We have determined that (i) pH-dependent cleavage of the glycosyl phosphatidylinositol (GPI) anchored protein GP2 from the ectoleaflet of the apical plasma membrane of rat pancreatic acinar cells plays a critical role in the activation of endocytosis; II this endocytic process is mediated through activation of tyrosine kinases; and (iii) GP2 appears to activate this process through the formation of a complex with the src kinases pp60 and p62yes as well as caveolin. These data indicate that ductal bicarbonate secretion, through alkalinization of the acinar lumen, regulates apical endocytosis in acinar cells through the pH-dependent cleavage of GP2. In support of this hypothesis we have shown in Cystic Fibrosis (CF) knockout mice that the absence of bicarbonate and hence the lack of alkalinization of the acinar lumen leads to a selective impairment in GP2 release as well as apical endocytosis. We have also discovered that CF knockout mice have a specific fatty acid imbalance characterized by an increase in phospholipid-bound arachidonic acid (AA) and a decrease in phospholipid-bound docosahexaenoic acid (DHA). This was present only in CFTR regulated tissues. Correction of this fatty acid imbalance by oral administration of DHA to CF mice resulted in reversal of the pathology in the pancreas, ileum, and in pseudomonas endotoxin-induced lung inflammation. In addition, we have recently shown that humans with CF have a similar abnormality in AA and OHA. The underlying hypothesis for this proposal is that the imbalance in AA and DHA may (i) lead to the excessive inflammatory response characteristic of CF and (ii) play a role in apical membrane events in the exocrine pancreas. This proposal will build upon these observations and (i) determine the mechanism by which defects in CFTR lead to abnormalities in AA and DHA; (ii) determine the role of fatty acids in membrane events at the apical surface of acinar cells; and (iii) determine the mechanism by which DHA regulates inflammation. Results from this project will be important in understanding the pathophysiology of CF and the development of potential therapies for diseases related to CF gene mutations.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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General Medicine A Subcommittee 2 (GMA)
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Serrano, Jose
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Beth Israel Deaconess Medical Center
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Zaman, Munir M; Martin, Camilia R; Andersson, Charlotte et al. (2010) Linoleic acid supplementation results in increased arachidonic acid and eicosanoid production in CF airway cells and in cftr-/- transgenic mice. Am J Physiol Lung Cell Mol Physiol 299:L599-606
Al-Turkmani, M Rabie; Andersson, Charlotte; Alturkmani, Ragheed et al. (2008) A mechanism accounting for the low cellular level of linoleic acid in cystic fibrosis and its reversal by DHA. J Lipid Res 49:1946-54
Andersson, Charlotte; Al-Turkmani, M Rabie; Savaille, Juanito E et al. (2008) Cell culture models demonstrate that CFTR dysfunction leads to defective fatty acid composition and metabolism. J Lipid Res 49:1692-700
Beharry, Satti; Ackerley, Cameron; Corey, Mary et al. (2007) Long-term docosahexaenoic acid therapy in a congenic murine model of cystic fibrosis. Am J Physiol Gastrointest Liver Physiol 292:G839-48
Pall, Harpreet; Zaman, Munir M; Andersson, Charlotte et al. (2006) Decreased peroxisome proliferator activated receptor alpha is associated with bile duct injury in cystic fibrosis transmembrane conductance regulator-/- mice. J Pediatr Gastroenterol Nutr 42:275-81
Ollero, Mario; Laposata, Michael; Zaman, Munir M et al. (2006) Evidence of increased flux to n-6 docosapentaenoic acid in phospholipids of pancreas from cftr-/- knockout mice. Metabolism 55:1192-200
Blanco, Paola G; Salem, Raneem O; Ollero, Mario et al. (2005) Ethanol administration to cystic fibrosis knockout mice results in increased fatty acid ethyl ester production. Alcohol Clin Exp Res 29:2039-45
Blanco, Paola G; Zaman, Munir M; Junaidi, Omer et al. (2004) Induction of colitis in cftr-/- mice results in bile duct injury. Am J Physiol Gastrointest Liver Physiol 287:G491-6
Ollero, Mario; Junaidi, Omer; Zaman, Munir M et al. (2004) Decreased expression of peroxisome proliferator activated receptor gamma in cftr-/- mice. J Cell Physiol 200:235-44
Freedman, S D; Kern, H F; Scheele, G A (2001) Pancreatic acinar cell dysfunction in CFTR(-/-) mice is associated with impairments in luminal pH and endocytosis. Gastroenterology 121:950-7

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