Tankyrases: Structure, Function and Therapeutic Implications in Cancer

Haikarainen, T.; Krauß, Stefan; Lehtiö, L.

doi:10.2174/1381612820666140630101525

Cited by 163 publications

(204 citation statements)

References 155 publications

(283 reference statements)

Supporting

Mentioning

200

Contrasting

Unclassified

Order By: Relevance

“…Inhibition of the PARP enzyme TNKS is garnering attention as a promising colon cancer therapeutic that blunts oncogenic ␤cat signaling through stabilization of Axin (41,42). TNKS normally functions to promote Axin degradation through direct PARylation and subsequent ubiquitination of Axin by the PARdependent E3 ubiquitin ligase RNF146.…”

Section: Discussionmentioning

confidence: 99%

The Poly(ADP-ribose) Polymerase Enzyme Tankyrase Antagonizes Activity of the β-Catenin Destruction Complex through ADP-ribosylation of Axin and APC2

Croy¹,

Fuller²,

Giannotti³

et al. 2016

Journal of Biological Chemistry

View full text Add to dashboard Cite

Most colon cancer cases are initiated by truncating mutations in the tumor suppressor, adenomatous polyposis coli (APC).APC is a critical negative regulator of the Wnt signaling pathway that participates in a multi-protein "destruction complex" to target the key effector protein ␤-catenin for ubiquitin-mediated proteolysis. Prior work has established that the poly(ADPribose) polymerase (PARP) enzyme Tankyrase (TNKS) antagonizes destruction complex activity by promoting degradation of the scaffold protein Axin, and recent work suggests that TNKS inhibition is a promising cancer therapy. We performed a yeast two-hybrid (Y2H) screen and uncovered TNKS as a putative binding partner of Drosophila APC2, suggesting that TNKS may play multiple roles in destruction complex regulation. We find that TNKS binds a C-terminal RPQPSG motif in Drosophila APC2, and that this motif is conserved in human APC2, but not human APC1. In addition, we find that APC2 can recruit TNKS into the ␤-catenin destruction complex, placing the APC2/ TNKS interaction at the correct intracellular location to regulate ␤-catenin proteolysis. We further show that TNKS directly PARylates both Drosophila Axin and APC2, but that PARylation does not globally regulate APC2 protein levels as it does for Axin. Moreover, TNKS inhibition in colon cancer cells decreases ␤-catenin signaling, which we find cannot be explained solely through Axin stabilization. Instead, our findings suggest that TNKS regulates destruction complex activity at the level of both Axin and APC2, providing further mechanistic insight into TNKS inhibition as a potential Wnt pathway cancer therapy.The Wnt pathway helps direct a myriad of normal developmental and adult homeostasic processes in metazoans, but is also misregulated in several human diseases such as cancer (1, 2). Wnt signaling is regulated through the activity of a multiprotein "destruction complex" that promotes proteolysis of the transcriptional co-activator ␤-catenin (␤cat) 3 by stimulating phosphorylation of the ␤cat phosphodegron (3). Core components of the destruction complex include the scaffold protein Axin, the tumor suppressor adenomatous polyposis coli (APC), and the kinases CK1 and GSK3.While Wnt signaling plays essential roles during development, it is inappropriately activated in a number of cancers, most notably colorectal cancer. Truncating mutations in the tumor suppressor adenomatous polyposis coli (APC) are the initiating mutational event in more than 80% of all colon cancer cases, and these mutations hyperactivate ␤cat signaling (4). Thus small molecule inhibitors of the Wnt pathway should provide an effective therapeutic strategy. Among these strategies, inhibition of oncogenic ␤cat activity would appear to be the most direct approach, as studies have demonstrated that the accumulation of ␤cat is what initiates oncogenesis, and that tumors have a continued reliance on oncogenic ␤cat signaling (5). Indeed, recent promising antagonists have been identified that specifically disrupt ␤cat binding to TCF or th...

show abstract

Section: Discussionmentioning

confidence: 99%

The Poly(ADP-ribose) Polymerase Enzyme Tankyrase Antagonizes Activity of the β-Catenin Destruction Complex through ADP-ribosylation of Axin and APC2

Croy¹,

Fuller²,

Giannotti³

et al. 2016

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…However, a number of PARPs are involved in non-DNA damage related processes (e.g. tankyrases, reviewed in 22) that take place outside the nucleus. Hydrolysis of PAR chains created by other PARPs is likely to involve PARG or ARH3 23 .…”

