Beta1 Integrin Research Articles

Filamin's Force Sensing Mechanism Revealed by Optical Tweezers

Cell adhesion, spreading and migration, as it occurs during embryogenesis or wound healing and hemostasis, involve a complex interplay between the extracellular matrix, transmembrane adhesion receptors and the cytoskeleton. A prominent role plays human filamin A, since it is a widely expressed actin cross-linker which additionally binds a multitude of transmembrane receptors such as beta integrins or the von Willebrand Factor receptor GPIbα.Although it has been shown that beta integrins or GPIbα bind to the Ig-like domain 21 of filamin A, the molecular-level mechanism for filamin binding, especially its regulation, is still unclear. Filamin can auto-inhibit the interaction by hiding the binding site through intra-molecular interactions and it has been suggested that the binding site can be exposed by a force-induced conformational change.To address the question whether filamin's binding site in domain 21 was activated by force, we adapted a highly sensitive optical tweezers setup to pull at single domain pairs of human filamin A containing the receptor binding site and the auto-inhibiting region. We were able to apply and detect low forces in the physiological relevant regime around 3 pN and monitor the conformational change by measuring the length increase of the protein on a sub-millisecond timescale. This allowed us to distinguish in real-time between the inhibited closed conformation and the active open one. Additionally, we were able to detect the binding of different ligands added in solution and how the applied force increased the binding rate. Therefore, filamin A can be regarded as a force sensor.

Role of Rho GTPases in Human Trophoblast Migration Induced by IGFBP11

Insulin-like growth factor binding protein 1 (IGFBP1), the main secretory product of the decidualized endometrium of a pregnant woman, has previously been shown to interact with the alpha(5)beta(1) integrin of extravillous trophoblast (EVT) cell surface to stimulate its migration in an IGF-independent manner. This migration stimulation has also been shown to require activation of extracellular signal regulated kinases 1 and 2 (ERK1/2; mitogen-activated protein kinase [MAPK] 3/1]) and focal adhesion kinase. The present study examined the roles of Rho GTPases RHOA, RHOC, RAC1, and CDC42 as well as RHO kinases ROCK1 and ROCK2 in IGFBP1-mediated migration of an immortalized EVT cell line HTR-8/SVneo. A nonselective RHO kinase inhibitor, Y27632, as well as siRNAs selective for ROCK1 and ROCK2 decreased the migration of these cells in a Transwell migration assay, and this inhibition could not be restored by IGFBP1. Clostridium difficile toxin B, which inhibits all the Rho GTPases, RAC inhibitor NSC23766, RAC1 siRNA, and CDC42 siRNA, decreased their basal migration, but none of these inhibitions except CDC42 siRNA-induced inhibition could be restored by IGFBP1. Clostridium botulinum C3 exoenzyme that inhibits RHOA, RHOB, and RHOC inhibited basal migration but not IGFBP1-induced migration. IGFBP1-induced activation of ERK1/2 (MAPK3/1), which did not require RHO proteins, might function as an alternate pathway for RHO action. However, selective siRNA-mediated downregulation of RHOA inhibited basal, but not IGFBP1-mediated, migration, whereas that of RHOC inhibited both basal and IGFBP1-mediated migration of these EVT cells. Therefore, RHO kinase, RHOC, and RAC1 are essential, but RHOA and CDC42 are not essential, for IGFBP1-induced EVT migration.

A gene expression signature of emphysema-related lung destruction and its reversal by the tripeptide GHK

