scholarly journals Endoplasmic Reticulum-Localized Human Papillomavirus Type 16 E5 Protein Alters Endosomal pH but Not trans-Golgi pH

2005 ◽  
Vol 79 (9) ◽  
pp. 5839-5846 ◽  
Author(s):  
Gary L. Disbrow ◽  
John A. Hanover ◽  
Richard Schlegel
Keyword(s):  
Endoplasmic Reticulum ◽  
Human Papillomavirus ◽  
Human Keratinocytes ◽  
Hpv 16 ◽  
Human Papillomavirus Type 16 ◽  
Endosomal Acidification ◽  
E5 Protein ◽  
Normal Expression ◽  
Intracellular Compartments ◽  
Endosomal Ph

ABSTRACT The human papillomavirus type 16 (HPV-16) E5 protein is a small, hydrophobic polypeptide that is expressed in virus-infected keratinocytes and alters receptor signaling pathways, apoptotic responses, and endosomal pH. Despite its ability to inhibit endosomal acidification, the HPV-16 E5 protein is found predominantly in the endoplasmic reticulum (ER), suggesting that its effect may be indirect and perhaps global. To determine whether E5 alters the pHs of additional intracellular compartments, we transduced human keratinocytes with a codon-optimized E5 vector and then quantified endosomal and trans-Golgi pHs using sensitive, compartment-specific, ratiometric pHluorin constructs. E5 protein increased endosomal pH from 5.9 to 6.9 but did not affect the normal trans-Golgi pH of 6.3. Confirming the lack of alteration in trans-Golgi pH, we observed no alterations in the acidification-dependent processing of the proH3 protein. C-terminal deletions of E5, which retained normal expression and localization in the ER, were defective for endosomal alkalization. Thus, E5 does not uniformly alkalinize intracellular compartments, and its C-terminal 10 amino acids appear to mediate interactions with critical ER targets that modulate proton pump function and/or localization.

scholarly journals The Human Papillomavirus Type 16 E5 Protein Impairs TRAIL- and FasL-Mediated Apoptosis in HaCaT Cells by Different Mechanisms

2002 ◽  
Vol 76 (23) ◽  
pp. 12162-12172 ◽  
Author(s):  
Kirsten Kabsch ◽  
Angel Alonso
Keyword(s):  
Human Papillomavirus ◽  
Fas Ligand ◽  
Human Keratinocytes ◽  
Fibroblast Cell ◽  
Mouse Fibroblast ◽  
Hpv 16 ◽  
Human Papillomavirus Type 16 ◽  
Trail Receptors ◽  
E5 Protein ◽  
Induced Apoptosis

ABSTRACT The effect of the human papillomavirus type 16 (HPV-16) E5 protein on apoptosis was investigated by using the polyclonal HaCaT-cell lines stably transfected either with E5 (HaCaT/E5) or the empty vector (HaCaT/pMSG) as reference. Apoptosis was triggered either by Fas ligand (FasL) or by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and was monitored by detection of cleavage of procaspase-8 and procaspase-3, as well as their substrate poly(ADP-ribose) polymerase (PARP). In contrast to the HaCaT/pMSG control cells we found that apoptosis induced by either of the two ligands is strongly suppressed in the E5-expressing keratinocytes. Fas expression is reduced by about a factor of two in HaCaT/E5 cells, which could be part of the mechanisms that protect the cells from FasL-induced apoptosis. For the TRAIL receptors, no such downregulation was observed. Here, E5 impairs the formation of the death-inducing signaling complex triggered by TRAIL. Apparently, E5 employs different mechanisms to inhibit death receptor signaling. This effect is not restricted to HaCaT/E5 cells since we found that the mouse fibroblast cell line A31-E5 is protected from TRAIL-induced apoptosis, as well but not the E5-lacking control cells A31-Neo. However, no such protection was observed upon FasL-induced apoptosis. Presumably, some of the antiapoptotic mechanisms employed by E5 of the human pathogenic HPV-16 are cell type specific. We propose that inhibition of ligand-mediated apoptosis in human keratinocytes is a primary function of the HPV-16 E5 protein needed to prevent apoptosis at early stages of viral infection.

