Integrins, adhesion and apoptosis

Molecular force-induced liberation of transforming growth factor-beta remodels the spleen for ectopic liver regeneration

BACKGROUND & AIMS

Ectopic liver regeneration in the spleen is a promising alternative to organ transplantation for treating liver failure. To accommodate transplanted liver cells, the splenic tissue must undergo structural changes to increase extracellular matrix content, demanding a safe and efficient approach for tissue remodelling.

METHODS

We synthesised sulphated hyaluronic acid (sHA) with an affinity for the latent complex of transforming growth factor-β (TGF-β) and cross-linked it into a gel network (sHA-X) via click chemistry. We injected this glycan into the spleens of mice to induce splenic tissue remodelling via supraphysiological activation of endogenous TGF-β.

RESULTS

sHA-X efficiently bound to the abundant latent TGF-β in the spleen. It provided the molecular force to liberate the active TGF-β dimers from their latent complex, mimicking the 'bind-and-pull' mechanism required for physiological activation of TGF-β and reshaping the splenic tissue to support liver cell growth. Hepatocytes transplanted into the remodelled spleen developed into liver tissue with sufficient volume to rescue animals with a metabolic liver disorder (Fah-/- transgenic model) or following 90% hepatectomy, with no adverse effects observed and no additional drugs required.

CONCLUSION

Our findings highlight the efficacy and translational potential of using sHA-X to remodel a specific organ by mechanically activating one single cytokine, representing a novel strategy for the design of biomaterials-based therapies for organ regeneration.

IMPACT AND IMPLICATIONS

Cell transplantation may provide a lifeline to millions of patients with end-stage liver diseases, but their severely damaged livers being unable to accommodate the transplanted cells is a crucial hurdle. Herein, we report an approach to restore liver functions in another organ - the spleen - by activating one single growth factor in situ. This approach, based on a chemically designed polysaccharide that can mechanically liberate the active transforming growth factor-β to an unusually high level, promotes the function of abundant allogenic liver cells in the spleen, rescuing animals from lethal models of liver diseases and showing a high potential for clinical translation.

Uncovering a novel role of focal adhesion and interferon-gamma in cellular rejection of kidney allografts at single cell resolution

Background

Kidney transplant recipients are currently treated with nonspecific immunosuppressants that cause severe systemic side effects. Current immunosuppressants were developed based on their effect on T-cell activation rather than the underlying mechanisms driving alloimmune responses. Thus, understanding the role of the intragraft microenvironment will help us identify more directed therapies with lower side effects.

Methods

To understand the role of the alloimmune response and the intragraft microenvironment in cellular rejection progression, we conducted a Single nucleus RNA sequencing (snRNA-seq) on one human non-rejecting kidney allograft sample, one borderline sample, and T-cell mediated rejection (TCMR) sample (Banff IIa). We studied the differential gene expression and enriched pathways in different conditions, in addition to ligand-receptor (L-R) interactions.

Results

Pathway analysis of T-cells in borderline sample showed enrichment for allograft rejection pathway, suggesting that the borderline sample reflects an early rejection. Hence, this allows for studying the early stages of cellular rejection. Moreover, we showed that focal adhesion (FA), IFNg pathways, and endomucin (EMCN) were significantly upregulated in endothelial cell clusters (ECs) of borderline compared to ECs TCMR. Furthermore, we found that pericytes in TCMR seem to favor endothelial permeability compared to borderline. Similarly, T-cells interaction with ECs in borderline differs from TCMR by involving DAMPS-TLRs interactions.

Conclusion

Our data revealed novel roles of T-cells, ECs, and pericytes in cellular rejection progression, providing new clues on the pathophysiology of allograft rejection.

An evolutionarily conserved coronin-dependent pathway defines cell population size

Maintenance of cell population size is fundamental to the proper functioning of multicellular organisms. Here, we describe a cell-intrinsic cell density–sensing pathway that enabled T cells to reach and maintain an appropriate population size. This pathway operated “kin-to-kin” or between identical or similar T cell populations occupying a niche within a tissue or organ, such as the lymph nodes, spleen, and blood. We showed that this pathway depended on the cell density–dependent abundance of the evolutionarily conserved protein coronin 1, which coordinated prosurvival signaling with the inhibition of cell death until the cell population reached threshold densities. At or above threshold densities, coronin 1 expression peaked and remained stable, thereby resulting in the initiation of apoptosis through kin-to-kin intercellular signaling to return the cell population to the appropriate cell density. This cell population size-controlling pathway was conserved from amoeba to humans, thus providing evidence for the existence of a coronin-regulated, evolutionarily conserved mechanism by which cells are informed of and coordinate their relative population size.

Selectivity of the collagen-binding integrin inhibitors, TC-I-15 and obtustatin

Integrins are a family of 24 adhesion receptors which are both widely-expressed and important in many pathophysiological cellular processes, from embryonic development to cancer metastasis. Hence, integrin inhibitors are valuable research tools which may have promising therapeutic uses. Here, we focus on the four collagen-binding integrins α1β1, α2β1, α10β1 and α11β1. TC-I-15 is a small molecule inhibitor of α2β1 that inhibits platelet adhesion to collagen and thrombus deposition, and obtustatin is an α1β1-specific disintegrin that inhibits angiogenesis. Both inhibitors were applied in cellular adhesion studies, using synthetic collagen peptide coatings with selective affinity for the different collagen-binding integrins and testing the adhesion of C2C12 cells transfected with each. Obtustatin was found to be specific for α1β1, as described, whereas TC-I-15 is shown to be non-specific, since it inhibits both α1β1 and α11β1 as well as α2β1. TC-I-15 was 100-fold more potent against α2β1 binding to a lower-affinity collagen peptide, suggestive of a competitive mechanism. These results caution against the use of integrin inhibitors in a therapeutic or research setting without testing for cross-reactivity.

Cell-Matrix Interactions in the Eye: From Cornea to Choroid

The extracellular matrix (ECM) plays a crucial role in all parts of the eye, from maintaining clarity and hydration of the cornea and vitreous to regulating angiogenesis, intraocular pressure maintenance, and vascular signaling. This review focuses on the interactions of the ECM for homeostasis of normal physiologic functions of the cornea, vitreous, retina, retinal pigment epithelium, Bruch's membrane, and choroid as well as trabecular meshwork, optic nerve, conjunctiva and tenon's layer as it relates to glaucoma. A variety of pathways and key factors related to ECM in the eye are discussed, including but not limited to those related to transforming growth factor-β, vascular endothelial growth factor, basic-fibroblastic growth factor, connective tissue growth factor, matrix metalloproteinases (including MMP-2 and MMP-9, and MMP-14), collagen IV, fibronectin, elastin, canonical signaling, integrins, and endothelial morphogenesis consistent of cellular activation-tubulogenesis and cellular differentiation-stabilization. Alterations contributing to disease states such as wound healing, diabetes-related complications, Fuchs endothelial corneal dystrophy, angiogenesis, fibrosis, age-related macular degeneration, retinal detachment, and posteriorly inserted vitreous base are also reviewed.