BackgroundChronic obstructive pulmonary disease (COPD) is a heterogeneous disease consisting of emphysema, small airway obstruction, and/or chronic bronchitis that results in significant loss of lung function over time.MethodsIn order to gain insights into the molecular pathways underlying progression of emphysema and explore computational strategies for identifying COPD therapeutics, we profiled gene expression in lung tissue samples obtained from regions within the same lung with varying amounts of emphysematous destruction from smokers with COPD (8 regions × 8 lungs = 64 samples). Regional emphysema severity was quantified in each tissue sample using the mean linear intercept (Lm) between alveolar walls from micro-CT scans.ResultsWe identified 127 genes whose expression levels were significantly associated with regional emphysema severity while controlling for gene expression differences between individuals. Genes increasing in expression with increasing emphysematous destruction included those involved in inflammation, such as the B-cell receptor signaling pathway, while genes decreasing in expression were enriched in tissue repair processes, including the transforming growth factor beta (TGFβ) pathway, actin organization, and integrin signaling. We found concordant differential expression of these emphysema severity-associated genes in four cross-sectional studies of COPD. Using the Connectivity Map, we identified GHK as a compound that can reverse the gene-expression signature associated with emphysematous destruction and induce expression patterns consistent with TGFβ pathway activation. Treatment of human fibroblasts with GHK recapitulated TGFβ-induced gene-expression patterns, led to the organization of the actin cytoskeleton, and elevated the expression of integrin β1. Furthermore, addition of GHK or TGFβ restored collagen I contraction and remodeling by fibroblasts derived from COPD lungs compared to fibroblasts from former smokers without COPD.ConclusionsThese results demonstrate that gene-expression changes associated with regional emphysema severity within an individual's lung can provide insights into emphysema pathogenesis and identify novel therapeutic opportunities for this deadly disease. They also suggest the need for additional studies to examine the mechanisms by which TGFβ and GHK each reverse the gene-expression signature of emphysematous destruction and the effects of this reversal on disease progression.

Allosteric Modulation of Beta1 Integrin Function Induces Lung Tissue Repair

The cellular cytoskeleton, adhesion receptors, extracellular matrix composition, and their spatial distribution are together fundamental in a cell's balanced mechanical sensing of its environment. We show that, in lung injury, extracellular matrix-integrin interactions are altered and this leads to signalling alteration and mechanical missensing. The missensing, secondary to matrix alteration and cell surface receptor alterations, leads to increased cellular stiffness, injury, and death. We have identified a monoclonal antibody against β1 integrin which caused matrix remodelling and enhancement of cell survival. The antibody acts as an allosteric dual agonist/antagonist modulator of β1 integrin. Intriguingly, this antibody reversed both functional and structural tissue injury in an animal model of degenerative disease in lung.

Association of Alpha-2 Beta-1 Integrin Polymorphism with Retinopathy in Diabetic Patients

Aim: Diabetes mellitus (DM) is a health concern because it leads to complications such as retinopathy and nephropathy. Pakistan has 6.9 million DM affected people that will be doubled by 2025. A study was designed to determine the role of genetics in diabetic retinopathy in Pakistani type 2 diabetes mellitus (T2DM) patients. Material and methods: It was a cross-sectional case-control study that included 236 subjects, divided into Group I (54 volunteers without diabetes), Group II (30 T2DM patients without retinopathy) and Group III (152 T2DM patients with retinopathy). A BglII polymorphism of α2β1 integrin gene was genotyped in all these individuals by using RFLP method. Results: The frequency of BglII polymorphism (++ and +-) genotypes was found significantly different between group I and group III individuals. Conclusion: BglII (+/+, +/-) genotypes, gender of subject, age at the onset of diabetes, and duration of diabetes is associated with development of diabetic retinopathy in Pakistani T2DM patients.

P2-01-16: Dissecting the Cellular Mechanism of Induction and Sustenance of Dormancy by Rho GTPases in Breast Cancer.

Abstract Tumor dormancy has been a very real problem in breast cancer survivors where recurrences are common and usually fatal. Molecular mechanisms involved in this process are often poorly understood and are a hot spotin breast cancer research today. We have found that Rho GTPases, specifically RhoC, is hyperactivated in low metastatic dormant breast tumor cells while RhoA is downregulated. We also found RhoC causes phosphorylation of c-jun NH2 terminal kinase (JNK) in these cells which in turn activates the process of autophagy, a possible mode of cell survival in dormant tumor cells. Modulating RhoC affected phosphorylation of JNK. Also, abrogating JNK by a pharmacological inhibitor SP600125 inhibited expression of the autophagy marker LC3B-II. Autophagy genes like Atg 5 and Atg 12 were expressed along with the autophagy marker LC3B-II. On inhibiting autophagy by a specific inhibitor 3-Methyladenine (3-MA), cells did not readily undergo apoptosis but on stressing them doubly with LY294002, an inhibitor of Class I PI3K, along with 3-MA (inhibitor of Class III PI3K), significant number of dormant cells underwent apoptosis as observed by TUNEL staining. We also found that p190RhoGAP was activated in these dormant cells which may lead to the observed downregulation of RhoA activation levels. Involvement of beta-1 integrin along with c-src in activation of RhoC was observed in these dormant cells. We are in the process of further elucidating these signal transduction processes that might be involved in cellular dormancy of breast cancer. A better understanding of some of the cellular mechanisms of induction and sustenance of dormancy may aid in formulating therapies for annihilating these dormant tumor cells thus preventing the often fatal relapses in breast cancer survivors. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-01-16.

