1. Adenosine Triphosphate Binding Cassette (ABC) Transporters Are Expressed and Regulated During Terminal Keratinocyte Differentiation: A Potential Role for ABCA7 in Epidermal Lipid Reorganization 
Danuta Kielar, Wolfgang E. Kaminski, Gerhard Liebisch, Armin Piehler, Jürgen J. Wenzel, Christoph Möhle, Susanne Heimerl, Thomas Langmann, Sven O. Friedrich, Alfred Böttcher, Stefan Barlage, Wolfgang Drobnik, Gerd Schmitz 
Journal of Investigative Dermatology 
Volume 121, Issue 3, Pages (September 2003)
DOI: /j x
Copyright © 2003 The Society for Investigative Dermatology, Inc Terms and Conditions

2. Figure 1
Increase of intracellular and cell surface ceramide levels in differentiating human keratinocytes. Intracellular ceramide content increases continuously during calcium-induced in vitro keratinocyte differentiation (A), which is paralleled by an upregulation of cell surface ceramide and its metabolites lactosylceramide and globotriaosylceramide, respectively (B). Intracellular lipids were quantitated by ESI-MS/MS and cell surface ceramide compounds were assessed by flow cytometry using specific antibodies (for details see Materials and Methods). Results are indicated as percentage change relative to day 1 of culturing (=100%). The data shown represent mean±SD of three experiments measured in triplicate, p<0.05. PC, phosphatidylcholine; PE, phosphatidylethanolamine; PS, phosphatidylserine; SPM, sphingomyelin.
Journal of Investigative Dermatology  , DOI: ( /j x)
Copyright © 2003 The Society for Investigative Dermatology, Inc Terms and Conditions

3. Figure 2
mRNA expression profiles of ABC transporters that are upregulated during keratinocyte differentiation. A total of six ABC transporters were identified that showed significant differentiation-dependent regulation in human keratinocytes. These include ABCA7 (A), ABCB1 (MDR1) and ABCG1 (B), and the ABC C subfamily transporters ABCC1 (MRP1), ABCC3 (MRP3) and ABCC4 (MRP4), respectively (C). The expression of the cholesterol and phospholipid export facilitator ABCA1 is shown as a reference in (A). mRNA expression profiles were assessed by semiquantitative Lightcycler reverse transcription–PCR. Mean±SEM values are indicated as target gene/GAPDH ratios. Data represent three independent experiments each measured in triplicate, p<0.01.
Journal of Investigative Dermatology  , DOI: ( /j x)
Copyright © 2003 The Society for Investigative Dermatology, Inc Terms and Conditions

4. Figure 3
Forced expression of ABCA7 in HeLa cells induces an increase in intracellular ceramide and phosphatidylserine levels. (A) Lipid profiles of HeLa cells stably overexpressing human ABCA7. Note the significant increase in intracellular ceramide and phosphatidylserine and the moderate elevation of phosphatidylcholine concentrations. Lipids were quantitated by ESI-MS/MS and values are shown as percentage change relative to mock-transfected HeLa cells (=100%). Each bar represents the mean±SEM of five independent experiments each perfomed in triplicate. PC, phosphatidylcholine; PE, phosphatidylethanolamine; phosphatidylserine, phosphatidylserine; SPM, sphingomyelin *p<0.05, **p<0.01. Inset: ABCA7 protein levels in mock-transfected and ABCA7 overexpressing HeLa cells (ABCA7+) assessed by western blot using the ABCA7-11R antibody. (B) Increased cell surface ceramide expression in ABCA7 overexpressing HeLa cells (black bars) relative to mock-transfected controls (gray bars). Shown is the ceramide cell surface content in total transfected cells vs. the propidium iodide positive (PI+) and negative (PI-) subpopulations representing viable and nonviable HeLa cells, respectively. Cell surface ceramide expression was analyzed by flow cytometry using a FITC-labeled anti-ceramide antibody. Data represent mean±SEM fluorescence intensities of three independent experiments. Note the significantly higher percentage of nonviable cells in ABCA7 overexpressing HeLa cells compared with mock-transfected controls (inset). MFI, mean fluorescence intensity.
Journal of Investigative Dermatology  , DOI: ( /j x)
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5. Figure 4
Cell cycle distribution of asynchronously growing mock-transfected and ABCA7 overexpressing HeLa cells. Note the significant increase of G2/M-phase cells in ABCA7 overexpressing cells indicative of a G2/M phase arrest. Cells were incubated with 10% fetal calf serum in DMEM for 72 h and subsequently cell cycle distribution was determined. Data are shown as percent of total cells. Each bar represents the mean±SEM of one representative experiment performed in triplicate. *p<0.01, ***p<
Journal of Investigative Dermatology  , DOI: ( /j x)
Copyright © 2003 The Society for Investigative Dermatology, Inc Terms and Conditions