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Cis-regulatory elements of alternative splicing in the human FAK gene. Known cis-regulatory elements involved in mRNA alternative splicing were searched in the human FAK gene (NCBI Gene ID: 5747) as described in the Methods section. (A) Frequency of ACE-EXs per 100 bp in each FAK exon. (B) Frequencies of exonic splicing enhancers (ESE, black) and exonic splicing silencers (ESS, grey) per 100 bp in each FAK exon (for example 5 ESE and 23 ESS/100 bp were found in exon 14). (C) Frequency of the hexamer UGCAUG per 10,000 bp in each FAK intron (numbered according to their 5' flanking exon).
Source publication
Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase critical for processes ranging from embryo development to cancer progression. Although isoforms with specific molecular and functional properties have been characterized in rodents and chicken, the organization of FAK gene throughout phylogeny and its potential to generate multiple isofo...
Citations
... First, PF-573228 inhibits FAK activity as well as the activity of other related kinases. Second, PYK2, a close paralogue to FAK has been shown to functionally compensate for loss of FAK (90,91), albeit 50-to 250-fold less selective for FAK than PYKA (92). In oncological and chronic disease applications dual FAK/PYKA inhibition has been shown to be more efficacious (93). ...
Introduction
Heterotopic ossification (HO) is a complex pathology often observed in combat injured casualties who have sustained severe, high energy polytraumatic extremity injuries. Once HO has developed, prophylactic therapies are limited outside of surgical excision. Tourniquet-induced ischemia injury (IR) exacerbates trauma-mediated musculoskeletal tissue injury, inflammation, osteogenic progenitor cell development and HO formation. Others have shown that focal adhesion kinase-2 (FAK2) plays a key role in regulating early inflammatory signaling events. Therefore, we hypothesized that targeting FAK2 prophylactically would mitigate extremity trauma induced IR inflammation and HO formation.
Methods
We tested whether the continuous infusion of a FAK2 inhibitor (Defactinib, PF-573228; 6.94 µg/kg/min for 14 days) can mitigate ectopic bone formation (HO) using an established blast-related extremity injury model involving femoral fracture, quadriceps crush injury, three hours of tourniquet-induced limb ischemia, and hindlimb amputation through the fracture site. Tissue inflammation, infiltrating cells, osteogenic progenitor cell content were assessed at POD-7. Micro-computed tomography imaging was used to quantify mature HO at POD-56.
Results
In comparison to vehicle control-treated rats, FAK2 administration resulted in no marked wound healing complications or weight loss. FAK2 treatment decreased HO by 43%. At POD-7, marked reductions in tissue proinflammatory gene expression and assayable osteogenic progenitor cells were measured, albeit no significant changes in expression patterns of angiogenic, chondrogenic and osteogenic genes. At the same timepoint, injured tissue from FAK-treated rats had fewer infiltrating cells. Additionally, gene expression analyses of tissue infiltrating cells resulted in a more measurable shift from an M1 inflammatory to an M2 anti-inflammatory macrophage phenotype in the FAK2 inhibitor-treated group.
Discussion
Our findings suggest that FAK2 inhibition may be a novel strategy to dampen trauma-induced inflammation and attenuate HO in patients at high risk as a consequence of severe musculoskeletal polytrauma.
... FAK is a type of cytoplasmic tyrosine kinase that is activated by both growth factors and integrins. Through AS of FAK pre-mRNA, specific exons (13,14,16, and 31) can be included independently, which in turn code for specific domains (boxes 28, 6, 7, and Pro-Trp-Arg, or PWR) that characterize FAK (140). There are different forms of FAK resulting from AS of its pre-mRNA. ...
RNA splicing is the process of forming mature mRNA, which is an essential phase necessary for gene expression and controls many aspects of cell proliferation, survival, and differentiation. Abnormal gene-splicing events are closely related to the development of tumors, and the generation of oncogenic isoform in splicing can promote tumor progression. As a main process of tumor-specific splicing variants, alternative splicing (AS) can promote tumor progression by increasing the production of oncogenic splicing isoforms and/or reducing the production of normal splicing isoforms. This is the focus of current research on the regulation of aberrant tumor splicing. So far, AS has been found to be associated with various aspects of tumor biology, including cell proliferation and invasion, resistance to apoptosis, and sensitivity to different chemotherapeutic drugs. This article will review the abnormal splicing events in colorectal cancer (CRC), especially the tumor-associated splicing variants arising from AS, aiming to offer an insight into CRC-targeted splicing therapy.
