Tensins: Bridging AMP-Activated Protein Kinase with Integrin Activation

Fibroblast integrin α11β1 is a collagen assembly receptor in mechanoregulated fibrillar adhesions

Solid epithelial cancers with significant desmoplasia are characterized by an excessive deposition of collagen-based matrix, which often supports tumor progression. However, the mechanism of how collagen receptors mediate collagen fibrillogenesis still remains mostly unclear. We show that the collagen-binding integrin α11β1 can co-localize with tensin-1 and deposited collagen I in human pancreatic ductal adenocarcinoma (PDAC) stroma. In addition to the canonical fibrillar adhesion integrin α5β1 expressed by human PDAC cancer-associated fibroblasts (CAFs), tensin-1-positive fibrillar adhesions contained α11β1 but lacked α1β1 and α2β1. CAFs lacking α5β1 expression displayed mechanoregulated and tensin-1 dependent α11β1 fibrillar adhesions, suggesting independent roles of the two integrins with regards to fibrillar adhesions-based de novo fibrillogenesis. Further, we demonstrate that cell surface-associated collagen I assembly necessitated α11β1, but not α5β1 expression. In summary, α11β1 integrin is a novel component of fibrillar adhesions, which is strategically positioned to mediate de novo collagen fibrillogenesis at the cell surface under pro-fibrotic conditions.

Irisin reduces senile osteoporosis by inducing osteocyte mitophagy through Ampk activation

Irisin, an exercise-induced myokine, is known to be able to regulate bone metabolism. However, the underlying mechanisms regarding the effects of irisin on senile osteoporosis have not been fully elucidated. Here, we demonstrated that irisin can inhibit bone mass loss and bone microarchitecture alteration in senile osteoporosis mouse model. In addition, irisin has effects on bone remodeling that is in favor of bone formation. Remarkably, irisin induced autophagy in osteocytes demonstrated by increased LC3-positive osteocytes, and increased autophagy-related genes and proteins. In vitro analysis revealed that Irisin can prevent mitochondrial oxidative damage. Furthermore, irisin can obviously induce osteocyte mitophagy and increased phosphorylation of Ampk and Ulk1. Inhibition of Ampk signaling recapitulated the biological effect of irisin loss, accompanied by the markedly lower expression of Ulk1. Taken together, our findings show that irisin reduces age-related bone loss by inducing osteocyte mitophagy via Ampk-dependent activation of Ulk1.

The mechanoreceptor Piezo is required for spermatogenesis in Bombyx mori

BACKGROUND

The animal sperm shows high diversity in morphology, components, and motility. In the lepidopteran model insect, the silkworm Bombyx mori, two types of sperm, including nucleate fertile eupyrene sperm and anucleate unfertile apyrene sperm, are generated. Apyrene sperm assists fertilization by facilitating the migration of eupyrene spermatozoa from the bursa copulatrix to the spermatheca. During spermatogenesis, eupyrene sperm bundles extrude the cytoplasm by peristaltic squeezing, while the nuclei of the apyrene sperm bundles are discarded with the same process, forming matured sperm.

RESULTS

In this study, we describe that a mechanoreceptor BmPiezo, the sole Piezo ortholog in B. mori, plays key roles in larval feeding behavior and, more importantly, is essential for eupyrene spermatogenesis and male fertility. CRISPR/Cas9-mediated loss of BmPiezo function decreases larval appetite and subsequent body size and weight. Immunofluorescence analyses reveal that BmPiezo is intensely localized in the inflatable point of eupyrene sperm bundle induced by peristaltic squeezing. BmPiezo is also enriched in the middle region of apyrene sperm bundle before peristaltic squeezing. Cytological analyses of dimorphic sperm reveal developmental arrest of eupyrene sperm bundles in BmPiezo mutants, while the apyrene spermatogenesis is not affected. RNA-seq analysis and q-RT-PCR analyses demonstrate that eupyrene spermatogenic arrest is associated with the dysregulation of the actin cytoskeleton. Moreover, we show that the deformed eupyrene sperm bundles fail to migrate from the testes, resulting in male infertility due to the absence of eupyrene sperm in the bursa copulatrix and spermatheca.

