Fig. 4. Cellular cholesterol levels affect chemotactic cell migration. (A) CD24^+/+ 18H18⁺ cells were loaded with cholesterol by incubation with 30 µg/ml soluble cholesterol and tested for chemotactic cell migration in response to SDF-1. CD24^–/– cells N232.18 and 18H18^– were treated with fluvastatin for 72 hours and then tested for chemotactic cell migration in response to SDF-1. Data are presented as the percentage migration (± s.e.m.) compared with untreated control cells. (B) SDF-1-triggered ERK-phosphorylation in CD24^–/– (N232.18 and 18H18^–) and CD24^+/+ (18H18⁺) cells. Cells were exposed for the indicated length of time (in minutes) to 100 ng/ml SDF-1 then lysed. An equal volume of lysate was mixed with sample buffer and analysed by SDS-PAGE and western blotting using a phospho-ERK-specific antibody and ECL detection. For a loading control, blots were reprobed with an ERK-1-specific antibody. (C) CD24^–/– (18H18^–) cells were treated with fluvastatin for 72 hours and then ERK phosphorylation in response to SDF-1 was tested. Note that ERK phosphorylation in 18H18^– cells was abolished after fluvastatin treatment.