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Hille B, Dickson EJ, Kruse M, Vivas O, Suh BC. Phosphoinositides regulate ion channels. BIOCHIMICA ET BIOPHYSICA ACTA 2015; 1851:844-56. [PMID: 25241941 PMCID: PMC4364932 DOI: 10.1016/j.bbalip.2014.09.010] [Citation(s) in RCA: 462] [Impact Index Per Article: 51.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 09/09/2014] [Accepted: 09/10/2014] [Indexed: 11/29/2022]
Abstract
Phosphoinositides serve as signature motifs for different cellular membranes and often are required for the function of membrane proteins. Here, we summarize clear evidence supporting the concept that many ion channels are regulated by membrane phosphoinositides. We describe tools used to test their dependence on phosphoinositides, especially phosphatidylinositol 4,5-bisphosphate, and consider mechanisms and biological meanings of phosphoinositide regulation of ion channels. This lipid regulation can underlie changes of channel activity and electrical excitability in response to receptors. Since different intracellular membranes have different lipid compositions, the activity of ion channels still in transit towards their final destination membrane may be suppressed until they reach an optimal lipid environment. This article is part of a Special Issue entitled Phosphoinositides.
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Affiliation(s)
- Bertil Hille
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195-7290, USA.
| | - Eamonn J Dickson
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195-7290, USA.
| | - Martin Kruse
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195-7290, USA.
| | - Oscar Vivas
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195-7290, USA.
| | - Byung-Chang Suh
- Department of Brain Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873, Republic of Korea.
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52
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Fung S, Cherry AE, Xu C, Stella N. Alkylindole-sensitive receptors modulate microglial cell migration and proliferation. Glia 2015; 63:1797-808. [PMID: 25914169 DOI: 10.1002/glia.22845] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 03/06/2015] [Accepted: 04/07/2015] [Indexed: 02/01/2023]
Abstract
Ligands targeting G protein-coupled receptors (GPCR) expressed by microglia have been shown to regulate distinct components of their activation process, including cell proliferation, migration and differentiation into M1 or M2 phenotypes. Cannabinoids, including the active component of the Cannabis plant, tetrahydrocannabinol (THC), and the synthetic alkylindole (AI) compound, WIN55212-2 (WIN-2), activate two molecularly identified GPCRs: CB1 and CB2 . Previous studies reported that WIN-2 activates an additional unknown GPCR that is not activated by plant-derived cannabinoids, and evidence indicates that microglia express these receptors. Detailed studies on the role of AI-sensitive receptors in microglial cell activation were difficult as no selective pharmacological tools were available. Here, three newly-developed AI analogues allowed us to determine if microglia express AI-sensitive receptors and if so, study how they regulate the microglial cell activation process. We found that mouse microglia in primary culture express functional AI-sensitive receptors as measured by radioligand binding and changes in intracellular cAMP levels, and that these receptors control both basal and ATP-stimulated migration. AI analogues inhibit cell proliferation stimulated by macrophage-colony stimulating factor (M-CSF) without affecting basal cell proliferation. Remarkably, AI analogues do not control the expression of effector proteins characteristic of M1 or M2 phenotypes; yet activating microglia with M1 and M2 cytokines reduces the microglial response to AI analogues. Our results suggest that microglia express functional AI-sensitive receptors that control select components of their activation process. Agonists of these novel targets might represent a novel class of therapeutics to influence the microglial cell activation process.
