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Lipid raft abnormalities and subsequent protein trafficking effects in Niemann‐Pick type C1 (LB158)
Author(s) -
Kuech EvaMaria,
Shammas Hadeel,
Maalouf Katia E.,
KoeckritzBlickwede Maren,
Das Anibh M.,
Naim Hassan Y.
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.lb158
Subject(s) - npc1 , endocytosis , lipid raft , sphingolipid , lipid microdomain , chemistry , cholesterol , ganglioside , microbiology and biotechnology , biochemistry , biology , cell , membrane , endosome
Many proteins and lipid components are organized within membrane microdomains, known as lipid rafts (LR). LR are cholesterol‐ and sphingolipid‐rich membranes resistant to non‐ionic detergents. In Niemann‐Pick type C1 (NPC1), a neurovisceral lysosomal storage disease, entrapment of cholesterol and sphingolipids occurs and may lead to alterations in LR composition. We investigate the LR status in fibroblasts derived from a patient with NPC1 and analyze the trafficking profiles of a typical LR‐associated membrane protein, dipeptidylpeptidase IV (DPPIV). Sucrose density gradients of Triton X‐100 cellular lysates revealed a substantial shift of the LR‐marker flotillin2 in NPC fibroblasts from the floating LR fractions to the detergent‐soluble membranes. Notably, the cell surface expression of DPPIV increased significantly by 2‐fold in NPC1 cells, while the overall protein level of DPPIV remained constant. FACS analysis corroborated the increase of DPPIV at the cell surface. This accumulation is the result of delayed lipid rafts‐dependent endocytosis in NPC1 cells as assessed by (i) a significant reduction in the level of internalized biotin‐labeled DPPIV and (ii) imaging studies revealing a reduced localization of DPPIV with EEA‐1 in NPC1 cells. Strikingly, N‐butyl‐deoxynojirimycin (NB‐DNJ), an inhibitor of glucosylceramide synthase, restored significantly LR levels and endocytosis of DPPIV. We conclude that altered composition or reduced levels of LR constitute a potential mechanism in the pathogenesis of NPC1 and NB‐DNJ treatment restores a balanced membrane lipid composition and the associated biochemical anomalies.