Date of Graduation
12-2014
Document Type
Thesis (MS)
Program Affiliation
Biomedical Sciences
Degree Name
Masters of Science (MS)
Advisor/Committee Chair
Oleh Pochynyuk
Committee Member
Roger.G.O’Neil
Committee Member
Kartik Venkatachalam
Committee Member
Richard.B.Clark
Committee Member
Peter. A. Doris
Abstract
The Ca2+-permeable TRPV4 channel is predominantly expressed in the distal nephron (DN) and its activity is essential for [Ca2+]i elevations in response to increased tubular flow. Here, I probed the physiological mechanisms controlling TRPV4 function and expression in the DN. I found that renal TRPV4 expression and mRNA levels were significantly increased by high K+ diet (5%) and decreased by dietary K+ restriction (0.003%). In contrast, variations in Na+ regimen had no apparent effect on TRPV4 expression and mRNA levels. Regulation of TRPV4 protein expression by K+ diet was independent of aldosterone action, since saturation of systemic mineralocorticoid signaling with DOCA, a precursor of aldosterone, had little effect on TRPV4 protein abundance in the kidney. Confocal immunofluorescence in split-opened DNs showed that high K+ and Na+ intake resulted in redistribution of the channel towards the apical plasma membrane of DN cells, while K+ and Na+ restrictions caused cytosolic distribution of TRPV4. Augmented TRPV4 expression and localization to the apical plasma membrane during high K+ and Na+ intake were associated with significantly augmented flow-induced [Ca2+]i responses in DN cells. In summary, my findings demonstrate that high K+ and Na+ intake regulate TRPV4 status to properly respond to elevated tubular flow during these physiological stimuli. I also propose that impaired regulation of TRPV4 in the DN during variations in dietary intake may result in systemic defects in K+ and Na+ balance contributing to cardiovascular abnormalities.
Keywords
TRPV4, mechanosensitivity, calcium, tubular flow, distal nephron, potassium diet, sodium diet, ion channels