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Affiliation(s)
- Susan Fung
- Department of Pharmacology, University of Washington, 1959 NE Pacific Way, Seattle, Washington.,Graduate Program in Neurobiology and Behavior, University of Washington, 1959 NE Pacific St., Seattle, Washington
| | - Allison E Cherry
- Department of Pharmacology, University of Washington, 1959 NE Pacific Way, Seattle, Washington
| | - Cong Xu
- Department of Pharmacology, University of Washington, 1959 NE Pacific Way, Seattle, Washington
| | - Nephi Stella
- Department of Pharmacology, University of Washington, 1959 NE Pacific Way, Seattle, Washington.,Graduate Program in Neurobiology and Behavior, University of Washington, 1959 NE Pacific St., Seattle, Washington.,Department of Psychiatry and Behavioral Sciences, University of Washington, 1959 NE Pacific Way, Seattle, Washington
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53
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Wilson FH, Johannessen CM, Piccioni F, Tamayo P, Kim JW, Van Allen EM, Corsello SM, Capelletti M, Calles A, Butaney M, Sharifnia T, Gabriel SB, Mesirov JP, Hahn WC, Engelman JA, Meyerson M, Root DE, Jänne PA, Garraway LA. A functional landscape of resistance to ALK inhibition in lung cancer. Cancer Cell 2015; 27:397-408. [PMID: 25759024 PMCID: PMC4398996 DOI: 10.1016/j.ccell.2015.02.005] [Citation(s) in RCA: 132] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 12/15/2014] [Accepted: 02/10/2015] [Indexed: 01/17/2023]
Abstract
We conducted a large-scale functional genetic study to characterize mechanisms of resistance to ALK inhibition in ALK-dependent lung cancer cells. We identify members of known resistance pathways and additional putative resistance drivers. Among the latter were members of the P2Y purinergic receptor family of G-protein-coupled receptors (P2Y1, P2Y2, and P2Y6). P2Y receptors mediated resistance in part through a protein-kinase-C (PKC)-dependent mechanism. Moreover, PKC activation alone was sufficient to confer resistance to ALK inhibitors, whereas combined ALK and PKC inhibition restored sensitivity. We observed enrichment of gene signatures associated with several resistance drivers (including P2Y receptors) in crizotinib-resistant ALK-rearranged lung tumors compared to treatment-naive controls, supporting a role for these identified mechanisms in clinical ALK inhibitor resistance.
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Affiliation(s)
- Frederick H Wilson
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA; The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | | | | | - Pablo Tamayo
- The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Jong Wook Kim
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA; The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Eliezer M Van Allen
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA; The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Steven M Corsello
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA; The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Marzia Capelletti
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Antonio Calles
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Mohit Butaney
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Tanaz Sharifnia
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA; The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Stacey B Gabriel
- The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Jill P Mesirov
- The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - William C Hahn
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA; The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Jeffrey A Engelman
- Massachusetts General Hospital Cancer Center, Charlestown, MA 02129, USA
| | - Matthew Meyerson
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA; The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA; Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - David E Root
- The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Pasi A Jänne
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA; Belfer Institute for Applied Cancer Science, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Levi A Garraway
- Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA; The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA.
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54
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Pelletán LE, Suhaiman L, Vaquer CC, Bustos MA, De Blas GA, Vitale N, Mayorga LS, Belmonte SA. ADP ribosylation factor 6 (ARF6) promotes acrosomal exocytosis by modulating lipid turnover and Rab3A activation. J Biol Chem 2015; 290:9823-41. [PMID: 25713146 DOI: 10.1074/jbc.m114.629006] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Indexed: 11/06/2022] Open
Abstract
Regulated secretion is a central issue for the specific function of many cells; for instance, mammalian sperm acrosomal exocytosis is essential for egg fertilization. ARF6 (ADP-ribosylation factor 6) is a small GTPase implicated in exocytosis, but its downstream effectors remain elusive in this process. We combined biochemical, functional, and microscopy-based methods to show that ARF6 is present in human sperm, localizes to the acrosomal region, and is required for calcium and diacylglycerol-induced exocytosis. Results from pulldown assays show that ARF6 exchanges GDP for GTP in sperm challenged with different exocytic stimuli. Myristoylated and guanosine 5'-3-O-(thio)triphosphate (GTPγS)-loaded ARF6 (active form) added to permeabilized sperm induces acrosome exocytosis even in the absence of extracellular calcium. We explore the ARF6 signaling cascade that promotes secretion. We demonstrate that ARF6 stimulates a sperm phospholipase D activity to produce phosphatidic acid and boosts the synthesis of phosphatidylinositol 4,5-bisphosphate. We present direct evidence showing that active ARF6 increases phospholipase C activity, causing phosphatidylinositol 4,5-bisphosphate hydrolysis and inositol 1,4,5-trisphosphate-dependent intra-acrosomal calcium release. We show that active ARF6 increases the exchange of GDP for GTP on Rab3A, a prerequisite for secretion. We propose that exocytic stimuli activate ARF6, which is required for acrosomal calcium efflux and the assembly of the membrane fusion machinery. This report highlights the physiological importance of ARF6 as a key factor for human sperm exocytosis and fertilization.
