Kai Schuh - Academia.edu (original) (raw)

Papers by Kai Schuh

Ziel dieser Arbeit war es, NF-AT1-Gen-defiziente Mauslinien zu erzeugen und die Folgen dieser gen... more Ziel dieser Arbeit war es, NF-AT1-Gen-defiziente Mauslinien zu erzeugen und die Folgen dieser genetischen Manipulation in vivo zu untersuchen. Die Untersuchung sollte die durch die Gendefizienz erwarteten Mängel während der Entwicklung (Embryogenese) und, im Besonderen, die Auswirkungen auf das Immunsytem und die Entwicklung und Differenzierung der T-Zellen aufzeigen. Zur Untersuchung der genomischen Organisation des Maus-NF-AT1-Gens wurde eine genomische l-Phagen-DNA-Bibliothek "gescreent" (durchgeführt von Dr. E. Jankevics, Universität von Riga, Lettland), die entsprechenden l-Phagen, die das NF-AT1-Gen enthielten, isoliert und die DNA präpariert. Nach Analyse der klonierten Phagen (Subklonierung und Sequenzierung) wurde eine Restriktionskarte der entsprechenden Bereiche erstellt und der "targeting-vector" erstellt. Der "targeting-vector" wurde durch Elektroporation in embryonale Stammzellen (ES-Zellen) eingebracht und die Integration in das Genom (&q...

Circulation, 2015

Rationale: The QT interval duration (QTc) reflects cardiac depolarization. It may predispose indi... more Rationale: The QT interval duration (QTc) reflects cardiac depolarization. It may predispose individuals to ventricular tachycardia and sudden cardiac death if prolonged (long QTc), shortened (short QTc) or otherwise unregularly. Whole-genome association studies have linked genetic variations in the neuronal nitric oxide synthase adapter protein NOS1AP to variations in QTc intervals and sudden cardiac death. Hypothesis: We hypothesize NOS1AP functions as an L-type-Ca2+ channel modulator via its interaction with the neuronal nitric oxide synthase NOS1. Therefore, alterations in myocardial NOS1AP expression should temper with QTc intervals and increase susceptibility to rhythm disorders. Methods and results: We generated conditional double transgenic mice by crossbreeding pTRE-6xHN-Nos1AP animals with α-MHC-tTA mice; NOS1AP expression is therefore restricted to cardiomyocytes and under control of doxycycline (Tet-Off system). NOS1AP overexpressing animals were investigated with the ma...

thrombus formation in mice

Hypertension, 2020

Cardiac ANP (atrial natriuretic peptide) moderates arterial blood pressure. The mechanisms mediat... more Cardiac ANP (atrial natriuretic peptide) moderates arterial blood pressure. The mechanisms mediating its hypotensive effects are complex and involve inhibition of the renin-angiotensin-aldosterone system, increased natriuresis, endothelial permeability, and vasodilatation. The contribution of the direct vasodilating effects of ANP to blood pressure homeostasis is controversial because variable levels of the ANP receptor, GC-A (guanylyl cyclase-A), are expressed among vascular beds. Here, we show that ANP stimulates GC-A/cyclic GMP signaling in cultured microvascular pericytes and thereby the phosphorylation of the regulatory subunit of myosin phosphatase 1 by cGMP-dependent protein kinase I. Moreover, ANP prevents the calcium and contractile responses of pericytes to endothelin-1 as well as microvascular constrictions. In mice with conditional inactivation (knock-out) of GC-A in microcirculatory pericytes, such vasodilating effects of ANP on precapillary arterioles and capillaries w...

Biological Chemistry, 2006

Blood coagulation factor XII (FXII, Hageman factor) is a plasma serine protease which is autoacti... more Blood coagulation factor XII (FXII, Hageman factor) is a plasma serine protease which is autoactivated following contact with negatively charged surfaces in a reaction involving plasma kallikrein and high-molecular-weight kininogen (contact phase activation). Active FXII has the ability to initiate blood clotting via the intrinsic pathway of coagulation and inflammatory reactions via the kallikrein-kinin system. Here we have determined FXII-mediated bradykinin formation and clotting in plasma. Western blotting analysis with specific antibodies against various parts of the contact factors revealed that limited activation of FXII is sufficient to promote plasma kallikrein activation, resulting in the conversion of high-molecular-weight kininogen and bradykinin generation. The presence of platelets significantly promoted FXII-initiated bradykinin formation. Similarly,in vitroclotting assays revealed that platelets critically promoted FXII-driven thrombin and fibrin formation. In summar...

