1
|
Cheng Q, Graves MD, Pallas SL. Dynamic Alterations of Retinal EphA5 Expression in Retinocollicular Map Plasticity. Dev Neurobiol 2019; 79:252-267. [PMID: 30916472 PMCID: PMC6506164 DOI: 10.1002/dneu.22675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 02/14/2019] [Accepted: 02/28/2019] [Indexed: 11/10/2022]
Abstract
The topographically ordered retinocollicular projection is an excellent system for studying the mechanism of axon guidance. Gradients of EphA receptors in the retina and ephrin-As in the superior colliculus (SC) pattern the anteroposterior axis of the retinocollicular map, but whether they are involved in map plasticity after injury is unknown. Partial damage to the caudal SC at birth creates a compressed, complete retinotopic map in the remaining SC without affecting visual response properties. Previously, we found that the gradient of ephrin-A expression in compressed maps is steeper than normal, suggesting an instructive role in compression. Here we measured EphA5 mRNA and protein levels after caudal SC damage in order to test the hypothesis that changes in retinal EphA5 expression occur that are complementary to the changes in collicular ephrin-A expression. We find that the nasotemporal gradient of EphA5 receptor expression steepens in the retina and overall expression levels change dynamically, especially in temporal retina, supporting the hypothesis. This change in receptor expression occurs after the change in ephrin-A ligand expression. We propose that changes in the retinal EphA5 gradient guide recovery of the retinocollicular projection from early injury. This could occur directly through the change in EphA5 expression instructing retino-SC map compression, or through ephrin-A ligand signaling instructing a change in EphA5 receptor expression that in turn signals the retinocollicular map to compress. Understanding what molecular signals direct compensation for injury is essential to developing rehabilitative strategies and maximizing the potential for recovery.
Collapse
Affiliation(s)
- Qi Cheng
- Neuroscience Institute Georgia State University, Atlanta, GA, USA
| | - Mark D. Graves
- Department of Biology, Georgia State University, Atlanta, GA, USA
| | - Sarah L. Pallas
- Neuroscience Institute Georgia State University, Atlanta, GA, USA
- Department of Biology, Georgia State University, Atlanta, GA, USA
| |
Collapse
|
2
|
Ghosh Moulick R, Afanasenkau D, Choi SE, Albers J, Lange W, Maybeck V, Utesch T, Offenhäusser A. Reconstitution of Fusion Proteins in Supported Lipid Bilayers for the Study of Cell Surface Receptor-Ligand Interactions in Cell-Cell Contact. Langmuir 2016; 32:3462-3469. [PMID: 26986674 DOI: 10.1021/acs.langmuir.5b04644] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Bioactive molecules such as adhesion ligands, growth factors, or enzymes play an important role in modulating cell behavior such as cell adhesion, spreading, and differentiation. Deciphering the mechanism of ligand-mediated cell adhesion and associated signaling is of great interest not only for fundamental biophysical investigations but also for applications in medicine and biotechnology. In the presented work, we developed a new biomimetic platform that enables culturing primary neurons and testing cell surface-receptor ligand interactions in cell-cell contacts as, e.g., in neuronal synapses. This platform consists of a supported lipid bilayer modified with incorporated neuronal adhesion proteins conjugated with the Fc-domain of IgG (ephrin A5 Fc-chimera). We extensively characterized properties of these protein containing bilayers using fluorescence recovery after photobleaching (FRAP), quartz crystal microbalance with dissipation (QCM-D), and immunostaining. We conclude that the Fc-domain is the part responsible for the incorporation of the protein into the bilayer. The biomimetic platform prepared by this new approach was able to promote neuronal cell adhesion and maintain growth as well as facilitate neuronal maturation as shown by electrophysiological measurements. We believe that our approach can be extended to insert other proteins to create a general culture platform for neurons and other cell types.
