Paxillin comes of age

Phytoconstituent-derived zingerone nanoparticles disrupt the cell adhesion mechanism and suppress cell motility in melanoma B16F10 cells

Combining phytochemicals and nanotechnology to improve the unfavorable innate properties of phytochemicals and develop them into potent nanomedicines to enhance antitumor efficacy has become a novel strategy for cancer chemoprevention. Melanoma is the most aggressive, metastatic, and deadly disease of the primary cutaneous neoplasms. In this study, we fabricated phytoconstituent-derived zingerone nanoparticles (NPs) and validated their effects on cell adhesion and motility in melanoma B16F10 cells. Our data indicated that zingerone NPs significantly induced cytotoxicity and anti-colony formation and inhibited cell migration and invasion. Moreover, zingerone NPs dramatically interfered with the cytoskeletal reorganization and markedly delayed the period of cell adhesion. Our results also revealed that zingerone NPs-mediated downregulation of MMPs (matrix metalloproteinases) activity is associated with inhibiting cell adhesion and motility. We further evaluated the effects of zingerone NPs on Src/FAK /Paxillin signaling, our data showed that zingerone NPs significantly inhibited the protein activities of Src, FAK, and Paxillin, indicating that they play important roles in zingerone NP-mediated anti-motility and anti-invasion in melanoma cells. Accordingly, the phytoconstituent-zingerone NPs can strengthen the inhibition of tumor growth, invasion, and metastasis in malignant melanoma. Altogether, these multi-pharmacological benefits of zingerone NPs will effectively achieve the purpose of melanoma prevention and invasion inhibition.

A comparative analysis of paxillin and Hic-5 proximity interactomes

Focal adhesions serve as structural and signaling hubs, facilitating bidirectional communication at the cell-extracellular matrix interface. Paxillin and the related Hic-5 (TGFβ1i1) are adaptor/scaffold proteins that recruit numerous structural and regulatory proteins to focal adhesions, where they perform both overlapping and discrete functions. In this study, paxillin and Hic-5 were expressed in U2OS osteosarcoma cells as biotin ligase (BioID2) fusion proteins and used as bait proteins for proximity-dependent biotinylation in order to directly compare their respective interactomes. The fusion proteins localized to both focal adhesions and the centrosome, resulting in biotinylation of components of each of these structures. Biotinylated proteins were purified and analyzed by mass spectrometry. The list of proximity interactors for paxillin and Hic-5 comprised numerous shared core focal adhesion proteins that likely contribute to their similar functions in cell adhesion and migration, as well as proteins unique to paxillin and Hic-5 that have been previously localized to focal adhesions, the centrosome, or the nucleus. Western blotting confirmed biotinylation and enrichment of FAK and vinculin, known interactors of Hic-5 and paxillin, as well as several potentially unique proximity interactors of Hic-5 and paxillin, including septin 7 and ponsin, respectively. Further investigation into the functional relationship between the unique interactors and Hic-5 or paxillin may yield novel insights into their distinct roles in cell migration.

Ex vivo expansion in a clinical grade medium, containing growth factors from human platelets, enhances migration capacity of adipose stem cells

Introduction

Adipose tissue mesenchymal stem/stromal cells (ASC) can be used as advanced therapy medicinal product in regenerative and cancer medicine. We previously demonstrated Supernatant Rich in Growth Factors (SRGF) can replace fetal bovine serum (FBS) to expand ASC by a clinical grade compliant protocol. The therapeutic potential of ASC is based also on their homing capacity toward inflammatory/cancer sites: oriented cell migration is a fundamental process in this scenario. We investigated the impact of SRGF on ASC migration properties.

Methods

The motility/migration potential of ASC expanded in 5% SRGF was analyzed, in comparison to 10% FBS, by standard wound healing, bidimensional chemotaxis and transwell assays, and by millifluidic transwell tests. Mechanisms involved in the migration process were investigated by transient protein overexpression.

Results

In comparison to standard 10% FBS, supplementation of the cell culture medium with 5% SRGF, strongly increased migration properties of ASC along the chemotactic gradient and toward cancer cell derived soluble factors, both in static and millifluidic conditions. We showed that, independently from applied migratory stimulus, SRGF expanded ASC were characterized by far lower expression of α-smooth muscle actin (αSMA), a protein involved in the cell migration machinery. Overexpression of αSMA induced a significant and marked decrease in migration capacity of SRGF expanded ASC.

Discussion

In conclusion, 5% SRGF addition in the cell culture medium increases the migration potential of ASC, reasonably through appropriate downregulation of αSMA. Thus, SRGF could potentially improve the therapeutic impact of ASC, both as modulators of the immune microenviroment or as targeted drug delivery vehicles in oncology.

Paxillin phase separation promotes focal adhesion assembly and integrin signaling

Focal adhesions (FAs) are transmembrane protein assemblies mediating cell-matrix connection. Although protein liquid-liquid phase separation (LLPS) has been tied to the organization and dynamics of FAs, the underlying mechanisms remain unclear. Here, we experimentally tune the LLPS of PXN/Paxillin, an essential scaffold protein of FAs, by utilizing a light-inducible Cry2 system in different cell types. In addition to nucleating FA components, light-triggered PXN LLPS potently activates integrin signaling and subsequently accelerates cell spreading. In contrast to the homotypic interaction-driven LLPS of PXN in vitro, PXN condensates in cells are associated with the plasma membrane and modulated by actomyosin contraction and client proteins of FAs. Interestingly, non-specific weak intermolecular interactions synergize with specific molecular interactions to mediate the multicomponent condensation of PXN and are efficient in promoting FA assembly and integrin signaling. Thus, our data establish an active role of the PXN phase transition into a condensed membrane-associated compartment in promoting the assembly/maturation of FAs.

Hic-5 regulates extracellular matrix-associated gene expression and cytokine secretion in cancer associated fibroblasts

The focal adhesion protein, Hic-5 plays a key role in promoting extracellular matrix deposition and remodeling by cancer associated fibroblasts within the tumor stroma to promote breast tumor cell invasion. However, whether stromal matrix gene expression is regulated by Hic-5 is still unknown. Utilizing a constitutive Hic-5 knockout, Mouse Mammary Tumor Virus-Polyoma Middle T-Antigen spontaneous breast tumor mouse model, bulk RNAseq analysis was performed on cancer associated fibroblasts isolated from Hic-5 knockout mammary tumors. Functional network analysis highlighted a key role for Hic-5 in extracellular matrix organization, with both structural matrix genes, as well as matrix remodeling genes being differentially expressed in relation to Hic-5 expression. The subcellular distribution of the MRTF-A transcription factor and expression of a subset of MRTF-A responsive genes was also impacted by Hic-5 expression. Additionally, cytokine array analysis of conditioned media from the Hic-5 and Hic-5 knockout cancer associated fibroblasts revealed that Hic-5 is important for the secretion of several key factors that are associated with matrix remodeling, angiogenesis and immune evasion. Together, these data provide further evidence of a central role for Hic-5 expression in cancer associated fibroblasts in regulating the composition and organization of the tumor stroma microenvironment to promote breast tumor progression.

Paxillin family proteins Hic-5 and LPXN promote lipid storage by regulating the ubiquitination degradation of CIDEC

Many metabolic diseases are caused by disorders of lipid homeostasis. CIDEC, a lipid droplet (LD)-associated protein, plays a critical role in controlling LD fusion and lipid storage. However, regulators of CIDEC remain largely unknown. Here, we established a homogeneous time-resolved fluorescence (HTRF)-based high-throughput screening method and identified LPXN as a positive regulatory candidate for CIDEC. LPXN and Hic-5, the members of the Paxillin family, are focal adhesion adaptor proteins that contribute to the recruitment of specific kinases and phosphatases, cofactors, and structural proteins, participating in the transduction of extracellular signals into intracellular responses. Our data showed that Hic-5 and LPXN significantly increased the protein level of CIDEC and enhanced CIDEC stability not through triacylglycerol synthesis and FAK signaling pathways. Hic-5 and LPXN reduced the ubiquitination of CIDEC and inhibited its proteasome degradation pathway. Furthermore, Hic-5 and LPXN enlarged LDs and promoted lipid storage in adipocytes. Therefore, we identified Hic-5 and LPXN as novel regulators of CIDEC. Our current findings also suggest intervention with Hic-5 and LPXN might ameliorate ectopic fat storage by enhancing the lipid storage capacity of white adipose tissues.