Affinity of the alpha4–beta1 integrin-targeting peptide LLP2A to canine lymphoma

Lymphoma is an important disease in dogs and people, with similar biological characteristics. We tested the binding affinity of a peptidomimetic LLP2A, previously shown to bind the alpha4–beta1 integrin on human lymphoma cell lines, to lymphocytes of dogs with spontaneously occurring lymphoma. Fine needle aspirates of lymph nodes from 32 dogs with B-cell lymphoma and 7 dogs with T-cell lymphoma were evaluated using flow cytometry. For B cells, the lowest MFI levels were in unlabeled, non-neoplastic lymphocytes. The highest median fluorescent intensity (MFI) levels occurred in LLP2A-labeled lymphoma cells from dogs that had not received chemotherapy followed by labeled lymphoma cells from dogs that had received chemotherapy. The fluorescence profile of the T-cell samples was similar although many of the differences were not statistically significant, likely due to low sample number. Specifically, LLP2A-labeled T-cell lymphoma cells had a significantly higher MFI compared to unlabeled non-neoplastic lymphocytes. LLP2A affinity was not significantly different in unlabeled and labeled T-cell lymphoma cells, and labeled non-neoplastic lymphocytes. For both B and T cells, labeling with LLP2A tended to increase MFI in both normal and lymphoma cells. Lymphoma cells had higher mean MFI levels than non-neoplastic lymphocytes, and chemotherapy acted to decrease MFI. In summary, these data demonstrate that LLP2A has affinity to canine lymphoma cells and indicates expression of the alpha4–beta1 integrin on these cells. In fact, LLP2A preferentially binds neoplastic B-cells, suggesting that this small molecule may be of use in cross-species clinical trials of targeted therapeutics.

Pyk2 Mediates Enhanced STAT3 Phosphorylation Following Collaborative Signaling Between gp130 and beta1 Integrins in Adhered Myeloma and B Cells

Abstract 2895Multiple myeloma is the second most common hematologic malignancy and remains incurable due to the eventual development of drug resistance. Therapy resistance has been linked to both acquired genetic changes as well as the dynamic influences of soluble and physical factors present in the microenvironment. We and others have shown that adhesion of tumor cells to the extracellular matrix component fibronectin (FN) via integrins leads to cell cycle arrest and protection from chemotherapy or Cell Adhesion-Mediated Drug Resistance (CAM-DR). The pleiotropic cytokine IL-6 has also been shown to mediate drug resistance in both solid and hematopoietic tumors [1]. To date, the influence of these two effectors on drug resistance has been studied separately; however, within the context of the bone marrow myeloma cells are influenced by both soluble and physical effectors of the microenvironment simultaneously. Using a reductionist model of the multivariant microenvironment, we recently demonstrated that unique collaborative signaling between FN-adhered cells and IL-6 leads to increased proliferation of protected tumor cells and a more malignant phenotype[2]. Our results demonstrate the FN-adhesion mediated cell-cycle arrest of myeloma cells was reversed following stimulation of adhered cells with IL-6. This phenotype was associated with a novel amplification of IL-6-induced STAT3 activation in adhered cells [2]. To further characterized the molecular events mediating this unique event we focused on the focal adhesion kinase, Proline-rich tYrosine Kinase 2 (Pyk2/FAK2). Pyk2 is a downstream intermediate of integrin signaling and has been demonstrated to amplify EGFR and cSrc-induced STAT3 activation. As such, we hypothesized that Pyk2 may be an important modulator of the enhanced STAT3 activation following multivariant signaling between beta1 integrins and gp130[3]. Our results link this amplification to Pyk2 in myeloma and murine pro-B cell lines. Western blot analysis demonstrated that Pyk2 autophophorylation on tyrosine 402 is induced following myeloma cell adhesion to FN correlating with the amplification of IL-6-induced STAT3, JAK1, and gp130 phosphorylation in both myeloma and pro B cell line models. Targeting Pyk2 with RNA interference attenuated the adhesion-associated amplification of STAT3 signaling as well as JAK1 and gp130 phosphorylation, but did not influence the limited STAT3 activation in cells grown in suspension. Further we demonstrated that Pyk2 kinase activity was similarly required for the activation of JAK1/STAT3 signaling under collaborative conditions, but not by IL-6 alone. Consistent with previous results ERK1/2 and Akt signaling were not affected by Pyk2 siRNA or kinase activity. Importantly, Pyk2 siRNA did not inhibit myeloma cell adhesion (n=4, p-value >0.05). Our previous results demonstrated that that the enhanced STAT3 signaling involved a FN-adhesion specific binding of unphosphorylated STAT3 with gp130 (independent of IL-6 stimulation). To determine if Pyk2 was similarly recruited to gp130 under co-stimulatory conditions we have initially used confocal microscopy. Confocal imaging with antisera to Pyk2 and gp130 demonstrated colocalization of the two effectors upon adhesion of myeloma cell to FN, but not in those grown in suspension. These data demonstrate that within the context of multivariant stimulation (IL-6 and FN-adhesion) a unique Pyk2-mediated JAK1/STAT3 signaling cascade is associated with unique biologic sequelae. We are currently exploring the biological sequelae of Pyk2-mediated collaborative signaling between integrins and IL-6. Key endpoints currently under investigation include proliferation and drug-response. These findings are significant because they suggests strategies targeting Pyk2 could be used to block cooperative signaling between integrins and IL-6, and inhibit the proliferation and/or therapy resistance conferred to tumor cells by the multivariant bone marrow niche. Disclosures:No relevant conflicts of interest to declare.