Collapse
Affiliation(s)
- R Ghosh Moulick
- Institute for Bioelectronics (ICS-8), Forschungszentrum Jülich , Wilhelm-Johnen Straße, 52425 Jülich, Germany
| | - D Afanasenkau
- Institute for Bioelectronics (ICS-8), Forschungszentrum Jülich , Wilhelm-Johnen Straße, 52425 Jülich, Germany
| | - S-E Choi
- Institute for Bioelectronics (ICS-8), Forschungszentrum Jülich , Wilhelm-Johnen Straße, 52425 Jülich, Germany
| | - J Albers
- Institute for Bioelectronics (ICS-8), Forschungszentrum Jülich , Wilhelm-Johnen Straße, 52425 Jülich, Germany
| | - W Lange
- Institute for Bioelectronics (ICS-8), Forschungszentrum Jülich , Wilhelm-Johnen Straße, 52425 Jülich, Germany
| | - V Maybeck
- Institute for Bioelectronics (ICS-8), Forschungszentrum Jülich , Wilhelm-Johnen Straße, 52425 Jülich, Germany
| | - T Utesch
- Department of Chemistry, Technische Universität Berlin , Straße des 17. Juni 135, 10623 Berlin, Germany
| | - A Offenhäusser
- Institute for Bioelectronics (ICS-8), Forschungszentrum Jülich , Wilhelm-Johnen Straße, 52425 Jülich, Germany
| |
Collapse
|
3
|
Gupta G, Song J. C-Terminal Auto-Regulatory Motif of Hepatitis C Virus NS5B Interacts with Human VAPB-MSP to Form a Dynamic Replication Complex. PLoS One 2016; 11:e0147278. [PMID: 26784321 PMCID: PMC4718513 DOI: 10.1371/journal.pone.0147278] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 01/02/2016] [Indexed: 12/12/2022] Open
Abstract
Hepatitis C virus (HCV) is a pathogen of global importance and nearly 200 million people are chronically infected with HCV. HCV is an enveloped single-stranded RNA virus, which is characteristic of the formation of the host membrane associated replication complex. Previous functional studies have already established that the human ER-anchored VAPB protein acts as a host factor to form a complex with HCV NS5A and NS5B, which may be established as a drug target. However, there is lacking of biophysical characterization of the structures and interfaces of the complex, partly due to the dynamic nature of the complex formation and dissociation, which is extensively involved in intrinsically-disordered domains. Here by an integrated use of domain dissection and NMR spectroscopy, for the first time we have successfully deciphered that the HCV NS5B utilizes its auto-regulatory C-linker to bind the VAPB-MSP domain to form a dynamic complex. This finding implies that the NS5B C-linker is capable of playing dual roles by a switch between the folded and disordered states. Interestingly, our previous and present studies together reveal that both HCV NS5A and NS5B bind to the MSP domains of the dimeric VAP with significantly overlapped interfaces and similar affinities. The identification that EphA2 and EphA5 bind to the MSP domain with higher affinity than EphA4 provides a biophysical basis for further exploring whether other than inducing ALS-like syndrome, the HCV infection might also trigger pathogenesis associated with signalling pathways mediated by EphA2 and EphA5.
Collapse
Affiliation(s)
- Garvita Gupta
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Singapore
| | - Jianxing Song
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Singapore
- * E-mail:
| |
Collapse
|
4
|
Kikuchi S, Kaibe N, Morimoto K, Fukui H, Niwa H, Maeyama Y, Takemura M, Matsumoto M, Nakamori S, Miwa H, Hirota S, Sasako M. Overexpression of Ephrin A2 receptors in cancer stromal cells is a prognostic factor for the relapse of gastric cancer. Gastric Cancer 2015; 18:485-94. [PMID: 24908114 DOI: 10.1007/s10120-014-0390-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 05/15/2014] [Indexed: 02/07/2023]
Abstract
BACKGROUND Microenvironments control cancer growth and progression. We explored the prognostic impact of stromal reaction and cancer stromal cells on relapse risk and survival after curative gastrectomy in gastric cancer patients. METHODS Tissue samples were obtained from 107 patients with gastric adenocarcinoma who underwent curative (R0) gastrectomy. Primary stromal cells isolated from gastric cancer tissue (GCSC) and normal gastric tissue (Gastric stromal cell: GSC) in each patient were cultured and subjected to comprehensive proteome (LC-MS/MS) and real-time RT-PCR analysis. Expression of Ephrin A2 receptors (EphA2) in cancers and GCSC was evaluated immunohistochemically. Intermingling of EphA2-positive cancer cells and GCSC (IC/A2+) and overexpression of EphA2 in cancer cells (Ca/A2+) in invasive parts of tumors were assessed, as were relationships of IC/A2+, Ca/A2+, and clinicopathological factors with relapse-free survival and overall survival. RESULTS Proteome analysis showed that EphA2 expression was significantly higher in GCSC than GSC. Real-time RT-PCR analysis showed that levels of EphA1/A2/A3/A5 and EphB2/B4 were ≥2.0-fold higher in GCSC than GSC. Ca/A2 and IC/A2 were positive in 65 (60.7 %) and 26 (24.3 %) patients, respectively. Relapse was significantly more frequent in IC/A2-positive than in IC/A2-negative (HR, 2.12; 95 % CI, 1.16-5.41; p = 0.0207) patients. Among the 54 patients who received S-1 adjuvant chemotherapy, relapse-free survival (RFS) was significantly shorter in those who were IC/A2-positive than in those who were IC/A2-negative and Ca/A2-negative (HR, 2.83; 95 % CI, 1.12-12.12; p = 0.0339). Multivariable analysis indicated that pathological stage (p = 0.010) and IC/A2+ (p = 0.008) were independent risk factors for recurrence. CONCLUSION IC/A2+ was predictive of relapse after curative (R0) gastrectomy.
