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Applied Microbiology and Biotechnology May 2023Campylobacter jejuni, causing strong enteritis, is an unusual bacterium with numerous peculiarities. Chemotactically controlled motility in viscous milieu allows... (Review)
Review
Campylobacter jejuni, causing strong enteritis, is an unusual bacterium with numerous peculiarities. Chemotactically controlled motility in viscous milieu allows targeted navigation to intestinal mucus and colonization. By phase variation, quorum sensing, extensive O-and N-glycosylation and use of the flagellum as type-3-secretion system C. jejuni adapts effectively to environmental conditions. C. jejuni utilizes proteases to open cell-cell junctions and subsequently transmigrates paracellularly. Fibronectin at the basolateral side of polarized epithelial cells serves as binding site for adhesins CadF and FlpA, leading to intracellular signaling, which again triggers membrane ruffling and reduced host cell migration by focal adhesion. Cell contacts of C. jejuni results in its secretion of invasion antigens, which induce membrane ruffling by paxillin-independent pathway. In addition to fibronectin-binding proteins, other adhesins with other target structures and lectins and their corresponding sugar structures are involved in host-pathogen interaction. Invasion into the intestinal epithelial cell depends on host cell structures. Fibronectin, clathrin, and dynein influence cytoskeletal restructuring, endocytosis, and vesicular transport, through different mechanisms. C. jejuni can persist over a 72-h period in the cell. Campylobacter-containing vacuoles, avoid fusion with lysosomes and enter the perinuclear space via dynein, inducing signaling pathways. Secretion of cytolethal distending toxin directs the cell into programmed cell death, including the pyroptotic release of proinflammatory substances from the destroyed cell compartments. The immune system reacts with an inflammatory cascade by participation of numerous immune cells. The development of autoantibodies, directed not only against lipooligosaccharides, but also against endogenous gangliosides, triggers autoimmune diseases. Lesions of the epithelium result in loss of electrolytes, water, and blood, leading to diarrhea, which flushes out mucus containing C. jejuni. Together with the response of the immune system, this limits infection time. Based on the structural interactions between host cell and bacterium, the numerous virulence mechanisms, signaling, and effects that characterize the infection process of C. jejuni, a wide variety of targets for attenuation of the pathogen can be characterized. The review summarizes strategies of C. jejuni for host-pathogen interaction and should stimulate innovative research towards improved definition of targets for future drug development. KEY POINTS: • Bacterial adhesion of Campylobacter to host cells and invasion into host cells are strictly coordinated processes, which can serve as targets to prevent infection. • Reaction and signalling of host cell depend on the cell type. • Campylobacter virulence factors can be used as targets for development of antivirulence drug compounds.
Topics: Humans; Bacterial Proteins; Campylobacter jejuni; Fibronectins; Dyneins; Virulence Factors; Adhesins, Bacterial; Epithelial Cells; Bacterial Adhesion; Campylobacter Infections
PubMed: 36941439
DOI: 10.1007/s00253-023-12456-w -
Acta Pharmaceutica Sinica. B Mar 2023The skeletal system, which contains bones, joints, tendons, ligaments and other elements, plays a wide variety of roles in body shaping, support and movement, protection... (Review)
Review
The skeletal system, which contains bones, joints, tendons, ligaments and other elements, plays a wide variety of roles in body shaping, support and movement, protection of internal organs, production of blood cells and regulation of calcium and phosphate metabolism. The prevalence of skeletal diseases and disorders, such as osteoporosis and bone fracture, osteoarthritis, rheumatoid arthritis, and intervertebral disc degeneration, increases with age, causing pain and loss of mobility and creating a huge social and economic burden globally. Focal adhesions (FAs) are macromolecular assemblies that are composed of the extracellular matrix (ECM), integrins, intracellular cytoskeleton and other proteins, including kindlin, talin, vinculin, paxillin, pinch, Src, focal adhesion kinase (FAK) and integrin-linked protein kinase (ILK) and other proteins. FA acts as a mechanical linkage connecting the ECM and cytoskeleton and plays a key role in mediating cell-environment communications and modulates important processes, such as cell attachment, spreading, migration, differentiation and mechanotransduction, in different cells in skeletal system by impacting distinct outside-in and inside-out signaling pathways. This review aims to integrate the up-to-date knowledge of the roles of FA proteins in the health and disease of skeletal system and focuses on the specific molecular mechanisms and underlying therapeutic targets for skeletal diseases.
PubMed: 36970189
DOI: 10.1016/j.apsb.2022.09.020 -
ELife Jul 2023Integrin-mediated cell attachment rapidly induces tyrosine kinase signaling. Despite years of research, the role of this signaling in integrin activation and focal...
