In cystic fibrosis (CF), mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel are associated with defective cAMP and acid-stimulated duodenal bicarbonate secretion, and defective cAMP and cGMP-activated fluid secretion in the intestine. On the other hand, increased activation of CFTR by cAMP and cGMP agonists elicit massive fluid secretion that result in secretory diarrhea. But the mechanisms responsible for increased or decreased activation of CFTR on the apical plasma membrane under physiological conditions in the intestine are unknown. Protein kinase A and G (PKA, PKG) phosphorylation is accepted as central to CFTR regulation. But this dogma assumes that CFTR is confined to the apical plasma membrane. We hypothesize that under physiological conditions in the intetsine, cell and region specific trafficking regulate the number and function of CFTR channels on the cell surface and contribute to disease pathogenesis. This hypothesis is supported by the following observations: (1) CFTR expression is cell and region-specific in the intestine (2) more than 50% of CFTR is in intracellular organelles in native enterocytes and supports constituitive and regulated trafficking in vivo (3) PKA and PKG regulate CFTR trafficking to the cell surface and fluid secretion in a cell and region specific manner in the intestine (4) in the duodenum, cAMP and luminal acid regulate CFTR trafficking and bicarbonate secretion (5) the endocytosis of CFTR from the apical plasma membrane in the intestine of transgenic mice lacking expression of the actin-binding motor myosin VI (Myo6 (sv/sv))is markedly defective, leads to its accumulation on the cell surface and increased CFTR-activated fluid secretion elicited by the cGMP- agonist Heat Stable Enterotoxin in vivo. Over the next five years, we propose to expand these observations and further elucidate the biological relevance of region and cell-specificity of CFTR trafficking, the role of luminal acid in regulating CFTR trafficking and function in the duodenum and the mechanism by which myosin VI regulates CFTR trafficking. We plan an integrative approach that incorporates state of the art cell biological structural, biochemical, and immunological studies including RNA silencing and in vivo perfusion and electrophysiology. These approaches, in conjunction with in vivo models of rat, and transgenic Myo6 (sv/sv) mouse intestine, polarized secretory and absorptive intestinal cells expressing endogenous CFTR and WT (wild type), DF508 and N287Y mutant CFTR-expressing cells will facilitate a comprehensive investigation to meet the defined goals of this proposal.

Public Health Relevance

In cystic fibrosis (CF), the cystic fibrosis transmembrane conductance regulator CFTR chloride channel fails to reach the plasma membrane of cells and in secretory diarrhea, CFTR function on the membrane of intestinal cells is increased. But the mechanisms that lead to CF or secretory diarrhea are unknown. This proposal seeks to understand the mechanisms that regulate CFTR movement into to the membrane under physiological conditions in the intestine in order to elucidate how dysfunction of CFTR leads to either CF or secretory diarrhea.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK077065-03
Application #
7908803
Study Section
Gastrointestinal Mucosal Pathobiology Study Section (GMPB)
Program Officer
Grey, Michael J
Project Start
2008-04-01
Project End
2013-03-31
Budget Start
2010-04-01
Budget End
2011-03-31
Support Year
3
Fiscal Year
2010
Total Cost
$348,171
Indirect Cost
Name
Yale University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
06520
Engevik, Amy C; Kaji, Izumi; Engevik, Melinda A et al. (2018) Loss of MYO5B Leads to Reductions in Na+ Absorption With Maintenance of CFTR-Dependent Cl- Secretion in Enterocytes. Gastroenterology 155:1883-1897.e10
Kumari, Vandana; Desai, Shruti; Ameen, Nadia A (2017) AP2 ? modulates cystic fibrosis transmembrane conductance regulator function in the human intestine. J Cyst Fibros 16:327-334
Kravtsov, Dmitri V; Ahsan, Md Kaimul; Kumari, Vandana et al. (2016) Identification of intestinal ion transport defects in microvillus inclusion disease. Am J Physiol Gastrointest Liver Physiol 311:G142-55
Hegan, Peter S; Kravtsov, Dmitri V; Caputo, Christina et al. (2015) Restoration of cytoskeletal and membrane tethering defects but not defects in membrane trafficking in the intestinal brush border of mice lacking both myosin Ia and myosin VI. Cytoskeleton (Hoboken) 72:455-76
Kravtsov, Dmitri; Mashukova, Anastasia; Forteza, Radia et al. (2014) Myosin 5b loss of function leads to defects in polarized signaling: implication for microvillus inclusion disease pathogenesis and treatment. Am J Physiol Gastrointest Liver Physiol 307:G992-G1001
Jakab, Robert L; Collaco, Anne M; Ameen, Nadia A (2013) Characterization of CFTR High Expresser cells in the intestine. Am J Physiol Gastrointest Liver Physiol 305:G453-65
Weis, Victoria G; Sousa, Josane F; LaFleur, Bonnie J et al. (2013) Heterogeneity in mouse spasmolytic polypeptide-expressing metaplasia lineages identifies markers of metaplastic progression. Gut 62:1270-9
Collaco, Anne M; Jakab, Robert L; Hoekstra, Nadia E et al. (2013) Regulated traffic of anion transporters in mammalian Brunner's glands: a role for water and fluid transport. Am J Physiol Gastrointest Liver Physiol 305:G258-75
Rogers, AilĂ­n C; Huetter, Lisa; Hoekstra, Nadia et al. (2013) Activation of AMPK inhibits cholera toxin stimulated chloride secretion in human and murine intestine. PLoS One 8:e69050
Collaco, Anne M; Geibel, Peter; Lee, Beth S et al. (2013) Functional vacuolar ATPase (V-ATPase) proton pumps traffic to the enterocyte brush border membrane and require CFTR. Am J Physiol Cell Physiol 305:C981-96

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