Primary HUVEC were treated with 500 nM MLN7243, 500 nM MLN4924 or DMSO (control) for 6 h. The experiment aims to identify up- or downregulated proteins after treatment with the E1 ligase inhibitor MLN7243 and the cullin inhibitor MLN4924 in HUVEC. Proteins that are regulated by ubiquitination or more specifically by cullin-based E3 ligases in the quiescent endothelium, will be identified.