Integrin-mediated cell attachment rapidly induces tyrosine kinase signaling. Despite years of research, the role of this signaling in integrin activation and focal adhesion assembly is unclear. We provide evidence that the Src-family kinase (SFK) substrate Cas (Crk-associated substrate, p130Cas, BCAR1) is phosphorylated and associated with its Crk/CrkL effectors in clusters that are precursors of focal adhesions. The initial phospho-Cas clusters contain integrin β1 in its inactive, bent closed, conformation. Later, phospho-Cas and total Cas levels decrease as integrin β1 is activated and core focal adhesion proteins including vinculin, talin, kindlin, and paxillin are recruited. Cas is required for cell spreading and focal adhesion assembly in epithelial and fibroblast cells on collagen and fibronectin. Cas cluster formation requires Cas, Crk/CrkL, SFKs, and Rac1 but not vinculin. Rac1 provides positive feedback onto Cas through reactive oxygen, opposed by negative feedback from the ubiquitin proteasome system. The results suggest a two-step model for focal adhesion assembly in which clusters of phospho-Cas, effectors and inactive integrin β1 grow through positive feedback prior to integrin activation and recruitment of core focal adhesion proteins.
Topics: Phosphorylation; Focal Adhesions; Phosphoproteins; Integrin beta1; Crk-Associated Substrate Protein; Protein-Tyrosine Kinases; Integrins; Focal Adhesion Protein-Tyrosine Kinases; Focal Adhesion Kinase 1
PubMed: 37489578
DOI: 10.7554/eLife.90234 -
Biology Nov 2021The cytoskeleton provides structure to cells and supports intracellular transport. Actin fibres are crucial to both functions. Focal Adhesions (FAs) are large... (Review)
Review
The cytoskeleton provides structure to cells and supports intracellular transport. Actin fibres are crucial to both functions. Focal Adhesions (FAs) are large macromolecular multiprotein assemblies at the ends of specialised actin fibres linking these to the extracellular matrix. FAs translate forces on actin fibres into forces contributing to cell migration. This review will discuss recent insights into FA protein dynamics and their organisation within FAs, made possible by advances in fluorescence imaging techniques and data analysis methods. Over the last decade, evidence has accumulated that FAs are composed of three layers parallel to the plasma membrane. We focus on some of the most frequently investigated proteins, two from each layer, paxillin and FAK (bottom, integrin signalling layer), vinculin and talin (middle, force transduction layer) and zyxin and VASP (top, actin regulatory layer). Finally, we discuss the potential impact of this layered nature on different aspects of FA behaviour.
PubMed: 34827182
DOI: 10.3390/biology10111189 -
Acta Pharmacologica Sinica Jul 2022Neurovascular unit (NVU) is organized multi-cellular and multi-component networks that are essential for brain health and brain homeostasis maintaining. Neurovascular...
Neurovascular unit (NVU) is organized multi-cellular and multi-component networks that are essential for brain health and brain homeostasis maintaining. Neurovascular unit dysfunction is the central pathogenesis process of ischemic stroke. Thus integrated protection of NVU holds great therapeutic potential for ischemic stroke. Catalpol, classified into the iridoid monosaccharide glycoside, is the main active ingredient of the radix from traditional Chinese medicine, Rehmannia glutinosa Libosch, that exhibits protective effects in several brain-related diseases. In the present study, we investigated whether catalpol exerted protective effects for NVU in ischemic stroke and the underlying mechanisms. MCAO rats were administered catalpol (2.5, 5.0, 10.0 mg·kg·d, i.v.) for 14 days. We showed that catalpol treatment dose-dependently reduced the infarction volume and significantly attenuated neurological deficits score in MCAO rats. Furthermore, catalpol treatment significantly ameliorated impaired NVU in ischemic region by protecting vessel-neuron-astrocyte structures and morphology, and promoting angiogenesis and neurogenesis to replenish lost vessels and neurons. Moreover, catalpol treatment significantly increased the expression of vascular endothelial growth factor (VEGF) through up-regulating PI3K/AKT signaling, followed by increasing FAK and Paxillin and activating PI3K/AKT and MEK1/2/ERK1/2 pathways. The protective mechanisms of catalpol were confirmed in an in vitro three-dimensional NVU model subjected to oxygen-glucose deprivation. In conclusion, catalpol protects NVU in ischemic region via activation of PI3K/AKT signaling and increased VEGF production; VEGF further enhances PI3K/AKT and MEK1/2/ERK1/2 signaling, which may trigger a partly feed-forward loop to protect NVU from ischemic stroke.
