FIGURE 8.
VEGF-induced occludin degradation is mediated via the ubiquitin/proteasomal system. A, after protein synthesis was inhibited by cycloheximide (CHX) (10 μg/ml) occludin content was evaluated by Western blotting. VEGF (50 ng/ml) enhanced the rate of occludin degradation, which was blocked by MG132 (50 μm). The rate of claudin-5 degradation was not changed by either VEGF or MG132. n = 7–8. Error bars represent the S.D. B, after the pretreatment with MG132 (50 μm), BRECs were treated with VEGF (50 ng/ml, 15 min). MG132 increased ubiquitinated occludin with or without VEGF. IP, immunoprecipitated; IB, immunoblot.