Intermediate Heparan Sulfate Binding During HPV-16 Infection in HaCaTs

Abstract

Human papillomavirus (HPV) is the most prevalent sexually transmitted disease in the United States, and can cause cancer with persistent infection. The most common cancer caused by HPV is cervical carcinoma with an average of 12,000 cases reported every year in the U.S. Worldwide, over 500,000 cases of cervical cancer are reported yearly with over 250,000 deaths attributed to the disease. Although much is known about the serious health risks associated with HPV infection, there is still much to be discovered about how HPV binds and enters target cells. Understanding how HPV infects will lead to strategies and therapies for reducing the number of infections and HPV-related diseases, including cancers. The HPV viral particle is composed of two viral proteins, L1 and L2. Data suggest that binding of the viral capsid to cells is dependent on the L1 protein. We hypothesize that this initial binding to a heparan sulfate is composed of two independent events: the first results in a structural change that exposes a hidden portion of the L1 protein leading to a second binding event on the heparan sulfate. Our experiments tested if this “hidden” portion of L1 is necessary for infection and explored the nature of this binding. We generated a peptide with the sequence of the “hidden” portion of L1. Infection of HaCaT cells in the presence of this peptide is highly reduced. Our results suggest that the binding of the L1 C-terminal domain is dependent on amino acid sequence, and is necessary for infection.

Superinfection Exclusion between Two High-Risk Human Papillomavirus Types during a Coinfection

“…However, the exact mechanism is unclear. A multitude of cellular receptors have been identified for HPV, including HSPGs (57,58,66,88,101), integrin ␣6/␤4 (61-65), growth factor receptors such as epidermal growth factor receptor (EGFR) and keratinocyte growth factor receptor (KGFR) (66), annexin-A2 (106), and the tetraspanin CD151 (107,108). Of these receptors, attachment to ␣6/␤4 and EGFR/KGFR has been shown to induce signaling cascades, which could lead to changes in the cell surface to prevent the attachment of additional HPV virions.…”

“…Microabrasions in the tissue allow the virus to gain access to basal cells (53), where the virus can bind to the extracellular matrix (ECM) and/or the cell surface via L1 (54)(55)(56)(57)(58)(59). Entry has been shown to involve multiple receptors/coreceptors, including heparan sulfate (HS) (54, [57][58][59][60], ␣6␤4 integrin (61)(62)(63)(64)(65), growth factor receptors (66,67), and annexin-A2 (67)(68)(69). Upon infection, the genome is maintained within the basal cells (70).…”

Human Papillomavirus Induced Transformation in Cervical and Head and Neck Cancers

“…Once there, it will utilize the host cell replication machinery to initiate viral DNA replication [ 35 ]. Our understanding of the initial HPV infection process including viral attachment and entry remains incomplete, but interactions with heparan sulfate on the cell surface have been implicated [ 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. The HPV life cycle is highly organized, geographically as well as functionally, around the cellular differentiation program [ 43 , 44 ].…”

Papillomavirus Infectious Pathways: A Comparison of Systems

“…This binding event induces a conformational change allowing for the L2 N-terminus to be cleaved by a proprotein convertase (PC) such as furin or PC5/6 [ 68 , 69 ]. Additionally, these conformational changes may allow for interactions with secondary HS sites on the capsid, transfer the virion to an uptake receptor or receptor complex, and allow for exposure of hidden epitopes that may be important for the interaction with other cellular proteins in the entry process [ 69 , 70 , 71 ]. The involvement of GAGs as an attachment receptor was first demonstrated utilizing HPV11 L1 only VLPs and HaCaT cells.…”