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Davis-Lunn M, Goult BT, Andrews MR. Clutching at Guidance Cues: The Integrin-FAK Axis Steers Axon Outgrowth. BIOLOGY 2023; 12:954. [PMID: 37508384 PMCID: PMC10376711 DOI: 10.3390/biology12070954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 06/27/2023] [Accepted: 06/30/2023] [Indexed: 07/30/2023]
Abstract
Integrin receptors are essential contributors to neurite outgrowth and axon elongation. Activated integrins engage components of the extracellular matrix, enabling the growth cone to form point contacts, which connect the extracellular substrate to dynamic intracellular protein complexes. These adhesion complexes facilitate efficient growth cone migration and neurite extension. Major signalling pathways mediated by the adhesion complex are instigated by focal adhesion kinase (FAK), whilst axonal guidance molecules present in vivo promote growth cone turning or retraction by local modulation of FAK activity. Activation of FAK is marked by phosphorylation following integrin engagement, and this activity is tightly regulated during neurite outgrowth. FAK inhibition slows neurite outgrowth by reducing point contact turnover; however, mutant FAK constructs with enhanced activity stimulate aberrant outgrowth. Importantly, FAK is a major structural component of maturing adhesion sites, which provide the platform for actin polymerisation to drive leading edge advance. In this review, we discuss the coordinated signalling of integrin receptors and FAK, as well as their role in regulating neurite outgrowth and axon elongation. We also discuss the importance of the integrin-FAK axis in vivo, as integrin expression and activation are key determinants of successful axon regeneration following injury.
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Affiliation(s)
- Mathew Davis-Lunn
- Faculty of Environmental and Life Sciences, University of Southampton, Southampton SO17 1BJ, UK
| | - Benjamin T Goult
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK
| | - Melissa R Andrews
- Faculty of Environmental and Life Sciences, University of Southampton, Southampton SO17 1BJ, UK
- Centre for Human Development, Stem Cells and Regeneration, School of Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK
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2
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Criss ZK, Bhasin N, Di Rienzi SC, Rajan A, Deans-Fielder K, Swaminathan G, Kamyabi N, Zeng XL, Doddapaneni H, Menon VK, Chakravarti D, Estrella C, Yu X, Patil K, Petrosino JF, Fleet JC, Verzi MP, Christakos S, Helmrath MA, Arimura S, DePinho RA, Britton RA, Maresso AW, Grande-Allen KJ, Blutt SE, Crawford SE, Estes MK, Ramani S, Shroyer NF. Drivers of transcriptional variance in human intestinal epithelial organoids. Physiol Genomics 2021; 53:486-508. [PMID: 34612061 DOI: 10.1152/physiolgenomics.00061.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Human intestinal epithelial organoids (enteroids and colonoids) are tissue cultures used for understanding the physiology of the human intestinal epithelium. Here, we explored the effect on the transcriptome of common variations in culture methods, including extracellular matrix substrate, format, tissue segment, differentiation status, and patient heterogeneity. RNA-sequencing datasets from 276 experiments performed on 37 human enteroid and colonoid lines from 29 patients were aggregated from several groups in the Texas Medical Center. DESeq2 and gene set enrichment analysis (GSEA) were used to identify differentially expressed genes and enriched pathways. PERMANOVA, Pearson's correlation, and dendrogram analysis of the data originally indicated three tiers of influence of culture methods on transcriptomic variation: substrate (collagen vs. Matrigel) and format (3-D, transwell, and monolayer) had the largest effect; segment of origin (duodenum, jejunum, ileum, colon) and differentiation status had a moderate effect; and patient heterogeneity and specific experimental manipulations (e.g., pathogen infection) had the smallest effect. GSEA identified hundreds of pathways that varied between culture methods, such as IL1 cytokine signaling enriched in transwell versus monolayer cultures and E2F target genes enriched in collagen versus Matrigel cultures. The transcriptional influence of the format was furthermore validated in a synchronized experiment performed with various format-substrate combinations. Surprisingly, large differences in organoid transcriptome were driven by variations in culture methods such as format, whereas experimental manipulations such as infection had modest effects. These results show that common variations in culture conditions can have large effects on intestinal organoids and should be accounted for when designing experiments and comparing results between laboratories. Our data constitute the largest RNA-seq dataset interrogating human intestinal epithelial organoids.
