Biological Activities of Papillomavirus E5 Proteins
Frank A. Suprynowicz, M. Saveria Campo and Richard Schlegel
from: Papillomavirus Research: From Natural History To Vaccines and Beyond (Edited by: M. Saveria Campo). Caister Academic Press, U.K. (2006)
This chapter discusses biological activities of the bovine papillomavirus type 1 E5 protein (BPV-1 E5), the closely-related E5 protein of bovine papillomavirus type 4 (BPV-4 E5) and the E5 protein of high-risk human papillomavirus type 16 (HPV-16 E5). BPV-1 E5 transforms fibroblasts by inducing constitutive, ligand-independent activation of the β-type platelet-derived growth factor receptor (PDGF-Rβ), and by constitutively activating c-Src and interfering with Golgi acidification independently of PDGF-Rβ signaling. BPV-4 E5 similarly transforms fibroblasts and disrupts gap junction-mediated intercellular communication. Both BPV proteins down-regulate surface expression of major histocompatibility complex (MHC) class I molecules, which should enhance the ability of infected cells to evade detection by the host immune system. HPV-16 E5 is only weakly oncogenic, but acts in a number of ways to increase the duration and scope of HPV-16 infections, which in turn may increase the probability of malignant progression. These actions include a reduction of MHC class I and class II surface expression, the disruption of gap junctional intercellular communication and the enhancement of ligand-dependent epidermal growth factor receptor activation read more ...