19238203 PMCID: PMC2641016 DOI: 10.1371/journal.pone.0004559] [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: 01/02/2009] [Accepted: 01/13/2009] [Indexed: 12/25/2022] Open
Abstract
RNA interference (RNAi) was investigated with the aim of achieving gene silencing with diverse RNAi platforms that include small interfering RNA (siRNA), short hairpin RNA (shRNA) and antisense oligonucleotides (ASO). Different versions of each system were used to silence the expression of specific subunits of the heterotrimeric signal transducing G-proteins, G alpha i2 and G beta 2, in the RAW 264.7 murine macrophage cell line. The specificity of the different RNA interference (RNAi) platforms was assessed by DNA microarray analysis. Reliable RNAi methodologies against the genes of interest were then developed and applied to functional studies of signaling networks. This study demonstrates a successful knockdown of target genes and shows the potential of RNAi for use in functional studies of signaling molecules.
Collapse
|
22
|
Cho H, Kehrl JH. Chapter 9 Regulation of Immune Function by G Protein‐Coupled Receptors, Trimeric G Proteins, and RGS Proteins. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 86:249-98. [DOI: 10.1016/s1877-1173(09)86009-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
23
|
Kitanaka N, Kitanaka J, Hall FS, Tatsuta T, Morita Y, Takemura M, Wang XB, Uhl GR. Alterations in the levels of heterotrimeric G protein subunits induced by psychostimulants, opiates, barbiturates, and ethanol: Implications for drug dependence, tolerance, and withdrawal. Synapse 2008; 62:689-99. [PMID: 18566973 DOI: 10.1002/syn.20543] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Neuronal adaptations have been found to occur in multiple brain regions after chronic intake of abused drugs, and are therefore thought to underlie drug dependence, tolerance, and withdrawal. Pathophysiological changes in drug responsiveness as well as behavioral sequelae of chronic drug exposure are thought to depend largely upon the altered state of heterotrimeric GTP binding protein (G protein)-coupled receptor (GPCR)-G protein interactions. Responsiveness of GPCR-related intracellular signaling systems to drugs of abuse is heterogeneous, depending on the types of intracellular effectors to which the specific Galpha protein subtypes are coupled and GPCR-G protein coupling efficiency, factors influenced by the class of drug, expression levels of G protein subunits, and drug treatment regimens. To enhance understanding of the molecular mechanisms that underlie the development of pathophysiological states resulting from chronic intake of abused drugs, this review focuses on alterations in the expression levels of G protein subunits induced by various drugs of abuse. Changes in these mechanisms appear to be specific to particular drugs of abuse, and specific conditions of drug treatment.
Collapse
Affiliation(s)
- Nobue Kitanaka
- Department of Pharmacology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Smrcka AV, Lehmann DM, Dessal AL. G protein betagamma subunits as targets for small molecule therapeutic development. Comb Chem High Throughput Screen 2008; 11:382-95. [PMID: 18537559 PMCID: PMC2688719 DOI: 10.2174/138620708784534761] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
G proteins mediate the action of G protein coupled receptors (GPCRs), a major target of current pharmaceuticals and a major target of interest in future drug development. Most pharmaceutical interest has been in the development of selective GPCR agonists and antagonists that activate or inhibit specific GPCRs. Some recent thinking has focused on the idea that some pathologies are the result of the actions of an array of GPCRs suggesting that targeting single receptors may have limited efficacy. Thus, targeting pathways common to multiple GPCRs that control critical pathways involved in disease has potential therapeutic relevance. G protein betagamma subunits released from some GPCRs upon receptor activation regulate a variety of downstream pathways to control various aspects of mammalian physiology. There is evidence from cell- based and animal models that excess Gbetagamma signaling can be detrimental and blocking Gbetagamma signaling has salutary effects in a number of pathological models. Gbetagamma regulates downstream pathways through modulation of enzymes that produce cellular second messengers or through regulation of ion channels by direct protein-protein interactions. Thus, blocking Gbetagamma functions requires development of small molecule agents that disrupt Gbetagamma protein interactions with downstream partners. Here we discuss evidence that small molecule targeting Gbetagamma could be of therapeutic value. The concept of disruption of protein-protein interactions by targeting a "hot spot" on Gbetagamma is delineated and the biochemical and virtual screening strategies for identification of small molecules that selectively target Gbetagamma functions are outlined. Evaluation of the effectiveness of virtual screening indicates that computational screening enhanced identification of true Gbetagamma binding molecules. However, further refinement of the approach could significantly improve the yield of Gbetagamma binding molecules from this screen that could result in multiple candidate leads for future drug development.