scholarly journals Cytotoxic T-Lymphocyte Responses to Human Papillomavirus Type 16 E5 and E7 Proteins and HLA-A*0201-Restricted T-Cell Peptides in Cervical Cancer Patients

2007 ◽  
Vol 81 (6) ◽  
pp. 2869-2879 ◽  
Author(s):  
Dai-Wei Liu ◽  
Yuh-Cheng Yang ◽  
Ho-Fan Lin ◽  
Mei-Fang Lin ◽  
Ya-Wen Cheng ◽  
...  
Keyword(s):  
Cervical Cancer ◽  
Human Papillomavirus ◽  
T Cell ◽  
Cancer Patients ◽  
T Lymphocyte ◽  
Cytotoxic T Lymphocyte ◽  
Hpv 16 ◽  
Human Papillomavirus Type 16 ◽  
E5 Protein ◽  
E7 Proteins

ABSTRACT Previously, we found that human papillomavirus type 16 (HPV-16) E5 protein is a tumor rejection antigen and can induce cytotoxic T-lymphocyte (CTL) activity. Therefore, in this study, human leukocyte antigen A*0201 (HLA-A*0201)-restricted human CTL epitopes of HPV-16 E5 protein were identified using a bioinformatics approach, and the abilities of these predicted peptides to induce an immune response in HLA-A*0201 transgenic mice were confirmed by assaying E5-specific CTLs and in vitro-generated CTLs from normal peripheral blood T lymphocytes of HLA-A2-positive human donors. Second, the CTL responses to HLA-A*0201 CTL epitopes (E5 63-71 and E7 11-20) were examined in HPV-16-infected patients with HLA-A2. Third, the effect of HLA-A-type alleles on CTL activities in response to the entire E5 and E7 proteins was examined in cervical cancer patients. E5 and E7 peptides (but not the whole proteins) stimulated E5- and E7-specific CTL recall responses in HPV-16- and HLA-A2-positive cervical cancer patients, and HPV-16 E5 and E7 proteins stimulated naïve T cells in HPV-16-negative cervical cancer patients with HLA-A11 and -A24 haplotypes. In summary, this is the first demonstration that E5 63-71 is an HLA-A*0201-restricted T-cell epitope of HPV-16 E5.

scholarly journals Induction of CD8 T Cells by Vaccination with Recombinant Adenovirus Expressing Human Papillomavirus Type 16 E5 Gene Reduces Tumor Growth

2000 ◽  
Vol 74 (19) ◽  
pp. 9083-9089 ◽  
Author(s):  
Dai-Wei Liu ◽  
Yeou-Ping Tsao ◽  
Chang-Hsun Hsieh ◽  
Jer-Tsong Hsieh ◽  
John T. Kung ◽  
...  
Keyword(s):  
T Cells ◽  
Human Papillomavirus ◽  
Cd8 T Cells ◽  
Recombinant Adenovirus ◽  
Tumor Vaccine ◽  
Tumor Rejection ◽  
Hpv 16 ◽  
Human Papillomavirus Type 16 ◽  
E5 Protein ◽  
Tumor Protection

ABSTRACT The potential of the E5 protein as a tumor vaccine candidate has not been explored yet. In this study, we evaluate the human papillomavirus type 16 (HPV-16) E5 protein delivered by an adenovirus vector as a tumor vaccine for cervical lesions. The results demonstrate that a single intramuscular injection of a recombinant adenovirus carrying the HPV-16 E5 gene into syngeneic animals can reduce the growth of tumors which contain E5 gene expression. Moreover, the E5 vaccine-induced tumor protection occurs through CD8 T cells but not through CD4 T cells in in vitro assays. In addition, our studies using knockout mice with distinct T-cell deficiencies confirm that cytotoxic T-lymphocyte-induced tumor protection is CD8 dependent but CD4 independent. Hence, HPV-16 E5 can be regarded as a tumor rejection antigen.

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