scholarly journals Integrin α5β1, as a Receptor of Fibronectin, Binds the FbaA Protein of Group A Streptococcus To Initiate Autophagy during Infection

mBio ◽  
2020 ◽  
Vol 11 (3) ◽  
Author(s):  
Jiachao Wang ◽  
Meiqi Meng ◽  
Miao Li ◽  
Xiaofei Guan ◽  
Jianguo Liu ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Cell Surface ◽  
Matrix Protein ◽  
Beclin 1 ◽  
Extracellular Matrix Protein ◽  
Critical Surface ◽  
Structural Protein ◽  
Integrin Α5β1 ◽  
Potent Inducer ◽  
Group A

ABSTRACT Group A Streptococcus (GAS), one of the most common extracellular pathogens, has been reported to invade epithelial and endothelial cells. Our results reveal that M1 GAS strain SF370 can be effectively eliminated by respiratory epithelial cells. Emerging evidence indicates that autophagy is an important strategy for nonphagocytes to eliminate intracellular bacteria. Upon pathogen recognition, cell surface receptors can directly trigger autophagy, which is a critical step in controlling infection. However, the mechanisms of how cells sense invading bacteria and use this information specifically to trigger autophagy remain unclear. In this study, we stimulated cells and infected mice with M and FbaA mutants of M1 GAS strain SF370 or with purified M and FbaA proteins (two critical surface structural proteins of GAS), and found that only FbaA protein was involved in autophagy induction. Furthermore, the FbaA protein induced autophagy independent of common pattern recognition receptors (such as Toll-like receptors); rather, it relies on binding to integrin α5β1 expressed on the cell surface, which is mediated by extracellular matrix protein fibronectin (Fn). The FbaA-Fn-integrin α5β1 complex activates Beclin-1 through the mTOR-ULK1–Beclin-1 pathway, which enables the Beclin-1/Vps34 complex to recruit Rab7 and, ultimately, to promote the formation of autophagosomes. By knocking down integrin α5β1, Fn, Atg5, Beclin-1, and ULK1 in Hep2 cells and deleting Atg5 or integrin α5β1 in mice, we reveal a novel role for integrin α5β1 in inducing autophagy. Our study demonstrates that integrin α5β1, through interacting with pathogen components, initiates effective host innate immunity against invading intracellular pathogens. IMPORTANCE Autophagy is generally considered a strategy used by the innate immune system to eliminate invasive pathogens through capturing and transferring them to lysosomes. Currently, researchers pay more attention to how virulence factors secreted by GAS regulate the autophagic process. Here, we provide the first evidence that the structural protein FbaA of M1 GAS strain SF370 is a potent inducer of autophagy in epithelial cells. Furthermore, we demonstrate that integrin α5β1 in epithelial cells in vitro and in vivo acts as a receptor to initiate the signaling for inducing autophagy by binding to FbaA of M1 GAS strain SF370 via Fn. Our study reveals the underlying mechanisms by which pathogens induce Fn-integrin α5β1 to trigger autophagy in a conserved pattern in epithelial cells.

scholarly journals The Role of pkc-3 and Genetic Suppressors in Caenorhabditis elegans Epithelial Cell Junction Formation

Genetics ◽  
2020 ◽  
Vol 214 (4) ◽  
pp. 941-959 ◽  
Author(s):  
José G. Montoyo-Rosario ◽  
Stephen T. Armenti ◽  
Yuliya Zilberman ◽  
Jeremy Nance
Keyword(s):  
Caenorhabditis Elegans ◽  
Epithelial Cells ◽  
Matrix Protein ◽  
Extracellular Matrix Protein ◽  
Cell Junction ◽  
Loss Of Function ◽  
Link Type ◽  
Junction Formation ◽  
Extragenic Suppressors