Collapse
Affiliation(s)
- Shojiro Kikuchi
- Department of Surgery, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo, 663-8501, Japan,
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Yamada T, Yuasa M, Masaoka T, Taniyama T, Maehara H, Torigoe I, Yoshii T, Shinomiya K, Okawa A, Sotome S. After repeated division, bone marrow stromal cells express inhibitory factors with osteogenic capabilities, and EphA5 is a primary candidate. Bone 2013; 57:343-54. [PMID: 24029132 DOI: 10.1016/j.bone.2013.08.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 08/23/2013] [Accepted: 08/29/2013] [Indexed: 01/01/2023]
Abstract
The differentiation capability of human bone marrow stromal cells (hBMSCs) is thought to deteriorate over multiple doubling processes. To clarify the deterioration mechanisms, the multilineage differentiation capabilities of short- and long-term passaged BMSCs were compared. Predictably, long-term passaged BMSCs showed reduced differentiation capacities compared to short-term passaged cells. Furthermore, a non-human primate heterotopic bone formation model demonstrated that long-term passaged BMSCs have bone formation capabilities but also exert inhibitory effects on bone formation. This finding indicated that long-term passaged BMSCs express higher levels of inhibitory factors than short-term passaged BMSCs do. Co-culture assays of short- and long-term passaged BMSCs suggested that the inhibitory signals required cell-cell contact and would therefore be expressed on the cell membrane. A microarray analysis of BMSCs identified ephrin type-A receptor 5 (EphA5) as an inhibitory factor candidate. Quantitative PCR revealed that among all members of the ephrin and Eph receptor families, only the expression of EphA5 was increased by BMSC proliferation. A gene knockdown analysis using siRNAs demonstrated that knockdown of EphA5 gene expression in long-term passaged BMSCs led to an increase in ALP mRNA expression. These results indicate that EphA5 may be a negative regulator of bone formation. A better understanding of the roles of the ephrin and Eph receptor families in hBMSCs may lead to alternative approaches for manipulating hBMSC fate. In addition, this avenue of discovery may provide new therapeutic targets and quality-control markers of the osteogenic differentiation capabilities of hBMSCs.
Collapse
Affiliation(s)
- Tsuyoshi Yamada
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan; Global Center of Excellence (GCOE) Program, International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo Medical and Dental University, Tokyo, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
6
|
Huan X, Shi J, Lim L, Mitra S, Zhu W, Qin H, Pasquale EB, Song J. Unique structure and dynamics of the EphA5 ligand binding domain mediate its binding specificity as revealed by X-ray crystallography, NMR and MD simulations. PLoS One 2013; 8:e74040. [PMID: 24086308 PMCID: PMC3782497 DOI: 10.1371/journal.pone.0074040] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 07/25/2013] [Indexed: 12/26/2022] Open
Abstract
The 16 EphA and EphB receptors represent the largest family of receptor tyrosine kinases, and their interactions with 9 ephrin-A and ephrin-B ligands initiate bidirectional signals controlling many physiological and pathological processes. Most interactions occur between receptor and ephrins of the same class, and only EphA4 can bind all A and B ephrins. To understand the structural and dynamic principles that enable Eph receptors to utilize the same jellyroll β-sandwich fold to bind ephrins, the VAPB-MSP domain, peptides and small molecules, we have used crystallography, NMR and molecular dynamics (MD) simulations to determine the first structure and dynamics of the EphA5 ligand-binding domain (LBD), which only binds ephrin-A ligands. Unexpectedly, despite being unbound, the high affinity ephrin-binding pocket of EphA5 resembles that of other Eph receptors bound to ephrins, with a helical conformation over the J–K loop and an open pocket. The openness of the pocket is further supported by NMR hydrogen/deuterium exchange data and MD simulations. Additionally, the EphA5 LBD undergoes significant picosecond-nanosecond conformational exchanges over the loops, as revealed by NMR and MD simulations, but lacks global conformational exchanges on the microsecond-millisecond time scale. This is markedly different from the EphA4 LBD, which shares 74% sequence identity and 87% homology. Consequently, the unbound EphA5 LBD appears to comprise an ensemble of open conformations that have only small variations over the loops and appear ready to bind ephrin-A ligands. These findings show how two proteins with high sequence homology and structural similarity are still able to achieve distinctive binding specificities through different dynamics, which may represent a general mechanism whereby the same protein fold can serve for different functions. Our findings also suggest that a promising strategy to design agonists/antagonists with high affinity and selectivity might be to target specific dynamic states of the Eph receptor LBDs.