Topics: Animals; Iridoid Glucosides; Ischemic Stroke; MAP Kinase Signaling System; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Rats; Vascular Endothelial Growth Factor A
PubMed: 34795412
DOI: 10.1038/s41401-021-00803-4 -
Progress in Biophysics and Molecular... Nov 2022Actopaxin is a newly discovered focal adhesions (FAs) protein, actin-binding protein and pseudopodia-enriched molecule. It can not only bind to a variety of FAs proteins... (Review)
Review
Actopaxin is a newly discovered focal adhesions (FAs) protein, actin-binding protein and pseudopodia-enriched molecule. It can not only bind to a variety of FAs proteins (such as Paxillin, ILK and PINCH) and non-FAs proteins (such as TESK1, CdGAP, β2-adaptin, G3BP2, ADAR1 and CD29), but also participates in multiple signaling pathways. Thus, it plays a crucial role in regulating important processes of tumor metastasis, including matrix degradation, migration, and invasion, etc. This review covers the latest progress in the structure and function of Actopaxin, its interaction with other proteins as well as its involvement in regulating tumor development and metastasis. Additionally, the current limitations for Actopaxin related studies and the possible research directions on it in the future are also discussed. It is hoped that this review can assist relevant researchers to obtain a deep understanding of the role that Actopaxin plays in tumor progression, and also enlighten further research and development of therapeutic approaches for the treatment of tumor metastasis.
Topics: Humans; Actinin; Cell Movement; Focal Adhesions; Microfilament Proteins; Neoplasms
PubMed: 36150525
DOI: 10.1016/j.pbiomolbio.2022.09.006 -
Frontiers in Cell and Developmental... 2023Cancer progression and metastasis are processes heavily controlled by the integrin receptor family. Integrins are cell adhesion molecules that constitute the central... (Review)
Review
Cancer progression and metastasis are processes heavily controlled by the integrin receptor family. Integrins are cell adhesion molecules that constitute the central components of mechanosensing complexes called focal adhesions, which connect the extracellular environment with the cell interior. Focal adhesions act as key players in cancer progression by regulating biological processes, such as cell migration, invasion, proliferation, and survival. Src family kinases (SFKs) can interplay with integrins and their downstream effectors. SFKs also integrate extracellular cues sensed by integrins and growth factor receptors (GFR), transducing them to coordinate metastasis and cell survival in cancer. The non-receptor tyrosine kinase CSK is a well-known SFK member that suppresses SFK activity by phosphorylating its specific negative regulatory loop (C-terminal Y residue). Consequently, CSK may play a pivotal role in tumour progression and suppression by inhibiting SFK oncogenic effects in several cancer types. Remarkably, CSK can localise near focal adhesions when SFKs are activated and even interact with focal adhesion components, such as phosphorylated FAK and Paxillin, among others, suggesting that CSK may regulate focal adhesion dynamics and structure. Even though SFK oncogenic signalling has been extensively described before, the specific role of CSK and its crosstalk with integrins in cancer progression, for example, in mechanosensing, remain veiled. Here, we review how CSK, by regulating SFKs, can regulate integrin signalling, and focus on recent discoveries of mechanotransduction. We additionally examine the cross talk of integrins and GFR as well as the membrane availability of these receptors in cancer. We also explore new pharmaceutical approaches to these signalling pathways and analyse them as future therapeutic targets.
PubMed: 37519303
DOI: 10.3389/fcell.2023.1214787 -
American Journal of Physiology.... Mar 2020PAK4 is the only member of the Group II p21-activated kinases (PAKs) present in rat pancreatic acinar cells and is activated by gastrointestinal...
