Analyse Gewebe-spezifischer Deletionen der cGMP-abhängigen Proteinkinase Typ I in Mäusen

Das gasf?xF6;rmige Signalmolek?xFC;l Stickstoffmonoxid (NO) ist an der Steuerung vieler physiologischer Prozesse beteiligt. Zahlreiche Studien weisen darauf hin, dass NO die Synthese des "second Messengers" cGMP bewirkt, welcher die cGMP-abh?xE4;ngige Proteinkinase Typ I (cGKI) aktiviert. Um die in vivo-Funktion der cGKI aufzukl?xE4;ren, wurden bereits konventionelle cGKI Knockout M?xE4;use generiert und analysiert. Da diese Nullmutanten einen multiplen Ph?xE4;notyp und eine stark verminderte Lebenserwartung aufweisen, k?xF6;nnen bestimmte Fragestellungen mit diesen Tieren nicht untersucht werden. Die Probleme, die sich aus der Deletion des cGKI Gens im gesamten Organismus ergeben, konnten durch die Methode der konditionalen somatischen Mutagenese mit Hilfe des Cre/loxP-Rekombinationssystems umgangen werden. Diese Technik erm?xF6;glicht es, ein Gen Zeit- und Gewebe-spezifisch auszuschalten und damit den schwerwiegenden Ph?xE4;notyp der konventionellen cGKI Mutanten zu umgehen. Ziel der Arbeit war es, konditional cGKI-defiziente M?xE4;use zu generieren, die cGKI Expression in diesen Tieren zu analysieren und deren Ph?xE4;notyp zu charakteriesieren. In dieser Arbeit sind vier konditional cGKI-defiziente Mausmutanten beschrieben, welche einen selektiven Verlust der cGKI im jeweils gew?xFC;nschten Gewebe (Hippocampus, Purkinje Zellen des Kleinhirns, Kardiomyozyten oder viszerale und vaskul?xE4;re glatte Muskelzellen) zeigten. Dadurch konnten erstmals Gewebe-spezifische Funktionen der cGKI in erwachsenen M?xE4;usen untersucht werde

Impairment of LTD and cerebellar learning by Purkinje cell–specific ablation of cGMP-dependent protein kinase I

The molecular basis for cerebellar plasticity and motor learning remains controversial. Cerebellar Purkinje cells (PCs) contain a high concentration of cGMP-dependent protein kinase type I (cGKI). To investigate the function of cGKI in long-term depression (LTD) and cerebellar learning, we have generated conditional knockout mice lacking cGKI selectively in PCs. These cGKI mutants had a normal cerebellar morphology and intact synaptic calcium signaling, but strongly reduced LTD. Interestingly, no defects in general behavior and motor performance could be detected in the LTD-deficient mice, but the mutants exhibited an impaired adaptation of the vestibulo-ocular reflex (VOR). These results indicate that cGKI in PCs is dispensable for general motor coordination, but that it is required for cerebellar LTD and specific forms of motor learning, namely the adaptation of the VOR

cGMP-Dependent Protein Kinase I Mediates the Negative Inotropic Effect of cGMP in the Murine Myocardium

Wegener J, Nawrath H, Wolfsgruber W, et al. cGMP-Dependent Protein Kinase I Mediates the Negative Inotropic Effect of cGMP in the Murine Myocardium. Circulation Research. 2002;90(1):18-20.To study the role of cGMP-dependent protein kinase I (cGKI) for cardiac contractility, force of contraction (Fc) was studied in electrically driven heart muscle from wild-type (WT) mice and from conventional and conditional cGKI knockout mice. Both 8-Br-cGMP and 8-pCPT-cGMP reduced Fc in cardiac muscle from juvenile WT but not from juvenile cGKI-null mutants. Similarly, the cGMP analogues reduced Fcin forskolin-stimulated ventricular muscle from WT mice but not from cGKI-null mutants. In contrast, carbachol reduced Fcin both groups of animals. 8-Br-cGMP reduced Fcalso in heart muscle from adult WT mice but not from adult cardiomyocyte-specific cGKI-knockout mice. These results demonstrate that cGKI mediates the negative inotropic effect of cGMP in the myocardium of juvenile and adult mice

cGMP-Dependent Protein Kinase I Mediates the Negative Inotropic Effect of cGMP in the Murine Myocardium

To study the role of cGMP-dependent protein kinase I (cGKI) for cardiac contractility, force of contraction (F c ) was studied in electrically driven heart muscle from wild-type (WT) mice and from conventional and conditional cGKI knockout mice. Both 8-Br-cGMP and 8-pCPT-cGMP reduced Fc in cardiac muscle from juvenile WT but not from juvenile cGKI-null mutants. Similarly, the cGMP analogues reduced F c in forskolin-stimulated ventricular muscle from WT mice but not from cGKI-null mutants. In contrast, carbachol reduced F c in both groups of animals. 8-Br-cGMP reduced F c also in heart muscle from adult WT mice but not from adult cardiomyocyte-specific cGKI-knockout mice. These results demonstrate that cGKI mediates the negative inotropic effect of cGMP in the myocardium of juvenile and adult mice. </jats:p

Hippocampal cGMP-dependent protein kinase I supports an age- and protein synthesis-dependent component of long-term potentiation but is not essential for spatial reference and contextual memory

cGMP-dependent protein kinase I (cGKI) is expressed in the hippocampus, but its role in hippocampal long-term potentiation (LTP) is controversial. In addition, whether cGKI is involved in spatial learning has not been investigated. To address these issues, we generated mice with a hippocampus-specific deletion of cGKI (cGKIhkomice). Unlike conventional cGKI knock-out mice, cGKIhkomice lack gastrointestinal and cardiovascular phenotypes and have a normal life expectancy, which enables us to analyze hippocampal synaptic plasticity and learning in young and adult animals. Hippocampal LTP after repetitive episodes of theta burst stimulation was impaired in adult (12–14 weeks of age) but not in juvenile (3–4 weeks of age) cGKIhkomice. The difference in LTP between adult control and cGKIhkomice was abolished by the protein synthesis inhibitor anisomycin, suggesting that the impairment of LTP in adult cGKIhkomice reflects a defect in late-phase LTP. Despite their deficit in LTP, adult cGKIhkomutants showed normal performance in a discriminatory water maze and had intact contextual fear conditioning. These results suggest that hippocampal cGKI supports an age- and protein synthesis-dependent form of hippocampal LTP, whereas it is dispensable for hippocampus-dependent spatial reference and contextual memory.</jats:p