1
|
Ebert O, Bohn B, Bertram B, Buchberger B, Finck H, Hoß J, Hübner P, Krabbe L, Kulzer B, Küstner E, Lachenmayr B, Lemmen KD, Petry F, Rinnert K, Salomon M, Schütt W, Holl RW, Maxeiner S, Wagener W. Diabetes and Road Traffic. Exp Clin Endocrinol Diabetes 2024. [PMID: 38395055 DOI: 10.1055/a-2166-6928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/25/2024]
Affiliation(s)
- Oliver Ebert
- REK Attorneys at Law, Stuttgart, Balingen, Germany
| | - Barbara Bohn
- Institute for Epidemiology and Medical Biometry, ZIBMT, University of Ulm, Germany
- German National Cohort (NAKO Gesundheitsstudie/NAKO), Heidelberg, Germany
| | - Bernd Bertram
- Ophthalmological Practice Prof. Bertram & Dr. Helg, Aachen, Germany
| | | | | | - Jürgen Hoß
- Specialist Practice Dr. Rainer Möllmann and Dr. Jürgen Hoß, Krefeld, Germany
| | | | - Laura Krabbe
- Chair of Medical Management, Faculty of Economics, University of Duisburg-Essen, Campus Essen, Germany
| | - Bernhard Kulzer
- Research Institute of the Diabetes Academy Bad Mergentheim (FIDAM GmbH), Bad Mergentheim, Germany
| | | | - Bernhard Lachenmayr
- Ophthalmology Clinic Prof. Dr. Dr. Bernhard Lachenmayr & PD Dr. Lukas Reznicek, Munich, Germany
| | | | | | - Kurt Rinnert
- Company Medical Service, City of Cologne, Germany
| | - Markus Salomon
- Diabetes Specialist Practice and Center for Nutritional Medicine, Medicum Hamburg, Germany
| | | | - Reinhard W Holl
- Institute for Epidemiology and Medical Biometry, ZIBMT, University of Ulm, Germany
| | | | | |
Collapse
|
2
|
Hollenhorst MI, Husnik T, Zylka M, Duda N, Flockerzi V, Tschernig T, Maxeiner S, Krasteva-Christ G. Human airway tuft cells influence the mucociliary clearance through cholinergic signalling. Respir Res 2023; 24:267. [PMID: 37925434 PMCID: PMC10625704 DOI: 10.1186/s12931-023-02570-8] [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: 08/14/2023] [Accepted: 10/20/2023] [Indexed: 11/06/2023] Open
Abstract
BACKGROUND Airway tuft cells, formerly called brush cells have long been described only morphologically in human airways. More recent RNAseq studies described a chemosensory cell population, which includes tuft cells, by a distinct gene transcription signature. Yet, until which level in the tracheobronchial tree in native human airway epithelium tuft cells occur and if they function as regulators of innate immunity, e.g., by regulating mucociliary clearance, remained largely elusive. METHODS We performed immunohistochemistry, RT-PCR and immunoblotting analyses for various tuft cell markers to confirm the presence of this cell type in human tracheal samples. Immunohistochemistry was conducted to study the distribution of tuft cells along the intrapulmonary airways in humans. We assessed the influence of bitter substances and the taste transduction pathway on mucociliary clearance in mouse and human tracheal samples by measuring particle transport speed. RESULTS Tuft cells identified by the expression of their well-established marker POU class 2 homeobox 3 (POU2F3) were present from the trachea to the bronchioles. We identified choline acetyltransferase in POU2F3 expressing cells as well as the transient receptor potential melastatin 5 (TRPM5) channel in a small population of tracheal epithelial cells with morphological appearance of tuft cells. Application of bitter substances, such as denatonium, led to an increase in mucociliary clearance in human tracheal preparations. This was dependent on activation of the TRPM5 channel and involved cholinergic and nitric oxide signalling, indicating a functional role for human tuft cells in the regulation of mucociliary clearance. CONCLUSIONS We were able to detect tuft cells in the tracheobronchial tree down to the level of the bronchioles. Moreover, taste transduction and cholinergic signalling occur in the same cells and regulate mucociliary clearance. Thus, tuft cells are potentially involved in the regulation of innate immunity in human airways.
Collapse
Affiliation(s)
| | - Thomas Husnik
- Institute of Anatomy and Cell Biology, Saarland University, Homburg, Germany
| | - Malin Zylka
- Institute of Anatomy and Cell Biology, Saarland University, Homburg, Germany
| | - Nele Duda
- Institute of Anatomy and Cell Biology, Saarland University, Homburg, Germany
| | - Veit Flockerzi
- Institute for Experimental and Clinical Pharmacology and Toxicology, Preclinical Center for Molecular Signaling, Saarland University, Homburg, Germany
| | - Thomas Tschernig
- Institute of Anatomy and Cell Biology, Saarland University, Homburg, Germany
| | - Stephan Maxeiner
- Institute of Anatomy and Cell Biology, Saarland University, Homburg, Germany
| | | |
Collapse
|
3
|
Trotter JH, Hao J, Maxeiner S, Tsetsenis T, Liu Z, Zhuang X, Südhof TC. Correction: Synaptic neurexin-1 assembles into dynamically regulated active zone nanoclusters. J Cell Biol 2023; 222:e20181207608242023c. [PMID: 37665610 PMCID: PMC10477082 DOI: 10.1083/jcb.20181207608242023c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2023] Open
|
4
|
Maxeiner S, Krasteva-Christ G, Althaus M. Pitfalls of using sequence databases for heterologous expression studies - a technical review. J Physiol 2023; 601:1611-1623. [PMID: 36762618 DOI: 10.1113/jp284066] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 02/07/2023] [Indexed: 02/11/2023] Open
Abstract
Synthesis of DNA fragments based on gene sequences that are available in public resources has become an efficient and affordable method that has gradually replaced traditional cloning efforts such as PCR cloning from cDNA. However, database entries based on genome sequencing results are prone to errors which can lead to false sequence information and, ultimately, errors in functional characterisation of proteins such as ion channels and transporters in heterologous expression systems. We have identified five common problems that repeatedly appear in public resources: (1) Not every gene has yet been annotated; (2) not all gene annotations are necessarily correct; (3) transcripts may contain automated corrections; (4) there are mismatches between gene, mRNA and protein sequences; and (5) splicing patterns often lack experimental validation. This technical review highlights and provides a strategy to bypass these issues in order to avoid critical mistakes that could impact future studies of any gene/protein of interest in heterologous expression systems.
Collapse
Affiliation(s)
- Stephan Maxeiner
- Institute for Anatomy and Cell Biology, Saarland University, Homburg, Germany
| | | | - Mike Althaus
- Department of Natural Sciences, Institute for Functional Gene Analytics, Bonn-Rhein-Sieg University of Applied Sciences, Rheinbach, Germany
| |
Collapse
|
5
|
Hollenhorst MI, Kumar P, Zimmer M, Salah A, Maxeiner S, Elhawy MI, Evers SB, Flockerzi V, Gudermann T, Chubanov V, Boehm U, Krasteva-Christ G. Taste Receptor Activation in Tracheal Brush Cells by Denatonium Modulates ENaC Channels via Ca2+, cAMP and ACh. Cells 2022; 11:cells11152411. [PMID: 35954259 PMCID: PMC9367940 DOI: 10.3390/cells11152411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 06/22/2022] [Revised: 07/23/2022] [Accepted: 08/03/2022] [Indexed: 02/04/2023] Open
Abstract
Mucociliary clearance is a primary defence mechanism of the airways consisting of two components, ciliary beating and transepithelial ion transport (ISC). Specialised chemosensory cholinergic epithelial cells, named brush cells (BC), are involved in regulating various physiological and immunological processes. However, it remains unclear if BC influence ISC. In murine tracheae, denatonium, a taste receptor agonist, reduced basal ISC in a concentration-dependent manner (EC50 397 µM). The inhibition of bitter taste signalling components with gallein (Gβγ subunits), U73122 (phospholipase C), 2-APB (IP3-receptors) or with TPPO (Trpm5, transient receptor potential-melastatin 5 channel) reduced the denatonium effect. Supportively, the ISC was also diminished in Trpm5−/− mice. Mecamylamine (nicotinic acetylcholine receptor, nAChR, inhibitor) and amiloride (epithelial sodium channel, ENaC, antagonist) decreased the denatonium effect. Additionally, the inhibition of Gα subunits (pertussis toxin) reduced the denatonium effect, while an inhibition of phosphodiesterase (IBMX) increased and of adenylate cyclase (forskolin) reversed the denatonium effect. The cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor CFTRinh172 and the KCNQ1 potassium channel antagonist chromanol 293B both reduced the denatonium effect. Thus, denatonium reduces ISC via the canonical bitter taste signalling cascade leading to the Trpm5-dependent nAChR-mediated inhibition of ENaC as well as Gα signalling leading to a reduction in cAMP-dependent ISC. Therefore, BC activation contributes to the regulation of fluid homeostasis.
Collapse
Affiliation(s)
| | - Praveen Kumar
- Institute of Anatomy and Cell Biology, Saarland University, 66421 Homburg, Germany
| | - Maxim Zimmer
- Institute of Anatomy and Cell Biology, Saarland University, 66421 Homburg, Germany
| | - Alaa Salah
- Institute of Anatomy and Cell Biology, Saarland University, 66421 Homburg, Germany
| | - Stephan Maxeiner
- Institute of Anatomy and Cell Biology, Saarland University, 66421 Homburg, Germany
| | | | - Saskia B. Evers
- Institute of Anatomy and Cell Biology, Saarland University, 66421 Homburg, Germany
| | - Veit Flockerzi
- Institute for Experimental and Clinical Pharmacology and Toxicology, Centre for Molecular Signalling, Saarland University, 66421 Homburg, Germany
| | - Thomas Gudermann
- Walter-Straub-Institute for Pharmacology and Toxicology, Ludwig-Maximilians-University and German Centre for Lung Research (DZL), 80366 Munich, Germany
| | - Vladimir Chubanov
- Walter-Straub-Institute for Pharmacology and Toxicology, Ludwig-Maximilians-University and German Centre for Lung Research (DZL), 80366 Munich, Germany
| | - Ulrich Boehm
- Experimental Pharmacology, Centre for Molecular Signalling, School of Medicine, Saarland University, 66421 Homburg, Germany
| | - Gabriela Krasteva-Christ
- Institute of Anatomy and Cell Biology, Saarland University, 66421 Homburg, Germany
- Correspondence: ; Tel.: +49-6841-16-26101
| |
Collapse
|
6
|
Maxeiner S, Benseler F, Brose N, Krasteva-Christ G. Of Humans and Gerbils— Independent Diversification of Neuroligin-4 Into X- and Y-Specific Genes in Primates and Rodents. Front Mol Neurosci 2022; 15:838262. [PMID: 35431802 PMCID: PMC9005811 DOI: 10.3389/fnmol.2022.838262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 02/03/2022] [Indexed: 11/13/2022] Open
Abstract
The neural cell adhesion protein neuroligin-4 has puzzled neuroscientists and geneticist alike for almost two decades. Its clinical association with autism spectrum disorders (ASD) is well established, however, its diversification into sex chromosome-specific copies, NLGN4X and NLGN4Y, remains uncharted territory. Just recently, the presence of substantial neuroligin-4 sequence differences between humans and laboratory mice, in which Nlgn4 is a pseudoautosomal gene, could be explained as a consequence of dramatic changes affecting the pseudoautosomal region on both sex chromosomes in a subset of rodents, the clade eumuroida. In this study, we describe the presence of sex chromosome-specific copies of neuroligin-4 genes in the Mongolian gerbil (Meriones unguiculatus) marking the first encounter of its kind in rodents. Gerbils are members of the family Muridae and are closely related to mice and rats. Our results have been incorporated into an extended evolutionary analysis covering primates, rodents, lagomorphs, treeshrews and culogos comprising together the mammalian superorder euarchontoglires. We gathered evidence that substantial changes in neuroligin-4 genes have also occurred outside eumuroida in other rodent species as well as in lagomorphs. These changes feature, e.g., a general reduction of its gene size, an increase in its average GC-content as well as in the third position (GC3) of synonymous codons, and the accumulation of repetitive sequences in line with previous observations. We further show conclusively that the diversification of neuroligin-4 in sex chromosome-specific copies has happened multiple times independently during mammal evolution proving that Y-chromosomal NLGN4Y genes do not originate from a single common NLGN4Y ancestor.