Paxillin participates in the sphingosylphosphorylcholine-induced abnormal contraction of vascular smooth muscle by regulating Rho-kinase activation

BACKGROUND

The Ca2+-independent contraction of vascular smooth muscle is a leading cause of cardiovascular and cerebrovascular spasms. In the previous study, we demonstrated the involvement of Src family protein tyrosine kinase Fyn and Rho-kinase in the sphingosylphosphorylcholine (SPC)-induced abnormal and Ca2+-independent contraction of vascular smooth muscle, but the specific mechanism has not been completely clarified.

METHODS

Paxillin knockdown human coronary artery smooth muscle cells (CASMCs) and smooth muscle-specific paxillin knockout mice were generated by using paxillin shRNA and the tamoxifen-inducible Cre-LoxP system, respectively. CASMCs contraction was observed by time-lapse recording. The vessel contractility was measured by using a myography assay. Fyn, Rho-kinase, and myosin light chain activation were assessed by immunoprecipitation and western blotting. The paxillin expression and actin stress fibers were visualized by histological analysis and immunofluorescent staining.

RESULTS

The SPC-induced abnormal contraction was inhibited in paxillin knockdown CASMCs and arteries of paxillin knockout mice, indicating that paxillin is involved in this abnormal contraction. Further study showed that paxillin knockdown inhibited the SPC-induced Rho-kinase activation without affecting Fyn activation. In addition, paxillin knockdown significantly inhibited the SPC-induced actin stress fiber formation and myosin light chain phosphorylation. These results suggest that paxillin, as an upstream molecule of Rho-kinase, is involved in the SPC-induced abnormal contraction of vascular smooth muscle.

CONCLUSIONS

The present study demonstrated that paxillin participates in the SPC-induced abnormal vascular smooth muscle contraction by regulating Rho-kinase activation. Video Abstract.

Extraciliary OFD1 Is Involved in Melanocyte Survival through Cell Adhesion to ECM via Paxillin

Primary cilia play a significant role in influencing cell fate, including apoptosis in multiple cell types. In the lesional epidermis of vitiligo patients, a reduced number of ciliated cells was observed. Our study also revealed a downregulation of oral-facial digital syndrome type 1 (OFD1) in the affected skin of vitiligo patients. However, it remains unknown whether primary cilia are involved in the control of melanocyte apoptosis. While both intraflagellar transport 88 (IFT88) and retinitis pigmentosa GTPase regulator-interacting protein-1 like (RPGRIP1L) are associated with ciliogenesis in melanocytes, only the knockdown of OFD1, but not IFT88 and RPGRIP1L, resulted in increased melanocyte apoptosis. OFD1 knockdown led to a decrease in the expression of proteins involved in cell-extracellular matrix (ECM) interactions, including paxillin. The OFD1 amino acid residues 601-1012 interacted with paxillin, while the amino acid residues 1-601 were associated with ciliogenesis, suggesting that the OFD1 domains responsible for paxillin binding are distinct from those involved in ciliogenesis. OFD1 knockdown, but not IFT88 knockdown, inhibited melanocyte adhesion to the ECM, a defect that was restored by paxillin overexpression. In summary, our findings indicate that the downregulation of OFD1 induces melanocyte apoptosis, independent of any impairment in ciliogenesis, by reducing melanocyte adhesion to the ECM via paxillin.

An ULK1/2-PXN mechanotransduction pathway suppresses breast cancer cell migration

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.

Paxillin interactome identified by SILAC and label-free approaches coupled to TurboID sheds light on the compositions of focal adhesions in mouse embryonic stem cells

Self-renewal and differentiation of mouse embryonic stem cells (mESCs) are greatly affected by the extracellular matrix (ECM) environment; the composition and stiffness of which are sensed by the cells via integrin-associated focal adhesions (FAs) which link the cells to the ECM. Although FAs have been studied extensively in differentiated cells, their composition and function in mESCs are not as well elucidated. To gain more detailed knowledge of the molecular compositions of FAs in mESCs, we adopted the proximity-dependent biotinylation (BioID) proteomics approach. Paxillin, a known FA protein (FAP), is fused to the promiscuous biotin ligase TurboID as bait. We employed both SILAC- and label-free (LF)-based quantitative proteomics to strengthen as well as complement individual approach. The mass spectrometry data derived from SILAC and LF identified 38 and 443 proteins, respectively, with 35 overlapping candidates. Fifteen of these shared proteins are known FAPs based on literature-curated adhesome and 7 others are among the reported "meta-adhesome", suggesting the components of FAs are largely conserved between mESCs and differentiated cells. Furthermore, the LF data set contained an additional 18 literature-curated FAPs. Notably, the overlapped proteomics data failed to detect LIM-domain proteins such as zyxin family proteins, which suggests that FAs in mESCs are less mature than differentiated cells. Using the LF approach, we are able to identify PDLIM7, a LIM-domain protein, as a FAP in mESCs. This study illustrates the effectiveness of TurboID in mESCs. Importantly, we found that application of both SILAC and LF methods in combination allowed us to analyze the TurboID proteomics data in an unbiased, stringent and yet comprehensive manner.

Phenotype screens of murine pancreatic cancer identify a Tgf-α-Ccl2-paxillin axis driving human-like neural invasion

Solid cancers like pancreatic ductal adenocarcinoma (PDAC), a type of pancreatic cancer, frequently exploit nerves for rapid dissemination. This neural invasion (NI) is an independent prognostic factor in PDAC, but insufficiently modeled in genetically engineered mouse models (GEMM) of PDAC. Here, we systematically screened for human-like NI in Europe's largest repository of GEMM of PDAC, comprising 295 different genotypes. This phenotype screen uncovered 2 GEMMs of PDAC with human-like NI, which are both characterized by pancreas-specific overexpression of transforming growth factor α (TGF-α) and conditional depletion of p53. Mechanistically, cancer-cell-derived TGF-α upregulated CCL2 secretion from sensory neurons, which induced hyperphosphorylation of the cytoskeletal protein paxillin via CCR4 on cancer cells. This activated the cancer migration machinery and filopodia formation toward neurons. Disrupting CCR4 or paxillin activity limited NI and dampened tumor size and tumor innervation. In human PDAC, phospho-paxillin and TGF-α-expression constituted strong prognostic factors. Therefore, we believe that the TGF-α-CCL2-CCR4-p-paxillin axis is a clinically actionable target for constraining NI and tumor progression in PDAC.

Paxillin regulates liver fibrosis via actin polymerization and ERK activation in hepatic stellate cells

Liver injury leads to fibrosis and cirrhosis. The primary mechanism underlying the fibrogenic response is the activation of hepatic stellate cells (HSCs), which are 'quiescent' in normal liver but become 'activated' after injury by transdifferentiating into extracellular matrix (ECM)-secreting myofibroblasts. Given that integrins are important in HSC activation and fibrogenesis, we hypothesized that paxillin, a key downstream effector in integrin signaling, might be critical in the fibrosis pathway. Using a cell-culture-based model of HSC activation and in vivo models of liver injury, we found that paxillin is upregulated in activated HSCs and fibrotic livers. Overexpression of paxillin (both in vitro and in vivo) led to increased ECM protein expression, and depletion of paxillin in a novel conditional mouse injury model reduced fibrosis. The mechanism by which paxillin mediated this effect appeared to be through the actin cytoskeleton, which signals to the ERK pathway and induces ECM protein production. These data highlight a novel role for paxillin in HSC biology and fibrosis.