Protein Disulfide Isomerase Plays An Important Role in Beta2 Integrin-Mediated Neutrophil Recruitment During Vascular Inflammation

Abstract 17Cell surface protein disulfide isomerase (PDI), a prototypic thiol isomerase, plays an important role in regulating integrin-mediated cellular functions. Although surface PDI has been reported to regulate L-selectin shedding on neutrophils, its role in neutrophil recruitment during vascular inflammation has not been explored. In this paper, we present novel findings on how neutrophil PDI regulates neutrophil recruitment into the site of vascular inflammation. Using real-time microscopy with cell-impermeable inhibitors for PDI (bacitracin or function-blocking antibodies), we demonstrated that inhibition of PDI reduces adhesion of human blood neutrophils to TNF-alpha-stimulated human umbilical vein endothelial cells (HUVECs) under venous shear. There was no additive effect on neutrophil adhesion in a combination of blocking anti-PDI and anti-beta2 antibodies, suggesting that surface PDI regulates beta2 integrin-mediated neutrophil adhesion to TNF-alpha-activated HUVECs under shear. Further, bacitracin and blocking anti-PDI antibodies diminished alphaMbeta2 integrin-mediated neutrophil adhesion to intercellular adhesion molecule-1 (ICAM-1)-coated surfaces under static conditions. When PDI gene is knocked down in neutrophil-like HL60 cells by shRNA, alphaMbeta2 activation and cell adhesion to TNF-alpha-activated HUVECs under shear were significantly reduced. High resolution confocal microscopy and immunoprecipitation assay revealed that surface PDI interacts with alphaMbeta2 integrin and that such interaction was enhanced by neutrophil activation and inhibited by bacitracin, a thiol isomerase inhibitor. Exogenous PDI equivalently bound to CHO cells stably expressing alphaMbeta2 or alphaLbeta2 when those cells were treated with Mn2+, whereas PDI binding was significantly reduced when the active site CGHC residues on PDI were mutated. Using multi-channel fluorescence intravital microscopy, we demonstrated that inhibition of PDI by infusion of PDI inhibitors impairs stable adhesion of neutrophils to the TNF-alpha-inflamed cremaster muscle venule wall in living mice. These findings suggest the potentially fundamental but poorly understood role for surface PDI in the regulation of beta2 integrin function in neutrophils. Therefore, our results provide the first evidence that inhibition of PDI may be a therapeutic target for the neutrophil-mediated vascular inflammation. Disclosures:No relevant conflicts of interest to declare.