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Affiliation(s)
- Zachary K Criss
- Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Nobel Bhasin
- Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Sara C Di Rienzi
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Anubama Rajan
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Kali Deans-Fielder
- Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | | | | | - Xi-Lei Zeng
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Harsha Doddapaneni
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas
| | - Vipin K Menon
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas
| | - Deepavali Chakravarti
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Clarissa Estrella
- Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Xiaomin Yu
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Ketki Patil
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Joseph F Petrosino
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - James C Fleet
- Department of Nutrition Sciences, The University of Texas, Austin, Texas
| | - Michael P Verzi
- Department of Genetics, Rutgers University, Piscataway, New Jersey
| | - Sylvia Christakos
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers-New Jersey Medical School, Newark, New Jersey
| | - Michael A Helmrath
- Department of Pediatric General and Thoracic Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Sumimasa Arimura
- Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Ronald A DePinho
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Robert A Britton
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Anthony W Maresso
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | | | - Sarah E Blutt
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Sue E Crawford
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Mary K Estes
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Sasirekha Ramani
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Noah F Shroyer
- Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine, Houston, Texas
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Simmen S, Maane M, Rogler S, Baebler K, Lang S, Cosin-Roger J, Atrott K, Frey-Wagner I, Spielmann P, Wenger RH, Weder B, Zeitz J, Vavricka SR, Rogler G, de Vallière C, Hausmann M, Ruiz PA. Hypoxia Reduces the Transcription of Fibrotic Markers in the Intestinal Mucosa. Inflamm Intest Dis 2021; 6:87-100. [PMID: 34124180 DOI: 10.1159/000513061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Accepted: 10/08/2020] [Indexed: 11/19/2022] Open
Abstract
Introduction Intestinal fibrosis, characterized by excessive deposition of extracellular matrix proteins, is a common and severe clinical complication of inflammatory bowel disease (IBD). However, the mechanisms underlying fibrosis remain elusive, and currently, there are limited effective pharmacologic treatments that target the development of fibrosis. Hypoxia is one of the key microenvironmental factors influencing intestinal inflammation and has been linked to fibrosis. Objective In the present study, we sought to elucidate the impact of hypoxia on fibrotic gene expression in the intestinal mucosa. Methods Human volunteers, IBD patients, and dextran sulphate sodium-treated mice were exposed to hypoxia, and colonic biopsies were collected. The human intestinal epithelial cell line Caco-2, human THP-1 macrophages, and primary human gut fibroblasts were subjected to hypoxia, and changes in fibrotic gene expression were assessed. Results Human volunteers subjected to hypoxia presented reduced transcriptional levels of fibrotic and epithelial-mesenchymal transition markers in the intestinal mucosa. IBD patients showed a trend towards a decrease in tissue inhibitor of metalloproteinase 1 protein expression. In mice, hypoxic conditions reduced the colonic expression of several collagens and matrix metalloproteinases. Hypoxic Caco-2 cells, THP-1 cells, and primary gut fibroblasts showed a significant downregulation in the expression of fibrotic and tissue remodelling factors. Conclusions Stabilization of hypoxia-inducible factors might represent a novel therapeutic approach for the treatment of IBD-associated fibrosis.
