Furthering our understanding of the redox regulation of Protein Kinase A in the cardiovascular system

Cardiovascular disease is the leading cause of death in the UK, as it is in other Western societies. This burden continues to grow as the population lives longer, exerting an important proteins (known as PKA) becomes altered (oxidised) when the levels of oxidant molecules increase in the heart and in blood vessels. Thus, PKA may become altered during times, for example during disease, when oxidant levels in the tissues of the cardiovascular system are changed. We think this modification of PKA may be important in the complex events leading to cardiovascular dysfunction, including high blood pressure (hypertension) or heart failure. In simple terms the alteration involves PKA becoming oxidised and we think this alteration changes how it functions, which likely impacts on the development of cardiovascular disease. We propose experiments that will allow us to better understand how the oxidative alteration modifies the activity or function of PKA, and thereafter how these changes influence the development of cardiovascular disease. In the longer term, we envisage the proposed studies may lead to new drugs that target PKA to limit the development of cardiovascular disease. This is important as currently there is a lack of pharmacotherapy that adequately combats this common health problem.

We originally discovered that Type I PKA protein, which is crucially important in cardiovascular function, is susceptible to oxidation. This kinase, which is expressed widely in the cardiovascular system, forms a homo interprotein disulfide within the kinases regulatory RIalpha subunits during oxidant stress. Our primary objective is to increase the understanding of the redox regulation of this isoform of PKA in the heart and in blood vessels. We want to do this because dysregulated PKA is broadly implicated in the pathogenesis of cardiovascular disease, times when the kinase may encounter elevated oxidative stress which promotes its oxidation. We have developed methods allowing us to routinely monitor PKA oxidation and will use biochemical methods and physiological measurement of cardiac function to monitor the changes in the heart or in blood vessel resulting from oxidation of this kinase. We have developed a transgenic knock in murine model in which the redox sensor cysteine thiols in this specific kinase are replaced to make the PKA RIalpha 'redox inactive'. By comparing the responses of these C17S PKA RIalpha knock in mice to wild type controls, we will be able to more clearly define the role of PKA oxidation in the development of cardiovascular disease - aiding our long term aim of trying to combat this prevalent and escalating, global healthcare burden.

This application focuses on the functional impact of PKA oxidation and its potential role in the pathogenesis of cardiovascular disease. PKA itself is an intensely studied kinase, and our identification of a novel mechanism involved in its regulation may help generate new ideas in many research areas. PKA is expressed in multiple tissues and has a broad impact on many cellular functions. Consistent with this, dysregulation of PKA is widely implicated in the pathogenesis of multiple diseases, not just those of the cardiovascular system - but also cancer and neurological disorders. Our pilot data clearly indicate that PKA oxidation to the disulfide markedly occurs during scenarios where myocardial mitophagy are induced such as starvation, as well as in blood vessels during pro-oxidant, hypertension-inducing interventions (e.g. administration of Ang II). This is evident from our clear-cut pilot studies showing food withdrawal induces PKA RIalpha oxidation in heart, as well as others where Angiotensin II (administered in vivo to mice) stimulates oxidation of this kinase in blood vessels. A wide range of scientists in different albeit complementary specialties will potentially benefit from the proposed studies, including physiologists, biochemists, structural biologists, medicinal chemists and pharmacologists. Given the ultimate translational potential of these studies, the project could impact positively on healthcare professionals at multiple levels within this sector. Ultimately, new therapies could arise from this work, which would aid clinicians and their colleagues in reducing the burden of highly prevalent cardiovascular diseases such as hypertension heart failure. Effective therapies against these highly prevalent conditions that negatively influence the health and wealth of society would strengthen the position of policy makers, healthcare managers, doctors and related staff and end-users as it could save an enormous amount of resource that could then be reallocated to address other problems. As PKA dysregulation is also implicated in the pathogenesis of cancer and some neurological disorders, our proposed studies may potentially lead to new understanding or therapies that alleviate those conditions. This would provide further significant wealth benefits to society, as well as reducing other negative aspects associated with the high morbidity and mortality caused by those diseases. Overall, it is evident that society at many levels may have much to gain from a better understanding of the redox control of PKA. This potentially could have a huge impact - not least because of the translational potential that could help in the fight against several diseases highly prevalent in the aging population.