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Affiliation(s)
- Leonardo E Pelletán
- From the Instituto de Histología y Embriología, CONICET, Facultad de Ciencias Médicas, CC56, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina and
| | - Laila Suhaiman
- From the Instituto de Histología y Embriología, CONICET, Facultad de Ciencias Médicas, CC56, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina and
| | - Cintia C Vaquer
- From the Instituto de Histología y Embriología, CONICET, Facultad de Ciencias Médicas, CC56, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina and
| | - Matías A Bustos
- From the Instituto de Histología y Embriología, CONICET, Facultad de Ciencias Médicas, CC56, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina and
| | - Gerardo A De Blas
- From the Instituto de Histología y Embriología, CONICET, Facultad de Ciencias Médicas, CC56, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina and
| | - Nicolas Vitale
- the Département Neurotransmission et Sécrétion Neuroendocrine, Institut des Neurosciences Cellulaires et Intégratives (UPR 3212), CNRS et Université de Strasbourg, 5 Rue Blaise Pascal, 67084 Strasbourg, France
| | - Luis S Mayorga
- From the Instituto de Histología y Embriología, CONICET, Facultad de Ciencias Médicas, CC56, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina and
| | - Silvia A Belmonte
- From the Instituto de Histología y Embriología, CONICET, Facultad de Ciencias Médicas, CC56, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina and
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55
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Wuttke A. Lipid Signalling Dynamics at the β-cell Plasma Membrane. Basic Clin Pharmacol Toxicol 2015; 116:281-90. [DOI: 10.1111/bcpt.12369] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 12/15/2014] [Indexed: 12/26/2022]
Affiliation(s)
- Anne Wuttke
- Department of Medical Cell Biology; Uppsala University; Uppsala Sweden
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56
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Martinello K, Huang Z, Lujan R, Tran B, Watanabe M, Cooper EC, Brown DA, Shah MM. Cholinergic afferent stimulation induces axonal function plasticity in adult hippocampal granule cells. Neuron 2015; 85:346-63. [PMID: 25578363 PMCID: PMC4306544 DOI: 10.1016/j.neuron.2014.12.030] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2014] [Indexed: 01/25/2023]
Abstract
Acetylcholine critically influences hippocampal-dependent learning. Cholinergic fibers innervate hippocampal neuron axons, dendrites, and somata. The effects of acetylcholine on axonal information processing, though, remain unknown. By stimulating cholinergic fibers and making electrophysiological recordings from hippocampal dentate gyrus granule cells, we show that synaptically released acetylcholine preferentially lowered the action potential threshold, enhancing intrinsic excitability and synaptic potential-spike coupling. These effects persisted for at least 30 min after the stimulation paradigm and were due to muscarinic receptor activation. This caused sustained elevation of axonal intracellular Ca2+ via T-type Ca2+ channels, as indicated by two-photon imaging. The enhanced Ca2+ levels inhibited an axonal KV7/M current, decreasing the spike threshold. In support, immunohistochemistry revealed muscarinic M1 receptor, CaV3.2, and KV7.2/7.3 subunit localization in granule cell axons. Since alterations in axonal signaling affect neuronal firing patterns and neurotransmitter release, this is an unreported cellular mechanism by which acetylcholine might, at least partly, enhance cognitive processing. Cholinergic fiber stimulation caused a persistent reduction in the spike threshold Post-synaptic muscarinic receptor activation enhanced axonal CaV3.2 channel activity The sustained Ca2+ entry inhibited axonal KV7 channels, lowering the spike threshold The lower spike threshold increased the propensity for action potential generation
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Affiliation(s)
| | - Zhuo Huang
- UCL School of Pharmacy, University College London, London, WC1N 1AX, UK
| | - Rafael Lujan
- Departamento de Ciencias Medicas, Universidad de Castilla-La Mancha, 02006 Albacete, Spain
| | - Baouyen Tran
- Neurology and Neuroscience, Baylor College of Medicine, TX 77030, USA
| | - Masahiko Watanabe
- Anatomy, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan
| | - Edward C Cooper
