The endocytic trafficking pathway of oncogenic papillomaviruses

Correlation between breast cancer and human papillomavirus (HPV) infection

Breast cancer (BC), the most common malignant tumor in women worldwide, has been increasing in incidence and mortality year by year. While significant progress has been made in understanding the pathogenesis of breast cancer, certain aspects remain under investigation. Human papillomavirus (HPV) is known to be closely associated with a variety of cancers, including cervical, vulvar, anal, and head and neck cancers. It is important to note that while HPV is associated with the mentioned cancers, its direct association with breast cancer remains a topic of debate and research. In this paper, we review the research progress on the correlation between breast cancer and HPV infection, and put forward the problems in the current research. This review aims to shed light on the current understanding and controversies surrounding the correlation between HPV infection and breast cancer, providing insights for future research aimed at enhancing prevention and treatment strategies.

RNF149 negatively regulates LPS/TLR4 signal transduction by ubiquitination-mediated CD63 degradation

This study aims to investigate the role of RNF149 and tetraspanin CD63 in lipopolysaccharide/Toll-like receptor 4 (LPS/TLR4) signal transduction. TNF-α was assessed using enzyme-linked immunosorbent assay. The distribution of TLR4 was examined through flow cytometry after CD63 knockdown. Real-time polymerase chain reaction was used to analyze the expression of the target genes RNF149 and CD63 under different conditions. Western blotting was employed to detect gene expression, while immunoprecipitation and confocal microscopy were used to evaluate protein interactions. Transcriptome array data from stimulated monocytes (GSE7547) was obtained from GEO and subjected to bioinformatic analysis. It is suggested that CD63 may serve as a substrate of RNF149, with RNF149 capable of directly interacting with CD63. RNF149 degrades CD63 through covalent modification of CD63 at lysine 29 of the ubiquitin monomer, leading to the formation of a multiubiquitin chain. Both RNF149 and CD63 interact with TLR4, with CD63 promoting LPS/TLR4 signaling and RNF149 inhibits it. CD63 does not impact the distribution of TLR4 on the cell surface and does not directly interact with TIRAP, IRAK4, or TRAF6, but does interact with Myd88.RNF149 plays a negative regulatory role in LPS/TLR4 signal transduction by mediating ubiquitination-induced CD63 degradation.

A peptide derived from sorting nexin 1 inhibits HPV16 entry, retrograde trafficking, and L2 membrane spanning

High risk human papillomavirus (HPV) infection is responsible for 99 % of cervical cancers and 5 % of all human cancers worldwide. HPV infection requires the viral genome (vDNA) to gain access to nuclei of basal keratinocytes of epithelium. After virion endocytosis, the minor capsid protein L2 dictates the subcellular retrograde trafficking and nuclear localization of the vDNA during mitosis. Prior work identified a cell-permeable peptide termed SNX1.3, derived from the BAR domain of sorting nexin 1 (SNX1), that potently blocks the retrograde and nuclear trafficking of EGFR in triple negative breast cancer cells. Given the importance of EGFR and retrograde trafficking pathways in HPV16 infection, we set forth to study the effects of SNX1.3 within this context. SNX1.3 inhibited HPV16 infection by both delaying virion endocytosis, as well as potently blocking virion retrograde trafficking and Golgi localization. SNX1.3 had no effect on cell proliferation, nor did it affect post-Golgi trafficking of HPV16. Looking more directly at L2 function, SNX1.3 was found to impair membrane spanning of the minor capsid protein. Future work will focus on mechanistic studies of SNX1.3 inhibition, and the role of EGFR signaling and SNX1-mediated endosomal tubulation, cargo sorting, and retrograde trafficking in HPV infection.

