HPV16 E5 protein disrupts the c-Cbl–EGFR interaction and EGFR ubiquitination in human foreskin keratinocytes

Abstract

The E5 protein of human papillomavirus type 16 (HPV16) is a small hydrophobic protein, which localizes to the cell membrane, Golgi apparatus and endosomes. HPV16 E5 enhances the activation of the epidermal growth factor (EGFR). The activated EGFR is downregulated through the endocytic pathway, where E5 has been shown to inhibit endosomal acidification and trafficking. Ubiquitination of the activated EGFR plays a role in this downregulation. cCbl is a ubiquitin ligase that associates with the activated EGFR and targets it for degradation. Since E5 has been shown to form a complex with the EGFR, we tested the hypothesis that E5 affects the interaction of c-Cbl with the EGFR. We found a significant decrease of c-Cbl bound to the EGFR and of ubiquitinated EGFR in the presence of E5. E5 did not affect c-Cbl steady-state level, phosphorylation or translocation to the membrane. This novel result suggests that HPV16 E5 may, at least in part, upregulate EGFR-mediated signal transduction by inhibiting the interaction of c-Cbl with the EGFR, thereby decreasing c-Cbl-mediated degradation of the EGFR.

Abl Tyrosine Kinase Regulates Endocytosis of the Epidermal Growth Factor Receptor

“…EGFR endocytosis has been shown previously to be regulated by tyrosine phosphorylation in the cytoplasmic tail of the EGFR (7,14,43,44). Oncogenic EGFR mutants such as the EGFRvIII show increased levels of tyrosine 1173 phosphorylation (35,45).…”

Itraconazole suppresses the growth of glioblastoma through induction of autophagy

“…37 In contrast, both GAPDH (a cytosolic protein) and MT-CO1 (mitochondrially encoded cytochrome c oxidase I; a mitochondrial membrane protein) were rarely detected in the isolated plasma membrane, confirming the purity of the isolated plasma membrane. 38,39 Treatment with itraconazole resulted in a marked reduction of plasma membrane cholesterol, compared with the DMSO-treated control group (Fig. 7B).…”

HPV16 E5 affects the KGFR/FGFR2b-mediated epithelial growth through alteration of the receptor expression, signaling and endocytic traffic

“…The oncogenic role of HPV16 E5 in epithelial transformation and malignant progression has been widely attributed to the ability of this viral protein to interfere with the endocytic pathway of signaling receptors, mainly of EGFR, either indirectly through inhibition of the endosomal acidification (Straight et al, 1995) and endosomal vesicle fusion (Suprynowicz et al, 2010), or directly through protein interactions with the receptor tyrosine kinases (Hwang et al, 1995;Zhang et al, 2005). As mentioned above, results obtained in previous studies from our group (Belleudi et al, 2006(Belleudi et al, , 2007 demonstrate that KGFR endocytosis on binding of the two alternative ligands, KGF or FGF10, is clathrindependent; however, once internalized the receptors follow two different intracellular endocytic pathways: while KGF targets the receptor to the lysosomal pathway, FGF10 induces KGFR recycling to the plasma membrane.…”

“…More recently, however, it has been proposed that 16E5 affects the EGF endocytic trafficking altering the endosome fusion through a pH-independent and cytoskeletonindependent mechanism (Suprynowicz et al, 2010). In addition, it has been also demonstrated that E5 protein is able to form a complex with the EGFR and to enhance its ligand-dependent signaling by disrupting EGFR/c-Cbl interaction and consequently decreasing the ubiquitin-mediated receptor degradation (Zhang et al, 2005).…”