Collapse
Affiliation(s)
- Stephan Maxeiner
- Anatomy and Cell Biology, Saarland University, Homburg, Germany
- *Correspondence: Stephan Maxeiner,
| | - Fritz Benseler
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | | |
Collapse
|
7
|
Shankhwar S, Schwarz K, Katiyar R, Jung M, Maxeiner S, Südhof TC, Schmitz F. RIBEYE B-Domain Is Essential for RIBEYE A-Domain Stability and Assembly of Synaptic Ribbons. Front Mol Neurosci 2022; 15:838311. [PMID: 35153673 PMCID: PMC8831697 DOI: 10.3389/fnmol.2022.838311] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 01/03/2022] [Indexed: 01/17/2023] Open
Abstract
Synaptic ribbons are presynaptic specializations that define eponymous ribbon synapses. Synaptic ribbons are largely composed of RIBEYE, a protein containing an N-terminal A-domain and a carboxyterminal B-domain that is identical with CtBP2, a NAD(H)-binding transcriptional co-repressor. Previously we showed that synaptic ribbons are completely absent in RIBEYE knockout mice in which the RIBEYE A-domain-encoding exon had been deleted, but CtBP2 is still made, demonstrating that the A-domain is required for synaptic ribbon assembly. In the present study, we asked whether the RIBEYE B-domain also has an essential role in the assembly of synaptic ribbons. For this purpose, we made use of RIBEYE knockin mice in which the RIBEYE B-domain was replaced by a fluorescent protein domain, whereas the RIBEYE A-domain was retained unchanged. We found that replacing the RIBEYE B-domain with a fluorescent protein module destabilizes the resulting hybrid protein and causes a complete loss of synaptic ribbons. Our results thus demonstrate an essential role of the RIBEYE B-domain in enabling RIBEYE assembly into synaptic ribbons, reinforcing the notion that RIBEYE is the central organizer of synaptic ribbons.
Collapse
Affiliation(s)
- Soni Shankhwar
- Institute of Anatomy and Cell Biology, Saarland University, Medical School, Homburg, Germany
- *Correspondence: Soni Shankhwar Frank Schmitz
| | - Karin Schwarz
- Institute of Anatomy and Cell Biology, Saarland University, Medical School, Homburg, Germany
| | - Rashmi Katiyar
- Institute of Anatomy and Cell Biology, Saarland University, Medical School, Homburg, Germany
| | - Martin Jung
- Institute of Medical Biochemistry and Molecular Biology, Saarland University, Medical School, Homburg, Germany
| | - Stephan Maxeiner
- Institute of Anatomy and Cell Biology, Saarland University, Medical School, Homburg, Germany
| | - Thomas C. Südhof
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, United States
| | - Frank Schmitz
- Institute of Anatomy and Cell Biology, Saarland University, Medical School, Homburg, Germany
- *Correspondence: Soni Shankhwar Frank Schmitz
| |
Collapse
|
8
|
Gettings SM, Maxeiner S, Tzika M, Cobain MRD, Ruf I, Benseler F, Brose N, Krasteva-Christ G, Vande Velde G, Schönberger M, Althaus M. Corrigendum to: Two Functional Epithelial Sodium Channel Isoforms Are Present in Rodents despite Pronounced Evolutionary Pseudogenization and Exon Fusion. Mol Biol Evol 2021; 39:6460366. [PMID: 34897515 PMCID: PMC8861876 DOI: 10.1093/molbev/msab328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
9
|
Gettings SM, Maxeiner S, Tzika M, Cobain MRD, Ruf I, Benseler F, Brose N, Krasteva-Christ G, Vande Velde G, Schönberger M, Althaus M. Two functional epithelial sodium channel isoforms are present in rodents despite pronounced evolutionary pseudogenisation and exon fusion. Mol Biol Evol 2021; 38:5704-5725. [PMID: 34491346 PMCID: PMC8662647 DOI: 10.1093/molbev/msab271] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The epithelial sodium channel (ENaC) plays a key role in salt and water homeostasis in
tetrapod vertebrates. There are four ENaC subunits (α, β, γ, δ), forming heterotrimeric
αβγ- or δβγ-ENaCs. Although the physiology of αβγ-ENaC is well understood, for decades the
field has stalled with respect to δβγ-ENaC due to the lack of mammalian model organisms.
The SCNN1D gene coding for δ-ENaC was previously believed to be absent in
rodents, hindering studies using standard laboratory animals. We analyzed all currently
available rodent genomes and discovered that SCNN1D is present in rodents
but was independently lost in five rodent lineages, including the Muridae (mice and rats).
The independent loss of SCNN1D in rodent lineages may be constrained by
phylogeny and taxon-specific adaptation to dry habitats, however habitat aridity does not
provide a selection pressure for maintenance of SCNN1D across Rodentia. A
fusion of two exons coding for a structurally flexible region in the extracellular domain
of δ-ENaC appeared in the Hystricognathi (a group that includes guinea pigs). This
conserved pattern evolved at least 41 Ma and represents a new autapomorphic feature for
this clade. Exon fusion does not impair functionality of guinea pig (Cavia
porcellus) δβγ-ENaC expressed in Xenopus oocytes.
Electrophysiological characterization at the whole-cell and single-channel level revealed
conserved biophysical features and mechanisms controlling guinea pig αβγ- and δβγ-ENaC
function as compared with human orthologs. Guinea pigs therefore represent commercially
available mammalian model animals that will help shed light on the physiological function
of δ-ENaC.
Collapse
Affiliation(s)
- Sean M Gettings
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom.,Biomedical Imaging, Department of Imaging and Pathology, Faculty of Medicine, KU Leuven, Belgium
| | - Stephan Maxeiner
- Institute for Anatomy and Cell Biology, Saarland University School of Medicine, Homburg, Germany
| | - Maria Tzika
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Matthew R D Cobain
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Irina Ruf
- Division of Messel Research and Mammalogy, Senckenberg Research Institute and Natural History Museum Frankfurt, Frankfurt am Main, Germany
| | - Fritz Benseler
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Gabriela Krasteva-Christ
- Institute for Anatomy and Cell Biology, Saarland University School of Medicine, Homburg, Germany
| | - Greetje Vande Velde
- Biomedical Imaging, Department of Imaging and Pathology, Faculty of Medicine, KU Leuven, Belgium
| | - Matthias Schönberger
- Biomedical Imaging, Department of Imaging and Pathology, Faculty of Medicine, KU Leuven, Belgium
| | - Mike Althaus
- Institute for Functional Gene Analytics, Department of Natural Sciences, Bonn-Rhein-Sieg University of Applied Sciences, Rheinbach, Germany
| |
Collapse
|
10
|
Maxeiner S, Benseler F, Krasteva-Christ G, Brose N, Südhof TC. Evolution of the Autism-Associated Neuroligin-4 Gene Reveals Broad Erosion of Pseudoautosomal Regions in Rodents. Mol Biol Evol 2021; 37:1243-1258. [PMID: 32011705 PMCID: PMC7182215 DOI: 10.1093/molbev/msaa014] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Variants in genes encoding synaptic adhesion proteins of the neuroligin family, most notably neuroligin-4, are a significant cause of autism spectrum disorders in humans. Although human neuroligin-4 is encoded by two genes, NLGN4X and NLGN4Y, that are localized on the X-specific and male-specific regions of the two sex chromosomes, the chromosomal localization and full genomic sequence of the mouse Nlgn4 gene remain elusive. Here, we analyzed the neuroligin-4 genes of numerous rodent species by direct sequencing and bioinformatics, generated complete drafts of multiple rodent neuroligin-4 genes, and examined their evolution. Surprisingly, we find that the murine Nlgn4 gene is localized to the pseudoautosomal region (PAR) of the sex chromosomes, different from its human orthologs. We show that the sequence differences between various neuroligin-4 proteins are restricted to hotspots in which rodent neuroligin-4 proteins contain short repetitive sequence insertions compared with neuroligin-4 proteins from other species, whereas all other protein sequences are highly conserved. Evolutionarily, these sequence insertions initiate in the clade eumuroidea of the infraorder myomorpha and are additionally associated with dramatic changes in noncoding sequences and gene size. Importantly, these changes are not exclusively restricted to neuroligin-4 genes but reflect major evolutionary changes that substantially altered or even deleted genes from the PARs of both sex chromosomes. Our results show that despite the fact that the PAR in rodents and the neuroligin-4 genes within the rodent PAR underwent massive evolutionary changes, neuroligin-4 proteins maintained a highly conserved core structure, consistent with a substantial evolutionary pressure preserving its physiological function.
Collapse
Affiliation(s)
- Stephan Maxeiner
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA.,Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA.,Institute for Anatomy and Cell Biology, Saarland University, Homburg, Germany
| | - Fritz Benseler
- Department of Molecular Neurobiology, Max-Planck-Institute of Experimental Medicine, Göttingen, Germany
| | | | - Nils Brose
- Department of Molecular Neurobiology, Max-Planck-Institute of Experimental Medicine, Göttingen, Germany
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA.,Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA
| |
Collapse
|
11
|
Mani J, Fleger J, Rutz J, Maxeiner S, Bernd A, Kippenberger S, Zöller N, Chun FKH, Relja B, Juengel E, Blaheta RA. Curcumin combined with exposure to visible light blocks bladder cancer cell adhesion and migration by an integrin dependent mechanism. Eur Rev Med Pharmacol Sci 2020; 23:10564-10574. [PMID: 31841214 DOI: 10.26355/eurrev_201912_19698] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Although the natural compound curcumin exerts antitumor properties in vitro, its clinical application is hampered due to rapid metabolism. Light exposure following curcumin application has been demonstrated to improve curcumin's bioavailability. Therefore, this investigation was directed towards evaluating whether light exposure in addition to curcumin application enhances curcumin's efficacy against bladder cancer cell adhesion and migration. MATERIALS AND METHODS RT112, UMUC3, and TCCSUP cells were incubated with low curcumin concentrations (0.1-0.4 μg/ml) and then exposed to 1.65 J/cm2 visible light for 5 min. Controls remained untreated or were treated with curcumin or light alone. Cell adhesion to Human umbilical vein endothelial cells (HUVECs), to immobilized collagen or fibronectin and chemotactic behavior, integrin α and β receptor expression with functional relevance, as well as focal adhesion kinase (total and phosphorylated FAK) were evaluated. RESULTS Curcumin plus light, but neither curcumin nor light alone, significantly altered tumor cell adhesion and suppressed chemotaxis. Integrin α and β subtypes were dissimilarly modified, depending on the cell line. Suppression of pFAK was noted in RT112 and UMUC3, but not in TCCSUP cells. The integrins α3, α5, and β1 were involved in curcumin's regulation of adhesion and migration. Blocking studies revealed α3, α5, and β1 to be associated with TCCSUP adhesion and migration, whereas α5 and β1, but not α3 contributed to UMUC3 adhesion and migration. Integrin α5 and β1 controlled RT112 chemotaxis as well, but only α5 was involved in the RT112 adhesion process. CONCLUSIONS Combining curcumin with light exposure enhances curcumin's anti-tumor potential.
Collapse
Affiliation(s)
- J Mani
- Department of Urology, Goethe-University, Frankfurt am Main, Germany.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Fairless R, Williams SK, Katiyar R, Maxeiner S, Schmitz F, Diem R. ERG Responses in Mice with Deletion of the Synaptic Ribbon Component RIBEYE. Invest Ophthalmol Vis Sci 2020; 61:37. [PMID: 32437548 PMCID: PMC7405791 DOI: 10.1167/iovs.61.5.37] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Purpose To determine the influence of RIBEYE deletion and the resulting absence of synaptic ribbons on retinal light signaling by electroretinography. Methods Full-field flash electroretinograms (ERGs) were recorded in RIBEYE knock-out (KO) and wild-type (WT) littermate mice under photopic and scotopic conditions, with oscillatory potentials (OPs) extracted by digital filtering. Flicker ERGs and ERGs following intravitreal injection of pharmacological agents were also obtained under scotopic conditions. Results The a-wave amplitudes were unchanged between RIBEYE KO and WT mice; however, the b-wave amplitudes were reduced in KOs under scotopic, but not photopic, conditions. Increasing stimulation frequency led to a greater reduction in RIBEYE KO b-wave amplitudes compared with WTs. Furthermore, we observed prominent, supernormal OPs in RIBEYE KO mice in comparison with WT mice. Following intravitreal injections with l-2 amino-4-phosphonobutyric acid and cis-2,3 piperidine dicarboxylic acid to block ON and OFF responses at photoreceptor synapses, OPs were completely abolished in both mice types, indicating a synaptic origin of the prominent OPs in the KOs. Conversely, tetrodotoxin treatment to block voltage-gated Na+ channels/spiking neurons did not differentially affect OPs in WT and KO mice. Conclusions The decreased scotopic b-wave and decreased responses to increased stimulation frequencies are consistent with signaling malfunctions at photoreceptor and inner retinal ribbon synapses. Because phototransduction in the photoreceptor outer segments is unaffected in the KOs, their supernormal OPs presumably result from a dysfunction in retinal synapses. The relatively mild ERG phenotype in KO mice, particularly in the photopic range, is probably caused by compensatory mechanisms in retinal signaling pathways.