A Peptide Derived from Sorting Nexin 1 Inhibits HPV16 Entry, Retrograde Trafficking, and L2 Membrane Spanning

High risk human papillomavirus (HPV) infection is responsible for 99% of cervical cancers and 5% of all human cancers worldwide. HPV infection requires the viral genome (vDNA) to gain access to nuclei of basal keratinocytes of epithelium. After virion endocytosis, the minor capsid protein L2 dictates the subcellular retrograde trafficking and nuclear localization of the vDNA during mitosis. Prior work identified a cell-permeable peptide termed SNX1.3, derived from the BAR domain of sorting nexin 1 (SNX1), that potently blocks the retrograde and nuclear trafficking of EGFR in triple negative breast cancer cells. Given the importance of EGFR and retrograde trafficking pathways in HPV16 infection, we set forth to study the effects of SNX1.3 within this context. SNX1.3 inhibited HPV16 infection by both delaying virion endocytosis, as well as potently blocking virion retrograde trafficking and Golgi localization. SNX1.3 had no effect on cell proliferation, nor did it affect post-Golgi trafficking of HPV16. Looking more directly at L2 function, SNX1.3 was found to impair membrane spanning of the minor capsid protein. Future work will focus on mechanistic studies of SNX1.3 inhibition, and the role of EGFR signaling and SNX1- mediated endosomal tubulation, cargo sorting, and retrograde trafficking in HPV infection.

Exploring the utility of FTS as a bonafide binding partner for EGFR: A potential drug target for cervical cancer

Establishment of human papilloma virus (HPV) infection and its progression to cervical cancer (CC) requires the participation of epidermal growth factor (EGF) receptor (EGFR) and fused toes homolog (FTS). This review is an attempt to understand the structure-function relationship between FTS and EGFR as a tool for the development of newer CC drugs. Motif analysis was performed using national center for biotechnology information (NCBI), kyoto encyclopedia of genes and genomes (KEGG), simple modular architecture research tool (SMART) and multiple expectation maximizations for motif elicitation (MEME) database. The secondary and tertiary structure prediction of FTS was performed using DISOPRED3 and threading assembly, respectively. A positive correlation was found between the transcript levels of FTS and EGFR. Amino acids responsible for interaction between EGFR and FTS were determined. The nine micro-RNAs (miRNAs) that regulates the expression of FTS were predicted using Network Analyst 3.0 database. hsa-miR-629-5p and hsa-miR-615-3p are identified as significant positive and negative regulators of FTS gene expression. This review opens up new avenues for the development of CC drugs which interfere with the interaction between FTS and EGFR.

Bombyx mori Tetraspanin A (BmTsp.A) is a facilitator in BmNPV invasion by regulating apoptosis

BmTsp.A (Bombyx mori Tetraspanin A) is one of the four transmembrane proteins which are capable to regulate multiple aspects of the immune response and are involved in various stages of viral invasion of the hosts. This study focused on the sequence features, analysis of expression pattern, as well as the effect of BmTsp.A on BmNPV (Bombyx mori nucleopolyhedrovirus) infection in the apoptotic pathway. BmTsp.A features the typical tetraspanins family, including four transmembrane domains and a major large extracellular loop domain. It is highly expressed specifically in the malpighian tubes, and its expression is increased by BmNPV induction for 48 h and 72 h. Overexpression and RNAi (RNA interference) mediated by siRNA reveal that BmTsp.A can promote the infection and replication of the virus. In addition, the overexpression of BmTsp.A regulates BmNPV-induced apoptosis, leading to changes in the expression of apoptosis-related genes and thus affecting viral proliferation. When subjected to stimulation by BmNPV infection, on the one hand, BmTsp.A inhibits Bmp53 through a Caspase-dependent pathway, which consequently promotes the expression of Bmbuffy, thereby activating BmICE to inhibit apoptosis and causing the promotion of viral proliferation. On the other hand, BmTsp.A inhibits the expression of BmPTEN and BmPkc through the phosphatidylinositol 3 kinase (PI3K)/protein kinaseB(AKT) signaling pathway, thus affecting the regulation of apoptosis. To summarize, our results demonstrate that BmTsp.A promotes viral infection and replication by inhibiting apoptosis, which is fundamental for understanding the pathogenesis of BmNPV and the immune defense mechanism of silkworm.

