EVER proteins, key elements of the natural anti-human papillomavirus barrier, are regulated upon T-cell activation.

Maciej Lazarczyk,Cécile Dalard,Roland S Liblau,Béatrice Pignolet,Francoise Vuillier,Loïc Dupre,Michel Favre,Myriam Hayder,Slawomir Majewski

doi:10.1371/journal.pone.0039995

Abstract

Human papillomaviruses (HPV) cause a variety of mucosal and skin lesions ranging from benign proliferations to invasive carcinomas. The clinical manifestations of infection are determined by host-related factors that define the natural anti-HPV barrier. Key elements of this barrier are the EVER1 and EVER2 proteins, as deficiency in either one of the EVER proteins leads to Epidermodysplasia Verruciformis (EV), a genodermatosis associated with HPV-induced skin carcinoma. Although EVERs have been shown to regulate zinc homeostasis in keratinocytes, their expression and function in other cell types that may participate to the anti-HPV barrier remain to be investigated. In this work, we demonstrate that EVER genes are expressed in different tissues, and most notably in lymphocytes. Interestingly, in contrast to the skin, where EVER2 transcripts are hardly detectable, EVER genes are both abundantly expressed in murine and human T cells. Activation of CD4+ and CD8+ T cells via the TCR triggers a rapid and profound decrease in EVER expression, accompanied by an accumulation of free Zn2+ ions. Thus, EVER proteins may be involved in the regulation of cellular zinc homeostasis in lymphocytes. Consistent with this hypothesis, we show that the concentration of Zn2+ ions is elevated in lymphoblastoid cells or primary T cells from EVER2-deficient patients. Interestingly, we also show that Zn2+ excess blocks T-cell activation and proliferation. Therefore, EVER proteins appear as key components of the activation-dependent regulation of Zn2+ concentration in T cells. However, the impact of EVER-deficiency in T cells on EV pathogenesis remains to be elucidated.

Highlights

Papillomaviruses are widespread infectious agents, transmitted by sexual or cutaneous contacts
We have shown that EVER1/TMC6 and EVER2/TMC8 proteins are located in the endoplasmic reticulum of keratinocytes, where they form a complex with zinc transporter-1 (ZnT-1), thereby controlling the cellular zinc balance [11]
Using both classical RT-PCR and quantitative RT-PCR, we observed that EVER1 and EVER2 were clearly expressed in spleen and thymus (Fig. 1A), as well as in purified murine (Fig. 1B) and human (Fig. S1A, B) lymphocyte populations

Summary

Introduction

Papillomaviruses are widespread infectious agents, transmitted by sexual or cutaneous contacts. Activation of purified TCR-transgenic CD8+ T cells with syngeneic antigen-presenting cells loaded with the cognate HA512– 520 peptide was associated with a clear and long-lasting decrease in the expression of both EVER genes (Fig. 2E).

Results

Conclusion