3369
2008
deu
doctoralthesis
1
2009-11-19
--
2009-11-19
Modulation der Einwärtsgleichrichrichtung von GIRK-Kanälen durch G-Protein Untereinheiten
Modulation of the rectification properties of GIRK channels by G Protein subunits
G-Protein-gekoppelte einwärtsgleichrichtende Kalium-Kanäle sind durch zwei Eigenschaften gekennzeichnet: (I) Die Leitfähigkeit für K+-Ionen ist positiv des Kalium-Gleichgewichtspotentials reduziert und (II) die Kanal-Aktivität wird durch Bindung von G betagamma-Dimere heterotrimerer Gi/o-Proteine reguliert. In der Literatur wurde die Aktivierung von GIRK-Kanälen als eine Zunahme ihrer Offenwahrscheinlichkeit unabhängig vom Membranpotential beschrieben. Die vorliegenden Untersuchungen zeigten, dass es bei starker Aktivierung des GIRK-Kanals durch G betagamma-Dimere auch zu einer Abschwächung der Einwärtsgleichrichtung kommt. Im heterologen Expressionssystem konnte bei Rezeptor-Stimulation mit Agonist die Einwärtsgleichrichtung von GIRK-Kanälen abhängig von der Stärke der Koexpression von G betagamma-Dimeren geschwächt werden. Dieser Effekt entstand nicht durch eine Veränderung der Affinität, mit der Polyamine und Mg2+-Ionen den GIRK-Kanal membranpotentialabhängig blockieren. Die Kinetik, mit der Polyamine den GIRK-Kanal blockieren, war nicht verändert; eine Erhöhung der intrazellulären Mg2+-Konzentration um den Faktor 20 konnte eine Abschwächung der Einwärtsgleichrichtung nicht mindern. Es wurde vermutet, dass eine Änderung der Konformation von Strukturen nahe des Selektivitätsfilters die Abschwächung der Einwärtsgleichrichtung verursacht. Gestützt wurde diese Vermutung zum einen dadurch, dass Ba2+- und Cs+-Ionen, die von extrazellulärer Seite her den Kanal an Strukturen nahe des Selektivitätsfilters blockieren können, unter schwach einwärtsgleichrichtenden Bedingungen eine geringere Bindungsaffinität hatten und zum anderen dadurch, dass das relative Ausmaß des GIRK-Kanal-Blocks durch Cs+-Ionen mit der Stärke der Einwärtsgleichrichtung korrelierte.
G Protein-coupled inwardly rectifying potassium channels (GIRK channels) conduct K+ ions at membrane potentials negative of the potassium reversal potential and are activated by binding of G betagamma subunits of heterotrimeric Gi/o proteins. Activation of GIRK channels was described to be a process, which results in an increase in open probabilty independent of the membrane potential. The investigations of this thesis enhance this modell by supoorting evidence, that the degree of rectification becomes weakened upon strong GIRK channel activation. The weakened inward rectification was not associated with a shift in Mg2+ or polyamine binding affinities towards GIRK. It was concluded, that structeres close to the selectivity filter may be involved in the process, as proposed by the finding, that Cs+ and Ba2+ block (which is considered to take place near the selectivity filter) is less efficient in weakly inward rectifying GIRK channels.