An in vitro correlation of metastatic capacity, substrate rigidity, and ECM composition

The process of metastasis requires a metastatic cancer cell to invade a variety of micro-environments of variable stiffnesses. Unlike metastatic cells, normal cell function and viability is dependent on the stiffness of the environment and used as a cue to maintain cell health and proper tissue organization. In this study we have asked if metastatic cells can ignore the parameter of stiffness and if this ability is gradually acquired and if so, through what mechanism. Using a panel of mouse mammary tumor cells derived from the same parental tumor, but possessing different metastatic abilities, we cultured the cells on hard and soft substrates conjugated with collagen or fibronectin. Normal and non-metastatic tumor cells responded to changes in stiffness on fibronectin, but not collagen. However, the more metastatic cells ignored the change in stiffness on fibronectin-coated substrates. This lack of response on fibronectin correlated with a change in the expression level of the α3 integrin subunit, activation of the β1 subunit, and phosphorylation of FAKpY397. We conclude that through fibronectin, changes in the activation and tethering of the beta-1 integrin provides a mechanism for metastatic cells to disregard changes in compliance to survive and navigate in environments of different stiffness.

Monophosphorylated (747pY) beta3 integrin cytoplasmic tail under membrane mimetic conditions

monophosphorylated (747pY) beta3 integrin cytoplasmic tail under membrane mimetic conditions

Matrix Metalloproteinase-8 Is Involved in Dermal Nerve Growth: Implications for Possible Application to Pruritus from In Vitro Models

Cutaneous nerve density is related to abnormal itch perception in dermatoses, such as atopic dermatitis and xerosis. However, the mechanisms underlying the elongation of dermal nerve fibers within the interstitial collagen (CoL) matrix are poorly understood. In this study, a culture system of rat dorsal root ganglion neurons consisting of type I CoL and a Boyden chamber containing a nerve growth factor (NGF) concentration gradient was used. Nerve fibers penetrating into type I CoL gel were observed in the presence of the NGF concentration gradient. Levels of matrix metalloproteinase-8 (MMP-8) mRNA and protein were increased in the cultured neurons and the conditioned medium, respectively. The nerve fiber penetration was dose dependently inhibited by MMP-8 blockers. Moreover, MMP-8 immunoreactivity was partially localized at growth cones in NGF-responsive nerve fibers. Semaphorin 3A stimulation also showed the opposite effects on these NGF-dependent events. Intriguingly, MMP-8 expression was upregulated by type I and III CoLs, which are substrates for this enzyme. These results suggested that MMP-8 is involved in sensory nerve growth within the interstitial CoL matrix through modulation by the axonal guidance molecules and/or extracellular matrix components. These findings provide insight into the development of pruritus involving skin nerve density.

Phenotyping of chondrocytes from human osteoarthritic cartilage: chondrocyte expression of beta integrins and correlation with anatomic injury

Chondrocyte-ECM (extracellular matrix) interactions are believed to play a pivotal role in the development and metabolic homeostasis of articular cartilage. Cell surface adhesion molecules have been reported to modulate chondrocyte binding to ECM (collagen, fibronectin, laminin) and they also act as transducers of critical signals in many biological processes such as growth, differentiation, migration and matrix synthesis. Recently, it has been shown that normal human articular chondrocytes strongly express beta1 integrins, which are constituted by a common chain (beta1) and a variable alphachain, but the behaviour of these molecules in human osteoarthritic cartilage has not been extensively investigated. We studied the expression of beta integrins (beta1-5, alpha1-6, av chains), LFA-1, ICAM-1 and CD44, on freshly isolated chondrocytes obtained from 10 osteoarthritic patients undergoing surgical knee replacement. Chondrocytes were isolated by enzymatic digestion from three zones of each articular cartilage with a differing degree of macroscopic and microscopic damage. Integrin expression and cell cycle analysis were carried out by flowcytometry. Chondrocytes from costal cartilages of 5 human foetuses were also studied. Chondrocytes from osteoarthritic cartilage expressed high levels of beta1 integrin and, at different percentages, all the alphachains. The alphachain most frequently expressed was alpha1, foilowed by alpha3, alpha5, alpha2, alphav. Integrin expression decreased from the least to the most damaged zone of articular cartilage and cell cycle analysis showed that proliferating chondrocytes (S phase) were prevalent on the latter zone. beta2, beta3, beta2, beta5, CD44, LFA-1/ICAM-1 complex were very low expressed. Fetal chondrocytes strongly expressed beta1 and beta5 chains. These data provide evidence to show that integrin expression on human chondrocytes changes in osteoarthritis and suggest that perturbations of chondrocyte-ECM signalling occur in the development of the disease. The different pattern of expression of beta1 and beta5 chains on adult and fetal chondrocytes leads to speculate that integrins play a key role in control of cartilage morphogenesis and differentiation.