Section: Discussionmentioning

confidence: 99%

An assay to measure poly(ADP ribose) glycohydrolase (PARG) activity in cells

et al. 2016

View full text Add to dashboard Cite

After a DNA damage signal multiple polymers of ADP ribose attached to poly(ADP) ribose (PAR) polymerases (PARPs) are broken down by the enzyme poly(ADP) ribose glycohydrolase (PARG). Inhibition of PARG leads to a failure of DNA repair and small molecule inhibition of PARG has been a goal for many years. To determine whether biochemical inhibitors of PARG are active in cells we have designed an immunofluorescence assay to detect nuclear PAR after DNA damage. This 384-well assay is suitable for medium throughput high-content screening and can detect cell-permeable inhibitors of PARG from nM to µM potency. In addition, the assay has been shown to work in murine cells and in a variety of human cancer cells. Furthermore, the assay is suitable for detecting the DNA damage response induced by treatment with temozolomide and methylmethane sulfonate (MMS). Lastly, the assay has been shown to be robust over a period of several years.

show abstract

“…Modified proteins are subsequently poly-ubiquitinated and predominantly turned over by proteasomal degradation (9). TNKS1/2 are involved in a wide range of cellular functions (10) and were recently shown to positively regulate the WNT/b-catenin pathway through poly-ADP-ribosylation of AXIN (11), the rate-limiting factor for destruction complex stability and function (12).…”

Section: Introductionmentioning

confidence: 99%

“…TNKS1/2 are involved in a wide range of cellular functions (10) and were recently shown to positively regulate the WNT/b-catenin pathway through poly-ADP-ribosylation of AXIN (11), the rate-limiting factor for destruction complex stability and function (12). Implication of TNKS1/2 as druggable targets in the WNT/b-catenin signaling pathway has generated profound research on developing novel small-molecule inhibitors (9,13,14). Inhibition of the catalytic activity of TNKS1/2 reduces WNT/b-catenin signaling in both APC wild-type cells (e.g., in HEK293) and colorectal cancer cells harboring APC truncations (e.g., in SW480; refs.…”

Section: Introductionmentioning

confidence: 99%

Structure, Dynamics, and Functionality of Tankyrase Inhibitor-Induced Degradasomes

Thorvaldsen

Pedersen

Wenzel

et al. 2015

Molecular Cancer Research

Self Cite

View full text Add to dashboard Cite

Tankyrase (TNKS) enzymes, due to their poly(ADP-ribose) polymerase activity, have emerged as potential targets in experimental cancer therapy. However, the functional consequences of TNKS inhibition remain incompletely resolved because of the binding promiscuity of TNKS. One of the hallmarks of small-molecule TNKS inhibitors (TNKSi) is the stabilization of AXIN, which plays a pivotal role in the WNT/b-catenin signaling pathway. The present study focused on the known ability of TNKSi to induce cytoplasmic puncta (degradasomes) consisting of components of the signallimiting WNT/b-catenin destruction complex. Using the colorectal cancer cell line SW480 stably transfected with GFP-TNKS1, it was demonstrated that a TNKS-specific inhibitor (G007-LK) induces highly dynamic and mobile degradasomes that contain phosphorylated b-catenin, ubiquitin, and b-TrCP. Likewise, G007-LK was found to induce similar degradasomes in other colorectal cancer cell lines expressing wild-type or truncated versions of the degradasome component APC. Super-resolution and electron microscopy revealed that the induced degradasomes in SW480 cells are membrane-free structures that consist of a filamentous assembly of high electron densities and discrete subdomains of various destruction complex components. Fluorescence recovery after photobleaching experiments further demonstrated that b-catenin-mCherry was rapidly turned over in the G007-LK-induced degradasomes, whereas GFP-TNKS1 remained stable. In conclusion, TNKS inhibition attenuates WNT/b-catenin signaling by promoting dynamic assemblies of functional active destruction complexes into a TNKS-containing scaffold even in the presence of an APC truncation.Implications: This study demonstrates that b-catenin is rapidly turned over in highly dynamic assemblies of WNT destruction complexes (degradasomes) upon tankyrase inhibition and provides a direct mechanistic link between degradasome formation and reduced WNT signaling in colorectal cancer cells.

show abstract

Tankyrases: Structure, Function and Therapeutic Implications in Cancer

Cited by 163 publications

References 155 publications

The Poly(ADP-ribose) Polymerase Enzyme Tankyrase Antagonizes Activity of the β-Catenin Destruction Complex through ADP-ribosylation of Axin and APC2

The Poly(ADP-ribose) Polymerase Enzyme Tankyrase Antagonizes Activity of the β-Catenin Destruction Complex through ADP-ribosylation of Axin and APC2

An assay to measure poly(ADP ribose) glycohydrolase (PARG) activity in cells

Structure, Dynamics, and Functionality of Tankyrase Inhibitor-Induced Degradasomes

Contact Info

Product

Resources

About