Evaluation of Paxillin Expression in Epithelial Dysplasia, Oral Squamous Cell Carcinoma, Lichen Planus with and without Dysplasia, and Hyperkeratosis: A Retrospective Cross-Sectional Study

BACKGROUND

Paxillin is a cytoskeletal protein involved in the pathogenesis of several types of cancers. However, the roles of paxillin in epithelial dysplasia (ED), oral squamous cell carcinoma (OSCC), oral lichen planus with dysplasia (OLPD), hyperkeratosis (HK), and oral lichen planus (OLP) have remained unnoticed in the literature. This study aimed to evaluate its attainable functions in the pathogenesis and malignant transformation of potentially malignant oral epithelium and benign lesions.

METHODS

In this retrospective cross-sectional study, paxillin expression was investigated in 99 tissue samples, including 18 cases of OSCC, 21 ED, 23 OLP, 21 OLPD, and 16 cases of HK. The tissue sections also underwent immunohistochemical paxillin staining using 3,3-diaminobenzidine (DAB) chromogen. The intensity, location, and percentage of staining were examined across all groups. Data were analyzed using the Shapiro-Wilk test, ANOVA, Pearson chi-square, Kruskal-Wallis, and Dunn's post hoc test.

RESULTS

The cytoplasmic percentage and intensity staining of Paxillin expression were evident in the central/suprabasal and basal/peripheral layers of all the obtained samples. The final staining score was significantly higher in OSCC and dysplasia compared to HK and OLP (p = 0.004). It was found that paxillin expression is associated with the grade of dysplastic samples (p < 0.001).

CONCLUSION

The present study provides evidence that paxillin may be involved in the pathogenesis of OSCC and the development and progression of dysplastic tissue, since the paxillin expression was higher than that of HK and OLP.

Paxillin regulates Rab5-mediated vesicle motility through modulating microtubule acetylation

Rab GTPase-mediated vesicle trafficking of cell surface proteins, including integrins, through endocytic and recycling pathways is important in controlling cell-extracellular matrix interactions during cell migration. The focal adhesion adaptor protein, paxillin, plays a central role in regulating adhesion dynamics and was previously shown to promote anterograde vesicle trafficking through modulation of microtubule acetylation via its inhibition of the deacetylase HDAC6. The role of paxillin in retrograde trafficking is unknown. Herein, we identified a role for paxillin in the modulation of the Rab5 GTPase, which is necessary for regulating early endosome dynamics and focal adhesion turnover. Using MDA-MB-231 breast cancer cells and paxillin (-/-) fibroblasts, paxillin was shown to impact Rab5-associated vesicle size and distribution, as well as Rab5 GTPase activity, through its modulation of HDAC6. Using a combination of real-time imaging and particle tracking analysis, paxillin was shown to promote Rab5-associated vesicle motility through inhibition of HDAC6-mediated micro-tubule deacetylation, along with the localization of active integrin to focal adhesions.

α-Hemolysin promotes uropathogenic E. coli persistence in Bladder epithelial cells Via abrogating bacteria-harboring lysosome acidification

There is a growing consensus that a significant proportion of recurrent urinary tract infections are linked to the persistence of uropathogens within the urinary tract and their re-emergence upon the conclusion of antibiotic treatment. Studies in mice and human have revealed that uropathogenic Escherichia coli (UPEC) can persist in bladder epithelial cells (BECs) even after the apparent resolution of the infection. Here, we found that, following the entry of UPEC into RAB27b+ fusiform vesicles in BECs, some bacteria escaped into the cytoplasmic compartment via a mechanism involving hemolysin A (HlyA). However, these UPEC were immediately recaptured within LC3A/B+ autophagosomes that matured into LAMP1+ autolysosomes. Thereafter, HlyA+ UPEC-containing lysosomes failed to acidify, which is an essential step for bacterial elimination. This lack of acidification was related to the inability of bacteria-harboring compartments to recruit V-ATPase proton pumps, which was attributed to the defragmentation of cytosolic microtubules by HlyA. The persistence of UPEC within LAMP1+ compartments in BECs appears to be directly linked to HlyA. Thus, through intravesicular instillation of microtubule stabilizer, this host defense response can be co-opted to reduce intracellular bacterial burden following UTIs in the bladder potentially preventing recurrence.

Acidic Growth Conditions Promote Epithelial-to-Mesenchymal Transition to Select More Aggressive PDAC Cell Phenotypes In Vitro

Pancreatic Ductal Adenocarcinoma (PDAC) is characterized by an acidic microenvironment, which contributes to therapeutic failure. So far there is a lack of knowledge with respect to the role of the acidic microenvironment in the invasive process. This work aimed to study the phenotypic and genetic response of PDAC cells to acidic stress along the different stages of selection. To this end, we subjected the cells to short- and long-term acidic pressure and recovery to pH_e 7.4. This treatment aimed at mimicking PDAC edges and consequent cancer cell escape from the tumor. The impact of acidosis was assessed for cell morphology, proliferation, adhesion, migration, invasion, and epithelial-mesenchymal transition (EMT) via functional in vitro assays and RNA sequencing. Our results indicate that short acidic treatment limits growth, adhesion, invasion, and viability of PDAC cells. As the acid treatment progresses, it selects cancer cells with enhanced migration and invasion abilities induced by EMT, potentiating their metastatic potential when re-exposed to pH_e 7.4. The RNA-seq analysis of PANC-1 cells exposed to short-term acidosis and pH_e-selected recovered to pH_e 7.4 revealed distinct transcriptome rewiring. We describe an enrichment of genes relevant to proliferation, migration, EMT, and invasion in acid-selected cells. Our work clearly demonstrates that upon acidosis stress, PDAC cells acquire more invasive cell phenotypes by promoting EMT and thus paving the way for more aggressive cell phenotypes.

Crisscross multilayering of cell sheets

Hydrostatic skeletons such as the Hydra's consist of two stacked layers of muscle cells perpendicularly oriented. In vivo, these bilayers first assemble, and then the muscle fibers of both layers develop and organize with this crisscross orientation. In the present work, we identify an alternative mechanism of crisscross bilayering of myoblasts in vitro, which results from the prior local organization of these active cells in the initial monolayer. The myoblast sheet can be described as a contractile active nematic in which, as expected, most of the +1/2 topological defects associated with this nematic order self-propel. However, as a result of the production of extracellular matrix (ECM) by the cells, a subpopulation of these comet-like defects does not show any self-propulsion. Perpendicular bilayering occurs at these stationary defects. Cells located at the head of these defects converge toward their core where they accumulate until they start migrating on top of the tail of the first layer, while the tail cells migrate in the opposite direction under the head. Since the cells keep their initial orientations, the two stacked layers end up perpendicularly oriented. This concerted process leading to a crisscross bilayering is mediated by the secretion of ECM.

Surface physical cues mediate the uptake of foreign particles by cancer cells

Cancer phenotypes are often associated with changes in the mechanical states of cells and their microenvironments. Numerous studies have established correlations between cancer cell malignancy and cell deformability at the single-cell level. The mechanical deformation of cells is required for the internalization of large colloidal particles. Compared to normal epithelial cells, cancer cells show higher capacities to distort their shapes during the engulfment of external particles, thus performing phagocytic-like processes more efficiently. This link between cell deformability and particle uptake suggests that the cell's adherence state may affect this particle uptake, as cells become stiffer when plated on a more rigid substrate and vice versa. Based on this, we hypothesized that cancer cells of the same origin, which are subjected to external mechanical cues through attachment to surfaces with varying rigidities, may express different capacities to uptake foreign particles. The effects of substrate rigidity on cancer cell uptake of inert particles (0.8 and 2.4 μm) were examined using surfaces with physiologically relevant rigidities (from 0.5 to 64 kPa). Our data demonstrate a wave-like ("meandering") dependence of cell uptake on the rigidity of the culture substrate explained by a superposition of opposing physical and biological effects. The uptake patterns were inversely correlated with the expression of phosphorylated paxillin, indicating that the initial passive particle absorbance is the primary limiting step toward complete uptake. Overall, our findings may provide a foundation for mechanical rationalization of particle uptake design.

