Epidermal Growth Factor Receptor neddylation is regulated by a desmosomal-COP9 (Constitutive Photomorphogenesis 9) signalosome complex

Abstract

Cell junctions are scaffolds that integrate mechanical and chemical signaling. We previously showed that a desmosomal cadherin promotes keratinocyte differentiation in an adhesion-independent manner by dampening Epidermal Growth Factor Receptor (EGFR) activity. Here we identify a potential mechanism by which desmosomes assist the de-neddylating COP9 signalosome (CSN) in attenuating EGFR through an association between the Cops3 subunit of the CSN and desmosomal components, Desmoglein1 (Dsg1) and Desmoplakin (Dp), to promote epidermal differentiation. Silencing CSN or desmosome components shifts the balance of EGFR modifications from ubiquitination to neddylation, inhibiting EGFR dynamics in response to an acute ligand stimulus. A reciprocal relationship between loss of Dsg1 and neddylated EGFR was observed in a carcinoma model, consistent with a role in sustaining EGFR activity during tumor progression. Identification of this previously unrecognized function of the CSN in regulating EGFR neddylation has broad-reaching implications for understanding how homeostasis is achieved in regenerating epithelia.

Desmosomes as Signaling Hubs in the Regulation of Cell Behavior

“…This dampened EGFR signaling and consequently cell division, and allowed differentiation to proceed. These data support a model where DSG1-dependent scaffolding of the COP9 signalosome facilitates epidermal differentiation by controlling EGFR dynamics ( Najor et al, 2017 ).…”

Direct Conjugation of NEDD8 to the N-Terminus of a Model Protein Can Induce Degradation

“…Several recent reports have highlighted the potential for non-canonical NEDDylation to result in a target protein’s destabilization and destruction. The first substrate identified that could be destabilized and destroyed following NEDD8 conjugation was the epithelial growth factor receptor (EGFR) [ 40 , 41 ]. Other proteins soon joined the list of substrates that could be destabilized and degraded following NEDDylation including HDAC, JunB, SMF2, c-Src, SRSF3, Ajuba, and E2F-1 [ 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ].…”

Proximity Ligation Assay for Detecting Protein‐Protein Interactions and Protein Modifications in Cells and Tissues in Situ

“…EGFR is stabilized at the plasma membrane in part by the process of neddylation, the addition of Nedd8 moieties to the C‐terminus. De‐neddylation is mediated by a large protein complex, the COPS9 signalosome, and results in the ubiquitination of EGFR and turnover of the receptor (Najor et al., 2017). ( A ) PLA using an antibody pair recognizing EGFR mouse and the Nedd8 moiety rabbit demonstrates the level of post‐translational modification of EGFR in the epithelial cells, visualized by PLA reaction “spots” in red (Duolink™ In Situ Detection Reagent Red, λ Ex : 594, λ Em : 624).…”

“…In Figure 3, the ability of PLA to reveal post‐translational modifications of epidermal growth factor receptor (EGFR) are presented. An antibody recognizing EGFR is used in combination with an antibody recognizing ubiquitin or Nedd8, a ubiquitin‐like protein (Najor et al., 2017). In this experiment, the authors questioned whether Nedd8 and ubiquitin could compete for lysine residues on EGFR.…”