PMID:11739687

Citation	Zhang, B, Spandau, DF and Roman, A (2002) E5 protein of human papillomavirus type 16 protects human foreskin keratinocytes from UV B-irradiation-induced apoptosis. J. Virol. 76:220-31
Abstract	The human papillomavirus type 16 (HPV16) E5 protein associates with the epidermal growth factor receptor (EGFR) and enhances the activation of the EGFR after stimulation by EGF in human keratinocytes. Phosphatidylinositol 3-kinase (PI3K) and ERK1/2 mitogen-activated protein kinase (ERK1/2 MAPK), two signal molecules downstream of the EGFR, have been recognized as participants in two survival signal pathways in response to stress. The fact that E5 can enhance EGFR activation suggests that E5 might act as a survival factor. To test this hypothesis, the apoptotic response of UV B-irradiated primary keratinocytes infected with either control retrovirus, LXSN, or HPV16 2E5-expressing recombinant retrovirus was quantitated. Under the same conditions, LXSN-infected cells showed extensive apoptosis, while E5-expressing cells demonstrated a significant reduction in UV B-irradiation-induced apoptosis. The E5-mediated protection against apoptosis was blocked by wortmannin and PD98059, specific inhibitors of the PI3K and ERK1/2 MAPK pathways, respectively, suggesting that the PI3K and ERK1/2 MAPK pathways are involved in this process. Western blot analysis showed that Akt (also named protein kinase B), which is a downstream effector of PI3K, and ERK1/2 MAPK were activated by EGF. When cells were stimulated by EGF and irradiated by UV B, the levels of phospho-Akt and phospho-ERK1/2 activated by EGF in E5-expressing cells were about twofold greater than those in LXSN-infected cells. Two other UV-activated stress pathways, p38 and JNK, were activated to the same level during UV B irradiation in both LXSN-infected cells and E5-expressing cells, indicating that E5 protein did not affect these two pathways. After UV B irradiation, p53 was activated in both LXSN-infected cells and E5-expressing cells, and cell cycle analysis showed that nearly all cells in both cell populations were growth arrested. These data suggest that unlike HPV16 E6, which blocks apoptosis by inactivation of p53, HPV16 E5 protects cells from apoptosis by enhancing the PI3K-Akt and ERK1/2 MAPK signal pathways.
Links	PubMed PMC135706
Keywords	Apoptosis; Cell Survival; Down-Regulation; Epidermal Growth Factor/physiology; Humans; Keratinocytes/radiation effects; Keratinocytes/virology; Oncogene Proteins, Viral/pharmacology; Papillomaviridae; Protein-Serine-Threonine Kinases; Proto-Oncogene Proteins/metabolism; Proto-Oncogene Proteins c-akt; Receptor, Epidermal Growth Factor/metabolism; Signal Transduction; Ultraviolet Rays
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HPV16:VE5		GO:0033668: negative regulation by symbiont of host apoptotic process	ECO:0000315:		P		Figure 2 shows a TUNNEL in parts A and B where E2 has kept HFKs from going under apoptosis after being exposed to UV. L(16E5)SN-infected keratinocytes were exposed to 0 (A) and 400 (B) J of UV light, the cells were stained with DAPI. this happens by E5 enhancing EGFR activation.	complete CACAO 6500
HPV16:VE5	involved_in	GO:0033668: negative regulation by symbiont of host apoptotic process	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

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