Collapse
Affiliation(s)
- Xuelu Huan
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, Republic of Singapore
| | - Jiahai Shi
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Republic of Singapore
| | - Liangzhong Lim
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Republic of Singapore
| | - Sayantan Mitra
- Sanford-Burnham Medical Research Institute, La Jolla, California, United States of America
| | - Wanlong Zhu
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Republic of Singapore
| | - Haina Qin
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Republic of Singapore
| | - Elena B. Pasquale
- Sanford-Burnham Medical Research Institute, La Jolla, California, United States of America
- Pathology Department, University of California San Diego, La Jolla, California, United States of America
| | - Jianxing Song
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, Republic of Singapore
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Republic of Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore
- * E-mail:
| |
Collapse
|
7
|
Jain R, Jain D, Liu Q, Bartosinska B, Wang J, Schumann D, Kauschke SG, Eickelmann P, Piemonti L, Gray NS, Lammert E. Pharmacological inhibition of Eph receptors enhances glucose-stimulated insulin secretion from mouse and human pancreatic islets. Diabetologia 2013; 56:1350-5. [PMID: 23475368 DOI: 10.1007/s00125-013-2877-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 02/07/2013] [Indexed: 12/22/2022]
Abstract
AIMS/HYPOTHESIS Type 2 diabetes is characterised by impaired glucose-stimulated insulin secretion (GSIS) from pancreatic islets. Since erythropoietin-producing hepatoma (Eph)-ephrin bidirectional signalling fine-tunes GSIS from pancreatic beta cells, we investigated Eph receptor tyrosine kinases (RTK) as potential drug targets for selectively increasing GSIS. METHODS Insulin secretion assays were carried out using mouse and human pancreatic islets as well as mouse insulinoma (MIN6) cells in the presence or absence of two Eph RTK inhibitors. Furthermore, the most potent inhibitor was injected into mice to evaluate its effects on glucose tolerance and plasma insulin levels. RESULTS We showed that the Eph RTK inhibitors selectively increased GSIS from MIN6 cells as well as mouse and human islets. Our results also showed that the insulin secretory effects of these compounds required Eph-ephrin signalling. Finally, pharmacological inhibition of Eph receptor signalling improved glucose tolerance in mice. CONCLUSIONS/INTERPRETATION We showed for the first time that Eph RTKs represent targets for small molecules to selectively increase GSIS and improve glucose tolerance.
Collapse
Affiliation(s)
- R Jain
- Institute of Metabolic Physiology and German Diabetes Center, Heinrich-Heine University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Mobbs CV, Moreno C. Hypothalamic EphA5 facilitates counterregulatory responses: possible role for bidirectional signaling leading to bistability that enhances responsiveness to hypoglycemia. Diabetes 2013; 62:1014-6. [PMID: 23520275 PMCID: PMC3609568 DOI: 10.2337/db12-1735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Charles V Mobbs
- Department of Neuroscience, Mount Sinai School of Medicine, New York, New York,
| | | |
Collapse
|
9
|
Szepietowska B, Zhu W, Czyzyk J, Eid T, Sherwin RS. EphA5-EphrinA5 interactions within the ventromedial hypothalamus influence counterregulatory hormone release and local glutamine/glutamate balance during hypoglycemia. Diabetes 2013; 62:1282-8. [PMID: 23274893 PMCID: PMC3609598 DOI: 10.2337/db12-0982] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Activation of β-cell EphA5 receptors by its ligand ephrinA5 from adjacent β-cells has been reported to decrease insulin secretion during hypoglycemia. Given the similarities between islet and ventromedial hypothalamus (VMH) glucose sensing, we tested the hypothesis that the EphA5/ephrinA5 system might function within the VMH during hypoglycemia to stimulate counterregulatory hormone release as well. Counterregulatory responses and glutamine/glutamate concentrations in the VMH were assessed during a hyperinsulinemic-hypoglycemic glucose clamp study in chronically catheterized awake male Sprague-Dawley rats that received an acute VMH microinjection of ephrinA5-Fc, chronic VMH knockdown, or overexpression of ephrinA5 using an adenoassociated viral construct. Local stimulation of VMH EphA5 receptors by ephrinA5-Fc or ephrinA5 overexpression increased, whereas knockdown of VMH ephrinA5 reduced counterregulatory responses during hypoglycemia. Overexpression of VMH ephrinA5 transiently increased local glutamate concentrations, whereas ephrinA5 knockdown produced profound suppression of VMH interstitial fluid glutamine concentrations in the basal state and during hypoglycemia. Changes in ephrinA5/EphA5 interactions within the VMH, a key brain glucose-sensing region, act in concert with islets to restore glucose homeostasis during acute hypoglycemia, and its effect on counterregulation may be mediated by changes in glutamate/glutamine cycling.