... a region shown to have frequent aberrations in human oncology (Pylayeva et al., 2009;Schaller, 2010). The coding sequence of FAK, a highly conserved 125 kDa non-receptor tyrosine kinase, contains 34 exons (Corsi et al., 2006). FAK consists of an amino-terminal region containing a 4.1-Ezrin-Radixin-moesin (FERM) structural domain, a central kinase structural domain, and a carboxy-terminal focal adhesion targeting (FAT) structural domain (Alanko and Ivaska, 2016). ...
... FAK expression and activation are regulated by several mechanisms: at the gene level by gene amplification (Agochiya et al., 1999;Okamoto et al., 2003); at the RNA level by selective splicing (Corsi et al., 2006;Devaud et al., 2019) or FAK mRNA upregulation (Tremblay et al., 1996;Fujii et al., 2004); at the translational and post-translational levels via phosphorylation (Imaizumi et al., 1997), dephosphorylation (Hauck et al., 2001); and non-coding RNA regulation (Egawa et al., 2016;Cheng et al., 2017;Qu et al., 2017;Wang et al., 2019;Yan et al., 2019;Pan and Xie, 2020;Tang et al., 2020;Zhang et al., 2021a). FAK plays an integral role in the development of various tumors through these mechanisms. ...
... Overexpression of FAK transcripts is crucial for FAKmediated tumor cell function. The PTK2 promoter is also activated or made more active by the transcription factors NF-κB (Corsi et al., 2006), BACH1 , ETV1 , ETS1 (Tomar et al., 2018), NANOG (Ho et al., 2012), AGO2 (Cheng et al., 2013), and ETV4 , which similarly increases the expression of FAK mRNA. In contrast, P53 (Cance and Golubovskaya, 2008) and ATF3 limit some of the tumor's functions by lowering the activity of the PTK2 promoter and the number of transcripts. ...
Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase and an adaptor protein that primarily regulates adhesion signaling and cell migration. FAK promotes cell survival in response to stress. Increasing evidence has shown that at the pathological level, FAK is highly expressed in multiple tumors in several systems (including lung, liver, gastric, and colorectal cancers) and correlates with tumor aggressiveness and patient prognosis. At the molecular level, FAK promotes tumor progression mainly by altering survival signals, invasive capacity, epithelial-mesenchymal transition, the tumor microenvironment, the Warburg effect, and stemness of tumor cells. Many effective drugs have been developed based on the comprehensive role of FAK in tumor cells. In addition, its potential as a tumor marker cannot be ignored. Here, we discuss the pathological and pre-clinical evidence of the role of FAK in cancer development; we hope that these findings will assist in FAK-based clinical studies.
... In addition to its kinase-dependent activity, FAK can also complex with a number of proteins as a scaffold to enhance cell survival in a kinase-independent manner (Kleinschmidt and Schlaepfer, 2017;Yoon et al., 2015). FAK is expressed as early as gastrulation, and genetic deletions of FAK in mice result in embryonic lethality with defects in mesodermal development, specifically cardiovascular development (Corsi et al., 2006;Furuta et al., 1995;Ilic et al., 1995;Lim et al., 2010). ...
Signals from the endothelium play a pivotal role in pancreatic lineage commitment. As such, the fate of the epithelial cells relies heavily on the spatiotemporal recruitment of the endothelial cells to the embryonic pancreas. While it is known that Vegf-A secreted by the epithelium recruits the endothelial cells to the specific domains within the developing pancreas, the mechanism that controls the timing for such recruitment is poorly understood. Here, we assessed the role of focal adhesion kinase (FAK) in mouse pancreatic development based on our observation that the presence of the enzymatically active form of FAK (pFAK) in the epithelial cells is inversely correlated with vessel recruitment.
