The epithelial Na+ channel (ENaC) is a distal target of the renin- angiotensin-aldosterone pathway, where it is critically positioned to play an important role in blood pressure control. Gain-of-function mutations in ENaC cause Liddle's syndrome, an inherited form of hypertension. Conversely, loss-of-function mutations cause a genetic disorder of salt wasting and hypotension (pseudohypoaldosteronism type 1). Thus, an understanding of the function and regulation of this channel will provide important insights into human blood pressure variations and the pathogenesis of hypertension. In this project, we are responsive to Goal 2 of the RFA; """"""""mechanistic studies on the consequence of genetic variation."""""""" In preliminary studies, we found that the interaction of ENaC with Nedd4, a ubiquitin protein-ligase, plays an important role in controlling Na+ absorption. Several findings suggest that a ubiquitin protein-ligase plays an important role in controlling Na+ absorption Several findings suggest that Nedd4 might play a critical role in the control of blood pressure. First, in preliminary studies we found that Nedd4 decreases ENaC Na+ current by targeting the channel for degradation. First, in preliminary studies we found that Nedd4 decreases ENaC Na+ current by targeting the channel for degradation. Second, the sequences in ENaC that bind to Ndd4 (PY motifs) are deleted or mutated in Liddle's syndromes. Third, we found that Liddle's syndrome mutations in the betaENaC subunit prevention Nedd4 from inhibiting the channel. Thus, the overall goal of this proposal is to understand the molecular mechanisms by which Nedd4 from inhibiting the channel. Thus, the overall goal of this proposal is to understand the molecular mechanisms by which Nedd4 inhibits ENaC, and to begin to define the role of this pathway in Liddle's syndrome and more common forms of hypertension. Thus, the overall goal of this proposal is to understand the molecular mechanisms by which Nedd4 inhibits ENaC, and to begin to define the role of this pathway in Liddle's syndrome and more common forms of hypertension. In the first two specific aims, we will investigate the molecular determinants for the inhibition of ENaC by Nedd4.
Specific Aim 1 will focus on the role of a C2 domain in Nedd4 in the Ca2+- dependent inhibition of ENaC, and on the physical interaction between WW domains in Nedd4 and the PY motifs of ENaC.
Specific Aim 2 will complement Aim 1, determining the sequences in ENaC that are involved in the interaction and inhibition by Nedd4. Specifically, we will examine the role of the PY motifs that are targeted in Liddle's syndrome, and test the hypothesis that ubiquitination of ENaC is required for Nedd4- mediated inhibition.
In Specific Aim 3, we will examine the functional consequences of natural genetic variation in ENaC found in hypertensive populations. This may provide important new insight into the role of ENaC and Nedd4 in human blood pressure variation and the pathogenesis of hypertension.
Showing the most recent 10 out of 183 publications