Elucidation of the signalling pathways for enhanced exosome release from Mycobacterium-infected macrophages and subsequent induction of differentiation

Exosomes are extracellular vesicles released by all cell types; perform several important functions such as cell-to-cell communication, growth, differentiation and so on. Exosomes elicit several signalling mechanisms as they carry information in the form of DNA, RNA or protein docked on them. We show that exosomes released from Mycobacterium tuberculosis (Mtb)-infected macrophages not only induce differentiation of naïve monocytes but also generate functionally active macrophages via MAPK-dependent signalling mechanism through MK-2 and NF-κβ activation which is completely different from the differentiation induced by exosomes from uninfected macrophages. Further, we elucidate unequivocally the signalling mechanism behind the enhanced release of exosome generation from infected macrophages driven by AKT phosphorylation involving Rab7a and Rab11a. Genes of both ESCRT-dependent and -independent pathways are found to be involved in enhanced exosomes release and are modulated by AKT. However, interestingly, the genes of the ESCRT-independent pathway are dependent on NF-κβ activation while the genes of the dependent pathway are not, suggesting two parallel signalling cascades operating in tandem.

Evaluation of competency and job satisfaction by positive human psychology among physical education teachers at the university level: A systematic review

The study aimed to determine how a teacher's competency at the university level related to professional commitment and job satisfaction. This systematic review intends to determine physical education teachers' competency and job satisfaction. One of the main objectives of physical education programs is to increase various activities of the student, especially physical activities and participation in it. Students who participate in physical activities feel a variety of emotions, and these may enhance their mental and physical well-being. The study concerns the teachers' satisfaction in effectively influencing and teaching the students. Job satisfaction refers to teachers' feelings and positive attitudes toward their work. The five components of job satisfaction are pay, promotion, supervision, co-workers, and work itself. Job satisfaction is broken down into these five components. Work as a teacher is one of the most important components of a teacher's or teacher's success at work and one of the key criteria for the school's achievement. Electronic libraries were explored, including Google Scholar, PubMed, Embase, Bing Academic, and Cochrane. Appropriate keywords were used for searching the literature. By applying certain inclusion and exclusion criteria, the final studies were selected for evaluation. The study's findings showed that physical education instructors had high levels of teaching competence and moderate levels of job satisfaction. The findings demonstrated that job satisfaction and competency rise when degree levels rise, and relatedness, skill, and autonomy self-motivation ensue. Students' motivation for physical education was greatly influenced by the teachers' support, motivation, and mastery climate. The self-determination theory positively enhances physical education from the teacher's perspective on PE, increasing instruction effectiveness.

Single-molecule characterization of subtype-specific β1 integrin mechanics

Although integrins are known to be mechanosensitive and to possess many subtypes that have distinct physiological roles, single molecule studies of force exertion have thus far been limited to RGD-binding integrins. Here, we show that integrin α4β1 and RGD-binding integrins (αVβ1 and α5β1) require markedly different tension thresholds to support cell spreading. Furthermore, actin assembled downstream of α4β1 forms cross-linked networks in circularly spread cells, is in rapid retrograde flow, and exerts low forces from actin polymerization. In contrast, actin assembled downstream of αVβ1 forms stress fibers linking focal adhesions in elongated cells, is in slow retrograde flow, and matures to exert high forces (>54-pN) via myosin II. Conformational activation of both integrins occurs below 12-pN, suggesting that post-activation subtype-specific cytoskeletal remodeling imposes the higher threshold for spreading on RGD substrates. Multiple layers of single integrin mechanics for activation, mechanotransduction and cytoskeleton remodeling revealed here may underlie subtype-dependence of diverse processes such as somite formation and durotaxis.

Effect of Poly(Oxanorbonene)- and Poly(Methacrylate)-Based Polyzwitterionic Surface Coatings on Cell Adhesion and Gene Expression of Human Keratinocytes

Polyzwitterions are generally known for their anti-adhesive properties, including resistance to protein and cell adhesion, and overall high bio-inertness. Yet there are a few polyzwitterions to which mammalian cells do adhere. To understand the structural features of this behavior, a panel of polyzwitterions with different functional groups and overall degrees of hydrophobicity is analyzed here, and their physical and biological properties are correlated to these structural differences. Cell adhesion is focused on, which is the basic requirement for cell viability, proliferation, and growth. With the here presented polyzwitterion panel, three different types of cell-surface interactions are observed: adhesion, slight attachment, and cell repellency. Using immunofluorescence methods, it is found that human keratinocytes (HaCaT) form focal adhesions on the cell-adhesive polyzwitterions, but not on the sample that has only slight cell attachment. Gene expression analysis indicates that HaCaT cells cultivated in the presence of a non-adhesive polyzwitterion have up-regulated inflammatory and apoptosis-related cell signaling pathways, while the gene expression of HaCaT cells grown on a cell-adhesive polyzwitterion does not differ from the gene expression of the growth control, and thus can be defined as fully cell-compatible.

The explorations of dynamic interactions of paxillin at the focal adhesions

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.

Nestin Modulates Airway Smooth Muscle Cell Migration by Affecting Spatial Rearrangement of Vimentin Network and Focal Adhesion Assembly

Airway smooth muscle cell migration plays a role in the progression of airway remodeling, a hallmark of allergic asthma. However, the mechanisms that regulate cell migration are not yet entirely understood. Nestin is a class VI intermediate filament protein that is involved in the proliferation/regeneration of neurons, cancer cells, and skeletal muscle. Its role in cell migration is not fully understood. Here, nestin knockdown (KD) inhibited the migration of human airway smooth muscle cells. Using confocal microscopy and the Imaris software, we found that nestin KD attenuated focal adhesion sizes during cell spreading. Moreover, polo-like kinase 1 (Plk1) and vimentin phosphorylation at Ser-56 have been previously shown to affect focal adhesion assembly. Here, nestin KD reduced Plk1 phosphorylation at Thr-210 (an indication of Plk1 activation), vimentin phosphorylation at Ser-56, the contacts of vimentin filaments to paxillin, and the morphology of focal adhesions. Moreover, the expression of vimentin phosphorylation-mimic mutant S56D (aspartic acid substitution at Ser-56) rescued the migration, vimentin reorganization, and focal adhesion size of nestin KD cells. Together, our results suggest that nestin promotes smooth muscle cell migration. Mechanistically, nestin regulates Plk1 phosphorylation, which mediates vimenitn phosphorylation, the connection of vimentin filaments with paxillin, and focal adhesion assembly.

Expression of the phagocytic receptors αMβ2 and αXβ2 is controlled by RIAM, VASP and Vinculin in neutrophil-differentiated HL-60 cells

Activation of the integrin phagocytic receptors CR3 (α_Mβ₂, CD11b/CD18) and CR4 (α_Xβ₂, CD11c/CD18) requires Rap1 activation and RIAM function. RIAM controls integrin activation by recruiting Talin to β₂ subunits, enabling the Talin-Vinculin interaction, which in term bridges integrins to the actin-cytoskeleton. RIAM also recruits VASP to phagocytic cups and facilitates VASP phosphorylation and function promoting particle internalization. Using a CRISPR-Cas9 knockout approach, we have analyzed the requirement for RIAM, VASP and Vinculin expression in neutrophilic-HL-60 cells. All knockout cells displayed abolished phagocytosis that was accompanied by a significant and specific reduction in ITGAM (α_M), ITGAX (α_X) and ITGB2 (β₂) mRNA, as revealed by RT-qPCR. RIAM, VASP and Vinculin KOs presented reduced cellular F-actin content that correlated with αM expression, as treatment with the actin filament polymerizing and stabilizing drug jasplakinolide, partially restored α_M expression. In general, the expression of α_X was less responsive to jasplakinolide treatment than α_M, indicating that regulatory mechanisms independent of F-actin content may be involved. The Serum Response Factor (SRF) was investigated as the potential transcription factor controlling α_Mβ₂ expression, since its coactivator MRTF-A requires actin polymerization to induce transcription. Immunofluorescent MRTF-A localization in parental cells was primarily nuclear, while in knockouts it exhibited a diffuse cytoplasmic pattern. Localization of FHL-2 (SRF corepressor) was mainly sub-membranous in parental HL-60 cells, but in knockouts the localization was disperse in the cytoplasm and the nucleus, suggesting RIAM, VASP and Vinculin are required to maintain FHL-2 close to cytoplasmic membranes, reducing its nuclear localization and inhibiting its corepressor activity. Finally, reexpression of VASP in the VASP knockout resulted in a complete reversion of the phenotype, as knock-ins restored α_M expression. Taken together, our results suggest that RIAM, VASP and Vinculin, are necessary for the correct expression of α_Mβ₂ and α_Xβ₂ during neutrophilic differentiation in the human promyelocytic HL-60 cell line, and strongly point to an involvement of these proteins in the acquisition of a phagocytic phenotype.