- Neurology and Neuroscience, Baylor College of Medicine, TX 77030, USA
| | - David A Brown
- Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, UK
| | - Mala M Shah
- UCL School of Pharmacy, University College London, London, WC1N 1AX, UK.
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57
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Abstract
The goal for the treatment of patients with diabetes has today shifted from merely reducing glucose concentrations to preventing the natural decline in β-cell function and delay the progression of disease. Pancreatic β-cell dysfunction and decreased β-cell mass are crucial in the development of diabetes. The β-cell defects are the main pathogenesis in patients with type 1 diabetes and are associated with type 2 diabetes as the disease progresses. Recent studies suggest that human pancreatic β-cells have a capacity for increased proliferation according to increased demands for insulin. In humans, β-cell mass has been shown to increase in patients showing insulin-resistance states such as obesity or in pregnancy. This capacity might be useful for identifying new therapeutic strategies to reestablish a functional β-cell mass. In this context, therapeutic approaches designed to increase β-cell mass might prove a significant way to manage diabetes and prevent its progression. This review describes the various β-cell defects that appear in patients with diabetes and outline the mechanisms of β-cell failure. We also review common methods for assessing β-cell function and mass and methodological limitations in vivo. Finally, we discuss the current therapeutic approaches to improve β-cell function and increase β-cell mass.
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Affiliation(s)
- Kyong Yeun Jung
- Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
| | - Kyoung Min Kim
- Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
| | - Soo Lim
- Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
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58
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Itsuki K, Imai Y, Hase H, Okamura Y, Inoue R, Mori MX. PLC-mediated PI(4,5)P2 hydrolysis regulates activation and inactivation of TRPC6/7 channels. ACTA ACUST UNITED AC 2014; 143:183-201. [PMID: 24470487 PMCID: PMC4001779 DOI: 10.1085/jgp.201311033] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Transient receptor potential classical (or canonical) (TRPC)3, TRPC6, and TRPC7 are a subfamily of TRPC channels activated by diacylglycerol (DAG) produced through the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) by phospholipase C (PLC). PI(4,5)P2 depletion by a heterologously expressed phosphatase inhibits TRPC3, TRPC6, and TRPC7 activity independently of DAG; however, the physiological role of PI(4,5)P2 reduction on channel activity remains unclear. We used Förster resonance energy transfer (FRET) to measure PI(4,5)P2 or DAG dynamics concurrently with TRPC6 or TRPC7 currents after agonist stimulation of receptors that couple to Gq and thereby activate PLC. Measurements made at different levels of receptor activation revealed a correlation between the kinetics of PI(4,5)P2 reduction and those of receptor-operated TRPC6 and TRPC7 current activation and inactivation. In contrast, DAG production correlated with channel activation but not inactivation; moreover, the time course of channel inactivation was unchanged in protein kinase C-insensitive mutants. These results suggest that inactivation of receptor-operated TRPC currents is primarily mediated by the dissociation of PI(4,5)P2. We determined the functional dissociation constant of PI(4,5)P2 to TRPC channels using FRET of the PLCδ Pleckstrin homology domain (PHd), which binds PI(4,5)P2, and used this constant to fit our experimental data to a model in which channel gating is controlled by PI(4,5)P2 and DAG. This model predicted similar FRET dynamics of the PHd to measured FRET in either human embryonic kidney cells or smooth muscle cells, whereas a model lacking PI(4,5)P2 regulation failed to reproduce the experimental data, confirming the inhibitory role of PI(4,5)P2 depletion on TRPC currents. Our model also explains various PLC-dependent characteristics of channel activity, including limitation of maximum open probability, shortening of the peak time, and the bell-shaped response of total current. In conclusion, our studies demonstrate a fundamental role for PI(4,5)P2 in regulating TRPC6 and TRPC7 activity triggered by PLC-coupled receptor stimulation.
