The actin depolymerizing factor (ADF)/cofilin family comprises small actin-binding proteins with crucial roles in development, tissue homeostasis and disease. They are best known for their roles in ...regulating actin dynamics by promoting actin treadmilling and thereby driving membrane protrusion and cell motility. However, recent discoveries have increased our understanding of the functions of these proteins beyond their well-characterized roles. This Cell Science at a Glance article and the accompanying poster serve as an introduction to the diverse roles of the ADF/cofilin family in cells. The first part of the article summarizes their actions in actin treadmilling and the main mechanisms for their intracellular regulation; the second part aims to provide an outline of the emerging cellular roles attributed to the ADF/cofilin family, besides their actions in actin turnover. The latter part discusses an array of diverse processes, which include regulation of intracellular contractility, maintenance of nuclear integrity, transcriptional regulation, nuclear actin monomer transfer, apoptosis and lipid metabolism. Some of these could, of course, be indirect consequences of actin treadmilling functions, and this is discussed.
E-cadherin is a single-pass transmembrane protein that mediates homophilic cell-cell interactions. Tumour progression is often associated with the loss of E-cadherin function and the transition to a ...more motile and invasive phenotype. This requires the coordinated regulation of both E-cadherin-mediated cell-cell adhesions and integrin-mediated adhesions that contact the surrounding extracellular matrix (ECM). Regulation of both types of adhesion is dynamic as cells respond to external cues from the tumour microenvironment that regulate polarity, directional migration and invasion. Here, we review the mechanisms by which tumour cells control the cross-regulation between dynamic E-cadherin-mediated cell-cell adhesions and integrin-mediated cell-matrix contacts, which govern the invasive and metastatic potential of tumours. In particular, we will discuss the role of the adhesion-linked kinases Src, focal adhesion kinase (FAK) and integrin-linked kinase (ILK), and the Rho family of GTPases.
Focal adhesion kinase (FAK) is both a non-receptor tyrosine kinase and an adaptor protein that primarily regulates adhesion signalling and cell migration, but FAK can also promote cell survival in ...response to stress. FAK is commonly overexpressed in cancer and is considered a high-value druggable target, with multiple FAK inhibitors currently in development. Evidence suggests that in the clinical setting, FAK targeting will be most effective in combination with other agents so as to reverse failure of chemotherapies or targeted therapies and enhance efficacy of immune-based treatments of solid tumours. Here, we discuss the recent preclinical evidence that implicates FAK in anticancer therapeutic resistance, leading to the view that FAK inhibitors will have their greatest utility as combination therapies in selected patient populations.
Focal adhesion kinase (FAK) promotes anti-tumor immune evasion. Specifically, the kinase activity of nuclear-targeted FAK in squamous cell carcinoma (SCC) cells drives exhaustion of CD8+ T cells and ...recruitment of regulatory T cells (Tregs) in the tumor microenvironment by regulating chemokine/cytokine and ligand-receptor networks, including via transcription of Ccl5, which is crucial. These changes inhibit antigen-primed cytotoxic CD8+ T cell activity, permitting growth of FAK-expressing tumors. Mechanistically, nuclear FAK is associated with chromatin and exists in complex with transcription factors and their upstream regulators that control Ccl5 expression. Furthermore, FAK’s immuno-modulatory nuclear activities may be specific to cancerous squamous epithelial cells, as normal keratinocytes do not have nuclear FAK. Finally, we show that a small-molecule FAK kinase inhibitor, VS-4718, which is currently in clinical development, also drives depletion of Tregs and promotes a CD8+ T cell-mediated anti-tumor response. Therefore, FAK inhibitors may trigger immune-mediated tumor regression, providing previously unrecognized therapeutic opportunities.
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•Depletion or kinase inhibition of FAK can cause squamous cell carcinoma regression•FAK promotes tumor evasion by inducing an immuno-suppressive microenvironment•Nuclear FAK promotes transcription of chemokines that drive recruitment of Tregs•FAK-induced Tregs inhibit cytotoxic CD8+ T cells, allowing tumor tolerance and growth
Nuclear focal adhesion kinase (FAK) regulates transcription of chemokines that drive recruitment of tumor-associated regulatory T cells (Tregs), thereby creating a tumor suppressive microenvironment by inhibiting cytotoxic CD8+ T cell activity.
Focal adhesion kinase (FAK) is a scaffold and tyrosine kinase protein that binds to itself and cellular partners through its four-point-one, ezrin, radixin, moesin (FERM) domain. Recent structural ...work reveals that regulatory protein partners convert auto-inhibited FAK into its active state by binding to its FERM domain. Further, the identity of FAK FERM domain-interacting proteins yields clues as to how FAK coordinates diverse cellular responses, including cell adhesion, polarization, migration, survival and death, and suggests that FERM domains might mediate information transfer between the cell cortex and nucleus. Importantly, the FAK FERM domain might act as a paradigm for the actions of other FERM domain-containing proteins.
