ER stress dysregulates ER proteostasis, which activates the transcription factor, ATF6, an inducer of genes that enhance protein folding and restore proteostasis. Due to increased protein synthesis, it is possible that protein folding and, thus, ER proteostasis are challenged during cardiac myocyte growth. However, it is not known whether ATF6 is activated, and if so, what its function is during hypertrophic growth of cardiac myocytes.
Pharmacologic activation of stress-responsive signaling pathways provides a promising approach for ameliorating imbalances in proteostasis associated with diverse diseases. However, this approach has not been employed in vivo. In recent research done in the Glembotski lab, we used a mouse model of myocardial ischemia/reperfusion to show that selective pharmacologic activation of the ATF6 arm of the unfolded protein response (UPR) during reperfusion with a new drug candidate we discovered in collaboration with scientists at The Scripps Research Institute, code named 147, transcriptionally reprogrammed proteostasis, ameliorated damage and preserved heart function in mice.
One of the projects in the Glembotski lab involves identifying proteins secreted by the heart, determining what their functions are in myocardial function, as well as regenerating damaged heart tissue, and elucidating the mechanisms of their secretion.
Over the last decade, it has become clear that the accumulation of misfolded proteins contributes to a number of neurodegenerative, immune and endocrine pathologies, as well as other age-related illnesses. Recent interest has focused on the possibility that the accumulation of misfolded proteins can also contribute to cardiovascular disease. In large part, the misfolding of proteins takes place during synthesis on free ribosomes in the cytoplasm, or on endoplasmic reticulum (ER) ribosomes.
Proteins secreted by the heart are called cardiokines. After secretion, cardiokines, such as cytokines, growth promoters and stem cell homing factors, can reduce ischemic damage, as well as enhancing stem cell survival and engraftment. But ischemia impairs protein folding and secretion, and negatively impacts stem cell-mediated regeneration. However, we discovered a secretion process that resists this inhibition, enabling the release of certain beneficial cardiokines, just when they are needed the most. Studies in the Glembotski lab focus on examining the functions of, and molecular mechanisms governing this secretion process in cardiac myocytes and in cardiac stem cells. Our studies of cardiokine secretion in the ischemic heart, and secretion by cardiac stem cells will facilitate the design of therapeutic strategies aimed at enhancing the secretion of beneficial cardiokines that minimize damage and maximize regeneration.
One of the main goals of research in the Glembotski lab is to develop prototypes of therapies that could be used as platforms for the development of novel treatments for heart disease. One such prototype involves the selective delivery of cardioprotective genes to the heart using an adenovirus-associated (AAV) gene therapy approach. In our studies of secretion, ER stress and stem cells in the heart, we have completed microarray analyses to identify mRNAs and microRNAs that are regulated in response to protective stress signaling pathways. As a result of those arrays, we have identified candidate genes that have been selected for development of prototypes for gene therapy. We have packaged the candidate genes into AAV9, a form of AAV that preferentially delivers genes to the heart. Moreover, we have engineered these genes so that their expression is regulated by cardiac-specific promoters, which further enhancing their utility and therapeutic safety. We have already shown the cardioprotective effects of several candidate genes using the AAV9 gene therapy approach, thus demonstrating the therapeutic potential of this platform for treating heart disease.
In efforts to develop novel therapies of treating heart disease, research in the Glembotski lab is focused on how to deliver cardioprotective agents to the heart without leaving a genetic footprint. One method to accomplish this is to deliver protective proteins directly to the heart using state-of-the-art protein formulation and transduction methods. One such method involves combining Tat- and Arg-9-mediated methods of protein transduction, with we identified as cardioprotective. To accomplish this, members of the lab have patented technologies for the generation of chimeric proteins so that the transduction domains are removed from the bioactive region of the proteins within cells of the heart. This approach has been used to develop a new therapeutic platform that can be applied in the future to the delivery of essentially any protective protein to any tissue of interest. Members of the Glembotski lab are encouraged to design novel therapeutic platforms, such as this, in order to optimize the application of our basic science research efforts to a therapeutic setting.