HPV-Associated Breast Cancer: Myth or Fact?

Some estimates place the proportion of human malignancies attributable to viruses at between 15 and 20 percent. Viruses including the human papillomavirus are considered an interesting but controversial etiological risk factor for breast cancer. HPV infection is anticipated to be an early trigger in breast cancer carcinogenesis, followed by cumulative alterations over time ("hit and run" mechanism) through synergy with other environmental factors. The association between HPV and breast cancer has not yet been verified. There are very conflicting data on the presence of HPV DNA in breast cancer samples, and we lack a clarified, exact mode of HPV transmission to the breast. In our review article we analyzed the up-to-date knowledge about the association of HPV and breast cancer. Furthermore, we summarized the available original research published since 2010. In conclusion, the complexity and inconsistency of the available results together with the relatively low prevalence of HPV infection requires extensive research with much larger studies and exact and unified diagnostic methods are required to better understand the role of the HPV in breast carcinogenesis.

Oral Papillomatosis: Its Relation with Human Papilloma Virus Infection and Local Immunity—An Update

Oral papilloma lesions may appear as a result of HPV infection, or not, and only special molecular methods could differentiate them. Low-risk and high-risk HPV types could induce oral HPV papillomatosis with different natural evolution, clearance and persistence mechanisms. The pathogenic mechanisms are based on the crosstalk between the oral epithelial and immune cells and this very efficient virus. HPV acts as a direct inducer in the process of transforming a benign lesion into a malignant one, the cancerization process being also debated in this paper. According to the degree of malignity, three types of papillomatous lesions can be described in the oral cavity: benign lesions, potential malign disorders and malignant lesions. The precise molecular diagnostic is important to identify the presence of various virus types and also the virus products responsible for its oncogenicity. An accurate diagnostic of oral papilloma can be established through a good knowledge of etiological and epidemiological factors, clinical examination and laboratory tests. This review intends to update the pathogenic mechanisms driving the macroscopic and histological features of oral papillomatosis having HPV infection as the main etiological factor, focusing on its interreference in the local immunity. In the absence of an accurate molecular diagnostic and knowledge of local immunological conditions, the therapeutic strategy could be difficult to decide.

Presence of Human Papillomavirus DNA in Malignant Neoplasia and Non-Malignant Breast Disease

Breast cancer is the leading cause of cancer death among women worldwide. Multiple extrinsic and intrinsic factors are associated with this disease’s development. Various research groups worldwide have reported the presence of human papillomavirus (HPV) DNA in samples of malignant breast tumors. Although its role in mammary carcinogenesis is not fully understood, it is known that the HPV genome, once inserted into host cells, has oncogenic capabilities. The present study aimed to detect the presence of HPV DNA in 116 breast tissue biopsies and classify them according to their histology. It was found that 50.9% of the breast biopsies analyzed were malignant neoplasms, of which 74.6% were histologically classified as infiltrating ductal carcinoma. In biopsies with non-malignant breast disease, fibroadenoma was the most common benign neoplasm (39.1%). Detection of HPV DNA was performed through nested PCR using the external primer MY09/11 and the internal primer GP5+/6+. A hybridization assay genotyped HPV. HPV DNA was identified in 20.3% (12/59) of malignant neoplasms and 35% non-malignant breast disease (16/46). It was also detected in 27.3% (3/11) of breast tissue biopsies without alteration. However, there are no statistically significant differences between these groups and the existence of HPV DNA (p = 0.2521). Its presence was more frequent in non-malignant alterations than in malignant neoplasias. The most frequent genotypes in the HPV-positive samples were low-risk (LR) HPV-42 followed by high-risk (HR) HPV-31.