Real-time and wide-field mapping of cell-substrate adhesion gap and its evolution via surface plasmon resonance holographic microscopy

As one of the most common biological phenomena, cell adhesion plays a vital role in the cellular activities such as the growth and apoptosis, attracting tremendous research interests over the past decades. Taking the cell evolution under drug injection as an example, the dynamics of cell-substrate adhesion gap can provide valuable information in the fundamental research of cell contacts. A robust technique of monitoring the cell adhesion gap and its evolution in real time is highly desired. Herein, we develop a surface plasmon resonance holographic microscopy to achieve the novel functionality of real-time and wide-field mapping of the cell-substrate adhesion gap and its evolution in situ. The cell adhesion gap images of mouse osteoblast cells and human breast cancer cells have been effectively extracted in a dynamic and label-free manner. The proposed technique opens up a new avenue of revealing the cell-substrate interaction mechanism and renders the wide applications in the biosensing area.

PRESCIENT: platform for the rapid evaluation of antibody success using integrated microfluidics enabled technology

Identifying antibodies (Abs) that neutralize infectious agents is the first step for developing therapeutics, vaccines, and diagnostic tools for these infectious agents. However, current approaches for identifying neutralizing Abs (nAbs) typically rely on dilution-based assays that are costly, inefficient, and only survey a small subset of the entire repertoire. There are also intrinsic biases in many steps of conventional nAb identification processes. More importantly, conventional assays rely on simple Ab-antigen binding assays, which may not result in identifying the most potent nAbs, as the strongest binder may not be the most potent nAb. Droplet microfluidic systems have the capability to overcome such limitations by conducting complex multi-step assays with high reliability, resolution, and throughput in a pico-liter volume water-in-oil emulsion droplet format. Here, we describe the development of PRESCIENT (Platform for the Rapid Evaluation of antibody SucCess using Integrated microfluidics ENabled Technology), a droplet microfluidic system that can enable high-throughput single-cell resolution identification of nAb repertoires elicited in response to viral infection. We demonstrate PRESCIENT's ability to identify Abs that neutralize a model viral agent, Murine coronavirus (murine hepatitis virus), which causes high mortality rates in experimentally infected mice. In-droplet infection of host cells by the virus was first demonstrated, followed by demonstration of in-droplet neutralization by nAbs produced from a single Ab-producing hybridoma cell. Finally, fluorescence intensity analyses of two populations of hybridoma cell lines (nAb-producing and non-nAb-producing hybridoma cell lines) successfully discriminated between the two populations. The presented strategy and platform have the potential to identify and investigate neutralizing activities against a broad range of potential infectious agents for which nAbs have yet to be discovered, significantly advancing the nAb identification process as well as reinvigorating the field of Ab discovery, characterization, and development.

Aggregatibacter actinomycetemcomitans leukotoxin causes activation of lymphocyte function-associated antigen 1

Repeats-in-toxin leukotoxin (LtxA) produced by the oral bacterium Aggregatibacter actinomycetemcomitans kills human leukocytes in a lymphocyte function-associated antigen 1 (LFA-1, integrin α_L /β₂ )-dependent manner, although the mechanism for this interaction has not been identified. The LtxA internalisation by LFA-1-expressing cells was explored with florescence resonance energy transfer (FRET) microscopy using a cell line that expresses LFA-1 with a cyan fluorescent protein-tagged cytosolic α_L domain and a yellow fluorescent protein-tagged β₂ domain. Phorbol 12-myristate 13-acetate activation of LFA-1 caused transient cytosolic domain separation. However, addition of LtxA resulted in an increase in FRET, indicating that LtxA brings the cytosolic domains closer together, compared with the inactive state. Unlike activation, this effect was not transient, lasting more than 30 min. Equilibrium constants of LtxA binding to the cytoplasmic domains of both α_L and β₂ were determined using surface plasmon resonance. LtxA has a strong affinity for the cytosolic domains of both the α_L and β₂ subunits (K_d  = 15 and 4.2 nM, respectively) and a significantly lower affinity for the cytoplasmic domains of other integrin α_M , α_X , and β₃ subunits (K_d  = 400, 180, and 230 nM, respectively), used as controls. Peptide fragments of α_L and β₂ show that LtxA binds membrane-proximal domain of α_L and intermediate domain of β₂ .

Integrin targeting of glyphosate and its cell adhesion modulation effects on osteoblastic MC3T3-E1 cells revealed by label-free optical biosensing

This study is a discovery of interesting and far reaching properties of the world leading herbicide active ingredient glyphosate. Here we demonstrate the cell adhesion-modifying characteristics of glyphosate affecting cellular interactions via Arg-Gly-Asp (RGD)-dependent integrins. This conclusion was supported by the observations that a glyphosate surface coating induced integrin-specific cell adhesion, while glyphosate in solution inhibited cell adhesion on an RGD-displaying surface. A sensitive, real-time, label-free, whole cell approach was used to monitor the cell adhesion kinetic processes with excellent data quality. The half maximal inhibitory concentration (IC50) for glyphosate was determined to be 0.47 ± 0.07% (20.6 mM) in serum-free conditions. A three-dimensional dissociation constant of 0.352 mM was calculated for the binding between RGD-specific integrins in intact MC3T3-E1 cells and soluble glyphosate by measuring its competition for RGD-motifs binding, while the affinity of those RGD-specific integrins to the RGD-motifs was 5.97 µM. The integrin-targeted affinity of glyphosate was proven using competitive binding assays to recombinant receptor αvβ3. The present study shows not only ligand-binding properties of glyphosate, but also illustrates its remarkable biomimetic power in the case of cell adhesion.

Stromal extracellular matrix is a microenvironmental cue promoting resistance to EGFR tyrosine kinase inhibitors in lung cancer cells

The acquisition of resistance to EGFR tyrosine kinase inhibitors (TKIs) remains a critical problem in lung cancer clinic, but the underlying mechanisms have remained incompletely understood. Although the TKI-induced or -selected genetic changes are known to drive resistance, resistance also occurs in tumor cells without genetic changes through poorly-characterized processes. Here, we show that the extracellular matrix (ECM) from various components of the tumor microenvironment, including neighboring tumor cells and fibroblasts, may be the driver of resistance in the absence of genetic changes. Unlike genetic changes, which may evolve during relatively long time of chronic EGFR TKI treatment to drive resistance, briefly culturing on de-cellularized ECM, or co-culturing with the ECM donor cells, immediately confers resistance to tumor cells that are otherwise sensitive to EGFR TKIs. We show evidence that collagen in the ECM may be its primary constituent driving resistance, at least partly through the collagen receptor Integrin-β1. Intriguingly, such effect of ECM and collagen is dose-dependent and reversible, suggesting a potential clinic-relevant application for targeting this effect. Collectively, our results reveal that the stromal ECM acts as a microenvironmental cue promoting EGFR TKI resistance in lung cancer cells, and targeting collagen and Integrin-β1 may be useful for treating resistance, especially the resistance without clearly-defined genetic changes, for which effective therapeutics are lacking.