To study the role of FAK in the pancreas, we conditionally deleted the gene encoding focal adhesion kinase in the developing mouse pancreas. We found that homozygous deletion of the Fak gene during embryogenesis resulted in ectopic epithelial expression of Vefg-A, abnormal endothelial recruitment and a delay in endocrine and acinar cell differentiation. The heterozygous mutants were born with no pancreatic phenotype but displayed gradual acinar atrophy due to cell polarity defects in exocrine cells.
Together, our findings imply a role for FAK in controlling the timing of pancreatic lineage commitment/differentiation in the embryonic pancreas by preventing endothelial recruitment to the embryonic pancreatic epithelium.
... The PYK2-encoding PTK2B gene originated via the duplication and diversification of the FAK-encoding PTK2 gene in vertebrates 10 . Both protein paralogs have the same domain organisation: an N-terminal band 4.1, ezrin, radixin, moesin (FERM) domain, a tyrosine kinase domain, and a C-terminal focal adhesion targeting (FAT) domain (Fig. 1a). ...
Multidomain kinases use many ways to integrate and process diverse stimuli. Here, we investigated the mechanism by which the protein tyrosine kinase 2-beta (PYK2) functions as a sensor and effector of cellular calcium influx. We show that the linker between the PYK2 kinase and FAT domains (KFL) encompasses an unusual calmodulin (CaM) binding element. PYK2 KFL is disordered and engages CaM through an ensemble of transient binding events. Calcium increases the association by promoting structural changes in CaM that expose auxiliary interaction opportunities. KFL also forms fuzzy dimers, and dimerization is enhanced by CaM binding. As a monomer, however, KFL associates with the PYK2 FERM-kinase fragment. Thus, we identify a mechanism whereby calcium influx can promote PYK2 self-association, and hence kinase-activating trans-autophosphorylation. Collectively, our findings describe a flexible protein module that expands the paradigms for CaM binding and self-association, and their use for controlling kinase activity. Protein tyrosine kinase 2-beta is shown to function as a sensor and effector of cellular calcium influx through self-association.
... This leads to auto-phosphorylation of Tyr residue on position 379 (pY379), which leads to phosphorylation on other sites in the kinase domain and promotes FAK to take part in downstream signal transduction (Schaller and Parsons 1994;Eide et al. 1995;Calalb et al. 1995;Schlaepfer et al. 1994). FAK regulation occurs on multiple levels including transcriptional -through regulation of gene expression and alternative splicing (Corsi et al. 2006) and protein -by phosphorylation . Changes in the regulation of FAK can contribute to its enhanced activation and subsequently promote tumour advancement. ...
Papillary thyroid carcinoma (PTC), a common endocrine malignancy, presents a challenge from a prognostic standpoint. Molecular alterations underlying PTC progression include deregulation of focal adhesion kinase (FAK) at post-transcriptional and post-translational levels. Searching for candidate markers of PTC progression, we investigated the prognostic significance of FAK alterations on mRNA/protein level. The expression levels and subcellular localisation of auto-phosphorylated FAK (pY397-FAK) were determined by western blot (WB) and immunohistochemistry. The quantity of total FAK mRNA, alternatively spliced FAK-Del26 and FAK-Del33 variants were analysed by RT-qPCR and related to pY397-FAK expression and subcellular distribution. The results were correlated with clinicopathological parameters of the patients. The expression of pY397-FAK was significantly elevated in malignant samples. Active FAK showed predominant cytoplasmic distribution with co-occurrence along the membrane, while nuclear staining was found less frequently. Expression of pY397-FAK in separate cellular compartments correlated with adverse clinicopathological parameters, but the strongest association was found when their mean scores were calculated. Alternatively spliced FAK-Del33 and total FAK transcripts positively correlated to pY397-FAK protein levels as well as to characteristics of PTC advancement. Over-expression of FAK on mRNA (total and Del-33) and activated protein (pY397-FAK) levels is a feature of PTC advanced stages. Of the analysed alterations, the mean pY397-FAK IHC score showed the best predictive performance. Correlation between mRNA FAK-Del33 and pY397-FAK expression implies a regulatory role of alternative splicing in PTC patients.