HPV16 Entry into Epithelial Cells: Running a Gauntlet

During initial infection, human papillomaviruses (HPV) take an unusual trafficking pathway through their host cell. It begins with a long period on the cell surface, during which the capsid is primed and a virus entry platform is formed. A specific type of clathrin-independent endocytosis and subsequent retrograde trafficking to the trans-Golgi network follow this. Cellular reorganization processes, which take place during mitosis, enable further virus transport and the establishment of infection while evading intrinsic cellular immune defenses. First, the fragmentation of the Golgi allows the release of membrane-encased virions, which are partially protected from cytoplasmic restriction factors. Second, the nuclear envelope breakdown opens the gate for these virus–vesicles to the cell nucleus. Third, the dis- and re-assembly of the PML nuclear bodies leads to the formation of modified virus-associated PML subnuclear structures, enabling viral transcription and replication. While remnants of the major capsid protein L1 and the viral DNA remain in a transport vesicle, the viral capsid protein L2 plays a crucial role during virus entry, as it adopts a membrane-spanning conformation for interaction with various cellular proteins to establish a successful infection. In this review, we follow the oncogenic HPV type 16 during its long journey into the nucleus, and contrast pro- and antiviral processes.

Endocytosis of abiotic nanomaterials and nanobiovectors: Inhibition of membrane trafficking

Humans are exposed to nanoscopical nanobiovectors (e.g. coronavirus SARS-CoV-2) as well as abiotic metal/carbon-based nanomaterials that enter cells serendipitously or intentionally. Understanding the interactions of cell membranes with these abiotic and biotic nanostructures will facilitate scientists to design better functional nanomaterials for biomedical applications. Such knowledge will also provide important clues for the control of viral infections and the treatment of virus-induced infectious diseases. In the present review, the mechanisms of endocytosis are reviewed in the context of how nanomaterials are uptaken into cells. This is followed by a detailed discussion of the attributes of man-made nanomaterials (e.g. size, shape, surface functional groups and elasticity) that affect endocytosis, as well as the different human cell types that participate in the endocytosis of nanomaterials. Readers are then introduced to the concept of viruses as nature-derived nanoparticles. The mechanisms in which different classes of viruses interact with various cell types to gain entry into the human body are reviewed with examples published over the last five years. These basic tenets will enable the avid reader to design advanced drug delivery and gene transfer nanoplatforms that harness the knowledge acquired from endocytosis to improve their biomedical efficacy. The review winds up with a discussion on the hurdles to be addressed in mimicking the natural mechanisms of endocytosis in nanomaterials design.

Recent Advances in Our Understanding of the Infectious Entry Pathway of Human Papillomavirus Type 16

Papillomaviruses are a diverse viral species, but several types such as HPV16 are given special attention due to their contribution towards the pathogenesis of several major cancers. In this review, we will summarize how the knowledge of HPV16 entry has expanded since the last comprehensive HPV16 entry review our lab published in 2017.

Advances in Targeting HPV Infection as Potential Alternative Prophylactic Means

Infection by oncogenic human papillomavirus (HPV) is the primary cause of cervical cancer and other anogenital cancers. The majority of cervical cancer cases occur in low- and middle- income countries (LMIC). Concurrent infection with Human Immunodeficiency Virus (HIV) further increases the risk of HPV infection and exacerbates disease onset and progression. Highly effective prophylactic vaccines do exist to combat HPV infection with the most common oncogenic types, but the accessibility to these in LMIC is severely limited due to cost, difficulties in accessing the target population, cultural issues, and maintenance of a cold chain. Alternative preventive measures against HPV infection that are more accessible and affordable are therefore also needed to control cervical cancer risk. There are several efforts in identifying such alternative prophylactics which target key molecules involved in early HPV infection events. This review summarizes the current knowledge of the initial steps in HPV infection, from host cell-surface engagement to cellular trafficking of the viral genome before arrival in the nucleus. The key molecules that can be potentially targeted are highlighted, and a discussion on their applicability as alternative preventive means against HPV infection, with a focus on LMIC, is presented.

