Human Gyrovirus Apoptin shows a similar subcellular distribution pattern and apoptosis induction as the chicken anaemia virus derived VP3/Apoptin

Abstract

The chicken anaemia virus-derived protein Apoptin/VP3 (CAV-Apoptin) has the important ability to induce tumour-selective apoptosis in a variety of human cancer cells. Recently the first human Gyrovirus (HGyV) was isolated from a human skin swab. It shows significant structural and organisational resemblance to CAV and encodes a homologue of CAV-Apoptin/VP3. Using overlapping primers we constructed a synthetic human Gyrovirus Apoptin (HGyV-Apoptin) fused to green fluorescent protein in order to compare its apoptotic function in various human cancer cell lines to CAV-Apoptin. HGyV-Apoptin displayed a similar subcellular expression pattern as observed for CAV-Apoptin, marked by translocation to the nucleus of cancer cells, although it is predominantly located in the cytosol of normal human cells. Furthermore, expression of either HGyV-Apoptin or CAV-Apoptin in several cancer cell lines triggered apoptosis at comparable levels. These findings indicate a potential anti-cancer role for HGyV-Apoptin.

Apoptin interacts with and regulates the activity of protein kinase C beta in cancer cells

“…2a). As expected from their respective amino acid sequences, HGyV-Apoptin was detected at a slightly higher molecular weight than CAVApoptin [3]. Similarly, the reciprocal immunoprecipitation using anti-HA antibodies confirmed binding of Apoptin to PKCbI in HCT116 cells (data not shown).…”

“…Increased expression levels of PKCbI in HCT116 cells correlated with enhanced activation of Apoptin, demonstrated by increased expression and phosphorylation levels of Apoptin, its translocation to the nucleus as well as induction of apoptosis in cancer cells while normal colon mucosa cells remained resistant to Apoptin expression. Knockdown of PKCbI in HCT116 Interestingly, HGyV-Apoptin, a recently identified VP3 homologue derived from the first human Gyrovirus HGyV [2,3], was also shown to interact with PKCbI. An online kinase prediction assay of the HGyV-Apoptin amino acid sequence (http://www.cbs.dtu.dk/services/NetPhos) revealed several potential phosphorylation sites matching the PKC consensus motif (S/TXK/R or S/TXXK/R) including Thr-111 which, like Thr-108 of CAV-Apoptin, is adjacent to a putative NES within the respective protein.…”

“…In recent years several other viruses resembling the overall organisation of CAV have been identified, including the first human Gyrovirus HGyV [2] which contains a VP3 protein with similar properties as CAVApoptin [3]. Importantly, Apoptin has the ability to selectively kill various human tumour or transformed cells with little cytotoxic effect in normal cells [4][5][6][7].…”

Human Gyrovirus-Apoptin Interferes with the Cell Cycle and Induces G2/M Arrest Prior to Apoptosis

“…Little is known about the molecular mechanism of action of HGyv-Apoptin. HGyvApoptin has the same subcellular distribution as the CAV-Apoptin; it localizes in the nuclei of cancer cells where it shows a granular distribution that later clusters to form aggregates while it remains in the cytoplasm of normal cells (Bullenkamp et al 2012). Despite a low overall identity important regions such as the nuclear localization and export signals and phosphorylation sites are conserved between HGyV and CAV-Apoptin suggesting a similar mechanism of action (Sauvage et al 2011) (Fig.…”

Cancer and cancer stem cell targeting agents : A focus on salinomycin and apoptin

“…With the recent discovery of human gyroviral-derived apoptin showing similar function in cell death as its chicken homolog, apoptin-based therapies may be developed in the foreseeable future 81,91,92 .…”