ARIA modulates proteasomal degradation of cIAP-1 and cIAP-2. (A) HA-tagged PSMA-7 and/or FLAG-tagged ARIA were expressed in BAECs. HA-PSMA7 and ARIA-FLAG were immunoprecipitated by anti-HA antibody and anti-FLAG M2 antibody, respectively. Coprecipitation of HA-PSMA7 and ARIA-FLAG was observed. (B) Proteasome inhibition with MG132 significantly increased cIAP-1 and cIAP-2, but not XIAP, expression in HUVECs. Similar results were obtained by 3 independent experiments. (C) However, when ARIA was knocked down, proteasome inhibition failed to further increase cIAP-1 and cIAP-2 expression. Similar results were obtained in 2 independent experiments. (D) Overexpression of human ARIA significantly reduced cIAP-1 expression in BAECs. Proteasome inhibition with MG132 abrogated this effect of ARIA overexpression on cIAP-1 expression. Similar results were obtained in 2 independent experiments. (E) Expression and subcellular localization of cIAP-1, cIAP-2, and XIAP in HUVECs. An effect of ARIA knockdown similar to proteasomal inhibition was observed with respect to expression as well as subcellular localization of cIAP-1 and cIAP-2. (Scale bar, 100 μm.) Similar results were obtained in 3 independent experiments.