PAK4 is the only member of the Group II p21-activated kinases (PAKs) present in rat pancreatic acinar cells and is activated by gastrointestinal hormones/neurotransmitters stimulating PLC/cAMP and by various pancreatic growth factors. However, little is known of the role of PAK4 activation in cellular signaling cascades in pancreatic acinar cells. In the present study, we examined the role of PAK4's participation in five different cholecystokinin-8 (CCK-8)-stimulated signaling pathways (PI3K/Akt, MAPK, focal adhesion kinase, GSK3, and β-catenin), which mediate many of its physiological acinar-cell effects, as well as effects in pathophysiological conditions. To define PAK4's role, the effect of two different PAK4 inhibitors, PF-3758309 and LCH-7749944, was examined under experimental conditions that only inhibited PAK4 activation and not activation of the other pancreatic PAK, Group I PAK2. The inhibitors' effects on activation of these five signaling cascades by both physiological and pathophysiological concentrations of CCK, as well as by 12--tetradecanoylphobol-13-acetate (TPA), a PKC-activator, were examined. CCK/TPA activation of focal adhesion kinases(PYK2/p125) and the accompanying adapter proteins (paxillin/p130), Mek1/2, and p44/42, but not c-Raf or other MAPKs (JNK/p38), were mediated by PAK4. Activation of PI3K/Akt/p70s6K was independent of PAK4, whereas GSK3 and β-catenin stimulation was PAK4-dependent. These results, coupled with recent studies showing PAK4 is important in pancreatic fluid/electrolyte/enzyme secretion and acinar cell growth, show that PAK4 plays an important role in different cellular signaling cascades, which have been shown to mediate numerous physiological and pathophysiological processes in pancreatic acinar cells. In pancreatic acinar cells, cholecystokinin (CCK) or 12--tetradecanoylphobol-13-acetate (TPA) activation of focal adhesion kinases (p125,PYK2) and its accompanying adapter proteins, p130CAS/paxillin; Mek1/2, p44/42, GSK3, and β-catenin are mediated by PAK4. PI3K/Akt/p70s6K, c-Raf, JNK, or p38 pathways are independent of PAK4 activation.
Topics: Acinar Cells; Animals; Crk-Associated Substrate Protein; Enzyme Activation; Enzyme Activators; Extracellular Signal-Regulated MAP Kinases; Focal Adhesion Kinase 1; Focal Adhesion Kinase 2; Glycogen Synthase Kinase 3; Male; Mitogen-Activated Protein Kinase Kinases; Pancreas, Exocrine; Paxillin; Protein Kinase Inhibitors; Rats, Sprague-Dawley; Signal Transduction; beta Catenin; p21-Activated Kinases
PubMed: 31984786
DOI: 10.1152/ajpgi.00229.2019 -
EMBO Reports Nov 2023The remodeling and stiffening of the extracellular matrix (ECM) is a well-recognized modulator of breast cancer progression. How changes in the mechanical properties of...
The remodeling and stiffening of the extracellular matrix (ECM) is a well-recognized modulator of breast cancer progression. How changes in the mechanical properties of the ECM are converted into biochemical signals that direct tumor cell migration and metastasis remain poorly characterized. Here, we describe a new role for the autophagy-inducing serine/threonine kinases ULK1 and ULK2 in mechanotransduction. We show that ULK1/2 activity inhibits the assembly of actin stress fibers and focal adhesions (FAs) and as a consequence impedes cell contraction and migration, independent of its role in autophagy. Mechanistically, we identify PXN/paxillin, a key component of the mechanotransducing machinery, as a direct binding partner and substrate of ULK1/2. ULK-mediated phosphorylation of PXN at S32 and S119 weakens homotypic interactions and liquid-liquid phase separation of PXN, impairing FA assembly, which in turn alters the mechanical properties of breast cancer cells and their response to mechanical stimuli. ULK1/2 and the well-characterized PXN regulator, FAK/Src, have opposing functions on mechanotransduction and compete for phosphorylation of adjacent serine and tyrosine residues. Taken together, our study reveals ULK1/2 as important regulator of PXN-dependent mechanotransduction.
Topics: Humans; Female; Paxillin; Breast Neoplasms; Mechanotransduction, Cellular; Phosphorylation; Cell Movement; Serine; Autophagy-Related Protein-1 Homolog; Intracellular Signaling Peptides and Proteins
PubMed: 37846507
DOI: 10.15252/embr.202356850 -
Biochimica Et Biophysica Acta. Proteins... Oct 2022Paxillin is one of the most important adapters in integrin-mediated adhesions that performs numerous crucial functions relying on its dynamic interactions. Its... (Review)
Review
Paxillin is one of the most important adapters in integrin-mediated adhesions that performs numerous crucial functions relying on its dynamic interactions. Its structural behavior serves different purposes, providing a base for several activities. The various domains of paxillin display different functions in the whole process of cell movements and have a significant role in cell adhesion, migration, signal transmission, and protein-protein interactions. On the other hand, some paxillin-associated proteins provide a unique spatiotemporal mechanism for regulating its dynamic characteristics in the tissue homeostasis and make it a more complex and decisive protein at the focal adhesions. This review briefly describes the structural adaptations and molecular mechanisms of recruitment of paxillin into adhesions, explains paxillin's binding dynamics and impact on adhesion stability and turnover, and reveals a variety of paxillin-associated regulatory mechanisms and how paxillin is embedded into the signaling networks.
Topics: Cell Adhesion; Cell Movement; Focal Adhesions; Paxillin; Signal Transduction
PubMed: 35926716
DOI: 10.1016/j.bbapap.2022.140825