Collapse
Affiliation(s)
- Barbara Szepietowska
- Department of Internal Medicine and Endocrinology, Yale University School of Medicine, New Haven, Connecticut
| | - Wanling Zhu
- Department of Internal Medicine and Endocrinology, Yale University School of Medicine, New Haven, Connecticut
| | - Jan Czyzyk
- Department of Pathology and Laboratory Medicine, University of Rochester, Rochester, New York
| | - Tore Eid
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Robert S. Sherwin
- Department of Internal Medicine and Endocrinology, Yale University School of Medicine, New Haven, Connecticut
- Corresponding author: Robert S. Sherwin,
| |
Collapse
|
10
|
Abstract
The EphA5 receptor tyrosine kinase plays key roles in axon guidance during development. However, the presence of EphA5 protein in the nervous system has not been fully characterized. To examine EphA5 localization better, mutant mice, in which the EphA5 cytoplasmic domain was replaced with beta-galactosidase, were analyzed for both temporal and regional changes in the distribution of EphA5 protein in the developing and adult nervous system. During embryonic development, high levels of EphA5 protein were found in the retina, olfactory bulb, cerebral neocortex, hippocampus, pretectum, tectum, cranial nerve nuclei, and spinal cord. Variations in intensity were observed as development proceeded. Staining of pretectal nuclei, tectal nuclei, and other areas of the mesencephalon became more diffuse after maturity, whereas the cerebral neocortex gained more robust intensity. In the adult, receptor protein continued to be detected in many areas including the olfactory nuclei, neocortex, piriform cortex, induseum griseum, hippocampus, thalamus, amygdala, hypothalamus, and septum. In addition, EphA5 protein was found in the claustrum, stria terminalis, barrel cortex, and striatal patches, and along discrete axon tracts within the corpus callosum of the adult. We conclude that EphA5 function is not limited to the developing mouse brain and may play a role in synaptic plasticity in the adult.
Collapse
Affiliation(s)
- Margaret A. Cooper
- Laboratory for Cancer Research, College of Pharmacy, Rutgers University, Piscataway, New Jersey 08854
| | - David P. Crockett
- Department of Neuroscience and Cell Biology, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey, 08854
| | - Richard S. Nowakowski
- Department of Neuroscience and Cell Biology, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey, 08854
| | | | - Renping Zhou
- Laboratory for Cancer Research, College of Pharmacy, Rutgers University, Piscataway, New Jersey 08854
- Department of Neuroscience and Cell Biology, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey, 08854
| |
Collapse
|
11
|
Abstract
AMP-activated protein kinase (AMPK) is a key regulator of cellular and whole-body energy homeostasis. Recently, 12 AMPK-related kinases (BRSK1, BRSK2, NUAK1, NUAK2, QIK, QSK, SIK, MARK1, MARK2, MARK3, MARK4 and MELK) were identified that are closely related by sequence homology to the catalytic domain of AMPK. The protein kinase LKB1 acts as a master upstream kinase activating AMPK and 11 of the AMPK-related kinases by phosphorylation of a conserved threonine residue in their T-loop region. Further sequence analyses have identified the eight-member SNRK kinase family as distant relatives of AMPK. However, only one of these is phosphorylated and activated by LKB1. Although much is known about AMPK, many of the AMPK-related kinases remain largely uncharacterized. This review outlines the general similarities in structure and function of the AMPK-related kinases before examining the specific characteristics of each, including a brief discussion of the SNRK family.