Collapse
Affiliation(s)
- Alan V Smrcka
- Department of Pharmacology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
| | | | | |
Collapse
|
25
|
Zaballos MA, Garcia B, Santisteban P. Gbetagamma dimers released in response to thyrotropin activate phosphoinositide 3-kinase and regulate gene expression in thyroid cells. Mol Endocrinol 2008; 22:1183-99. [PMID: 18202153 DOI: 10.1210/me.2007-0093] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Signaling by TSH through its receptor leads to the dissociation of trimeric G proteins into Galpha and Gbetagamma. Galphas activates adenylyl cyclase, which increases cAMP levels that induce several effects in the thyroid cell, including transcription of the sodium-iodide symporter (NIS) gene through a mechanism involving Pax8 binding to the NIS promoter. Much less is known about the function of Gbetagamma in thyroid differentiation, and therefore we studied their role in TSH signaling. Gbetagamma overexpression inhibits NIS promoter activation and reduces NIS protein accumulation in response to TSH and forskolin. Conversely, inhibition of Gbetagamma-dependent pathways increases NIS promoter activity elicited by TSH but does not modify forskolin-induced activation. Gbetagamma dimers are being released from the Gs subfamily of proteins, because cholera toxin mimics the effects elicited by TSH, whereas pertussis toxin has no effect on NIS promoter activity. We also found that TSH stimulates Akt phosphorylation in a phosphoinositide 3-kinase (PI3K)-dependent and cAMP-independent manner. This is mediated by Gbetagamma, because its overexpression or specific sequestration, respectively, increased or reduced phosphorylated Akt levels upon TSH stimulation. Gbetagamma sequestration increases NIS protein levels induced by TSH and Pax8 binding to the NIS promoter, which is also increased by PI3K inhibition. This is, at least in part, caused by Gbetagamma-mediated Pax8 exclusion from the nucleus that is attenuated when PI3K activity is blocked. These data unequivocally demonstrate that Gbetagamma released by TSH action stimulate PI3K, inhibiting NIS gene expression in a cAMP-independent manner due to a decrease in Pax8 binding to the NIS promoter.
