1
|
Nakamura N, Honjo M, Yamagishi-Kimura R, Sakata R, Watanabe S, Aihara M. Neuroprotective effect of omidenepag on excitotoxic retinal ganglion cell death regulating COX-2-EP2-cAMP-PKA/Epac pathway via Neuron-Glia interaction. Neuroscience 2024; 553:145-159. [PMID: 38992567 DOI: 10.1016/j.neuroscience.2024.07.006] [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: 10/18/2023] [Revised: 06/03/2024] [Accepted: 07/04/2024] [Indexed: 07/13/2024]
Abstract
Glutamate excitotoxicity is involved in retinal ganglion cell (RGC) death in various retinal degenerative diseases, including ischemia-reperfusion injury and glaucoma. Excitotoxic RGC death is caused by both direct damage to RGCs and indirect damage through neuroinflammation of retinal glial cells. Omidenepag (OMD), a novel E prostanoid receptor 2 (EP2) agonist, is a recently approved intraocular pressure-lowering drug. The second messenger of EP2 is cyclic adenosine monophosphate (cAMP), which activates protein kinase A (PKA) and exchange protein directly activated by cAMP (Epac). In this study, we investigated the neuroprotective effects of OMD on excitotoxic RGC death by focusing on differences in cAMP downstream signaling from the perspective of glia-neuron interactions. We established a glutamate excitotoxicity model in vitro and NMDA intravitreal injection model in vivo. In vitro, rat primary RGCs were used in an RGC survival rate assay. MG5 cells (mouse microglial cell line) and A1 cells (astrocyte cell line) were used for immunocytochemistry and Western blotting to evaluate the expressions of COX-1/2, PKA, Epac1/2, pCREB, cleaved caspase-3, inflammatory cytokines, and neurotrophic factors. Mouse retinal specimens underwent hematoxylin and eosin staining, flat-mounted retina examination, and immunohistochemistry. OMD significantly suppressed excitotoxic RGC death, cleaved caspase-3 expression, and activated glia both in vitro and in vivo. Moreover, it inhibited Epac1 and inflammatory cytokine expression and promoted COX-2, pCREB, and neurotrophic factor expression. OMD may have neuroprotective effects through inhibition of the Epac pathway and promotion of the COX-2-EP2-cAMP-PKA pathway by modulating glia-neuron interaction.
Collapse
Affiliation(s)
- Natsuko Nakamura
- Department of Ophthalmology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; Division of Vision Research, National Institute of Sensory Organs, NHO Tokyo Medical Center, Tokyo, Japan; Department of Ophthalmology, Kobe City Eye Hospital, Kobe, Japan
| | - Megumi Honjo
- Department of Ophthalmology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
| | - Reiko Yamagishi-Kimura
- Department of Ophthalmology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Rei Sakata
- Department of Ophthalmology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Sumiko Watanabe
- Department of Ophthalmology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Makoto Aihara
- Department of Ophthalmology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| |
Collapse
|
2
|
Wu L, Wang F, Moncman CL, Pandey M, Clarke HA, Frazier HN, Young LE, Gentry MS, Cai W, Thibault O, Sun RC, Andres DA. RIT1 regulation of CNS lipids RIT1 deficiency Alters cerebral lipid metabolism and reduces white matter tract oligodendrocytes and conduction velocities. Heliyon 2023; 9:e20384. [PMID: 37780758 PMCID: PMC10539968 DOI: 10.1016/j.heliyon.2023.e20384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 07/21/2023] [Accepted: 09/20/2023] [Indexed: 10/03/2023] Open
Abstract
Oligodendrocytes (OLs) generate lipid-rich myelin membranes that wrap axons to enable efficient transmission of electrical impulses. Using a RIT1 knockout mouse model and in situ high-resolution matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) coupled with MS-based lipidomic analysis to determine the contribution of RIT1 to lipid homeostasis. Here, we report that RIT1 loss is associated with altered lipid levels in the central nervous system (CNS), including myelin-associated lipids within the corpus callosum (CC). Perturbed lipid metabolism was correlated with reduced numbers of OLs, but increased numbers of GFAP+ glia, in the CC, but not in grey matter. This was accompanied by reduced myelin protein expression and axonal conduction deficits. Behavioral analyses revealed significant changes in voluntary locomotor activity and anxiety-like behavior in RIT1KO mice. Together, these data reveal an unexpected role for RIT1 in the regulation of cerebral lipid metabolism, which coincide with altered white matter tract oligodendrocyte levels, reduced axonal conduction velocity, and behavioral abnormalities in the CNS.
Collapse
Affiliation(s)
- Lei Wu
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
| | - Fang Wang
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
| | - Carole L. Moncman
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
| | - Mritunjay Pandey
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
| | - Harrison A. Clarke
- Department of Neuroscience, College of Medicine, University of Kentucky, KY 40536, USA
| | - Hilaree N. Frazier
- Department of Pharmacological and Nutritional Sciences, College of Medicine, University of Kentucky, KY 40536, USA
| | - Lyndsay E.A. Young
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
- Markey Cancer Center, Lexington, KY 40536, USA
| | - Matthew S. Gentry
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
- Markey Cancer Center, Lexington, KY 40536, USA
- Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, Gainesville, FL 32611, USA
- Center for Advanced Spatial Biomolecule Research, University of Florida, College of Medicine, Gainesville, FL 32611, USA
| | - Weikang Cai
- Department of Biomedical Sciences, New York Institute of Technology College of Osteopathic Medicine, NY 11568, USA
| | - Olivier Thibault
- Department of Pharmacological and Nutritional Sciences, College of Medicine, University of Kentucky, KY 40536, USA
| | - Ramon C. Sun
- Department of Neuroscience, College of Medicine, University of Kentucky, KY 40536, USA
- Markey Cancer Center, Lexington, KY 40536, USA
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY 40536, USA
- Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, Gainesville, FL 32611, USA
- Center for Advanced Spatial Biomolecule Research, University of Florida, College of Medicine, Gainesville, FL 32611, USA
| | - Douglas A. Andres
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, KY 40536, USA
- Markey Cancer Center, Lexington, KY 40536, USA
- Spinal Cord and Brain Injury Research Center, College of Medicine, University of Kentucky, KY 40536, USA
- Gill Heart and Vascular Institute, College of Medicine, University of Kentucky, Lexington, KY 40536, USA
| |
Collapse
|
3
|
Slika H, Mansour H, Nasser SA, Shaito A, Kobeissy F, Orekhov AN, Pintus G, Eid AH. Epac as a tractable therapeutic target. Eur J Pharmacol 2023; 945:175645. [PMID: 36894048 DOI: 10.1016/j.ejphar.2023.175645] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Revised: 02/26/2023] [Accepted: 03/06/2023] [Indexed: 03/09/2023]
Abstract
In 1957, cyclic adenosine monophosphate (cAMP) was identified as the first secondary messenger, and the first signaling cascade discovered was the cAMP-protein kinase A (PKA) pathway. Since then, cAMP has received increasing attention given its multitude of actions. Not long ago, a new cAMP effector named exchange protein directly activated by cAMP (Epac) emerged as a critical mediator of cAMP's actions. Epac mediates a plethora of pathophysiologic processes and contributes to the pathogenesis of several diseases such as cancer, cardiovascular disease, diabetes, lung fibrosis, neurological disorders, and others. These findings strongly underscore the potential of Epac as a tractable therapeutic target. In this context, Epac modulators seem to possess unique characteristics and advantages and hold the promise of providing more efficacious treatments for a wide array of diseases. This paper provides an in-depth dissection and analysis of Epac structure, distribution, subcellular compartmentalization, and signaling mechanisms. We elaborate on how these characteristics can be utilized to design specific, efficient, and safe Epac agonists and antagonists that can be incorporated into future pharmacotherapeutics. In addition, we provide a detailed portfolio for specific Epac modulators highlighting their discovery, advantages, potential concerns, and utilization in the context of clinical disease entities.
Collapse
Affiliation(s)
- Hasan Slika
- Department of Pharmacology and Toxicology, American University of Beirut, Beirut, P.O. Box 11-0236, Lebanon.
| | - Hadi Mansour
- Department of Pharmacology and Toxicology, American University of Beirut, Beirut, P.O. Box 11-0236, Lebanon.
| | | | - Abdullah Shaito
- Biomedical Research Center, Qatar University, Doha, P.O. Box: 2713, Qatar.
| | - Firas Kobeissy
- Department of Neurobiology and Neuroscience, Morehouse School of Medicine, Atlanta, Georgia, USA.
| | - Alexander N Orekhov
- Laboratory of Cellular and Molecular Pathology of Cardiovascular System, Institute of Human Morphology, 3 Tsyurupa Street, Moscow, 117418, Russia; Laboratory of Angiopathology, Institute of General Pathology and Pathophysiology, 8 Baltiiskaya Street, Moscow, 125315, Russia; Institute for Atherosclerosis Research, Skolkovo Innovative Center, Osennyaya Street 4-1-207, Moscow, 121609, Russia.
| | - Gianfranco Pintus
- Department of Biomedical Sciences, University of Sassari, 07100, Sassari, Italy.
| | - Ali H Eid
- Department of Basic Medical Sciences, College of Medicine, QU Health, Qatar University, Doha, P.O. Box 2713, Qatar.
| |
Collapse
|
4
|
Lu J, Piper SJ, Zhao P, Miller LJ, Wootten D, Sexton PM. Targeting VIP and PACAP Receptor Signaling: New Insights into Designing Drugs for the PACAP Subfamily of Receptors. Int J Mol Sci 2022; 23:8069. [PMID: 35897648 PMCID: PMC9331257 DOI: 10.3390/ijms23158069] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 07/18/2022] [Accepted: 07/20/2022] [Indexed: 12/16/2022] Open
Abstract
Pituitary Adenylate Cyclase-Activating Peptide (PACAP) and Vasoactive Intestinal Peptide (VIP) are neuropeptides involved in a diverse array of physiological and pathological processes through activating the PACAP subfamily of class B1 G protein-coupled receptors (GPCRs): VIP receptor 1 (VPAC1R), VIP receptor 2 (VPAC2R), and PACAP type I receptor (PAC1R). VIP and PACAP share nearly 70% amino acid sequence identity, while their receptors PAC1R, VPAC1R, and VPAC2R share 60% homology in the transmembrane regions of the receptor. PACAP binds with high affinity to all three receptors, while VIP binds with high affinity to VPAC1R and VPAC2R, and has a thousand-fold lower affinity for PAC1R compared to PACAP. Due to the wide distribution of VIP and PACAP receptors in the body, potential therapeutic applications of drugs targeting these receptors, as well as expected undesired side effects, are numerous. Designing selective therapeutics targeting these receptors remains challenging due to their structural similarities. This review discusses recent discoveries on the molecular mechanisms involved in the selectivity and signaling of the PACAP subfamily of receptors, and future considerations for therapeutic targeting.
Collapse
Affiliation(s)
- Jessica Lu
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia; (J.L.); (S.J.P.); (P.Z.)
| | - Sarah J. Piper
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia; (J.L.); (S.J.P.); (P.Z.)
| | - Peishen Zhao
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia; (J.L.); (S.J.P.); (P.Z.)
| | - Laurence J. Miller
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ 85259, USA;
| | - Denise Wootten
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia; (J.L.); (S.J.P.); (P.Z.)
| | - Patrick M. Sexton
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia; (J.L.); (S.J.P.); (P.Z.)
| |
Collapse
|
5
|
Ahmed MB, Alghamdi AAA, Islam SU, Lee JS, Lee YS. cAMP Signaling in Cancer: A PKA-CREB and EPAC-Centric Approach. Cells 2022; 11:cells11132020. [PMID: 35805104 PMCID: PMC9266045 DOI: 10.3390/cells11132020] [Citation(s) in RCA: 36] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 06/17/2022] [Accepted: 06/23/2022] [Indexed: 02/01/2023] Open
Abstract
Cancer is one of the most common causes of death globally. Despite extensive research and considerable advances in cancer therapy, the fundamentals of the disease remain unclear. Understanding the key signaling mechanisms that cause cancer cell malignancy may help to uncover new pharmaco-targets. Cyclic adenosine monophosphate (cAMP) regulates various biological functions, including those in malignant cells. Understanding intracellular second messenger pathways is crucial for identifying downstream proteins involved in cancer growth and development. cAMP regulates cell signaling and a variety of physiological and pathological activities. There may be an impact on gene transcription from protein kinase A (PKA) as well as its downstream effectors, such as cAMP response element-binding protein (CREB). The position of CREB downstream of numerous growth signaling pathways implies its oncogenic potential in tumor cells. Tumor growth is associated with increased CREB expression and activation. PKA can be used as both an onco-drug target and a biomarker to find, identify, and stage tumors. Exploring cAMP effectors and their downstream pathways in cancer has become easier using exchange protein directly activated by cAMP (EPAC) modulators. This signaling system may inhibit or accelerate tumor growth depending on the tumor and its environment. As cAMP and its effectors are critical for cancer development, targeting them may be a useful cancer treatment strategy. Moreover, by reviewing the material from a distinct viewpoint, this review aims to give a knowledge of the impact of the cAMP signaling pathway and the related effectors on cancer incidence and development. These innovative insights seek to encourage the development of novel treatment techniques and new approaches.
