The entry of sodium across the lumen-facing membranes of renal and airway epithelia is a highly regulated process, mediated by the epithelial sodium channel (ENaC). Abnormalities in ENaC function are implicated in significant human diseases, including hypertension, nephrosis, cystic fibrosis and pulmonary edema. In renal and airway epithelia, ENaC activity is regulated by factors that control the number of active channels residing in the apical membranes. Apical channel number is determined by membrane trafficking events in response to key hormonal regulators of the extracellular fluid volume and blood pressure. This proposal addresses the phosphorylation-dependent regulation of ENaC trafficking in renal epithelia. Nearly all research in this field has focused on the mechanisms that govern ENaC retrieval from the apical membrane;by contrast, our knowledge of the mechanisms that regulate the forward trafficking of ENaC to the apical cell surface is weak. During the prior funding period, we found that 14-3-3 proteins are essential stabilizers of the phospho-proteins that regulate ENaC trafficking, and we developed 14-3-3 affinity capture as a tool to identify proteins lying at important regulatory nodes in the forward trafficking of ENaC. Therefore, the proposed work will examine the mechanisms of action of three new regulators and assess their physiological significance. To begin, we will define the mechanism of action of the Rab-GAP, AS160, 14-3-3 binding protein and phosphorylation-dependent regulator of aldosterone- and insulin-mediated ENaC trafficking. A related protein, TBC1D1, is a candidate regulator of apical ENaC trafficking in response to vasopressin stimulation, and interactions between these pathways may account for synergism in the actions of these agonists. This approach has also identified the actin reorganizing, 14-3-3 binding protein, cofilin, as a candidate to control regulated apical ENaC insertion. Our work is expected to reveal new mechanisms for the control of apical ENaC density, and identify novel targets for the therapeutic targeting of abnormal salt and water balance in sodium transporting epithelia.
This proposal aims to identify the key regulators of epithelial sodium channel (ENaC) density at the apical membranes of renal epithelial cells. The trafficking of ENaC to the apical surface is the principal mode of channel regulation for hormones that sense extracellular fluid volume and blood pressure. These pathways are implicated in significant human diseases, including hypertension. Using 14-3-3 affinity methods, we have identified several new regulators of forward ENaC trafficking to the apical membranes, and we will define the mechanisms by which they control significant steps along the apical ENaC trafficking pathway in response to agonists. This work is expected to reveal new regulators and therapeutic targets for the control of sodium and fluid transport in the kidney.
|Holleran, John P; Zeng, Jianxin; Frizzell, Raymond A et al. (2013) Regulated recycling of mutant CFTR is partially restored by pharmacological treatment. J Cell Sci 126:2692-703|
|Frizzell, Raymond A; Hanrahan, John W (2012) Physiology of epithelial chloride and fluid secretion. Cold Spring Harb Perspect Med 2:a009563|
|Liang, Xiubin; Da Paula, Ana Carina; Bozóky, Zoltán et al. (2012) Phosphorylation-dependent 14-3-3 protein interactions regulate CFTR biogenesis. Mol Biol Cell 23:996-1009|
|Butterworth, Michael B; Edinger, Robert S; Silvis, Mark R et al. (2012) Rab11b regulates the trafficking and recycling of the epithelial sodium channel (ENaC). Am J Physiol Renal Physiol 302:F581-90|
|Edinger, Robert S; Bertrand, Carol A; Rondandino, Christine et al. (2012) The epithelial sodium channel (ENaC) establishes a trafficking vesicle pool responsible for its regulation. PLoS One 7:e46593|
|Butterworth, Michael B (2010) Regulation of the epithelial sodium channel (ENaC) by membrane trafficking. Biochim Biophys Acta 1802:1166-77|
|Liang, Xiubin; Butterworth, Michael B; Peters, Kathryn W et al. (2010) AS160 modulates aldosterone-stimulated epithelial sodium channel forward trafficking. Mol Biol Cell 21:2024-33|
|Butterworth, Michael B; Edinger, Robert S; Frizzell, Raymond A et al. (2009) Regulation of the epithelial sodium channel by membrane trafficking. Am J Physiol Renal Physiol 296:F10-24|
|Myerburg, Mike M; McKenna, Erin E; Luke, Cliff J et al. (2008) Prostasin expression is regulated by airway surface liquid volume and is increased in cystic fibrosis. Am J Physiol Lung Cell Mol Physiol 294:L932-41|
|Liang, Xiubin; Butterworth, Michael B; Peters, Kathryn W et al. (2008) An obligatory heterodimer of 14-3-3beta and 14-3-3epsilon is required for aldosterone regulation of the epithelial sodium channel. J Biol Chem 283:27418-25|
Showing the most recent 10 out of 22 publications