Collapse
Affiliation(s)
- Miguel A Zaballos
- Instituto de Investigaciones Biomedicas Alberto Sols, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, 28029 Madrid, Spain
| | | | | |
Collapse
|
26
|
Yi KS, Lee S, Kang YH, Bae YS, Hwang SY, Ha I, Kim H, Kim MS, Cho B, Kang HJ, Bang KT, Kim JY, Yang J, Chung J, Ahn C. Weak response of porcine C5a receptor towards human C5a in miniature pig endothelial cells and PMNs. Xenotransplantation 2007; 14:563-71. [DOI: 10.1111/j.1399-3089.2007.00421.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
27
|
Monk PN, Scola AM, Madala P, Fairlie DP. Function, structure and therapeutic potential of complement C5a receptors. Br J Pharmacol 2007; 152:429-48. [PMID: 17603557 PMCID: PMC2050825 DOI: 10.1038/sj.bjp.0707332] [Citation(s) in RCA: 296] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Complement fragment (C)5a is a 74 residue pro-inflammatory polypeptide produced during activation of the complement cascade of serum proteins in response to foreign surfaces such as microorganisms and tissue damaged by physical or chemical injury. C5a binds to at least two seven-transmembrane domain receptors, C5aR (C5R1, CD88) and C5L2 (gpr77), expressed ubiquitously on a wide variety of cells but particularly on the surface of immune cells like macrophages, neutrophils and T cells. C5aR is a classical G protein-coupled receptor that signals through G alpha i and G alpha 16, whereas C5L2 does not appear to couple to G proteins and has no known signalling activity. Although C5a was first described as an anaphylatoxin and later as a leukocyte chemoattractant, the widespread expression of C5aR suggested more general functionality. Our understanding of the physiology of C5a has improved significantly in recent years through exploitation of receptor knockout and knocking mice, C5 and C5a antibodies, soluble recombinant C5a and C5a analogues and newly developed receptor antagonists. C5a is now also implicated in non-immunological functions associated with developmental biology, CNS development and neurodegeneration, tissue regeneration, and haematopoiesis. Combined receptor mutagenesis, molecular modelling, structure-activity relationship studies and species dependence for ligand potency on C5aR have been helpful for identifying ligand binding sites on the receptor and for defining mechanisms of receptor activation and inactivation. This review will highlight major developments in C5a receptor research that support C5aR as an important therapeutic target. The intriguing possibilities raised by the existence of a non-signalling C5a receptor are also discussed.
Collapse
Affiliation(s)
- P N Monk
- Academic Neurology Unit, School of Medicine and Biomedical Science, University of Sheffield, Sheffield, UK.
| | | | | | | |
Collapse
|
28
|
Cho MK, Kim WD, Ki SH, Hwang JI, Choi S, Lee CH, Kim SG. Role of Galpha12 and Galpha13 as novel switches for the activity of Nrf2, a key antioxidative transcription factor. Mol Cell Biol 2007; 27:6195-208. [PMID: 17591699 PMCID: PMC1952151 DOI: 10.1128/mcb.02065-06] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Galpha12 and Galpha13 function as molecular regulators responding to extracellular stimuli. NF-E2-related factor 2 (Nrf2) is involved in a protective adaptive response to oxidative stress. This study investigated the regulation of Nrf2 by Galpha12 and Galpha13. A deficiency of Galpha12, but not of Galpha13, enhanced Nrf2 activity and target gene transactivation in embryo fibroblasts. In mice, Galpha12 knockout activated Nrf2 and thereby facilitated heme catabolism to bilirubin and its glucuronosyl conjugations. An oligonucleotide microarray demonstrated the transactivation of Nrf2 target genes by Galpha12 gene knockout. Galpha12 deficiency reduced Jun N-terminal protein kinase (JNK)-dependent Nrf2 ubiquitination required for proteasomal degradation, and so did Galpha13 deficiency. The absence of Galpha12, but not of Galpha13, increased protein kinase C delta (PKC delta) activation and the PKC delta-mediated serine phosphorylation of Nrf2. Galpha13 gene knockout or knockdown abrogated the Nrf2 phosphorylation induced by Galpha12 deficiency, suggesting that relief from Galpha12 repression leads to the Galpha13-mediated activation of Nrf2. Constitutive activation of Galpha13 promoted Nrf2 activity and target gene induction via Rho-mediated PKC delta activation, corroborating positive regulation by Galpha13. In summary, Galpha12 and Galpha13 transmit a JNK-dependent signal for Nrf2 ubiquitination, whereas Galpha13 regulates Rho-PKC delta-mediated Nrf2 phosphorylation, which is negatively balanced by Galpha12.