Collapse
|
13
|
Dembla E, Dembla M, Maxeiner S, Schmitz F. Synaptic ribbons foster active zone stability and illumination-dependent active zone enrichment of RIM2 and Cav1.4 in photoreceptor synapses. Sci Rep 2020; 10:5957. [PMID: 32249787 PMCID: PMC7136232 DOI: 10.1038/s41598-020-62734-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 03/18/2020] [Indexed: 02/08/2023] Open
Abstract
Rod photoreceptor synapses use large, ribbon-type active zones for continuous synaptic transmission during light and dark. Since ribbons are physically connected to the active zones, we asked whether illumination-dependent changes of ribbons influence Cav1.4/RIM2 protein clusters at the active zone and whether these illumination-dependent effects at the active zone require the presence of the synaptic ribbon. We found that synaptic ribbon length and the length of presynaptic Cav1.4/RIM2 clusters are tightly correlated. Dark-adaptation did not change the number of ribbons and active zone puncta. However, mean ribbon length and length of presynaptic Cav1.4/RIM2 clusters increased significantly during dark-adaptation when tonic exocytosis is highest. In the present study, we identified by the analyses of synaptic ribbon-deficient RIBEYE knockout mice that synaptic ribbons are (1) needed to stabilize Cav1.4/RIM2 at rod photoreceptor active zones and (2) are required for the darkness-induced active zone enrichment of Cav1.4/RIM2. These data propose a role of the ribbon in active zone stabilization and suggest a homeostatic function of the ribbon in illumination-dependent active zone remodeling.
Collapse
Affiliation(s)
- Ekta Dembla
- Institute of Anatomy and Cell Biology, Department of Neuroanatomy, Saarland University, Medical School, 66421, Homburg, Germany.
| | - Mayur Dembla
- Institute of Anatomy and Cell Biology, Department of Neuroanatomy, Saarland University, Medical School, 66421, Homburg, Germany
| | - Stephan Maxeiner
- Institute of Anatomy and Cell Biology, Department of Neuroanatomy, Saarland University, Medical School, 66421, Homburg, Germany
- Institute of Anatomy and Cell Biology, Saarland University, AG Krasteva-Christ, 66421, Homburg, Germany
| | - Frank Schmitz
- Institute of Anatomy and Cell Biology, Department of Neuroanatomy, Saarland University, Medical School, 66421, Homburg, Germany.
| |
Collapse
|
14
|
Maxeiner S, Sester M, Krasteva-Christ G. Novel human sex-typing strategies based on the autism candidate gene NLGN4X and its male-specific gametologue NLGN4Y. Biol Sex Differ 2019; 10:62. [PMID: 31852540 PMCID: PMC6921425 DOI: 10.1186/s13293-019-0279-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 12/09/2019] [Indexed: 12/17/2022] Open
Abstract
Background Since the early days of PCR techniques, sex identification, “sex-typing,” of genomic DNA samples has been a fundamental part of human forensic analysis but also in animal genetics aiming at strategic livestock breeding. Most analyses are employing the AMELX/AMELY gene loci on the X and Y chromosomes present in most mammals. We hypothesize that sex-typing in humans is also possible based on the genes NLGN4X and NLGN4Y, which represent X and Y chromosome-specific copies of a common ancestral neuroligin-4 orthologue. Methods Genomic DNA was isolated from human blood and buccal cell samples (total n = 111) and submitted to two different strategies: (a) a traditional two-primer PCR approach detecting an insertion/deletion (indel) polymorphism immediately upstream of the translational start on exon 1 and (b) detection of a single nucleotide polymorphism, SNP, on the translational stop carrying exon 7. The SNP detection was based on a quantitative PCR approach (rhAMP genotyping) employing DNA/RNA hybrid oligonucleotides that were blocked and which could only be activated upon perfect annealing to the target DNA sequence. Results All indel PCR-tested human DNA samples showed two bands for males representing X- and Y-specific copies of NLGN4 and a single band for female samples, i.e., homozygosity of NLGN4X and absence of NLGN4Y, in accordance with the self-reported sex of the donors. These results were in perfect agreement with the results of the rhAMP-based SNP-detection method: all males were consequently positive for both alleles, representing either SNP variant, and females were interpreted as homozygous regarding the SNP variant found in NLGN4X. Both methods have shown reliable and consistent results that enabled us to infer the sex of donor DNA samples across different ethnicities. Conclusions These results indicate that the detection of human NLGN4X/Y is a suitable alternative to previously reported methods employing gene loci such as AMELX/Y. Furthermore, this is the first report applying successfully the rhAMP-genotyping strategy as a means for SNP-based sex-typing, which consequently will be applicable to other gene loci or different species as well.
Collapse
Affiliation(s)
- Stephan Maxeiner
- Institute of Anatomy and Cell Biology, Saarland University, Homburg, Germany.
| | - Martina Sester
- Department of Transplant and Infection Immunology, Saarland University, Homburg, Germany
| | | |
Collapse
|
15
|
Schutt KA, Maxeiner S, Lysaja K, Berger M, Ruetten S, Boor P, Marx N. 3309Complement activation leads to C3 and C5 dependent prothrombotic alterations of fibrin clots. Eur Heart J 2019. [DOI: 10.1093/eurheartj/ehz745.0073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Background and aims
Alterations of clot structure with thin fibres, small pores and prolonged fibrinolysis are associated with an increased cardiovascular risk. We previously demonstrated complement C3 to be incorporated into fibrin clots resulting in prolongation of fibrinolysis, an effect which was exaggerated in patients with diabetes. Patients with diabetes are known to display higher levels of complement activation. However, the role of complement activation in particular activation of C3 and C5 on clot lysis time remains unexplored. Thus, the present study seeks to determine whether activation of complement C3 and C5 by cobra venom factor (CVF) has an impact on fibrin clot structure and clot lysis.
Materials and methods
Fibrin clot structure and lysis were determined in a plasma pool of healthy controls in the presence and absence of the complement C3 and C5 activator CVF using a validated turbidimetric assay and scanning electron microscopy. C3 activation was inhibited by the addition of the small 14-AA-peptide Cp40, while C5 activation was blocked by the addition of the FDA approved monoclonal antibody eculizumab (Emab).
Results
Complement activation with CVF leads to a prothrombotic clot structure with thinner fibres (Co 0.20±0.001 au, CVF 0.13±0.001 au; p<0.0001) and prolongation of clot lysis time (Co 864±32 sec, CVF 1665±17 sec; p<0.0001), which was confirmed by electron microscopy (Co 94.7±1.44 nm, CVF 60.7±0.96 nm; p<0.0001). Inhibition of C3 activation by Cp40 improved clot structure resulting in thicker fibres (Co 0.20±0.001 au, CVF 0.13±0.001 au, CP40 0.20±0.002 au; p<0.0001) and shorter clot lysis time (Co 100%, CVF 181±8.9%, CP40 139±7.8%; p<0.0001), while scrambled protein had no effect on either clot structure or lysis time. As CVF can also activate C5 convertase we next investigated the inhibition of complement C5 activation with eculizumab. The latter improved both fibre thickness (Co 0.20±0.002 au, CVF 0.13±0.003 au, Emab 0.16±0.006 au; p<0.0001) and clot lysis time (Co 100%, CVF 192±12%, Emab 140±11%; p<0.001). The combined inhibition of C3 and C5 activation using both, Cp40 and eculizumab in combination optimized clot structure (Co 0.22±0.001 au, CVF 0.13±0.0006 au, Cp40/Emab 0.21±0.001 au; Co vs. Cp40/Emab p=0.003) and restored clot lysis time (Co 100%, CVF 226±6%, CP40/Emab 104±1%; Co vs. Cp40/Emap p=0.8). The results were confirmed by electron microscopy (fibre thickness: Co 93±1.4 nm, CVF 68±1.3 nm, Cp40 83±1.4 nm, Emab 78±1.7 nm, CP40/Emap 95±1.6 nm).
Conclusions
Complement activation at the level of complement C3 and C5 has a detrimental impact on clot properties. Blocking C3 and C5 activation can restore both clot density and prolongation of clot lysis time. Further studies are needed to determine the underlying binding sites on fibrin(ogen) to pave the way for molecules improving clot properties without affecting immune responses.
Acknowledgement/Funding
KS is supported by the German Research Foundation (DFG) (SFB/TRR219 C-07; HE 5666/1-2 to KS (née Hess)]
Collapse
Affiliation(s)
- K A Schutt
- RWTH University Hospital Aachen, Internal Medicine I, Aachen, Germany
| | - S Maxeiner
- RWTH University Hospital Aachen, Internal Medicine I, Aachen, Germany
| | - K Lysaja
- RWTH University Hospital Aachen, Internal Medicine I, Aachen, Germany
| | - M Berger
- RWTH University Hospital Aachen, Internal Medicine I, Aachen, Germany
| | - S Ruetten
- RWTH University Hospital Aachen, Electron Microscopy Facility, Aachen, Germany
| | - P Boor
- RWTH University Hospital Aachen, Electron Microscopy Facility, Aachen, Germany
| | - N Marx
- RWTH University Hospital Aachen, Internal Medicine I, Aachen, Germany
| |
Collapse
|
16
|
Berger M, Maxeiner S, Lysaja KM, Baldia P, Wessel L, Marx N, Schuett KM. 3310Platelet complement C3 deposition predicts platelet hyperactivity in patients with type II diabetes. Eur Heart J 2019. [DOI: 10.1093/eurheartj/ehz745.0074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Introduction
Atherothrombotic disease is associated with significant morbidity and mortality. Diabetes greatly increases the prothrombotic risk of individuals by factors that remain ill defined. Recently, increased plasma levels of complement C3 were associated with prothrombotic alterations in coagulation in patients with diabetes. The aim of this project was to evaluate the role of complement C3 on platelets in patients with type 2 diabetes.
Methods
Patients with type 2 diabetes (N=20) and controls (N=22) were included in the present study and assessed for platelet complement C3 deposition and expression of complement regulating proteins (e.g. CD35, CD55, CD59 and Factor H).
Results
Complement C3 was present on the surface of unstimulated platelets and significantly increased upon platelet activation (C3: 194±10 vs. C3-activated: 778±51 p=0.0001). Expression of complement C3 correlated significantly with platelet expression of CD35 and CD55, that are known to impair C3 breakdown, suggesting a key function in regulation of platelet complement deposition of these proteins (CD35 R2=0.374, p=0.001; CD55 R2 = 0.121 p=0.026). Interestingly, in patients with type 2 diabetes complement C3 deposition predicted platelet hyperactivity measured by P-selectin expression in an univariate analysis while this was not the case in control patients (Diabetes: std. β: 0.527; p=0.013 Controls: std.β 0.087 p=0.740). Using a multivariate approach complement C3 deposition remained a predictor for platelet hyperactivity after correction for dual antiplatelet therapy (DAPT), Aspirin treatment, BMI, age and basal platelet activity in patients with type II diabetes (Diabetes: std. β 0.490 p=0.049 Control: std. β −0.152 p=0.612). Since there was no quantitative difference in complement C3 deposition between the patient groups we hypothesised that a difference in complement activation might explain the differential effects of C3 deposition in these patient groups (Control: 186±54 vs. Diabetes: 202±76 p=0.422). Indeed, presence of the complement C3 metabolite iC3b, which is liberated by complement C3 activation, correlated significantly with HbA1c (R20.174; p=0.015) suggesting an increased complement activation in patients with diabetes. To test whether complement C3 activity influences platelet activity, we preincubated platelets with the complement activator cobra venom factor (CVF) or complement inhibitor CP40 (C3 inhibitor) and Eculizumab (C5 Inhibitor). While additive complement activation showed no effect on platelet activity (p=0.87), complement inhibition by either CP40 and Eculizumab led to a significant reduction in platelet activity (CP40% Inhibition: 15.81% ± 2.42 p=0.0006 Eculizumab % Inhibition: 31,71% ± 7.89, p=0.007).
Conclusion
Our data suggests that complement C3 deposition in patients with type 2 diabetes predicts platelet hyperactivity and these effects might be due to increased complement activation.