Overexpression of Chicken IRF7 Increased Viral Replication and Programmed Cell Death to the Avian Influenza Virus Infection Through TGF-Beta/FoxO Signaling Axis in DF-1

During mammalian viral infections, interferon regulatory factor 7 (IRF7) partners with IRF3 to regulate the type I interferon response. In chickens, however, it is still unclear how IRF7 functions in the host innate immune response, especially given that IRF3 is absent. To further elucidate the functional role of chicken IRF7 during avian influenza virus (AIV) infection, we generated inducible IRF7 overexpression DF-1 cell lines and performed in vitro infection using low pathogenic AIVs (LPAIVs). Overexpression of IRF7 resulted in higher viral replication of H6N2 and H10N7 LPAIVs compared to empty vector control cells regardless of IRF7 expression level. In addition, a high rate of induced cell death was observed due to elevated level of IRF7 upon viral infection. RNA-seq and subsequent transcriptome analysis of IRF7 overexpression and control cells discovered candidate genes possibly controlled by chicken IRF7. Functional annotation revealed potential pathways modulated by IRF7 such as TGF-beta signaling pathway, FoxO signaling pathway and cell structural integrity related pathways. Next, we analyzed the host response alteration due to the IRF7 overexpression and additionally discovered the possible connection of chicken IRF7 and JAK-STAT signaling pathway. These findings suggest that chicken IRF7 could modulate a wide range of cellular processes in the host innate immune response thus meticulous control of IRF7 expression is crucial to the host in response to AIV infection.

Cell-matrix adhesion controls Golgi organization and function through Arf1 activation in anchorage-dependent cells

Cell-matrix adhesion regulates membrane trafficking controlling anchorage-dependent signaling. While a dynamic Golgi complex can contribute to this pathway, its regulation by adhesion remains unclear. Here we report that loss of adhesion dramatically disorganized the Golgi in mouse and human fibroblast cells. Golgi integrity is restored rapidly upon integrin-mediated re-adhesion to FN and is disrupted by integrin blocking antibody. In suspended cells, the cis, cis-medial and trans-Golgi networks differentially disorganize along the microtubule network but show no overlap with the ER, making this disorganization distinct from known Golgi fragmentation. This pathway is regulated by an adhesion-dependent reduction and recovery of Arf1 activation. Constitutively active Arf1 disrupts this regulation and prevents Golgi disorganization due to loss of adhesion. Adhesion-dependent Arf1 activation regulates its binding to the microtubule minus-end motor protein dynein to control Golgi reorganization, which is blocked by ciliobrevin. Adhesion-dependent Golgi organization controls its function, regulating cell surface glycosylation due to loss of adhesion, which is blocked by constitutively active Arf1. This study, hence, identified integrin-dependent cell-matrix adhesion to be a novel regulator of Arf1 activation, controlling Golgi organization and function in anchorage-dependent cells.

This article has an associated First Person interview with the first author of the paper.

Summary: Integrin-dependent cell-matrix adhesion activates Arf1, which then recruits dynein to regulate Golgi organization and function along the microtubule network.

Effects of Transplanted Islets Nano-Encapsulated with Hyperbranched Polyethylene Glycol and Heparin on Microenvironment Reconstruction and Glucose Control

The microenvironment of pancreatic islets gets disrupted during enzyme digestion and causes islets to remain in a vulnerable state, leading to poor outcome in the initial days of transplantation. To avoid immune invasion while allowing the reconstruction of the microenvironment of the transplanted site, we propose immunoisolation polymers, which can nanoencapsulate islets quickly without cytotoxicity. Here, nonhuman primate (NHP) islets were nanoencapsulated with hyperbranched polyethylene glycol (hb-PEG) and heparin by layer-by-layer technology and transplanted into the kidney subcapsular space of diabetic C57BL/6 mice. An immunosuppressive drug protocol was applied to increase the survival time until the animals were sacrificed. The recipients of NHP islets exhibited high nonfasting blood glucose level (BGL) for 2-3 weeks, which was normalized afterward. Immunohistochemical (IHC) analysis revealed an immature vascular basement membrane and cell surface integrins directly associated with poor initial insulin production. The transplanted grafts regained their own microenvironment within a month without any outside stimuli. No lymphocyte infiltration was observed in the grafts at any time. Humoral and cell-mediated immune responses were prominently diminished by the hb-PEG/Heparin nanoencapsulated islets. Immunoisolation accompanied by an immunosuppressive drug protocol protects islets by helping them avoid immunogenesis while at the same time allowing them to reconstruct their microenvironment.

Neuroprotective Effect of CeO2@PAA-LXW7 Against H2O2-Induced Cytotoxicity in NGF-Differentiated PC12 Cells

CeO₂ nanoparticles (nanoceria) have been used in many studies as a powerful free radical scavenger, and LXW7, a small-molecule peptide, can specifically target the integrin αvβ3, whose neuroprotective effects have also been demonstrated. The objective of this study is to observe the neuroprotective effect and potential mechanism of CeO₂@PAA-LXW7, a new compound that couples CeO₂@PAA (nanoceria modified with the functional group of polyacrylic acid) with LXW7 via a series of chemical reactions, in H₂O₂-induced NGF-differentiated PC12 cells. We examined the effects of LXW7, CeO₂@PAA, and CeO₂@PAA-LXW7 on the viability of primary hippocampal neurons and found that there was no significant difference under control conditions, but increased cellular viability was observed in the case of H₂O₂-induced injury. We used H₂O₂-induced NGF-differentiated PC12 cells as the classical injury model to investigate the neuroprotective effect of CeO₂@PAA-LXW7. In this study, LXW7, CeO₂@PAA, and CeO₂@PAA-LXW7 inhibit H₂O₂-induced oxidative stress by reducing the production of reactive oxygen species (ROS) and regulating Bax/Bcl-2, cleaved caspase-3 and mitochondrial cytochrome C (cyto C) in the apoptotic signaling pathways. We found that the levels of phosphorylation of focal adhesion kinase (FAK) and of signal transducer and activator of transcription 3 (STAT3) increased significantly in H₂O₂-induced NGF-differentiated PC12 cells, whereas LXW7, CeO₂@PAA, and CeO₂@PAA-LXW7 suppressed the increase to different degrees. Among the abovementioned changes, the inhibitory effect of CeO₂@PAA-LXW7 on H₂O₂-induced changes, including the increases in the levels of p-FAK and p-STAT3, is more obvious than that of LXW7 or CeO₂@PAA alone. In summary, these results suggest that integrin signaling participates in the regulation of apoptosis via the regulation of ROS and of the apoptosis pathway in H₂O₂-induced NGF-differentiated PC12 cells. LXW7, CeO₂@PAA, and CeO₂@PAA-LXW7 can play neuroprotective roles by counteracting the oxidative stress and apoptosis induced by H₂O₂ in NGF-differentiated PC12 cells. CeO₂@PAA-LXW7 exerting a more powerful synergistic effect via the conjunction of LXW7 and CeO₂@PAA.

