PROJECT SUMMARYIncreases in protein synthesis during pathological cardiac hypertrophy places demands on protein-foldingmachinery to avert the accumulation of toxic misfolded proteins. Associated with the endoplasmic reticulum(ER) where many important proteins are synthesized in cardiac myocytes is a system that recognizes anddegrades misfolded proteins i.e. ER associated (protein) degradation or ERAD. We discovered a differentnon-canonical role for ERAD as a regulator of the levels of the growth-promoting kinase serum glucocorticoidkinase 1 (SGK1). SGK1 is a cytosolic kinase involved in growth of other cell types such as cancer cells.Interestingly SGK1 can traffic to the ER where it is ubiquitylated by ERAD machinery and subsequentlydegraded by cytosolic proteasomes; however this unique regulatory mechanism has not been studied in theheart. Our preliminary evidence shows that non-canonical ERAD could regulate SGK1 levels in the heart andthereby regulating cardiac growth under pathological conditions. We also found that an SGK1-binding proteincalled glucocorticoid-inducible leucine zipper protein (GILZ) can bind to and protect SGK1 from non-canonicalERAD-mediated degradation which we believe increases SGK1-mediated growth of the heart during pressureoverload. Accordingly our hypothesis is that SGK1 is a major inducer of pressure overload-induced cardiacpathology. During pressure overload SGK1 levels and thus SGK1-mediated cardiac hypertrophy andsubsequent pathology are increased by GILZ-dependent diversion of SGK1 away from the ER which decreasesSGK1 degradation by non-canonical ERAD. Ectopic expression of an SGK1 peptide disrupts the GILZ-SGK1interaction increases SGK1 degradation thus decreasing SGK1-mediated cardiac hypertrophy and subsequentpathology. This hypothesis will be examined in mice subjected to pressure overload-induced cardiac pathologyin our specific aims which are to 1-couple cardiac-specific SGK1 deletion with AAV9 encoding SGK1-WT(active; ER-targeted) SGK1-KD (kinase-dead ER-targeted) or SGK1-60 (active; not ER-targeted) to examinethe effect of SGK1 and ERAD on overload-induced cardiac pathology 2-combine AAV9-SGK1-WT or AAV9-SGK1-60 with AAV9-mediated GILZ overexpression or knockdown to determine whether GILZ diverts SGK1-WT from the ER and protects it from ERAD in the heart 3-evaluate the potential therapeutic antihypertrophiceffects of a novel SGK1 peptide that interrupts GILZ-SGK1 binding and increases non-canonical ERAD-mediated SGK1 degradation. These studies are significant because they will reveal previously unappreciatedroles for SGK1 GILZ and ERAD in pathologic cardiac hypertrophy. We will use an innovative molecular strategyto mechanistically dissect roles for GILZ and non-canonical ERAD as regulators of SGK1 signaling and cardiacpathology. Peptide-based disruption of the SGK1-GILZ interaction could be a highly specific method for inhibitingthe maladaptive pathological effects of SGK1 in the heart by selective degradation of SGK1.