Human papillomaviruses bind a basal extracellular matrix component secreted by keratinocytes which is distinct from a membrane-associated receptor

Abstract

Human papillomaviruses (HPVs) have previously been shown to adsorb to cultured cells via membrane-associated heparan sulfate (HS) and alpha6 integrin. We demonstrate that cultured keratinocytes uniquely secrete a component into the basal extracellular matrix (ECM) which can function to adsorb HPV particles which can then be internalized by adherent cells. This uncharacterized basal ECM adsorption receptor was secreted by normal human epidermal keratinocytes (NHEK) and by each of the four keratinocyte-derived cell lines we examined, but not by non-keratinocyte cell lines. Multiple HPV types bound preferentially to this keratinocyte-specific receptor over the membrane-associated receptor, and binding to the basal ECM adsorption receptor was refractory to inhibition by heparin. Like the membrane-associated receptor, this basal ECM component was functional as an adsorption receptor in our in vitro infection model using HPV-11. Unlike particle adsorption, however, successful infection with HPV-11 virions remained sensitive to the pretreatment of virions with heparin. The secreted basal ECM receptor did not colocalize with antibodies against HS, perlecan, or alpha6 integrin, but colocalized with antibody against laminin-5, a marker of keratinocyte ECM and an abundant component of the basement membrane in mucosa and skin. These findings suggest a model for natural infections in which HPV virions, nonspecifically adsorbed to HS on suprabasal keratinocytes throughout an epithelial wound, might be transferred to mitotically active migrating keratinocytes via an intermediate association with the ECM secreted by these cells as they reestablish the basement membrane.

Differential binding patterns to host cells associated with particles of several human alphapapillomavirus types

“…In these studies, which were focused on the primary binding events rather than uptake/infection, we found that VLPs and PsV particles showed similar binding patterns to those found previously for HPV11 L1 VLPs, HPV11 PsVs and native HPV11 virions (Culp et al, 2006a). The data suggest that the four types of VLP capsid tested in this study showed qualitative differences in binding to HS, ECM and purified LN5, although direct quantification of K d values for binding to purified individual components awaits additional experimentation.…”

“…The role of HS receptors in vivo has been examined recently in a mouse vaginal infection model using PsVs of several HPV types and, interestingly, preferential initial binding of HPV PsVs to basement membrane (BM) components was demonstrated (Johnson et al, 2009;Roberts et al, 2007). In addition, preferential binding of several HPV VLPs to the BM in human cervical tissue sections was reported previously (Culp et al, 2006a). These recent studies support an important role for BM/ECM components in the initial binding and uptake of HPV capsids in vivo, as a reservoir for uptake of virions via cellular filopodia (Schelhaas et al, 2008;Smith et al, 2008), and support a role for the importance of ECM-binding events that can be observed in vitro when keratinocyte cell lines representing the natural host cell are used.…”

“…Earlier studies on HPV binding and infection focused predominantly on one HPV type and one cell type to identify papillomavirus binding receptors for HS, a-6 integrin, syndecan-1 and LN5 (Culp et al, 2006a;Evander et al, 1997;Joyce et al, 1999;Patterson et al, 2005;ShaftiKeramat et al, 2003). These earlier studies led investigators to propose general mechanisms for HPV infection that should be applicable to all HPV types.…”

“…Previous research from our laboratory also established a direct binding interaction between HPV11 and laminin 5 (LN5), a key extracellular matrix (ECM) component involved in hemidesmosome formation. We hypothesized that HPV11 virions utilize LN5 as a transreceptor for proper targeting to basal keratinocytes migrating to the site of injury (Culp et al, 2006a).…”

Incoming human papillomavirus type 16 genome resides in a vesicular compartment throughout mitosis

“…Following primary attachment and internalization, acidification of early endosomes triggers capsid disassembly (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). Host cell cyclophilins release the majority of L1 from the L2 protein, which remains in complex with the viral genome (2,23,24).…”