The American Journal of Human Genetics, 2021

Upregulated signal flow through RAS and the mitogen-associated protein kinase (MAPK) cascade is t... more Upregulated signal flow through RAS and the mitogen-associated protein kinase (MAPK) cascade is the unifying mechanistic theme of the RASopathies, a family of disorders affecting development and growth. Pathogenic variants in more than 20 genes have been causally linked to RASopathies, the majority having a dominant role in promoting enhanced signaling. Here, we report that SPRED2 loss of function is causally linked to a recessive phenotype evocative of Noonan syndrome. Homozygosity for three different variants-c.187C>T (p.Arg63∗), c.299T>C (p.Leu100Pro), and c.1142_1143delTT (p.Leu381Hisfs∗95)-were identified in four subjects from three families. All variants severely affected protein stability, causing accelerated degradation, and variably perturbed SPRED2 functional behavior. When overexpressed in cells, all variants were unable to negatively modulate EGF-promoted RAF1, MEK, and ERK phosphorylation, and time-course experiments in primary fibroblasts (p.Leu100Pro and p.Leu381Hisfs∗95) documented an increased and prolonged activation of the MAPK cascade in response to EGF stimulation. Morpholino-mediated knockdown of spred2a and spred2b in zebrafish induced defects in convergence and extension cell movements indicating upregulated RAS-MAPK signaling, which were rescued by expressing wild-type SPRED2 but not the SPRED2Leu381Hisfs∗95 protein. The clinical phenotype of the four affected individuals included developmental delay, intellectual disability, cardiac defects, short stature, skeletal anomalies, and a typical facial gestalt as major features, without the occurrence of the distinctive skin signs characterizing Legius syndrome. These features, in part, characterize the phenotype of Spred2-/- mice. Our findings identify the second recessive form of Noonan syndrome and document pleiotropic consequences of SPRED2 loss of function in development.

Journal of Clinical Medicine

Anxiety disorders and depression are common comorbidities in cardiac patients. Mice lacking the s... more 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 pe...

complexes, which regulate cytoplasmic actin networks. Conversely, Mena/VASP deficiency results in... more complexes, which regulate cytoplasmic actin networks. Conversely, Mena/VASP deficiency results in disrupted β-actin assembly, Z- and intercalated disc malformation, and induces dilated cardiomyopathy and conduction Benz et al. Cell Communication and Signaling 2013, 11:56

Circulation, 2007

Background— Neuronal nitric oxide synthase (nNOS) has recently been shown to be a major regulator... more Background— Neuronal nitric oxide synthase (nNOS) has recently been shown to be a major regulator of cardiac contractility. In a cellular system, we have previously shown that nNOS is regulated by the isoform 4b of plasma membrane calcium/calmodulin-dependent ATPase (PMCA4b) through direct interaction mediated by a PDZ domain (PSD 95, Drosophilia Discs large protein and Zona occludens-1) on nNOS and a cognate ligand on PMCA4b. It remains unknown, however, whether this interaction has physiological relevance in the heart in vivo. Methods and Results— We generated 2 strains of transgenic mice overexpressing either human PMCA4b or PMCA ct120 in the heart. PMCA ct120 is a highly active mutant form of the pump that does not interact with or modulate nNOS function. Calcium was extruded normally from PMCA4b-overexpressing cardiomyocytes, but in vivo, overexpression of PMCA4b reduced the β-adrenergic contractile response. This attenuated response was not observed in ct120 transgenic mice. T...