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Affiliation(s)
- Kyohei Itsuki
- Department of Physiology, School of Medicine, Fukuoka University, Fukuoka 814-0180, Japan
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59
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Keum D, Baek C, Kim DI, Kweon HJ, Suh BC. Voltage-dependent regulation of CaV2.2 channels by Gq-coupled receptor is facilitated by membrane-localized β subunit. ACTA ACUST UNITED AC 2014; 144:297-309. [PMID: 25225550 PMCID: PMC4178937 DOI: 10.1085/jgp.201411245] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The pathway through which preferentially GqPCRs inhibit CaV2.2 channels depends on which β subunits are present. G protein–coupled receptors (GPCRs) signal through molecular messengers, such as Gβγ, Ca2+, and phosphatidylinositol 4,5-bisphosphate (PIP2), to modulate N-type voltage-gated Ca2+ (CaV2.2) channels, playing a crucial role in regulating synaptic transmission. However, the cellular pathways through which GqPCRs inhibit CaV2.2 channel current are not completely understood. Here, we report that the location of CaV β subunits is key to determining the voltage dependence of CaV2.2 channel modulation by GqPCRs. Application of the muscarinic agonist oxotremorine-M to tsA-201 cells expressing M1 receptors, together with CaV N-type α1B, α2δ1, and membrane-localized β2a subunits, shifted the current-voltage relationship for CaV2.2 activation 5 mV to the right and slowed current activation. Muscarinic suppression of CaV2.2 activity was relieved by strong depolarizing prepulses. Moreover, when the C terminus of β-adrenergic receptor kinase (which binds Gβγ) was coexpressed with N-type channels, inhibition of CaV2.2 current after M1 receptor activation was markedly reduced and delayed, whereas the delay between PIP2 hydrolysis and inhibition of CaV2.2 current was decreased. When the Gβγ-insensitive CaV2.2 α1C-1B chimera was expressed, voltage-dependent inhibition of calcium current was virtually abolished, suggesting that M1 receptors act through Gβγ to inhibit CaV2.2 channels bearing membrane-localized CaV β2a subunits. Expression of cytosolic β subunits such as β2b and β3, as well as the palmitoylation-negative mutant β2a(C3,4S), reduced the voltage dependence of M1 muscarinic inhibition of CaV2.2 channels, whereas it increased inhibition mediated by PIP2 depletion. Together, our results indicate that, with membrane-localized CaV β subunits, CaV2.2 channels are subject to Gβγ-mediated voltage-dependent inhibition, whereas cytosol-localized β subunits confer more effective PIP2-mediated voltage-independent regulation. Thus, the voltage dependence of GqPCR regulation of calcium channels can be determined by the location of isotype-specific CaV β subunits.