Collapse
Affiliation(s)
- Muhammad Bilal Ahmed
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, College of Natural Sciences, Kyungpook National University, Daegu 41566, Korea; (M.B.A.); (J.-S.L.)
| | | | - Salman Ul Islam
- Department of Pharmacy, Cecos University, Peshawar, Street 1, Sector F 5 Phase 6 Hayatabad, Peshawar 25000, Pakistan;
| | - Joon-Seok Lee
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, College of Natural Sciences, Kyungpook National University, Daegu 41566, Korea; (M.B.A.); (J.-S.L.)
| | - Young-Sup Lee
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, College of Natural Sciences, Kyungpook National University, Daegu 41566, Korea; (M.B.A.); (J.-S.L.)
- Correspondence: ; Tel.: +82-53-950-6353; Fax: +82-53-943-2762
| |
Collapse
|
6
|
The Role of Neuropeptide-Stimulated cAMP-EPACs Signalling in Cancer Cells. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27010311. [PMID: 35011543 PMCID: PMC8746471 DOI: 10.3390/molecules27010311] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 12/23/2021] [Accepted: 12/27/2021] [Indexed: 02/06/2023]
Abstract
Neuropeptides are autocrine and paracrine signalling factors and mainly bind to G protein-coupled receptors (GPCRs) to trigger intracellular secondary messenger release including adenosine 3′, 5′-cyclic monophosphate (cAMP), thus modulating cancer progress in different kind of tumours. As one of the downstream effectors of cAMP, exchange proteins directly activated by cAMP (EPACs) play dual roles in cancer proliferation and metastasis. More evidence about the relationship between neuropeptides and EPAC pathways have been proposed for their potential role in cancer development; hence, this review focuses on the role of neuropeptide/GPCR system modulation of cAMP/EPACs pathways in cancers. The correlated downstream pathways between neuropeptides and EPACs in cancer cell proliferation, migration, and metastasis is discussed to glimmer the direction of future research.
Collapse
|
7
|
An J, Chen B, Tian D, Guo Y, Yan Y, Yang H. Regulation of Neurogenesis and Neuronal Differentiation by Natural Compounds. Curr Stem Cell Res Ther 2021; 17:756-771. [PMID: 34493197 DOI: 10.2174/1574888x16666210907141447] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 07/15/2021] [Accepted: 07/28/2021] [Indexed: 11/22/2022]
Abstract
Neuronal damage or degeneration is the main feature of neurological diseases. Regulation of neurogenesis and neuronal differentiation is important in developing therapies to promote neuronal regeneration or synaptic network reconstruction. Neurogenesis is a multistage process in which neurons are generated and integrated into existing neuronal circuits. Neuronal differentiation is extremely complex because it can occur in different cell types and can be caused by a variety of inducers. Recently, natural compounds that induce neurogenesis and neuronal differentiation have attracted extensive attention. In this paper, the potential neural induction effects of medicinal plant-derived natural compounds on neural stem/progenitor cells (NS/PCs), the cultured neuronal cells, and mesenchymal stem cells (MSCs) are reviewed. The natural compounds that are efficacious in inducing neurogenesis and neuronal differentiation include phenolic acids, polyphenols, flavonoids, glucosides, alkaloids, terpenoids, quinones, coumarins, and others. They exert neural induction effects by regulating signal factors and cell-specific genes involved in the process of neurogenesis and neuronal differentiation, including specific proteins (β-tubulin III, MAP-2, tau, nestin, neurofilaments, GFAP, GAP-43, NSE), related genes and proteins (STAT3, Hes1, Mash1, NeuroD1, notch, cyclin D1, SIRT1, reggie-1), transcription factors (CREB, Nkx-2.5, Ngn1), neurotrophins (BDNF, NGF, NT-3) and signaling pathways (JAK/STAT, Wnt/β-catenin, MAPK, PI3K/Akt, GSK-3β/β-catenin, Ca2+/CaMKII/ATF1, Nrf2/HO-1, BMP). The natural compounds with neural induction effects are of great value for neuronal regenerative medicine and provide promising prevention and treatment strategies for neurological diseases.
Collapse
Affiliation(s)
- Jing An
- Translational Medicine Centre, Honghui Hospital, Xi'an Jiaotong University, Xi'an. China
| | - Bo Chen
- Translational Medicine Centre, Honghui Hospital, Xi'an Jiaotong University, Xi'an. China
| | - Ding Tian
- Translational Medicine Centre, Honghui Hospital, Xi'an Jiaotong University, Xi'an. China
| | - Yunshan Guo
- Department of Spine Surgery, Honghui Hospital, Xi'an Jiaotong University, Xi'an. China
| | - Yuzhu Yan
- Clinical Lab, Honghui Hospital, Xi'an Jiaotong University, Xi'an. China
| | - Hao Yang
- Translational Medicine Centre, Honghui Hospital, Xi'an Jiaotong University, Xi'an. China
| |
Collapse
|
8
|
Maher A, El Sayed N, Nafea H, Gad M. Rolipram rescues memory consolidation deficits caused by sleep deprivation: Implication of the cAMP/PKA and cAMP/Epac pathways. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2021; 21:631-639. [PMID: 34397335 DOI: 10.2174/1871527320666210816105144] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 07/16/2021] [Accepted: 07/20/2021] [Indexed: 11/22/2022]
Abstract
BACKGROUND Over the last few years, the number of people suffering from sleeping disorders has increased significantly despite negative effects on cognition and an association with brain inflammation. OBJECTIVES We assessed memory deficits caused by sleep deprivation (SD) to determine the therapeutic effect of phosphodiesterase 4 (PDE4) inhibitors on SD-induced memory deficits and to investigate whether the modulation of memory deficits by PDE4 inhibitors is mediated by a protein kinase A (PKA)-independent pathway in conjunction with a PKA-dependent pathway. METHODS Adult male mice were divided into four groups. Three SD groups were deprived of Rapid eye movement (REM) sleep for 12 h a day for six consecutive days. They were tested daily in the Morris water maze to evaluate learning and memory. One of the SD groups was injected with a PDE4 inhibitor, rolipram (1 mg/kg ip), whereas another had rolipram co-administered with chlorogenic acid (CHA, 20 mg/kg ip), an inhibitor of PKA. After 6 days, the mice were sacrificed, and the hippocampi were evaluated for cyclic AMP (cAMP) and nuclear factor Nrf-2 levels. The hippocampal expression of PKA, phosphorylated cAMP response element-binding protein (CREB), and phosphorylated glycogen synthase 3β (Ser389) were also evaluated. RESULTS SD caused a significant decrease in cAMP levels in the brain and had a detrimental effect on learning and memory. The administration of rolipram or rolipram+CHA resulted in an improvement in cognitive function. CONCLUSION The present study provides evidence that restoration of memory with PDE4 inhibitors occurs through a dual mechanism involving the PKA and Epac pathways.
Collapse
Affiliation(s)
- Ahmed Maher
- Biochemistry Department, Faculty of Pharmacy, October University for Modern Sciences and Arts (MSA), Cairo. Egypt
| | - Nesrine El Sayed
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Cairo University. Egypt
| | - Heba Nafea
- Biochemistry Department, Faculty of Pharmacy and Biotechnology, German University in Cairo (GUC), Cairo. Egypt
| | - Mohamed Gad
- Biochemistry Department, Faculty of Pharmacy and Biotechnology, German University in Cairo (GUC), Cairo. Egypt
| |
Collapse
|
9
|
Abstract
The well-known second messenger cyclic adenosine monophosphate (cAMP) regulates the morphology and physiology of neurons and thus higher cognitive brain functions. The discovery of exchange protein activated by cAMP (Epac) as a guanine nucleotide exchange factor for Rap GTPases has shed light on protein kinase A (PKA)-independent functions of cAMP signaling in neural tissues. Studies of cAMP-Epac-mediated signaling in neurons under normal and disease conditions also revealed its diverse contributions to neurodevelopment, synaptic remodeling, and neurotransmitter release, as well as learning, memory, and emotion. In this mini-review, the various roles of Epac isoforms, including Epac1 and Epac2, highly expressed in neural tissues are summarized, and controversies or issues are highlighted that need to be resolved to uncover the critical functions of Epac in neural tissues and the potential for a new therapeutic target of mental disorders.
Collapse
Affiliation(s)
- Kyungmin Lee
- Laboratory for Behavioral Neural Circuitry and Physiology, Department of Anatomy, Brain Science & Engineering Institute, School of Medicine, Kyungpook National University, Daegu 41944, Korea
| |
Collapse
|
10
|
GRKs and Epac1 Interaction in Cardiac Remodeling and Heart Failure. Cells 2021; 10:cells10010154. [PMID: 33466800 PMCID: PMC7830799 DOI: 10.3390/cells10010154] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 01/06/2021] [Accepted: 01/08/2021] [Indexed: 12/25/2022] Open
Abstract
β-adrenergic receptors (β-ARs) play a major role in the physiological regulation of cardiac function through signaling routes tightly controlled by G protein-coupled receptor kinases (GRKs). Although the acute stimulation of β-ARs and the subsequent production of cyclic AMP (cAMP) have beneficial effects on cardiac function, chronic stimulation of β-ARs as observed under sympathetic overdrive promotes the development of pathological cardiac remodeling and heart failure (HF), a leading cause of mortality worldwide. This is accompanied by an alteration in cAMP compartmentalization and the activation of the exchange protein directly activated by cAMP 1 (Epac1) signaling. Among downstream signals of β-ARs, compelling evidence indicates that GRK2, GRK5, and Epac1 represent attractive therapeutic targets for cardiac disease. Here, we summarize the pathophysiological roles of GRK2, GRK5, and Epac1 in the heart. We focus on their signalosome and describe how under pathological settings, these proteins can cross-talk and are part of scaffolded nodal signaling systems that contribute to a decreased cardiac function and HF development.
Collapse
|
11
|
Schreiber R, Hollands R, Blokland A. A Mechanistic Rationale for PDE-4 Inhibitors to Treat Residual Cognitive Deficits in Acquired Brain Injury. Curr Neuropharmacol 2020; 18:188-201. [PMID: 31660837 PMCID: PMC7327948 DOI: 10.2174/1570159x17666191010103044] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 08/06/2019] [Accepted: 10/03/2019] [Indexed: 02/06/2023] Open
Abstract
Patients with acquired brain injury (ABI) suffer from cognitive deficits that interfere significantly with their daily lives. These deficits are long-lasting and no treatment options are available. A better understanding of the mechanistic basis for these cognitive deficits is needed to develop novel treatments. Intracellular cyclic adenosine monophosphate (cAMP) levels are decreased in ABI. Herein, we focus on augmentation of cAMP by PDE4 inhibitors and the potentially synergistic mechanisms in traumatic brain injury. A major acute pathophysiological event in ABI is the breakdown of the blood-brain-barrier (BBB). Intracellular cAMP pathways are involved in the subsequent emergence of edema, inflammation and hyperexcitability. We propose that PDE4 inhibitors such as roflumilast can improve cognition by modulation of the activity in the cAMP-Phosphokinase A-Ras-related C3 botulinum toxin substrate (RAC1) inflammation pathway. In addition, PDE4 inhibitors can also directly enhance network plasticity and attenuate degenerative processes and cognitive dysfunction by increasing activity of the canonical cAMP/phosphokinase-A/cAMP Responsive Element Binding protein (cAMP/PKA/CREB) plasticity pathway. Doublecourtin and microtubule-associated protein 2 are generated following activation of the cAMP/PKA/CREB pathway and are decreased or even absent after injury. Both proteins are involved in neuronal plasticity and may consist of viable markers to track these processes. It is concluded that PDE4 inhibitors may consist of a novel class of drugs for the treatment of residual symptoms in ABI attenuating the pathophysiological consequences of a BBB breakdown by their anti-inflammatory actions via the cAMP/PKA/RAC1 pathway and by increasing synaptic plasticity via the cAMP/PKA/CREB pathway. Roflumilast improves cognition in young and elderly humans and would be an excellent candidate for a proof of concept study in ABI patients.