ANXA2 is a potential marker for the diagnosis of human cervical cancer

Aim: The aim is to study ANXA2 biomarkers for early diagnosis of cervical cancer. Materials & methods: The study used bioinformatics analysis and experimental verification of ANXA2 expression in cervical cancer. Results:ANXA2 expression was higher in cancer tissues than in non-cancer tissues (p = 0.002). ANXA2 was expressed in cell membranes of non-cancer tissues, whereas in cancer tissues it was expressed in both the cell membranes and the cytoplasm. Moreover, ANXA2 expression was more pronounced in squamous cell carcinomas. ANXA2 expression decreased overall survival of patients, and the data suggested that protein expression was associated with invasion and migration of tumors. Conclusion:ANXA2 has high specificity and sensitivity as a detection marker for cervical cancer and can assist in the diagnosis of cervical cancer.

Mechanistic Approaches of Internalization, Subcellular Trafficking, and Cytotoxicity of Nanoparticles for Targeting the Small Intestine

Targeting the small intestine employing nanotechnology has proved to be a more effective way for site-specific drug delivery. The drug targeting to the small intestine can be achieved via nanoparticles for its optimum bioavailability within the systemic circulation. The small intestine is a remarkable candidate for localized drug delivery. The intestine has its unique properties. It has a less harsh environment than the stomach, provides comparatively more retention time, and possesses a greater surface area than other parts of the gastrointestinal tract. This review focuses on elaborating the intestinal barriers and approaches to overcome these barriers for internalizing nanoparticles and adopting different cellular trafficking pathways. We have discussed various factors that contribute to nanocarriers' cellular uptake, including their surface chemistry, surface morphology, and functionalization of nanoparticles. Furthermore, the fate of nanoparticles after their uptake at cellular and subcellular levels is also briefly explained. Finally, we have delineated the strategies that are adopted to determine the cytotoxicity of nanoparticles.

Theta-Defensins Inhibit High-Risk Human Papillomavirus Infection Through Charge-Driven Capsid Clustering

Persistent infection with high-risk human papillomavirus (hrHPV) genotypes results in a large number of anogenital and head and neck cancers worldwide. Although prophylactic vaccination coverage has improved, there remains a need to develop methods that inhibit viral transmission toward preventing the spread of HPV-driven disease. Defensins are a class of innate immune effector peptides that function to protect hosts from infection by pathogens such as viruses and bacteria. Previous work utilizing α and β defensins from humans has demonstrated that the α-defensin HD5 is effective at inhibiting the most common high-risk genotype, HPV16. A third class of defensin that has yet to be explored are θ-defensins: small, 18-amino acid cyclic peptides found in old-world monkeys whose unique structure makes them both highly cationic and resistant to degradation. Here we show that the prototype θ-defensin, rhesus theta defensin 1, inhibits hrHPV infection through a mechanism involving capsid clustering that inhibits virions from binding to cell surface receptor complexes.

Vesicular trafficking permits evasion of cGAS/STING surveillance during initial human papillomavirus infection

Oncogenic human papillomaviruses (HPVs) replicate in differentiating epithelium, causing 5% of cancers worldwide. Like most other DNA viruses, HPV infection initiates after trafficking viral genome (vDNA) to host cell nuclei. Cells possess innate surveillance pathways to detect microbial components or physiological stresses often associated with microbial infections. One of these pathways, cGAS/STING, induces IRF3-dependent antiviral interferon (IFN) responses upon detection of cytosolic DNA. Virion-associated vDNA can activate cGAS/STING during initial viral entry and uncoating/trafficking, and thus cGAS/STING is an obstacle to many DNA viruses. HPV has a unique vesicular trafficking pathway compared to many other DNA viruses. As the capsid uncoats within acidic endosomal compartments, minor capsid protein L2 protrudes across vesicular membranes to facilitate transport of vDNA to the Golgi. L2/vDNA resides within the Golgi lumen until G2/M, whereupon vesicular L2/vDNA traffics along spindle microtubules, tethering to chromosomes to access daughter cell nuclei. L2/vDNA-containing vesicles likely remain intact until G1, following nuclear envelope reformation. We hypothesize that this unique vesicular trafficking protects HPV from cGAS/STING surveillance. Here, we investigate cGAS/STING responses to HPV infection. DNA transfection resulted in acute cGAS/STING activation and downstream IFN responses. In contrast, HPV infection elicited minimal cGAS/STING and IFN responses. To determine the role of vesicular trafficking in cGAS/STING evasion, we forced premature viral penetration of vesicular membranes with membrane-perturbing cationic lipids. Such treatment renders a non-infectious trafficking-defective mutant HPV infectious, yet susceptible to cGAS/STING detection. Overall, HPV evades cGAS/STING by its unique subcellular trafficking, a property that may contribute to establishment of infection.