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Affiliation(s)
- Dongil Keum
- Department of Brain Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873, South Korea
| | - Christina Baek
- Department of Brain Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873, South Korea
| | - Dong-Il Kim
- Department of Brain Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873, South Korea
| | - Hae-Jin Kweon
- Department of Brain Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873, South Korea
| | - Byung-Chang Suh
- Department of Brain Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873, South Korea
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Golgi and plasma membrane pools of PI(4)P contribute to plasma membrane PI(4,5)P2 and maintenance of KCNQ2/3 ion channel current. Proc Natl Acad Sci U S A 2014; 111:E2281-90. [PMID: 24843134 DOI: 10.1073/pnas.1407133111] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Plasma membrane (PM) phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] regulates the activity of many ion channels and other membrane-associated proteins. To determine precursor sources of the PM PI(4,5)P2 pool in tsA-201 cells, we monitored KCNQ2/3 channel currents and translocation of PHPLCδ1 domains as real-time indicators of PM PI(4,5)P2, and translocation of PHOSH2×2, and PHOSH1 domains as indicators of PM and Golgi phosphatidylinositol 4-phosphate [PI(4)P], respectively. We selectively depleted PI(4)P pools at the PM, Golgi, or both using the rapamycin-recruitable lipid 4-phosphatases. Depleting PI(4)P at the PM with a recruitable 4-phosphatase (Sac1) results in a decrease of PI(4,5)P2 measured by electrical or optical indicators. Depleting PI(4)P at the Golgi with the 4-phosphatase or disrupting membrane-transporting motors induces a decline in PM PI(4,5)P2. Depleting PI(4)P simultaneously at both the Golgi and the PM induces a larger decrease of PI(4,5)P2. The decline of PI(4,5)P2 following 4-phosphatase recruitment takes 1-2 min. Recruiting the endoplasmic reticulum (ER) toward the Golgi membranes mimics the effects of depleting PI(4)P at the Golgi, apparently due to the trans actions of endogenous ER Sac1. Thus, maintenance of the PM pool of PI(4,5)P2 appears to depend on precursor pools of PI(4)P both in the PM and in the Golgi. The decrease in PM PI(4,5)P2 when Sac1 is recruited to the Golgi suggests that the Golgi contribution is ongoing and that PI(4,5)P2 production may be coupled to important cell biological processes such as membrane trafficking or lipid transfer activity.
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Dickson EJ, Falkenburger BH, Hille B. Quantitative properties and receptor reserve of the IP(3) and calcium branch of G(q)-coupled receptor signaling. ACTA ACUST UNITED AC 2014; 141:521-35. [PMID: 23630337 PMCID: PMC3639578 DOI: 10.1085/jgp.201210886] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Gq-coupled plasma membrane receptors activate phospholipase C (PLC), which hydrolyzes membrane phosphatidylinositol 4,5-bisphosphate (PIP2) into the second messengers inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). This leads to calcium release, protein kinase C (PKC) activation, and sometimes PIP2 depletion. To understand mechanisms governing these diverging signals and to determine which of these signals is responsible for the inhibition of KCNQ2/3 (KV7.2/7.3) potassium channels, we monitored levels of PIP2, IP3, and calcium in single living cells. DAG and PKC are monitored in our companion paper (Falkenburger et al. 2013. J. Gen. Physiol.http://dx.doi.org/10.1085/jgp.201210887). The results extend our previous kinetic model of Gq-coupled receptor signaling to IP3 and calcium. We find that activation of low-abundance endogenous P2Y2 receptors by a saturating concentration of uridine 5′-triphosphate (UTP; 100 µM) leads to calcium release but not to PIP2 depletion. Activation of overexpressed M1 muscarinic receptors by 10 µM Oxo-M leads to a similar calcium release but also depletes PIP2. KCNQ2/3 channels are inhibited by Oxo-M (by 85%), but not by UTP (<1%). These differences can be attributed purely to differences in receptor abundance. Full amplitude calcium responses can be elicited even after PIP2 was partially depleted by overexpressed inducible phosphatidylinositol 5-phosphatases, suggesting that very low amounts of IP3 suffice to elicit a full calcium release. Hence, weak PLC activation can elicit robust calcium signals without net PIP2 depletion or KCNQ2/3 channel inhibition.
