FIG 5.

Certain lipids affect the sensitivity of β-glucan synthase to CAS. (A and B) Lipidomics analysis of enriched glucan synthase from RG101 grown in the absence and presence (1 μg/ml) of CAS showed (A) >2-fold-increased abundance of dihydrosphingosine (DhSph) and (B) 10-fold-increased abundance of phytosphingosine (PhytoSph) in CAS-exposed cells. (C) Addition of DhSph and PhytoSph at a concentration of 150 μg/ml for 1 h to enriched glucan synthase extract in the enzyme assay made the enzyme insensitive to CAS [IC₅₀ (no lipid) = ∼0.01 ng/ml; IC₅₀ (150 μg/ml DhSph) = 0.1 ng/ml; IC₅₀ (150 μg/ml PhytoSph) = ∼100 ng/ml], whereas addition of other lipids such as phytoceramide did not alter the enzyme property [IC₅₀ (150 μg/ml C2 PhytoCer) = ∼0.01 ng/ml].