CONCLUSIONS

In conclusion, our studies thus uncover a new role for Piezo in regulating spermatogenesis and male fertility in insects.

Genetic risk factors for severe and fatigue dominant long COVID and commonalities with ME/CFS identified by combinatorial analysis

BACKGROUND

Long COVID is a debilitating chronic condition that has affected over 100 million people globally. It is characterized by a diverse array of symptoms, including fatigue, cognitive dysfunction and respiratory problems. Studies have so far largely failed to identify genetic associations, the mechanisms behind the disease, or any common pathophysiology with other conditions such as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) that present with similar symptoms.

METHODS

We used a combinatorial analysis approach to identify combinations of genetic variants significantly associated with the development of long COVID and to examine the biological mechanisms underpinning its various symptoms. We compared two subpopulations of long COVID patients from Sano Genetics' Long COVID GOLD study cohort, focusing on patients with severe or fatigue dominant phenotypes. We evaluated the genetic signatures previously identified in an ME/CFS population against this long COVID population to understand similarities with other fatigue disorders that may be triggered by a prior viral infection. Finally, we also compared the output of this long COVID analysis against known genetic associations in other chronic diseases, including a range of metabolic and neurological disorders, to understand the overlap of pathophysiological mechanisms.

RESULTS

Combinatorial analysis identified 73 genes that were highly associated with at least one of the long COVID populations included in this analysis. Of these, 9 genes have prior associations with acute COVID-19, and 14 were differentially expressed in a transcriptomic analysis of long COVID patients. A pathway enrichment analysis revealed that the biological pathways most significantly associated with the 73 long COVID genes were mainly aligned with neurological and cardiometabolic diseases. Expanded genotype analysis suggests that specific SNX9 genotypes are a significant contributor to the risk of or protection against severe long COVID infection, but that the gene-disease relationship is context dependent and mediated by interactions with KLF15 and RYR3. Comparison of the genes uniquely associated with the Severe and Fatigue Dominant long COVID patients revealed significant differences between the pathways enriched in each subgroup. The genes unique to Severe long COVID patients were associated with immune pathways such as myeloid differentiation and macrophage foam cells. Genes unique to the Fatigue Dominant subgroup were enriched in metabolic pathways such as MAPK/JNK signaling. We also identified overlap in the genes associated with Fatigue Dominant long COVID and ME/CFS, including several involved in circadian rhythm regulation and insulin regulation. Overall, 39 SNPs associated in this study with long COVID can be linked to 9 genes identified in a recent combinatorial analysis of ME/CFS patient from UK Biobank. Among the 73 genes associated with long COVID, 42 are potentially tractable for novel drug discovery approaches, with 13 of these already targeted by drugs in clinical development pipelines. From this analysis for example, we identified TLR4 antagonists as repurposing candidates with potential to protect against long term cognitive impairment pathology caused by SARS-CoV-2. We are currently evaluating the repurposing potential of these drug targets for use in treating long COVID and/or ME/CFS.

CONCLUSION

This study demonstrates the power of combinatorial analytics for stratifying heterogeneous populations in complex diseases that do not have simple monogenic etiologies. These results build upon the genetic findings from combinatorial analyses of severe acute COVID-19 patients and an ME/CFS population and we expect that access to additional independent, larger patient datasets will further improve the disease insights and validate potential treatment options in long COVID.

