Abstract
Development of novel small molecules that selectively degrade pathogenic proteins would provide an important advance in targeted therapy. Recently, we have devised a series of hybrid small molecules named SNIPER (Specific and Non-genetic IAP-dependent Protein ERaser) that induces the degradation of target proteins via the ubiquitin-proteasome system. To understand the localization of proteins that can be targeted by this protein knockdown technology, we examined whether SNIPERs are able to induce degradation of CRABP-II proteins localized in subcellular compartments of cells. CRABP-II is genetically fused with subcellular localization signals, and they are expressed in the cells. SNIPER(CRABP)s with different IAP-ligands, SNIPER(CRABP)-4 with bestatin and SNIPER(CRABP)-11 with MV1, induce the proteasomal degradation of wild-type, cytosolic, nuclear and membrane-localized CRABP-II proteins, whereas only SNIPER(CRABP)-11 displayed degradation activity towards the mitochondrial CRABP-II protein. The siRNA-mediated silencing of cIAP1 expression attenuated the knockdown activity of SNIPER(CRABP)s against wild-type and cytosolic CRABP-II proteins, indicating that cIAP1 is the E3 ligase responsible for degradation of these proteins. Against membrane-localized CRABP-II protein, cIAP1 is also a primary E3 ligase in the cells, but another E3 ligase distinct from cIAP2 and XIAP could also be involved in the SNIPER(CRABP)-11-induced degradation. However, for the degradation of nuclear and mitochondrial CRABP-II proteins, E3 ligases other than cIAP1, cIAP2 and XIAP play a role in the SNIPER-mediated protein knockdown. These results indicate that SNIPER can target cytosolic, nuclear, membrane-localized and mitochondrial proteins for degradation, but the responsible E3 ligase is different depending on the localization of the target protein.
- The American Society for Pharmacology and Experimental Therapeutics