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Affiliation(s)
- Simona Simmen
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
| | - Max Maane
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
| | - Sarah Rogler
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
| | - Katherina Baebler
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
| | - Silvia Lang
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
| | - Jesus Cosin-Roger
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
| | - Kirstin Atrott
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
| | - Isabelle Frey-Wagner
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
| | - Partick Spielmann
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland
| | - Roland H Wenger
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland
| | - Bruce Weder
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
| | - Jonas Zeitz
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland.,Center of Gastroenterology, Clinic Hirslanden, Zurich, Switzerland
| | - Stephan R Vavricka
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
| | - Gerhard Rogler
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland
| | - Cheryl de Vallière
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
| | - Martin Hausmann
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
| | - Pedro A Ruiz
- Department of Gastroenterology and Hepatology, University of Zurich, Zurich, Switzerland
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Nikulin SV, Poloznikov AA, Sakharov DA. A method for rapid generation of model intestinal barriers in vitro. BULLETIN OF RUSSIAN STATE MEDICAL UNIVERSITY 2020. [DOI: 10.24075/brsmu.2020.077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To increase the efficiency of drug development process, it is important to improve performance of preclinical experiments. A major drawback of the currently used in vitro intestinal barrier models is that it takes a significant time to obtain functional enterocyte monolayers with formed tight junctions. In this work, we have optimized various parameters such as cell density and different coatings, for a more rapid and efficient producing Caco-2 cell monolayers suitable for further experiments. In vivo microscopy and impedance spectroscopy were used to monitor cells state under various conditions. To determine possible biological mechanisms affected by exposure to various protein substrates, the transcriptomic analysis was applied. It was shown that collagen IV coating of the cell growth substrate significantly increased the rate of proliferation and migration of Caco-2 cells. This effect allows forming a functional monolayer of epithelial cells with tight junctions within 24 hours. Optimally, the initial cell density should be 90,000 to 200,000 cells/cm2. It was observed that collagen IV was poorly expressed by Caco-2 cells while the collagen IV receptor was expressed at a relatively high level in these cells. Laminin-332, another basement membrane component, was found to have no significant effect on times of formation of functional epithelial monolayers. Thus, using the optimal parameters determined in this study allows to significantly improve efficiency of using the in vitro intestinal barrier models.
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Affiliation(s)
- SV Nikulin
- National Research University Higher School of Economics, Moscow, Russia; SRC Bioclinicum, Moscow, Russia
| | - AA Poloznikov
- National Research University Higher School of Economics, Moscow, Russia
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Zong D, Jiang N, Xu JH, Wang DJ, Zhu HF, Wu LR, Chen C, Yin L, He X. ZNF488 is an independent prognostic indicator in nasopharyngeal carcinoma and promotes cell adhesion and proliferation via collagen IV/FAK/AKT/Cyclin D1 pathway. Cancer Manag Res 2019; 11:5871-5882. [PMID: 31303793 PMCID: PMC6605772 DOI: 10.2147/cmar.s200001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Accepted: 05/17/2019] [Indexed: 12/22/2022] Open
Abstract
Background: ZNF488 acts as an oncogene which promotes cell invasion and endows tumor cells stem cell capacity in nasopharyngeal carcinoma (NPC), but its correlation with clinicopathologic characteristics and patients' survival in NPC remain undefined. Methods: In this study, 158 cases of confirmed NPC were subjected to immunohistochemistry staining for evaluating endogenous expression. Kaplan-Meier method and log-rank test were used to estimate the survival rates. The relationship between ZNF488 and clinicopathological characteristics was statistically calculated by chi-squared test, univariate and multivariate analysis. In addition, adhesion assay, MTT and colony formation assays were performed for measuring adhesion and proliferation capacity. Cell cycle analysis via flow cytometry was conducted to explore cell cycle distribution. Western blot was used to detect pathway protein levels, and the pFAK (Y397) kit was used for focal adhesion kinase (FAK) activation. Results: We demonstrated that high expression of ZNF488 was significantly correlated with locoregional failure (P=0.018) and distant metastasis (P=0.001). Patients with high ZNF488 expression had poorer overall survival (P<0.001), loco-regional recurrence-free survival (P<0.001), distance metastasis-free survival (P<0.001) and progression-free survival (P<0.001) than those with low ZNF488 group. Multivariate analysis showed that ZNF488 expression was an independent prognostic indicator for predicting NPC patients' survival (HR, 3.314; 95% CI, 1.489-7.386; P=0.003). Additionally, ZNF488-induced collagen IV/FAK/AKT to enhance adhesion ability meanwhile led to the upregulation of Cyclin D1 to facilitate cell proliferation through promoting cell cycle progression and inhibition of apoptosis through caspase-independent way. Conclusion: These results reveal that ZNF488, as an independent prognostic indicator, promotes cell adhesion and proliferation through collagen IV/FAK/AKT/Cyclin D1 pathway in NPC.