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Affiliation(s)
- Eamonn J Dickson
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
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62
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Hille B, Dickson E, Kruse M, Falkenburger B. Dynamic metabolic control of an ion channel. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 123:219-47. [PMID: 24560147 DOI: 10.1016/b978-0-12-397897-4.00008-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
G-protein-coupled receptors mediate responses to external stimuli in various cell types. We are interested in the modulation of KCNQ2/3 potassium channels by the Gq-coupled M1 muscarinic (acetylcholine) receptor (M1R). Here, we describe development of a mathematical model that incorporates all known steps along the M1R signaling cascade and accurately reproduces the macroscopic behavior we observe when KCNQ2/3 currents are inhibited following M1R activation. Gq protein-coupled receptors of the plasma membrane activate phospholipase C (PLC) which cleaves the minor plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) into the second messengers diacylgycerol and inositol 1,4,5-trisphosphate, leading to calcium release, protein kinase C (PKC) activation, and PI(4,5)P2 depletion. Combining optical and electrical techniques with knowledge of relative abundance of each signaling component has allowed us to develop a kinetic model and determine that (i) M1R activation and M1R/Gβ interaction are fast; (ii) Gαq/Gβ separation and Gαq/PLC interaction have intermediate time constants; (iii) the amount of activated PLC limits the rate of KCNQ2/3 suppression; (iv) weak PLC activation can elicit robust calcium signals without net PI(4,5)P2 depletion or KCNQ2/3 channel inhibition; and (v) depletion of PI(4,5)P2, and not calcium/CaM or PKC-mediated phosphorylation, closes KCNQ2/3 potassium channels, thereby increasing neuronal excitability.
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Affiliation(s)
- Bertil Hille
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Eamonn Dickson
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Martin Kruse
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
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Tan J, Brill JA. Cinderella story: PI4P goes from precursor to key signaling molecule. Crit Rev Biochem Mol Biol 2013; 49:33-58. [PMID: 24219382 DOI: 10.3109/10409238.2013.853024] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Phosphatidylinositol lipids are signaling molecules involved in nearly all aspects of cellular regulation. Production of phosphatidylinositol 4-phosphate (PI4P) has long been recognized as one of the first steps in generating poly-phosphatidylinositol phosphates involved in actin organization, cell migration, and signal transduction. In addition, progress over the last decade has brought to light independent roles for PI4P in membrane trafficking and lipid homeostasis. Here, we describe recent advances that reveal the breadth of processes regulated by PI4P, the spectrum of PI4P effectors, and the mechanisms of spatiotemporal control that coordinate crosstalk between PI4P and cellular signaling pathways.