Collapse
Affiliation(s)
- Rudy Schreiber
- Faculty of Psychology and Neuroscience, Section Neuropsychology and Psychopharmacology, Maastricht University, PO BOX 616, 6200 MD Maastricht, Netherlands
| | - Romain Hollands
- Faculty of Psychology and Neuroscience, Section Neuropsychology and Psychopharmacology, Maastricht University, PO BOX 616, 6200 MD Maastricht, Netherlands
| | - Arjan Blokland
- Faculty of Psychology and Neuroscience, Section Neuropsychology and Psychopharmacology, Maastricht University, PO BOX 616, 6200 MD Maastricht, Netherlands
| |
Collapse
|
12
|
Wehbe N, Slika H, Mesmar J, Nasser SA, Pintus G, Baydoun S, Badran A, Kobeissy F, Eid AH, Baydoun E. The Role of Epac in Cancer Progression. Int J Mol Sci 2020; 21:ijms21186489. [PMID: 32899451 PMCID: PMC7555121 DOI: 10.3390/ijms21186489] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 07/28/2020] [Accepted: 07/29/2020] [Indexed: 12/14/2022] Open
Abstract
Cancer continues to be a prime contributor to global mortality. Despite tremendous research efforts and major advances in cancer therapy, much remains to be learned about the underlying molecular mechanisms of this debilitating disease. A better understanding of the key signaling events driving the malignant phenotype of cancer cells may help identify new pharmaco-targets. Cyclic adenosine 3',5'-monophosphate (cAMP) modulates a plethora of biological processes, including those that are characteristic of malignant cells. Over the years, most cAMP-mediated actions were attributed to the activity of its effector protein kinase A (PKA). However, studies have revealed an important role for the exchange protein activated by cAMP (Epac) as another effector mediating the actions of cAMP. In cancer, Epac appears to have a dual role in regulating cellular processes that are essential for carcinogenesis. In addition, the development of Epac modulators offered new routes to further explore the role of this cAMP effector and its downstream pathways in cancer. In this review, the potentials of Epac as an attractive target in the fight against cancer are depicted. Additionally, the role of Epac in cancer progression, namely its effect on cancer cell proliferation, migration/metastasis, and apoptosis, with the possible interaction of reactive oxygen species (ROS) in these phenomena, is discussed with emphasis on the underlying mechanisms and pathways.
Collapse
Affiliation(s)
- Nadine Wehbe
- Department of Biology, American University of Beirut, P.O. Box 11-0236 Beirut, Lebanon; (N.W.); (J.M.)
| | - Hasan Slika
- Department of Pharmacology and Therapeutics, Faculty of Medicine, American University of Beirut, P.O. Box 11-0236 Beirut, Lebanon;
| | - Joelle Mesmar
- Department of Biology, American University of Beirut, P.O. Box 11-0236 Beirut, Lebanon; (N.W.); (J.M.)
| | - Suzanne A. Nasser
- Department of Pharmacology, Beirut Arab University, P.O. Box 11-5020 Beirut, Lebanon;
| | - Gianfranco Pintus
- Department of Biomedical Sciences, University of Sharjah, P.O. Box 27272 Sharjah, UAE;
- Department of Biomedical Sciences, University of Sassari, Viale San Pietro 43, 07100 Sassari, Italy
| | - Serine Baydoun
- Department of Radiology, American University of Beirut, P.O. Box 11-0236 Beirut, Lebanon;
| | - Adnan Badran
- Department of Basic Sciences, University of Petra, P.O. Box 961343, Amman 11196, Jordan;
| | - Firas Kobeissy
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, P.O. Box 11-0236, Beirut, Lebanon;
| | - Ali H. Eid
- Department of Pharmacology and Therapeutics, Faculty of Medicine, American University of Beirut, P.O. Box 11-0236 Beirut, Lebanon;
- Department of Pharmacology and Therapeutics, Faculty of Medicine, American University of Beirut, P.O. Box 11-0236, Beirut, Lebanon
- Correspondence: (A.H.E.); (E.B.); Tel.: +961-1-350-000 (ext. 4891) (A.H.E. & E.B.)
| | - Elias Baydoun
- Department of Biology, American University of Beirut, P.O. Box 11-0236 Beirut, Lebanon; (N.W.); (J.M.)
- Correspondence: (A.H.E.); (E.B.); Tel.: +961-1-350-000 (ext. 4891) (A.H.E. & E.B.)
| |
Collapse
|
13
|
Van R, Cuevas-Navarro A, Castel P, McCormick F. The molecular functions of RIT1 and its contribution to human disease. Biochem J 2020; 477:2755-2770. [PMID: 32766847 PMCID: PMC7787054 DOI: 10.1042/bcj20200442] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/01/2020] [Accepted: 07/02/2020] [Indexed: 12/29/2022]
Abstract
RIT1 is a member of the Ras family of GTPases that direct broad cellular physiological responses through tightly controlled signaling networks. The canonical Ras GTPases are well-defined regulators of the RAF/MEK/ERK pathway and mutations in these are pathogenic in cancer and a class of developmental disorders termed RASopathies. Emerging clinical evidences have now demonstrated a role for RIT1 in RASopathies, namely Noonan syndrome, and various cancers including lung adenocarcinoma and myeloid malignancies. While RIT1 has been mostly described in the context of neuronal differentiation and survival, the mechanisms underlying aberrant RIT1-mediated signaling remain elusive. Here, we will review efforts undertaken to characterize the biochemical and functional properties of the RIT1 GTPase at the molecular, cellular, and organismal level, as well as provide a phenotypic overview of different human conditions caused by RIT1 mutations. Deeper understanding of RIT1 biological function and insight to its pathogenic mechanisms are imperative to developing effective therapeutic interventions for patients with RIT1-mutant Noonan syndrome and cancer.
Collapse
Affiliation(s)
- Richard Van
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, U.S.A
| | - Antonio Cuevas-Navarro
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, U.S.A
| | - Pau Castel
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, U.S.A
| | - Frank McCormick
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, U.S.A
| |
Collapse
|
14
|
Hara M, Takeba Y, Iiri T, Ohta Y, Ootaki M, Watanabe M, Watanabe D, Koizumi S, Otsubo T, Matsumoto N. Vasoactive intestinal peptide increases apoptosis of hepatocellular carcinoma by inhibiting the cAMP/Bcl-xL pathway. Cancer Sci 2018; 110:235-244. [PMID: 30390393 PMCID: PMC6317926 DOI: 10.1111/cas.13861] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Revised: 10/25/2018] [Accepted: 11/01/2018] [Indexed: 12/12/2022] Open
Abstract
Vasoactive intestinal peptide (VIP) is a modulator of inflammatory responses. VIP receptors are expressed in several tumor types, such as colorectal carcinoma. The study described herein was conducted to confirm the presence of VIP and its receptors (VPAC1 and VPAC2) in surgically resected hepatocellular carcinoma (HCC) tissues and in the HCC cell line Huh7. The mechanism responsible for apoptosis of HCC cells was then examined because VIP treatment (10-10 M) significantly suppressed proliferation of Huh7 cells. In examining apoptosis-related proteins, we found caspase-3 to be significantly increased and Bcl-xL and cyclic AMP (cAMP) response element-binding protein (CREB) to be significantly decreased in Huh7 cells cultured with VIP. Furthermore, the CREB level and phosphorylation were reduced. These effects were reversed by the addition of VIP receptor antagonist or cAMP antagonist Rp-cAMPS. Pretreatment with cAMP analogue blocked the increased apoptosis, suggesting that VIP induces apoptosis via a PKA-independent signaling mechanism. Our data indicate that VIP prevents the progression of HCC by apoptosis through the cAMP/Bcl-xL pathway.
Collapse
Affiliation(s)
- Masaki Hara
- Division of Gastroenterology and Hepatology, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Yuko Takeba
- Department of Pharmacology, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Taroh Iiri
- Department of Pharmacology, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Yuki Ohta
- Department of Pharmacology, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Masanori Ootaki
- Department of Pharmacology, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Minoru Watanabe
- Experimental Animals Institution, St. Marianna University Graduate School of Medicine, Kawasaki, Japan
| | - Daiki Watanabe
- Department of Pharmacology, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Satoshi Koizumi
- Division of Gastroenterological Surgery, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Takehito Otsubo
- Division of Gastroenterological Surgery, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Naoki Matsumoto
- Department of Pharmacology, St. Marianna University School of Medicine, Kawasaki, Japan
| |
Collapse
|
15
|
Li WP, Ma K, Jiang XY, Yang R, Lu PH, Nie BM, Lu Y. Molecular mechanism of panaxydol on promoting axonal growth in PC12 cells. Neural Regen Res 2018; 13:1927-1936. [PMID: 30233066 PMCID: PMC6183029 DOI: 10.4103/1673-5374.239439] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/2018] [Indexed: 12/04/2022] Open
Abstract
Nerve growth factor (NGF) promotes axonal growth in PC12 cells primarily by regulating the RTK-RAS-MEK-ERK pathway. Panaxydol, a polyacetylene isolated from Panax notoginseng, can mimic the effects of NGF. Panaxydol promotes neurite outgrowth in PC12 cells, but its molecular mechanism remains unclear. Indeed, although alkynol compounds such as panaxydol can increase intracellular cyclic adenosine 3',5'-monophosphate (cAMP) levels and the ERK inhibitor U0126 inhibits alkynol-induced axonal growth, how pathways downstream of cAMP activate ERK have not been investigated. This study observed the molecular mechanism of panaxydol-, NGF- and forskolin-induced PC12 cell axon growth using specific signaling pathway inhibitors. The results demonstrated that although the RTK inhibitor SU5416 obviously inhibited the growth-promoting effect of NGF, it could not inhibit the promoting effect of panaxydol on axonal growth of PC12 cells. The adenylate cyclase inhibitor SQ22536 and cAMP-dependent protein kinase inhibitor RpcAMPS could suppress the promoting effect of forskolin and panaxydol on axonal growth. The ERK inhibitor U0126 inhibited axonal growth induced by all three factors. However, the PKA inhibitor H89 inhibited the promoting effect of forskolin on axonal growth but could not suppress the promoting effect of panaxydol. A western blot assay was used to determine the effects of stimulating factors and inhibitors on ERK phosphorylation levels. The results revealed that NGF activates the ERK pathway through tyrosine receptors to induce axonal growth of PC12 cells. In contrast, panaxydol and forskolin increased cellular cAMP levels and were inhibited by adenylyl cyclase inhibitors. The protein kinase A inhibitor H89 completely inhibited forskolin-induced axonal outgrowth and ERK phosphorylation, but could not inhibit panaxydol-induced axonal growth and ERK phosphorylation. These results indicated that panaxydol promoted axonal growth of PC12 cells through different pathways downstream of cAMP. Considering that exchange protein directly activated by cAMP 1 (Epac1) plays an important role in mediating cAMP signaling pathways, RNA interference experiments targeting the Epac1 gene were employed. The results verified that Epac1 could mediate the axonal growth signaling pathway induced by panaxydol. These findings suggest that compared with NGF and forskolin, panaxydol elicits axonal growth through the cAMP-Epac1-Rap1-MEK-ERK-CREB pathway, which is independent of PKA.
Collapse
Affiliation(s)
- Wei-Peng Li
- Department of Nuclear Medicine, the First Affiliated Hospital of Bengbu Medical College, Bengbu, Anhui Province, China
| | - Ke Ma
- Department of Pharmacy, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xiao-Yan Jiang
- Key Laboratory of Arrhythmias of Ministry of Education of China, Tongji University School of Medicine, Shanghai, China
| | - Rui Yang
- Department of Pharmacy, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Pei-Hua Lu
- Department of Pharmacy, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Bao-Ming Nie
- Department of Pharmacy, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yang Lu
- Department of Pharmacy, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| |
Collapse
|
16
|
Meyer zum Büschenfelde U, Brandenstein LI, von Elsner L, Flato K, Holling T, Zenker M, Rosenberger G, Kutsche K. RIT1 controls actin dynamics via complex formation with RAC1/CDC42 and PAK1. PLoS Genet 2018; 14:e1007370. [PMID: 29734338 PMCID: PMC5937737 DOI: 10.1371/journal.pgen.1007370] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 04/18/2018] [Indexed: 12/12/2022] Open
Abstract
RIT1 belongs to the RAS family of small GTPases. Germline and somatic RIT1 mutations have been identified in Noonan syndrome (NS) and cancer, respectively. By using heterologous expression systems and purified recombinant proteins, we identified the p21-activated kinase 1 (PAK1) as novel direct effector of RIT1. We found RIT1 also to directly interact with the RHO GTPases CDC42 and RAC1, both of which are crucial regulators of actin dynamics upstream of PAK1. These interactions are independent of the guanine nucleotide bound to RIT1. Disease-causing RIT1 mutations enhance protein-protein interaction between RIT1 and PAK1, CDC42 or RAC1 and uncouple complex formation from serum and growth factors. We show that the RIT1-PAK1 complex regulates cytoskeletal rearrangements as expression of wild-type RIT1 and its mutant forms resulted in dissolution of stress fibers and reduction of mature paxillin-containing focal adhesions in COS7 cells. This effect was prevented by co-expression of RIT1 with dominant-negative CDC42 or RAC1 and kinase-dead PAK1. By using a transwell migration assay, we show that RIT1 wildtype and the disease-associated variants enhance cell motility. Our work demonstrates a new function for RIT1 in controlling actin dynamics via acting in a signaling module containing PAK1 and RAC1/CDC42, and highlights defects in cell adhesion and migration as possible disease mechanism underlying NS. Noonan syndrome (NS) belongs to the RASopathies, a group of developmental diseases caused by mutations in genes encoding RAS-MAPK pathway components. Germline mutations in RIT1 have been identified in NS. RIT1 belongs to the RAS superfamily, however, the cellular function of RIT1 remains elusive. We show that RIT1 binds p21-activated kinase 1 (PAK1), an effector of the RHO GTPases RAC1 and CDC42, which are important regulators of cytoskeletal dynamics. NS-associated RIT1 mutants enhance complex formation between RIT1, RAC1/CDC42 and PAK1. Expression of wild-type or mutant forms of RIT1 caused loss of stress fibers and mature focal adhesions and enhanced cell motility. Our data suggest that dysfunction in actin dynamics is a novel aspect in the pathophysiology of RASopathies.
