In Vivo Knockdown of Pathogenic Proteins via S pecific and N ongenetic I nhibitor of Apoptosis Protein (IAP)-dependent P rotein Er asers (SNIPERs)

J Biol Chem. 2017 Mar 17;292(11):4556-4570. doi: 10.1074/jbc.M116.768853. Epub 2017 Feb 2.

Abstract

Many diseases, especially cancers, result from aberrant or overexpression of pathogenic proteins. Specific inhibitors against these proteins have shown remarkable therapeutic effects, but these are limited mainly to enzymes. An alternative approach that may have utility in drug development relies on selective degradation of pathogenic proteins via small chimeric molecules linking an E3 ubiquitin ligase to the targeted protein for proteasomal degradation. To this end, we recently developed a protein knockdown system based on hybrid small molecule SNIPERs (Specific and Nongenetic IAP-dependent Protein Erasers) that recruit inhibitor of the apoptosis protein (IAP) ubiquitin ligases to specifically degrade targeted proteins. Here, we extend our previous study to show a proof of concept of the SNIPER technology in vivo By incorporating a high affinity IAP ligand, we developed a novel SNIPER against estrogen receptor α (ERα), SNIPER(ER)-87, that has a potent protein knockdown activity. The SNIPER(ER) reduced ERα levels in tumor xenografts and suppressed the growth of ERα-positive breast tumors in mice. Mechanistically, it preferentially recruits X-linked IAP (XIAP) rather than cellular IAP1, to degrade ERα via the ubiquitin-proteasome pathway. With this IAP ligand, potent SNIPERs against other pathogenic proteins, BCR-ABL, bromodomain-containing protein 4 (BRD4), and phosphodiesterase-4 (PDE4) could also be developed. These results indicate that forced ubiquitylation by SNIPERs is a useful method to achieve efficient protein knockdown with potential therapeutic activities and could also be applied to study the role of ubiquitylation in many cellular processes.

Keywords: LCL161; SNIPER; X-linked inhibitor of apoptosis protein (XIAP); estrogen receptor; proteasome; tumor therapy; ubiquitin.

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology
  • Antineoplastic Agents / therapeutic use*
  • Breast / drug effects
  • Breast / metabolism
  • Breast / pathology
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology
  • Cell Line
  • Cell Line, Tumor
  • Drug Discovery
  • Estrogen Receptor alpha / antagonists & inhibitors
  • Estrogen Receptor alpha / metabolism*
  • Female
  • Humans
  • Inhibitor of Apoptosis Proteins / antagonists & inhibitors
  • Inhibitor of Apoptosis Proteins / metabolism*
  • Ligands
  • Mice
  • Mice, Inbred BALB C
  • Mice, Nude
  • Proteasome Endopeptidase Complex / metabolism
  • Proteolysis / drug effects*
  • Small Molecule Libraries / pharmacology
  • Small Molecule Libraries / therapeutic use*
  • Ubiquitination / drug effects
  • X-Linked Inhibitor of Apoptosis Protein / metabolism

Substances

  • Antineoplastic Agents
  • ESR1 protein, human
  • Estrogen Receptor alpha
  • Inhibitor of Apoptosis Proteins
  • Ligands
  • Small Molecule Libraries
  • X-Linked Inhibitor of Apoptosis Protein
  • Proteasome Endopeptidase Complex