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Affiliation(s)
- Dan Zong
- Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province 210009, People's Republic of China
| | - Ning Jiang
- Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province 210009, People's Republic of China
| | - Jian-Hua Xu
- Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province 210009, People's Republic of China
| | - De-Jun Wang
- Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province 210009, People's Republic of China
| | - Huan-Feng Zhu
- Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province 210009, People's Republic of China
| | - Li-Rong Wu
- Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province 210009, People's Republic of China
| | - Cheng Chen
- Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province 210009, People's Republic of China
| | - Li Yin
- Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province 210009, People's Republic of China
| | - Xia He
- Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu Province 210009, People's Republic of China
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Extracellular matrix-mediated cellular communication in the heart. J Mol Cell Cardiol 2016; 91:228-37. [PMID: 26778458 DOI: 10.1016/j.yjmcc.2016.01.011] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 01/10/2016] [Accepted: 01/11/2016] [Indexed: 01/13/2023]
Abstract
The extracellular matrix (ECM) is a complex and dynamic scaffold that maintains tissue structure and dynamics. However, the view of the ECM as an inert architectural support has been increasingly challenged. The ECM is a vibrant meshwork, a crucial organizer of cellular microenvironments. It plays a direct role in cellular interactions regulating cell growth, survival, spreading, proliferation, differentiation and migration through the intricate relationship among cellular and acellular tissue components. This complex interrelationship preserves cardiac function during homeostasis; however it is also responsible for pathologic remodeling following myocardial injury. Therefore, enhancing our understanding of this cross-talk may provide mechanistic insights into the pathogenesis of heart failure and suggest new approaches to novel, targeted pharmacologic therapies. This review explores the implications of ECM-cell interactions in myocardial cell behavior and cardiac function at baseline and following myocardial injury.
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Zhang X, Moore SW, Iskratsch T, Sheetz MP. N-WASP-directed actin polymerization activates Cas phosphorylation and lamellipodium spreading. J Cell Sci 2014; 127:1394-405. [PMID: 24481817 DOI: 10.1242/jcs.134692] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Tyrosine phosphorylation of the substrate domain of Cas (CasSD) correlates with increased cell migration in healthy and diseased cells. Here, we address the mechanism leading to the phosphorylation of CasSD in the context of fibronectin-induced early spreading of fibroblasts. We have previously demonstrated that mechanical stretching of CasSD exposes phosphorylation sites for Src family kinases (SFKs). Surprisingly, phosphorylation of CasSD was independent of myosin contractile activity but dependent on actin polymerization. Furthermore, we found that CasSD phosphorylation in the early stages of cell spreading required: (1) integrin anchorage and integrin-mediated activation of SFKs, (2) association of Cas with focal adhesion kinase (FAK), and (3) N-WASP-driven actin-assembly activity. These findings, and analyses of the interactions of the Cas domains, indicate that the N-terminus of Cas associates with the FAK-N-WASP complex at the protrusive edge of the cell and that the C-terminus of Cas associates with the immobilized integrin-SFK cluster. Thus, extension of the leading edge mediated by actin polymerization could stretch Cas during early cell spreading, priming it for phosphorylation.