Collapse
Affiliation(s)
- M Berger
- RWTH University Hospital Aachen, Aachen, Germany
| | - S Maxeiner
- RWTH University Hospital Aachen, Aachen, Germany
| | - K M Lysaja
- RWTH University Hospital Aachen, Aachen, Germany
| | - P Baldia
- RWTH University Hospital Aachen, Aachen, Germany
| | - L Wessel
- RWTH University Hospital Aachen, Aachen, Germany
| | - N Marx
- RWTH University Hospital Aachen, Aachen, Germany
| | - K M Schuett
- RWTH University Hospital Aachen, Aachen, Germany
| |
Collapse
|
17
|
Trotter JH, Hao J, Maxeiner S, Tsetsenis T, Liu Z, Zhuang X, Südhof TC. Synaptic neurexin-1 assembles into dynamically regulated active zone nanoclusters. J Cell Biol 2019; 218:2677-2698. [PMID: 31262725 PMCID: PMC6683742 DOI: 10.1083/jcb.201812076] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [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] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 05/10/2019] [Accepted: 05/30/2019] [Indexed: 12/04/2022] Open
Abstract
Neurexins are well-characterized presynaptic cell adhesion molecules that engage multifarious postsynaptic ligands and organize diverse synapse properties. However, the precise synaptic localization of neurexins remains enigmatic. Using super-resolution microscopy, we demonstrate that neurexin-1 forms discrete nanoclusters at excitatory synapses, revealing a novel organizational feature of synaptic architecture. Synapses generally contain a single nanocluster that comprises more than four neurexin-1 molecules and that also includes neurexin-2 and/or neurexin-3 isoforms. Moreover, we find that neurexin-1 is physiologically cleaved by ADAM10 similar to its ligand neuroligin-1, with ∼4-6% of neurexin-1 and ∼2-3% of neuroligin-1 present in the adult brain as soluble ectodomain proteins. Blocking ADAM10-mediated neurexin-1 cleavage dramatically increased the synaptic neurexin-1 content, thereby elevating the percentage of Homer1(+) excitatory synapses containing neurexin-1 nanoclusters from 40-50% to ∼80%, and doubling the number of neurexin-1 molecules per nanocluster. Taken together, our results reveal an unexpected nanodomain organization of synapses in which neurexin-1 is assembled into discrete presynaptic nanoclusters that are dynamically regulated via ectodomain cleavage.
Collapse
Affiliation(s)
- Justin H Trotter
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA
- Howard Hughes Medical Institute, Stanford University, Stanford, CA
| | - Junjie Hao
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA
- Department of Physics, Harvard University, Cambridge, MA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA
| | - Stephan Maxeiner
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA
- Howard Hughes Medical Institute, Stanford University, Stanford, CA
| | - Theodoros Tsetsenis
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA
- Howard Hughes Medical Institute, Stanford University, Stanford, CA
| | - Zhihui Liu
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA
- Howard Hughes Medical Institute, Stanford University, Stanford, CA
| | - Xiaowei Zhuang
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA
- Department of Physics, Harvard University, Cambridge, MA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA
- Howard Hughes Medical Institute, Stanford University, Stanford, CA
| |
Collapse
|
18
|
Zaffalon S, Latz A, Krasteva-Christ G, Maxeiner S. Sex identification in horses (Equus caballus) based on the gene pair NLGN4X/NLGN4Y. Anim Genet 2019; 50:551. [PMID: 31318073 DOI: 10.1111/age.12823] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/23/2019] [Indexed: 11/30/2022]
Affiliation(s)
- Simon Zaffalon
- Anatomy and Cell Biology, Saarland University Medical School, Kirrbergerstr. 100 Bldg. 61, 66424, Homburg, Germany
| | - Ariane Latz
- Tierarztpraxis für Pferde Eyendorf, Zur Horst 13, 21376, Eyendorf, Germany
| | - Gabriela Krasteva-Christ
- Anatomy and Cell Biology, Saarland University Medical School, Kirrbergerstr. 100 Bldg. 61, 66424, Homburg, Germany
| | - Stephan Maxeiner
- Anatomy and Cell Biology, Saarland University Medical School, Kirrbergerstr. 100 Bldg. 61, 66424, Homburg, Germany
| |
Collapse
|
19
|
Wichmann L, Dulai JS, Marles-Wright J, Maxeiner S, Szczesniak PP, Manzini I, Althaus M. An extracellular acidic cleft confers profound H +-sensitivity to epithelial sodium channels containing the δ-subunit in Xenopus laevis. J Biol Chem 2019; 294:12507-12520. [PMID: 31248986 DOI: 10.1074/jbc.ra119.008255] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Revised: 06/27/2019] [Indexed: 11/06/2022] Open
Abstract
The limited sodium availability of freshwater and terrestrial environments was a major physiological challenge during vertebrate evolution. The epithelial sodium channel (ENaC) is present in the apical membrane of sodium-absorbing vertebrate epithelia and evolved as part of a machinery for efficient sodium conservation. ENaC belongs to the degenerin/ENaC protein family and is the only member that opens without an external stimulus. We hypothesized that ENaC evolved from a proton-activated sodium channel present in ionocytes of freshwater vertebrates and therefore investigated whether such ancestral traits are present in ENaC isoforms of the aquatic pipid frog Xenopus laevis Using whole-cell and single-channel electrophysiology of Xenopus oocytes expressing ENaC isoforms assembled from αβγ- or δβγ-subunit combinations, we demonstrate that Xenopus δβγ-ENaC is profoundly activated by extracellular acidification within biologically relevant ranges (pH 8.0-6.0). This effect was not observed in Xenopus αβγ-ENaC or human ENaC orthologs. We show that protons interfere with allosteric ENaC inhibition by extracellular sodium ions, thereby increasing the probability of channel opening. Using homology modeling of ENaC structure and site-directed mutagenesis, we identified a cleft region within the extracellular loop of the δ-subunit that contains several acidic amino acid residues that confer proton-sensitivity and enable allosteric inhibition by extracellular sodium ions. We propose that Xenopus δβγ-ENaC can serve as a model for investigating ENaC transformation from a proton-activated toward a constitutively-active ion channel. Such transformation might have occurred during the evolution of tetrapod vertebrates to enable bulk sodium absorption during the water-to-land transition.
Collapse
Affiliation(s)
- Lukas Wichmann
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom; Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus-Liebig University Giessen, 35390 Giessen, Germany
| | - Jasdip Singh Dulai
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom
| | - Jon Marles-Wright
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom
| | - Stephan Maxeiner
- Institute of Anatomy and Cell Biology, Saarland University, 66421 Homburg, Germany
| | - Pawel Piotr Szczesniak
- Department of Medicine, Haematology/Oncology, Johann-Wolfgang-Goethe University Frankfurt, 60323 Frankfurt, Germany
| | - Ivan Manzini
- Institute of Animal Physiology, Department of Animal Physiology and Molecular Biomedicine, Justus-Liebig University Giessen, 35390 Giessen, Germany
| | - Mike Althaus
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom.
| |
Collapse
|
20
|
Althaus M, Gettings SM, Wichmann L, Krasteva‐Christ G, Maxeiner S. Sodium self‐inhibition and proton sensitivity do not correlate with proteolytic processing in epithelial sodium channels containing the δ‐subunit. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.824.27] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Mike Althaus
- School of Natural and Environmental SciencesNewcastle UniversityNewcastle upon TyneUnited Kingdom
| | - Sean Michael Gettings
- School of Natural and Environmental SciencesNewcastle UniversityNewcastle upon TyneUnited Kingdom
| | - Lukas Wichmann
- Institute for Animal PhysiologyJustus‐Liebig‐UniversityGiessenGermany
| | | | - Stephan Maxeiner
- Institute for Anatomy and Cell BiologySaarland UniversityHomburgGermany
| |
Collapse
|
21
|
Scherer JJ, Reichrath S, Tschernig T, Maxeiner S. A snapshot of anatomy teaching: Peer-led anatomy boot camps — Priming for success? Ann Anat 2019; 221:141-147. [DOI: 10.1016/j.aanat.2018.10.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 10/01/2018] [Accepted: 10/02/2018] [Indexed: 10/28/2022]
|
22
|
Hamza A, Radosa J, Meyberg-Solomayer G, Solomayer EF, Takacs Z, Juhasz-Boess I, Krasteva-Christ G, Tschernig T, Maxeiner S. Trial integration of combined ultrasound and laparoscopy tuition in an undergraduate anatomy class with volunteer participation - A pilot study. Ann Anat 2018; 221:101-107. [PMID: 30300688 DOI: 10.1016/j.aanat.2018.09.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 09/11/2018] [Accepted: 09/18/2018] [Indexed: 10/28/2022]
Abstract
Anatomy is a cornerstone of medical undergraduate curricula. Due to increasing changes in various medical fields, a lot of new subjects were introduced in undergraduate curricula, while the teaching areas of basic sciences, i.e. anatomy, were reduced. The introduction of advanced diagnostic and therapeutic devices, i.e. ultrasound and laparoscopy, with outstanding imaging quality will be increasingly introduced in basic sciences. In our project, we examined the effect integrating ultrasound and laparoscopy in an anatomy undergraduate course to illustrate the female pelvis. Anatomy students that completed their practicum and cadaver dissection course were enrolled in our project. They received a theoretical introduction followed by a practical course of ultrasound or laparoscopy in the department of obstetrics and gynaecology. Following the course the students had to answer two questionnaires that evaluated their satisfaction, subjective knowledge-gain, problems and content of the course. At the end, a closing briefing was done to discuss the clinical skills and the course. The answers of the questionnaire were summed up in a Likert scale. 25 students were enrolled in the project. 52% attended laparoscopy operations, while 48% attended ultrasound examinations. After analysing the questionnaires using Likert scales (1=strongly agree, 5=strongly disagree) a general satisfaction of 1.5, a subjective knowledge gain of 2.4 and a thrive to extend these clinical skill programs in gynaecology and other specialities in basic science of 1.5 and 1.2, respectively, was reported. There were no statistically significant differences in the Likert scores between both groups (p>0.05). The introduction of ultrasound and laparoscopy in undergraduate basic science teaching programs is a promising method and should be further evaluated, standardized and expanded.
Collapse
Affiliation(s)
- Amr Hamza
- Department of Obstetrics and Gynaecology, University Medical Centre, 66421 Homburg, Germany
| | - Julia Radosa
- Department of Obstetrics and Gynaecology, University Medical Centre, 66421 Homburg, Germany
| | | | - Erich-Franz Solomayer
- Department of Obstetrics and Gynaecology, University Medical Centre, 66421 Homburg, Germany
| | - Zoltan Takacs
- Department of Obstetrics and Gynaecology, University Medical Centre, 66421 Homburg, Germany
| | - Ingolf Juhasz-Boess
- Department of Obstetrics and Gynaecology, University Medical Centre, 66421 Homburg, Germany
| | - Gabriela Krasteva-Christ
- Institute of Anatomy, Cell and Developmental Biology of the University of Saarland, 66421 Homburg, Germany
| | - Thomas Tschernig
- Institute of Anatomy, Cell and Developmental Biology of the University of Saarland, 66421 Homburg, Germany.
| | - Stephan Maxeiner
- Institute of Anatomy, Cell and Developmental Biology of the University of Saarland, 66421 Homburg, Germany
| |
Collapse
|
23
|
Moellmann J, Haj-Yehia E, Maxeiner S, Schuett K, Lopaschuk GD, Verma S, Mayoux E, Lehrke M, Marx N. P1266Empagliflozin improves left ventricular diastolic function in db/db mice without altering cardiac expression of enzymes relevant for ketone body or branched chain amino acid catabolism. Eur Heart J 2018. [DOI: 10.1093/eurheartj/ehy565.p1266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- J Moellmann
- RWTH University Hospital Aachen, Cardiology, Aachen, Germany
| | - E Haj-Yehia
- RWTH University Hospital Aachen, Cardiology, Aachen, Germany
| | - S Maxeiner
- RWTH University Hospital Aachen, Cardiology, Aachen, Germany
| | - K Schuett
- RWTH University Hospital Aachen, Cardiology, Aachen, Germany
| | - G D Lopaschuk
- University of Alberta, Faculty of Pharmacy and Pharmaceutical Sciences, Edmonton, Canada
| | - S Verma
- University of Toronto, Department of Surgery and Pharmacology & Toxicology, Toronto, Canada
| | - E Mayoux
- Boehringer Ingelheim Pharma GmbH & Co. KG, Cardio-metabolic Diseases, Ingelheim, Germany
| | - M Lehrke
- RWTH University Hospital Aachen, Cardiology, Aachen, Germany
| | - N Marx
- RWTH University Hospital Aachen, Cardiology, Aachen, Germany
| |
Collapse
|
24
|
Keshavarz M, Skill M, Hollenhorst MI, Maxeiner S, Walecki M, Pfeil U, Kummer W, Krasteva-Christ G. Caveolin-3 differentially orchestrates cholinergic and serotonergic constriction of murine airways. Sci Rep 2018; 8:7508. [PMID: 29760450 PMCID: PMC5951923 DOI: 10.1038/s41598-018-25445-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 04/16/2018] [Indexed: 01/22/2023] Open
Abstract
The mechanisms of controlling airway smooth muscle (ASM) tone are of utmost clinical importance as inappropriate constriction is a hallmark in asthma and chronic obstructive pulmonary disease. Receptors for acetylcholine and serotonin, two relevant mediators in this context, appear to be incorporated in specialized, cholesterol-rich domains of the plasma membrane, termed caveolae due to their invaginated shape. The structural protein caveolin-1 partly accounts for anchoring of these receptors. We here determined the role of the other major caveolar protein, caveolin-3 (cav-3), in orchestrating cholinergic and serotonergic ASM responses, utilizing newly generated cav-3 deficient mice. Cav-3 deficiency fully abrogated serotonin-induced constriction of extrapulmonary airways in organ baths while leaving intrapulmonary airways unaffected, as assessed in precision cut lung slices. The selective expression of cav-3 in tracheal, but not intrapulmonary bronchial epithelial cells, revealed by immunohistochemistry, might explain the differential effects of cav-3 deficiency on serotonergic ASM constriction. The cholinergic response of extrapulmonary airways was not altered, whereas a considerable increase was observed in cav-3-/- intrapulmonary bronchi. Thus, cav-3 differentially organizes serotonergic and cholinergic signaling in ASM through mechanisms that are specific for airways of certain caliber and anatomical position. This may allow for selective and site-specific intervention in hyperreactive states.