Reticular adhesions are assembled at flat clathrin lattices and opposed by active integrin α5β1

Reticular adhesions (RAs) consist of integrin αvβ5 and harbor flat clathrin lattices (FCLs), long-lasting structures with similar molecular composition as clathrin-mediated endocytosis (CME) carriers. Why FCLs and RAs colocalize is not known. Here, we show that RAs are assembled at FCLs in a process controlled by fibronectin (FN) and its receptor, integrin α5β1. We observed that cells on FN-rich matrices displayed fewer FCLs and RAs. CME machinery inhibition abolished RAs and live-cell imaging showed that RA establishment requires FCL coassembly. The inhibitory activity of FN was mediated by the activation of integrin α5β1 at Tensin1-positive fibrillar adhesions. Conventionally, endocytosis disassembles cellular adhesions by internalizing their components. Our results present a novel paradigm in the relationship between these two processes by showing that endocytic proteins can actively function in the assembly of cell adhesions. Furthermore, we show this novel adhesion assembly mechanism is coupled to cell migration via unique crosstalk between cell-matrix adhesions.

Tensins in Kidney Function and Diseases

Tensins are focal adhesion proteins that regulate various biological processes, such as mechanical sensing, cell adhesion, migration, invasion, and proliferation, through their multiple binding activities that transduce critical signals across the plasma membrane. When these molecular interactions and/or mediated signaling are disrupted, cellular activities and tissue functions are compromised, leading to disease development. Here, we focus on the significance of the tensin family in renal function and diseases. The expression pattern of each tensin in the kidney, their roles in chronic kidney diseases, renal cell carcinoma, and their potentials as prognostic markers and/or therapeutic targets are discussed in this review.

TFEB controls integrin-mediated endothelial cell adhesion by the regulation of cholesterol metabolism

The dynamic integrin-mediated adhesion of endothelial cells (ECs) to the surrounding ECM is fundamental for angiogenesis both in physiological and pathological conditions, such as embryonic development and cancer progression. The dynamics of EC-to-ECM adhesions relies on the regulation of the conformational activation and trafficking of integrins. Here, we reveal that oncogenic transcription factor EB (TFEB), a known regulator of lysosomal biogenesis and metabolism, also controls a transcriptional program that influences the turnover of ECM adhesions in ECs by regulating cholesterol metabolism. We show that TFEB favors ECM adhesion turnover by promoting the transcription of genes that drive the synthesis of cholesterol, which promotes the aggregation of caveolin-1, and the caveolin-dependent endocytosis of integrin β1. These findings suggest that TFEB might represent a novel target for the pharmacological control of pathological angiogenesis and bring new insights in the mechanism sustaining TFEB control of endocytosis.

Novel γ-sarcoglycan interactors in murine muscle membranes

BACKGROUND

The sarcoglycan complex (SC) is part of a network that links the striated muscle cytoskeleton to the basal lamina across the sarcolemma. The SC coordinates changes in phosphorylation and Ca⁺⁺-flux during mechanical deformation, and these processes are disrupted with loss-of-function mutations in gamma-sarcoglycan (Sgcg) that cause Limb girdle muscular dystrophy 2C/R5.

METHODS

To gain insight into how the SC mediates mechano-signaling in muscle, we utilized LC-MS/MS proteomics of SC-associated proteins in immunoprecipitates from enriched sarcolemmal fractions. Criteria for inclusion were co-immunoprecipitation with anti-Sgcg from C57BL/6 control muscle and under-representation in parallel experiments with Sgcg-null muscle and with non-specific IgG. Validation of interaction was performed in co-expression experiments in human RH30 rhabdomyosarcoma cells.

RESULTS

We identified 19 candidates as direct or indirect interactors for Sgcg, including the other 3 SC proteins. Novel potential interactors included protein-phosphatase-1-catalytic-subunit-beta (Ppp1cb, PP1b) and Na⁺-K⁺-Cl^--co-transporter NKCC1 (SLC12A2). NKCC1 co-localized with Sgcg after co-expression in human RH30 rhabdomyosarcoma cells, and its cytosolic domains depleted Sgcg from cell lysates upon immunoprecipitation and co-localized with Sgcg after detergent permeabilization. NKCC1 localized in proximity to the dystrophin complex at costameres in vivo. Bumetanide inhibition of NKCC1 cotransporter activity in isolated muscles reduced SC-dependent, strain-induced increases in phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2). In silico analysis suggests that candidate SC interactors may cross-talk with survival signaling pathways, including p53, estrogen receptor, and TRIM25.