Circulation, 1999

The plasma membrane calmodulin-dependent calcium ATPase (PMCA) is a calcium-extruding enzyme cont... more The plasma membrane calmodulin-dependent calcium ATPase (PMCA) is a calcium-extruding enzyme controlling Ca 2ϩ homeostasis in nonexcitable cells. However, its function in the myocardium is unclear because of the presence of the Na ϩ /Ca 2ϩ exchanger. We approached the question of the physiological function of the calcium pump using a transgenic "gain of function" model. Transgenic rat lines carrying the human PMCA 4 cDNA under control of the ventricle-specific myosin light chain-2 promoter were established, and expression in the myocardium was ascertained at the mRNA, protein, and functional levels. In vivo hemodynamic measurements in adult homozygous animals showed no differences in baseline and increased cardiac performance recruited by volume overload compared with controls. No differences between transgenic and control cardiomyocytes were found in patch clamp voltage dependence, activation/inactivation behavior of the L-type Ca 2ϩ current, or fast [Ca 2ϩ ] i transients (assessed by the Fura-2 method). To test whether the PMCA might be involved in processes other than beat-to-beat regulation of contraction/relaxation, we compared growth processes of neonatal transgenic and control cardiomyocytes. A 1.6-and 2.3-fold higher synthesis rate of total protein was seen in cells from transgenic animals compared with controls on incubation with 2% FCS for 24 hours and 36 hours, respectively. An effect of similar magnitude was observed using 20 mol/L phenylephrine. A 1.4-fold-and 2.0-fold-higher protein synthesis peak was seen in PMCA-overexpressing cardiomyocytes after stimulation with isoproterenol for 12 hours and 24 hours, respectively. Because pivotal parts of the ␣and ␤-adrenergic signal transduction pathways recently have been localized to caveolae, we tested the hypothesis that the PMCA might alter the amplitude of ␣and ␤-adrenergic growth signals by virtue of its localization in caveolae. Biochemical as well as immunocytochemical studies suggested that the PMCA in large part was colocalized with caveolin 3 in caveolae of cardiomyocytes. These results indicate that the sarcolemmal Ca 2ϩ-pump has little relevance for beat-to-beat regulation of contraction/relaxation in adult animals but likely plays a role in regulating myocardial growth, possibly through modulation of caveolar signal transduction.

American Journal of Physiology, 2001

Journal of Experimental Medicine, 1998

The expression of the murine interleukin (IL)-2 receptor α chain/CD25 is strongly induced at the ... more The expression of the murine interleukin (IL)-2 receptor α chain/CD25 is strongly induced at the transcriptional level after T cell activation. We show here that nuclear factor of activated T cell (NF-AT) factors are involved in the control of CD25 promoter induction in T cells. NF-ATp and NF-ATc bind to two sites around positions −585 and −650 located upstream of the proximal CD25 promoter. Immediately 3′ from these NF-AT motifs, nonconsensus sites are located for the binding of AP-1–like factors. Mutations of sites that suppress NF-AT binding impair the induction and strong NF-ATp–mediated transactivation of the CD25 promoter in T cells. In T lymphocytes from NF-ATp–deficient mice, the expression of CD25 is severely impaired, leading to a delayed IL-2 receptor expression after T cell receptor (TCR)/CD3 stimulation. Our data indicate an important role for NF-AT in the faithful expression of high affinity IL-2 receptors and a close link between the TCR-mediated induction of IL-2 and...

European journal of …, 1998

NF-ATp and NF-ATc are the most prominent nuclear NF-AT transcription factors in peripheral T lymp... more NF-ATp and NF-ATc are the most prominent nuclear NF-AT transcription factors in peripheral T lymphocytes. After T cell activation both factors bind to and control the promoters and enhancers of numerous lymphokine and receptor ligand genes. In order to define a specific role for ...