Collapse
Affiliation(s)
| | | | - Leonie von Elsner
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Kristina Flato
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Tess Holling
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Martin Zenker
- Institute of Human Genetics, University Hospital Magdeburg, Magdeburg, Germany
| | - Georg Rosenberger
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- * E-mail: (KK); (GR)
| | - Kerstin Kutsche
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- * E-mail: (KK); (GR)
| |
Collapse
|
17
|
Robichaux WG, Cheng X. Intracellular cAMP Sensor EPAC: Physiology, Pathophysiology, and Therapeutics Development. Physiol Rev 2018; 98:919-1053. [PMID: 29537337 PMCID: PMC6050347 DOI: 10.1152/physrev.00025.2017] [Citation(s) in RCA: 141] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 09/05/2017] [Accepted: 09/06/2017] [Indexed: 12/13/2022] Open
Abstract
This review focuses on one family of the known cAMP receptors, the exchange proteins directly activated by cAMP (EPACs), also known as the cAMP-regulated guanine nucleotide exchange factors (cAMP-GEFs). Although EPAC proteins are fairly new additions to the growing list of cAMP effectors, and relatively "young" in the cAMP discovery timeline, the significance of an EPAC presence in different cell systems is extraordinary. The study of EPACs has considerably expanded the diversity and adaptive nature of cAMP signaling associated with numerous physiological and pathophysiological responses. This review comprehensively covers EPAC protein functions at the molecular, cellular, physiological, and pathophysiological levels; and in turn, the applications of employing EPAC-based biosensors as detection tools for dissecting cAMP signaling and the implications for targeting EPAC proteins for therapeutic development are also discussed.
Collapse
Affiliation(s)
- William G Robichaux
- Department of Integrative Biology and Pharmacology, Texas Therapeutics Institute, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center , Houston, Texas
| | - Xiaodong Cheng
- Department of Integrative Biology and Pharmacology, Texas Therapeutics Institute, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center , Houston, Texas
| |
Collapse
|
18
|
Pituitary adenylate cyclase activating polypeptide induces long-term, transcription-dependent plasticity and remodeling at autonomic synapses. Mol Cell Neurosci 2017; 85:170-182. [DOI: 10.1016/j.mcn.2017.10.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 09/19/2017] [Accepted: 10/06/2017] [Indexed: 12/28/2022] Open
|
19
|
Sundrum T, Walker CS. Pituitary adenylate cyclase-activating polypeptide receptors in the trigeminovascular system: implications for migraine. Br J Pharmacol 2017; 175:4109-4120. [PMID: 28977676 DOI: 10.1111/bph.14053] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2017] [Revised: 08/24/2017] [Accepted: 09/11/2017] [Indexed: 12/13/2022] Open
Abstract
The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) has been implicated in a wide range of functions including vasodilatation, neuroprotection, nociception and neurogenic inflammation. PACAP activates three distinct receptors, the PAC1 receptor, which responds to PACAP, and the VPAC1 and VPAC2 receptors, which respond to both PACAP and vasoactive intestinal polypeptide. The trigeminovascular system plays a key role in migraine and contains the trigeminal nerve, which is the major conduit of craniofacial pain. PACAP is expressed throughout the trigeminovascular system and in higher brain regions involved in processing pain. Evidence from human clinical studies suggests that PACAP may act outside the blood-brain barrier in the pathogenesis of migraine. However, the precise mechanisms involved remain unclear. PACAP potentially induces migraine attacks by activating different receptors in different cell types and tissues. This complexity prompted this review of PACAP receptor pharmacology, expression and function in the trigeminovascular system. Current evidence suggests that the PAC1 receptor is the likely pathophysiological target of PACAP in migraine. However, multiple PACAP receptors are expressed in key parts of the trigeminovascular system and further work is required to determine their contribution to PACAP physiology and the pathology of migraine. LINKED ARTICLES This article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.21/issuetoc.
Collapse
Affiliation(s)
- Tahlia Sundrum
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Christopher S Walker
- School of Biological Sciences, University of Auckland, Auckland, New Zealand.,Maurice Wilkins Centre and Centre for Brain Research, University of Auckland, Auckland, New Zealand
| |
Collapse
|
20
|
Emery AC, Xu W, Eiden MV, Eiden LE. Guanine nucleotide exchange factor Epac2-dependent activation of the GTP-binding protein Rap2A mediates cAMP-dependent growth arrest in neuroendocrine cells. J Biol Chem 2017; 292:12220-12231. [PMID: 28546426 DOI: 10.1074/jbc.m117.790329] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 05/23/2017] [Indexed: 11/06/2022] Open
Abstract
First messenger-dependent activation of MAP kinases in neuronal and endocrine cells is critical for cell differentiation and function and requires guanine nucleotide exchange factor (GEF)-mediated activation of downstream Ras family small GTPases, which ultimately lead to ERK, JNK, and p38 phosphorylation. Because there are numerous GEFs and also a host of Ras family small GTPases, it is important to know which specific GEF-small GTPase dyad functions in a given cellular process. Here we investigated the upstream activators and downstream effectors of signaling via the GEF Epac2 in the neuroendocrine NS-1 cell line. Three cAMP sensors, Epac2, PKA, and neuritogenic cAMP sensor-Rapgef2, mediate distinct cellular outputs: p38-dependent growth arrest, cAMP response element-binding protein-dependent cell survival, and ERK-dependent neuritogenesis, respectively, in these cells. Previously, we found that cAMP-induced growth arrest of PC12 and NS-1 cells requires Epac2-dependent activation of p38 MAP kinase, which posed the important question of how Epac2 engages p38 without simultaneously activating other MAP kinases in neuronal and endocrine cells. We now show that the small GTP-binding protein Rap2A is the obligate effector for, and GEF substrate of, Epac2 in mediating growth arrest through p38 activation in NS-1 cells. This new pathway is distinctly parcellated from the G protein-coupled receptor → Gs → adenylate cyclase → cAMP → PKA → cAMP response element-binding protein pathway mediating cell survival and the G protein-coupled receptor → Gs → adenylate cyclase → cAMP → neuritogenic cAMP sensor-Rapgef2 → B-Raf → MEK → ERK pathway mediating neuritogenesis in NS-1 cells.
Collapse
Affiliation(s)
- Andrew C Emery
- Section on Molecular Neuroscience, National Institute of Mental Health Intramural Research Program, Bethesda, Maryland 20892
| | - Wenqin Xu
- Section on Molecular Neuroscience, National Institute of Mental Health Intramural Research Program, Bethesda, Maryland 20892
| | - Maribeth V Eiden
- Office of the Scientific Director, National Institute of Mental Health Intramural Research Program, Bethesda, Maryland 20892
| | - Lee E Eiden
- Section on Molecular Neuroscience, National Institute of Mental Health Intramural Research Program, Bethesda, Maryland 20892.
| |
Collapse
|
21
|
Sukhanova IF, Kozhevnikova LM, Mironova GY, Avdonin PV. The Epac protein inhibitor ESI-09 eliminates the tonic phase of aorta contraction induced by endogenic vasoconstrictors in rats. BIOL BULL+ 2017. [DOI: 10.1134/s1062359017020200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
22
|
Muñoz-Llancao P, de Gregorio C, Las Heras M, Meinohl C, Noorman K, Boddeke E, Cheng X, Lezoualc'h F, Schmidt M, Gonzalez-Billault C. Microtubule-regulating proteins and cAMP-dependent signaling in neuroblastoma differentiation. Cytoskeleton (Hoboken) 2017; 74:143-158. [PMID: 28164467 DOI: 10.1002/cm.21355] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 01/26/2017] [Accepted: 01/31/2017] [Indexed: 01/15/2023]
Abstract
Neurons are highly differentiated cells responsible for the conduction and transmission of information in the nervous system. The proper function of a neuron relies on the compartmentalization of their intracellular domains. Differentiated neuroblastoma cells have been extensively used to study and understand the physiology and cell biology of neuronal cells. Here, we show that differentiation of N1E-115 neuroblastoma cells is more pronounced upon exposure of a chemical analog of cyclic AMP (cAMP), db-cAMP. We next analysed the expression of key microtubule-regulating proteins in differentiated cells and the expression and activation of key cAMP players such as EPAC, PKA and AKAP79/150. Most of the microtubule-promoting factors were up regulated during differentiation of N1E-115 cells, while microtubule-destabilizing proteins were down regulated. We observed an increase in tubulin post-translational modifications related to microtubule stability. As expected, db-cAMP increased PKA- and EPAC-dependent signalling. Consistently, pharmacological modulation of EPAC activity instructed cell differentiation, number of neurites, and neurite length in N1E-115 cells. Moreover, disruption of the PKA-AKAP interaction reduced these morphometric parameters. Interestingly, PKA and EPAC act synergistically to induce neuronal differentiation in N1E-115. Altogether these results show that the changes observed in the differentiation of N1E-115 cells proceed by regulating several microtubule-stabilizing factors, and the acquisition of a neuronal phenotype is a process involving concerted although independent functions of EPAC and PKA.
Collapse
Affiliation(s)
- Pablo Muñoz-Llancao
- Laboratory of Cell and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile.,Department of Molecular Pharmacology, University of Groningen, The Netherlands
| | - Cristian de Gregorio
- Laboratory of Cell and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile
| | - Macarena Las Heras
- Laboratory of Cell and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile.,Geroscience Center for Brain Health and Metabolism (GERO), Santiago, Chile
| | - Christopher Meinohl
- Department of Molecular Pharmacology, University of Groningen, The Netherlands
| | - Kevin Noorman
- Department of Molecular Pharmacology, University of Groningen, The Netherlands
| | - Erik Boddeke
- Department of Medical Physiology, University Medical Center Groningen, University of Groningen, The Netherlands
| | - Xiaodong Cheng
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center, Houston, USA
| | - Frank Lezoualc'h
- Inserm UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Toulouse, France.,Université de Toulouse III, Paul Sabatier, Toulouse, France
| | - Martina Schmidt
- Department of Molecular Pharmacology, University of Groningen, The Netherlands
| | - Christian Gonzalez-Billault
- Laboratory of Cell and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile.,Geroscience Center for Brain Health and Metabolism (GERO), Santiago, Chile.,The Buck Institute for Research on Aging, Novato, USA
| |
Collapse
|
23
|
Baameur F, Singhmar P, Zhou Y, Hancock JF, Cheng X, Heijnen CJ, Kavelaars A. Epac1 interacts with importin β1 and controls neurite outgrowth independently of cAMP and Rap1. Sci Rep 2016; 6:36370. [PMID: 27808165 PMCID: PMC5093460 DOI: 10.1038/srep36370] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 10/14/2016] [Indexed: 01/23/2023] Open
Abstract
Exchange protein directly activated by cAMP-1 (Epac1) is a cAMP sensor that regulates multiple cellular functions including cellular migration, proliferation and differentiation. Classically, Epac1 is thought to exert its effects through binding of cAMP leading to a conformational change in Epac1 and its accumulation at the plasma membrane (PM) where it activates Rap1. In search for regulators of Epac1 activity, we show here that importin β1 (impβ1) is an Epac1 binding partner that prevents PM accumulation of Epac1. We demonstrate that in the absence of impβ1, endogenous as well as overexpressed Epac1 accumulate at the PM. Moreover, agonist-induced PM translocation of Epac1 leads to dissociation of Epac1 from impβ1. Localization of Epac1 at the PM in the absence of impβ1, requires residue R82 in its DEP domain. Notably, the PM accumulation of Epac1 in the absence of impβ1 does not require binding of cAMP to Epac1 and does not result in Rap1 activation. Functionally, PM accumulation of Epac1, an Epac1 mutant deficient in cAMP binding, or an Epac1 mutant tethered to the PM, is sufficient to inhibit neurite outgrowth. In conclusion, we uncover a cAMP-independent function of Epac1 at the PM and demonstrate that impβ1 controls subcellular localization of Epac1.
