Essays in Biochemistry (2019) 63 579–594 https://doi.org/10.1042/EBC20190022 Review Article The role of DUBs in the post-translational control of cell migration Guillem Lambies1,2, Antonio Garc´ıade Herreros1,2 and V´ıctor M. D´ıaz1,2,3 1Programa de Recerca en Cancer,` Institut Hospital del Mar d’Investigacions Mediques` (IMIM), Unidad Asociada CSIC, Barcelona, Spain; 2Departament de Ciencies` Experimentals i de la Salut, Universitat Pompeu Fabra (UPF), Barcelona, Spain; 3Faculty of Medicine and Health Sciences, International University of Catalonia, Sant Cugat del Valles,` Barcelona, Spain Downloaded from https://portlandpress.com/essaysbiochem/article-pdf/63/5/579/859061/ebc-2019-0022c.pdf by guest on 05 November 2019 Correspondence: V.M. Dıaz´ ([email protected])orA.Garcıa´ de Herreros ([email protected]) Cell migration is a multifactorial/multistep process that requires the concerted action of growth and transcriptional factors, motor proteins, extracellular matrix remodeling and proteases. In this review, we focus on the role of transcription factors modulat- ing Epithelial-to-Mesenchymal Transition (EMT-TFs), a fundamental process supporting both physiological and pathological cell migration. These EMT-TFs (Snail1/2, Twist1/2 and Zeb1/2) are labile proteins which should be stabilized to initiate EMT and provide full mi- gratory and invasive properties. We present here a family of enzymes, the deubiquitinases (DUBs) which have a crucial role in counteracting polyubiquitination and proteasomal degra- dation of EMT-TFs after their induction by TGFβ, inflammatory cytokines and hypoxia. We also describe the DUBs promoting the stabilization of Smads, TGFβ receptors and other key proteins involved in transduction pathways controlling EMT. Introduction Epithelial-to-mesenchymal transition (EMT) is a cell process allowing epithelial cells to adopt mesenchy- mal properties and enhance their migratory capability [1]. Although some other types of migration have been described [3,4], in this review, we will focus on that related with EMT and describe how it is modu- lated by a myriad of labile proteins that need to be stabilized. In particular, we will analyze the role of an emergent class of enzymes called deubiquitinases (DUBs) in several aspects of cell migration. Typesofcellmigration Physiological cell migration during embryonic development and wound healing EMT is particularly relevant during embryonic development since it allows cells to migrate over extremely long distances in the embryo, giving rise to the formation of the three-dimensional structures and orig- ination of the different organs in the final organism. EMT happens early in embryonic development, in the generation of parietal endoderm and in the mesoderm and neural crest formation [2–4]. For instance, neural crest arises from a population of precursor cells that escape from the neural tube and migrate a long distance in the embryo, promoting the formation of different subtypes of cells [5]. Upon migra- tion of neural crest cells to the different locations, cells become again epithelial undergoing the opposite Received: 21 June 2019 process, the mesenchymal-to-epithelial transition, performing transient epithelial structures such as the Revised: 30 September 2019 somites, the precursors of the urogenital system and the splachnopleure. These structures again undergo Accepted: 01 October 2019 EMT to promote mesenchymal cells with a more restricted differentiation potential [5]. Besides morpho- Version of Record published: genesis, the acquisition of migratory properties through an EMT in physiological conditions plays a key 11 October 2019 role in other physiological processes such as wound healing, the response of the organism to an injury in © 2019 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society 579 Essays in Biochemistry (2019) 63 579–594 https://doi.org/10.1042/EBC20190022 the skin. Keratinocytes from the epidermis located at the wound border undergo a partial EMT, acquiring the capa- bilities to migrate [2]. Pathological cell migration: fibrosis and cancer metastasis Cell migration is also involved in pathological processes such as fibrosis and cancer invasion. Fibrosis involves organ degeneration and takes place following tissue injuries such as cardiac failure [6]. This results in a massive deposition of collagen fibers mediated by fibroblastic cells derived from a set of epithelial cells via an EMT process. These cells migrate to the injured tissue and secrete a huge amount of fibroblastic proteins such as Collagen I and alpha-smooth muscle actin (α-SMA) [6]. The fibrotic EMT has been observed in many organs, such as liver, lung and intestine [7]. EMT also plays a crucial role in cancer. Even though EMT features