Epithelial cells form intercellular junctions to strengthen cell–cell adhesion and limit diffusion, allowing epithelia to function as dynamic tissues and barriers separating internal and external environments. Junctions form as epithelial cells differentiate; clusters of junction proteins first concentrate apically, then mature into continuous junctional belts that encircle and connect each cell. In mammals and Drosophila, atypical protein kinase C (aPKC) is required for junction maturation, although how it contributes to this process is poorly understood. A role for the Caenorhabditis elegans aPKC homolog PKC-3 in junction formation has not been described previously. Here, we show that PKC-3 is essential for junction maturation as epithelia first differentiate. Using a temperature-sensitive allele of pkc-3 that causes junction breaks in the spermatheca and leads to sterility, we identify intragenic and extragenic suppressors that render pkc-3 mutants fertile. Intragenic suppressors include an unanticipated stop-to-stop mutation in the pkc-3 gene, providing evidence for the importance of stop codon identity in gene activity. One extragenic pkc-3 suppressor is a loss-of-function allele of the lethal(2) giant larvae homolog lgl-1, which antagonizes aPKC within epithelia of Drosophila and mammals, but was not known previously to function in C. elegans epithelia. Finally, two extragenic suppressors are loss-of-function alleles of sups-1—a previously uncharacterized gene. We show that SUPS-1 is an apical extracellular matrix protein expressed in epidermal cells, suggesting that it nonautonomously regulates junction formation in the spermatheca. These findings establish a foundation for dissecting the role of PKC-3 and interacting genes in epithelial junction maturation.

scholarly journals Cell surface expression of adhesins for fibronectin correlates with virulence in Sporothrix schenckii

Microbiology ◽  
2009 ◽  
Vol 155 (11) ◽  
pp. 3730-3738 ◽  
Author(s):  
Pedro Antônio Castelo Teixeira ◽  
Rafaela Alves de Castro ◽  
Rosana Cícera Nascimento ◽  
Guy Tronchin ◽  
Armando Pérez Torres ◽  
...  
Keyword(s):  
Cell Surface ◽  
Yeast Cell ◽  
Matrix Protein ◽  
Binding Capacity ◽  
Protein Pattern ◽  
Sporothrix Schenckii ◽  
Surface Expression ◽  
Extracellular Matrix Protein ◽  
Cell Surface Expression ◽  
Yeast Cell Surface

The virulence of four Sporothrix schenckii isolates was compared in a murine model of sporotrichosis, together with the protein pattern of the yeast cell surface and the capacity to bind the extracellular matrix protein fibronectin. Virulence was determined by the mortality rate, fungal burden and histopathology. Two clinical isolates were more virulent for C57BL/6 mice, but no direct correlation was seen between virulence and the clinical or environmental origin of the isolates. The lowest virulence was observed for an isolate recovered from a patient with meningeal sporotrichosis. Although all isolates could effectively disseminate, the dissemination patterns were not similar. Using flow cytometry analysis, we investigated the interaction of all the strains with fibronectin, and showed that the binding capacity correlated with virulence. Western blot analysis of S. schenckii cell wall extracts revealed positive bands for fibronectin in the range of 37–92 kDa. The 70 kDa adhesin was also recognized by a protective monoclonal antibody raised against a gp70 antigen of S. schenckii (mAb P6E7). Confocal microscopy confirmed the co-localization of fibronectin and mAb P6E7 on the yeast cell surface. To our knowledge, this is the first report identifying adhesins for fibronectin on the surface of this human pathogen.

scholarly journals Mapping the ligand-binding pocket of integrin α5β1 using a gain-of-function approach

2009 ◽  
Vol 424 (2) ◽  
pp. 179-189 ◽  
Author(s):  
A. Paul Mould ◽  
Ewa J. Koper ◽  
Adam Byron ◽  
Grit Zahn ◽  
Martin J. Humphries
Keyword(s):  
Matrix Protein ◽  
Cyclic Peptide ◽  
Therapeutic Potential ◽  
Function Analysis ◽  
Extracellular Matrix Protein ◽  
Minor Role ◽  
Gain Of Function ◽  
Integrin Α5β1 ◽  
Human Fibronectin ◽  
Human Integrin