Collapse
Affiliation(s)
- Min Kyung Cho
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Sillim-dong, Gwanak-gu, Seoul, South Korea
| | | | | | | | | | | | | |
Collapse
|
29
|
Hippe HJ, Luedde M, Lutz S, Koehler H, Eschenhagen T, Frey N, Katus HA, Wieland T, Niroomand F. Regulation of cardiac cAMP synthesis and contractility by nucleoside diphosphate kinase B/G protein beta gamma dimer complexes. Circ Res 2007; 100:1191-9. [PMID: 17363702 DOI: 10.1161/01.res.0000264058.28808.cc] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Heterotrimeric G proteins are pivotal regulators of myocardial contractility. In addition to the receptor-induced GDP/GTP exchange, G protein alpha subunits can be activated by a phosphate transfer via a plasma membrane-associated complex of nucleoside diphosphate kinase B (NDPK B) and G protein betagamma-dimers (Gbetagamma). To investigate the physiological role of this phosphate transfer in cardiomyocytes, we generated a Gbeta1gamma2-dimer carrying a single amino acid exchange at the intermediately phosphorylated His-266 in the beta1 subunit (Gbeta1H266Lgamma2). Recombinantly expressed Gbeta1H266Lgamma2 were integrated into heterotrimeric G proteins in rat cardiomyocytes but were deficient in intermediate Gbeta phosphorylation. Compared with wild-type Gbeta1gamma2 (Gbeta1WTgamma2), overexpression of Gbeta1H266Lgamma2 suppressed basal cAMP formation up to 55%. A similar decrease in basal cAMP production occurred when the formation of NDPK B/Gbetagamma complexes was attenuated by siRNA-mediated NDPK B knockdown. In adult rat cardiomyocytes expressing Gbeta1H266Lgamma2, the basal contractility was suppressed by approximately 50% which correlated to similarly reduced basal cAMP levels and reduced Ser16-phosphorylation of phospholamban. In the presence of the beta-adrenoceptor agonist isoproterenol, the total cAMP formation and contractility were significantly lower in Gbeta1H266Lgamma2 than in Gbeta1WTgamma2 expressing cardiomyocytes. However, the relative isoproterenol-induced increased was not affected by Gbeta1H266Lgamma2. We conclude that the receptor-independent activation of G proteins via NDPK B/Gbetagamma complexes requires the intermediate phosphorylation of G protein beta subunits at His-266. Our results highlight the histidine kinase activity of NDPK B for Gbeta and demonstrate its contribution to the receptor-independent regulation of cAMP synthesis and contractility in intact cardiomyocytes.
Collapse
Affiliation(s)
- Hans-Joerg Hippe
- Innere Medizin III-Kardiologie, Universität Heidelberg, Heidelberg, Germany.
| | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Wieland T. Interaction of nucleoside diphosphate kinase B with heterotrimeric G protein betagamma dimers: consequences on G protein activation and stability. Naunyn Schmiedebergs Arch Pharmacol 2007; 374:373-83. [PMID: 17200862 DOI: 10.1007/s00210-006-0126-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2006] [Accepted: 11/20/2006] [Indexed: 12/31/2022]
Abstract
It is generally accepted that G protein coupled receptors (GPCR) activate heterotrimeric G proteins by inducing a GDP/GTP exchange at the G protein alpha subunit. In addition, the transfer of high energetic phosphate by nucleoside diphosphate kinase (NDPK) and/or the beta subunit of G proteins (Gbeta) can induce G protein activation. Recent evidence suggests that the NDPK isoform B (NDPK B) forms a complex with Gbetagamma dimers. In this complex, NDPK B acts as a protein histidine kinase phosphorylating Gbeta at histidine residue 266 (His266). The high energetic phosphoamidate bond on His266 allows for a phosphate transfer specifically onto GDP and thus local formation of GTP, which binds to and thereby activates the respective G protein alpha subunit. Apparently, this process occurs independent of the classical GPCR-induced GDP/GTP exchange at least for members of the G(s) and G(i) subfamilies of heterotrimeric G proteins. By using a mutant of Gbeta(1) in which His266 was replaced by Leu, it was recently demonstrated that NDPK B/Gbetagamma-mediated G(s) activation contributes by about 50% to basal cAMP formation and contractility in rat cardiac myocytes. Besides its apparent role in G protein activation, the complex formation of NDPK B with Gbetagamma dimers might be essential for G protein stability. Depletion of either the NDPK B orthologue or Gbeta(1) isoforms in zebrafish embryos led to a similar phenotype displaying contractile dysfunction in the heart accompanied by a complete loss of heterotrimeric G protein expression. In conclusion, the interaction of NDKP B with Gbetagamma dimers might play an important role in signal transduction, and alterations in this novel pathway might be of pathophysiological importance.
