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

Abstract

Apoptin, the VP3 protein from chicken anaemia virus (CAV), induces tumour cell-specific cell death and represents a potential future anti-cancer therapeutic. In tumour but not in normal cells, Apoptin is phosphorylated and translocates to the nucleus, enabling its cytotoxic activity. Recently, the β isozyme of protein kinase C (PKCβ) was shown to phosphorylate Apoptin in multiple myeloma cell lines. However, the exact mechanism and nature of interaction between PKCβ and Apoptin remain unclear. Here we investigated the physical and functional link between PKCβ and CAV-Apoptin as well as with the recently identified Apoptin homologue derived from human Gyrovirus (HGyV). In contrast to HCT116 colorectal cancer cells the normal colon mucosa cell lines expressed low levels of PKCβI and showed reduced Apoptin activation, as evident by cytoplasmic localisation, decreased phosphorylation and lack of cytotoxic activity. Co-immunoprecipitation and proximity ligation assay studies identified binding of both CAV- and HGyV-Apoptin to PKCβI in HCT116 cells. Using Apoptin deletion constructs the N-terminal domain of Apoptin was found to be required for interacting with PKCβI. FRET-based PKC activity reporter assays by fluorescence lifetime imaging microscopy showed that expression of Apoptin in cancer cells but not in normal cells triggers a significant increase in PKC activity. Collectively, the results demonstrate a novel cancer specific interplay between Apoptin and PKCβI. Direct interaction between the two proteins leads to Apoptin-induced activation of PKC and consequently activated PKCβI mediates phosphorylation of Apoptin to promote its tumour-specific nuclear translocation and cytotoxic function.

Efficient therapeutic delivery by a novel cell-permeant peptide derived from KDM4A protein for antitumor and antifibrosis

“…To further evaluating the effectiveness of a potential delivery tool hPP10 for other macromolecules, GFP and Apoptin were conjugated with the C-terminal fragment of hPP10 separately, and their fusion protein produced using prokaryotic expression systems, then we directly visualized the well-distributed in cellular of these conjugated protein. Furthermore, we evaluated the function of these cargo, including the apoptosis induction by Apoptin, although the exact mechanism of apoptosis induced by Apoptin remains obscure [56]. Apoptin fused with hPP10 penetrate into cytoplasm and induce the cancer cell apoptosis.…”

Marek’s disease virus oncoprotein Meq physically interacts with the chicken infectious anemia virus-encoded apoptotic protein apoptin

“…Apoptin is known to bind multiple partners including Hippi [ 22 , 23 ], APC1 [ 23 ], HSP70 [ 24 ], Crm1 protein for nuclear export [ 17 ], Bcr-Abl oncoprotein [ 20 ], p85 subunit of PI3-Kinase [ 25 , 26 ], DEDAF (human death effector domain-associated factor) [ 27 ], FADD, Bcl 10 [ 52 ], and PKC (protein kinase C) beta [ 39 ]. Recent studies have shown that apoptin inhibits Bcr-Abl1 kinases in chronic myeloid leukemia (CML), and regulates the activity of protein kinase C (PKC) in myeloma cell lines, respectively [ 39 , 40 ]. However, none of these proteins have demonstrated a conserved interaction motif, although the larger SH3 domain of Bcr-Abl1 and PI3-Kinase appear to be involved [ 20 , 25 , 26 ].…”

Apoptin as a Tumor-Specific Therapeutic Agent: Current Perspective on Mechanism of Action and Delivery Systems

“…While many reports suggest that cancer cells differentially express a kinase that phosphorylates Apoptin at T108 thereby activating it, the nature and identity of such a kinase have remained an enigma. Protein kinase C (PKC), cyclin-dependent kinases (CDKs) 1 and 2, homeodomain-interacting protein kinase 2 (HIPK2), phosphoinositide 3-kinase (PI3K), and checkpoint kinases (Chk) are some of the kinases that have been incriminated in Apoptin activation ( Los et al, 2009 ; Maddika et al, 2009 ; Kucharski et al, 2011 , 2016 ; Zhao et al, 2013 ; Bullenkamp et al, 2015 ).…”