Epidermal Growth Factor Receptor and Abl2 Kinase Regulate Distinct Steps of Human Papillomavirus 16 Endocytosis

Human papillomavirus 16 (HPV16), the leading cause of cervical cancer, exploits a novel endocytic pathway during host cell entry. This mechanism shares many requirements with macropinocytosis but differs in the mode of vesicle formation. Previous work indicated a role of the epidermal growth factor receptor (EGFR) in HPV16 endocytosis. However, the functional outcome of EGFR signaling and its downstream targets during HPV16 uptake are not well characterized. Here, we analyzed the functional importance of signal transduction via EGFR and its downstream effectors for endocytosis of HPV16. Our findings indicate two phases of EGFR signaling as follows: a-likely dispensable-transient activation with or shortly after cell binding and signaling required throughout the process of asynchronous internalization of HPV16. Interestingly, EGFR inhibition interfered with virus internalization and strongly reduced the number of endocytic pits, suggesting a role for EGFR signaling in the induction of HPV16 endocytosis. Moreover, we identified the Src-related kinase Abl2 as a novel regulator of virus uptake. Inhibition of Abl2 resulted in an accumulation of misshaped endocytic pits, indicating Abl2's importance for endocytic vesicle maturation. Since Abl2 rather than Src, a regulator of membrane ruffling during macropinocytosis, mediated downstream signaling of EGFR, we propose that the selective effector targeting downstream of EGFR determines whether HPV16 endocytosis or macropinocytosis is induced.IMPORTANCE Human papillomaviruses are small, nonenveloped DNA viruses that infect skin and mucosa. The so-called high-risk HPVs (e.g., HPV16, HPV18, HPV31) have transforming potential and are associated with various anogenital and oropharyngeal tumors. These viruses enter host cells by a novel endocytic pathway with unknown cellular function. To date, it is unclear how endocytic vesicle formation occurs mechanistically. Here, we addressed the role of epidermal growth factor receptor signaling, which has previously been implicated in HPV16 endocytosis and identified the kinase Abl2 as a novel regulator of virus uptake. Since other viruses, such as influenza A virus and lymphocytic choriomeningitis virus, possibly make use of related mechanisms, our findings shed light on fundamental strategies of virus entry and may in turn help to develop new host cell-targeted antiviral strategies.

Papillomaviruses Go Retro

Human papillomaviruses are important pathogens responsible for approximately 5% of cancer as well as other important human diseases, but many aspects of the papillomavirus life cycle are poorly understood. To undergo genome replication, HPV DNA must traffic from the cell surface to the nucleus. Recent findings have revolutionized our understanding of HPV entry, showing that it requires numerous cellular proteins and proceeds via a series of intracellular membrane-bound vesicles that comprise the retrograde transport pathway. This paper reviews the evidence supporting this unique entry mechanism with a focus on the crucial step by which the incoming virus particle is transferred from the endosome into the retrograde pathway. This new understanding provides novel insights into basic cellular biology and suggests novel rational approaches to inhibit HPV infection.

Anatomy of a viral entry platform differentially functionalized by integrins α3 and α6

During cell invasion, human papillomaviruses use large CD151 patches on the cell surface. Here, we studied whether these patches are defined architectures with features for virus binding and/or internalization. Super-resolution microscopy reveals that the patches are assemblies of closely associated nanoclusters of CD151, integrin α3 and integrin α6. Integrin α6 is required for virus attachment and integrin α3 for endocytosis. We propose that CD151 organizes viral entry platforms with different types of integrin clusters for different functionalities. Since numerous viruses use tetraspanin patches, we speculate that this building principle is a blueprint for cell-surface architectures utilized by viral particles.