Integrin α5β1 is a key receptor for the extracellular matrix protein fibronectin. Antagonists of human integrin α5β1 have therapeutic potential as anti-angiogenic agents in cancer and diseases of the eye. However, the structure of the integrin is unsolved and the atomic basis of fibronectin and antagonist binding by integrin α5β1 is poorly understood. In the present study, we demonstrate that zebrafish α5β1 integrins do not interact with human fibronectin or the human α5β1 antagonists JSM6427 and cyclic peptide CRRETAWAC. Zebrafish α5β1 integrins do bind zebrafish fibronectin-1, and mutagenesis of residues on the upper surface and side of the zebrafish α5 subunit β-propeller domain shows that these residues are important for the recognition of the Arg-Gly-Asp (RGD) motif and the synergy sequence [Pro-His-Ser-Arg-Asn (PHSRN)] in fibronectin. Using a gain-of-function analysis involving swapping regions of the zebrafish integrin α5 subunit with the corresponding regions of human α5 we show that blades 1–4 of the β-propeller are required for human fibronectin recognition, suggesting that fibronectin binding involves a broad interface on the side and upper face of the β-propeller domain. We find that the loop connecting blades 2 and 3 of the β-propeller, the D3–A3 loop, contains residues critical for antagonist recognition, with a minor role played by residues in neighbouring loops. A new homology model of human integrin α5β1 supports an important function for D3–A3 loop residues Trp157 and Ala158 in the binding of antagonists. These results will aid the development of reagents that block integrin α5β1 functions in vivo.

scholarly journals Matrilin-2 Is a Widely Distributed Extracellular Matrix Protein and a Potential Biomarker in the Early Stage of Osteoarthritis in Articular Cartilage

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Shukun Zhang ◽  
Jinwu Peng ◽  
Yan Guo ◽  
Sara Javidiparsijani ◽  
Guirong Wang ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Articular Cartilage ◽  
Epithelial Cells ◽  
Matrix Protein ◽  
Early Stage ◽  
Extracellular Matrix Protein ◽  
Corpus Spongiosum ◽  
Tracheal Cartilage ◽  
Potential Biomarker ◽  
Mouse Tissues

In this study, we first generated and characterized a polyclonal antibody against unique domain of matrlin-2 and then used this specific antibody to assess the expression pattern of matrilin-2 by immunohistochemistry. We found that marilin-2 is widely distributed in the connective tissues of many mouse tissues including heart, colon, penis, esophagus, lung, kidney, tracheal cartilage, developmental bone, and adult bone. The expression level of matrilin-2 was remarkably increased in the tissues of osteoarthritis developmental articular cartilage, compared to normal healthy tissues. Furthermore, we determined matrilin-2 expression in specific epithelial cells in stomach and ductal epithelial cells of salivary gland. In other tissues, the positive signals were mainly located around cardiac muscle cells and Purkinje fibers in the heart; corpus spongiosum in the penis; submucosa in the colon and esophagus; extracellular matrix of cartilage in the tracheal cartilage; and, glomerulus, the basement membrane of distal convoluted tubule and renal matrix in kidney. These observations indicated that the distribution pattern of matrilin-2 is heterogeneous in each tissue. Matrilin-2 may play an important role in the communication of matrix to matrix and matrix to cells and will be used as a potential biomarker in the early stage of osteoarthritis of articular cartilage.

scholarly journals The extracellular matrix protein Edil3 stimulates osteoblast differentiation through the integrin α5β1/ERK/Runx2 pathway

PLoS ONE ◽  
2017 ◽  
Vol 12 (11) ◽  
pp. e0188749 ◽  
Author(s):  
Sin-Hye Oh ◽  
Jung-Woo Kim ◽  
Yuri Kim ◽  
Mi Nam Lee ◽  
Min-Suk Kook ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Osteoblast Differentiation ◽  
Matrix Protein ◽  
Extracellular Matrix Protein ◽  
Integrin Α5β1

scholarly journals Integrin αVβ3 Contains a Cell Surface Receptor Site for Thyroid Hormone that Is Linked to Activation of Mitogen-Activated Protein Kinase and Induction of Angiogenesis