Collapse
Affiliation(s)
- Thomas Wieland
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät Mannheim, Universität Heidelberg, Maybachstrasse 14, D-68169 Mannheim, Germany.
| |
Collapse
|
31
|
Ramos MC, Tenorio R, Martínez-García A, Sastre I, Vilella-Cuadrada E, Frank A, Rosich-Estragó M, Valdivieso F, Bullido MJ. Association of DSC1, a gene modulated by adrenergic stimulation, with Alzheimer's disease. Neurosci Lett 2006; 408:203-8. [PMID: 17014956 DOI: 10.1016/j.neulet.2006.09.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2006] [Revised: 07/26/2006] [Accepted: 09/01/2006] [Indexed: 11/25/2022]
Abstract
Alzheimer's disease (AD) is a complex multifactorial disorder involving a number of genetic and environmental factors, with severe head injury consistently reported as a major non-genetic risk factor. The adrenergic activation that occurs during major trauma increases cAMP levels, therefore the cAMP signaling pathway might be involved in AD pathogenesis. Time course of candidate gene expression following adrenergic stimulation with isoproterenol was assayed in neuroblastoma cells by quantitative reverse transcription (RT)-PCR. Then, genetic association studies of polymorphisms in several of these candidate genes were performed. Association studies in two independent case-control samples showed a polymorphism in DSC1, encoding desmocollin 1--a member of the desmosomal cadherins--which modulated AD susceptibility in a gender-specific manner. These results are in accordance with the potential involvement of the adrenergic signaling pathway in AD pathogenesis.
Collapse
Affiliation(s)
- María C Ramos
- Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (C.S.I.C.-U.A.M.), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Kehrl JH. Chemoattractant receptor signaling and the control of lymphocyte migration. Immunol Res 2006; 34:211-27. [PMID: 16891672 DOI: 10.1385/ir:34:3:211] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 02/08/2023]
Abstract
This review focuses on mechanisms by which chemoattractant receptors activate downstream signaling pathways in lymphocytes. An emphasis is placed on heterotrimeric G protein signaling with a discussion of the specific heterotrimeric G-proteins involved in lymphocyte chemotaxis and motility and the role of regulator of G protein signaling (RGS) proteins in controlling the activation of downstream effectors. Also considered are those direct downstream effectors known to function in lymphocyte chemotaxis and/or motility. The consequences of targeting genes suspected, known, or serendipitously found to be involved in chemokine receptor signaling pathways form much of a basis for the review. When needed for clarification, reference to studies of chemoattractant signaling in model organisms and in neutrophils will be compared and contrasted to studies in lymphocytes. Finally, the emergence of tools to image lymphocyte in vitro and in vivo will be mentioned as they are increasing helpful for the analysis of lymphocyte trafficking and amendable to the study of chemokine receptor signaling.