Collapse
Affiliation(s)
- M Keshavarz
- Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - M Skill
- Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - M I Hollenhorst
- Institute of Anatomy and Cell Biology, School of Medicine, Saarland University, Saarbrucken, Germany
| | - S Maxeiner
- Institute of Anatomy and Cell Biology, School of Medicine, Saarland University, Saarbrucken, Germany
| | - M Walecki
- Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - U Pfeil
- Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - W Kummer
- Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany.,German Center for Lung Research (DZL), Marburg, Germany
| | - G Krasteva-Christ
- Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany. .,German Center for Lung Research (DZL), Marburg, Germany. .,Institute of Anatomy and Cell Biology, School of Medicine, Saarland University, Saarbrucken, Germany.
| |
Collapse
|
25
|
Berndt-Zipfel C, Maxeiner S. Weniger Hypoglykämien durch CGM-Dexcom in der Diabetologischen-Schwerpunktpraxis (Rheinland-Pfalz). DIABETOL STOFFWECHS 2018. [DOI: 10.1055/s-0038-1641850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- C Berndt-Zipfel
- Diabetologisch Hausärztliche Gemeinschafspraxis Bosenheim, Bad Kreuznach, Germany
| | - S Maxeiner
- Diabetologisch Hausärztliche Gemeinschafspraxis Bosenheim, Bad Kreuznach, Germany
| |
Collapse
|
26
|
Berndt-Zipfel C, Maxeiner S. Fallbericht nach 12 Jahren Diabetes zufällige Entdeckung eines Phäochromozytoms. DIABETOL STOFFWECHS 2018. [DOI: 10.1055/s-0038-1641864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- C Berndt-Zipfel
- Diabetologisch Hausärztliche Gemeinschaftspraxis Bosenheim, Bad Kreuznach, Germany
| | - S Maxeiner
- Diabetologisch Hausärztliche Gemeinschaftspraxis Bosenheim, Bad Kreuznach, Germany
| |
Collapse
|
27
|
Jean P, Lopez de la Morena D, Michanski S, Jaime Tobón LM, Chakrabarti R, Picher MM, Neef J, Jung S, Gültas M, Maxeiner S, Neef A, Wichmann C, Strenzke N, Grabner C, Moser T. The synaptic ribbon is critical for sound encoding at high rates and with temporal precision. eLife 2018; 7:29275. [PMID: 29328020 PMCID: PMC5794258 DOI: 10.7554/elife.29275] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 12/19/2017] [Indexed: 11/30/2022] Open
Abstract
We studied the role of the synaptic ribbon for sound encoding at the synapses between inner hair cells (IHCs) and spiral ganglion neurons (SGNs) in mice lacking RIBEYE (RBEKO/KO). Electron and immunofluorescence microscopy revealed a lack of synaptic ribbons and an assembly of several small active zones (AZs) at each synaptic contact. Spontaneous and sound-evoked firing rates of SGNs and their compound action potential were reduced, indicating impaired transmission at ribbonless IHC-SGN synapses. The temporal precision of sound encoding was impaired and the recovery of SGN-firing from adaptation indicated slowed synaptic vesicle (SV) replenishment. Activation of Ca2+-channels was shifted to more depolarized potentials and exocytosis was reduced for weak depolarizations. Presynaptic Ca2+-signals showed a broader spread, compatible with the altered Ca2+-channel clustering observed by super-resolution immunofluorescence microscopy. We postulate that RIBEYE disruption is partially compensated by multi-AZ organization. The remaining synaptic deficit indicates ribbon function in SV-replenishment and Ca2+-channel regulation. Our sense of hearing relies on our ears quickly and tirelessly processing information in a precise manner. Sounds cause vibrations in a part of the inner ear called the cochlea. Inside the cochlea, the vibrations move hair-like structures on sensory cells that translate these movements into electrical signals. These hair cells are connected to specialized nerve cells that relay the signals to the brain, which then interprets them as sounds. Hair cells communicate with the specialized nerve cells via connections known as chemical synapses. This means that the electrical signals in the hair cell activate channel proteins that allow calcium ions to flow in. This in turn triggers membrane-bound packages called vesicles inside the hair cell to fuse with its surface membrane and release their contents to the outside. The contents, namely chemicals called neurotransmitters, then travels across the space between the cells, relaying the signal to the nerve cell. The junctions between the hair cells and the nerve cells are more specifically known as ribbon synapses. This is because they have a ribbon-like structure that appears to tether a halo of vesicles close to the active zone where neurotransmitters are released. However, the exact role of this synaptic ribbon has remained mysterious despite decades of study. The ribbon is mainly composed of a protein called Ribeye, and now Jean, Lopez de la Morena, Michanski, Jaime Tobón et al. show that mutant mice that lack this protein do not have any ribbons at their “ribbon synapses”. Hair cells without synaptic ribbons are less able to timely and reliably send signals to the nerve cells, most likely because they cannot replenish the vesicles at the synapse quickly enough. Further analysis showed that the synaptic ribbon also helps to regulate the calcium channels at the synapse, which is important for linking the electrical signals in the hair cell to the release of the neurotransmitters. Jean et al. also saw that hair cells without ribbons reorganize their synapses to form multiple active zones that could transfer neurotransmitter to the nerve cells. This could partially compensate for the loss of the ribbons, meaning the impact of their loss may have been underestimated. Future studies could explore this by eliminating the Ribeye protein only after the ribbon synapses are fully formed. These findings may help scientists to better understand deafness and other hearing disorders in humans. They will also be of interest to neuroscientists who research synapses, hearing and other sensory processes.
Collapse
Affiliation(s)
- Philippe Jean
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center, University of Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany
| | - David Lopez de la Morena
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany
| | - Susann Michanski
- Collaborative Research Center, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany.,Institute for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Lina María Jaime Tobón
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center, University of Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Rituparna Chakrabarti
- Collaborative Research Center, University of Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany.,Institute for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Maria Magdalena Picher
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany
| | - Jakob Neef
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - SangYong Jung
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Neuro Modulation and Neuro Circuitry Group, Singapore Bioimaging Consortium (SBIC), Biomedical Sciences Institutes, Singapore, Singapore
| | - Mehmet Gültas
- Department of Breeding Informatics, Georg-August-University Göttingen, Göttingen, Germany
| | - Stephan Maxeiner
- Institute for Anatomy and Cell Biology, University of the Saarland, Homburg, Germany
| | - Andreas Neef
- Bernstein Group Biophysics of Neural Computation, Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany
| | - Carolin Wichmann
- Collaborative Research Center, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany.,Institute for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Nicola Strenzke
- Collaborative Research Center, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Auditory Systems Physiology Group, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany
| | - Chad Grabner
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany
| |
Collapse
|
28
|
Becker L, Schnee ME, Niwa M, Sun W, Maxeiner S, Talaei S, Kachar B, Rutherford MA, Ricci AJ. The presynaptic ribbon maintains vesicle populations at the hair cell afferent fiber synapse. eLife 2018; 7:30241. [PMID: 29328021 PMCID: PMC5794257 DOI: 10.7554/elife.30241] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 12/19/2017] [Indexed: 01/07/2023] Open
Abstract
The ribbon is the structural hallmark of cochlear inner hair cell (IHC) afferent synapses, yet its role in information transfer to spiral ganglion neurons (SGNs) remains unclear. We investigated the ribbon’s contribution to IHC synapse formation and function using KO mice lacking RIBEYE. Despite loss of the entire ribbon structure, synapses retained their spatiotemporal development and KO mice had a mild hearing deficit. IHCs of KO had fewer synaptic vesicles and reduced exocytosis in response to brief depolarization; a high stimulus level rescued exocytosis in KO. SGNs exhibited a lack of sustained excitatory postsynaptic currents (EPSCs). We observed larger postsynaptic glutamate receptor plaques, potentially compensating for the reduced EPSC rate in KO. Surprisingly, large-amplitude EPSCs were maintained in KO, while a small population of low-amplitude slower EPSCs was increased in number. The ribbon facilitates signal transduction at physiological stimulus levels by retaining a larger residency pool of synaptic vesicles.
Collapse
Affiliation(s)
- Lars Becker
- Department of Otolaryngology, Stanford University, Stanford, United States
| | - Michael E Schnee
- Department of Otolaryngology, Stanford University, Stanford, United States
| | - Mamiko Niwa
- Department of Otolaryngology, Stanford University, Stanford, United States
| | - Willy Sun
- National Institute of Deafness and Communicative Disorders, United States
| | - Stephan Maxeiner
- Molecular and Cellular Physiology, Stanford University, Stanford, United States
| | - Sara Talaei
- Department of Otolaryngology, Stanford University, Stanford, United States
| | - Bechara Kachar
- National Institute of Deafness and Communicative Disorders, United States
| | - Mark A Rutherford
- Department of Otolaryngology, Washington University, St. Louis, United States
| | - Anthony J Ricci
- Department of Otolaryngology, Stanford University, Stanford, United States.,Molecular and Cellular Physiology, Stanford University, Stanford, United States
| |
Collapse
|
29
|
Anderson GR, Maxeiner S, Sando R, Tsetsenis T, Malenka RC, Südhof TC. Postsynaptic adhesion GPCR latrophilin-2 mediates target recognition in entorhinal-hippocampal synapse assembly. J Cell Biol 2017; 216:3831-3846. [PMID: 28972101 PMCID: PMC5674891 DOI: 10.1083/jcb.201703042] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [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] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 07/24/2017] [Accepted: 08/17/2017] [Indexed: 12/15/2022] Open
Abstract
Synapse assembly likely requires postsynaptic target recognition by incoming presynaptic afferents. Using newly generated conditional knock-in and knockout mice, we show in this study that latrophilin-2 (Lphn2), a cell-adhesion G protein-coupled receptor and presumptive α-latrotoxin receptor, controls the numbers of a specific subset of synapses in CA1-region hippocampal neurons, suggesting that Lphn2 acts as a synaptic target-recognition molecule. In cultured hippocampal neurons, Lphn2 maintained synapse numbers via a postsynaptic instead of a presynaptic mechanism, which was surprising given its presumptive role as an α-latrotoxin receptor. In CA1-region neurons in vivo, Lphn2 was specifically targeted to dendritic spines in the stratum lacunosum-moleculare, which form synapses with presynaptic entorhinal cortex afferents. In this study, postsynaptic deletion of Lphn2 selectively decreased spine numbers and impaired synaptic inputs from entorhinal but not Schaffer-collateral afferents. Behaviorally, loss of Lphn2 from the CA1 region increased spatial memory retention but decreased learning of sequential spatial memory tasks. Thus, Lphn2 appears to control synapse numbers in the entorhinal cortex/CA1 region circuit by acting as a domain-specific postsynaptic target-recognition molecule.