Collapse
Affiliation(s)
- Faiza Baameur
- Laboratory of Neuroimmunology, Department of Symptom Research, Division of Internal Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Pooja Singhmar
- Laboratory of Neuroimmunology, Department of Symptom Research, Division of Internal Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Yong Zhou
- Department of Integrative Biology and Pharmacology and Texas Therapeutics Institute, The University of Texas Health Science Center, Houston, TX 77030, USA
| | - John F Hancock
- Department of Integrative Biology and Pharmacology and Texas Therapeutics Institute, The University of Texas Health Science Center, Houston, TX 77030, USA
| | - Xiaodong Cheng
- Department of Integrative Biology and Pharmacology and Texas Therapeutics Institute, The University of Texas Health Science Center, Houston, TX 77030, USA
| | - Cobi J Heijnen
- Laboratory of Neuroimmunology, Department of Symptom Research, Division of Internal Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Annemieke Kavelaars
- Laboratory of Neuroimmunology, Department of Symptom Research, Division of Internal Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| |
Collapse
|
24
|
Zhou L, Ma SL, Yeung PKK, Wong YH, Tsim KWK, So KF, Lam LCW, Chung SK. Anxiety and depression with neurogenesis defects in exchange protein directly activated by cAMP 2-deficient mice are ameliorated by a selective serotonin reuptake inhibitor, Prozac. Transl Psychiatry 2016; 6:e881. [PMID: 27598965 PMCID: PMC5048194 DOI: 10.1038/tp.2016.129] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 05/03/2016] [Accepted: 05/05/2016] [Indexed: 01/29/2023] Open
Abstract
Intracellular cAMP and serotonin are important modulators of anxiety and depression. Fluoxetine, a selective serotonin reuptake inhibitor (SSRI) also known as Prozac, is widely used against depression, potentially by activating cAMP response element-binding protein (CREB) and increasing brain-derived neurotrophic factor (BDNF) through protein kinase A (PKA). However, the role of Epac1 and Epac2 (Rap guanine nucleotide exchange factors, RAPGEF3 and RAPGEF4, respectively) as potential downstream targets of SSRI/cAMP in mood regulations is not yet clear. Here, we investigated the phenotypes of Epac1 (Epac1(-/-)) or Epac2 (Epac2(-/-)) knockout mice by comparing them with their wild-type counterparts. Surprisingly, Epac2(-/-) mice exhibited a wide range of mood disorders, including anxiety and depression with learning and memory deficits in contextual and cued fear-conditioning tests without affecting Epac1 expression or PKA activity. Interestingly, rs17746510, one of the three single-nucleotide polymorphisms (SNPs) in RAPGEF4 associated with cognitive decline in Chinese Alzheimer's disease (AD) patients, was significantly correlated with apathy and mood disturbance, whereas no significant association was observed between RAPGEF3 SNPs and the risk of AD or neuropsychiatric inventory scores. To further determine the detailed role of Epac2 in SSRI/serotonin/cAMP-involved mood disorders, we treated Epac2(-/-) mice with a SSRI, Prozac. The alteration in open field behavior and impaired hippocampal cell proliferation in Epac2(-/-) mice were alleviated by Prozac. Taken together, Epac2 gene polymorphism is a putative risk factor for mood disorders in AD patients in part by affecting the hippocampal neurogenesis.
Collapse
Affiliation(s)
- L Zhou
- School of Biomedical Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - S L Ma
- Department of Psychiatry, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
| | - P K K Yeung
- School of Biomedical Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR, China,State Key Laboratory of Pharmaceutical Biotechnology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Y H Wong
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China,State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China
| | - K W K Tsim
- State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China,Division of Life Science and Center for Chinese Medicine, Hong Kong University of Science and Technology, Clear Water Bay, Clear Water Bay, Hong Kong SAR, China
| | - K F So
- School of Biomedical Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR, China,Research Center of Heart, Brain, Hormone and Healthy Aging, The University of Hong Kong, Pokfulam, Hong Kong SAR, China,State Key Laboratory of Brain and Cognitive Science, The University of Hong Kong, Pokfulam, Hong Kong SAR, China,Department of Ophthalmology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - L C W Lam
- Department of Psychiatry, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
| | - S K Chung
- School of Biomedical Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR, China,State Key Laboratory of Pharmaceutical Biotechnology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China,Research Center of Heart, Brain, Hormone and Healthy Aging, The University of Hong Kong, Pokfulam, Hong Kong SAR, China,School of Biomedical Sciences, The University of Hong Kong, 1/F, Laboratory Block, Faculty of Medicine Building, 21 Sassoon Road, Pokfulam, Hong Kong SAR, China. E-mail:
| |
Collapse
|
25
|
Activation of MEK/ERK Signaling by PACAP in Guinea Pig Cardiac Neurons. J Mol Neurosci 2016; 59:309-16. [PMID: 27194157 DOI: 10.1007/s12031-016-0766-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 04/29/2016] [Indexed: 10/21/2022]
Abstract
Pituitary adenylate cyclase-activating polypeptide (PACAP) signaling can increase guinea pig cardiac neuron excitability in part through extracellular signal-regulated kinase (ERK) activation. The present study examined the PACAP receptors and signaling cascades that stimulate guinea pig cardiac neuron ERK signaling using confocal microscopy to quantify PACAP-induced neuronal phosphorylated ERK (pERK) immunoreactivity. PACAP and maxadilan, but not vasoactive intestinal polypeptide (VIP), increased cardiac neuron pERK, implicating primary roles for PACAP-selective PAC1 receptor (Adcyap1r1) signaling rather than VPAC receptors (Vipr1 and Vipr2) in the generation of cardiac neuron pERK. The adenylyl cyclase (AC) activator forskolin, but not the protein kinase C (PKC) activator phorbol myristate acetate (PMA), increased pERK. Also, Bim1 did not blunt PACAP activation of pERK. Together, the results suggest PAC1 receptor signal transduction via Gs/adenylyl cyclase (AC)/cAMP rather than Gq/phospholipase C (PLC) generated neuronal pERK. Activator and inhibitor studies suggested that the PACAP-mediated pERK activation was PKA-dependent rather than an exchange protein directly activated by a cAMP (EPAC), PKA-independent mechanism. The PACAP-induced pERK was inhibited by the clathrin inhibitor Pitstop2 to block receptor internalization and endosomal signaling. We propose that the PACAP-mediated MEK/ERK activation in cardiac neurons involves both AC/cAMP/PKA signaling and PAC1 receptor internalization/activation of signaling endosomes.
Collapse
|
26
|
Fang Z, Marshall CB, Yin JC, Mazhab-Jafari MT, Gasmi-Seabrook GMC, Smith MJ, Nishikawa T, Xu Y, Neel BG, Ikura M. Biochemical Classification of Disease-associated Mutants of RAS-like Protein Expressed in Many Tissues (RIT1). J Biol Chem 2016; 291:15641-52. [PMID: 27226556 DOI: 10.1074/jbc.m116.714196] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Indexed: 01/09/2023] Open
Abstract
RAS-like protein expressed in many tissues 1 (RIT1) is a disease-associated RAS subfamily small guanosine triphosphatase (GTPase). Recent studies revealed that germ-line and somatic RIT1 mutations can cause Noonan syndrome (NS), and drive proliferation of lung adenocarcinomas, respectively, akin to RAS mutations in these diseases. However, the locations of these RIT1 mutations differ significantly from those found in RAS, and do not affect the three mutational "hot spots" of RAS. Moreover, few studies have characterized the GTPase cycle of RIT1 and its disease-associated mutants. Here we developed a real-time NMR-based GTPase assay for RIT1 and investigated the effect of disease-associated mutations on GTPase cycle. RIT1 exhibits an intrinsic GTP hydrolysis rate similar to that of H-RAS, but its intrinsic nucleotide exchange rate is ∼4-fold faster, likely as a result of divergent residues near the nucleotide binding site. All of the disease-associated mutations investigated increased the GTP-loaded, activated state of RIT1 in vitro, but they could be classified into two groups with different intrinsic GTPase properties. The S35T, A57G, and Y89H mutants exhibited more rapid nucleotide exchange, whereas F82V and T83P impaired GTP hydrolysis. A RAS-binding domain pulldown assay indicated that RIT1 A57G and Y89H were highly activated in HEK293T cells, whereas T83P and F82V exhibited more modest activation. All five mutations are associated with NS, whereas two (A57G and F82V) have also been identified in urinary tract cancers and myeloid malignancies. Characterization of the effects on the GTPase cycle of RIT1 disease-associated mutations should enable better understanding of their role in disease processes.
Collapse
Affiliation(s)
- Zhenhao Fang
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Christopher B Marshall
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Jiani C Yin
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Mohammad T Mazhab-Jafari
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Geneviève M C Gasmi-Seabrook
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Matthew J Smith
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Tadateru Nishikawa
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Yang Xu
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Benjamin G Neel
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Mitsuhiko Ikura
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| |
Collapse
|
27
|
Zhou Z, Tanaka KF, Matsunaga S, Iseki M, Watanabe M, Matsuki N, Ikegaya Y, Koyama R. Photoactivated adenylyl cyclase (PAC) reveals novel mechanisms underlying cAMP-dependent axonal morphogenesis. Sci Rep 2016; 5:19679. [PMID: 26795422 PMCID: PMC4726437 DOI: 10.1038/srep19679] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 12/16/2015] [Indexed: 01/17/2023] Open
Abstract
Spatiotemporal regulation of axonal branching and elongation is essential in the development of refined neural circuits. cAMP is a key regulator of axonal growth; however, whether and how intracellular cAMP regulates axonal branching and elongation remain unclear, mainly because tools to spatiotemporally manipulate intracellular cAMP levels have been lacking. To overcome this issue, we utilized photoactivated adenylyl cyclase (PAC), which produces cAMP in response to blue-light exposure. In primary cultures of dentate granule cells transfected with PAC, short-term elevation of intracellular cAMP levels induced axonal branching but not elongation, whereas long-term cAMP elevation induced both axonal branching and elongation. The temporal dynamics of intracellular cAMP levels regulated axonal branching and elongation through the activation of protein kinase A (PKA) and exchange protein directly activated by cAMP (Epac), respectively. Thus, using PAC, our study for the first time reveals that temporal cAMP dynamics could regulate axonal branching and elongation via different signaling pathways.
Collapse
Affiliation(s)
- Zhiwen Zhou
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
| | - Kenji F Tanaka
- Department of Neuropsychiatry, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo, Japan
| | - Shigeru Matsunaga
- Central Research Laboratory, Hamamatsu Photonics K.K., 5000 Hirakuchi Hamakita-ku, Hamamatsu, Shizuoka, Japan
| | - Mineo Iseki
- Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi, Chiba, Japan
| | - Masakatsu Watanabe
- The Graduate School for the Creation of New Photonics Industries, 1955-1 Kurematsu-cho, Nishiku, Hamamatsu, Shizuoka, Japan
| | - Norio Matsuki
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
| | - Yuji Ikegaya
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
| | - Ryuta Koyama
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
| |
Collapse
|
28
|
Exchange Protein Directly Activated by cAMP (EPAC) Regulates Neuronal Polarization through Rap1B. J Neurosci 2015; 35:11315-29. [PMID: 26269639 DOI: 10.1523/jneurosci.3645-14.2015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
UNLABELLED Acquisition of neuronal polarity is a complex process involving cellular and molecular events. The second messenger cAMP is involved in axonal specification through activation of protein kinase A. However, an alternative cAMP-dependent mechanism involves the exchange protein directly activated by cAMP (EPAC), which also responds to physiological changes in cAMP concentration, promoting activation of the small Rap GTPases. Here, we present evidence that EPAC signaling contributes to axon specification and elongation. In primary rat hippocampal neurons, EPAC isoforms were expressed differentially during axon specification. Furthermore, 8-pCPT, an EPAC pharmacological activator, and genetic manipulations of EPAC in neurons induced supernumerary axons indicative of Rap1b activation. Moreover, 8-pCPT-treated neurons expressed ankyrin G and other markers of mature axons such as synaptophysin and axonal accumulation of vGLUT1. In contrast, pharmacological inhibition of EPAC delayed neuronal polarity. Genetic manipulations to inactivate EPAC1 using either shRNA or neurons derived from EPAC1 knock-out (KO) mice led to axon elongation and polarization defects. Interestingly, multiaxonic neurons generated by 8-pCPT treatments in wild-type neurons were not found in EPAC1 KO mice neurons. Altogether, these results propose that EPAC signaling is an alternative and complementary mechanism for cAMP-dependent axon determination. SIGNIFICANCE STATEMENT This study identifies the guanine exchange factor responsible for Rap1b activation during neuronal polarization and provides an alternate explanation for cAMP-dependent acquisition of neuronal polarity.
Collapse
|
29
|
Blirando K, Blaise R, Gorodnaya N, Rouxel C, Meilhac O, Vincent P, Limon I. The stellate vascular smooth muscle cell phenotype is induced by IL-1β via the secretion of PGE2 and subsequent cAMP-dependent protein kinase A activation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:3235-47. [PMID: 26403276 DOI: 10.1016/j.bbamcr.2015.09.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 09/11/2015] [Accepted: 09/14/2015] [Indexed: 12/12/2022]
Abstract
Atherosclerosis development is associated with morphological changes to intimal cells, leading to a stellate cell phenotype. In this study, we aimed to determine whether and how key pro-atherogenic cytokines present in atherosclerotic plaques (IL-1β, TNFα and IFNγ) could induce this phenotype, as these molecules are known to trigger the transdifferentiation of vascular smooth muscle cells (VSMCs). We found that, IL-1β was the only major inflammatory mediator tested capable of inducing a stellate morphology in VSMCs. This finding was confirmed by staining for F-actin and vinculin at focal adhesions, as these two markers were disrupted only by IL-1β. We then investigated the possible association of this IL-1β-dependent change in morphology with an increase in intracellular cAMP concentration ([cAMP]), using the FRET-based biosensor for cAMP (T)Epac(VV). Experiments in the presence of IL-1β or medium conditioned by IL-1β-treated VSMCs and pharmacological tools demonstrated that the long-term increase in intracellular cAMP concentration was induced by the secretion of an autocrine/paracrine mediator, prostaglandin E₂(PGE₂), acting through the EP4 receptor. Finally, by knocking down the expression of the regulatory subunit PKAR1α, thereby reproducing the effects of IL-1β and PGE₂ on VSMCs, we demonstrated the contribution of PKA activity to the observed behavior of VSMCs.