Collapse
Affiliation(s)
- N J Bright
- Cellular Stress Group, MRC Clinical Sciences Centre, London, UK
| | | | | |
Collapse
|
12
|
Numachi Y, Yoshida S, Yamashita M, Fujiyama K, Toda S, Matsuoka H, Kajii Y, Nishikawa T. Altered EphA5 mRNA expression in rat brain with a single methamphetamine treatment. Neurosci Lett 2007; 424:116-21. [PMID: 17714871 DOI: 10.1016/j.neulet.2007.07.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 07/08/2007] [Accepted: 07/23/2007] [Indexed: 11/25/2022]
Abstract
Methamphetamine is a potent and indirect dopaminergic agonist which can cause chronic brain dysfunctions including drug abuse, drug dependence and drug-induced psychosis. Methamphetamine is known to trigger molecular mechanisms involved in associative learning and memory, and thereby alter patterns of synaptic connectivity. The persistent risk of relapse in methamphetamine abuse, dependence and psychosis may be caused by such alterations in synaptic connectivity. EphA5 receptors constitute large families of tyrosine kinase receptor and are expressed almost exclusively in the nervous system, especially in the limbic structures. Recent studies suggest EphA5 to be important in the topographic projection, development, and plasticity of limbic structures, and to be involved in dopaminergic neurotransmission. We used in situ hybridization to examine whether methamphetamine alters EphA5 mRNA expression in the brains of adult male Wister rats. EphA5 mRNA was widely distributed in the medial frontal cortex, cingulate cortex, piriform cortex, hippocampus, habenular nucleus and amygdala. Compared to baseline expression at 0h, EphA5 mRNA was significantly decreased (by 20%) in the medial frontal cortex at 24h, significantly increased (by 30%) in the amygdala at 9 and 24h, significantly but transiently decreased (by 30%) in the habenular nucleus at 1h after a single injection of methamphetamine. Methamphetamine did not change EphA5 mRNA expression in the cingulate cortex, piriform cortex or hippocampus. Our results that methamphetamine altered EphA5 mRNA expression in rat brain suggest methamphetamine could affect patterns of synaptic connectivity, which might be responsible for methamphetamine-induced chronic brain dysfunctions.
Collapse
Affiliation(s)
- Yohtaro Numachi
- Musashi Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
13
|
Abstract
The Eph receptor tyrosine kinases and their membrane-bound ligands, the ephrins, are involved in a variety of developmental processes such as axonal guidance, cell migration, cell adhesion, proliferation, and differentiation. In addition to repulsive effects, ephrins can also induce attractive responses. Up to now, little was known about the underlying signaling mechanisms that regulate attractive versus repulsive effects. In this study, we show that ephrin-A5 enhances the motility of cortical neurons that is dependent on the activity of Src-family kinases (SFKs). Ephrin-A5 further changes the adhesive properties of neurons by inducing the formation of cell aggregates. Using the stripe assay, we found that the motogenic effect of ephrin-A5 is the result of repulsive ephrin-A interactions. Blocking SFK function leads to a conversion of repulsion into adhesion, suggesting that SFKs can act as a biological switch for the response of EphA receptors. Finally, we discovered a ligand-induced release of membrane particles containing EphA receptors, suggesting membrane ripping as a novel mechanism to overcome the "ephrin paradox" of repulsion after high-affinity receptor-ligand binding.
Collapse
Affiliation(s)
| | | | - Franco Weth
- Nachwuchsgruppe Neurogenetik, Theoretikum, Universität Jena, 07743 Jena, Germany
| | - Jürgen Bolz
- Institut für Allgemeine Zoologie und Tierphysiologie and
| |
Collapse
|
14
|
Abstract
Two new studies report how discrete identities of olfactory sensory neurons are converted into a spatial map of axonal connections (Imai et al., 2006; Serizawa et al., 2006). They find that levels of cAMP signals derived from olfactory receptors (ORs) can direct targeting of axons along an axis, and that ORs and neural activity regulate expression of adhesion/guidance molecules in mosaic patterns that can sort axons into discrete locations.