urn:nbn:de:bvb:20-opus-40388
4038
http://www.jbc.org/content/278/2/1037.full
X122709
Leif Hommers
deu
swd
GIRK
deu
swd
Einwärtsgleichrichtung
deu
swd
G Protein
deu
swd
Gi/o
deu
swd
G beta gamma
deu
uncontrolled
GIRK
deu
uncontrolled
Einwärtsgleichrichtung
deu
uncontrolled
G Protein
deu
uncontrolled
Gi/o
deu
uncontrolled
G beta gamma
eng
uncontrolled
GIRK
eng
uncontrolled
Inward Rectification
eng
uncontrolled
G Protein
eng
uncontrolled
Gi/o
eng
uncontrolled
G beta gamma
Biowissenschaften; Biologie
open_access
Institut für Pharmakologie und Toxikologie
Universität Würzburg
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/3369/MDiss_Hommers.pdf
4817
2011
deu
doctoralthesis
1
2011-05-16
--
2011-05-10
Über die Interaktion aktivierter G-Proteine mit G-Protein gekoppelten Rezeptoren
Interaction of activated G Protein with activated G Protein coupled receptors
Aktivierte G-Protein gekoppelte Rezeptoren aktivieren heterotrimere GProteine, in dem sie den Austausch von GDP zu GTP am G-Protein katalysieren. Theoretische Untersuchungen mittels eines vereinfachten kinetischen Modells des Gi/o-Protein Zyklus legen nahe, dass nicht nur GDP-,sondern auch GTP-gebundene Gi/o-Proteine mit aktivierten α2A-adrenergen Rezeptoren (α2A-AR) interagieren können. Demgemäß sollten aktivierte Gi/o-Proteine mit aktivierten α2A-AR vermehrt interagieren, wenn mehr α2A-AR aktiviert werden als für eine maximale G-Protein Aktivierung nötig sind. Dies sollte zu einer paradoxen Deaktivierung von Gi/o-Proteinen und deren Effektorproteinen, z.B. dem G-Protein gekoppelten, einwärtsgleichrichtenden Kaliumkanal (GIRK-Kanal) führen. Mittels FRET lässt sich in lebenden und in permeabilisierten Zellen unter Kontrolle der intrazellulären Nukleotide die Aktivierung von α2A-AR, die Interaktion von Gi/o-Proteinen mit α2A-AR und die Aktivierung von Gi/o-Proteinen bestimmen. Die Arbeit zeigt auf mehreren Ebenen, dass Go-Proteine mit aktivierten α2A-AR interagieren und im nukleotidfreiem Zustand sequestriert werden können: (I) Go-Proteine,irreversibel durch GTPγS aktiviert werden abhängig von der Rezeptor Aktivierung in Abwesenheit von Nukleotiden deaktiviert, (II) Go-Proteine interagieren in Gegenwart niedriger Nukleotidkonzentrationen in wesentlich größer Fraktion mit aktivierten α2A-AR als in Gegenwart hoher Nukleotidkonzentrationen, (III) Go Proteine können in Gegenwart niedriger GTP und GTPγS-Konzentrationen bei Aktivierung des α2A-AR inaktiviert werden. Die Arbeit zeigt exemplarisch an der Signalkaskade des α2A-AR und Go, dass der G-Protein Zyklus in lebenden Zellen reversibel ist, woraus eine Deaktivierung aktivierter G-Proteine und aktivierter G-Protein Effektoren resultieren kann. Dies erklärt paradoxe Befunde zur Deaktivierung von GIRK-Kanälen in Myozyten durch A1-Rezeptoren.
G protein coupled receptors activate heterotrimeric G proteins by catalyzing the exchange of GDP with GTP at the Gα subunit. Kinetic modelling of the Gi/o protein cycle suggests, that both GDP- and GTP-bound Gi/o proteins interact with activated α2A-adrenergic receptors (α2A-AR). Consequently, upon activating more α2A-AR then required for maximal Gi/o protein activation, the interaction of activated Gi/o proteins with activated α2A-AR will become incresingly prominent and ultimately lead to a paradoxic deactivation of Gi/o proteins and their effectors such as G protein coupled inwardly rectifying potassium channels. Using means of FRET allows the detection of the receptor activation, receptor/G protein interaction and G protein activation in single living cells and in single permeabilized cells while controlling the intracellular nucleotide composition.Data suggest, that activated Go proteins may be sequestrated at activated α2A-AR in their nucleotide-free state: (I) Go proteins irreversibly activated by GTPγS become inactivated upon receptor stimulation in the absence of nucleotides, (II) Go proteins interact with activated α2A-AR to a large extent in the presence of low concentrations of nucleotide, (III) Go proteins may be inactivated upon activation of α2A-AR in the presence of low concentrations of GTP or GTPγS. Taken together, the data demonstrate the reversibility of the G protein cycle in living cells for the paradigm α2A-AR/Go pathway. The data thereby explain the paradoxic inactivation of G protein coupled inwardly rectifying potassium channels in myocytes upon activation of adenosine A1 receptors.