Integrin β3 plays a novel role in innate immunity in silkworm, Bombyx mori

Integrins are transmembrane receptors that play essential roles in many physiological and pathological processes through cell-to-cell and cell-to-extracellular matrix (ECM) interactions. In the current study, a 2653-bp full-length cDNA of a novel integrin β subunit (designated Bmintegrin β3) was obtained from silkworm hemocytes. Bmintegrin β3 has the typical conserved structure of the integrin β family. The qRT-PCR results showed that Bmintegrin β3 was specifically expressed in the hematological system and that its expression was significantly increased after challenge with different types of PAMPs and bacteria. The recombinant Bmintegrin β3 protein displayed increased aggregation with S. aureus, suggesting that Bmintegrin β3 might directly bind to PAMPs. Interestingly, Bmintegrin β3 knockdown promoted PPO1, PPO2, BAEE, SPH78, SPH125, and SPH127 expression and accelerated the melanization process. Unexpectedly, the expression of genes related to phagocytosis, the Toll pathway, and the IMD pathway was also up-regulated after Bmintegrin β3 knockdown. Thus, Bmintegrin β3 might be a pattern recognition protein (PRP) for PAMPs and might directly bind to bacteria and enhance the phagocytosis activity of hemocytes. Moreover, Bmintegrin β3 and its ligand might negatively regulate the expression of immune-related genes through an unknown mechanism. In summary, our studies provide new insights into the immune functions of Bmintegrin β3 from the silkworm, Bombyx mori.

Integrins in Vascular Development and Pathology

During vascular development, endothelial cells (ECs) and neighboring stromal cells interact and communicate through autocrine and paracrine signaling mechanisms involving extracellular matrix (ECM) proteins and their cell surface integrin adhesion receptors. Integrin-mediated adhesion and signaling pathways are crucial for normal vascular development and physiology, and alterations in integrin expression and/or function drive several vascular-related pathologies including thrombosis, autoimmune disorders, and cancer. The purpose of this chapter is to discuss integrin adhesion and signaling pathways important for EC growth, survival, and migration. Integrin-mediated paracrine links between ECs and surrounding stromal cells in the organ microenvironment will also be discussed. Lastly, we will review roles for integrins in vascular pathologies and discuss possible targets for therapeutic intervention.

A pH-dependent Antibacterial Peptide Release Nano-system Blocks Tumor Growth in vivo without Toxicity

In this study, we designed a nano-system where a novel antibacterial peptide RGD-hylin a1 with reduced hemolysis than the commonly studied melittin was loaded onto mesoporous silica (HMS). We found out that the designed nano-system, RGD-hylin a1-HMS, released RGD-hylin a1 in a pH-dependent manner. It caused apoptosis of cancer cells at low dosage of the antibacterial peptide at pH = 5.5, but was safe to the cells at pH = 7. The hemolytic activity of RGD-hylin a1 itself was reduced by 50~100% by the nano-system depending on the dosage. When this nano-system was administered to tumor-bearing mice at low dosage via intravenous injection, the growth of the solid tumor was blocked by the RGD-hylin a1-HMS nano-system with a 50–60% inhibition rate relative to the PBS-treated control group in terms of tumor volume and weight. Further, the hemolytic activity of RGD-hylin a1 was completely eliminated within the delivery system with no other side effects observed. This study demonstrates that this smart pH-dependent antibacterial peptide release nano-system has superior potential for solid tumor treatments through intravenous administration. This smart-releasing system has great potential in further clinical applications.

Integrin-FAK signaling rapidly and potently promotes mitochondrial function through STAT3

Background

STAT3 is increasingly becoming known for its non-transcriptional regulation of mitochondrial bioenergetic function upon activation of its S727 residue (S727-STAT3). Lengthy mitochondrial dysfunction can lead to cell death. We tested whether an integrin-FAK-STAT3 signaling pathway we recently discovered regulates mitochondrial function and cell survival, and treatments thereof.

Methods

Cultured mouse brain bEnd5 endothelial cells were treated with integrin, FAK or STAT3 inhibitors, FAK siRNA, as well as integrin and STAT3 activators. STAT3 null cells were transfected with mutant STAT3 plasmids. Outcome measures included oxygen consumption rate for mitochondrial bioenergetics, Western blotting for protein phosphorylation, mitochondrial membrane potential for mitochondrial integrity, ROS production, and cell counts.

Results

Vitronectin-dependent mitochondrial basal respiration, ATP production, and maximum reserve and respiratory capacities were suppressed within 4 h by RGD and αvβ3 integrin antagonist peptides. Conversely, integrin ligands vitronectin, laminin and fibronectin stimulated mitochondrial function. Pharmacological inhibition of FAK completely abolished mitochondrial function within 4 h while FAK siRNA treatments confirmed the specificity of FAK signaling. WT, but not S727A functionally dead mutant STAT3, rescued bioenergetics in cells made null for STAT3 using CRISPR-Cas9. STAT3 inhibition with stattic in whole cells rapidly reduced mitochondrial function and mitochondrial pS727-STAT3. Stattic treatment of isolated mitochondria did not reduce pS727 whereas more was detected upon phosphatase inhibition. This suggests that S727-STAT3 is activated in the cytoplasm and is short-lived upon translocation to the mitochondria. FAK inhibition reduced pS727-STAT3 within mitochondria and reduced mitochondrial function in a non-transcriptional manner, as shown by co-treatment with actinomycin. Treatment with the small molecule bryostatin-1 or hepatocyte growth factor (HGF), which indirectly activate S727-STAT3, preserved mitochondrial function during FAK inhibition, but failed in the presence of the STAT3 inhibitor. FAK inhibition induced loss of mitochondrial membrane potential, which was counteracted by bryostatin, and increased superoxide and hydrogen peroxide production. Bryostatin and HGF reduced the substantial cell death caused by FAK inhibition over a 24 h period.

Conclusion

These data suggest that extracellular matrix molecules promote STAT3-dependent mitochondrial function and cell survival through integrin-FAK signaling. We furthermore show a new treatment strategy for cell survival using S727-STAT3 activators.

The comprehensive immunomodulation of NeurimmiRs in haemocytes of oyster Crassostrea gigas after acetylcholine and norepinephrine stimulation

Background

Neural-endocrine-immune (NEI) system is a major modulation network among the nervous, endocrine and immune system and weights greatly in maintaining homeostasis of organisms during stress and infection. Some microRNAs are found interacting with NEI system (designated NeurimmiRs), addressing swift modulations on immune system. The oyster Crassostrea gigas, as an intertidal bivalve, has evolved a primary NEI system. However, the knowledge about NeurimmiRs in oysters remains largely unknown.

Results

Six small RNA libraries from haemocytes of oysters stimulated with acetylcholine (ACh) and norepinephrine (NE) were sequenced to identify neurotransmitter-responsive miRNAs and survey their immunomodulation roles. A total of 331 miRNAs (132 identified in the present study plus 199 identified previously) were subjected to expression analysis, and twenty-one and sixteen of them were found ACh- or NE-responsive, respectively (FDR < 0.05). Meanwhile, 21 miRNAs exhibited different expression pattern after ACh or NE stimulation. Consequently, 355 genes were predicted as putative targets of these neurotransmitter-responsive miRNAs in oyster. Through gene onthology analysis, multiple genes involved in death, immune system process and response to stimulus were annotated to be modulated by NeurimmiRs. Besides, a significant decrease in haemocyte phagocytosis and late-apoptosis or necrosis rate was observed after ACh and NE stimulation (p < 0.05) while early-apoptosis rate remained unchanged.

