CFTR knockdown stimulates lipid synthesis and transport in intestinal Caco-2/15 cells.
Cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel highly expressed in epithelial cells of the gastrointestinal tract. Mutations in the CFTR gene cause cystic fibrosis (CF), a disease characterized by pancreatic insufficiency, fat malabsorption, and steatorrhea. Despite the administration of pancreatic enzymes to normalize malabsorption, CF patients still experienced lipid fecal loss, nutritional deficiencies, and abnormalities in serum lipid profile, suggesting the presence of intrinsic defects in the intestinal handling of nutrients. The objective of the present study was to assess the impact of CFTR gene knockdown on intracellular lipid metabolism of the intestinal Caco-2/15 cell line. Partial CFTR gene inactivation led to cellular lipid accretion of phospholipids, triglycerides, and cholesteryl esters. Likewise, secretion of these lipid fractions was significantly increased following CFTR gene manipulation. As expected from these findings, the output of triglyceride-rich lipoproteins showed the same increasing pattern. Investigation of the mechanisms underlying these changes revealed that CFTR knockdown resulted in raised levels of apolipoproteins in cells and media and microsomal transfer protein activity, two important factors for the efficient assembly and secretion of lipoproteins. Similarly, scrutiny of the enzymatic monoacylglycerol acyltransferase and diacylglycerol acyltransferase, which exhibit dynamic function in triacylglycerol resynthesis and chylomicron formation in enterocytes, revealed a significant augmentation in their activity. Conversely, cholesterol uptake mediated by Niemann-Pick C1 like 1, Scavenger Receptor Class B Type I, and ATP-binding cassette G8 remains unaffected by genetic modification of CFTR. Collectively, these results highlight the role played by CFTR in intestinal handling of lipids and may suggest that factors other than defective CFTR are responsible for the abnormal intracellular events leading to fat malabsorption in CF patients.
Mailhot
Geneviève
G
Research Centre, CHU Sainte-Justine, Université de Montréal, Québec, Canada.
Ravid
Zaava
Z
Barchi
Soraya
S
Moreau
Alain
A
Rabasa-Lhoret
Rémi
R
Levy
Emile
E
D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000217:Acyltransferases / Q000378:metabolism; D001053:Apolipoproteins / Q000096:biosynthesis / Q000378:metabolism; D001692:Biological Transport; D018955:CD36 Antigens / Q000378:metabolism; D018938:Caco-2 Cells; D002352:Carrier Proteins / Q000378:metabolism; D002788:Cholesterol Esters / Q000096:biosynthesis / Q000378:metabolism; D003550:Cystic Fibrosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000172:deficiency* / Q000235:genetics; D051048:Diacylglycerol O-Acyltransferase / Q000378:metabolism; D015536:Down-Regulation; D020895:Enterocytes / Q000378:metabolism* / Q000473:pathology; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D006801:Humans; D007408:Intestinal Absorption / Q000235:genetics; D007419:Intestinal Secretions; D050155:Lipogenesis / Q000235:genetics; D008074:Lipoproteins / Q000096:biosynthesis / Q000378:metabolism; D055627:Natural Cytotoxicity Triggering Receptor 1 / Q000378:metabolism; D010743:Phospholipids / Q000096:biosynthesis / Q000378:metabolism; D014280:Triglycerides / Q000096:biosynthesis / Q000378:metabolism
C416946:ABCG8 protein, human; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters; D001053:Apolipoproteins; D018955:CD36 Antigens; C505032:CFTR protein, human; D002352:Carrier Proteins; D002788:Cholesterol Esters; D008074:Lipoproteins; C112260:NCR1 protein, human; D055627:Natural Cytotoxicity Triggering Receptor 1; D010743:Phospholipids; D014280:Triglycerides; C106092:microsomal triglyceride transfer protein; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000217:Acyltransferases; D051048:Diacylglycerol O-Acyltransferase; C021802:2-acylglycerol O-acyltransferase