urn:nbn:de:bvb:20-opus-56576
5657
X123507
Deutsches Urheberrecht
Leif Hommers
deu
swd
G-Protein gekoppelte Rezeptoren
eng
uncontrolled
G protein coupled receptor
Biowissenschaften; Biologie
open_access
Institut für Pharmakologie und Toxikologie
Universität Würzburg
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/4817/Diss_Hommers_2011.pdf
11823
2014
eng
376
8
article
1
2015-08-20
--
--
Experimental heart failure causes depression-like behavior together with differential regulation of inflammatory and structural genes in the brain
Background: Depression and anxiety are common and independent outcome predictors in patients with chronic heart failure (CHF). However, it is unclear whether CHF causes depression. Thus, we investigated whether mice develop anxiety- and depression-like behavior after induction of ischemic CHF by myocardial infarction (MI).
Methods and Results: In order to assess depression-like behavior, anhedonia was investigated by repeatedly testing sucrose preference for 8 weeks after coronary artery ligation or sham operation. Mice with large MI and increased left ventricular dimensions on echocardiography (termed CHF mice) showed reduced preference for sucrose, indicating depression-like behavior. 6 weeks after MI, mice were tested for exploratory activity, anxiety-like behavior and cognitive function using the elevated plus maze (EPM), light-dark box (LDB), open field (OF), and object recognition (OR) tests. In the EPM and OF, CHF mice exhibited diminished exploratory behavior and motivation despite similar movement capability. In the OR, CHF mice had reduced preference for novelty and impaired short-term memory. On histology, CHF mice had unaltered overall cerebral morphology. However, analysis of gene expression by RNA-sequencing in prefrontal cortical, hippocampal, and left ventricular tissue revealed changes in genes related to inflammation and cofactors of neuronal signal transduction in CHF mice, with Nr4a1 being dysregulated both in prefrontal cortex and myocardium after MI.
Conclusions: After induction of ischemic CHF, mice exhibited anhedonic behavior, decreased exploratory activity and interest in novelty, and cognitive impairment. Thus, ischemic CHF leads to distinct behavioral changes in mice analogous to symptoms observed in humans with CHF and comorbid depression.
Frontiers in Behavioral Neuroscience
10.3389/fnbeh.2014.00376
1662-5153
urn:nbn:de:bvb:20-opus-118234
Frontiers in Behavioral Neuroscience 8:376. doi:10.3389/fnbeh.2014.00376
Anna Frey
Sandy Popp
Antonia Post
Simon Langer
Marc Lehmann
Ulrich Hofmann
Anna-Leena Siren
Leif Hommers
Angelika Schmitt
Tatyana Strekalova
Georg Ertl
Klaus-Peter Lesch
Stefan Frantz
eng
uncontrolled
chronic heart failure
eng
uncontrolled
myocardial infarction
eng
uncontrolled
anxiety
eng
uncontrolled
depression
eng
uncontrolled
mice
Krankheiten
open_access
Neurochirurgische Klinik und Poliklinik
Klinik und Poliklinik für Psychiatrie, Psychosomatik und Psychotherapie
Medizinische Klinik und Poliklinik I
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/11823/014_Frey_FRONTIERS_IN_BEHAVIORAL_NEUROSCIENCE.pdf
25986
2021
eng
2
3
article
1
2022-03-10
--
--
Inhibition of acid sphingomyelinase increases regulatory T cells in humans
Genetic deficiency for acid sphingomyelinase or its pharmacological inhibition has been shown to increase Foxp3\(^+\) regulatory T-cell frequencies among CD4\(^+\) T cells in mice. We now investigated whether pharmacological targeting of the acid sphingomyelinase, which catalyzes the cleavage of sphingomyelin to ceramide and phosphorylcholine, also allows to manipulate relative CD4\(^+\) Foxp3\(^+\) regulatory T-cell frequencies in humans. Pharmacological acid sphingomyelinase inhibition with antidepressants like sertraline, but not those without an inhibitory effect on acid sphingomyelinase