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Affiliation(s)
- Xian Zhang
- Department of Biological Sciences, Columbia University, 1212 Amsterdam Avenue, New York, NY 10027, USA
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Yu LCH, Wang JT, Wei SC, Ni YH. Host-microbial interactions and regulation of intestinal epithelial barrier function: From physiology to pathology. World J Gastrointest Pathophysiol 2012; 3:27-43. [PMID: 22368784 PMCID: PMC3284523 DOI: 10.4291/wjgp.v3.i1.27] [Citation(s) in RCA: 156] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Revised: 10/04/2011] [Accepted: 02/08/2012] [Indexed: 02/06/2023] Open
Abstract
The gastrointestinal tract is the largest reservoir of commensal bacteria in the human body, providing nutrients and space for the survival of microbes while concurrently operating mucosal barriers to confine the microbial population. The epithelial cells linked by tight junctions not only physically separate the microbiota from the lamina propria, but also secrete proinflammatory cytokines and reactive oxygen species in response to pathogen invasion and metabolic stress and serve as a sentinel to the underlying immune cells. Accumulating evidence indicates that commensal bacteria are involved in various physiological functions in the gut and microbial imbalances (dysbiosis) may cause pathology. Commensal bacteria are involved in the regulation of intestinal epithelial cell turnover, promotion of epithelial restitution and reorganization of tight junctions, all of which are pivotal for fortifying barrier function. Recent studies indicate that aberrant bacterial lipopolysaccharide-mediated signaling in gut mucosa may be involved in the pathogenesis of chronic inflammation and carcinogenesis. Our perception of enteric commensals has now changed from one of opportunistic pathogens to active participants in maintaining intestinal homeostasis. This review attempts to explain the dynamic interaction between the intestinal epithelium and commensal bacteria in disease and health status.
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Owen KA, Abshire MY, Tilghman RW, Casanova JE, Bouton AH. FAK regulates intestinal epithelial cell survival and proliferation during mucosal wound healing. PLoS One 2011; 6:e23123. [PMID: 21887232 PMCID: PMC3160839 DOI: 10.1371/journal.pone.0023123] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Accepted: 07/11/2011] [Indexed: 12/29/2022] Open
Abstract
Background Following damage to the intestinal epithelium, restoration of epithelial barrier integrity is triggered by a robust proliferative response. In other tissues, focal adhesion kinase (FAK) regulates many of the cellular processes that are critical for epithelial homeostasis and restitution, including cell migration, proliferation and survival. However, few studies to date have determined how FAK contributes to mucosal wound healing in vivo. Methodology and Principal Findings To examine the role of FAK in intestinal epithelial homeostasis and during injury, we generated intestinal epithelium (IE)-specific conditional FAK knockout mice. Colitis was induced with dextran-sulfate-sodium (DSS) and intestinal tissues were analyzed by immunohistochemistry and immunoblotting. While intestinal development occurred normally in mice lacking FAK, FAK-deficient animals were profoundly susceptible to colitis. The loss of epithelial FAK resulted in elevated p53 expression and an increased sensitivity to apoptosis, coincident with a failure to upregulate epithelial cell proliferation. FAK has been reported to function as a mechanosensor, inducing cyclin D1 expression and promoting cell cycle progression under conditions in which tissue/matrix stiffness is increased. Collagen deposition, a hallmark of inflammatory injury resulting in increased tissue rigidity, was observed in control and FAK knockout mice during colitis. Despite this fibrotic response, the colonic epithelium in FAK-deficient mice exhibited significantly reduced cyclin D1 expression, suggesting that proliferation is uncoupled from fibrosis in the absence of FAK. In support of this hypothesis, proliferation of Caco-2 cells increased proportionally with matrix stiffness in vitro only under conditions of normal FAK expression; FAK depleted cells exhibited reduced proliferation concomitant with attenuated cyclin D1 expression. Conclusions In the colon, FAK functions as a regulator of epithelial cell survival and proliferation under conditions of mucosal injury and a mechanosensor of tissue compliance, inducing repair-driven proliferation in the colonic epithelium through upregulation of cyclin D1.
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Affiliation(s)
- Katherine A. Owen
- Department of Cell Biology, University of Virginia Health System, Charlottesville, Virginia, United States of America
| | - Michelle Y. Abshire
- Department of Microbiology, University of Virginia Health System, Charlottesville, Virginia, United States of America
| | - Robert W. Tilghman
- Department of Microbiology, University of Virginia Health System, Charlottesville, Virginia, United States of America
| | - James E. Casanova
- Department of Cell Biology, University of Virginia Health System, Charlottesville, Virginia, United States of America
- Department of Microbiology, University of Virginia Health System, Charlottesville, Virginia, United States of America
- * E-mail: (AHB); (JEC)
| | - Amy H. Bouton
- Department of Microbiology, University of Virginia Health System, Charlottesville, Virginia, United States of America
- * E-mail: (AHB); (JEC)
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