Figure 1. Glucose activates SREBPs via upregulation of SCAP.

(A) Western blot analysis of U87 cells cultured in serum-free media with or without glucose (5 mM) in the presence or absence of sterols (10 µg/ml 25-hydroxycholesterol, and 10 µg/ml cholesterol) for 12 hr.

(B, C) Western blot analysis of U87 cells cultured in serum-free media with different dose of glucose for 12 hr (B) or stimulated with 5 mM glucose at indicated times (C).

(D, E) Confocal microscopy images show GFP-SREBP-1 (green), which was derived from a cDNA lacking the exon 1 of SREBP-1 (encodes the identical amino acid sequence between SREBP-1a and −1c) (D) or endogenous SREBP-1 (E, red) subcellular localization in U87 cells cultured in serum-free media with or without glucose (Gluc) for 12 hr. Nuclei were stained by DAPI (blue). Scale bars, 10 µm. The nucleus intensity of GFP-SREBP-1 (D) or endogenous SREBP-1 (red) (E) was quantified over 30 cells by using ImageJ. Red lines in the quantification graphs show mean ± SEM (n = 30). Significance was determined by an unpaired student t test.

(F) Western blot analysis of membrane and nuclear extracts from U87 cells cultured in serum-free media with or without glucose (5 mM) for 12 hr.

(G, H) Western blot analysis of membrane, nuclear extracts or total cell lysates from HEK293T cells co-transfected with GFP-SCAP or GFP vector and full length (FL) Flag-SREBP-1a, −1c or HA-SREBP-2 plasmids (G) or from U87 cells after knockdown of SCAP in comparison with shRNA control (shCtrl) in serum-free media with or without glucose (5 mM) for 12 hr (H). P, precursor of SREBPs; N, N-terminus of SREBP-1. C, C-terminus of SREBP-2.

See also Figure S1.