Conclusions

A comprehensive immune-related network involving PRRs, intracellular receptors, signaling transducers and immune effectors was proposed to be modulated by ACh- and NE-responsive NeurimmiRs, which would be indispensable for oyster haemocytes to respond against stress and infection. Characterization of the NeurimmiRs would be an essential step to understand the NEI system of invertebrate and the adaptation mechanism of oyster.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2150-8) contains supplementary material, which is available to authorized users.

Dynamic contact angle analysis of protein adsorption on polysaccharide multilayer's films for biomaterial reendothelialization

Atherosclerosis is a major cardiovascular disease. One of the side effects is restenosis. The aim of this work was to study the coating of stents by dextran derivates based polyelectrolyte's multilayer (PEM) films in order to increase endothelialization of injured arterial wall after stent implantation. Films were composed with diethylaminoethyl dextran (DEAE) as polycation and dextran sulphate (DS) as polyanion. One film was composed with 4 bilayers of (DEAE-DS)4 and was labeled D-. The other film was the same as D- but with an added terminal layer of DEAE polycation: (DEAE-DS)4-DEAE (labeled D+). The dynamic adsorption/desorption of proteins on the films were characterized by dynamic contact angle (DCA) and atomic force microscopy (AFM). Human endothelial cell (HUVEC) adhesion and proliferation were quantified and correlated to protein adsorption analyzed by DCA for fibronectin, vitronectin, and bovine serum albumin (BSA). Our results showed that the endothelial cell response was optimal for films composed of DS as external layer. Fibronectin was found to be the only protein to exhibit a reversible change in conformation after desorption test. This behavior was only observed for (DEAE-DS)4 films. (DEAE-DS)4 films could enhance HUVEC proliferation in agreement with fibronectin ability to easily change from conformation.

Molecular mechanisms underlying the divergent roles of SPARC in human carcinogenesis

Communication between the cell and its surrounding environment, consisting of proteinaceous (non-living material) and extracellular matrix (ECM), is important for biophysiological and chemical signaling. This signaling results in a range of cellular activities, including cell division, adhesion, differentiation, invasion, migration and angiogenesis. The ECM non-structural secretory glycoprotein called secreted protein, acidic and rich in cysteine (SPARC), plays a significant role in altering cancer cell activity and the tumor's microenvironment (TME). However, the role of SPARC in cancer research has been the subject of controversy. This review mainly focuses on recent advances in understanding the contradictory nature of SPARC in relation to ECM assembly, cancer cell proliferation, adhesion, migration, apoptosis and tumor growth.

Protein kinase C, focal adhesions and the regulation of cell migration

Cell adhesion to extracellular matrix is a complex process involving protrusive activity driven by the actin cytoskeleton, engagement of specific receptors, followed by signaling and cytoskeletal organization. Thereafter, contractile and endocytic/recycling activities may facilitate migration and adhesion turnover. Focal adhesions, or focal contacts, are widespread organelles at the cell-matrix interface. They arise as a result of receptor interactions with matrix ligands, together with clustering. Recent analysis shows that focal adhesions contain a very large number of protein components in their intracellular compartment. Among these are tyrosine kinases, which have received a great deal of attention, whereas the serine/threonine kinase protein kinase C has received much less. Here the status of protein kinase C in focal adhesions and cell migration is reviewed, together with discussion of its roles and potential substrates.

Αvβ3-integrin-mediated adhesion is regulated through an AAK1L- and EHD3-dependent rapid-recycling pathway

Protein transport through the endosome is critical for maintaining proper integrin cell surface integrin distribution to support cell adhesion, motility and viability. Here we employ a live-cell imaging approach to evaluate the relationship between integrin function and transport through the early endosome. We discovered that two early endosome factors, AAK1L and EHD3, are critical for αvβ3-integrin-mediated cell adhesion in HeLa cells. siRNA-mediated depletion of either factor delays short-loop β3 integrin recycling from the early endosome back to the cell surface. Total internal reflection fluorescence-based colocalization analysis reveals that β3 integrin transits AAK1L- and EHD3-positive endosomes near the cell surface, a subcellular location consistent with a rapid-recycling role for both factors. Moreover, structure-function analysis reveals that AAK1L kinase activity, as well as its C-terminal domain, is essential for cell adhesion maintenance. Taken together, these data reveal an important role for AAK1L and EHD3 in maintaining cell viability and adhesion by promoting αvβ3 integrin rapid recycling from the early endosome.

Bcl-2 family proteins and cytoskeleton changes involved in DM-1 cytotoxic effect on melanoma cells

Melanoma is one of the most aggressive types of skin cancer and its incidence rate is still increasing. All existing treatments are minimally effective. Consequently, new therapeutic agents for melanoma treatment should be developed. The DM-1 compound is a curcumin analog that possesses several curcumin characteristics, such as antiproliferative, antitumor, and anti-metastatic properties. The aim of this study was to evaluate the different signaling pathways involved in the cytotoxic effect of DM-1 on melanoma cells. The apoptotic process and cytoskeletal changes were evaluated by immunoblotting and immunofluorescence, respectively, in melanoma cells. After DM-1 treatment, SK-MEL-5 melanoma cells showed actin filament disorganization with spicule formation throughout the cytoskeleton and significant reduction of focal adhesion as well as they were present only at cell extremities, conferring a poor connection between the cell and the substrate. Besides this, there was significant filopodium retraction and loss of typical cytoskeleton scaffold. These modifications contributed to cell detachment followed by cell death. Furthermore, DM-1-induced apoptosis was triggered by multiple Bcl-2 proteins involved in both the extrinsic and the intrinsic apoptotic pathways. SK-MEL-5 cells showed a death mechanism mainly by Bcl-2/Bax ratio decrease, whereas A375 cells presented apoptosis induction by Mcl-1 and Bcl-xL downregulation. In SK-MEL-5 and A375 melanoma cells, there was a significant increase in the active form of caspase 9, and the inactive form of the effector caspase 3 was decreased in both cell lines. Expression of cleaved poly ADP ribose polymerase was increased after DM-1 treatment in these melanoma cell lines, demonstrating that the apoptotic process occurred. Altogether, these data elucidate the cellular and molecular mechanisms involved in the cytotoxicity induced by the antitumor agent DM-1 in melanoma cells.

New insights into the kinetic resistance to anticancer agents

Kinetic resistance plays a major role in the failure of chemotherapy towards many solid tumors. Kinetic resistance to cytotoxic drugs can be reproduced in vitro by growing the cells as multicellular spheroids (Multicellular Resistance) or as hyperconfluent cultures (Confluence-Dependent Resistance). Recent findings on the cell cycle regulation have permitted a better understanding why cancer cells which arrest in long quiescent phases are poorly sensitive to cell-cycle specific anticancer drugs. Two cyclin-dependent kinase inhibitors (CDKI) seem particularly involved in the cell cycle arrest at the G1 to S transition checkpoint: the p53-dependent p21(cip1) protein which is activated by DNA damage and the p27(kip1) which is a mediator of the contact inhibition signal. Cell quiescence could alter drug-induced apoptosis which is partly dependent on an active progression in the cell cycle and which is facilitated by overexpression of oncogenes such as c-Myc or cyclins. Investigations are yet necessary to determine the influence of the cell cycle on the balance between antagonizing (bcl-2, bcl-X(L)...) or stimulating (Bax, Bcl-X(S), Fas...) factors in chemotherapy-induced apoptosis. Quiescent cells could also be protected from toxic agents by an enhanced expression of stress proteins, such as HSP27 which is induced by confluence. New strategies are required to circumvent kinetic resistance of solid tumors: adequate choice of anticancer agents whose activity is not altered by quiescence (radiation, cisplatin), recruitment from G1 to S/G2 phases by cell pretreatment with alkylating drugs or attenuation of CDKI activity by specific inhibitors.