CONCLUSIONS

Results support that NKCC1 is a new SC-associated signaling protein. Moreover, the identities of other candidate SC interactors suggest ways by which the SC and NKCC1, along with other Sgcg interactors such as the membrane-cytoskeleton linker archvillin, may regulate kinase- and Ca⁺⁺-mediated survival signaling in skeletal muscle.

Sinner or Saint?: Nck Adaptor Proteins in Vascular Biology

The Nck family of modular adaptor proteins, including Nck1 and Nck2, link phosphotyrosine signaling to changes in cytoskeletal dynamics and gene expression that critically modulate cellular phenotype. The Nck SH2 domain interacts with phosphotyrosine at dynamic signaling hubs, such as activated growth factor receptors and sites of cell adhesion. The Nck SH3 domains interact with signaling effectors containing proline-rich regions that mediate their activation by upstream kinases. In vascular biology, Nck1 and Nck2 play redundant roles in vascular development and postnatal angiogenesis. However, recent studies suggest that Nck1 and Nck2 differentially regulate cell phenotype in the adult vasculature. Domain-specific interactions likely mediate these isoform-selective effects, and these isolated domains may serve as therapeutic targets to limit specific protein-protein interactions. In this review, we highlight the function of the Nck adaptor proteins, the known differences in domain-selective interactions, and discuss the role of individual Nck isoforms in vascular remodeling and function.

The roles of integrins in cancer

Integrin-mediated adhesion of cells to the extracellular matrix (ECM) is crucial for the physiological development and functioning of tissues but is pathologically disrupted in cancer. Indeed, abnormal regulation of integrin receptors and ECM ligands allows cancer cells to break down tissue borders, breach into blood and lymphatic vessels, and survive traveling in suspension through body fluids or residing in metabolically or pharmacologically hostile environments. Different molecular and cellular mechanisms responsible for the modulation of integrin adhesive function or mechanochemical signaling are altered and participate in cancer. Cancer development and progression are also bolstered by dysfunctionalities of integrin-mediated ECM adhesion occurring both in tumor cells and in elements of the surrounding tumor microenvironment, such as vascular cells, cancer-associated fibroblasts, and immune cells. Mounting evidence suggests that integrin inhibitors may be effectively exploited to overcome resistance to standard-of-care anti-cancer therapies.

Immunohistochemical Analysis of the Expression of Adhesion Proteins: TNS1, TNS2 and TNS3 in Correlation with Clinicopathological Parameters in Gastric Cancer

Tensins belong to the group of adhesion proteins that are involved in cell adhesion and migration, actin cytoskeleton maintenance and intercellular communication. TNS1, TNS2 and TNS3 proteins expression was evaluated in 90 patients with gastric cancer by immunohistochemistry method. TNS1 was more frequently present in non-differentiated tumors compared to poorly and moderately differentiated tumors (p = 0.016). TNS1 was also more often observed in metastatic tumors compared to those without distant metastases (p = 0.001). TNS2 was more common in moderately differentiated tumors than in poorly or non-differentiated ones (p = 0.041). TNS2 expression was also more frequently present in tumors with peritumoral inflammation (p = 0.041) and with concomitant H. pylori infection (p = 0.023). In contrast, TNS3 protein was more prevalent in moderately than in poorly and non-differentiated tumors (p = 0.023). No significant relationship was found between tensins' expression and the overall survival rate of patients. TNS1 protein expression is associated with a poor-prognosis type of GC. Higher expression of TNS2 is accompanied by peritumoral inflammation and H. pylori infection, which favor the development of GC of a better prognosis, similarly to higher TNS3 protein expression.

