Human papillomavirus type 16 E5 oncoprotein (HPV16 E5)

The Human papillomavirus type 16 (HPV16) E5 oncoprotein is a small, 83-amino acid hydrophobic membrane protein that functions as a viroporin and a critical mediator of early viral oncogenesis (UniProt P06927). It is primarily localized to the endoplasmic reticulum and Golgi apparatus, where it interacts with various cellular proteins, including the 16 kDa subunit of the vacuolar H+-ATPase and the epidermal growth factor receptor (EGFR) (PubMed: 22438551). By inhibiting endosomal acidification and receptor degradation, E5 enhances EGFR signaling and downstream MAPK/ERK activation, promoting cell proliferation and survival (PubMed: 20634278). Additionally, E5 facilitates immune evasion by downregulating the surface expression of MHC class I and II molecules, thereby preventing the presentation of viral antigens to the host immune system (PubMed: 31848197). Although E5 is often lost during the integration of the HPV genome into the host DNA in advanced cancers, it is highly expressed in early-stage lesions and episomal infections, making it a strategic target for therapeutic vaccines like PRGN-2009 and small-molecule inhibitors like rimantadine (Cancer Res. 2020;80(4):732-746). Recent studies have also identified E5 as a mediator of resistance to anti-PD-L1 immunotherapy, suggesting that targeting E5 could improve clinical outcomes in head and neck and cervical cancers (PubMed: 31848197).

Other names

HPV16 E5E5 protein16E5Oncogene protein E5HPV-16 E5

Inhibition of viroporin ion channel activity; induction of T-cell mediated immune response; inhibition of EGFR recycling; restoration of MHC class I/II surface expression.