... The microexon of PTK2 analyzed in the present study is exon 31, which encodes three amino acids, Pro-Trp-Arg (PWR). 27,31 It is highly conserved among vertebrates from zebrafish and fugu to chimpanzee and human, with the maintenance of 100% amino acid sequence identity, suggestive of an important physiological role. 27 The potential functional role of this microexon remains unclear, however. ...
... 27,31 It is highly conserved among vertebrates from zebrafish and fugu to chimpanzee and human, with the maintenance of 100% amino acid sequence identity, suggestive of an important physiological role. 27 The potential functional role of this microexon remains unclear, however. Although the encoded residues are located in the COOHterminal focal adhesion targeting (FAT) domain, which mediates localization of the protein to focal adhesions, exclusion of the microexon does not affect the subcellular localization of PTK2. ...
The splicing of microexons (very small exons) is frequently dysregulated in the brain of individuals with autism spectrum disorder. However, little is known of the patterns, regulatory mechanisms and roles of microexon splicing in cancer. We here examined the transcriptome‐wide profile of microexon splicing in matched colorectal cancer (CRC) and normal tissue specimens. Out of 1492 microexons comprising 3 to 15 nucleotides, 21 (1%) manifested differential splicing between CRC and normal tissue. The 21 genes harboring the differentially spliced microexons were enriched in gene ontology terms related to cell adhesion and migration. RNA interference‐mediated knockdown experiments identified two splicing factors, RBFOX2 and PTBP1, as regulators of microexon splicing in CRC cells. RBFOX2 and PTBP1 were found to directly bind to microexon‐containing pre‐mRNAs and to control their splicing in such cells. Differential microexon splicing was shown to be due, at least in part, to altered expression of RBFOX2 and PTBP1 in CRC tissue compared to matched normal tissue. Finally, we found that changes in the pattern of microexon splicing were associated with CRC metastasis. Our data thus suggest that altered expression of RBFOX2 and PTBP1 might influence CRC metastasis through the regulation of microexon splicing.
... A number of reports have ascertained the role of FAK in breast cancer showing that its expression is associated with a poor prognosis and a metastatic phenotype [14,16]. The availability and elaboration of genomic information have also allowed the identification of genetic alterations, transcriptional and post-translational modifications involved in the regulation of FAK expression [200]. For instance, the amplification of the gene encoding FAK, PTK2, has been observed in different types of tumors as the invasive breast cancer [201]. ...
Simple Summary
Breast cancer is the most common diagnosed malignancy and the main leading cause of tumor-related death among women worldwide. Thus, several studies have been carried out in order to identify valuable molecular biomarkers for the prognosis and prediction of therapeutic responses in breast tumor patients. Focal adhesion kinase (FAK) is a cytoplasmic non-receptor protein tyrosine kinase overexpressed in diverse tumors, including breast cancer. Here, we review previous evidence dealing with the role of FAK in the growth and metastatic features of breast tumors, its action as a driver of cancer stem cell phenotype and function as a mechanotransducer, and FAK activity within the breast tumor microenvironment and critical prognostic value of FAK expression in breast malignancy. In addition, we recapitulated the usefulness of FAK inhibitors in breast cancer treatment.
Abstract
Breast cancer represents the most common diagnosed malignancy and the main leading cause of tumor-related death among women worldwide. Therefore, several efforts have been made in order to identify valuable molecular biomarkers for the prognosis and prediction of therapeutic responses in breast tumor patients. In this context, emerging discoveries have indicated that focal adhesion kinase (FAK), a non-receptor tyrosine kinase, might represent a promising target involved in breast tumorigenesis. Of note, high FAK expression and activity have been tightly correlated with a poor clinical outcome and metastatic features in several tumors, including breast cancer. Recently, a role for the integrin-FAK signaling in mechanotransduction has been suggested and the function of FAK within the breast tumor microenvironment has been ascertained toward tumor angiogenesis and vascular permeability. FAK has been also involved in cancer stem cells (CSCs)-mediated initiation, maintenance and therapeutic responses of breast tumors. In addition, the potential of FAK to elicit breast tumor-promoting effects has been even associated with the capability to modulate immune responses. On the basis of these findings, several agents targeting FAK have been exploited in diverse preclinical tumor models. Here, we recapitulate the multifaceted action exerted by FAK and its prognostic significance in breast cancer. Moreover, we highlight the recent clinical evidence regarding the usefulness of FAK inhibitors in the treatment of breast tumors.