Effects of altered restraints in beta1 integrin on the force-regulated interaction between the glycosylated I-like domain of beta1 integrin and fibronectin III9-10: a steered molecular dynamic study.

Cytoskeletal restraints affect force-regulated integrin function in cell adhesion. However, the structural and molecular basis underlying the effect of cytoskeletal restraints on beta1 integrin binding to fibronectin is still largely unknown. In this study, we used steered molecular dynamics simulations to investigate the changes in glycosylated beta1 integrin-fibronectin binding and in conformation and structure of the glycosylated beta1 I-like domain-FN-III9-10 complex caused by altered restraints applied to beta1 I-like domain. The results revealed that imposition of the increased constraints on beta1 integrin increased resistance to force-induced dissociation of the beta1 I-like domain-fibronectin complex. Specifically, the increased constraints enhanced resistance to relative conformational changes in the RGD-synergy site in fibronectin, increased the conformational stability of fibronectin, and prevented losses in hydrogen bond occupancy of each beta-strand pair in FN-III10 resulting from external force. The increased constraints also resulted in an increase in correlated motion between residues in the beta1 I-like domain, which may directly affect the interaction of beta1 integrin with fibronectin. Results from this study provide molecular and structural insights into the effects of altered restraints in beta1 integrin on the interaction between glycosylated beta1 Integrin and fibronectin and its induced cell adhesion.

The effect of ovarian stimulation on expression level of alpha(v), beta(3) integrins in mouse blastocyst and endometrium

The effect of ovarian stimulation on expression level of alpha(v), beta(3) integrins in mouse blastocyst and endometrium

Beta-1 integrin is an upstream regulator of Eph-B4-mediated vein graft adaptation

Beta-1 integrin is an upstream regulator of Eph-B4-mediated vein graft adaptation

Hydrogen sulfide protects against ischemia-reperfusion injury by decreasing neutrophil-mediated tissue damage

METHODS: Human neutrophils were incubated in 10uM HS or saline and labeled with antibodies to PSGL-1, LFA-1, Mac1alpha, L-selectin and beta-2 integrin CBRM1/5 epitope prior to flow cytometry analysis. Additional neutrophils were activated with IL-8, fMLP, or TNFalpha, or treated with 30uM TAPI-0 (an inhibitor of the enzyme responsible for L-selectin cleavage) prior to HS/saline treatment, labeling, and flow cytometry. Nine C57BL/6 mice were administered an intravenous dose of 20uM HS or saline. Mice then underwent 3h of unilateral tourniquetinduced hindlimb ischemia, followed by 3h of reperfusion. The bilateral gastrocnemius muscles were harvested and stained with H&E. Neutrophil infiltration was quantified.

Comparative studies of vertebrate Beta integrin genes and proteins: ancient genes in vertebrate evolution.

