title: Alterations in membrane caveolae and BKCa channel activity in skin fibroblasts in Smith-Lemli-Opitz syndrome.
abstract: The Smith-Lemli-Opitz syndrome (SLOS) is an inherited disorder of cholesterol synthesis caused by mutations in DHCR7 which encodes the final enzyme in the cholesterol synthesis pathway. The immediate precursor to cholesterol synthesis, 7-dehydrocholesterol (7-DHC) accumulates in the plasma and cells of SLOS patients which has led to the idea that the accumulation of abnormal sterols and/or reduction in cholesterol underlies the phenotypic abnormalities of SLOS. We tested the hypothesis that 7-DHC accumulates in membrane caveolae where it disturbs caveolar bilayer structure-function. Membrane caveolae from skin fibroblasts obtained from SLOS patients were isolated and found to accumulate 7-DHC. In caveolar-like model membranes containing 7-DHC, subtle, but complex alterations in intermolecular packing, lipid order and membrane width were observed. In addition, the BK(Ca) K(+) channel, which co-migrates with caveolin-1 in a membrane fraction enriched with cholesterol, was impaired in SLOS cells as reflected by reduced single channel conductance and a 50 mV rightward shift in the channel activation voltage. In addition, a marked decrease in BK(Ca) protein but not mRNA expression levels was seen suggesting post-translational alterations. Accompanying these changes was a reduction in caveolin-1 protein and mRNA levels, but membrane caveolar structure was not altered. These results are consistent with the hypothesis that 7-DHC accumulation in the caveolar membrane results in defective caveolar signaling. However, additional cellular alterations beyond mere changes associated with abnormal sterols in the membrane likely contribute to the pathogenesis of SLOS.
authors: Department of Surgery, Cooper University Hospital, Camden, NJ 08103, USA.
authors: Gongyi
authors: G
authors: Ren
authors: Robert F
authors: RF
authors: Jacob
authors: Yuri
authors: Y
authors: Kaulin
authors: Paul
authors: P
authors: Dimuzio
authors: Yi
authors: Y
authors: Xie
authors: R Preston
authors: RP
authors: Mason
authors: G Stephen
authors: GS
authors: Tint
authors: Robert D
authors: RD
authors: Steiner
authors: Jean-Baptiste
authors: JB
authors: Roullet
authors: Louise
authors: L
authors: Merkens
authors: Diana
authors: D
authors: Whitaker-Menezes
authors: Philippe G
authors: PG
authors: Frank
authors: Michael P
authors: MP
authors: Lisanti
authors: Robert H
authors: RH
authors: Cox
authors: Thomas N
authors: TN
authors: Tulenko
mesh_terms: D021941:Caveolae / Q000378:metabolism*; D051242:Caveolin 1 / Q000378:metabolism; D002478:Cells, Cultured; D003684:Dehydrocholesterols / Q000737:chemistry / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism*; D005838:Genotype; D006801:Humans; D015151:Immunoblotting; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000378:metabolism*; D008567:Membranes, Artificial; D008854:Microscopy, Electron; D015394:Molecular Structure; D012867:Skin / Q000166:cytology; D019082:Smith-Lemli-Opitz Syndrome / Q000378:metabolism*; D013261:Sterols / Q000378:metabolism; D014961:X-Ray Diffraction
chemical_list: D051242:Caveolin 1; D003684:Dehydrocholesterols; C494841:KCNMA1 protein, human; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D008567:Membranes, Artificial; D013261:Sterols; C016705:7-dehydrocholesterol