The Charming World of the Extracellular Matrix: A Dynamic and Protective Network of the Intestinal Wall

The intestinal extracellular matrix (ECM) represents a complex network of proteins that not only forms a support structure for resident cells but also interacts closely with them by modulating their phenotypes and functions. More than 300 molecules have been identified, each of them with unique biochemical properties and exclusive biological functions. ECM components not only provide a scaffold for the tissue but also afford tensile strength and limit overstretch of the organ. The ECM holds water, ensures suitable hydration of the tissue, and participates in a selective barrier to the external environment. ECM-to-cells interaction is crucial for morphogenesis and cell differentiation, proliferation, and apoptosis. The ECM is a dynamic and multifunctional structure. The ECM is constantly renewed and remodeled by coordinated action among ECM-producing cells, degrading enzymes, and their specific inhibitors. During this process, several growth factors are released in the ECM, and they, in turn, modulate the deposition of new ECM. In this review, we describe the main components and functions of intestinal ECM and we discuss their role in maintaining the structure and function of the intestinal barrier. Achieving complete knowledge of the ECM world is an important goal to understand the mechanisms leading to the onset and the progression of several intestinal diseases related to alterations in ECM remodeling.

Smarce1 and Tensin 4 Are Putative Modulators of Corneoscleral Stiffness

The biomechanical properties of the cornea and sclera are important in the onset and progression of multiple ocular pathologies and vary substantially between individuals, yet the source of this variation remains unknown. Here we identify genes putatively regulating corneoscleral biomechanical tissue properties by conducting high-fidelity ocular compliance measurements across the BXD recombinant inbred mouse set and performing quantitative trait analysis. We find seven cis-eQTLs and non-synonymous SNPs associating with ocular compliance, and show by RT-qPCR and immunolabeling that only two of the candidate genes, Smarce1 and Tns4, showed significant expression in corneal and scleral tissues. Both have mechanistic potential to influence the development and/or regulation of tissue material properties. This work motivates further study of Smarce1 and Tns4 for their role(s) in ocular pathology involving the corneoscleral envelope as well as the development of novel mouse models of ocular pathophysiology, such as myopia and glaucoma.

Mechano-responsiveness of fibrillar adhesions on stiffness-gradient gels

Fibrillar adhesions are important structural and adhesive components in fibroblasts, and are required for fibronectin fibrillogenesis. While nascent and focal adhesions are known to respond to mechanical cues, the mechanoresponsive nature of fibrillar adhesions remains unclear. Here, we used ratiometric analysis of paired adhesion components to determine an appropriate fibrillar adhesion marker. We found that active α5β1-integrin exhibits the most definitive fibrillar adhesion localization compared to other proteins, such as tensin-1, reported to be in fibrillar adhesions. To elucidate the mechanoresponsiveness of fibrillar adhesions, we designed a cost-effective and reproducible technique to fabricate physiologically relevant stiffness gradients on thin polyacrylamide (PA) hydrogels, embedded with fluorescently labelled beads. We generated a correlation curve between bead density and hydrogel stiffness, thus enabling a readout of stiffness without the need for specialized knowhow, such as atomic force microscopy (AFM). We find that stiffness promotes growth of fibrillar adhesions in a tensin-1-dependent manner. Thus, the formation of these extracellular matrix-depositing structures is coupled to the mechanical parameters of the cell environment and may enable cells to fine-tune their matrix environment in response to changing physical conditions.

Statistical Mechanics of Non-Muscle Myosin IIA in Human Bone Marrow-Derived Mesenchymal Stromal Cells Seeded in a Collagen Scaffold: A Thermodynamic Near-Equilibrium Linear System Modified by the Tripeptide Arg-Gly-Asp (RGD)