Integrin β1 in Pancreatic Cancer: Expressions, Functions, and Clinical Implications

Simple Summary

Pancreatic cancer (PC) is a highly aggressive malignant tumor with an extremely poor prognosis. Early diagnosis and treatment are key to improving the survival rate of PC patients. Emerging studies show that integrins might contribute to the pathogenesis of PC. This review presents the various signaling pathways that are mediated by integrins in PC and emphasizes the multiple functions of integrin β1 in malignant behaviors of PC. It also discusses the clinical significance of integrin β1 as well as integrin β1-based therapy in PC patients.

Abstract

Pancreatic cancer (PC) is characterized by rapid progression and a high mortality rate. The current treatment is still based on surgical treatment, supplemented by radiotherapy and chemotherapy, and new methods of combining immune and molecular biological treatments are being explored. Despite this, the survival rate of PC patients is still very disappointing. Therefore, clarifying the molecular mechanism of PC pathogenesis and developing precisely targeted drugs are key to improving PC prognosis. As the most common β subunit of the integrin family, integrin β1 has been proved to be closely related to the vascular invasion, distant metastasis, and survival of PC patients, and treatment targeting integrin β1 in PC has gained initial success in animal models. In this review, we summarize the various signaling pathways by which integrins are involved in PC, focusing on the roles of integrin β1 in the malignant behaviors of PC. Additionally, recent studies regarding the feasibility of integrin β1 as a diagnostic and prognostic biomarker in PC are also discussed. Finally, we present the progress of several integrin β1-based clinical trials to highlight the potential of integrin β1 as a target for personalized therapy in PC.

Cytostatic Effects of Polyethyleneimine Surfaces on the Mesenchymal Stromal Cell Cycle

Polyelectrolytes assembled layer-by-layer (PEMs) are commonly used as functional coatings to build-up biological interfaces, particularly suitable as compatible layers for the interaction with a biological medium, providing suitable conditions to promote or prevent cell seeding while maintaining the phenotype. The proper assessment of the biocompatibility of PEMs and the elucidation of the related mechanisms are therefore of paramount importance. In this study, we report in detail the effect of two different PEM endings, polystyrene sulfonate (PSS) and polyethylenimine (PEI), respectively, on the cell adhesion, growth, and viability of human bone mesenchymal stromal cells (MSCs). The results have shown that PSS-ended substrates appear to be the most suitable to drive the cell adhesion and phenotype maintenance of MSCs, showing good biocompatibility. On the contrary, while the cells seem to adhere more quickly and strongly on the PEI-ended surfaces, the interaction with PEI significantly affects the growth and viability, reducing the cell spreading capability, by sequestering the adhesion molecules already in the very early steps of cell–substrate contact. These results point to the promotion of a cytostatic effect of PEI, rather than the often-claimed cytotoxicity.

Paxillin: A Hub for Mechano-Transduction from the β3 Integrin-Talin-Kindlin Axis

Focal adhesions are specialized integrin-dependent adhesion complexes, which ensure cell anchoring to the extracellular matrix. Focal adhesions also function as mechano-signaling platforms by perceiving and integrating diverse physical and (bio)chemical cues of their microenvironment, and by transducing them into intracellular signaling for the control of cell behavior. The fundamental biological mechanism of creating intracellular signaling in response to changes in tensional forces appears to be tightly linked to paxillin recruitment and binding to focal adhesions. Interestingly, the tension-dependent nature of the paxillin binding to adhesions, combined with its scaffolding function, suggests a major role of this protein in integrating multiple signals from the microenvironment, and accordingly activating diverse molecular responses. This minireview offers an overview of the molecular bases of the mechano-sensitivity and mechano-signaling capacity of core focal adhesion proteins, and highlights the role of paxillin as a key component of the mechano-transducing machinery based on the interaction of cells to substrates activating the β3 integrin-talin1-kindlin.

Phosphorylated paxillin and phosphorylated FAK constitute subregions within focal adhesions

Integrin-mediated adhesions are convergence points of multiple signaling pathways. Their inner structure and their diverse functions can be studied with super-resolution microscopy. Here, we examined the spatial organization within focal adhesion by analyzing several adhesion proteins with structured illumination microscopy (SIM). We found that phosphorylated paxillin (pPax) and phosphorylated focal adhesion kinase (pFAK) form spot-like, spatially defined clusters within adhesions in several cell lines and confirmed these findings with additional super-resolution techniques. These clusters showed a more regular separation from each other compared to more randomly distributed labels of general FAK or paxillin. Mutational analysis indicated that the active (open) FAK conformation is a prerequisite for the pattern formation of pFAK. Live-cell super-resolution imaging revealed that organization in clusters is preserved over time for FAK constructs; however, distance between clusters is dynamic for FAK, while paxillin is more stable. Combined, these data introduce spatial clusters of pPax and pFAK as substructures in adhesions and highlight the relevance of paxillin-FAK binding for establishing a regular substructure in focal adhesions.

Sulforaphane suppresses metastasis of triple-negative breast cancer cells by targeting the RAF/MEK/ERK pathway

Breast cancer metastasis is the main cause of cancer death in women, so far, no effective treatment has inhibited breast cancer metastasis. Sulforaphane (SFN), a natural compound derived from broccoli, has shown potential health benefits in many cancers. However, research on breast cancer metastasis is still insufficient. Here, we showed that SFN, including its two isomers of R-SFN and S-SFN, significantly inhibited TGF-β1-induced migration and invasion in breast cancer cells. Proteomic and phosphoproteomic analysis showed that SFN affected the formation of the cytoskeleton. Subsequent experiments confirmed that SFN significantly inhibited TGF-β1-induced actin stress fiber formation and the expression of actin stress fiber formation-associated proteins, including paxillin, IQGAP1, FAK, PAK2, and ROCK. Additionally, SFN is directly bound to RAF family proteins (including ARAF, BRAF, and CRAF) and inhibited MEK and ERK phosphorylation. These in vitro results indicate that SFN targets the RAF/MEK/ERK signaling pathway to inhibit the formation of actin stress fibers, thereby inhibiting breast cancer cell metastasis.

The core autophagy protein ATG9A controls dynamics of cell protrusions and directed migration

Chemotactic migration is a fundamental cellular behavior relying on the coordinated flux of lipids and cargo proteins toward the leading edge. We found here that the core autophagy protein ATG9A plays a critical role in the chemotactic migration of several human cell lines, including highly invasive glioma cells. Depletion of ATG9A protein altered the formation of large and persistent filamentous actin (F-actin)-rich lamellipodia that normally drive directional migration. Using live-cell TIRF microscopy, we demonstrated that ATG9A-positive vesicles are targeted toward the migration front of polarized cells, where their exocytosis correlates with protrusive activity. Finally, we found that ATG9A was critical for efficient delivery of β1 integrin to the leading edge and normal adhesion dynamics. Collectively, our data uncover a new function for ATG9A protein and indicate that ATG9A-positive vesicles are mobilized during chemotactic stimulation to facilitate expansion of the lamellipodium and its anchorage to the extracellular matrix.

