2000 — 2009 |
Brewer, Joseph W |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Homeostasis of the Er in Differentiating B Cells @ Loyola University Chicago
DESCRIPTION (provided by applicant): The long-term goal of this research program is to delineate the molecular mechanisms that regulate homeostasis of the endoplasmic reticulum (ER) in B-lymphocytes. The ER is a specialized compartment for the maturation of membrane and secreted proteins. As such, the ER is the site where immunoglobulin chains fold and assemble into functional antibodies. When B-lymphocytes differentiate into antibody-secreting plasma cells, the ER expands and adapts to accommodate high-rate antibody production. Therefore, the mechanisms that regulate ER homeostasis in differentiating B cells are critical for antibody-mediated immunity. An intracellular signaling pathway, termed the unfolded protein response (UPR), monitors the status of protein folding in the ER and transmits that information to mechanisms that modulate the ER environment. A key UPR transcriptional activator, XBP1(S), is required for plasma cell development. ER expansion includes increased expression of many ER resident proteins and elevated synthesis of phospholipids necessary for membrane biosynthesis. Both of these events have been linked to XBP1(S). This project focuses on four specific aims. First, the protein and lipid composition of the ER will be characterized in differentiating B cells and in a fibroblast model in which ER expansion is induced by enforced expression of XBP1(S). Second, the ability of the expanded ER to support protein biosynthesis will be evaluated in these systems. Third, the mechanism by which phospholipid biosynthesis increases during ER expansion will be investigated. Finally, factors that regulate ER biogenesis will be identified using biochemical and genetic approaches. These studies will yield new information concerning UPR-regulated events that control plasma cell development, generate efficient antibody responses, and mediate ER homeostasis. Importantly, the UPR has been linked to a number of physiologically significant processes including pancreatic function, skeletal development, oxidative stress, and macrophage apoptosis in atherosclerotic lesions. In addition, a number of catastrophic disorders including lysosomal storage diseases, cystic fibrosis, and Alzheimer disease have been linked to protein maturation errors in the ER. A mechanistic understanding of ER homeostasis might lead to the development of novel therapeutics for these diseases.
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1 |
2010 — 2011 |
Brewer, Joseph W |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Homeostasis of the Er in Differentiating B-Cells @ University of South Alabama
DESCRIPTION (provided by applicant): The long-term goal of this research program is to delineate mechanisms that regulate homeostasis of the endoplasmic reticulum (ER) in B-lymphocytes and to understand how these same mechanisms influence the fate of activated B-cells. A link exists between the supply of phosphatidylcholine (PtdCho), the most abundant phospholipid in cellular membranes, and unfolded protein response (UPR) signaling pathway. XBP1(S), a transcription factor generated by the UPR, is required for normal antibody production, maximal increases in total PtdCho and ER expansion in stimulated B-cells. Another UPR transcription factor, ATF61, also has the ability to induce PtdCho synthesis and ER expansion. Deletion of CCT1, the rate-limiting enzyme in PtdCho synthesis, markedly diminishes PtdCho production in activated B-cells. This correlates with accelerated induction of XBP1(S) and IgM secretion, but little production of other antibody isotypes. Therefore, we hypothesize that PtdCho supply can influence the fate of activated B-cells by interfacing with the UPR to promote PtdCho synthesis and drive differentiation of antibody-secreting B-cells. The project will focus on four specific aims and utilize gene knockout mouse models, cell culture systems and a combination of molecular, biochemical and cellular techniques. In aim 1, experiments will address the mechanism by which XBP1(S) up-regulates PtdCho supply in activated B-cells. In aim 2, studies will assess the contributions of ATF61 to the regulation of PtdCho synthesis and ER expansion in activated B-cells. In aim 3, experiments will address how a limited PtdCho supply at distinct stages of the B-cell response affects B-cell function and fate in vivo. In aim 4, the mechanism linking PtdCho supply to UPR activation will be explored. Experiments will assess how reduced levels of PtdCho affect ER function and protein transport in the secretory pathway. Antibody-mediated autoimmune disorders such as lupus and B-cell cancers like multiple myeloma are devastating diseases, underscoring the need to identify novel regulatory mechanisms in B-cells that might provide new targets for drug design. The UPR is also involved in many other physiologically significant processes including tumor progression and proper function of the pancreas and liver. Understanding how the UPR works in normal cellular processes is necessary for rational exploration of drugs to modulate this pathway in disease states. PUBLIC HEALTH RELEVANCE: Normal B-cells in the body help fight infection, but B-cells that malfunction can cause life- threatening diseases like cancer. In this research, processes that control B-cell function are being studied. The results may lead to new treatments for diseases caused by faulty B-cells.
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0.937 |