PMID- 22733765 OWN - NLM STAT- MEDLINE DCOM- 20121029 LR - 20211021 IS - 1091-6490 (Electronic) IS - 0027-8424 (Print) IS - 0027-8424 (Linking) VI - 109 IP - 33 DP - 2012 Aug 14 TI - Functional isolation of activated and unilaterally phosphorylated heterodimers of ERBB2 and ERBB3 as scaffolds in ligand-dependent signaling. PG - 13237-42 LID - 10.1073/pnas.1200105109 [doi] AB - The EGFR (ERBB) family provides a model system for receptor signaling, oncogenesis, and the development of targeted therapeutics. Heterodimers of the ligand-binding-deficient ERBB2 (HER2) receptor and the kinase impaired ERBB3 (HER3) create a potent mitogenic signal, but the phosphorylation of ERBB2 in this context presents a challenge to established models of phosphorylation in trans. Higher order complexes of ERBB receptors have been observed biophysically and offer a theoretical route for ERBB2 phosphorylation, but it is not clear whether such complexes provide functionality beyond the constituent dimers. We now show that a previously selected inhibitory RNA aptamer that targets the extracellular domain (ECD) of ERBB3 acts by sterically disrupting these higher order interactions. Ligand binding, heterodimerization, phosphorylation of ERBB3, and AKT signaling are only minimally affected, whereas ERBB2 phosphorylation and MAPK signaling are selectively inhibited. The mapping of the binding site and creation of aptamer-resistant point mutants are consistent with a model of side-by-side oriented heterodimers to facilitate proxy phosphorylation, even at very low endogenous levels of receptors (below 10,000 receptors per cell). Additional modes of signaling with relevance to pathological ERBB expression states emerge at high receptor levels. Hence, higher order complexes of nonoverexpressed ERBB receptors are an integral and qualitatively distinct part of normal ERBB2/ERBB3 signaling. This mechanism of activation has implications for models of allosteric control, specificity of interactions, possible mechanisms of cross-talk, and approaches to therapeutic intervention that at present often generate experimental and clinical outcomes that do not reconcile with purely canonical, dimer-based models. FAU - Zhang, Qian AU - Zhang Q AD - Department of Biochemistry and Molecular Biology, Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, FL 33136, USA. FAU - Park, Euisun AU - Park E FAU - Kani, Kian AU - Kani K FAU - Landgraf, Ralf AU - Landgraf R LA - eng GR - R01 CA098881/CA/NCI NIH HHS/United States GR - CA98881-05/CA/NCI NIH HHS/United States PT - Journal Article PT - Research Support, N.I.H., Extramural PT - Research Support, Non-U.S. Gov't DEP - 20120625 PL - United States TA - Proc Natl Acad Sci U S A JT - Proceedings of the National Academy of Sciences of the United States of America JID - 7505876 RN - 0 (Aptamers, Nucleotide) RN - 0 (Ligands) RN - EC 2.7.10.1 (Receptor, ErbB-2) RN - EC 2.7.10.1 (Receptor, ErbB-3) RN - EC 2.7.11.24 (Mitogen-Activated Protein Kinases) SB - IM CIN - Proc Natl Acad Sci U S A. 2012 Aug 14;109(33):13140-1. PMID: 22851769 MH - Aptamers, Nucleotide/metabolism MH - Cell Line, Tumor MH - Enzyme Activation MH - Humans MH - Ligands MH - Mitogen-Activated Protein Kinases/antagonists & inhibitors/metabolism MH - Phosphorylation MH - Protein Binding MH - *Protein Multimerization MH - Protein Structure, Tertiary MH - Receptor, ErbB-2/chemistry/*metabolism MH - Receptor, ErbB-3/chemistry/*metabolism MH - *Signal Transduction MH - Structural Homology, Protein PMC - PMC3421218 COIS- The authors declare no conflict of interest. EDAT- 2012/06/27 06:00 MHDA- 2012/10/30 06:00 PMCR- 2013/02/14 CRDT- 2012/06/27 06:00 PHST- 2012/06/27 06:00 [entrez] PHST- 2012/06/27 06:00 [pubmed] PHST- 2012/10/30 06:00 [medline] PHST- 2013/02/14 00:00 [pmc-release] AID - 1200105109 [pii] AID - 201200105 [pii] AID - 10.1073/pnas.1200105109 [doi] PST - ppublish SO - Proc Natl Acad Sci U S A. 2012 Aug 14;109(33):13237-42. doi: 10.1073/pnas.1200105109. Epub 2012 Jun 25.