From the ‡Institute for Clinical Biochemistry and Pathobiochemistry, University of Wuerzburg, Jos... more From the ‡Institute for Clinical Biochemistry and Pathobiochemistry, University of Wuerzburg, Josef-Schneider-Strasse 2, D-97080 Wuerzburg, Germany, the Biochemical Research and Study Center, University of Latvia, Ratsupites iela 1, Riga, LV-1067, Latvia, the **Department of Obstetrics and Gynecology, University of Wuerzburg, Josef-Schneider-Str. 2, D-97080 Wuerzburg, Germany, the ‡‡FMP, Krahmerstrasse 6, D-12207 Berlin, Germany, and the ¶Division of Cardiology, Room 1.302 Stopford Building, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom

Background—Calcineurin (CnA) is important in the regulation of myocardial hypertrophy. We demonst... more Background—Calcineurin (CnA) is important in the regulation of myocardial hypertrophy. We demonstrated that targeted proteolysis of the CnA autoinhibitory domain under pathological myocardial workload leads to increased CnA activity in human myocardium. Here, we investigated the proteolytic mechanism leading to activation of CnA. Methods and Results—In patients with diseased myocardium, we found strong nuclear translocation of CnA. In contrast, in normal human myocardium, there was a cytosolic distribution of CnA. Stimulation of rat cardiomyocytes with angiotensin (Ang) II increased calpain activity significantly (433±11%; P<0.01; n=6) and caused proteolysis of the autoinhibitory domain of CnA. Inhibition of calpain by a membrane-permeable calpain inhibitor prevented proteolysis. We identified the cleavage site of calpain in the human CnA sequence at amino acid 424. CnA activity was increased after Ang II stimulation (310±29%; P<0.01; n=6) and remained high after removal of An...

Obsessive-compulsive disorder (OCD) is a common neuropsychiatric disease affecting about 2% of th... more Obsessive-compulsive disorder (OCD) is a common neuropsychiatric disease affecting about 2% of the general population. It is characterized by persistent intrusive thoughts and repetitive ritualized behaviors. While gene variations, malfunction of cortico-striato-thalamo-cortical (CSTC) circuits, and dysregulated synaptic transmission have been implicated in the pathogenesis of OCD, the underlying mechanisms remain largely unknown. Here we show that OCD-like behavior in mice is caused by deficiency of SPRED2, a protein expressed in various brain regions and a potent inhibitor of Ras/ERK-MAPK signaling. Excessive self-grooming, reflecting OCD-like behavior in rodents, resulted in facial skin lesions in SPRED2 knockout (KO) mice. This was alleviated by treatment with the selective serotonin reuptake inhibitor fluoxetine. In addition to the previously suggested involvement of cortico-striatal circuits, electrophysiological measurements revealed altered transmission at thalamo-amygdala s...

Background Hypertensive cardiac remodelling is a major risk factor for cardiovascular morbidity a... more Background Hypertensive cardiac remodelling is a major risk factor for cardiovascular morbidity and a leading cause of chronic heart failure. The activation of the renin-angiotensin system plays an important pathophysiological role in hypertensive cardiac remodelling [1]. C-type natriuretic peptide (CNP) belongs to the natriuretic peptide family. In the cardiovascular system, CNP is secreted from endothelial cells and possibly from cardiac fibroblasts, to act as autocrine/paracrine hormone [2]. It activates the guanylyl cyclase B (GC-B) receptor which synthesizes the second messenger cGMP. In vitro the CNP/GC-B pathway inhibits the proliferation and collagen synthesis of cardiac fibroblasts [3]. Therefore, we aimed to study the cardiac effects of synthetic CNP on Angiotensin II (Ang II)-induced cardiac fibrosis and hypertrophy in vivo.

Brain Sciences

Vocalization is an important part of social communication, not only for humans but also for mice.... more Vocalization is an important part of social communication, not only for humans but also for mice. Here, we show in a mouse model that functional deficiency of Sprouty-related EVH1 domain-containing 2 (SPRED2), a protein ubiquitously expressed in the brain, causes differences in social ultrasound vocalizations (USVs), using an uncomplicated and reliable experimental setting of a short meeting of two individuals. SPRED2 mutant mice show an OCD-like behaviour, accompanied by an increased release of stress hormones from the hypothalamic–pituitary–adrenal axis, both factors probably influencing USV usage. To determine genotype-related differences in USV usage, we analyzed call rate, subtype profile, and acoustic parameters (i.e., duration, bandwidth, and mean peak frequency) in young and old SPRED2-KO mice. We recorded USVs of interacting male and female mice, and analyzed the calls with the deep-learning DeepSqueak software, which was trained to recognize and categorize the emitted USVs...