Paxillin Promotes Breast Tumor Collective Cell Invasion through Maintenance of Adherens Junction Integrity

Distant organ metastasis is linked to poor prognosis during cancer progression. The expression level of the focal adhesion adapter protein paxillin varies among different human cancers, but its role in tumor progression is unclear. Herein, we utilize a newly generated PyMT mammary tumor mouse model with conditional paxillin ablation in breast tumor epithelial cells, combined with in vitro 3D tumor organoids invasion analysis and 2D calcium switch assays, to assess the roles for paxillin in breast tumor cell invasion. Paxillin had little effect on primary tumor initiation and growth but is critical for the formation of distant lung metastasis. In paxillin-depleted 3D tumor organoids, collective cell invasion was substantially perturbed. Two-dimensional cell culture revealed paxillin-dependent stabilization of adherens junctions (AJ). Mechanistically, paxillin is required for AJ assembly through facilitating E-cadherin endocytosis and recycling and HDAC6-mediated microtubule acetylation. Furthermore, Rho GTPase activity analysis and rescue experiments with a RhoA activator or Rac1 inhibitor suggest paxillin is potentially regulating the E-cadherin-dependent junction integrity and contractility through control of the balance of RhoA and Rac1 activities. Together, these data highlight new roles for paxillin in the regulation of cell-cell adhesion and collective tumor cell migration to promote the formation of distance organ metastases. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text].

Genetic Differences between Physical Injury Patients With and Without Post-traumatic Syndrome: Focus on Secondary Findings and Potential Variants Revealed by Whole Exome Sequencing

Objective

Sudden traumatic physical injuries often cause psychological distress, which may be associated with chronic disability. Although considerable effort has been expended to identify genetic predictors of post-traumatic stress disorder (PTSD) after traumatic events, genetic predictors of psychological distress in response to severe physical injuries have been yet to be elucidated using whole exome sequencing (WES). Here, the genetic architecture of post-traumatic syndrome (PTS), which encompasses a broad range of psychiatric disorders after traumatic events including depression, anxiety disorder, acute stress disorder, and PTSD, was explored using WES in severely physically injured patients, focusing on secondary findings and potential PTS-related variants.

Methods

In total, 141 severely physically injured patients were consecutively recruited, and PTS was evaluated within 1 month of the injury. Secondary findings were analyzed according to PTS status. To identify PTS-related variants, genome-wide association analyses and the optimal sequencing kernel association test were performed.

Results

Of the 141 patients, 88 (62%) experienced PTS. There were 108 disease-causing variants in severely physically injured patients. As secondary findings, the stress- and inflammation-related signaling pathways were enriched in the PTS patients, while the glucose metabolism pathway was enriched in those without PTS. However, no significant PTS-related variants were identified.

Conclusion

Our findings suggest that genetic alterations in stress and inflammatory pathways might increase the likelihood of PTS immediately after severe physical injury. Future studies with larger samples and longitudinal designs are needed.

A Layered View on Focal Adhesions

Simple Summary

The cytoskeleton is a network of protein fibres within cells that provide structure and support intracellular transport. Focal adhesions are protein complexes associated with the outer cell membrane that are found at the ends of specialised actin fibres of this cytoskeleton. They mediate cell adhesion by connecting the cytoskeleton to the extracellular matrix, a protein and sugar network that surrounds cells in tissues. Focal adhesions also translate forces on actin fibres into forces contributing to cell migration. Cell adhesion and migration are crucial to diverse biological processes such as embryonic development, proper functioning of the immune system or the metastasis of cancer cells. Advances in fluorescence microscopy and data analysis methods provided a more detailed understanding of the dynamic ways in which proteins bind and dissociate from focal adhesions and how they are organised within these protein complexes. In this review, we provide an overview of the advances in the current scientific understanding of focal adhesions and summarize relevant imaging techniques. One of the key insights is that focal adhesion proteins are organised into three layers parallel to the cell membrane. We discuss the relevance of this layered nature for the functioning of focal adhesion.

Abstract

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.

Protein tyrosine phosphatase 1B targets focal adhesion kinase and paxillin in cell-matrix adhesions

Protein tyrosine phosphatase 1B (PTP1B, also known as PTPN1) is an established regulator of cell-matrix adhesion and motility. However, the nature of substrate targets at adhesion sites remains to be validated. Here, we used bimolecular fluorescence complementation assays, in combination with a substrate trapping mutant of PTP1B, to directly examine whether relevant phosphotyrosines on paxillin and focal adhesion kinase (FAK, also known as PTK2) are substrates of the phosphatase in the context of cell-matrix adhesion sites. We found that the formation of catalytic complexes at cell-matrix adhesions requires intact tyrosine residues Y31 and Y118 on paxillin, and the localization of FAK at adhesion sites. Additionally, we found that PTP1B specifically targets Y925 on the focal adhesion targeting (FAT) domain of FAK at adhesion sites. Electrostatic analysis indicated that dephosphorylation of this residue promotes the closed conformation of the FAT 4-helix bundle and its interaction with paxillin at adhesion sites.

Hypothalamic and ovarian transcriptome profiling reveals potential candidate genes in low and high egg production of white Muscovy ducks (Cairina moschata)

In China, the low egg production rate is a major challenge to Muscovy duck farmers. Hypothalamus and ovary play essential role in egg production of birds. However, there are little or no reports from these tissues to identify potential candidate genes responsible for egg production in White Muscovy ducks. A total of 1,537 laying ducks were raised; the egg production traits which include age at first egg (days), number of eggs at 300 d, and number of eggs at 59 wk were recorded. Moreover, 4 lowest (LP) and 4 highest producing (HP) were selected at 59 wk of age, respectively. To understand the mechanism of egg laying regulation, we sequenced the hypothalamus and ovary transcriptome profiles in LP and HP using RNA-Seq. The results showed that the number of eggs at 300 d and number of eggs at 59 wk in the HP were significantly more (P < 0.001) than the LP ducks. In total, 106.98G clean bases were generated from 16 libraries with an average of 6.68G clean bases for each library. Further analysis showed 569 and 2,259 differentially expressed genes (DEGs) were identified in the hypothalamus and ovary between LP and HP, respectively. The KEGG pathway enrichment analysis revealed 114 and 139 pathways in the hypothalamus and ovary, respectively which includes Calcium signaling pathway, ECM-receptor interaction, Focal adhesion, MAPK signaling pathway, Apoptosis and Apelin signaling pathways that are involved in egg production. Based on the GO terms and KEGG pathways results, 10 potential candidate genes (P2RX1, LPAR2, ADORA1, FN1, AKT3, ADCY5, ADCY8, MAP3K8, PXN, and PTTG1) were identified to be responsible for egg production. Further, protein-protein interaction was analyzed to show the relationship between these candidate genes. Therefore, this study provides useful information on transcriptome of hypothalamus and ovary of LP and HP Muscovy ducks.

Campylobacter jejuni Triggers Signaling through Host Cell Focal Adhesions To Inhibit Cell Motility

Campylobacter jejuni is a major foodborne pathogen that exploits the focal adhesions of intestinal cells to promote invasion and cause severe gastritis. Focal adhesions are multiprotein complexes involved in bidirectional signaling between the actin cytoskeleton and the extracellular matrix. We investigated the dynamics of focal adhesion structure and function in C. jejuni-infected cells using a comprehensive set of approaches, including confocal microscopy of live and fixed cells, immunoblotting, and superresolution interferometric photoactivated localization microscopy (iPALM). We found that C. jejuni infection of epithelial cells results in increased focal adhesion size and altered topology. These changes resulted in a persistent modulatory effect on the host cell focal adhesion, evidenced by an increase in cell adhesion strength, a decrease in individual cell motility, and a reduction in collective cell migration. We discovered that C. jejuni infection causes an increase in phosphorylation of paxillin and an alteration of paxillin turnover at the focal adhesion, which together represent a potential mechanistic basis for altered cell motility. Finally, we observed that infection of epithelial cells with the C. jejuni wild-type strain in the presence of a protein synthesis inhibitor, a C. jejuni CadF and FlpA fibronectin-binding protein mutant, or a C. jejuni flagellar export mutant blunts paxillin phosphorylation and partially reestablishes individual host cell motility and collective cell migration. These findings provide a potential mechanism for the restricted intestinal repair observed in C. jejuni-infected animals and raise the possibility that bacteria targeting extracellular matrix components can alter cell behavior after binding and internalization by manipulating focal adhesions.