cAMP signalling protects proximal tubular epithelial cells from cisplatin-induced apoptosis via activation of Epac

BACKGROUND AND PURPOSE

Nephrotoxicity is the principal dose-limiting factor for cisplatin chemotherapy and is primarily associated with proximal tubular epithelial cells, including disruption of cell adhesions and induction of apoptosis. Cell adhesion and survival is regulated by, amongst other factors, the small GTPase Rap and its activator, the exchange protein directly activated by cAMP (Epac). Epac is particularly enriched in renal tubule epithelium. This study investigates the cytoprotective effects of cAMP-Epac-Rap signalling in a model of cisplatin-induced renal cell injury.

EXPERIMENTAL APPROACH

The Epac-selective cAMP analogue 8-pCPT-2'-O-Me-cAMP was used to activate the Epac-Rap signalling pathway in proximal tubular epithelial cells. Cells were exposed to cisplatin, in the presence or absence of 8-pCPT-2'-O-Me-cAMP, and nephrotoxicity was determined by monitoring cell-cell junctions and cell apoptosis.

KEY RESULTS

Activation of Epac-Rap signalling preserves cell-cell junctions and protects against cell apoptosis of mouse proximal tubular cells during cisplatin treatment. Activation with the Epac-selective cAMP analogue 8-pCPT-2'-O-Me-cAMP or receptor-mediated induction of cAMP both induced cytoprotection against cisplatin, whereas a PKA-selective cAMP analogue was not cytoprotective. 8-pCPT-2'-O-Me-cAMP mediated cytoprotection was blocked by RNAi-mediated silencing of Epac-Rap signalling in these cells. In contrast, 8-pCPT-2'-O-Me-cAMP did not protect against cisplatin-induced cell death of cancer cells that lacked Epac1 expression.

CONCLUSIONS AND IMPLICATIONS

Our study identifies activation of Epac-Rap signalling as a potential strategy for reducing the nephrotoxicity associated with cisplatin treatments and, as a result, broadens the therapeutic window of this chemotherapeutic agent.

Collagen VI ablation retards brain tumor progression due to deficits in assembly of the vascular basal lamina

To investigate the importance of the vascular basal lamina in tumor blood vessel morphogenesis and function, we compared vessel development, vessel function, and progression of B16F10 melanoma tumors in the brains of wild-type and collagen VI-null mice. In 7-day tumors in the absence of collagen VI, the width of the vascular basal lamina was reduced twofold. Although the ablation of collagen VI did not alter the abundance of blood vessels, a detailed analysis of the number of either pericytes or endothelial cells (or pericyte coverage of endothelial cells) showed that collagen VI-dependent defects during the assembly of the basal lamina have negative effects on both pericyte maturation and the sprouting and survival of endothelial cells. As a result of these deficits, vessel patency was reduced by 25%, and vessel leakiness was increased threefold, resulting in a 10-fold increase in tumor hypoxia along with a fourfold increase in hypoxia-inducible factor-1α expression. In 12-day collagen VI-null tumors, vascular endothelial growth factor expression was increased throughout the tumor stroma, in contrast to the predominantly vascular pattern of vascular endothelial growth factor expression in wild-type tumors. Vessel size was correspondingly reduced in 12-day collagen VI-null tumors. Overall, these vascular deficits produced a twofold decrease in tumor volume in collagen VI-null mice, confirming that collagen VI-dependent basal lamina assembly is a critical aspect of vessel development.

Oncogenic ras-induced down-regulation of pro-apoptotic protease caspase-2 is required for malignant transformation of intestinal epithelial cells

Resistance of carcinoma cells to anoikis, apoptosis that is normally induced by loss of cell-to-extracellular matrix adhesion, is thought to be essential for the ability of these cells to form primary tumors, invade adjacent tissues, and metastasize to distant organs. Current knowledge about the mechanisms by which cancer cells evade anoikis is far from complete. In an effort to understand these mechanisms, we found that ras, a major oncogene, down-regulates protease caspase-2 (which initiates certain steps of the cellular apoptotic program) in malignant human and rat intestinal epithelial cells. This down-regulation could be reversed by inhibition of a protein kinase Mek, a mediator of Ras signaling. We also found that enforced down-regulation of caspase-2 in nonmalignant intestinal epithelial cells by RNA interference protected them from anoikis. Furthermore, the reversal of the effect of Ras on caspase-2 achieved by the expression of exogenous caspase-2 in detached ras-transformed intestinal epithelial cells promoted well established apoptotic events, such as the release of the pro-apoptotic mitochondrial factors cytochrome c and HtrA2/Omi into the cytoplasm of these cells, significantly enhanced their anoikis susceptibility, and blocked their long term growth in the absence of adhesion to the extracellular matrix. Finally, the blockade of the effect of Ras on caspase-2 substantially suppressed growth of tumors formed by the ras-transformed cells in mice. We conclude that ras-induced down-regulation of caspase-2 represents a novel mechanism by which oncogenic Ras protects malignant intestinal epithelial cells from anoikis, promotes their anchorage-independent growth, and allows them to form tumors in vivo.

Angiogenesis

Extracellular matrix (ECM) is essential for all stages of angiogenesis. In the adult, angiogenesis begins with endothelial cell (EC) activation, degradation of vascular basement membrane, and vascular sprouting within interstitial matrix. During this sprouting phase, ECM binding to integrins provides critical signaling support for EC proliferation, survival, and migration. ECM also signals the EC cytoskeleton to initiate blood vessel morphogenesis. Dynamic remodeling of ECM, particularly by membrane-type matrix metalloproteases (MT-MMPs), coordinates formation of vascular tubes with lumens and provides guidance tunnels for pericytes that assist ECs in the assembly of vascular basement membrane. ECM also provides a binding scaffold for a variety of cytokines that exert essential signaling functions during angiogenesis. In the embryo, ECM is equally critical for angiogenesis and vessel stabilization, although there are likely important distinctions from the adult because of differences in composition and abundance of specific ECM components.

Tissue inhibitor of metalloproteinase 1 expression associated with gene demethylation confers anoikis resistance in early phases of melanocyte malignant transformation

Although anoikis resistance has been considered a hallmark of malignant phenotype, the causal relation between neoplastic transformation and anchorage-independent growth remains undefined. We developed an experimental model of murine melanocyte malignant transformation, where a melanocyte lineage (melan-a) was submitted to sequential cycles of anchorage blockade, resulting in progressive morphologic alterations, and malignant transformation. Throughout this process, cells corresponding to premalignant melanocytes and melanoma cell lines were established and show progressive anoikis resistance and increased expression of Timp1. In melan-a melanocytes, Timp1 expression is suppressed by DNA methylation as indicated by its reexpression after 5-aza-2'-deoxycytidine treatment. Methylation-sensitive single-nucleotide primer extension analysis showed increased demethylation in Timp1 in parallel with its expression along malignant transformation. Interestingly, TIMP1 expression has already been related with negative prognosis in some human cancers. Although described as a MMP inhibitor, this protein has been associated with apoptosis resistance in different cell types. Melan-a cells overexpressing Timp1 showed increased survival in suspension but were unable to form tumors in vivo, whereas Timp1-overexpressing melanoma cells showed reduced latency time for tumor appearance and increased metastatic potential. Here, we demonstrated for the first time an increment in Timp1 expression since the early phases of melanocyte malignant transformation, associated to a progressive gene demethylation, which confers anoikis resistance. In this way, Timp1 might be considered as a valued marker for melanocyte malignant transformation.

