Identification of an HSP90 modulated multi-step process for ERBB2 degradation in breast cancer cells

• DOI: 10.18632/oncotarget.13392
• Publication Date: 2016-11-16T20:52:51Z
• Authors: Patrizio Castagnola; Grazia Bellese; Filippo Birocchi; Maria Cristina Ga...; Carlo Tacchetti; Katia Cortese
• Keywords: Lactacystin; Wortmannin; Protein Degradation

The receptor tyrosine kinase ERBB2 interacts with HSP90 and is overexpressed in aggressive breast cancers. Therapeutic inhibitors, i.e. Geldanamycin (GA), target to degradation. We have previously shown that responsible for the missorting of recycling degradation compartments. In this study, we used biochemical, immunofluorescence electron microscopy techniques demonstrate SKBR3 human cancer cells, GA strongly induces polyubiquitination internalization full-length p185-ERBB2, promotes its cleavage, formation a p116-ERBB2 form EEA1-positive endosomes (EE). corresponds non-ubiquitinated, signaling-impaired, membrane-bound fragment, which readily sorted lysosomes degraded. To define sequence events leading degradation, first blocked EE maturation/trafficking late endosomes/lysosomes wortmannin, found an increase GA-dependent p116-ERBB2; then inhibited proteasome activity MG-132 or lactacystin, observed efficient block p185-ERBB2 accumulation EE, suggesting necessary proteasome-dependent generation occurring EE. As has also been implicated autophagy-mediated under different experimental conditions, exploited possibility inhibits early autophagy, reduces levels autophagy markers atg5-12 LC3-II, irrespective GA-induced polyubiquitination, ruling out autophagic ERBB2. conclusion, propose inhibition fosters non-ubiquitinated inactive trafficked from altered lysosomes.