The viral death protein Apoptin interacts with Hippi, the protein interactor of Huntingtin-interacting protein 1

Cheng, C. C.; Huang, Shih-Hui; Chang, Yung-Fu; Chung, Wen Yuan; Yuo, Chung-Yee

doi:10.1016/s0006-291x(03)00764-2

Cited by 34 publications

(32 citation statements)

References 13 publications

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Wadia et al (7) recently claimed that apoptin, a virally encoded protein with tumor-selective apoptosis activity, contains a concentration-dependent nuclear localization signal (NLS) that is not tumor selective as previously reported (1,2,4). Their Fig.

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confidence: 95%

Relevance of Apoptin's Integrity for Its Functional Behavior

Rohn

Zhang

Leliveld

et al. 2005

J Virol

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Wadia et al. (7) recently claimed that apoptin, a virally encoded protein with tumor-selective apoptosis activity, contains a concentration-dependent nuclear localization signal (NLS) that is not tumor selective as previously reported (1,2,4). Their Fig. 1B shows, however, that under all the conditions tested, nuclear import of green fluorescent protein (GFP)-apoptin 70-121 remains 200 to 300% higher in tumor cells than in primary cells. The apparent concentration dependence of apoptin's NLS is intriguing. We agree with their interpretation that presentation of multiple apoptin NLS domains by a molecular aggregate could generate more efficient nuclear trafficking than NLS exposure at a single site. This result is, however, somewhat academic, as full-length apoptin can only be harvested as a multimer from live cells, with a dissociation rate constant (k off ) that is so slow that it can hardly be measured, whereas the C-terminal fragment forms only monomers (5, 9). This could explain why Wadia et al. could measure a cooperative, concentration-dependent effect of apoptin's NLS, as they used a GFP fusion of a C-terminal fragment of apoptin lacking the multimerization domain (5). Had they used full-length apoptin, all the NLS sequences would likely have been clustered, resulting in effective nuclear import over all concentration ranges. Nevertheless, we suggest caution in using GFPapoptin fusions in functional studies. For example, fusion of GFP to full-length apoptin results in increased levels of nuclear GFP-apoptin versus wild-type apoptin in primary cells (Fig. 1A).The current hypothesis is that nuclear trafficking and tumorspecific phosphorylation of apoptin at Thr108 are essential for induction of apoptosis (3,6,8). Wadia et al. reported a failure to detect phosphorylation with radioactive labeling of GFPapoptin 70-121 ; we do not know why this is so, as phosphorylation of full-length apoptin has been thoroughly documented by the use of mass spectrometry and a phospho-specific antibody (6). Our preliminary experiments suggest that abolishing the phosphorylation site of apoptin does not significantly disrupt its nuclear import in tumor cells. In attempting to address this observation with a GFP-apoptin 70-121 T108A mutant, Wadia et al. used a construct that is not phospho-null in vivo; in our hands, as Thr108 is the last in a run of three threonine residues, the adjacent Thr107 becomes opportunistically phosphorylated instead, which yields the same phenotype. Mutation at both positions 107 and 108 is required to eliminate phosphorylation and function. As Fig. 1B indicates, phosphorylation of apoptin is required for apoptosis induced by its Cterminal death domain (3); a control experiment confirms that the apoptosis-competent fragment is phosphorylated on Thr108 in vivo (Fig. 1C).Apoptin's tumor-specific activity does not result from a single characteristic. Its multimerization behavior, its potential to be phosphorylated, its cooperativity in nuclear trafficking, and many of its other physical, chemical, and f...

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confidence: 95%

Relevance of Apoptin's Integrity for Its Functional Behavior

Rohn

Zhang

Leliveld

et al. 2005

J Virol

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“…Co-immunoprecipitation and PLA studies convincingly showed direct binding and co-localisation of Apoptin and PKCbI. This interaction seemed to require the N-terminal region of Apoptin which has been shown to be involved in both binding of Apoptin to other cellular proteins [32][33][34] as well as Apoptin multimerisation [35]. Importantly, interaction with Apoptin triggered nuclear translocation of PKCbI; to our knowledge this is a novel phenomenon in respect to PKCbI activity.…”

Section: Discussionmentioning

confidence: 62%

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

et al. 2015

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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.

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“…In normal cells, apoptin binding to Hippi results in co-localization of the complex in the cytoplasm; while in the cancer cells, apoptin moves to nucleus and Hippi remained in the cytoplasm [139].…”

Section: Hip-1 Interacting Protein (Hippi)mentioning

confidence: 99%

Viral genes as oncolytic agents for cancer therapy

Gupta

Gandham

Sahoo

et al. 2014

Cell. Mol. Life Sci.

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Many viruses have the ability to modulate the apoptosis, and to accomplish it; viruses encode proteins which specifically interact with the cellular signaling pathways. While some viruses encode proteins, which inhibit the apoptosis or death of the infected cells, there are viruses whose encoded proteins can kill the infected cells by multiple mechanisms, including apoptosis. A particular class of these viruses has specific gene(s) in their genomes which, upon ectopic expression, can kill the tumor cells selectively without affecting the normal cells. These genes and their encoded products have demonstrated great potential to be developed as novel anticancer therapeutic agents which can specifically target and kill the cancer cells leaving the normal cells unharmed. In this review, we will discuss about the viral genes having specific cancer cell killing properties, what is known about their functioning, signaling pathways and their therapeutic applications as anticancer agents.

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The viral death protein Apoptin interacts with Hippi, the protein interactor of Huntingtin-interacting protein 1

Cited by 34 publications

References 13 publications

Relevance of Apoptin's Integrity for Its Functional Behavior

Relevance of Apoptin's Integrity for Its Functional Behavior

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

Viral genes as oncolytic agents for cancer therapy

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