Mesenchymal stromal cells (MSCs) were obtained from human bone marrow and amplified in cultures supplemented with human platelet lysate. Once semi-confluent, cells were seeded in solid collagen scaffolds that were rapidly colonized by the cells generating a 3D cell scaffold. Here, they acquired a myofibroblast phenotype and when exposed to appropriate chemical stimulus, developed tension and cell shortening, similar to those of striated and smooth muscle cells. Myofibroblasts contained a molecular motor-the non-muscle myosin type IIA (NMMIIA) whose crossbridge (CB) kinetics are dramatically slow compared with striated and smooth muscle myosins. Huxley's equations were used to determine the molecular mechanical properties of NMMIIA. Thank to the great number of NMMIIA molecules, we determined the statistical mechanics (SM) of MSCs, using the grand canonical ensemble which made it possible to calculate various thermodynamic entities such as the chemical affinity, statistical entropy, internal energy, thermodynamic flow, thermodynamic force, and entropy production rate. The linear relationship observed between the thermodynamic force and the thermodynamic flow allowed to establish that MSC-laden in collagen scaffolds were in a near-equilibrium stationary state (affinity ≪ RT), MSCs were also seeded in solid collagen scaffolds functionalized with the tripeptide Arg-Gly-Asp (RGD). This induced major changes in NMMIIA SM particularly by increasing the rate of entropy production. In conclusion, collagen scaffolds laden with MSCs can be viewed as a non-muscle contractile bioengineered tissue operating in a near-equilibrium linear regime, whose SM could be substantially modified by the RGD peptide.

Integrins as biomechanical sensors of the microenvironment

Integrins, and integrin-mediated adhesions, have long been recognized to provide the main molecular link attaching cells to the extracellular matrix (ECM) and to serve as bidirectional hubs transmitting signals between cells and their environment. Recent evidence has shown that their combined biochemical and mechanical properties also allow integrins to sense, respond to and interact with ECM of differing properties with exquisite specificity. Here, we review this work first by providing an overview of how integrin function is regulated from both a biochemical and a mechanical perspective, affecting integrin cell-surface availability, binding properties, activation or clustering. Then, we address how this biomechanical regulation allows integrins to respond to different ECM physicochemical properties and signals, such as rigidity, composition and spatial distribution. Finally, we discuss the importance of this sensing for major cell functions by taking cell migration and cancer as examples.

Cross-Talk Between the Tumor Microenvironment, Extracellular Matrix, and Cell Metabolism in Cancer

The extracellular matrix (ECM) is a complex network of secreted proteins which provides support for tissues and organs. Additionally, the ECM controls a plethora of cell functions, including cell polarity, migration, proliferation, and oncogenic transformation. One of the hallmarks of cancer is altered cell metabolism, which is currently being exploited to develop anti-cancer therapies. Several pieces of evidence indicate that the tumor microenvironment and the ECM impinge on tumor cell metabolism. Therefore, it is essential to understand the contribution of the complex 3D microenvironment in controlling metabolic plasticity and responsiveness to therapies targeting cell metabolism. In this mini-review, we will describe how the tumor microenvironment and cancer-associated fibroblasts dictate cancer cell metabolism, resulting in increased tumor progression. Moreover, we will define the cross-talk between nutrient signaling and the trafficking of the ECM receptors of the integrin family. Finally, we will present recent data highlighting the contribution of nutrient scavenging from the microenvironment to support cancer cells growth under nutrient starvation conditions.

The Cytoskeleton as Regulator of Cell Signaling Pathways

During interphase, filamentous actin, microtubules, and intermediate filaments regulate cell shape, motility, transport, and interactions with the environment. These activities rely on signaling events that control cytoskeleton properties. Recent studies uncovered mechanisms that go far beyond this one-directional flow of information. Thus, the three branches of the cytoskeleton impinge on signaling pathways to determine their activities. We propose that this regulatory role of the cytoskeleton provides sophisticated mechanisms to control the spatiotemporal output and the intensity of signaling events. Specific examples emphasize these emerging contributions of the cytoskeleton to cell physiology. In our opinion, further exploration of these pathways will uncover new concepts of cellular communication that originate from the cytoskeleton.