Integrin signaling, cell survival, and anoikis: distinctions, differences, and differentiation

Cell survival and apoptosis implicate an increasing complexity of players and signaling pathways which regulate not only the decision-making process of surviving (or dying), but as well the execution of cell death proper. The same complex nature applies to anoikis, a form of caspase-dependent apoptosis that is largely regulated by integrin-mediated, cell-extracellular matrix interactions. Not surprisingly, the regulation of cell survival, apoptosis, and anoikis furthermore implicates additional mechanistic distinctions according to the specific tissue, cell type, and species. Incidentally, studies in recent years have unearthed yet another layer of complexity in the regulation of these cell processes, namely, the implication of cell differentiation state-specific mechanisms. Further analyses of such differentiation state-distinct mechanisms, either under normal or physiopathological contexts, should increase our understanding of diseases which implicate a deregulation of integrin function, cell survival, and anoikis.

Bcl-xL-inhibitory BH3 mimetics can induce a transient thrombocytopathy that undermines the hemostatic function of platelets

BH3 mimetics are a new class of proapo-ptotic anticancer agents that have shown considerable promise in preclinical animal models and early-stage human trials. These agents act by inhibiting the pro-survival function of one or more Bcl-2-related proteins. Agents that inhibit Bcl-x(L) induce rapid platelet death that leads to thrombocytopenia; however, their impact on the function of residual circulating platelets remains unclear. In this study, we demonstrate that the BH3 mimetics, ABT-737 or ABT-263, induce a time- and dose-dependent decrease in platelet adhesive function that correlates with ectodomain shedding of the major platelet adhesion receptors, glycoprotein Ibα and glycoprotein VI, and functional down-regulation of integrin α(IIb)β(3). Analysis of platelets from mice treated with higher doses of BH3 mimetics revealed the presence of a subpopulation of circulating platelets undergoing cell death that have impaired activation responses to soluble agonists. Functional analysis of platelets by intravital microscopy revealed a time-dependent defect in platelet aggregation at sites of vascular injury that correlated with an increase in tail bleeding time. Overall, these studies demonstrate that Bcl-x(L)-inhibitory BH3 mimetics not only induce thrombocytopenia but also a transient thrombocytopathy that can undermine the hemostatic function of platelets.

TNFalpha accelerates monocyte to endothelial transdifferentiation in tumors by the induction of integrin alpha5 expression and adhesion to fibronectin

Tumor-associated myeloid cells are believed to promote tumor development by stimulating tumor growth, angiogenesis, invasion, and metastasis. Tumor-associated myeloid cells that coexpress endothelial and myeloid markers represent a proangiogenic subpopulation known as vascular leukocytes. Recently, we and others had shown that tumor-derived TNFα promotes local tumor growth and vascularity. Our data suggested that tumor growth is in part due to TNFα-mediated increased numbers of tumor-associated vascular leukocytes (i.e., myeloid-endothelial biphenotypic cells). The work detailed herein explored the mechanism by which TNFα mediates endothelial differentiation of myeloid cells. Our studies showed that fibronectin is a robust facilitator of endothelial differentiation of blood mononuclear cells in vitro. We have found that TNFα treatment of monocytes significantly increased expression of α(5)β(1) integrin, a major fibronectin receptor enriched on endothelial cells, leading to a consequent fourfold increase in fibronectin adhesion. Furthermore, TNFα-treated monocytes upregulated expression of endothelial markers, flk-1(VEGFR2/KDR) and VE-cadherin. Integrin α(5) subunit inhibitory antibodies blocked adhesion to fibronectin as well as consequent upregulation of flk-1 and VE-cadherin transcripts, implying a role for outside-in signaling by the α(5)β(1) integrin after binding fibronectin. Finally, treatment of mouse tumors with anti-α(5) antibodies reduced accumulation of tumor vascular leukocytes in vivo. Our studies suggest that tumor cell-derived TNFα constitutes a tumor microenvironment signal that promotes differentiation of tumor-associated monocytes toward a proangiogenic/provasculogenic myeloid-endothelial phenotype via upregulation of the fibronectin receptor α(5)β(1).

Epac-Rap signaling reduces cellular stress and ischemia-induced kidney failure

Renal ischemia-reperfusion injury is associated with the loss of tubular epithelial cell-cell and cell-matrix interactions which contribute to renal failure. The Epac-Rap signaling pathway is a potent regulator of cell-cell and cell-matrix adhesion. The cyclic AMP analogue 8-pCPT-2'-O-Me-cAMP has been shown to selectively activate Epac, whereas the addition of an acetoxymethyl (AM) ester to 8-pCPT-2'-O-Me-cAMP enhanced in vitro cellular uptake. Here we demonstrate that pharmacological activation of Epac-Rap signaling using acetoxymethyl-8-pCPT-2'-O-Me-cAMP preserves cell adhesions during hypoxia in vitro, maintaining the barrier function of the epithelial monolayer. Intrarenal administration in vivo of 8-pCPT-2'-O-Me-cAMP also reduced renal failure in a mouse model for ischemia-reperfusion injury. This was accompanied by decreased expression of the tubular cell stress marker clusterin-α, and lateral expression of β-catenin after ischemia indicative of sustained tubular barrier function. Our study emphasizes the undervalued importance of maintaining tubular epithelial cell adhesion in renal ischemia and demonstrates the potential of pharmacological modulation of cell adhesion as a new therapeutic strategy to reduce the extent of injury in kidney disease and transplantation.

The influence of bisphosphonates on human osteoblast migration and integrin aVb3/tenascin C gene expression in vitro

Background

Bisphosphonates are therapeutics of bone diseases, such as Paget's disease, multiple myeloma or osteoclastic metastases. As a severe side effect the bisphosphonate induced osteonecrosis of the jaw (BONJ) often requires surgical treatment and is accompanied with a disturbed wound healing.

Therefore, the influence on adhesion and migration of human osteoblasts (hOB) after bisphosphonate therapy has been investigated by morphologic as well as gene expression methods.

Methods

By a scratch wound experiment, which measures the reduction of defined cell layer gap, the morphology and migration ability of hOB was evaluated. A test group of hOB, which was stimulated by zoledronate 5 × 10^-5M, and a control group of unstimulated hOB were applied. Furthermore the gene expression of integrin aVb3 and tenascin C was quantified by Real-Time rtPCR at 5data points over an experimental period of 14 days. The bisphosphonates zoledronate, ibandronate and clodronate have been compared with an unstimulated hOB control.