The calpain system and cancer Martin, Stewart G; Storr, Sarah J; Carragher, Neil O ...
Nature reviews. Cancer,
05/2011, Letnik:
11, Številka:
5
Journal Article
Recenzirano
The calpains are a conserved family of cysteine proteinases that catalyse the controlled proteolysis of many specific substrates. Calpain activity is implicated in several fundamental physiological ...processes, including cytoskeletal remodelling, cellular signalling, apoptosis and cell survival. Calpain expression is altered during tumorigenesis, and the proteolysis of numerous substrates, such as inhibitors of nuclear factor-κB (IκB), focal adhesion proteins (including, focal adhesion kinase and talin) and proto-oncogenes (for example, MYC), has been implicated in tumour pathogenesis. Recent evidence indicates that the increased expression of certain family members might influence the response to cancer therapies, providing justification for the development of novel calpain inhibitors.
Considerable evidence now implicates elevated expression and/or activity of Src in cancer development. In cells, endogenous Src is switched from an inactive to an active state by a variety of ...mechanisms that simultaneously relieve constraints on the kinase and protein-interacting Src homology (SH) domains. As a result, Src is translocated to the cell periphery, often to sites of cell adhesion, where myristylation mediates attachment to the inner surface of the plasma membrane. From these peripheral sites, Src's catalytic activity initiates intracellular signal transduction pathways that influence cell growth and adhesion strength, the latter contributing to control of cell migration. De-regulation in cancer cells may therefore enhance tumour growth and/or stimulate migratory or invasive potential in cells that would normally be relatively non-motile. Evidence now exists to suggest that Src may also influence the life or death decisions that cells make during many biological processes. Thus, Src modulation in cancer cells can alter cell responses that are often perturbed in cancer. Consequently, there is optimism that drugs which inhibit Src's kinase activity, or the activity of its downstream effectors, might have profound effects on cancer cell behaviour and be useful therapeutic agents.
Cell adhesion to macromolecules in the microenvironment is essential for the development and maintenance of tissues, and its dysregulation can lead to a range of disease states, including ...inflammation, fibrosis, and cancer. The biomechanical and biochemical mechanisms that mediate cell adhesion rely on signaling by a range of effector proteins, including kinases and associated scaffolding proteins. The intracellular trafficking of these must be tightly controlled in space and time to enable effective cell adhesion and microenvironmental sensing and to integrate cell adhesion with, and compartmentalize it from, other cellular processes, such as gene transcription, protein degradation, and cell division. Delivery of adhesion receptors and signaling proteins from the plasma membrane to unanticipated subcellular locales is revealing novel biological functions. Here, we review the expected and unexpected trafficking, and sites of activity, of adhesion and growth factor receptors and intracellular kinase partners as we begin to appreciate the complexity and diversity of their spatial regulation.
TP53 mutation occurs in 50-75% of human pancreatic ductal adenocarcinomas (PDAC) following an initiating activating mutation in the KRAS gene. These p53 mutations frequently result in expression of a ...stable protein, p53R¹⁷⁵H, rather than complete loss of protein expression. In this study we elucidate the functions of mutant p53 (Trp53R¹⁷²H), compared to knockout p53 (Trp53fl), in a mouse model of PDAC. First we find that although KrasG¹²D is one of the major oncogenic drivers of PDAC, most KrasG¹²D-expressing pancreatic cells are selectively lost from the tissue, and those that remain form premalignant lesions. Loss, or mutation, of Trp53 allows retention of the KrasG¹²D-expressing cells and drives rapid progression of these premalignant lesions to PDAC. This progression is consistent with failed growth arrest and/or senescence of premalignant lesions, since a mutant of p53, p53R¹⁷²P, which can still induce p21 and cell cycle arrest, is resistant to PDAC formation. Second, we find that despite similar kinetics of primary tumor formation, mutant p53R¹⁷²H, as compared with genetic loss of p53, specifically promotes metastasis. Moreover, only mutant p53R¹⁷²H-expressing tumor cells exhibit invasive activity in an in vitro assay. Importantly, in human PDAC, p53 accumulation significantly correlates with lymph node metastasis. In summary, by using 'knock-in' mutations of Trp53 we have identified two critical acquired functions of a stably expressed mutant form of p53 that drive PDAC; first, an escape from KrasG¹²D-induced senescence/growth arrest and second, the promotion of metastasis.
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