Collapse
Affiliation(s)
- Yao Chen
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | | |
Collapse
|
15
|
Serizawa S, Miyamichi K, Takeuchi H, Yamagishi Y, Suzuki M, Sakano H. A Neuronal Identity Code for the Odorant Receptor-Specific and Activity-Dependent Axon Sorting. Cell 2006; 127:1057-69. [PMID: 17129788 DOI: 10.1016/j.cell.2006.10.031] [Citation(s) in RCA: 245] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Revised: 09/14/2006] [Accepted: 10/18/2006] [Indexed: 10/23/2022]
Abstract
In the mouse, olfactory sensory neurons (OSNs) expressing the same odorant receptor (OR) converge their axons to a specific set of glomeruli in the olfactory bulb. To study how OR-instructed axonal fasciculation is controlled, we searched for genes whose expression profiles are correlated with the expressed ORs. Using the transgenic mouse in which the majority of OSNs express a particular OR, we identified such genes coding for the homophilic adhesive molecules Kirrel2/Kirrel3 and repulsive molecules ephrin-A5/EphA5. In the CNGA2 knockout mouse, where the odor-evoked cation influx is disrupted, Kirrel2 and EphA5 were downregulated, while Kirrel3 and ephrin-A5 were upregulated, indicating that these genes are transcribed in an activity-dependent manner. Mosaic analysis demonstrated that gain of function of these genes generates duplicated glomeruli. We propose that a specific set of adhesive/repulsive molecules, whose expression levels are determined by OR molecules, regulate the axonal fasciculation of OSNs during the process of glomerular map formation.
Collapse
Affiliation(s)
- Shou Serizawa
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Tokyo 113-0032, Japan
| | | | | | | | | | | |
Collapse
|
16
|
Martínez A, Otal R, Sieber BA, Ibáñez C, Soriano E. Disruption of ephrin-A/EphA binding alters synaptogenesis and neural connectivity in the hippocampus. Neuroscience 2006; 135:451-61. [PMID: 16112477 DOI: 10.1016/j.neuroscience.2005.06.052] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Revised: 05/26/2005] [Accepted: 06/15/2005] [Indexed: 11/26/2022]
Abstract
Ephrins are guidance cues that modulate axonal growth and the subsequent axonal topographic maps in many regions of the CNS. Here we studied the functional roles of ephrin-A/EphA interactions in the layer-specific pattern of axonal projections in the hippocampus by disrupting the ephrin-A signaling by over-expression of a soluble EphA receptor. Tracing experiments in EphA5-Fc over-expressing mice revealed that reduction of ephrin-A/EphA interactions did not affect the proper distribution of the main hippocampal afferents, i.e. entorhinal and commissural projections. However, further ultrastructural analyses showed a reduction in the density of synaptic terminals in the entorhinal and commissural termination layers in these mice. In addition, using anti-calbindin antibodies, we analyzed the dentate mossy fiber projections following disruption of ephrin-A/EphA interactions throughout developing hippocampus. While the main mossy fiber bundle appeared normal, the infrapyramidal bundle formed longer projections that established ectopic contacts in these transgenic mice. Later, the expected specific pruning of the infrapyramidal bundle was not observed at adult stages. Ultrastructural analyses confirmed a higher number of mossy fiber terminals in the infrapyramidal bundle in adult EphA5-Fc transgenic mice and showed that these terminals were larger and established a greater number of contacts than in controls. Our results demonstrate that ephrin-A/EphA interactions regulate the synaptogenesis of hippocampal afferents and the proper development and refinement of granule cell projections.
Collapse
Affiliation(s)
- A Martínez
- Department of Cell Biology and Barcelona Science Park (IRBB), University of Barcelona, Barcelona 08028, Spain.
| | | | | | | | | |
Collapse
|
17
|
Torii M, Levitt P. Dissociation of corticothalamic and thalamocortical axon targeting by an EphA7-mediated mechanism. Neuron 2006; 48:563-75. [PMID: 16301174 DOI: 10.1016/j.neuron.2005.09.021] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2005] [Revised: 08/01/2005] [Accepted: 09/12/2005] [Indexed: 10/25/2022]
Abstract
Molecular mechanisms generating the topographic organization of corticothalamic (CT) circuits, which comprise more than three-quarters of the synaptic inputs onto sensory relay neurons, and their interdependence with thalamocortical (TC) axon development are unknown. Using in utero electroporation-mediated gene transfer, we show that EphA7-mediated signaling on neocortical axons controls the within-nucleus topography of CT projections in the thalamus. Notably, CT axons that mis-express EphA7 do not shift the relative positioning of their pathway within the subcortical telencephalon (ST), indicating that they do not depend upon EphA7/ephrin-A signaling in the ST for establishing this topography. Moreover, mis-expression of cortical EphA7 results in disrupted topography of CT projections, but unchanged inter- and intra-areal topography of TC projections. Our results support a model in which EphA/ephrin-A signaling controls independently the precision with which CT and TC projections develop, yet is essential for establishing their topographic reciprocity.