Hyperactivity of Mek in TNS1 knockouts leads to potential treatments for cystic kidney diseases

Cystic kidney disease is the progressive development of multiple fluid-filled cysts that may severely compromise kidney functions and lead to renal failure. TNS1 (tensin-1) knockout mice develop cystic kidneys and die from renal failure. Here, we have established TNS1-knockout MDCK cells and applied 3D culture system to investigate the mechanism leading to cyst formation. Unlike wild-type MDCK cells, which form cysts with a single lumen, TNS1-knockout cysts contain multiple lumens and upregulated Mek/Erk activities. The multiple lumen phenotype and Mek/Erk hyperactivities are rescued by re-expression of wild-type TNS1 but not the TNS1 mutant lacking a fragment essential for its cell–cell junction localization. Furthermore, Mek inhibitor treatments restore the multiple lumens back to single lumen cysts. Mek/Erk hyperactivities are also detected in TNS1-knockout mouse kidneys. Treatment with the Mek inhibitor trametinib significantly reduces the levels of interstitial infiltrates, fibrosis and dilated tubules in TNS1-knockout kidneys. These studies establish a critical role of subcellular localization of TNS1 in suppressing Mek/Erk signaling and maintaining lumenogenesis, and provide potential therapeutic strategies by targeting the Mek/Erk pathway for cystic kidney diseases.

Cell Adhesion by Integrins

Integrins are heterodimeric cell surface receptors ensuring the mechanical connection between cells and the extracellular matrix. In addition to the anchorage of cells to the extracellular matrix, these receptors have critical functions in intracellular signaling, but are also taking center stage in many physiological and pathological conditions. In this review, we provide some historical, structural, and physiological notes so that the diverse functions of these receptors can be appreciated and put into the context of the emerging field of mechanobiology. We propose that the exciting journey of the exploration of these receptors will continue for at least another new generation of researchers.

Curdione inhibits thrombin-induced platelet aggregation via regulating the AMP-activated protein kinase-vinculin/talin-integrin αIIbβ3 sign pathway

BACKGROUND

Curdione, a sesquiterpene compound isolated from the essential oil of Curcuma aromatica Salisb. inhibits platelet aggregation, suggesting its significant anticoagulant and antithrombotic effects. However, the mechanisms have not been fully elucidated.

HYPOTHESIS

We hypothesized that curdione inhibits thrombin-induced platelet aggregation via regulating the AMP-activated protein kinase-vinculin/talin-integrin αIIbβ3 signaling pathway.

STUDY DESIGN

We performed in vitro assays to evaluate the effect of curdione on thrombin-induced expression levels of the AMPK signaling molecule and integrin αIIbβ3 signaling pathway components.

METHODS

Platelet proteins were extracted from washed human platelets, and the effects of curdione on thrombin-induced platelet aggregation were evaluated. The expression levels of the AMPK signaling molecule and integrin αIIbβ3 signaling pathway-related proteins were examined using western blot and RT-PCR. The binding of vinculin and talin were studied using immunoprecipitation, double immunofluorescence staining and microscale thermophoresis.

RESULTS

Platelet aggregation analysis showed that 0.02 U/ml thrombin significantly induces platelet aggregation. Western blot and RT-PCR analysis revealed that AMPK inhibits the vinculin/talin-mediated integrin αIIbβ3 signaling pathway, and curdione downregulates the thrombin-induced expression of phosphorylated AMPK (P-AMPK) and P-integrin at both the protein and mRNA levels and downregulates vinculin and talin at the protein level. Furthermore, microscale thermophoresis experiments showed that curdione inhibits the binding of vinculin and talin. The results from the immunoprecipitation and double immunofluorescence staining were consistent with the results of the microscale thermophoresis experiments.

CONCLUSION

Curdione inhibits thrombin-induced platelet aggregation via regulating the AMP-activated protein kinase-vinculin/talin-integrin αIIbβ3 signaling pathway, which suggests its therapeutic potential in ethnomedicinal applications as an anti-platelet and anti-thrombotic compound to prevent thrombotic diseases.