... Focal adhesion kinase (FAK), a highly conserved nonreceptor tyrosine kinase [1], is a key signalling mediator downstream of integrins, receptor tyrosine kinases, and G-protein-coupled receptors (GPCRs) [2][3][4][5]. FAK, which controls cell adhesion, polarity, motility, proliferation, and survival [6,7], plays a critical role during development and its deletion in mice results in early embryonic death [8][9][10][11][12]. ...
... This hypothesis is supported by the dose-dependent inhibition of GST-FAK autophosphorylation by recombinant β-arr2 in vitro. FAK and β-arrs are expressed at variable levels in adult tissues [1,44] and the effects of β-arrs on FAK activity likely depend on their respective concentrations. Furthermore, FAK expression and autophosphorylation are increased in several human cancers [7], whereas changes in β-arrs are triggers G-protein activation (illustrated by GDP to GTP exchange); the receptors are then phosphorylated (P) by GRKs (not shown) and recruit β-arr-FAK complexes. ...
Focal adhesion kinase (FAK) regulates key biological processes downstream of G protein-coupled receptors (GPCRs) in normal and cancer cells, but the modes of kinase activation by these receptors remain unclear. We report that after GPCR stimulation, FAK activation is controlled by a sequence of events depending on the scaffolding proteins β-arrestins and G proteins. Depletion of β-arrestins results in a marked increase in FAK autophosphorylation and focal adhesion number. We demonstrate that β-arrestins interact directly with FAK and inhibit its autophosphorylation in resting cells. Both FAK–β-arrestin interaction and FAK inhibition require the FERM domain of FAK. Following the stimulation of the angiotensin receptor AT1AR and subsequent translocation of the FAK–β-arrestin complex to the plasma membrane, β-arrestin interaction with the adaptor AP-2 releases inactive FAK from the inhibitory complex, allowing its activation by receptor-stimulated G proteins and activation of downstream FAK effectors. Release and activation of FAK in response to angiotensin are prevented by an AP-2-binding deficient β-arrestin and by a specific inhibitor of β-arrestin/AP-2 interaction; this inhibitor also prevents FAK activation in response to vasopressin. This previously unrecognized mechanism of FAK regulation involving a dual role of β-arrestins, which inhibit FAK in resting cells while driving its activation at the plasma membrane by GPCR-stimulated G proteins, opens new potential therapeutic perspectives in cancers with up-regulated FAK.
... (Fiedorek & Kay, 1995). Les facteurs NF-κB, AGo2, PEA3 et NANOG en sont les principaux promoteurs tandis que la protéine p53 est le principal répresseur (Cheng et al., 2014 ;Corsi et al., 2006 ;Ho et al., 2012 ;Li et al., 2013). Par ailleurs, quatre isoformes de FAK résultant de l'épissage alternatif ont été caractérisées (Burgaya et al., 1997) (Burgaya et al., 1997 ;Toutant et al., 2002). ...
L’invasion tumorale requière la coordination des processus de migration et de dégradation de la matrice extracellulaire (MEC), régulés respectivement par les adhérences focales et par les invadopodes, protrusions membranaires enrichies en métalloprotéases matricielles. Sur un modèle de mélanome, nous avons étudié les mécanismes moléculaires de l’invasion cellulaire sous-jacents. La protéine FAK (Focal Adhesion Kinase) régule la balance entre migration et dégradation matricielle dans les cellules cancéreuses. Nous montrons que l’inhibition du domaine kinase de FAK diminue la migration cellulaire mais augmente la dégradation matricielle. En revanche, en inhibant l’interaction FAK-paxilline, nous montrons que la migration et l’invasion tumorale sont diminuées, soulignant la pertinence d’une nouvelle stratégie thérapeutique ciblant FAK. Aussi, nous avons trouvé que l’activation du récepteur CD47 par la TSP-1 inhibe la migration mais favorise la dégradation de la MEC par la voie de signalisation MEK/ERK. Nous montrons ainsi pour la première fois l’implication directe de l’axe CD47-TSP-1 dans la formation et l’activité des invadopodes.