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Affiliation(s)
- Julie Tan
- Department of Molecular Genetics, University of Toronto , Toronto, Ontario , Canada and
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The actions of Pasteurella multocida toxin on neuronal cells. Neuropharmacology 2013; 77:9-18. [PMID: 24055502 PMCID: PMC3878393 DOI: 10.1016/j.neuropharm.2013.09.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 09/03/2013] [Accepted: 09/05/2013] [Indexed: 02/06/2023]
Abstract
Pasteurella multocida toxin (PMT) activates the G-proteins Gαi(1-3), Gαq, Gα11, Gα12 and Gα13 by deamidation of specific glutamine residues. A number of these alpha subunits have signalling roles in neurones. Hence we studied the action of this toxin on rat superior cervical ganglion (SCG) neurones and NG108-15 neuronal cells. Both Gαq and Gα11 could be identified in SCGs with immunocytochemistry. PMT had no direct action on Kv7 or Cav2 channels in SCGs. However PMT treatment enhanced muscarinic receptor mediated inhibition of M-current (Kv7.2 + 7. 3) as measured by a 19-fold leftward shift in the oxotremorine-M concentration–inhibition curve. Agonists of other receptors, such as bradykinin or angiotensin, that inhibit M-current did not produce this effect. However the amount of PIP2 hydrolysis could be enhanced by PMT for all three agonists. In a transduction system in SCGs that is unlikely to be affected by PMT, Go mediated inhibition of calcium current, PMT was ineffective whereas the response was blocked by pertussis toxin as expected. M1 muscarinic receptor evoked calcium mobilisation in transformed NG108-15 cells was enhanced by PMT. The calcium rises evoked by uridine triphosphate acting on endogenous P2Y2 receptors in NG108-15 cells were enhanced by PMT. The time and concentration dependence of the PMT effect was different for the resting calcium compared to the calcium rise produced by activation of P2Y2 receptors. PMT's action on these neuronal cells would suggest that if it got into the brain, symptoms of a hyperexcitable nature would be seen, such as seizures. Pasteurella multocida toxin (PMT) activates a range of G-protein alpha subunits. PMT increased muscarinic receptor mediated suppression of Kv7 potassium current in sympathetic neurones. PMT enhances both muscarinic and purinergic receptor mediated calcium mobilisation in NG108-15 cells. Both these events are mediated by the G-proteins Gq or G11. We would predict that the symptoms of central nervous system PMT toxicity would be hyperexcitable events such as seizures.
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Cockcroft S, Garner K. Potential role for phosphatidylinositol transfer protein (PITP) family in lipid transfer during phospholipase C signalling. Adv Biol Regul 2013; 53:280-291. [PMID: 23916246 DOI: 10.1016/j.jbior.2013.07.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 07/11/2013] [Accepted: 07/12/2013] [Indexed: 06/02/2023]
Abstract
The hallmark of mammalian phosphatidylinositol transfer proteins (PITPs) is to transfer phosphatidylinositol between membrane compartments. In the mammalian genome, there are three genes that code for soluble PITP proteins, PITPα, PITPβ and RdgBβ and two genes that code for membrane-associated multi-domain proteins (RdgBαI and II) containing a PITP domain. PITPα and PITPβ constitute Class I PITPs whilst the RdgB proteins constitute Class II proteins based on sequence analysis. The PITP domain of both Class I and II can sequester one molecule of phosphatidylinositol (PI) in its hydrophobic cavity. Therefore, in principle, PITPs are therefore ideally poised to couple phosphatidylinositol delivery to the PI kinases for substrate provision for phospholipases C during cell activation. Since phosphatidylinositol (4,5)bisphosphate plays critical roles in cells, particularly at the plasma membrane, where it is a substrate for both phospholipase C and phosphoinositide-3-kinases as well as required as an intact lipid to regulate ion channels and the actin cytoskeleton, homeostatic mechanisms to maintain phosphatidylinositol(4,5)bisphosphate levels are vital. To maintain phosphatidylinositol levels, phospholipase C activation inevitably leads to the resynthesis of PI at the endoplasmic reticulum where the enzymes are located. Phosphatidic acid generated at the plasma membrane during phospholipase C activation needs to move to the ER for conversion to PI and here we provide evidence that Class II PITPs are also able to bind and transport phosphatidic acid. Thus RdgB proteins could couple PA and PI transport bidirectionally during phospholipase C signalling.
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Affiliation(s)
- Shamshad Cockcroft
- Dept. of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, London WC1E 6JJ, UK.
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Mak DOD. A mechanism for different receptors coupled to the same G protein to generate different responses mediated by different second messengers. J Gen Physiol 2013; 141:513-6. [PMID: 23630335 PMCID: PMC3639579 DOI: 10.1085/jgp.201311006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Don-On Daniel Mak
- Physiology Department, University of Pennsylvania, Philadelphia, PA 19104, USA.
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