Collapse
Affiliation(s)
- Karl Blirando
- Sorbonne Universités, UPMC Univ Paris 06CNRS UMR 8256 B2A, IBPS, F-75005, Paris, France
| | - Régis Blaise
- Sorbonne Universités, UPMC Univ Paris 06CNRS UMR 8256 B2A, IBPS, F-75005, Paris, France
| | - Natalia Gorodnaya
- Sorbonne Universités, UPMC Univ Paris 06CNRS UMR 8256 B2A, IBPS, F-75005, Paris, France
| | - Clotilde Rouxel
- Sorbonne Universités, UPMC Univ Paris 06CNRS UMR 8256 B2A, IBPS, F-75005, Paris, France
| | - Olivier Meilhac
- Inserm U1188 Diabète Athérothrombose Thérapies Réunion Océan Indien (DéTROI) CYROI, 2, rue Maxime Rivière, 97490 Sainte Clotilde, La Réunion, France
| | - Pierre Vincent
- Sorbonne Universités, UPMC Univ Paris 06CNRS UMR 8256 B2A, IBPS, F-75005, Paris, France
| | - Isabelle Limon
- Sorbonne Universités, UPMC Univ Paris 06CNRS UMR 8256 B2A, IBPS, F-75005, Paris, France.
| |
Collapse
|
30
|
Mohan S, Narumiya S, Doré S. Neuroprotective role of prostaglandin PGE2 EP2 receptor in hemin-mediated toxicity. Neurotoxicology 2015; 46:53-9. [PMID: 25451967 PMCID: PMC4681391 DOI: 10.1016/j.neuro.2014.10.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 10/18/2014] [Accepted: 10/23/2014] [Indexed: 01/01/2023]
Abstract
Heme (Fe(2+) protoporphyrin IX) and hemin (Fe(3+)), the prosthetic group of hemoprotein, are cytotoxic due to their ability to contribute to the production of reactive oxygen species, increased intracellular calcium levels, and stimulate glutamate-mediated excitotoxicity. Previous work by our group showed that blockade of the prostaglandin E2 (PGE2)-EP1 receptor reduced hemin-induced cytotoxicity in primary cortical neuronal cultures. However, the role of the prostaglandin E2 (PGE2)-EP2 receptor in hemin neurotoxicity remains unclear. Activation of the EP2 receptor in neurons results in increased cyclic AMP (cAMP) and protein kinase A signaling; therefore, we hypothesized that the activation of the EP2 receptor decreases hemin neurotoxicity. Using postnatal primary cortical neurons cultured from wildtype-control (WT) and EP2(-/-) mice, we investigated the role of the EP2 receptor in hemin neurotoxicity by monitoring cell survival with the Calcein-AM live-cell and lactate dehydrogenase assays. MitoTracker staining was also performed to determine how mitochondria were affected by hemin. Hemin neurotoxicity in EP2(-/-) neurons was 37.2 ± 17.0% greater compared to WT neurons. Of interest, cotreatment with the EP2 receptor agonist, butaprost (1 and 10 μM), significantly attenuated hemin neurotoxicity by 55.7 ± 21.1% and 60.1 ± 14.8%, respectively. To further investigate signaling mechanisms related to EP2 receptor mediating cytoprotection, neurons were cotreated with hemin and activators/inhibitors of both the cAMP-protein kinase A/exchange protein directly activated by cAMP (Epac) pathways. Forskolin, a cAMP activator, and 8-pCPT-cAMP, an Epac activator, both attenuated hemin neurotoxicity by 78.8 ± 22.2% and 58.4 ± 9.8%, respectively, as measured using the lactate dehydrogenase assay. Together, the results reveal that activation of the EP2 receptor is protective against hemin neurotoxicity in vitro and these findings suggest that neuroprotection occurs through the cAMP-Epac pathway in neuronal cultures. Therefore, activation of the EP2 receptor could be used to minimize neuronal damage following exposure to supraphysiological levels of hemin.
Collapse
MESH Headings
- Adjuvants, Immunologic/pharmacology
- Alprostadil/analogs & derivatives
- Alprostadil/pharmacology
- Analysis of Variance
- Animals
- Animals, Newborn
- Cell Survival/drug effects
- Cerebral Cortex/cytology
- Colforsin/pharmacology
- Cyclic AMP/analogs & derivatives
- Cyclic AMP/pharmacology
- Dose-Response Relationship, Drug
- Excitatory Amino Acid Agonists/pharmacology
- Glutamic Acid/pharmacology
- Hemin/toxicity
- L-Lactate Dehydrogenase/metabolism
- Mice
- Mice, Knockout
- Neurons/drug effects
- Neuroprotective Agents/pharmacology
- Receptors, Prostaglandin E, EP2 Subtype/agonists
- Receptors, Prostaglandin E, EP2 Subtype/genetics
- Receptors, Prostaglandin E, EP2 Subtype/metabolism
- Thionucleotides/pharmacology
Collapse
Affiliation(s)
- Shekher Mohan
- Department of Anesthesiology, University of Florida, Gainesville, FL, USA
| | - Shuh Narumiya
- Department of Pharmacology, Kyoto University, Kyoto, Japan
| | - Sylvain Doré
- Department of Anesthesiology, University of Florida, Gainesville, FL, USA; Departments of Neurology, Psychiatry, and Neuroscience, University of Florida, Gainesville, FL, USA.
| |
Collapse
|
31
|
Abstract
The Rit subfamily of GTPases is a founding branch within the Ras family of small G-proteins and preserves unique sequences in the G2 effector loop domain and the C-terminus. Rit proteins regulate a diversity of signal transduction pathways, some of which are similar to and others of which differ from the pathways that are regulated by other Ras family GTPases. Rit proteins have been demonstrated to be essential regulators in neuronal differentiation and survival. Here, we describe the materials and methods utilized to characterize cellular signaling for the Rit subfamily of G-proteins in neuronal differentiation and survival.
Collapse
|
32
|
Vitali E, Peverelli E, Giardino E, Locatelli M, Lasio GB, Beck-Peccoz P, Spada A, Lania AG, Mantovani G. Cyclic adenosine 3'-5'-monophosphate (cAMP) exerts proliferative and anti-proliferative effects in pituitary cells of different types by activating both cAMP-dependent protein kinase A (PKA) and exchange proteins directly activated by cAMP (Epac). Mol Cell Endocrinol 2014; 383:193-202. [PMID: 24373949 DOI: 10.1016/j.mce.2013.12.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 12/05/2013] [Accepted: 12/06/2013] [Indexed: 10/25/2022]
Abstract
In the pituitary the activation of cyclic adenosine 3'-5'-monophosphate (cAMP) dependent pathways generates proliferative signals in somatotrophs, whereas in pituitary cells of other lineages its effect remains uncertain. Moreover, the specific role of the two main cAMP effectors, protein kinase A (PKA) and exchange proteins directly activated by cAMP (Epac), has not been defined. Aim of this study was to investigate the effect of cAMP on pituitary adenomatous cells proliferation and to identify PKA and Epac differential involvement. We found that cAMP increased DNA synthesis and cyclin D1 expression in somatotropinomas, whereas it reduced both parameters in prolactinomas and nonfunctioning adenomas, these effects being replicated in corresponding cell lines. Moreover, the divergent cAMP effects were mimicked by Epac and PKA analogs, which activated Rap1 and CREB, respectively. In conclusion, we demonstrated that cAMP exerted opposite effects on different pituitary cell types proliferation, these effects being mediated by both Epac and PKA.
Collapse
Affiliation(s)
- E Vitali
- Endocrine Unit, Department of Clinical Sciences and Community Health, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Italy
| | - E Peverelli
- Endocrine Unit, Department of Clinical Sciences and Community Health, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Italy
| | - E Giardino
- Endocrine Unit, Department of Clinical Sciences and Community Health, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Italy
| | - M Locatelli
- Neurosurgery Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - G B Lasio
- Neurosurgery Unit, IRCCS Humanitas Clinical Institute, Rozzano, Italy
| | - P Beck-Peccoz
- Endocrine Unit, Department of Clinical Sciences and Community Health, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Italy
| | - A Spada
- Endocrine Unit, Department of Clinical Sciences and Community Health, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Italy
| | - A G Lania
- Endocrine Unit, IRCCS Humanitas Clinical Institute, University of Milan, Rozzano, Italy.
| | - G Mantovani
- Endocrine Unit, Department of Clinical Sciences and Community Health, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Italy
| |
Collapse
|
33
|
Emery AC, Eiden MV, Eiden LE. Separate cyclic AMP sensors for neuritogenesis, growth arrest, and survival of neuroendocrine cells. J Biol Chem 2014; 289:10126-39. [PMID: 24567337 DOI: 10.1074/jbc.m113.529321] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dividing neuroendocrine cells differentiate into a neuronal-like phenotype in response to ligands activating G protein-coupled receptors, leading to the elevation of the second messenger cAMP. Growth factors that act at receptor tyrosine kinases, such as nerve growth factor, also cause differentiation. We report here that two aspects of cAMP-induced differentiation, neurite extension and growth arrest, are dissociable at the level of the sensors conveying the cAMP signal in PC12 and NS-1 cells. Following cAMP elevation, neuritogenic cyclic AMP sensor/Rapgef2 is activated for signaling to ERK to mediate neuritogenesis, whereas Epac2 is activated for signaling to the MAP kinase p38 to mediate growth arrest. Neither action of cAMP requires transactivation of TrkA, the receptor for NGF. In fact, the differentiating effects of NGF do not require activation of any of the cAMP sensors protein kinase A, Epac, or neuritogenic cyclic AMP sensor/Rapgef2 but, rather, depend on ERK and p38 activation via completely independent signaling pathways. Hence, cAMP- and NGF-dependent signaling for differentiation are also completely insulated from each other. Cyclic AMP and NGF also protect NS-1 cells from serum withdrawal-induced cell death, again by two wholly separate signaling mechanisms, PKA-dependent for cAMP and PKA-independent for NGF.
Collapse
|
34
|
Berger AH, Imielinski M, Duke F, Wala J, Kaplan N, Shi GX, Andres DA, Meyerson M. Oncogenic RIT1 mutations in lung adenocarcinoma. Oncogene 2014; 33:4418-23. [PMID: 24469055 PMCID: PMC4150988 DOI: 10.1038/onc.2013.581] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 11/25/2013] [Accepted: 12/03/2013] [Indexed: 12/27/2022]
Abstract
Lung adenocarcinoma is comprised of distinct mutational subtypes characterized by mutually exclusive oncogenic mutations in RTK/RAS pathway members KRAS, EGFR, BRAF and ERBB2, and translocations involving ALK, RET and ROS1. Identification of these oncogenic events has transformed the treatment of lung adenocarcinoma via application of therapies targeted toward specific genetic lesions in stratified patient populations. However, such mutations have been reported in only ∼55% of lung adenocarcinoma cases in the United States, suggesting other mechanisms of malignancy are involved in the remaining cases. Here we report somatic mutations in the small GTPase gene RIT1 in ∼2% of lung adenocarcinoma cases that cluster in a hotspot near the switch II domain of the protein. RIT1 switch II domain mutations are mutually exclusive with all other known lung adenocarcinoma driver mutations. Ectopic expression of mutated RIT1 induces cellular transformation in vitro and in vivo, which can be reversed by combined PI3K and MEK inhibition. These data identify RIT1 as a driver oncogene in a specific subset of lung adenocarcinomas and suggest PI3K and MEK inhibition as a potential therapeutic strategy in RIT1-mutated tumors.