activity like citalopram, increased the frequency of Foxp3\(^+\) regulatory T cell among human CD4\(^+\) T cells in vitro. In an observational prospective clinical study with patients suffering from major depression, we observed that acid sphingomyelinase-inhibiting antidepressants induced a stronger relative increase in the frequency of CD4\(^+\) Foxp3\(^+\) regulatory T cells in peripheral blood than acid sphingomyelinase-non- or weakly inhibiting antidepressants. This was particularly true for CD45RA\(^-\) CD25\(^{high}\) effector CD4\(^+\) Foxp3\(^+\) regulatory T cells. Mechanistically, our data indicate that the positive effect of acid sphingomyelinase inhibition on CD4\(^+\) Foxp3\(^+\) regulatory T cells required CD28 co-stimulation, suggesting that enhanced CD28 co-stimulation was the driver of the observed increase in the frequency of Foxp3+ regulatory T cells among human CD4\(^+\) T cells. In summary, the widely induced pharmacological inhibition of acid sphingomyelinase activity in patients leads to an increase in Foxp3+ regulatory T-cell frequencies among CD4\(^+\) T cells in humans both in vivo and in vitro.
Brain Communications
10.1093/braincomms/fcab020
urn:nbn:de:bvb:20-opus-259868
publish
Brain Communications (2021) 3:2, fcab020. https://doi.org/10.1093/braincomms/fcab020
false
true
CC BY: Creative-Commons-Lizenz: Namensnennung 4.0 International
Teresa Wiese
Fabio Dennstädt
Claudia Hollmann
Saskia Stonawski
Catherina Wurst
Julian Fink
Erika Gorte
Putri Mandasari
Katharina Domschke
Leif Hommers
Bernard Vanhove
Fabian Schumacher
Burkard Kleuser
Jürgen Seibel
Jan Rohr
Mathias Buttmann
Andreas Menke
Jürgen Schneider-Schaulies
Niklas Beyersdorf
eng
uncontrolled
acid sphingomyelinase
eng
uncontrolled
antidepressants
eng
uncontrolled
major depression
eng
uncontrolled
regulatory T cells
eng
uncontrolled
sphingolipids
Medizin und Gesundheit
open_access
Institut für Virologie und Immunbiologie
Neurologische Klinik und Poliklinik
Klinik und Poliklinik für Psychiatrie, Psychosomatik und Psychotherapie
Institut für Organische Chemie
Deutsches Zentrum für Herzinsuffizienz (DZHI)
Förderzeitraum 2021
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/25986/fcab020_2021.pdf
24273
2021
eng
14
10
article
1
--
2021-07-14
--
5-HTT Deficiency in Male Mice Affects Healing and Behavior after Myocardial Infarction
Anxiety disorders and depression are common comorbidities in cardiac patients. Mice lacking the serotonin transporter (5-HTT) exhibit increased anxiety-like behavior. However, the role of 5-HTT deficiency on cardiac aging, and on healing and remodeling processes after myocardial infarction (MI), remains unclear. Cardiological evaluation of experimentally naïve male mice revealed a mild cardiac dysfunction in ≥4-month-old 5-HTT knockout (−/−) animals. Following induction of chronic cardiac dysfunction (CCD) by MI vs. sham operation 5-HTT−/− mice with infarct sizes >30% experienced 100% mortality, while 50% of 5-HTT+/− and 37% of 5-HTT+/+ animals with large MI survived the 8-week observation period. Surviving (sham and MI < 30%) 5-HTT−/− mutants displayed reduced exploratory activity and increased anxiety-like behavior in different approach-avoidance tasks. However, CCD failed to provoke a depressive-like behavioral response in either 5-Htt genotype. Mechanistic analyses were performed on mice 3 days post-MI. Electrocardiography, histology and FACS of inflammatory cells revealed no abnormalities. However, gene expression of inflammation-related cytokines (TGF-β, TNF-α, IL-6) and MMP-2, a protein involved in the breakdown of extracellular matrix, was significantly increased in 5-HTT−/− mice after MI. This study shows that 5-HTT deficiency leads to age-dependent cardiac dysfunction and disrupted early healing after MI probably due to alterations of inflammatory processes in mice.