Intregins are heterodimeric α- and β-subunit containing membrane receptor proteins which serve various cell adhesion roles in tissue repair, hemostasis, immune response, embryogenesis and metastasis. At least 18 α- (ITA or ITGA) and 8 β-integrin subunits (ITB or ITGB) are encoded on mammalian genomes. Comparative ITB amino acid sequences and protein structures and ITB gene locations were examined using data from several vertebrate genome projects. Vertebrate ITB genes usually contained 13–16 coding exons and encoded protein subunits with ∼800 amino acids, whereas vertebrate ITB4 genes contained 36-39 coding exons and encoded larger proteins with ∼1800 amino acids. The ITB sequences exhibited several conserved domains including signal peptide, extracellular β-integrin, β-tail domain and integrin β-cytoplasmic domains. Sequence alignments of the integrin β-cytoplasmic domains revealed highly conserved regions possibly for performing essential functions and its maintenance during vertebrate evolution. With the exception of the human ITB8 sequence, the other ITB sequences shared a predicted 19 residue α-helix for this region. Potential sites for regulating human ITB gene expression were identified which included CpG islands, transcription factor binding sites and microRNA binding sites within the 3′-UTR of human ITB genes. Phylogenetic analyses examined the relationships of vertebrate beta-integrin genes which were consistent with four major groups: 1: ITB1, ITB2, ITB7; 2: ITB3, ITB5, ITB6; 3: ITB4; and 4: ITB8 and a common evolutionary origin from an ancestral gene, prior to the appearance of fish during vertebrate evolution. The phylogenetic analyses revealed that ITB4 is the most likely primordial form of the vertebrate β integrin subunit encoding genes, that is the only β subunit expressed as a constituent of the sole integrin receptor ‘α6β4’ in the hemidesmosomes of unicellular organisms.

Rab7 and actin cytoskeleton participate during mobilization of β1EHFNR in fibronectin‐stimulated Entamoeba histolyticatrophozoites

In vitro interaction of Entamoeba histolytica trophozoites with fibronectin (FN) induces redistribution of the amoebic fibronectin receptor (β1EhFNR). Trafficking of beta1 integrins is important for cell adhesion and migration in higher eukaryotes and requires the participation of Rab proteins. In E. histolytica, the machinery involved in integrin trafficking is not completely known. EhRab7 is a 24.5-kDa protein whose alignment with other Rab7 proteins demonstrated that it shared significant homology with Rab7 proteins from other organisms, including humans. Using different types of microscopy (fluorescence and confocal microscopy), it was established that Rab7 and the actin cytoskeleton participated in the mobilization of β1EhFNR in FN-stimulated trophozoites. β1EhFNR and Rab7 co-localized only in vesicular structures at 5 min, and at longer time (1 h), both co-localized in both plasma membrane and in vesicular structures; at the same time, Rab7 co-localized with specific actin structures (phagocytic vacuoles). At 5 h the β1EhFNR, Rab7, and actin co-localized at the plasma membrane, and only β1EhFNR and Rab7 decorated vesicles of different sizes. Actin and Rab7 co-localized in a cap-like structure at one end of the cell. Fluorescence resonance energy transfer and electron microscopy confirmed the close interaction between β1EhFNR and Rab7. Moreover, the use of a lysosome-specific marker (LysoTracker) and a Golgi-specific marker (NBD C(6)-ceramide) allowed us to establish that, at some point within the endocytic route, β1EhFNR and Rab7 co-localized within a lysosome-type organelle, but not a Golgi-like organelle, which indicated that this integrin-like molecule was returned to the plasma membrane via exocytic or secretory vesicles.

Comparative analysis of macrophage associated vectors for use in genetic vaccine

BackgroundAntigen presentation by non professional antigen presenting cells (APC) can lead to anergy. In genetic vaccines, targeting the macrophages and APC for efficient antigen presentation might lead to balanced immune response. One such approach is to incorporate APC specific promoter in the vector to be used.MethodsThree promoters known to be active in macrophage were selected and cloned in mammalian expressing vector (pAcGFP1-N1) to reconstruct (pAcGFP-MS), (pAcGFP-EMR) and (pAcGFP-B5I) with macrosialin, EmrI and Beta-5 Integrin promoters respectively. As a positive control (pAcGFP-CMV) was used with CMV promoter and promoterless vector (pAcGFP-NIX) which served as a negative control. GFP gene was used as readout under the control of each of the promoter. The expression of GFP was analyzed on macrophage and non-macrophage cell lines using Flow cytometry and qRT-PCR with TaqMan probe chemistries.ResultsAll the promoters in question were dominant to macrophage lineage cell lines as observed by fluorescence, Western blot and quantitative RT-PCR. The activity of macrosialin was significantly higher than other macrophage promoters. CMV promoter showed 1.83 times higher activity in macrophage cell lines. The expression of GFP driven by macrosialin promoter after 24 hours was 4.40 times higher in macrophage derived cell lines in comparison with non macrophage cell lines.ConclusionsBased on this study, macrosialin promoter can be utilized for targeting macrophage dominant expression. In vivo study needs to be carried out for its utility as a vaccine candidate.