Tspan8-Tumor Extracellular Vesicle-Induced Endothelial Cell and Fibroblast Remodeling Relies on the Target Cell-Selective Response

Tumor cell-derived extracellular vesicles (TEX) expressing tetraspanin Tspan8-alpha4/beta1 support angiogenesis. Tspan8-alpha6/beta4 facilitates lung premetastatic niche establishment. TEX-promoted target reprogramming is still being disputed, we explored rat endothelial cell (EC) and lung fibroblast (Fb) mRNA and miRNA profile changes after coculture with TEX. TEX were derived from non-metastatic BSp73AS (AS) or metastatic BSp73ASML (ASML) rat tumor lines transfected with Tspan8 (AS-Tspan8) or Tspan8-shRNA (ASML-Tspan8kd). mRNA was analyzed by deep sequencing and miRNA by array analysis of EC and Fb before and after coculture with TEX. EC and Fb responded more vigorously to AS-Tspan8- than AS-TEX. Though EC and Fb responses differed, both cell lines predominantly responded to membrane receptor activation with upregulation and activation of signaling molecules and transcription factors. Minor TEX-initiated changes in the miRNA profile relied, at least partly, on long noncoding RNA (lncRNA) that also affected chromosome organization and mRNA processing. These analyses uncovered three important points. TEX activate target cell autonomous programs. Responses are initiated by TEX targeting units and are target cell-specific. The strong TEX-promoted lncRNA impact reflects lncRNA shuttling and location-dependent distinct activities. These informations urge for an in depth exploration on the mode of TEX-initiated target cell-specific remodeling including, as a major factor, lncRNA.

Glutathione contributes to efficient post-Golgi trafficking of incoming HPV16 genome

Human papillomavirus (HPV) is the most common sexually transmitted pathogen in the United States, causing 99% of cervical cancers and 5% of all human cancers worldwide. HPV infection requires transport of the viral genome (vDNA) into the nucleus of basal keratinocytes. During this process, minor capsid protein L2 facilitates subcellular retrograde trafficking of the vDNA from endosomes to the Golgi, and accumulation at host chromosomes during mitosis for nuclear retention and localization during interphase. Here we investigated the relationship between cellular glutathione (GSH) and HPV16 infection. siRNA knockdown of GSH biosynthetic enzymes results in a partial decrease of HPV16 infection. Likewise, infection of HPV16 in GSH depleted keratinocytes is inefficient, an effect that was not seen with adenoviral vectors. Analysis of trafficking revealed no defects in cellular binding, entry, furin cleavage of L2, or retrograde trafficking of HPV16, but GSH depletion hindered post-Golgi trafficking and translocation, decreasing nuclear accumulation of vDNA. Although precise mechanisms have yet to be defined, this work suggests that GSH is required for a specific post-Golgi trafficking step in HPV16 infection.

ADAM17-dependent signaling is required for oncogenic human papillomavirus entry platform assembly

Oncogenic human papillomaviruses (HPV) are small DNA viruses that infect keratinocytes. After HPV binding to cell surface receptors, a cascade of molecular interactions mediates the infectious cellular internalization of virus particles. Aside from the virus itself, important molecular players involved in virus entry include the tetraspanin CD151 and the epidermal growth factor receptor (EGFR). To date, it is unknown how these components are coordinated in space and time. Here, we studied plasma membrane dynamics of CD151 and EGFR and the HPV16 capsid during the early phase of infection. We find that the proteinase ADAM17 activates the extracellular signal-regulated kinases (ERK1/2) pathway by the shedding of growth factors which triggers the formation of an endocytic entry platform. Infectious endocytic entry platforms carrying virus particles consist of two-fold larger CD151 domains containing the EGFR. Our finding clearly dissects initial virus binding from ADAM17-dependent assembly of a HPV/CD151/EGFR entry platform.