Collapse
Affiliation(s)
- A H Berger
- 1] Cancer Program, The Broad Institute of Harvard and M.I.T., 7 Cambridge Center, Cambridge, MA, USA [2] Department of Medical Oncology, Dana Farber Cancer Institute, Boston, MA, USA
| | - M Imielinski
- 1] Cancer Program, The Broad Institute of Harvard and M.I.T., 7 Cambridge Center, Cambridge, MA, USA [2] Department of Medical Oncology, Dana Farber Cancer Institute, Boston, MA, USA [3] Department of Pathology, Massachusetts General Hospital, Boston, MA, USA [4] Department of Pathology, Harvard Medical School, Boston, MA, USA
| | - F Duke
- Cancer Program, The Broad Institute of Harvard and M.I.T., 7 Cambridge Center, Cambridge, MA, USA
| | - J Wala
- 1] Cancer Program, The Broad Institute of Harvard and M.I.T., 7 Cambridge Center, Cambridge, MA, USA [2] Department of Medical Oncology, Dana Farber Cancer Institute, Boston, MA, USA [3] Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - N Kaplan
- Department of Medical Oncology, Dana Farber Cancer Institute, Boston, MA, USA
| | - G-X Shi
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY, USA
| | - D A Andres
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY, USA
| | - M Meyerson
- 1] Cancer Program, The Broad Institute of Harvard and M.I.T., 7 Cambridge Center, Cambridge, MA, USA [2] Department of Medical Oncology, Dana Farber Cancer Institute, Boston, MA, USA [3] Department of Pathology, Harvard Medical School, Boston, MA, USA
| |
Collapse
|
35
|
Abstract
Cycoloxygenase-2 (COX-2) induction is prevalent in a variety of (brain and peripheral) injury models where COX-2 levels correlate with disease progression. Thus, COX-2 has been widely explored for anti-inflammatory therapy with COX-2 inhibitors, which proved to be effective in reducing the pain and inflammation in patients with arthritis and menstrual cramps, but they have not provided any benefit to patients with chronic inflammatory neurodegenerative disease. Recently, two COX-2 drugs, rofecoxib and valdecoxib, were withdrawn from the United States market due to cardiovascular side effects. Thus, future anti-inflammatory therapy could be targeted through a specific prostanoid receptor downstream of COX-2. The PGE2 receptor EP2 is emerging as a pro-inflammatory target in a variety of CNS and peripheral diseases. Here we highlight the latest developments on the role of EP2 in diseases, mechanism of activation, and small molecule discovery targeted either to enhance or to block the function of this receptor.
Collapse
Affiliation(s)
- Thota Ganesh
- Department of Pharmacology, Emory University School of Medicine , 1510 Clifton Road, Atlanta, Georgia, 30322, United States
| |
Collapse
|
36
|
Claulansine F promotes neuritogenesis in PC12 cells via the ERK signaling pathway. Acta Pharmacol Sin 2013; 34:1499-507. [PMID: 24096602 DOI: 10.1038/aps.2013.95] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 06/24/2013] [Indexed: 12/21/2022] Open
Abstract
AIM To study the effects of Claulansine F (Clau F), a carbazole alkaloid isolated from the stem of Clausena lansium (Lour) Skeels, on neuritogenesis of PC12 cells, and to elucidate the mechanism of action. METHODS Neuritogenesis of PC12 cells was quantified under an inverted microscope. Expression of the neurite outgrowth marker GAP-43 was detected using immunofluorescence. GAP-43 transcription was measured using RT-PCR. Cell viability was evaluated with MTT assay. The levels of phosphor-ERK1/2, phosphor-CREB, phosphor-AKT and acetylate-p53 in the cells were examined using Western blotting analyses. RESULTS Clau F (10-100 μmol/L) significantly increased the percentage of PC12 cells bearing neurites. Clau F markedly increased the expression of GAP-43 in the cells. The efficiency of Clau F (10 μmol/L) in increasing neuritogenesis and GAP-43 expression was comparable to that of nerve growth factor (50 ng/mL). In addition, Clau F completely blocked the proliferation of PC12 cells within 7 d of incubation, whereas it did not cause cell death in cultured rat cortical neurons. Treatment of PC12 cells with Clau F activated both ERK and AKT signaling pathways. Co-treatment of PC12 cells with the specific ERK inhibitor PD98059, but not the specific PI3K inhibitor LY294002, blocked Clau F-induced neuritogenesis and GAP-43 upregulation. CONCLUSION Clau F promotes neuritogenesis in PC12 cells specifically via activation of the ERK signaling pathway.
Collapse
|
37
|
Perez-Aso M, Fernandez P, Mediero A, Chan ES, Cronstein BN. Adenosine 2A receptor promotes collagen production by human fibroblasts via pathways involving cyclic AMP and AKT but independent of Smad2/3. FASEB J 2013; 28:802-12. [PMID: 24200882 DOI: 10.1096/fj.13-241646] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Activation of adenosine A2A receptor (A2AR) promotes fibrosis and collagen synthesis. However, the underlying mechanism is still unclear, not least because cAMP, its principal effector, has been found to inhibit TGFβ1-induced collagen synthesis. Here, we show that in primary normal human dermal fibroblasts, A2AR stimulation with CGS21680 elicits a modest cAMP increase (150 ± 12% of control; EC50 54.8 nM), which stimulates collagen1 (Col1) and collagen3 (Col3), but maximal cAMP resulting from direct activation of adenylyl cyclase by forskolin (15,689 ± 7038% of control; EC50 360.7 nM) inhibits Col1 and increases Col3. Similar to Col1 expression, fibroblast proliferation increased following physiological cAMP increases by CGS21680 but was inhibited by cAMP increases beyond the physiological range by forskolin. The A2AR-mediated increase of Col1 and Col3 was mediated by AKT, while Col3, but not Col1, expression was dependent on p38 and repressed by ERK. TGFβ1 induced phosphorylation of Smad2/3 and increased Col3 expression, which was prevented by Smad3 depletion. In contrast, CGS21680 did not activate Smad2/3, and Smad2/3 knockdown did not prevent CGS21680-induced Col1 or Col3 increases. Our results indicate that cAMP is a concentration-dependent switch for collagen production via noncanonical, AKT-dependent, Smad2/3-independent signaling. These observations explain the paradoxical effects of cAMP on collagen expression.
Collapse
Affiliation(s)
- Miguel Perez-Aso
- 1Department of Medicine, New York University School of Medicine, 550 First Ave., New York, NY 10016, USA.
| | | | | | | | | |
Collapse
|
38
|
Taylor RDT, Madsen MG, Krause M, Sampedro-Castañeda M, Stocker M, Pedarzani P. Pituitary adenylate cyclase-activating polypeptide (PACAP) inhibits the slow afterhyperpolarizing current sIAHP in CA1 pyramidal neurons by activating multiple signaling pathways. Hippocampus 2013; 24:32-43. [PMID: 23996525 PMCID: PMC3920641 DOI: 10.1002/hipo.22201] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/20/2013] [Indexed: 12/13/2022]
Abstract
The slow afterhyperpolarizing current (sIAHP ) is a calcium-dependent potassium current that underlies the late phase of spike frequency adaptation in hippocampal and neocortical neurons. sIAHP is a well-known target of modulation by several neurotransmitters acting via the cyclic AMP (cAMP) and protein kinase A (PKA)-dependent pathway. The neuropeptide pituitary adenylate cyclase activating peptide (PACAP) and its receptors are present in the hippocampal formation. In this study we have investigated the effect of PACAP on the sIAHP and the signal transduction pathway used to modulate intrinsic excitability of hippocampal pyramidal neurons. We show that PACAP inhibits the sIAHP , resulting in a decrease of spike frequency adaptation, in rat CA1 pyramidal cells. The suppression of sIAHP by PACAP is mediated by PAC1 and VPAC1 receptors. Inhibition of PKA reduced the effect of PACAP on sIAHP, suggesting that PACAP exerts part of its inhibitory effect on sIAHP by increasing cAMP and activating PKA. The suppression of sIAHP by PACAP was also strongly hindered by the inhibition of p38 MAP kinase (p38 MAPK). Concomitant inhibition of PKA and p38 MAPK indicates that these two kinases act in a sequential manner in the same pathway leading to the suppression of sIAHP. Conversely, protein kinase C is not part of the signal transduction pathway used by PACAP to inhibit sIAHP in CA1 neurons. Our results show that PACAP enhances the excitability of CA1 pyramidal neurons by inhibiting the sIAHP through the activation of multiple signaling pathways, most prominently cAMP/PKA and p38 MAPK. Our findings disclose a novel modulatory action of p38 MAPK on intrinsic excitability and the sIAHP, underscoring the role of this current as a neuromodulatory hub regulated by multiple protein kinases in cortical neurons.
Collapse
Affiliation(s)
- Ruth D T Taylor
- Research Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | | | | | | | | | | |
Collapse
|
39
|
Cai W, Shi GX, Andres DA. Putting the Rit in cellular resistance: Rit, p38 MAPK and oxidative stress. Commun Integr Biol 2013; 6:e22297. [PMID: 23802035 PMCID: PMC3689566 DOI: 10.4161/cib.22297] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Cells mobilize diverse signaling pathways to protect against stress-mediated injury. Ras family GTPases play critical roles in this process, controlling the activation and integration of multiple regulatory cascades. p38 mitogen-activated protein kinase (MAPK) signaling serves as a critical fulcrum in this process, regulating networks that stimulate cellular apoptosis but also promote cell survival. However, this functional dichotomy is incompletely understood, particularly regulation of p38-dependent survival. Here, we discuss our recent evidence that the Rit GTPase associates with and is required for stress-mediated activation of a scaffolded p38-MK2-HSP27-Akt pro-survival signaling cascade. Drosophila lacking D-Ric, a Rit homologue, are susceptible to a variety of environmental stresses, while embryonic fibroblasts derived from Rit knockout mice display blunted stress-dependent signaling and decreased viability. Conversely, expression of constitutively active Rit triggers p38-Akt-dependent cell survival. Together, our studies establish Rit as the central regulator of an evolutionarily conserved, p38-dependent signaling cascade that functions as a critical survival mechanism in response to stress.
Collapse
Affiliation(s)
- Weikang Cai
- Department of Molecular and Cellular Biochemistry; College of Medicine; University of Kentucky; Lexington, KY USA
| | | | | |
Collapse
|
40
|
Jiang J, Dingledine R. Prostaglandin receptor EP2 in the crosshairs of anti-inflammation, anti-cancer, and neuroprotection. Trends Pharmacol Sci 2013; 34:413-23. [PMID: 23796953 DOI: 10.1016/j.tips.2013.05.003] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 05/05/2013] [Accepted: 05/10/2013] [Indexed: 10/26/2022]
Abstract
Modulation of a specific prostanoid synthase or receptor provides therapeutic alternatives to nonsteroidal anti-inflammatory drugs (NSAIDs) for treating pathological conditions governed by cyclooxygenase-2 (COX-2 or PTGS2). Among the COX-2 downstream signaling pathways, the prostaglandin E2 (PGE2) receptor EP2 subtype (PTGER2) is emerging as a crucial mediator of many physiological and pathological events. Genetic ablation strategies and recent advances in chemical biology provide tools for a better understanding of EP2 signaling. In the brain, the EP2 receptor modulates some beneficial effects, including neuroprotection, in acute models of excitotoxicity, neuroplasticity, and spatial learning via cAMP-PKA signaling. Conversely, EP2 activation accentuates chronic inflammation mainly through the cAMP-Epac pathway, likely contributing to delayed neurotoxicity. EP2 receptor activation also engages β-arrestin in a G-protein-independent pathway that promotes tumor cell growth and migration. Understanding the conditions under which multiple EP2 signaling pathways are engaged might suggest novel therapeutic strategies to target this key inflammatory prostaglandin receptor.
Collapse
Affiliation(s)
- Jianxiong Jiang
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA.
| | | |
Collapse
|
41
|
Shi GX, Cai W, Andres DA. Rit subfamily small GTPases: regulators in neuronal differentiation and survival. Cell Signal 2013; 25:2060-8. [PMID: 23770287 DOI: 10.1016/j.cellsig.2013.06.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 06/04/2013] [Indexed: 02/07/2023]
Abstract
Ras family small GTPases serve as binary molecular switches to regulate a broad array of cellular signaling cascades, playing essential roles in a vast range of normal physiological processes, with dysregulation of numerous Ras-superfamily G-protein-dependent regulatory cascades underlying the development of human disease. However, the physiological function for many "orphan" Ras-related GTPases remain poorly characterized, including members of the Rit subfamily GTPases. Rit is the founding member of a novel branch of the Ras subfamily, sharing close homology with the neuronally expressed Rin and Drosophila Ric GTPases. Here, we highlight recent studies using transgenic and knockout animal models which have begun to elucidate the physiological roles for the Rit subfamily, including emerging roles in the regulation of neuronal morphology and cellular survival signaling, and discuss new genetic data implicating Rit and Rin signaling in disorders such as cancer, Parkinson's disease, autism, and schizophrenia.