Integrin trafficking in cells and tissues

Cell adhesion to the extracellular matrix is fundamental to metazoan multicellularity and is accomplished primarily through the integrin family of cell-surface receptors. Integrins are internalized and enter the endocytic-exocytic pathway before being recycled back to the plasma membrane. The trafficking of this extensive protein family is regulated in multiple context-dependent ways to modulate integrin function in the cell. Here, we discuss recent advances in understanding the mechanisms and cellular roles of integrin endocytic trafficking.

Every step of the way: integrins in cancer progression and metastasis

Cell adhesion to the extracellular matrix is fundamental to tissue integrity and human health. Integrins are the main cellular adhesion receptors that through multifaceted roles as signalling molecules, mechanotransducers and key components of the cell migration machinery are implicated in nearly every step of cancer progression from primary tumour development to metastasis. Altered integrin expression is frequently detected in tumours, where integrins have roles in supporting oncogenic growth factor receptor (GFR) signalling and GFR-dependent cancer cell migration and invasion. In addition, integrins determine colonization of metastatic sites and facilitate anchorage-independent survival of circulating tumour cells. Investigations describing integrin engagement with a growing number of versatile cell surface molecules, including channels, receptors and secreted proteins, continue to lead to the identification of novel tumour-promoting pathways. Integrin-mediated sensing, stiffening and remodelling of the tumour stroma are key steps in cancer progression supporting invasion, acquisition of cancer stem cell characteristics and drug resistance. Given the complexity of integrins and their adaptable and sometimes antagonistic roles in cancer cells and the tumour microenvironment, therapeutic targeting of these receptors has been a challenge. However, novel approaches to target integrins and antagonism of specific integrin subunits in stringently stratified patient cohorts are emerging as potential ways forward.

The role of compartmentalized signaling pathways in the control of mitochondrial activities in cancer cells

Mitochondria are the powerhouse organelles present in all eukaryotic cells. They play a fundamental role in cell respiration, survival and metabolism. Stimulation of G-protein coupled receptors (GPCRs) by dedicated ligands and consequent activation of the cAMP·PKA pathway finely couple energy production and metabolism to cell growth and survival. Compartmentalization of PKA signaling at mitochondria by A-Kinase Anchor Proteins (AKAPs) ensures efficient transduction of signals generated at the cell membrane to the organelles, controlling important aspects of mitochondrial biology. Emerging evidence implicates mitochondria as essential bioenergetic elements of cancer cells that promote and support tumor growth and metastasis. In this context, mitochondria provide the building blocks for cellular organelles, cytoskeleton and membranes, and supply all the metabolic needs for the expansion and dissemination of actively replicating cancer cells. Functional interference with mitochondrial activity deeply impacts on cancer cell survival and proliferation. Therefore, mitochondria represent valuable targets of novel therapeutic approaches for the treatment of cancer patients. Understanding the biology of mitochondria, uncovering the molecular mechanisms regulating mitochondrial activity andmapping the relevant metabolic and signaling networks operating in cancer cells will undoubtly contribute to create a molecular platform to be used for the treatment of proliferative disorders. Here, we will highlight the emerging roles of signaling pathways acting downstream to GPCRs and their intersection with the ubiquitin proteasome system in the control of mitochondrial activity in different aspects of cancer cell biology.

Extracellular matrix internalization links nutrient signalling to invasive migration

Integrins are the key mediators of cell-extracellular matrix (ECM) interaction, linking the ECM to the actin cytoskeleton. Besides localizing at the cell surface, they can be internalized and transported back to the plasma membrane (recycled) or delivered to the late endosomes/lysosomes for degradation. We and others have shown that integrin can be endocytosed together with their ECM ligands. In this short review, I will highlight how extracellular protein (including ECM) endocytosis impinges on the activation of the mechanistic target of rapamycin (mTOR) pathway, a master regulator of cell metabolism and growth. This supports the intriguing hypothesis that ECM components may be considered as nutrient sources, primarily under soluble nutrient-depleted conditions.