Cancer regulator EGFR-ErbB4 heterodimer is stabilized through glycans at the dimeric interface

Abstract

The ErbB family of tyrosine kinase receptors is composed of four homologous members, including EGFR (ErbB1/HER1), ErbB2 (HER2), ErbB3 (HER3), and ErbB4 (HER4). Since the ErbB proteins play vital roles in various developmental processes, their mutation or overexpression leads to severe abnormalities such as cancer. The general mechanism of ErbB receptors activity is binding to growth factors via their extracellular domain followed by tyrosine phosphorylation intracellularly. Yet the EGFR and ErbB4 are the only two members that keep their ligand-binding domain and the tyrosine kinase activated. In contrast, ErbB2 and ErbB3 are incapable of keeping their ligand-binding and kinase domains activated, respectively. Active ErbB receptors form homo and heterodimers by binding of two similar or different family members together, respectively. Ligands and intracellular pathways that could be activated through heterodimerization are more diverse compared to homodimers. Moreover, it is known that Nglycosylation is critical for stabilizing and activating the ErbB receptors. In this study, atomistic molecular dynamics simulations were used on one of the most potentiated ErbB heterodimers (EGFR-ErbB4) in the glycosylated and unglycosylated states. It was shown that the EGFR-ErbB4 heterodimer is highly stabilized by glycosylation. The increased stability is most signi cant at the dimeric interfaces. Regulated by packing of three glycans attached to EGFR (Asn337) and ErbB4 (Asn333, Asn523) at the dimeric interface. Finally, it is proposed that heterodimerization is the persistent key player of the ErbB receptors activation. Thus, targeting the heterodimers in future therapeutic designs could be a promising approach against drug resistance ErbB positive cancers.

Structural dynamics of the active HER4 and HER2/HER4 complexes is finely tuned by different growth factors and glycosylation

“…To our knowledge, the cryo-EM maps of HER4 homodimers and HER2/HER4 heterodimers offer the first glimpse into extensive glycan-mediated contacts in an active HER receptor dimer. The observed interactions might explain some of the stabilizing effects of HER receptor glycosylation previously suggested ( Motamedi et al, 2022 ). We identified glycans in both HER2 and HER4 that directly connect their domains I and II and the HER4-specific interdomain glycan connections between domains II and IV.…”

“…In recent years several studies of the effects of HER receptor glycosylation on their structure and signaling have been conducted using molecular dynamics (MD) generating models on how glycans contribute to receptor stability and its interactions with the membrane ( Taylor et al, 2017 ; Arkhipov et al, 2013 ; Kaszuba et al, 2015 ; Azimzadeh Irani et al, 2017 ). Most recently, MD simulations conducted on the HER4/EGFR heterodimer models have suggested that the glycans present on HER4 N358 and N548, as well as EGFR N361 (which is equivalent to HER4 N358), form a connection in the dimerization interface that effectively stabilizes the heterodimer ( Motamedi et al, 2022 ). Our current study provides the first direct experimental evidence that these glycan interactions are operative at the level of HER4 homodimers.…”

Structural dynamics of the active HER4 and HER2/HER4 complexes is finely tuned by different growth factors and glycosylation

“…To our knowledge, the cryo-EM maps of HER4 homodimers and HER2/HER4 heterodimers offer the first glimpse into extensive glycan-mediated contacts in an active HER receptor dimer. The observed interactions might explain some of the stabilizing effects of HER receptor glycosylation previously suggested [62]. We identified glycans in both HER2 and HER4 that directly connect their domains I and II and the HER4-specific interdomain glycan connections between domains II and IV.…”

“…In recent years several studies of the effects of HER receptor glycosylation on their structure and signaling has been conducted using molecular dynamics (MD) generating models on how glycans contribute to receptor stability and its interactions with the membrane [63][64][65][66]. Most recently, MD simulations conducted on the HER4/EGFR heterodimer models have suggested that the glycans present on HER4 N358 and N548, as well as EGFR N361 (which is equivalent to HER4 N358), form a connection in the dimerization interface that effectively stabilizes the heterodimer [62]. Our current study provides first direct experimental evidence that these glycan interactions are operative at the level of HER4 homodimers.…”