Results

After initially identical migration and adhesion characteristics, zoledronate inhibited hOB migration after 50 h of stimulation. The integrinavb3 and tenascin C gene expression was effected by bisphosphonates in a cell line dependent manner with decreased, respectively inconsistent gene expression levels over time. The non-nitrogen containing bisphosphonates clodronate led to decreased gene expression levels.

Conclusion

Bisphosphonates seem to inhibit hOB adhesion and migration. The integrin aVb3 and tenascin C gene expression seem to be dependent on the cell line. BONJ could be enhanced by an inhibition of osteoblast adhesion and migration. The gene expression results, however, suggest a cell line dependent effect of bisphosphonates, which could explain the interindividual differences of BONJ incidences.

Visual indicator for surfactant abundance in MS-based membrane and general proteomics applications

The existence of surfactants in proteomics samples can severely reduce enzymatic digestion efficiency, liquid chromatography (LC) separation efficiency, column lifetime, and mass spectrometry (MS) sensitivity. Although various techniques are able to remove surfactants, surfactants may occasionally be retained in samples due to variations in sample preparation method or personal skill. Evaluation of surfactant residue in a sample, however, usually requires an additional instrument and is time-consuming. In this study, a simple and rapid visual indicator for surfactant abundance (VISA) was developed. With the detection of a visible surfactant pellet in the solution, this assay was able to detect surfactant residue in aqueous solutions within 5 min. Without the need of additional equipment such as a mass spectrometer, every user can perform a quick test on their bench before sending the sample to the MS facility. The detection limit for the commonly used surfactants, Triton X-114 and SDS, was about 0.0005% and 0.0002%, respectively. The VISA was successfully applied to evaluate the efficiency of removal of surfactants in Triton X-114 extracted membrane proteins using tube-gel. With the combination of Triton X-114 extraction and tube-gel protocol, a study of spermatozoa membrane proteome identified about 252 proteins of which about 67.5% were classified as membrane proteins. The coexistence of protein and surfactant did not affect the VISA sensitivity, suggesting that this indicator is suitable for proteomics applications. The VISA also has potential for the detection of other surfactants and can be applied to other surfactant removing protocols.

A combination method of chemical with enzyme reactions for identification of membrane proteins

A simple method for effective analysis of various proteins has been developed, including membrane proteins, with LC-MS/MS, using CNBr and acetic acid cleavage in one reaction for the digestion of both the M/ and /D/ positions within the target proteins. This dual chemical reaction has been compared with traditional CNBr or an acid cleavage method using a rat kidney membrane fraction and it showed an advantage of the dual reaction with respect to a high number of peptides detected and a high protein recovery. Furthermore, when this dual chemical reaction was combined with trypsin digestion, the number of proteins surprisingly increased approximately 3.0 times more than in the cases with the trypsin digestion only. It was also 1.9 times more than in cases dealing with Tube-Gel trypsin digestion, which is one of the most efficient digestion methods. In addition, it was shown that this dual chemical reaction could be applied to an in-gel digestion. Using the combination of the chemical and enzyme reaction, 172 proteins including 95 membrane proteins were identified. This indicated that this method is one of the efficient systems in single MS/MS analysis. In particular, many membrane proteins identified in this study were detected by a new combination, but not by a traditional trypsin digestion method.

Acurhagin-C, an ECD disintegrin, inhibits integrin alphavbeta3-mediated human endothelial cell functions by inducing apoptosis via caspase-3 activation

BACKGROUND AND PURPOSE

Acurhagin, a member of versatile metalloproteinase disintegrins from Agkistrodon acutus venom, has been identified as a platelet aggregation inhibitor, previously. Here, acurhagin-C, the C-terminal Glu-Cys-Asp (ECD)-containing fragment of acurhagin, was evaluated for its biological activities and potential applications in anti-angiogenic therapy.

EXPERIMENTAL APPROACH

Human umbilical vein endothelial cells (HUVECs) were treated with acurhagin-C to assay effects on viability, apoptosis, adhesion, migration, invasion, proliferation and angiogenesis. The recognition site and signalling involved for the interactions of acurhagin-C with HUVEC were determined using flow cytometric, electrophoresis and immunoblotting analyses.

KEY RESULTS

Acurhagin-C decreased viability and induced apoptosis in HUVEC. It also dose-dependently inhibited HUVEC adhesion to immobilized extracellular matrices fibronectin, collagen I and vitronectin with respective IC(50) values of approximately 0.6, 0.3 and 0.1 microM. Acurhagin-C prevented migration and invasion of HUVEC through vitronectin- and Matrigel-coated barriers respectively. Furthermore, acurhagin-C attenuated fibroblast growth factor-2-primed angiogenesis both in vitro and in vivo, and specifically blocked the binding of anti-alphavbeta3 monoclonal antibody 23C6 to HUVEC in an ECD-dependent manner. However, purified alphavbeta3 also dose-dependently bound to immobilized acurhagin and acurhagin-C with a saturable pattern. Interference with integrin alphavbeta3-mediated functions and promotion of caspase-3 activation by acurhagin-C affected morphology of HUVEC and induced apoptosis.

CONCLUSIONS AND IMPLICATIONS

Acurhagin-C elicited endothelial anoikis via disruption of alphavbeta3/focal adhesion kinase/phosphatidylinositol 3-kinase/Akt survival cascade and subsequent initiation of the procaspase-3 apoptotic signalling pathway.

Binding of the fibronectin-mimetic peptide, PR_b, to alpha5beta1 on pig islet cells increases fibronectin production and facilitates internalization of PR_b functionalized liposomes

Islet transplantation is a promising treatment for type 1 diabetes. Recent studies have demonstrated that human islet allografts can restore insulin independence to patients with this disease. As islet isolation and immunotherapeutic techniques improve, the demand for this cell-based therapy will dictate the need for other sources of islets. Pig islets could provide an unlimited supply for xenotransplantation and have shown promise as an alternative to human islet allografts. However, stresses imposed during islet isolation and transplantation decrease islet viability, leading to loss of graft function. In this study, we investigated the ability of a fibronectin-mimetic peptide, PR_b, which specifically binds to the alpha(5)beta(1) integrin, to re-establish lost extracellular matrix (ECM) around isolated pig islets and increase internalization of liposomes. Confocal microscopy and Western blotting were used to show the presence of the integrin alpha(5)beta(1) on the pig islets on day 0 (day of isolation) as well as on different days of islet culture. Islets cultured in medium supplemented with free PR_b for 48 h were found to have increased levels of ECM fibronectin secretion compared to islets in normal culture conditions. Using confocal microscopy and flow cytometry, we found that PR_b peptide-amphiphile functionalized liposomes delivered to the pig islets internalized into the cells in a PR_b concentration dependent manner and nonfunctionalized liposomes showed minimal internalization. These studies proved that the fibronectin-mimetic peptide, PR_b, is an appropriate peptide bullet for applications involving alpha(5)beta(1) expressing pig islet cells. Fibronectin production stimulated through alpha(5)beta(1) PR_b binding may decrease apoptosis and therefore increase islet viability in culture. In addition, PR_b peptide-amphiphile functionalized liposomes may be used for targeted delivery of different agents to pig islet cells.