Collapse
MESH Headings
- Animals
- Behavior, Animal
- CA1 Region, Hippocampal/metabolism
- CA1 Region, Hippocampal/pathology
- CA1 Region, Hippocampal/physiopathology
- Cells, Cultured
- Dendritic Spines/metabolism
- Dendritic Spines/pathology
- Entorhinal Cortex/metabolism
- Entorhinal Cortex/pathology
- Entorhinal Cortex/physiopathology
- Fear
- Genotype
- Maze Learning
- Memory
- Mice, Mutant Strains
- Motor Activity
- Neurons/metabolism
- Neurons/pathology
- Phenotype
- Presynaptic Terminals/metabolism
- Presynaptic Terminals/pathology
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Peptide/genetics
- Receptors, Peptide/metabolism
- Rotarod Performance Test
- Smell
- Synaptic Membranes/metabolism
- Synaptic Membranes/pathology
- Synaptic Potentials
- Time Factors
- Transfection
Collapse
Affiliation(s)
- Garret R Anderson
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA
- Department of Psychiatry and Behavioral Science, Nancy Pritzker Laboratory, Stanford University Medical School, Stanford, CA
| | - Stephan Maxeiner
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA
| | - Richard Sando
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA
| | - Theodoros Tsetsenis
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA
| | - Robert C Malenka
- Department of Psychiatry and Behavioral Science, Nancy Pritzker Laboratory, Stanford University Medical School, Stanford, CA
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA
| |
Collapse
|
30
|
Hamza A, Meyberg-Solomayer G, Solomayer EF, Takacs Z, Juhasz-Boess I, Radosa J, Ströder R, Tschernig T, Maxeiner S. Einführung eines praktischen Ultraschall- und Laparoskopiekurs in der Anatomielehre am UKS. Geburtshilfe Frauenheilkd 2017. [DOI: 10.1055/s-0037-1606158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Affiliation(s)
- A Hamza
- Klinik für Frauenheilkunde, Geburtshilfe und Reproduktionsmedizin, Universitätsklinikum des Saarlandes
| | - G Meyberg-Solomayer
- Klinik für Frauenheilkunde, Geburtshilfe und Reproduktionsmedizin, Universitätsklinikum des Saarlandes
| | - EF Solomayer
- Klinik für Frauenheilkunde, Geburtshilfe und Reproduktionsmedizin, Universitätsklinikum des Saarlandes
| | - Z Takacs
- Klinik für Frauenheilkunde, Geburtshilfe und Reproduktionsmedizin, Universitätsklinikum des Saarlandes
| | - I Juhasz-Boess
- Klinik für Frauenheilkunde, Geburtshilfe und Reproduktionsmedizin, Universitätsklinikum des Saarlandes
| | - J Radosa
- Klinik für Frauenheilkunde, Geburtshilfe und Reproduktionsmedizin, Universitätsklinikum des Saarlandes
| | - R Ströder
- Klinik für Frauenheilkunde, Geburtshilfe und Reproduktionsmedizin, Universitätsklinikum des Saarlandes
| | - T Tschernig
- Institut für Anatomie, Zellbiologie und Entwicklungsbiologie, Universität des Saarlandes
| | - S Maxeiner
- Institut für Anatomie, Zellbiologie und Entwicklungsbiologie, Universität des Saarlandes
| |
Collapse
|
31
|
Maxeiner S, Luo F, Tan A, Schmitz F, Südhof TC. How to make a synaptic ribbon: RIBEYE deletion abolishes ribbons in retinal synapses and disrupts neurotransmitter release. EMBO J 2016; 35:1098-114. [PMID: 26929012 DOI: 10.15252/embj.201592701] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Accepted: 02/01/2016] [Indexed: 12/21/2022] Open
Abstract
Synaptic ribbons are large proteinaceous scaffolds at the active zone of ribbon synapses that are specialized for rapid sustained synaptic vesicles exocytosis. A single ribbon-specific protein is known, RIBEYE, suggesting that ribbons may be constructed from RIBEYE protein. RIBEYE knockdown in zebrafish, however, only reduced but did not eliminate ribbons, indicating a more ancillary role. Here, we show in mice that full deletion of RIBEYE abolishes all presynaptic ribbons in retina synapses. Using paired recordings in acute retina slices, we demonstrate that deletion of RIBEYE severely impaired fast and sustained neurotransmitter release at bipolar neuron/AII amacrine cell synapses and rendered spontaneous miniature release sensitive to the slow Ca(2+)-buffer EGTA, suggesting that synaptic ribbons mediate nano-domain coupling of Ca(2+) channels to synaptic vesicle exocytosis. Our results show that RIBEYE is essential for synaptic ribbons as such, and may organize presynaptic nano-domains that position release-ready synaptic vesicles adjacent to Ca(2+) channels.
Collapse
Affiliation(s)
- Stephan Maxeiner
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute Stanford University School of Medicine, Stanford, CA, USA Department of Neuroanatomy, Institute for Anatomy and Cell Biology Medical School Saarland University, Homburg/Saar, Germany
| | - Fujun Luo
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute Stanford University School of Medicine, Stanford, CA, USA
| | - Alison Tan
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute Stanford University School of Medicine, Stanford, CA, USA
| | - Frank Schmitz
- Department of Neuroanatomy, Institute for Anatomy and Cell Biology Medical School Saarland University, Homburg/Saar, Germany
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute Stanford University School of Medicine, Stanford, CA, USA
| |
Collapse
|
32
|
Zhang B, Chen LY, Liu X, Maxeiner S, Lee SJ, Gokce O, Südhof TC. Neuroligins Sculpt Cerebellar Purkinje-Cell Circuits by Differential Control of Distinct Classes of Synapses. Neuron 2015; 87:781-96. [PMID: 26291161 DOI: 10.1016/j.neuron.2015.07.020] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 05/25/2015] [Accepted: 07/22/2015] [Indexed: 10/23/2022]
Abstract
Neuroligins are postsynaptic cell-adhesion molecules that bind presynaptic neurexins and are genetically linked to autism. Neuroligins are proposed to organize synaptogenesis and/or synaptic transmission, but no systematic analysis of neuroligins in a defined circuit is available. Here, we show that conditional deletion of all neuroligins in cerebellar Purkinje cells caused loss of distal climbing-fiber synapses and weakened climbing-fiber but not parallel-fiber synapses, consistent with alternative use of neuroligins and cerebellins as neurexin ligands for the excitatory climbing-fiber versus parallel-fiber synapses. Moreover, deletion of neuroligins increased the size of inhibitory basket/stellate-cell synapses but simultaneously severely impaired their function. Multiple neuroligin isoforms differentially contributed to climbing-fiber and basket/stellate-cell synapse functions, such that inhibitory synapse-specific neuroligin-2 was unexpectedly essential for maintaining normal climbing-fiber synapse numbers. Using systematic analyses of all neuroligins in a defined neural circuit, our data thus show that neuroligins differentially contribute to various Purkinje-cell synapses in the cerebellum in vivo.
Collapse
Affiliation(s)
- Bo Zhang
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, 265 Campus Drive, Room G1021, Stanford, CA 94305, USA
| | - Lulu Y Chen
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, 265 Campus Drive, Room G1021, Stanford, CA 94305, USA
| | - Xinran Liu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Stephan Maxeiner
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, 265 Campus Drive, Room G1021, Stanford, CA 94305, USA
| | - Sung-Jin Lee
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, 265 Campus Drive, Room G1021, Stanford, CA 94305, USA
| | - Ozgun Gokce
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, 265 Campus Drive, Room G1021, Stanford, CA 94305, USA
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, 265 Campus Drive, Room G1021, Stanford, CA 94305, USA.
| |
Collapse
|
33
|
Patzke C, Han Y, Covy J, Yi F, Maxeiner S, Wernig M, Südhof TC. Analysis of conditional heterozygous STXBP1 mutations in human neurons. J Clin Invest 2015; 125:3560-71. [PMID: 26280581 PMCID: PMC4588304 DOI: 10.1172/jci78612] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [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: 08/19/2014] [Accepted: 06/11/2015] [Indexed: 12/31/2022] Open
Abstract
Heterozygous mutations in the syntaxin-binding protein 1 (STXBP1) gene, which encodes Munc18-1, a core component of the presynaptic membrane-fusion machinery, cause infantile early epileptic encephalopathy (Ohtahara syndrome), but it is unclear how a partial loss of Munc18-1 produces this severe clinical presentation. Here, we generated human ES cells designed to conditionally express heterozygous and homozygous STXBP1 loss-of-function mutations and studied isogenic WT and STXBP1-mutant human neurons derived from these conditionally mutant ES cells. We demonstrated that heterozygous STXBP1 mutations lower the levels of Munc18-1 protein and its binding partner, the t-SNARE-protein Syntaxin-1, by approximately 30% and decrease spontaneous and evoked neurotransmitter release by nearly 50%. Thus, our results confirm that using engineered human embryonic stem (ES) cells is a viable approach to studying disease-associated mutations in human neurons on a controlled genetic background, demonstrate that partial STXBP1 loss of function robustly impairs neurotransmitter release in human neurons, and suggest that heterozygous STXBP1 mutations cause early epileptic encephalopathy specifically through a presynaptic impairment.
Collapse
Affiliation(s)
| | - Yan Han
- Department of Molecular and Cellular Physiology
| | - Jason Covy
- Department of Molecular and Cellular Physiology
| | - Fei Yi
- Department of Molecular and Cellular Physiology
| | | | - Marius Wernig
- Institute for Stem Cell Biology and Regenerative Medicine and Department of Pathology, and
| | - Thomas C. Südhof
- Department of Molecular and Cellular Physiology
- Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California, USA
| |
Collapse
|
34
|
Pak C, Danko T, Zhang Y, Aoto J, Anderson G, Maxeiner S, Yi F, Wernig M, Südhof TC. Human Neuropsychiatric Disease Modeling using Conditional Deletion Reveals Synaptic Transmission Defects Caused by Heterozygous Mutations in NRXN1. Cell Stem Cell 2015; 17:316-28. [PMID: 26279266 DOI: 10.1016/j.stem.2015.07.017] [Citation(s) in RCA: 156] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2014] [Revised: 03/23/2015] [Accepted: 07/22/2015] [Indexed: 10/23/2022]
Abstract
Heterozygous mutations of the NRXN1 gene, which encodes the presynaptic cell-adhesion molecule neurexin-1, were repeatedly associated with autism and schizophrenia. However, diverse clinical presentations of NRXN1 mutations in patients raise the question of whether heterozygous NRXN1 mutations alone directly impair synaptic function. To address this question under conditions that precisely control for genetic background, we generated human ESCs with different heterozygous conditional NRXN1 mutations and analyzed two different types of isogenic control and NRXN1 mutant neurons derived from these ESCs. Both heterozygous NRXN1 mutations selectively impaired neurotransmitter release in human neurons without changing neuronal differentiation or synapse formation. Moreover, both NRXN1 mutations increased the levels of CASK, a critical synaptic scaffolding protein that binds to neurexin-1. Our results show that, unexpectedly, heterozygous inactivation of NRXN1 directly impairs synaptic function in human neurons, and they illustrate the value of this conditional deletion approach for studying the functional effects of disease-associated mutations.
Collapse
Affiliation(s)
- ChangHui Pak
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
| | - Tamas Danko
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
| | - Yingsha Zhang
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
| | - Jason Aoto
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
| | - Garret Anderson
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
| | - Stephan Maxeiner
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
| | - Fei Yi
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
| | - Marius Wernig
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA; Department of Pathology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA.
| |
Collapse
|
35
|
Rothwell PE, Fuccillo MV, Maxeiner S, Hayton SJ, Gokce O, Lim BK, Fowler SC, Malenka RC, Südhof TC. Autism-associated neuroligin-3 mutations commonly impair striatal circuits to boost repetitive behaviors. Cell 2014; 158:198-212. [PMID: 24995986 DOI: 10.1016/j.cell.2014.04.045] [Citation(s) in RCA: 325] [Impact Index Per Article: 32.5] [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] [Received: 11/09/2013] [Revised: 02/22/2014] [Accepted: 04/18/2014] [Indexed: 11/17/2022]
Abstract
In humans, neuroligin-3 mutations are associated with autism, whereas in mice, the corresponding mutations produce robust synaptic and behavioral changes. However, different neuroligin-3 mutations cause largely distinct phenotypes in mice, and no causal relationship links a specific synaptic dysfunction to a behavioral change. Using rotarod motor learning as a proxy for acquired repetitive behaviors in mice, we found that different neuroligin-3 mutations uniformly enhanced formation of repetitive motor routines. Surprisingly, neuroligin-3 mutations caused this phenotype not via changes in the cerebellum or dorsal striatum but via a selective synaptic impairment in the nucleus accumbens/ventral striatum. Here, neuroligin-3 mutations increased rotarod learning by specifically impeding synaptic inhibition onto D1-dopamine receptor-expressing but not D2-dopamine receptor-expressing medium spiny neurons. Our data thus suggest that different autism-associated neuroligin-3 mutations cause a common increase in acquired repetitive behaviors by impairing a specific striatal synapse and thereby provide a plausible circuit substrate for autism pathophysiology.