Collapse
Affiliation(s)
- Geng-Xian Shi
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, BBSRB, 741S. Limestone St., Lexington, KY 40536-0509, USA
| | | | | |
Collapse
|
42
|
Schmidt M, Dekker FJ, Maarsingh H. Exchange protein directly activated by cAMP (epac): a multidomain cAMP mediator in the regulation of diverse biological functions. Pharmacol Rev 2013; 65:670-709. [PMID: 23447132 DOI: 10.1124/pr.110.003707] [Citation(s) in RCA: 203] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Since the discovery nearly 60 years ago, cAMP is envisioned as one of the most universal and versatile second messengers. The tremendous feature of cAMP to tightly control highly diverse physiologic processes, including calcium homeostasis, metabolism, secretion, muscle contraction, cell fate, and gene transcription, is reflected by the award of five Nobel prizes. The discovery of Epac (exchange protein directly activated by cAMP) has ignited a new surge of cAMP-related research and has depicted novel cAMP properties independent of protein kinase A and cyclic nucleotide-gated channels. The multidomain architecture of Epac determines its activity state and allows cell-type specific protein-protein and protein-lipid interactions that control fine-tuning of pivotal biologic responses through the "old" second messenger cAMP. Compartmentalization of cAMP in space and time, maintained by A-kinase anchoring proteins, phosphodiesterases, and β-arrestins, contributes to the Epac signalosome of small GTPases, phospholipases, mitogen- and lipid-activated kinases, and transcription factors. These novel cAMP sensors seem to implement certain unexpected signaling properties of cAMP and thereby to permit delicate adaptations of biologic responses. Agonists and antagonists selective for Epac are developed and will support further studies on the biologic net outcome of the activation of Epac. This will increase our current knowledge on the pathophysiology of devastating diseases, such as diabetes, cognitive impairment, renal and heart failure, (pulmonary) hypertension, asthma, and chronic obstructive pulmonary disease. Further insights into the cAMP dynamics executed by the Epac signalosome will help to optimize the pharmacological treatment of these diseases.
Collapse
Affiliation(s)
- Martina Schmidt
- Department of Molecular Pharmacology, Groningen Research Institute for Pharmacy, University of Groningen, 9713 AV Groningen, The Netherlands.
| | | | | |
Collapse
|
43
|
Blechman J, Levkowitz G. Alternative Splicing of the Pituitary Adenylate Cyclase-Activating Polypeptide Receptor PAC1: Mechanisms of Fine Tuning of Brain Activity. Front Endocrinol (Lausanne) 2013; 4:55. [PMID: 23734144 PMCID: PMC3659299 DOI: 10.3389/fendo.2013.00055] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2012] [Accepted: 04/24/2013] [Indexed: 12/11/2022] Open
Abstract
Alternative splicing of the precursor mRNA encoding for the neuropeptide receptor PAC1/ADCYAP1R1 generates multiple protein products that exhibit pleiotropic activities. Recent studies in mammals and zebrafish have implicated some of these splice isoforms in control of both cellular and body homeostasis. Here, we review the regulation of PAC1 splice variants and their underlying signal transduction and physiological processes in the nervous system.
Collapse
Affiliation(s)
- Janna Blechman
- Department of Molecular Cell Biology, Weizmann Institute of ScienceRehovot, Israel
| | - Gil Levkowitz
- Department of Molecular Cell Biology, Weizmann Institute of ScienceRehovot, Israel
- *Correspondence: Gil Levkowitz, Department of Molecular Cell Biology, Weizmann Institute of Science, P. O. Box 26, Rehovot 76100, Israel. e-mail:
| |
Collapse
|
44
|
Mohan S, Ahmad AS, Glushakov AV, Chambers C, Doré S. Putative role of prostaglandin receptor in intracerebral hemorrhage. Front Neurol 2012; 3:145. [PMID: 23097645 PMCID: PMC3477820 DOI: 10.3389/fneur.2012.00145] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Accepted: 09/30/2012] [Indexed: 01/21/2023] Open
Abstract
Each year, approximately 795,000 people experience a new or recurrent stroke. Of all strokes, 84% are ischemic, 13% are intracerebral hemorrhage (ICH) strokes, and 3% are subarachnoid hemorrhage strokes. Despite the decreased incidence of ischemic stroke, there has been no change in the incidence of hemorrhagic stroke in the last decade. ICH is a devastating disease 37–38% of patients between the ages of 45 and 64 die within 30 days. In an effort to prevent ischemic and hemorrhagic strokes we and others have been studying the role of prostaglandins and their receptors. Prostaglandins are bioactive lipids derived from the metabolism of arachidonic acid. They sustain homeostatic functions and mediate pathogenic mechanisms, including the inflammatory response. Most prostaglandins are produced from specific enzymes and act upon cells via distinct G-protein coupled receptors. The presence of multiple prostaglandin receptors cross-reactivity and coupling to different signal transduction pathways allow differentiated cells to respond to prostaglandins in a unique manner. Due to the number of prostaglandin receptors, prostaglandin-dependent signaling can function either to promote neuronal survival or injury following acute excitotoxicity, hypoxia, and stress induced by ICH. To better understand the mechanisms of neuronal survival and neurotoxicity mediated by prostaglandin receptors, it is essential to understand downstream signaling. Several groups including ours have discovered unique roles for prostaglandin receptors in rodent models of ischemic stroke, excitotoxicity, and Alzheimer disease, highlighting the emerging role of prostaglandin receptor signaling in hemorrhagic stroke with a focus on cyclic-adenosine monophosphate and calcium (Ca2+) signaling. We review current ICH data and discuss future directions notably on prostaglandin receptors, which may lead to the development of unique therapeutic targets against hemorrhagic stroke and brain injuries alike.
Collapse
Affiliation(s)
- Shekher Mohan
- Department of Anesthesiology, College of Medicine, University of Florida Gainesville, FL, USA
| | | | | | | | | |
Collapse
|
45
|
Shi GX, Cai W, Andres DA. Rit-mediated stress resistance involves a p38-mitogen- and stress-activated protein kinase 1 (MSK1)-dependent cAMP response element-binding protein (CREB) activation cascade. J Biol Chem 2012; 287:39859-68. [PMID: 23038261 DOI: 10.1074/jbc.m112.384248] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The cAMP response element (CRE)-binding protein (CREB) is a key regulatory factor of gene transcription, and plays an essential role in development of the central nervous system and for neuroprotection. Multiple signaling pathways have been shown to contribute to the regulation of CREB-dependent transcription, including both ERK and p38 mitogen-activated protein (MAP) kinases cascades. Recent studies have identified the Ras-related small G-protein, Rit, as a central regulator of a p38-MK2-HSP27 signaling cascade that functions as a critical survival mechanism for cells adapting to stress. Here, we examine the contribution of Rit-p38 signaling to the control of stress-dependent gene transcription. Using a pheochromocytoma cell model, we find that a novel Rit-p38-MSK1/2 pathway plays a critical role in stress-mediated CREB activation. RNAi-mediated Rit silencing, or inhibition of p38 or MSK1/2 kinases, was found to disrupt stress-mediated CREB-dependent transcription, resulting in increased cell death. Furthermore, ectopic expression of active Rit stimulates CREB-Ser133 phosphorylation, induces expression of the anti-apoptotic Bcl-2 and Bcl(XL) proteins, and promotes cell survival. These data indicate that the Rit-p38-MSK1/2 signaling pathway may have an important role in the stress-dependent regulation of CREB-dependent gene expression.
Collapse
Affiliation(s)
- Geng-Xian Shi
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, Kentucky 40536-0509, USA.
| | | | | |
Collapse
|
46
|
Abstract
Epacs (exchange proteins directly activated by cAMP) are guanine-nucleotide-exchange factors for the Ras-like small GTPases Rap1 and Rap2. Epacs were discovered in 1998 as new sensors for the second messenger cAMP acting in parallel to PKA (protein kinase A). As cAMP regulates many important physiological functions in brain and heart, the existence of Epacs raises many questions regarding their role in these tissues. The present review focuses on the biological roles and signalling pathways of Epacs in neurons and cardiac myocytes. We discuss the potential involvement of Epacs in the manifestation of cardiac and central diseases such as cardiac hypertrophy and memory disorders.
Collapse
|
47
|
Shi GX, Andres DA, Cai W. Ras family small GTPase-mediated neuroprotective signaling in stroke. Cent Nerv Syst Agents Med Chem 2012; 11:114-37. [PMID: 21521171 DOI: 10.2174/187152411796011349] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Revised: 01/18/2011] [Accepted: 03/22/2011] [Indexed: 12/31/2022]
Abstract
Selective neuronal cell death is one of the major causes of neuronal damage following stroke, and cerebral cells naturally mobilize diverse survival signaling pathways to protect against ischemia. Importantly, therapeutic strategies designed to improve endogenous anti-apoptotic signaling appear to hold great promise in stroke treatment. While a variety of complex mechanisms have been implicated in the pathogenesis of stroke, the overall mechanisms governing the balance between cell survival and death are not well-defined. Ras family small GTPases are activated following ischemic insults, and in turn, serve as intrinsic switches to regulate neuronal survival and regeneration. Their ability to integrate diverse intracellular signal transduction pathways makes them critical regulators and potential therapeutic targets for neuronal recovery after stroke. This article highlights the contribution of Ras family GTPases to neuroprotective signaling cascades, including mitogen-activated protein kinase (MAPK) family protein kinase- and AKT/PKB-dependent signaling pathways as well as the regulation of cAMP response element binding (CREB), Forkhead box O (FoxO) and hypoxiainducible factor 1(HIF1) transcription factors, in stroke.
Collapse
Affiliation(s)
- Geng-Xian Shi
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, 741 S. Limestone St., Lexington, KY 40536-0509, USA.
| | | | | |
Collapse
|
48
|
Rap-linked cAMP signaling Epac proteins: Compartmentation, functioning and disease implications. Cell Signal 2011; 23:1257-66. [DOI: 10.1016/j.cellsig.2011.03.007] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 03/04/2011] [Accepted: 03/04/2011] [Indexed: 12/14/2022]
|
49
|
Cai W, Rudolph JL, Harrison SMW, Jin L, Frantz AL, Harrison DA, Andres DA. An evolutionarily conserved Rit GTPase-p38 MAPK signaling pathway mediates oxidative stress resistance. Mol Biol Cell 2011; 22:3231-41. [PMID: 21737674 PMCID: PMC3164468 DOI: 10.1091/mbc.e11-05-0400] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Rit knockout mice and D-Ric null Drosophila were used to identify the Rit/RIC subfamily of Ras-related GTPases as regulators of an evolutionarily conserved, p38-dependent signaling cascade that functions as a survival mechanism for cells in response to reactive oxygen species exposure. Ras-related small GTP-binding proteins control a wide range of cellular processes by regulating a variety of effector pathways, including prominent roles in the control of mitogen-activated protein kinase (MAPK) cascades. Although the regulatory role(s) for many Ras family GTPases are well established, the physiological function for the Rit/Rin subfamily has been lacking. Here, using both knockout mice and Drosophila models, we demonstrate an evolutionarily conserved role for Rit subfamily GTPases (mammalian Rit and Rin, and the Drosophila RIC homologue) in governing survival in response to oxidative stress. Primary embryonic fibroblasts derived from Rit knockout mice display increased apoptosis and selective disruption of MAPK signaling following reactive oxygen species (ROS) exposure but not in response to endoplasmic reticulum stress or DNA damage. These deficits include a reduction in ROS-mediated stimulation of a p38-MK2-HSP27 signaling cascade that controls Akt activation, directing Bad phosphorylation to promote cell survival. Furthermore, D-RIC null flies display increased susceptibility to environmental stresses and reduced stress-dependent p38 signaling, extending the Rit-p38 survival pathway to Drosophila. Together, our studies establish the Rit GTPases as critical regulators of an evolutionarily conserved, p38 MAPK–dependent signaling cascade that functions as an important survival mechanism for cells in response to oxidative stress.
Collapse
Affiliation(s)
- Weikang Cai
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536-0509, USA
| | | | | | | | | | | | | |
Collapse
|
50
|
Cyclic AMP signalling through PKA but not Epac is essential for neurturin-induced biphasic ERK1/2 activation and neurite outgrowths through GFRα2 isoforms. Cell Signal 2011; 23:1727-37. [PMID: 21723942 DOI: 10.1016/j.cellsig.2011.06.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 06/09/2011] [Accepted: 06/15/2011] [Indexed: 11/23/2022]
Abstract
Cyclic AMP (cAMP) and neurotrophic factors are known to interact closely to promote neurite outgrowth and neuronal regeneration. Glial cell line-derived neurotrophic factor (GDNF) and its family member neurturin (NTN) transduce signal through a multi-component receptor complex consisting of GDNF family receptor alpha 2 (GFRα2) and Ret receptor tyrosine kinase. Neurons from GFRα2-deficient mice do not promote axonal initiation when stimulated by NTN, consistent with the role of GFRα2 in neuronal outgrowth. Multiple alternatively spliced isoforms of GFRα2 are known to be expressed in the nervous system. GFRα2a and GFRα2c but not GFRα2b promoted neurite outgrowth. It is currently unknown if cAMP signalling is differentially regulated by these isoforms. In this study, NTN activation of GFRα2a and GFRα2c but not GFRα2b induced biphasic ERK1/2 activation and phosphorylation of the major cAMP target CREB. Interestingly, inhibition of cAMP signalling significantly impaired GFRα2a and GFRα2c-mediated neurite outgrowth while cAMP agonists cooperated with GFRα2b to induce neurite outgrowth. Importantly, the specific cAMP effector PKA but not Epac was essential for NTN-induced neurite outgrowth, through transcription and translation-dependent activation of late phase ERK1/2. Taken together, these results not only demonstrated the essential role of cAMP-PKA signalling in NTN-induced biphasic ERK1/2 activation and neurite outgrowth, but also suggested cAMP-PKA signalling as a hitherto unrecognized underlying mechanism contributing to the differential neuritogenic activities of GFRα2 isoforms.
Collapse
|