- Title
- Actin crosslinking protein α-actinin-4 (ACTN4) regulates receptor-interacting serine/threonine-protein kinase 1 (RIPK1) in melanoma
- Creator
- Zhang, Yuanyuan
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2019
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- ACTN4 is a member of the α-actinin family of filamentous actin crosslinking proteins important for regulation of cytoskeletal integrity and cell movement (Honda, 2015; Honda et al., 1998; Hsu and Kao, 2013). Like other family members, ACTN4 contains an N-terminal actin-binding domain (ABD) with two calponin-homology (CH) repeats, a central rod domain (RD) with 4 spectrin-like repeats (SR) that is essential for anti-parallel dimerisation of ACTN4, and a calmodulin (CaM)-like domain (CLD) at the C-terminus (Broderick and Winder, 2002; Djinovic-Carugo et al., 2002; Hsu and Kao, 2013). Although ACTN4 is ubiquitously expressed in normal non-muscle cells (Hsu and Kao, 2013; Oikonomou et al., 2011), its expression is frequently increased in various types of cancer cells including melanoma cells and high ACTN4 expression levels are often correlated with disease progression and poor patient prognosis (Kakuya et al., 2017; Watanabe et al., 2015; Yamamoto et al., 2009). Indeed, there is increasing evidence pointing to a role of ACTN4 in the pathogenesis of cancer (Kakuya et al., 2017; Noro et al., 2013; Watabe et al., 2014; Yamamoto et al., 2009; Yamamoto et al., 2012). This is not only due to its critical involvement in regulation of cancer cell adhesion, invasion, and metastasis (Gao et al., 2015; Honda et al., 1998; Shao et al., 2014), but also closely associated with its role in regulation of signalling pathways through its interaction with a large array of proteins (Agarwal et al., 2013; Aksenova et al., 2013; Khurana et al., 2011). For example, ACTN4 targets the p65/RelA subunit of NF-κB to the nucleus in breast cancer cells upon stimulation with tumour necrosis factor α (TNF-α) or epithelial growth factor (EGF), where it functions as a co-factor for transactivation of nuclear factor κB (NF-κB) target genes (Aksenova et al., 2013; Babakov et al., 2008). Moreover, ACTN4 interacts with Akt1 and promotes its phosphorylation (activation) thus leading to enhanced cell survival and proliferation (Ding et al., 2006). Although the activity of ACTN4 is known to be modulated by multiple mechanisms such as processing by calpain protease, phosphorylation by protein kinases, and binding to phosphatidylinositol intermediates (Carragher et al., 2001; Shao et al., 2010; Sjoblom et al., 2008), how ACTN4 expression is regulated remains to be defined. RIPK1 is a Ser/Thr protein kinase that plays an important role in cell survival and death signal transduction and is a critical determinant of cell fate in response to cellular stress (Christofferson et al., 2012; Festjens et al., 2007; Jin et al., 2016; Liu et al., 2015; Luan et al., 2015; Wang et al., 2008), in particular, in response to activation of death receptors such as TNF receptor 1 (TNFR1). Upon TNFR1 stimulation, prosurvival complex I is formed via recruiting RIPK1 and other proteins involving cellular inhibitor of apoptosis proteins (cIAP1/2), TNFR-associated death domain (TRADD), and TNFR-associated factors (TRAF2/5) (Ofengeim and Yuan, 2013; Wang et al., 2008). This results in stabilisation of RIPK1 through K63-linked polyubiquitination by cIAPs (Bertrand et al., 2008; Liu et al., 2015). K63-linked polyubiquitin chains serve as substrates for binding of the transforming growth factor-β (TGF-β)-activated kinase 1 (TAK1)/TAK1-binding proteins 2 and 3 (TAB2/3) complex and NF-κB essential modulator (NEMO), leading to activation of NF-κB (Blackwell et al., 2013; Liu et al., 2015; Ofengeim and Yuan, 2013). When cIAPs are blocked, RIPK1 is deubiquitinated and its function is switched to that of promoting apoptosis, or alternatively, necroptosis in certain types of cells (Moquin et al., 2013; Wang et al., 2008). RIPK1 is often upregulated and promotes cell proliferation via activation of NF-κB in melanoma (Liu et al., 2015). Stabilisation of RIPK1 by cIAPs is critical for its increased expression (Bertrand et al., 2008; Liu et al., 2015). Here we demonstrate that ACTN4 is necessary for cIAP-mediated stabilisation of RIPK1 through acting as a scaffold to enable the physical association between cIAP1 and RIPK1, and thus plays a critical role in activation of NF-κB and promotion of melanoma cell proliferation. Moreover, we show that NF-κB signalling is responsible for ACTN4 transcriptional upregulation in melanoma cells.
- Subject
- ACTN4; melanoma; cancer; receptor-interacting serine/threonine-protein kinase 1 (RIPK1)
- Identifier
- http://hdl.handle.net/1959.13/1395609
- Identifier
- uon:33913
- Rights
- Copyright 2019 Yuanyuan Zhang
- Language
- eng
- Full Text
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