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Journal of Lipid Research, Vol. 50, 1101-1108, June 2009
Copyright © 2009 by American Society for Biochemistry and Molecular Biology

Defective CFTR increases synthesis and mass of sphingolipids that modulate membrane composition and lipid signaling

Hiroko Hamai^*, Fannie Keyserman^*, Lynne M. Quittell and Tilla S. Worgall^1,*,,

^* Department of Pathology, New York, NY 10032
Department of Pediatrics, New York, NY 10032
Institute of Human Nutrition, Columbia University, New York, NY 10032

Published, JLR Papers in Press, January 14, 2009.

¹ To whom correspondence should be addressed. e-mail: tpw7{at}columbia.edu

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) that affect protein structure and channel function. CFTR, localized in the apical membrane within cholesterol and sphingomyelin rich regions, is an ABC transporter that functions as a chloride channel. Here, we report that expression of defective CFTR (F508CFTR or decreased CFTR) in human lung epithelial cell lines increases sphingolipid synthesis and mass of sphinganine, sphingosine, four long-chain saturated ceramide species, C16 dihydroceramide, C22, C24, C26-ceramide, and sphingomyelin, and decreases mass of C18 and unsaturated C18:1 ceramide species. Decreased expression of CFTR is associated with increased expression of long-chain base subunit 1 of serine-palmitoyl CoA, the rate-limiting enzyme of de novo sphingolipid synthesis and increased sphingolipid synthesis. Overexpression of F508CFTR in bronchoalveolar cells that do not express CFTR increases sphingolipid synthesis and mass, whereas overexpression of wild-type CFTR, but not of an unrelated ABC transporter, ABCA7, decreases sphingolipid synthesis and mass. The data are consistent with a model in which CFTR functions within a feedback system that affects sphingolipid synthesis and in which increased sphingolipid synthesis could reflect a physiological response to sequestration of sphingolipids or altered membrane structure.

Supplementary key words cystic fibrosis transmembrane conductance regulator • sphingomyelin • sphingosine • sphinganine • serine-palmitoyl transferase • long-chain base subunit 1

Abbreviations: CF, cystic fibrosis; CFTR, cystic fibrosis transmembrane conductance regulator; LCB1, long-chain base subunit 1; SPT, serine-palmitoyl transferase

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