Collapse
Affiliation(s)
- Patrick E Rothwell
- Department of Molecular and Cellular Physiology, Stanford University Medical School, Stanford, CA 94305, USA; Nancy Pritzker Laboratory, Department of Psychiatry and Behavioral Sciences, Stanford University Medical School, Stanford, CA 94305, USA
| | - Marc V Fuccillo
- Department of Molecular and Cellular Physiology, Stanford University Medical School, Stanford, CA 94305, USA; Nancy Pritzker Laboratory, Department of Psychiatry and Behavioral Sciences, Stanford University Medical School, Stanford, CA 94305, USA
| | - Stephan Maxeiner
- Department of Molecular and Cellular Physiology, Stanford University Medical School, Stanford, CA 94305, USA
| | - Scott J Hayton
- Nancy Pritzker Laboratory, Department of Psychiatry and Behavioral Sciences, Stanford University Medical School, Stanford, CA 94305, USA
| | - Ozgun Gokce
- Department of Molecular and Cellular Physiology, Stanford University Medical School, Stanford, CA 94305, USA
| | - Byung Kook Lim
- Nancy Pritzker Laboratory, Department of Psychiatry and Behavioral Sciences, Stanford University Medical School, Stanford, CA 94305, USA
| | - Stephen C Fowler
- Department of Pharmacology and Toxicology, University of Kansas, Lawrence, KS 66045, USA
| | - Robert C Malenka
- Nancy Pritzker Laboratory, Department of Psychiatry and Behavioral Sciences, Stanford University Medical School, Stanford, CA 94305, USA.
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University Medical School, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA 94305, USA.
| |
Collapse
|
36
|
Boucard AA, Maxeiner S, Südhof TC. Latrophilins function as heterophilic cell-adhesion molecules by binding to teneurins: regulation by alternative splicing. J Biol Chem 2013; 289:387-402. [PMID: 24273166 DOI: 10.1074/jbc.m113.504779] [Citation(s) in RCA: 131] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Latrophilin-1, -2, and -3 are adhesion-type G protein-coupled receptors that are auxiliary α-latrotoxin receptors, suggesting that they may have a synaptic function. Using pulldowns, we here identify teneurins, type II transmembrane proteins that are also candidate synaptic cell-adhesion molecules, as interactors for the lectin-like domain of latrophilins. We show that teneurin binds to latrophilins with nanomolar affinity and that this binding mediates cell adhesion, consistent with a role of teneurin binding to latrophilins in trans-synaptic interactions. All latrophilins are subject to alternative splicing at an N-terminal site; in latrophilin-1, this alternative splicing modulates teneurin binding but has no effect on binding of latrophilin-1 to another ligand, FLRT3. Addition to cultured neurons of soluble teneurin-binding fragments of latrophilin-1 decreased synapse density, suggesting that latrophilin binding to teneurin may directly or indirectly influence synapse formation and/or maintenance. These observations are potentially intriguing in view of the proposed role for Drosophila teneurins in determining synapse specificity. However, teneurins in Drosophila were suggested to act as homophilic cell-adhesion molecules, whereas our findings suggest a heterophilic interaction mechanism. Thus, we tested whether mammalian teneurins also are homophilic cell-adhesion molecules, in addition to binding to latrophilins as heterophilic cell-adhesion molecules. Strikingly, we find that although teneurins bind to each other in solution, homophilic teneurin-teneurin binding is unable to support stable cell adhesion, different from heterophilic teneurin-latrophilin binding. Thus, mammalian teneurins act as heterophilic cell-adhesion molecules that may be involved in trans-neuronal interaction processes such as synapse formation or maintenance.
Collapse
Affiliation(s)
- Antony A Boucard
- From the Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Palo Alto, California 94305
| | | | | |
Collapse
|
37
|
Chapman RJ, Lall VK, Maxeiner S, Willecke K, Deuchars J, King AE. Localization of neurones expressing the gap junction protein Connexin45 within the adult spinal dorsal horn: a study using Cx45-eGFP reporter mice. Brain Struct Funct 2012; 218:751-65. [PMID: 22638825 PMCID: PMC3637643 DOI: 10.1007/s00429-012-0426-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Accepted: 04/30/2012] [Indexed: 12/21/2022]
Abstract
Connexin (Cx) proteins localized to neuronal and glial syncytia provide the ultrastructural components for intercellular communication via gap junctions. In this study, a Cx45 reporter mouse model in which the Cx45 coding sequence is substituted for enhanced green fluorescent protein (eGFP) was used to characterize Cx45 expressing neurones within adult mouse spinal cord. eGFP-immunoreactive (eGFP-IR) cells were localized at all rostro-caudal levels to laminae I-III of the dorsal horn (DH), areas associated with nociception. The neuronal rather than glial phenotype of these cells in DH was confirmed by co-localisation of eGFP-IR with the neuronal marker NeuN. Further immunohistochemical studies revealed that eGFP-IR interneurones co-express the calcium-binding protein calbindin, and to a lesser extent calretinin. In contrast, eGFP-IR profiles did not co-localize with either parvalbumin or GAD-67, both of which are linked to inhibitory interneurones. Staining with the primary afferent markers isolectin-B4 (IB4) and calcitonin gene-related peptide revealed that eGFP-IR somata within laminae I-III receive close appositions from the former, presumed non-peptidergic nociceptive afferents of peripheral origin. The presence of 5-HT terminals in close apposition to eGFP-IR interneuronal somata suggests modulation via descending pathways. These data demonstrate a highly localized expression of Cx45 in a population of interneurones within the mouse superficial dorsal horn. The implications of these data in the context of the putative role of Cx45 and gap junctions in spinal somatosensory processing and pain are discussed.
Collapse
Affiliation(s)
- R J Chapman
- Institute for Membrane and Systems Biology, University of Leeds, Leeds LS2 9JT, UK
| | | | | | | | | | | |
Collapse
|
38
|
Bao M, Kanter EM, Huang RYC, Maxeiner S, Frank M, Zhang Y, Schuessler RB, Smith TW, Townsend RR, Rohrs HW, Berthoud VM, Willecke K, Laing JG, Yamada KA. Residual Cx45 and its relationship to Cx43 in murine ventricular myocardium. Channels (Austin) 2011; 5:489-99. [PMID: 22127232 DOI: 10.4161/chan.5.6.18523] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Gap junction channels in ventricular myocardium are required for electrical and metabolic coupling between cardiac myocytes and for normal cardiac pump function. Although much is known about expression patterns and remodeling of cardiac connexin(Cx)43, little is known about the less abundant Cx45, which is required for embryonic development and viability, is downregulated in adult hearts, and is pathophysiologically upregulated in human end-stage heart failure. We applied quantitative immunoblotting and immunoprecipitation to native myocardial extracts, immunogold electron microscopy to cardiac tissue and membrane sections, electrophysiological recordings to whole hearts, and high-resolution tandem mass spectrometry to Cx45 fusion protein, and developed two new tools, anti-Cx45 antisera and Cre(+);Cx45 floxed mice, to facilitate characterization of Cx45 in adult mammalian hearts. We found that Cx45 represents 0.3% of total Cx protein (predominantly 200 fmol Cx43 protein/μg ventricular protein) and colocalizes with Cx43 in native ventricular gap junctions, particularly in the apex and septum. Cre(+);Cx45 floxed mice express 85% less Cx45, but do not exhibit overt electrophysiologic abnormalities. Although the basal phosphorylation status of native Cx45 remains unknown, CaMKII phosphorylates 8 Ser/Thr residues in Cx45 in vitro. Thus, although downregulation of Cx45 does not produce notable deficits in electrical conduction in adult, disease-free hearts, Cx45 is a target of the multifunctional kinase CaMKII, and the phosphorylation status of Cx45 and the role of Cx43/Cx45 heteromeric gap junction channels in both normal and diseased hearts merits further investigation.
Collapse
Affiliation(s)
- Mingwei Bao
- Washington University School of Medicine, St. Louis, MO, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
39
|
Blankenship AG, Hamby AM, Firl A, Vyas S, Maxeiner S, Willecke K, Feller MB. The role of neuronal connexins 36 and 45 in shaping spontaneous firing patterns in the developing retina. J Neurosci 2011; 31:9998-10008. [PMID: 21734291 PMCID: PMC3142875 DOI: 10.1523/jneurosci.5640-10.2011] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [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: 10/26/2010] [Revised: 05/17/2011] [Accepted: 05/23/2011] [Indexed: 12/27/2022] Open
Abstract
Gap junction coupling synchronizes activity among neurons in adult neural circuits, but its role in coordinating activity during development is less known. The developing retina exhibits retinal waves--spontaneous depolarizations that propagate among retinal interneurons and drive retinal ganglion cells (RGCs) to fire correlated bursts of action potentials. During development, two connexin isoforms, connexin 36 (Cx36) and Cx45, are expressed in bipolar cells and RGCs, and therefore provide a potential substrate for coordinating network activity. To determine whether gap junctions contribute to retinal waves, we compared spontaneous activity patterns using calcium imaging, whole-cell recording, and multielectrode array recording in control, single-knock-out (ko) mice lacking Cx45 and double-knock-out (dko) mice lacking both isoforms. Wave frequency, propagation speed, and bias in propagation direction were similar in control, Cx36ko, Cx45ko, and Cx36/45dko retinas. However, the spontaneous firing rate of individual retinal ganglion cells was elevated in Cx45ko retinas, similar to Cx36ko retinas (Hansen et al., 2005; Torborg and Feller, 2005), a phenotype that was more pronounced in Cx36/45dko retinas. As a result, spatial correlations, as assayed by nearest-neighbor correlation and functional connectivity maps, were significantly altered. In addition, Cx36/45dko mice had reduced eye-specific segregation of retinogeniculate afferents. Together, these findings suggest that although Cx36 and Cx45 do not play a role in gross spatial and temporal propagation properties of retinal waves, they strongly modulate the firing pattern of individual RGCs, ensuring strongly correlated firing between nearby RGCs and normal patterning of retinogeniculate projections.
Collapse
Affiliation(s)
- Aaron G. Blankenship
- Neurosciences Graduate Program, University of California, San Diego, La Jolla, California 92093
- Department of Molecular and Cell Biology
| | | | - Alana Firl
- Vision Sciences Graduate Program, Department of Optometry, and
| | - Shri Vyas
- Department of Molecular and Cell Biology
| | - Stephan Maxeiner
- LIMES (Life and Medical Sciences) Institute, University of Bonn, 53115 Bonn, Germany
| | - Klaus Willecke
- LIMES (Life and Medical Sciences) Institute, University of Bonn, 53115 Bonn, Germany
| | - Marla B. Feller
- Department of Molecular and Cell Biology
- Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California 94720, and
| |
Collapse
|
40
|
Zlomuzica A, Reichinnek S, Maxeiner S, Both M, May E, Wörsdörfer P, Draguhn A, Willecke K, Dere E. Deletion of connexin45 in mouse neurons disrupts one-trial object recognition and alters kainate-induced gamma-oscillations in the hippocampus. Physiol Behav 2010; 101:245-53. [PMID: 20471991 DOI: 10.1016/j.physbeh.2010.05.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2009] [Revised: 04/16/2010] [Accepted: 05/07/2010] [Indexed: 10/19/2022]
Abstract
Neuronal gap junctions, allowing fast intercellular electrotonic signal transfer, have been implicated in mechanisms governing learning and memory processes. We have examined conditional neuron-directed (Cx45fl/fl:Nestin-Cre) connexin45 deficient mice in terms of behavioral and electrophysiological correlates of learning and memory. Behavioral habituation to a novel environment and motor learning were not changed in these mice. Novel object recognition after delays of up to 60min was impaired in neuronal Cx45 deficient mice. However, object-place recognition was not significantly different from controls. Analysis of enhanced green fluorescent reporter protein expression controlled by the endogenous mouse Cx45 promoter in the brain of neuronal Cx45 deficient mice suggested that Cx45 is expressed in the perirhinal cortex and the CA3 subregion of the hippocampus. The neuronal Cx45 deficient mice were also examined for aberrations in the generation and synchronization of network oscillations in the hippocampus. General excitability, synaptic short time plasticity, and spontaneous high-frequency oscillations (sharp-wave ripples) in the hippocampus were not different from controls. However, bath stimulation of hippocampal slices with kainate induced significantly lower gamma-oscillation amplitudes in the CA3, but not in the CA1 subfield of the neuronal Cx45 deficient mice. Additionally, they exhibited a significantly larger full width half maximum of the frequency distribution in the CA1 subfield as compared to the controls. In conclusion, the neuron-directed deletion of Cx45 impaired one-trial novel object recognition and altered kainate-induced gamma-oscillations possibly via the disruption of inter-neuronal gap junctional communication in the hippocampus or perirhinal cortex.