Endocrinology ◽  
2005 ◽  
Vol 146 (7) ◽  
pp. 2864-2871 ◽  
Author(s):  
Joel J. Bergh ◽  
Hung-Yun Lin ◽  
Lawrence Lansing ◽  
Seema N. Mohamed ◽  
Faith B. Davis ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Thyroid Hormone ◽  
Cell Surface ◽  
Matrix Protein ◽  
Integrin Αvβ3 ◽  
Recognition Site ◽  
Cell Surface Receptor ◽  
Extracellular Matrix Protein ◽  
Surface Receptor ◽  
A Cell

Abstract Integrin αVβ3 is a heterodimeric plasma membrane protein whose several extracellular matrix protein ligands contain an RGD recognition sequence. This study identifies integrin αVβ3 as a cell surface receptor for thyroid hormone [l-T4 (T4)] and as the initiation site for T4-induced activation of intracellular signaling cascades. Integrin αVβ3 dissociably binds radiolabeled T4 with high affinity, and this binding is displaced by tetraiodothyroacetic acid, αVβ3 antibodies, and an integrin RGD recognition site peptide. CV-1 cells lack nuclear thyroid hormone receptor, but express plasma membrane αVβ3; treatment of these cells with physiological concentrations of T4 activates the MAPK pathway, an effect inhibited by tetraiodothyroacetic acid, RGD peptide, and αVβ3 antibodies. Inhibitors of T4 binding to the integrin also block the MAPK-mediated proangiogenic action of T4. T4-induced phosphorylation of MAPK is inhibited by small interfering RNA knockdown of αV and β3. These findings suggest that T4 binds to αVβ3 near the RGD recognition site and show that hormone-binding to αVβ3 has physiological consequences.

scholarly journals Polarized fibronectin secretion induced by adenosine regulates bacterial–epithelial interaction in human intestinal epithelial cells

2004 ◽  
Vol 382 (2) ◽  
pp. 589-596 ◽  
Author(s):  
Baljit WALIA ◽  
Florencia E. CASTANEDA ◽  
Lixin WANG ◽  
Vasantha L. KOLACHALA ◽  
Rahul BAJAJ ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Matrix Protein ◽  
Intestinal Epithelial Cells ◽  
Cell Types ◽  
Extracellular Matrix Protein ◽  
Intestinal Epithelial ◽  
T84 Cells ◽  
Multifunctional Protein ◽  
Adenosine Receptor Antagonist ◽  
Apical Compartment

Fibronectin (FN) is a multifunctional protein that plays important roles in many biological processes including cell adhesion and migration, wound healing and inflammation. Cellular FNs are produced by a wide variety of cell types including epithelial cells, which secrete them and often organize them into extensive extracellular matrices at their basal surface. However, regulation of FN synthesis and the polarity of FN secretion by intestinal epithelial cells have not been investigated. In the present study we investigated the role of adenosine, whose levels are up-regulated during inflammation, in modulating FN synthesis, the polarity of FN secretion and the downstream effects of the secreted FN. Polarized monolayers of T84 cells were used as an intestinal epithelial model. Adenosine added to either the apical or basolateral aspect of the cells led to a time- and dose-dependent accumulation of FN in the culture supernatants, polarized to the apical compartment and reached maximal levels 24 h after apical or basolateral addition of adenosine. Confocal microscopy confirmed that FN localized to the apical domain of model intestinal epithelial cells stimulated with apical or basolateral adenosine. The induction of FN was significantly down-regulated in response to the adenosine receptor antagonist alloxazine and was inhibited by cycloheximide. Moreover, adenosine increased FN promoter activity (3.5-fold compared with unstimulated controls) indicating that FN induction is, in part, transcriptionally regulated. Interestingly, we demonstrated that adenosine, as well as apical FN, significantly enhanced the adherence and invasion of Salmonella typhimurium into cultured epithelial cells. In summary, we have shown for the first time that FN, a classic extracellular matrix protein, is secreted into the apical compartment of epithelial cells in response to adenosine. FN may be a critical host factor that modulates adherence and invasion of bacteria, thus playing a key role in mucosal immune responses during inflammation.

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