Collapse
Affiliation(s)
- John H Kehrl
- B Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
| |
Collapse
|
33
|
Shin KJ, Wall EA, Zavzavadjian JR, Santat LA, Liu J, Hwang JI, Rebres R, Roach T, Seaman W, Simon MI, Fraser IDC. A single lentiviral vector platform for microRNA-based conditional RNA interference and coordinated transgene expression. Proc Natl Acad Sci U S A 2006; 103:13759-64. [PMID: 16945906 PMCID: PMC1557799 DOI: 10.1073/pnas.0606179103] [Citation(s) in RCA: 254] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
RNAi is proving to be a powerful experimental tool for the functional annotation of mammalian genomes. The full potential of this technology will be realized through development of approaches permitting regulated manipulation of endogenous gene expression with coordinated reexpression of exogenous transgenes. We describe the development of a lentiviral vector platform, pSLIK (single lentivector for inducible knockdown), which permits tetracycline-regulated expression of microRNA-like short hairpin RNAs from a single viral infection of any naïve cell system. In mouse embryonic fibroblasts, the pSLIK platform was used to conditionally deplete the expression of the heterotrimeric G proteins Galpha12 and Galpha13 both singly and in combination, demonstrating the Galpha13 dependence of serum response element-mediated transcription. In RAW264.7 macrophages, regulated knockdown of Gbeta2 correlated with a reduced Ca(2+) response to C5a. Insertion of a GFP transgene upstream of the Gbeta2 microRNA-like short hairpin RNA allowed concomitant reexpression of a heterologous mRNA during tetracycline-dependent target gene knockdown, significantly enhancing the experimental applicability of the pSLIK system.
Collapse
Affiliation(s)
- Kum-Joo Shin
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Estelle A. Wall
- Alliance for Cell Signaling Molecular Biology Laboratory and
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Joelle R. Zavzavadjian
- Alliance for Cell Signaling Molecular Biology Laboratory and
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Leah A. Santat
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Jamie Liu
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Jong-Ik Hwang
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Robert Rebres
- Alliance for Cell Signaling Macrophage Biology Laboratory, Department of Veterans Affairs Medical Center, University of California, 4150 Clement Street, San Francisco, CA 94121
| | - Tamara Roach
- Alliance for Cell Signaling Macrophage Biology Laboratory, Department of Veterans Affairs Medical Center, University of California, 4150 Clement Street, San Francisco, CA 94121
| | - William Seaman
- Alliance for Cell Signaling Macrophage Biology Laboratory, Department of Veterans Affairs Medical Center, University of California, 4150 Clement Street, San Francisco, CA 94121
| | - Melvin I. Simon
- Alliance for Cell Signaling Molecular Biology Laboratory and
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| | - Iain D. C. Fraser
- Alliance for Cell Signaling Molecular Biology Laboratory and
- *Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125; and
| |
Collapse
|
34
|
Gotthardt D, Blancheteau V, Bosserhoff A, Ruppert T, Delorenzi M, Soldati T. Proteomics fingerprinting of phagosome maturation and evidence for the role of a Galpha during uptake. Mol Cell Proteomics 2006; 5:2228-43. [PMID: 16926386 DOI: 10.1074/mcp.m600113-mcp200] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Phagocytosis, whether of food particles in protozoa or bacteria and cell remnants in the metazoan immune system, is a conserved process. The particles are taken up into phagosomes, which then undergo complex remodeling of their components, called maturation. By using two-dimensional gel electrophoresis and mass spectrometry combined with genomic data, we identified 179 phagosomal proteins in the amoeba Dictyostelium, including components of signal transduction, membrane traffic, and the cytoskeleton. By carrying out this proteomics analysis over the course of maturation, we obtained time profiles for 1,388 spots and thus generated a dynamic record of phagosomal protein composition. Clustering of the time profiles revealed five clusters and 24 functional groups that were mapped onto a flow chart of maturation. Two heterotrimeric G protein subunits, Galpha4 and Gbeta, appeared at the earliest times. We showed that mutations in the genes encoding these two proteins produce a phagocytic uptake defect in Dictyostelium. This analysis of phagosome protein dynamics provides a reference point for future genetic and functional investigations.