SphK1-driven autophagy potentiates focal adhesion paxillin-mediated metastasis in colorectal cancer

Invasion and metastasis are the main causes of colorectal cancer (CRC)‐related death. Accumulating evidence suggested that sphingosine kinase 1 (SphK1) promoted the metastasis of CRC and autophagy played an important role in SphK1 promoting the metastasis of malignancy. However, the mechanism by which SphK1‐driven autophagy promotes invasion and metastasis in CRC remains to be clarified. In the present study, immunohistochemical detection showed the expression of SphK1 and paxillin was higher in human CRC tissues than those of normal colorectal mucosal tissues, they were both associated with TNM staging, lymphatic, and distance metastasis. In addition, study of in situ tumor transplantation model in nude mice showed that the suppression of SphK1 inhibited the growth of colonic orthotopic implantation tumors and the expression of paxillin, p‐paxillin, LC3 in the tumor. So, SphK1 may promote CRC metastasis via inducing the expression of paxillin expression and its phosphorylation, in vivo. Furthermore, results of CCK8 assay, transwell and wound healing assays showed that SphK1 promoted the viability, invasion, and metastasis of CRC cells. Transmission electron microscopy detection showed that SphK1 is the key factor in autophagy induction in CRC cells. Moreover, western blot examination indicated that the expression of LC3Ⅱ/Ⅰ, paxillin, p‐paxillin, MMP‐2, and vimentin was enhanced in SphK1‐overexpressed CRC cells and suppressed in SphK1 knockdown CRC cells, meanwhile, the expression of E‐cadherin was suppressed in SphK1‐overexpressed CRC cells and enhanced in SphK1 knockdown CRC cells. Suppression of autophagy by 3MA reversed the expression of paxillin and its phosphorylation in SphK1‐overexpressed CRC cells, indicated that SphK1‐driven autophagy induced the expression of paxillin and its phosphorylation in CRC cells. Together, these findings reveal that SphK1‐driven autophagy may promote the invasion and metastasis of CRC via promoting the expression of focal adhesion paxillin and its phosphorylation.

Chronic Wound Healing by Amniotic Membrane: TGF-β and EGF Signaling Modulation in Re-epithelialization

The application of amniotic membrane (AM) on chronic wounds has proven very effective at resetting wound healing, particularly in re-epithelialization. Historically, several aspects of AM effect on wound healing have been evaluated using cell models. In keratinocytes, the presence of AM induces the activation of mitogen-activated protein (MAP) kinase and c-Jun N-terminal kinase (JNK) pathways, together with the high expression of c-Jun, an important transcription factor for the progression of the re-epithelialization tongue. In general, the levels of transforming growth factor (TGF)-β present in a wound are critical for the process of wound healing; they are elevated during the inflammation phase and remain high in some chronic wounds. Interestingly, the presence of AM, through epidermal growth factor (EGF) signaling, produces a fine-tuning of the TGF-β signaling pathway that re-conducts the stalled process of wound healing. However, the complete suppression of TGF-β signaling has proven negative for the AM stimulation of migration, suggesting that a minimal amount of TGF-β signaling is required for proper wound healing. Regarding migration machinery, AM contributes to the dynamics of focal adhesions, producing a high turnover and thus speeding up remodeling. This is clear because proteins, such as Paxillin, are activated upon treatment with AM. On top of this, AM also produces changes in the expression of Paxillin. Although we have made great progress in understanding the effects of AM on chronic wound healing, a long way is still ahead of us to fully comprehend its effects.

Integrin-mediated interactions with a laminin-presenting substrate modulate biosynthesis and phenotypic expression for cells of the human nucleus pulposus

With aging and pathology, cells of the nucleus pulposus (NP) de-differentiate towards a fibroblast-like phenotype, a change that contributes to degeneration of the intervertebral disc (IVD). Laminin isoforms are a component of the NP extracellular matrix during development but largely disappear in the adult NP tissue. Exposing human adult NP cells to hydrogels made from PEGylated-laminin-111 (PEGLM) has been shown to regulate NP cell behaviors and promote cells to assume a biosynthetically active state with gene/protein expression and morphology consistent with those observed in juvenile NP cells. However, the mechanism regulating this effect has remained unknown. In the present study, the integrin subunits that promote adult degenerative NP cell interactions with laminin-111 are identified by performing integrin blocking studies along with assays of intracellular signaling and cell phenotype. The findings indicate that integrin α3 is a primary regulator of cell attachment to laminin and is associated with phosphorylation of signaling molecules downstream of integrin engagement (ERK 1/2 and GSK3β). Sustained effects of blocking integrin α3 were also demonstrated including decreased expression of phenotypic markers, reduced biosynthesis, and altered cytoskeletal organization. Furthermore, blocking both integrin α3 and additional integrin subunits elicited changes in cell clustering, but did not alter the phenotype of single cells. These findings reveal that integrin- mediated interactions through integrin α3 are critical in the process by which NP cells sense and alter phenotype in response to culture upon laminin and further suggest that targeting integrin α3 has potential for reversing or slowing degenerative changes to the NP cell.

LIM domain proteins in cell mechanobiology

The actin cytoskeleton is important for maintaining mechanical homeostasis in adherent cells, largely through its regulation of adhesion and cortical tension. The LIM (Lin-11, Isl1, MEC-3) domain-containing proteins are involved in a myriad of cellular mechanosensitive pathways. Recent work has discovered that LIM domains bind to mechanically stressed actin filaments, suggesting a novel and widely conserved mechanism of mechanosensing. This review summarizes the current state of knowledge of LIM protein mechanosensitivity.

MAGI1 localizes to mature focal adhesion and modulates endothelial cell adhesion, migration and angiogenesis

MAGI1 is an intracellular adaptor protein that stabilizes cell junctions and regulates epithelial and endothelial integrity. Here, we report that that in endothelial cells MAGI1 colocalizes with paxillin, β3-integrin, talin 1, tensin 3 and α-4-actinin at mature focal adhesions and actin stress fibers, and regulates their dynamics. Downregulation of MAGI1 reduces focal adhesion formation and maturation, cell spreading, actin stress fiber formation and RhoA/Rac1 activation. MAGI1 silencing increases phosphorylation of paxillin at Y118, an indicator of focal adhesion turnover. MAGI1 promotes integrin-dependent endothelial cells adhesion to ECM, reduces invasion and tubulogenesisin vitro and suppresses angiogenesis  in vivo. Our results identify MAGI1 as anovel component of focal adhesions, and regulator of focal adhesion dynamics, cell adhesion, invasion and angiogenesis.

Pre-complexation of talin and vinculin without tension is required for efficient nascent adhesion maturation

Talin and vinculin are mechanosensitive proteins that are recruited early to integrin-based nascent adhesions (NAs). In two epithelial cell systems with well-delineated NA formation, we find these molecules concurrently recruited to the subclass of NAs maturing to focal adhesions. After the initial recruitment under minimal load, vinculin accumulates in maturing NAs at a ~ fivefold higher rate than in non-maturing NAs, and is accompanied by a faster traction force increase. We identify the R8 domain in talin, which exposes a vinculin-binding-site (VBS) in the absence of load, as required for NA maturation. Disruption of R8 domain function reduces load-free vinculin binding to talin, and reduces the rate of additional vinculin recruitment. Taken together, these data show that the concurrent recruitment of talin and vinculin prior to mechanical engagement with integrins is essential for the traction-mediated unfolding of talin, exposure of additional VBSs, further recruitment of vinculin, and ultimately, NA maturation.