had been largely observed in in vitro and in vivo cancer models, the relevance of EMT for cancer metastasis has been a matter of debate for many years [8]. This is due to the similarity between the mesenchymal cells derived from an EMT program and the stromal cells, two cell Downloaded from https://portlandpress.com/essaysbiochem/article-pdf/63/5/579/859061/ebc-2019-0022c.pdf by guest on 05 November 2019 types sharing similar markers [2]. The first relationship between EMT and cancer metastasis was observed in HER2 transgenic mice showing cancer cells with migratory features [9]. On the other hand, detection of cell aggregates detaching from the tumor into the adjacent stroma further confirmed the involvement of EMT in cancer metastasis [10]. Genetic lineage-tracing experiments have formally demonstrated the role of EMT during invasion [11], although other studies have questioned a critical role of EMT in metastasis [12,13]. In any case, besides metastasis formation, the role of EMT in chemo-resistance is beyond any doubt [14,15]. Molecular mechanisms controlling cell migration Epithelial cells maintain cell contacts between them through the arrangement of tight junctions, desmosomes and adherent junctions which are lost during EMT promotion. Occludins, claudins and Zona-Occludens 1 (components of tight junctions) or desmoplakins (of desmosomes) are down-regulated during EMT. However, the most relevant feature of EMT is the loss of the essential homotypic adherent junction E-cadherin [16], encoded by the CDH1 gene, which mediates homophilic intercellular interactions through its extracellular domain. These junctions are main- tained by anchoring its intracellular domain to actin filaments via β-catenin association [17]. This loss of the epithe- lial markers is accompanied by an up-regulation of mesenchymal proteins such as Fibronectin. Fibronectin mediates extracellular matrix (ECM) assembly through the binding to α5β1 integrins; this stimulates its self-association and organizes the actin cytoskeleton to promote cell contractility. It also allows the assembly of other fibrous proteins such as Collagen I [18]. Another relevant trait in the modulation of cell migration is the positive modulation of the Rho-GTPases, involved in lamelipodium extension at the front of the cell, formation of new adhesions of the cell to surrounding matrix proteins, cell body contraction and tail retraction [19]. Moreover, Rho is essential to mediate actin contractility to promote fibronectin-dependent ECM assembly [20]. Cell migration also requires the up-regulation of proteases that degrade basement membranes, enhancing the capability of cells to invade and migrate [21,22]. Transcription factors modulating EMT and cell migration The expression of epithelial and mesenchymal markers is tightly regulated by different transcription factors collec- tively known as transcription factors modulating EMT (EMT-TFs). Snail1 is considered the main EMT-TF [16]. It binds sequences with a 5-CACCTG-3 core located in the promoters of CDH1 and other epithelial markers, such as occludins and claudins. Besides its role as a repressor, Snail1 also works as an activator, up-regulating the expression of mesenchymal markers such as fibronectin and the EMT-TFs Zeb1 and 2 [23–25]. Similar to Snail1, Zeb1 and 2 repress E-cadherin and are required for EMT [26]. Besides Snail1 and Zeb1/2, other EMT-TFs also promoting migra- tion are the basic helix–loop–helix proteins Twist1 and 2 [27]. Snail1 and EMT-TFs induce all the molecular events required for cell migration such as a high protease secretion and a stimulation of Rho-GTPase and Akt activity, a proteinkinasealsorequiredforcellinvasion[4]. Signaling pathways controlling EMT Different signaling pathways induce EMT being the most studied that are triggered by TGF-β [28]. TGF-β signals through serine/threonine kinase receptors; it binds to the TGF-β receptor type II (TβRII) that associates with the typeI(TβRI), phosphorylating its Ser/Thr kinase domain; this propagates the signal through the recruitment and phosphorylation of the Smad proteins [29]. TGF-β activates Snai1 transcription through Smad–HMGA2 complex that binds to the Snai1 promoter [30]. TGF-β pathway also cross-talks with other signaling pathways, such as Wnt and Notch. Canonical Wnt ligands interact with the transmembrane proteins LRP5/6 and Frizzled promoting the recruitment of the adenomatous polyposis coli (APC)/Axin/Glycogen-synthase kinase 3 complex to the membrane 580 © 2019 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society Essays in Biochemistry (2019) 63 579–594 https://doi.org/10.1042/EBC20190022 and preventing β-catenin degradation; consequently, β-catenintranslocatestothenucleusandinducestheexpression