Journal of Clinical Medicine
2077-0383
10.3390/jcm10143104
urn:nbn:de:bvb:20-opus-242739
2021-08-01T16:39:17+00:00
sword
swordwue
attachment; filename=deposit.zip
c26d74e7ca9ddb8ea8bed92f5c7da38f
Journal of Clinical Medicine 2021, 10(14), 3104; https://doi.org/10.3390/jcm10143104
false
true
CC BY: Creative-Commons-Lizenz: Namensnennung 4.0 International
Sandy Popp
Angelika Schmitt-Böhrer
Simon Langer
Ulrich Hofmann
Leif Hommers
Kai Schuh
Stefan Frantz
Klaus-Peter Lesch
Anna Frey
eng
uncontrolled
chronic heart failure
eng
uncontrolled
myocardial infarction
eng
uncontrolled
serotonin transporter deficient mice
eng
uncontrolled
anxiety
eng
uncontrolled
depression
eng
uncontrolled
behavior
eng
uncontrolled
inflammation
Medizin und Gesundheit
open_access
Physiologisches Institut
Klinik und Poliklinik für Psychiatrie, Psychosomatik und Psychotherapie
Medizinische Klinik und Poliklinik I
Import
Förderzeitraum 2021
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/24273/jcm-10-03104-v2.pdf
26205
2022
eng
13
article
1
--
2022-02-22
--
Proteolytic cleavage of the extracellular domain affects signaling of parathyroid hormone 1 receptor
Parathyroid hormone 1 receptor (PTH1R) is a member of the class B family of G protein-coupled receptors, which are characterized by a large extracellular domain required for ligand binding. We have previously shown that the extracellular domain of PTH1R is subject to metalloproteinase cleavage in vivo that is regulated by ligand-induced receptor trafficking and leads to impaired stability of PTH1R. In this work, we localize the cleavage site in the first loop of the extracellular domain using amino-terminal protein sequencing of purified receptor and by mutagenesis studies. We further show, that a receptor mutant not susceptible to proteolytic cleavage exhibits reduced signaling to G\(_s\) and increased activation of G\(_q\) compared to wild-type PTH1R. These findings indicate that the extracellular domain modulates PTH1R signaling specificity, and that its cleavage affects receptor signaling.
Frontiers in Endocrinology
1664-2392
10.3389/fendo.2022.839351
urn:nbn:de:bvb:20-opus-262055
2022-03-28T07:39:08+00:00
sword
swordwue
attachment; filename=deposit.zip
31622eb3a401a5bf75d8667831d62869
Frontiers in Endocrinology (2022) 13:839351. doi:10.3389/fendo.2022.839351
232944
false
true
CC BY: Creative-Commons-Lizenz: Namensnennung 4.0 International
Christoph Klenk
Leif Hommers
Martin J. Lohse
eng
uncontrolled
GPCRs
eng
uncontrolled
parathyroid hormone 1 receptor
eng
uncontrolled
matrix metalloproteinase
eng
uncontrolled
ectodomain cleavage
eng
uncontrolled
biased signaling
Medizin und Gesundheit
open_access
Institut für Pharmakologie und Toxikologie
Klinik und Poliklinik für Psychiatrie, Psychosomatik und Psychotherapie
Rudolf-Virchow-Zentrum
OpenAIRE
Import
Comprehensive Cancer Center Mainfranken
Förderzeitraum 2022
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/26205/fendo-13-839351.pdf