Collapse
Affiliation(s)
- Daniel Gotthardt
- Department of Molecular Cell Research, Max Planck Institute for Medical Research, University Hospital of Heidelberg, Germany
| | | | | | | | | | | |
Collapse
|
35
|
Borodinsky LN, Spitzer NC. Second messenger pas de deux: the coordinated dance between calcium and cAMP. Sci Signal 2006; 2006:pe22. [PMID: 16720840 DOI: 10.1126/stke.3362006pe22] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Dynamic calcium signaling is a well-established precept in biology. Different cell types exhibit spontaneous as well as stimulus-triggered transient changes in the concentration of intracellular calcium. Does this behavior extend to other second messengers? Optical dissection of various signal transduction pathways with fluorescent reporter molecules that enable visualization of changes in concentration of other second messengers is well under way. Recent research using technologically refined probes provides improved temporal and spatial resolution of adenosine 3',5'-monophosphate (cAMP) dynamics to generate insights into the bidirectional interplay between intracellular fluctuations of cAMP and calcium. cAMP oscillations are generated in response to hormones, and cells can recognize and differentially respond to transient versus sustained changes in this second messenger. Second messenger reporters are now available to track multiple players and so provide a dynamic picture of signaling networks.
Collapse
Affiliation(s)
- Laura N Borodinsky
- Neurobiology Section, Kavli Institute for Brain and Mind, University of California, San Diego, La Jolla, CA 92093, USA.
| | | |
Collapse
|
36
|
Krumins AM, Gilman AG. Targeted knockdown of G protein subunits selectively prevents receptor-mediated modulation of effectors and reveals complex changes in non-targeted signaling proteins. J Biol Chem 2006; 281:10250-62. [PMID: 16446365 DOI: 10.1074/jbc.m511551200] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Heterotrimeric G protein signaling specificity has been attributed to select combinations of Galpha, beta, and gamma subunits, their interactions with other signaling proteins, and their localization in the cell. With few exceptions, the G protein subunit combinations that exist in vivo and the significance of these specific combinations are largely unknown. We have begun to approach these problems in HeLa cells by: 1) determining the concentrations of Galpha and Gbeta subunits; 2) examining receptor-dependent activities of two effector systems (adenylyl cyclase and phospholipase Cbeta); and 3) systematically silencing each of the Galpha and Gbeta subunits by using small interfering RNA while quantifying resultant changes in effector function and the concentrations of other relevant proteins in the network. HeLa cells express equimolar amounts of total Galpha and Gbeta subunits. The most prevalent Galpha proteins were one member of each Galpha subfamily (Galpha(s), Galpha(i3), Galpha(11), and Galpha(13)). We substantially abrogated expression of most of the Galpha and Gbeta proteins expressed in these cells, singly and some in combinations. As expected, agonist-dependent activation of adenylyl cyclase or phospholipase Cbeta was specifically eliminated following the silencing of Galpha(s) or Galpha(q/11), respectively. We also confirmed that Gbeta subunits are necessary for stable accumulation of Galpha proteins in vivo. Gbeta subunits demonstrated little isoform specificity for receptor-dependent modulation of effector activity. We observed compensatory changes in G protein accumulation following silencing of individual genes, as well as an apparent reciprocal relationship between the expression of certain Galpha(q) and Galpha(i) subfamily members. These findings provide a foundation for understanding the mechanisms that regulate the adaptability and remarkable resilience of G protein signaling networks.
