TMC8

Abstract: Summary: Infections by human papillomaviruses (HPVs) are the most frequently occurring sexually transmitted diseases. The crucial role of genital oncogenic HPV in cervical carcinoma development is now well established. In contrast, the role of cutaneous HPV in skin cancer development remains a matter of debate. Cutaneous beta-HPV strains show an amazing ubiquity. The fact that a few oncogenic genotypes cause cancers in patients suffering from epidermodysplasia verruciformis is in sharp contrast to the unapparent course of infection in the general population. Our recent investigations revealed that a natural barrier exists in humans, which protects them against infection with these papillomaviruses. A central role in the function of this HPV-specific barrier is played by a complex of the zinc-transporting proteins EVER1, EVER2, and ZnT-1, which maintain cellular zinc homeostasis. Apparently, the deregulation of the cellular zinc balance emerges as an important step in the life cycles not only of cutaneous but also of genital HPVs, although the latter viruses have developed a mechanism by which they can break the barrier and impose a zinc imbalance. Herein, we present a previously unpublished list of the cellular partners of EVER proteins, which points to future directions concerning investigations of the mechanisms of action of the EVER/ZnT-1 complex. We also present a general overview of the pathogenesis of HPV infections, taking into account the latest discoveries regarding the role of cellular zinc homeostasis in the HPV life cycle. We propose a potential model for the mechanism of function of the anti-HPV barrier.

Abstract: Epidermodysplasia verruciformis (EV) is a rare, autosomal recessive genodermatosis associated with a high risk of skin carcinoma (MIM 226400). EV is characterized by the abnormal susceptibility of otherwise healthy patients to infection by specific, weakly virulent human papillomaviruses (HPVs), including the potentially oncogenic HPV-5. Inactivating mutations in either of the related EVER1/TMC6 and EVER2/TMC8 genes cause most EV cases. New insights in EV pathogenesis have been gained from the following recent observations: (1) EV-specific HPVs (betapapillomaviruses) are defective for an important growth-promoting function encoded by an E5/E8 gene present in other HPVs, and inactivation of EVER proteins may compensate for the missing viral function; (2) the transmembrane viral E5/E8 and cellular EVER proteins interact both with the zinc transporter ZnT1, and are likely to modulate zinc homeostasis. EV may thus represent a primary deficiency in intrinsic, constitutive immunity to betapapillomaviruses, or constitute a primary deficiency in innate immunity (or both). Keratinocytes, the home cells of HPVs, are likely to play a central role in both cases. An important issue is to establish which cellular genes involved in intrinsic and innate antiviral responses play a part in the outcome of infections with other HPV types, such as genital oncogenic HPVs.

Abstract: † We describe a family with typical epidermodysplasia verruciformis (EV) in which only male members are affected. Whereas none of the index patient's ten children have EV, four of eight grandsons born to his daughters have inherited the disorder. All are infected with human papillomavirus (HPV) 3 and HPV 8. The inheritance in this kindred most likely results from an X-linked recessive genetic defect. Since other kindreds have been described with autosomal inheritance, this novel inheritance pattern suggests that the persistent high clinical susceptibility to HPV infection characteristic of EV may result from defects in either of at least two different genetic loci, one of which may be located on the X chromosome. (Arch Dermatol1985;121:864-868)