GM1-deficient C6 cells are sensitized to CT by inhibition of sialylation or GSL biosynthesis.

<p><b>(A-E)</b> C6 cells were cultured with the indicated inhibitors for 72 h followed by: <b>(A)</b> Staining was then performed with biotin-CTB, followed by DTAF-streptavidin. Fluorescence was measured by flow cytometry, represented here by MFI. <b>(B)</b> 1 h exposure to CT after which accumulated cAMP was measured by the cAMP-Glo™ luminescence assay. Luminescence signal is inversely proportional to cAMP levels. <b>(C)</b> As in panel <b>A</b>, but stained with biotin-PNA, followed by DTAF-streptavidin <b>(D)</b> Cell lysates were separated by PAGE and probed with biotin-PNA, biotin-CTB, or no biotinylated reagent, followed by streptavidin-peroxidase conjugate and development with chemiluminescent substrate. Equivalent amounts of protein were loaded in each lane and blots were probed with an anti-α-tubulin or anti-GAPDH antibody to confirm equivalent loading. <b>(E)</b> As in panel <b>B</b>, but brefeldin A (BFA) was added 1 h prior to CT addition and was also present during CT induction.</p>