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Protein quality control has been shown to protect the heart from acute stresses such as ischemia and reperfusion (I/R). This dissertation explores two mechanisms by which protein quality control protects the heart from I/R- induced damage. The first study characterizes protein disulfide isomerase-associated 6 (PDIA6) as an endoplasmic reticulum (ER) stress response gene and its ability to protect cultured cardiac myocytes from I/R damage. The second study elucidates the role of alpha-B crystallin ([alpha]BC) in protecting the myocardium from I/R injury using a novel knock-out (KO) mouse model. I/R can impair ER protein folding and initiate the ER stress response. ER stress and I/R activate the transcription factor, activating transcription factor 6 (ATF6), which induces numerous genes, many of which have not been examined in the heart. In this study, we presented that, ATF6 induced the PDIA6 gene, which encodes an ER enzyme that catalyzes protein disulfide bond formation. Gain- and loss-of- function studies showed that PDIA6 protected cardiac myocytes against simulated I/R-induced death in a manner that was dependent on the catalytic activity of PDIA6. Thus, by facilitating disulfide bond formation, and enhancing ER protein folding, PDIA6 may contribute to the protective effects of ATF6 in the ischemic heart. Overexpression studies have shown that the small heat shock proteins (sHSP) can protect from I/R damage. Previous studies have shown that hearts harboring the deletion of both [alpha]BC and HSPB2, both sHSP family members, were more susceptible to I/R damage. In this study, we generated and characterized a mouse line in which only [alpha]BC was deleted [alpha]BC KO), in order to clarify the roles of [alpha]BC and HSPB2 in cardioprotection. Cardiac morphology and function of the [alpha]BC KO mice were indistinguishable from age-matched wild-type (WT) mice, although a few markers of cardiac pathology were elevated, suggesting an underlying phenotype. The function of isolated perfused hearts from [alpha]BC KO mice were initially indistinguishable from those from WT mice, however, after I/R, [alpha]BC KO mouse hearts exhibited a 50% reduced functional recovery when compared to WT mouse hearts. Thus, [alpha]BC is required for maximal functional recovery from I/R-induced injury

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REST (RE1 silencing transcription factor), also known as NRSF (neuron-restrictive silencer factor), is a well-known transcriptional repressor of neural genes in non-neural tissues and stem cells. Dysregulation of REST activity is thought to play a role in diverse diseases including epilepsy, cancer, Down's syndrome and Huntington's disease. The role of REST/NRSF in control of human embryonic stem cell (hESC) fate has never been examined. To evaluate the role of REST in hESCs we developed an inducible REST knockdown system and examined both growth and differentiation over short and long term culture. Interestingly, we have found that altering REST levels in multiple hESC lines does not result in loss of self-renewal but instead leads to increased survival. During differentiation, REST knockdown resulted in increased MAPK/ERK and WNT signaling and increased expression of mesendoderm differentiation markers. Therefore we have uncovered a new role for REST in regulation of growth and early differentiation decisions in human embryonic stem cells.

Adipose tissue is the site of long-term energy storage. During the fasting state, exercise, and cold exposure, the white adipose tissue mobilizes energy for peripheral tissues through lipolysis. The mobilization of lipids from white adipose tissue to the liver can lead to excess triglyceride accumulation and fatty liver disease. Although the white adipose tissue is known to release free fatty acids, a comprehensive analysis of lipids mobilized from white adipocytes in vivo has not been completed. In these studies, we provide a comprehensive quantitative analysis of the adipocyte-secreted lipidome and show that there is interorgan crosstalk with liver. Our analysis identifies multiple lipid classes released by adipocytes in response to activation of lipolysis. Time-dependent analysis of the serum lipidome showed that free fatty acids increase within 30 min of β3-adrenergic receptor activation and subsequently decrease, followed by a rise in serum triglycerides, liver triglycerides, and several ceramide species. The triglyceride composition of liver is enriched for linoleic acid despite higher concentrations of palmitate in the blood. To further validate that these findings were a specific consequence of lipolysis, we generated mice with conditional deletion of adipose tissue triglyceride lipase exclusively in adipocytes. This loss of in vivo adipocyte lipolysis prevented the rise in serum free fatty acids and hepatic triglycerides. Furthermore, conditioned media from adipocytes promotes lipid remodeling in hepatocytes with concomitant changes in genes/pathways mediating lipid utilization. Together, these data highlight critical role of adipocyte lipolysis in interorgan crosstalk between adipocytes and liver.