Collapse
Affiliation(s)
- A Zlomuzica
- Institute of Experimental Psychology, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Kaiser P, Weise A, Maxeiner S, Nolden F, Borck A, Forst T, Pfützner A. Laboruntersuchung zur Effizienz der Mischung von NPH-Insulin in Kartuschen mit unterschiedlicher Anzahl von Mischkugeln. DIABETOL STOFFWECHS 2010. [DOI: 10.1055/s-0030-1253741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
42
|
Dedek K, Breuninger T, de Sevilla Müller LP, Maxeiner S, Schultz K, Janssen-Bienhold U, Willecke K, Euler T, Weiler R. A novel type of interplexiform amacrine cell in the mouse retina. Eur J Neurosci 2009; 30:217-28. [DOI: 10.1111/j.1460-9568.2009.06808.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
43
|
Hanner F, von Maltzahn J, Maxeiner S, Toma I, Sipos A, Krüger O, Willecke K, Peti-Peterdi J. Connexin45 is expressed in the juxtaglomerular apparatus and is involved in the regulation of renin secretion and blood pressure. Am J Physiol Regul Integr Comp Physiol 2008; 295:R371-80. [PMID: 18579650 DOI: 10.1152/ajpregu.00468.2007] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Connexin (Cx) proteins are known to play a role in cell-to-cell communication via intercellular gap junction channels or transiently open hemichannels. Previous studies have identified several connexin isoforms in the juxtaglomerular apparatus (JGA), but the vascular connexin isoform Cx45 has not yet been studied in this region. The present work aimed to identify in detail the localization of Cx45 in the JGA and to suggest a functional role for Cx45 in the kidney using conditions where Cx45 expression or function was altered. Using mice that express lacZ coding DNA under the control of the Cx45 promoter, we observed beta-galactosidase staining in cortical vasculature and glomeruli, with specific localization to the JGA region. Renal vascular localization of Cx45 was further confirmed with the use of conditional Cx45-deficient (Cx45fl/fl:Nestin-Cre) mice, which express enhanced green fluorescence protein (EGFP) instead of Cx45 only in cells that, during development, expressed the intermediate filament nestin. EGFP fluorescence was found in the afferent and efferent arteriole smooth muscle cells, in the renin-producing juxtaglomerular cells, and in the extra- and intraglomerular mesangium. Cx45fl/fl:Nestin-Cre mice exhibited increased renin expression and activity, as well as higher systemic blood pressure. The propagation of mechanically induced calcium waves was slower in cultured vascular smooth muscle cells (VSMCs) from Cx45fl/fl:Nestin-Cre mice and in control VSMC treated with a Cx45 gap mimetic peptide that inhibits Cx45 gap junctional communication. VSMCs allowed the cell-to-cell passage of the gap junction permeable dye Lucifer yellow, and calcium wave propagation was not altered by addition of the ATP receptor blocker suramin, suggesting that Cx45 regulates calcium wave propagation via direct gap junction coupling. In conclusion, the localization of Cx45 to the JGA and functional data from Cx45fl/fl:Nestin-Cre mice suggest that Cx45 is involved in the propagation of JGA vascular signals and in the regulation of renin release and blood pressure.
Collapse
Affiliation(s)
- Fiona Hanner
- Department of Physiology, Zilkha Neurogenetic Institute, University of Southern California, 1501 San Pablo St., ZNI 335, Los Angeles, CA 90033, USA
| | | | | | | | | | | | | | | |
Collapse
|
44
|
Gallwitz B, Lüddeke HJ, Maxeiner S, Grundner M, Kaiser M. Mit oralen Antidiabetika behandelte Patienten mit Typ-2-Diabetes nehmen signifikant an Gewicht ab, wenn bei Einleitung einer Therapie mit Insulindetemir Sulfonylharnstoffe oder Thiazolidindione abgesetzt werden: Ergebnisse von PREDICTIVE™. DIABETOL STOFFWECHS 2008. [DOI: 10.1055/s-2008-1076351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
45
|
Wörsdörfer P, Maxeiner S, Markopoulos C, Kirfel G, Wulf V, Auth T, Urschel S, von Maltzahn J, Willecke K. Connexin expression and functional analysis of gap junctional communication in mouse embryonic stem cells. Stem Cells 2007; 26:431-9. [PMID: 18055446 DOI: 10.1634/stemcells.2007-0482] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Gap junctional intercellular communication (GJIC) has been suggested to be necessary for cellular proliferation and differentiation. We wanted to investigate the function of GJIC in mouse embryonic stem (ES) cells using pharmacological inhibitors or a genetic approach to inhibit the expression of connexins, that is, the subunit proteins of gap junction channels. For this purpose, we have analyzed all known connexin genes in mouse ES cells but found only three of them, Cx31, Cx43, and Cx45, to be expressed as proteins. We have demonstrated by coimmunoprecipitation that Cx31 and Cx43, as well as Cx43 and Cx45, probably form heteromeric gap junction channels, whereas Cx31 and Cx45 do not. The pharmacological inhibitors reduced GJIC between ES cells to approximately 3% and initiated apoptosis, suggesting an antiapoptotic effect of GJIC. In contrast to these results, reduction of GJIC to approximately 5% by decreased expression of Cx31 or Cx45 via RNA interference in homozygous Cx43-deficient ES cells did not lead to apoptosis. Additional studies suggested that apoptotic death of ES cells and adult stem cells reported in the literature is likely due to a cytotoxic side effect of the inhibitors and not due to a decrease of GJIC. Using the connexin expression pattern in mouse ES cells, as determined in this study, multiple connexin-deficient ES cells can now be genetically engineered in which the level of GJIC is further decreased, to clarify whether the differentiation of ES cells is qualitatively or quantitatively compromised.
Collapse
Affiliation(s)
- Philipp Wörsdörfer
- Division of Molecular Genetics, Institute of Genetics, University of Bonn, Bonn, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Lüddeke HJ, Sreenan S, Aczel S, Maxeiner S, Yenigun M, Kozlovski P, Gydesen H, Dornhorst A. PREDICTIVE- a global, prospective observational study to evaluate insulin detemir treatment in types 1 and 2 diabetes: baseline characteristics and predictors of hypoglycaemia from the European cohort. Diabetes Obes Metab 2007; 9:428-34. [PMID: 17391171 DOI: 10.1111/j.1463-1326.2006.00677.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [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] [Indexed: 01/16/2023]
Abstract
AIM PREDICTIVEtrade mark (Predictable Results and Experience in Diabetes through Intensification and Control to Target: An International Variability Evaluation) is a large, multi-national, observational study assessing the safety and efficacy of insulin detemir. We report the study design, population characteristics and baseline observations, including cross-sectional analysis, from 19 911 patients with type 1 or 2 diabetes. METHODS Patients with type 1 or 2 diabetes requiring basal insulin are prescribed insulin detemir and followed up for 12-52 weeks. Data on demographics, haemoglobin A(1c) (HbA(1c)), fasting glucose, within-subject fasting glucose variability and weight are collected from patient records (and/or recall for hypoglycaemia). A negative binomial distribution model is used to assess the influence of predictive/confounding variables on hypoglycaemic episodes in insulin-treated patients at baseline. Multi-factorial analysis of covariance is used to evaluate the association of the variables with current body weight and within-subject fasting glucose variability. RESULTS Total hypoglycaemic episodes in the 4 weeks prior to study start were 47.5 per patient-year in patients with type 1 and 9.2 per patient-year in patients with type 2 diabetes. The frequency of hypoglycaemia in insulin-treated patients showed a significant, positive association with duration of diabetes, number of insulin injections and fasting glucose variability but was inversely related to HbA(1c), fasting glucose and body mass index. Weight showed a significant positive association with gender (male > female) and insulin dosage. Weight was also positively associated with fasting glucose variability in patients with type 1 diabetes, and age and number of injections in patients with type 2 diabetes. CONCLUSIONS These baseline data showed that, in addition to the established relationship with intensive treatment and HbA(1c), frequency of hypoglycaemia was positively associated with fasting glucose variability. Follow-up data from PREDICTIVE will provide insights on insulin detemir in diabetes management.
Collapse
|
47
|
Gallwitz B, Maxeiner S, Koenen C, Grundner M, Lüddeke HJ. Die Einleitung einer Insulintherapie mit Insulindetemir bei zuvor mit oralen Antidiabetika behandelten Patienten mit Typ 2 Diabetes verbessert die Blutzuckereinstellung ohne zu einer Gewichtszunahme zu führen: 3-Monats-Daten aus PREDICTIVE™. DIABETOL STOFFWECHS 2007. [DOI: 10.1055/s-2007-982407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
48
|
Gallwitz B, Maxeiner S, Koenen C, Grundner M, Lüddeke HJ. Insulindetemir in Kombination mit oralen Antidiabetika (OAD) verbessert die Blutzuckereinstellung und vermindert Hypoglykämien bei Typ 2 Diabetikern, die zuvor mit OADs und NPH-Insulin oder Insulinglargin behandelt wurden, ohne zu einer Gewichtszunahme zu führen: Ergebnisse von PREDICTIVE™. DIABETOL STOFFWECHS 2007. [DOI: 10.1055/s-2007-982408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
49
|
Krüger O, Maxeiner S, Kim JS, van Rijen HVM, de Bakker JMT, Eckardt D, Tiemann K, Lewalter T, Ghanem A, Lüderitz B, Willecke K. Cardiac morphogenetic defects and conduction abnormalities in mice homozygously deficient for connexin40 and heterozygously deficient for connexin45. J Mol Cell Cardiol 2006; 41:787-97. [PMID: 16919680 DOI: 10.1016/j.yjmcc.2006.07.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [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: 12/06/2005] [Revised: 06/15/2006] [Accepted: 07/08/2006] [Indexed: 10/24/2022]
Abstract
Connexin40 (Cx40) and connexin45 (Cx45) are involved in both cardiac morphogenesis and propagation of electrical activity. We found that Cx40/Cx45 double deficiency (Cx40(-/-)/Cx45(+/-)) causes a variety of cardiac defects leading to high mortality during embryonic development and at birth. The majority of Cx40(-/-)/Cx45(+/-) embryos and postnatal mice suffered from atrioventricular septal defects. Additional cardiac abnormalities, e.g., ventricular septal defects and abnormal myocardial arrangement, occurred at lower abundance. Electrocardiograms of Cx40(-/-)/Cx45(+/+) and Cx40(-/-)/Cx45(+/-) mice revealed prolongation of P-wave, PQ interval and QRS duration compared to controls. Interestingly, in Cx40(-/-)/Cx45(+/-) mice, PQ interval and QRS duration were significantly prolonged compared to Cx40(-/-)/Cx45(+/+) mice. We conclude that the gap junctional proteins Cx40 and Cx45 have overlapping and partially compensatory functions with regard to heart morphogenesis and cardiac conduction. Cx45 might be one of the genetic modifiers that can cause variations in the phenotype of connexin40-deficient animals. Our findings may be particularly relevant for understanding molecular factors contributing to human congenital cardiac diseases.
Collapse
Affiliation(s)
- Olaf Krüger
- Institute of Genetics, Division of Molecular Genetics, University of Bonn, Roemerstr. 164, 53117 Bonn, Germany
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
50
|
Dedek K, Schultz K, Pieper M, Dirks P, Maxeiner S, Willecke K, Weiler R, Janssen-Bienhold U. Localization of heterotypic gap junctions composed of connexin45 and connexin36 in the rod pathway of the mouse retina. Eur J Neurosci 2006; 24:1675-86. [PMID: 17004931 DOI: 10.1111/j.1460-9568.2006.05052.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The primary rod pathway in mammals contains gap junctions between AII amacrine cells and ON cone bipolar cells which relay the rod signal into the cone pathway under scotopic conditions. Two gap junctional proteins, connexin36 (Cx36) and connexin45 (Cx45), appear to play a pivotal role in this pathway because lack of either protein leads to an impairment of visual transmission under scotopic conditions. To investigate whether these connexins form heterotypic gap junctions between ON cone bipolar and AII amacrine cells, we used newly developed Cx45 antibodies and studied the cellular and subcellular distribution of this protein in the mouse retina. Specificity of the Cx45 antibodies was determined, among others, by Western blot and immunostaining of mouse heart, where Cx45 is abundantly expressed. In mouse retina, Cx45 immunosignals were detected in both plexiform layers and the ganglion cell layer. Double staining for Cx45 and Cx36 revealed a partial overlap in the punctate patterns in the ON sublamina of the inner plexiform layer of the retina. We quantified the distributions of these two connexins in the ON sublamina, and detected 30% of the Cx45 signals to be co-localized with or in close apposition to Cx36 signals. Combining immunostaining and intracellular dye injection revealed an overlap or tight association of Cx36 and Cx45 signals on the terminals of injected AII amacrine and two types of ON cone bipolar cells. Our results provide direct evidence for heterotypic gap junctions composed of Cx36 and Cx45 between AII amacrine and certain types of ON cone bipolar cells.
Collapse
Affiliation(s)
- Karin Dedek
- Department of Neurobiology, University of Oldenburg, D-26111 Oldenburg, Germany
| | | | | | | | | | | | | | | |
Collapse
|