Collapse
Affiliation(s)
- Masaaki Torii
- Vanderbilt Kennedy Center for Research on Human Development and Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37203, USA
| | | |
Collapse
|
18
|
Gamble JA, Karunadasa DK, Pape JR, Skynner MJ, Todman MG, Bicknell RJ, Allen JP, Herbison AE. Disruption of ephrin signaling associates with disordered axophilic migration of the gonadotropin-releasing hormone neurons. J Neurosci 2005; 25:3142-50. [PMID: 15788771 PMCID: PMC6725091 DOI: 10.1523/jneurosci.4759-04.2005] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2004] [Revised: 02/10/2005] [Accepted: 02/11/2005] [Indexed: 11/21/2022] Open
Abstract
Ephrin signaling is involved in repulsive and attractive interactions mediating axon guidance and cell-boundary formation in the developing nervous system. As a result of a fortuitous transgene integration event, we have identified here a potential role for EphA5 in the axophilic migration of gonadotropin-releasing hormone (GnRH) neurons from the nasal placode into the brain along ephrin-expressing vomeronasal axons. Transgene integration in the GNR23 mouse line resulted in a 26 kb deletion in chromosome 5, approximately 67 kb 3' to Epha5. This induced a profound, region-specific upregulation of EphA5 mRNA and protein expression in the developing mouse brain. The GnRH neurons in GNR23 mice overexpressed EphA5 from embryonic day 11, whereas ephrin A3 and A5 mRNA levels in olfactory neurons were unchanged. The GnRH neurons were found to be slow in commencing their migration from the olfactory placode and also to form abnormal clusters of cells on the olfactory axons, prohibiting their migration out of the nose. As a result, adult hemizygous mice had only 40% of the normal complement of GnRH neurons in the brain, whereas homozygous mice had <15%. This resulted in infertility in adult female homozygous GNR23 mice, suggesting that some cases of human hypogonadotropic hypogonadism may result from ephrin-related mutations. These data provide evidence for a role of EphA-ephrin signaling in the axophilic migration of the GnRH neurons during embryogenesis.
Collapse
Affiliation(s)
- John A Gamble
- Neurobiology Programme, The Babraham Institute, Cambridge CB2 4AT, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
19
|
Yun ME, Johnson RR, Antic A, Donoghue MJ. EphA family gene expression in the developing mouse neocortex: regional patterns reveal intrinsic programs and extrinsic influence. J Comp Neurol 2003; 456:203-16. [PMID: 12528186 DOI: 10.1002/cne.10498] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Parcellation of the mammalian cerebral cortex into distinct areas is essential for proper cortical function; however, the developmental program that results in the genesis of distinct areas is not fully understood. We examined the expression of members of the EphA family-the EphA receptor tyrosine kinases and the ephrin-A ligands-within the developing mouse cerebral cortex, with the aim of characterizing this component of the molecular landscape during cortical parcellation. We found that specific embryonic zones, such as the ventricular, subventricular, intermediate, subplate, and marginal zones, as well as the cortical plate, were positive for particular EphA genes early in corticogenesis (E12-E15). Along with this zone-selective expression, several genes (EphA3, EphA4, EphA5) were evenly expressed along the axes of the developing cortex, whereas one family member (EphA7) was expressed in a distinct anteroposterior pattern. Later in corticogenesis (E16-E18), other EphA family members became selectively expressed, but only within the cortical plate: EphA6 was present posteriorly, and ephrin-A5 was expressed within a middle region. At birth, patterning of EphA gene expression was striking. Thus, we found that the expression of a single EphA gene or a combination of family members can define distinct embryonic zones and anteroposterior regions of the neocortex during development. To examine whether cellular context affects the patterning of EphA expression, we examined gene expression in embryonic cortical cells grown in vitro, such that all cellular contacts are lacking, and in Mash-1 mutant mice, in which thalamocortical connections do not form. We found that the expression patterns of most EphA family members remained stable in these scenarios, whereas the pattern of ephrin-A5 was altered. Taken together, this work provides a comprehensive picture of EphA family expression during mouse corticogenesis and demonstrates that most EphA expression profiles are cell intrinsically based, whereas ephrin-A5 is plastically regulated.
Collapse
Affiliation(s)
- Mihae E Yun
- Section of Neurobiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA
| | | | | | | |
Collapse
|