Structural and functional analysis of LIM domain-dependent recruitment of paxillin to αvβ3 integrin-positive focal adhesions

The LIM domain-dependent localization of the adapter protein paxillin to β3 integrin-positive focal adhesions (FAs) is not mechanistically understood. Here, by combining molecular biology, photoactivation and FA-isolation experiments, we demonstrate specific contributions of each LIM domain of paxillin and reveal multiple paxillin interactions in adhesion-complexes. Mutation of β3 integrin at a putative paxillin binding site (β3^VE/YA) leads to rapidly inward-sliding FAs, correlating with actin retrograde flow and enhanced paxillin dissociation kinetics. Induced mechanical coupling of paxillin to β3^VE/YA integrin arrests the FA-sliding, thereby disclosing an essential structural function of paxillin for the maturation of β3 integrin/talin clusters. Moreover, bimolecular fluorescence complementation unveils the spatial orientation of the paxillin LIM-array, juxtaposing the positive LIM4 to the plasma membrane and the β3 integrin-tail, while in vitro binding assays point to LIM1 and/or LIM2 interaction with talin-head domain. These data provide structural insights into the molecular organization of β3 integrin-FAs.

HDAC6 regulates microtubule stability and clustering of AChRs at neuromuscular junctions

Microtubules (MTs) are known to be post-translationally modified at the neuromuscular junction (NMJ), hence increasing their stability. To date however, the function(s) of the dynamic MT network and its relative stability in the formation and maintenance of NMJs remain poorly described. Stabilization of the MT is dependent in part on its acetylation status, and HDAC6 is capable of reversing this post-translational modification. Here, we report that HDAC6 preferentially accumulates at NMJs and that it contributes to the organization and the stability of NMJs. Indeed, pharmacological inhibition of HDAC6 protects against MT disorganization and reduces the size of acetylcholine receptor (AChR) clusters. Moreover, the endogenous HDAC6 inhibitor paxillin interacts with HDAC6 in skeletal muscle cells, colocalizes with AChR aggregates, and regulates the formation of AChR. Our findings indicate that the focal insertion of AChRs into the postsynaptic membrane is regulated by stable MTs and highlight how an MT/HDAC6/paxillin axis participates in the regulation of AChR insertion and removal to control the structure of NMJs.

Paxillin Is Required for Proper Spinal Motor Axon Growth into the Limb

To assemble the functional circuits of the nervous system, the neuronal axonal growth cones must be precisely guided to their proper targets, which can be achieved through cell-surface guidance receptor activation by ligand binding in the periphery. We investigated the function of paxillin, a focal adhesion protein, as an essential growth cone guidance intermediary in the context of spinal lateral motor column (LMC) motor axon trajectory selection in the limb mesenchyme. Using in situ mRNA detection, we first show paxillin expression in LMC neurons of chick and mouse embryos at the time of spinal motor axon extension into the limb. Paxillin loss-of-function and gain-of-function using in ovo electroporation in chick LMC neurons, of either sex, perturbed LMC axon trajectory selection, demonstrating an essential role of paxillin in motor axon guidance. In addition, a neuron-specific paxillin deletion in mice led to LMC axon trajectory selection errors. We also show that knocking down paxillin attenuates the growth preference of LMC neurites against ephrins in vitro, and erythropoietin-producing human hepatocellular (Eph)-mediated retargeting of LMC axons in vivo, suggesting paxillin involvement in Eph-mediated LMC motor axon guidance. Finally, both paxillin knockdown and ectopic expression of a nonphosphorylable paxillin mutant attenuated the retargeting of LMC axons caused by Src overexpression, implicating paxillin as a Src target in Eph signal relay in this context. In summary, our findings demonstrate that paxillin is required for motor axon guidance and suggest its essential role in the ephrin-Eph signaling pathway resulting in motor axon trajectory selection.SIGNIFICANCE STATEMENT During the development of neural circuits, precise connections need to be established among neurons or between neurons and their muscle targets. A protein family found in neurons, Eph, is essential at different stages of neural circuit formation, including nerve outgrowth and pathfinding, and is proposed to mediate the onset and progression of several neurodegenerative diseases, such as Alzheimer's disease. To investigate how Ephs relay their signals to mediate nerve growth, we investigated the function of a molecule called paxillin and found it important for the development of spinal nerve growth toward their muscle targets, suggesting its role as an effector of Eph signals. Our work could thus provide new information on how neuromuscular connectivity is properly established during embryonic development.

MiR-216b regulates the tumorigenesis of gastric cancer by targeting PXN

BACKGROUND

Accumulating evidence has demonstrated that microRNAs (miRNAs) are associated with tumorigenesis. miR-216b can play a vital role in the genesis and development of gastric cancer (GC), and its molecular mechanisms require further elucidation.

METHODS

The biological effects of miR-216b in GC cells were investigated by MTT, transwell assays, and cell cycle. Western blot and luciferase assay were performed to demonstrate the direct binding of miR-216b on PXN 3'UTR. Furthermore, MTT, colony formation assays, transwell assays, and flow cytometry analysis, as well as xenograft mice model, were used to measure the effects of miR-216b-PXN on GC cell proliferation, migration, and invasion indicated by in vitro and in vivo.

RESULTS

Our results showed that miR-216b acted as a tumor suppressor in GC progression. miR-216b overexpression suppressed GC cell proliferation, migration, and invasion in vitro. Luciferase reporter assays identified paxillin (PXN) as a novel target gene of miR-216b. PXN overexpression could partially rescue miR-216b-induced the inhibitory effects in GC cells. Besides, overexpression of miR-216b contributed to the activation of PI3K/AKT signaling via partly regulating PXN in GC cells.

CONCLUSIONS

The above results showed that miR-216b could offer a novel therapeutic avenue by targeting PXN in GC.

The Adhesome Network: Key Components Shaping the Tumour Stroma

Beyond the conventional perception of solid tumours as mere masses of cancer cells, advanced cancer research focuses on the complex contributions of tumour-associated host cells that are known as "tumour microenvironment" (TME). It has been long appreciated that the tumour stroma, composed mainly of blood vessels, cancer-associated fibroblasts and immune cells, together with the extracellular matrix (ECM), define the tumour architecture and influence cancer cell properties. Besides soluble cues, that mediate the crosstalk between tumour and stroma cells, cell adhesion to ECM arises as a crucial determinant in cancer progression. In this review, we discuss how adhesome, the intracellular protein network formed at cell adhesions, regulate the TME and control malignancy. The role of adhesome extends beyond the physical attachment of cells to ECM and the regulation of cytoskeletal remodelling and acts as a signalling and mechanosensing hub, orchestrating cellular responses that shape the tumour milieu.

MITF reprograms the extracellular matrix and focal adhesion in melanoma

The microphthalmia-associated transcription factor (MITF) is a critical regulator of melanocyte development and differentiation. It also plays an important role in melanoma where it has been described as a molecular rheostat that, depending on activity levels, allows reversible switching between different cellular states. Here, we show that MITF directly represses the expression of genes associated with the extracellular matrix (ECM) and focal adhesion pathways in human melanoma cells as well as of regulators of epithelial-to-mesenchymal transition (EMT) such as CDH2, thus affecting cell morphology and cell-matrix interactions. Importantly, we show that these effects of MITF are reversible, as expected from the rheostat model. The number of focal adhesion points increased upon MITF knockdown, a feature observed in drug-resistant melanomas. Cells lacking MITF are similar to the cells of minimal residual disease observed in both human and zebrafish melanomas. Our results suggest that MITF plays a critical role as a repressor of gene expression and is actively involved in shaping the microenvironment of melanoma cells in a cell-autonomous manner.