Figure 6.

Cellular cholesterol levels regulate metalloproteinase-dependent shedding of LRP-1 ectodomain. Cholesterol content (A, C) was measured in the two HT1080 variants; LRP-1 ectodomain shedding (B, D) was quantified on Western blots of α-chain released in the corresponding concentrated medium conditioned for 6 h (or 24 h for lovastatin treatment; data normalized as a percentage of untreated fibroblastoid cells) as described in Materials and Methods. A, B) Effect of acute cholesterol depletion. Fibroblastoid and epithelioid HT1080 cells were treated without (−) or with (+) 5 mM empty MβCD for 30 min (n=6). C, D) Cholesterol was enriched in fibroblastoid cells by exogenous supply with 1 mM chol-MβCD for 90 min (+ chol; n=3). Alternatively, cholesterol was metabolically depleted in epithelioid HT1080 cells by treatment with 4 μM lovastatin for 24 h (n=5). NS, not significant. Values are means ± sd. *P < 0.05, **P < 0.005, ***P < 0.0005; Student's t test.