Collapse
Affiliation(s)
- Andrejs M Krumins
- Department of Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | | |
Collapse
|
37
|
Cahill AL, Herring BE, Fox AP. Stable silencing of SNAP-25 in PC12 cells by RNA interference. BMC Neurosci 2006; 7:9. [PMID: 16445859 PMCID: PMC1373637 DOI: 10.1186/1471-2202-7-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2005] [Accepted: 01/30/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND SNAP-25 is a synaptic protein known to be involved in exocytosis of synaptic vesicles in neurons and of large dense-core vesicles in neuroendocrine cells. Its role in exocytosis has been studied in SNAP-25 knockout mice, in lysed synaptosomes lacking functional SNAP-25 and in cells after treatment with botulinum toxins A or E that specifically cleave SNAP-25. These studies have shown that SNAP-25 appears to be required for most but not all evoked secretion. In order to further study the role of SNAP-25 in catecholamine secretion from PC12 cells we have used the recently developed technique of RNA interference to generate PC12 cell lines with virtually undetectable levels of SNAP-25. RNA interference is the sequence-specific silencing or knockdown of gene expression triggered by the introduction of double-stranded RNA into a cell. RNA interference can be elicited in mammalian cells in a number of ways, one of which is by the expression of small hairpin RNAs from a transfected plasmid. Selection of stably transfected cell lines expressing a small hairpin RNA allows one-time characterization of the degree and specificity of gene silencing and affords a continuing source of well-characterized knockdown cells for experimentation. RESULTS A PC12 cell line stably transfected with a plasmid expressing an shRNA targeting SNAP-25 has been established. This SNAP-25 knockdown cell line has barely detectable levels of SNAP-25, but normal levels of other synaptic proteins. Catecholamine secretion elicited by depolarization of the SNAP-25 knockdown cells was reduced to 37% of control. CONCLUSION Knockdown of SNAP-25 in PC12 cells reduces but does not eliminate evoked secretion of catecholamines. Transient expression of human SNAP-25 in the knockdown cells rescues the deficit in catecholamine secretion.
Collapse
Affiliation(s)
- Anne L Cahill
- Department of Neurobiology, Pharmacology & Physiology, The University of Chicago, Chicago, IL, USA
| | - Bruce E Herring
- Department of Neurobiology, Pharmacology & Physiology, The University of Chicago, Chicago, IL, USA
| | - Aaron P Fox
- Department of Neurobiology, Pharmacology & Physiology, The University of Chicago, Chicago, IL, USA
| |
Collapse
|
38
|
Hashimoto M, Ito T, Fukumitsu H, Nomoto H, Furukawa Y, Furukawa S. Stimulation of production of glial cell line-derived neurotrophic factor and nitric oxide by lipopolysaccharide with different dose-responsiveness in cultured rat macrophages. Biomed Res 2005; 26:223-9. [PMID: 16295699 DOI: 10.2220/biomedres.26.223] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
To understand the molecular basis of inflammation-induced neurotrophic influences, we investigated the effects of lipopolysaccharide (LPS) on production of glial cell line-derived neurotrophic factor (GDNF) in the injured rat spinal cord or in cultured rat macrophages in comparison with the effects on synthesis/secretion of inducible nitric oxide synthase (iNOS) and nitric oxide (NO). We found that GDNF mRNA expression lasted longer than that of iNOS mRNA in the injured spinal cord after injection of the high-dose LPS that had improved locomotor function, suggesting that the GDNF expression and its balance with NO generation were critical for injury regeneration. Therefore, we next investigated the effects of LPS on cultured macrophages. Levels of iNOS mRNA and secreted NO were enhanced by LPS at lower concentrations (10 ng/mL and above), whereas mRNA expression and secretion of GDNF were elevated only at higher concentrations (100 ng/mL and above). The culture medium of macrophages treated with 10 ng/mL of LPS was actually neurotoxic against cultured cortical neurons, whereas that conditioned at 1000 ng/mL was not. These observations suggest that neurotoxicity partly based on NO is induced by a lower degree of inflammation, whereas neurotrophic effects based on GDNF are manifested at a higher degree of inflammatory activity.
Collapse
Affiliation(s)
- Manabu Hashimoto
- Laboratory of Molecular Biology, Gifu Pharmaceutical University, 5-6-1, Mitahora-higashi, Gifu 502-8585, Japan
| | | | | | | | | | | |
Collapse
|