Islet amyloid formation is a pathological hallmark of type 2 diabetes and is observed in >90% of patients with the disease. These amyloid deposits are associated with -cell apoptosis resulting in -cell mass loss. In the autoimmune disease process of type 1 diabetes, cytokines are responsible for the induction of -cell apoptosis. Studies of the mechanisms of -cell loss have identified the involvement of a number of pro- apoptotic molecules. However, the role of apoptosis repressor with a caspase recruitment domain (ARC), a novel anti-apoptotic protein recently identified in the cell, remains largely unknown. To gai greater insight into the mechanisms of -cell apoptosis, we will determine how ARC interacts with other proteins in the cell to limit apoptosis. These interactions include (a) synergizing wth the anti-apoptotic protein 14-3-3?, (b) inhibiting signaling by the pro-apoptotic protein JNK, an (c) inhibiing signaling pathway molecules activated by TNF-?-, IL-1, and IFN-?. In this application we propose four specific aims to examine the mechanisms by which ARC decreases - cell apoptosis.
Specific Aims 1 -3 will utilize in vitro approaches. The first two aims primaril address islet amyloid-induced mechanisms, while the third focuses on those induced by cytokines.
Specific Aim 4 will be done in vivo to examine the translational relevance of increasing ARC in the cell.
Specific Aim 1 : To determine if ARC's inhibition of JNK and/or p53 is sufficient to prevent amyloid-induced - cell apoptosis.
Specific Aim 2 : To determine the role of 14-3-3? in mediating the effect of ARC to reduce amyloid-induced - cell apoptosis.
Specific Aim 3 : To determine whether ARC prevents cytokine-induced -cell apoptosis and the mechanism(s) by which it does so.
Specific Aim 4 : To determine in vivo whether increasing ARC expression in cells can safely reduce amyloid- induced -cell loss. For the in vitro studies (Specific Aims 1-3) we will use islets from our transgenic mouse model of islet amyloid, wild type mice and humans as well as an immortalized -cell line. For the in vivo work examining the effects of ARC in cells (Specific Aim 4), we will produce a new transgenic mouse model expressing both human islet amyloid polypeptide (hIAPP) and ARC in its cells. The long-term goal of this work is to define additional targets to prevent or curtail -cell loss, an important component of the diabetes disease process.
The number of individuals affected by diabetes continues to increase, with the disease disproportionately affecting Veterans. The islet cell represents a key component in the disease process, manifest as reduced insulin secretion and the loss of insulin producing cells. There are a number of causes for the loss of cells, including islet amyloid and cytokines The formation of amyloid deposits and the action of cytokines are associated with cellular stress that activates pathways leading to the death of the cell. We propose to examine proteins in the islet cell that act on molecules in these pathways and thus could prevent -cell death. By gaining a greater understanding of the role of proteins linked to the death and survival of the cell, our goal is ultimately to develop new approaches to treat patients with diabetes in order to preserve their cells.
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