ITGAL expression in non-small-cell lung cancer tissue and its association with immune infiltrates

Background

Integrin subunit alpha L (ITGAL) encodes an integrin component of LFA-1 and is a membrane receptor molecule widely expressed on leukocytes. It plays a key role in the interaction between white blood cells and other cells. There was a significant correlation between the expression of ITGAL and the tumor microenvironment in a number of cancers. However, experimental studies targeting ITGAL and immune cell infiltration in non-small-cell lung cancer (NSCLC) and the response to immune checkpoint inhibitor therapy are lacking.

Methods

Data were obtained from The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), and Clinical Proteomic Tumor Analysis Consortium (CPTAC) databases to explore the relationship between ITGAL expression and prognosis, as well as the immune cell infiltration in patients with NSCLC. In addition, immunohistochemical staining for ITGAL and multiplex immunofluorescence (mIF) staining for ITGAL, CD20, CD68, CD4, and CD8 from tissue microarrays containing 118 tumor tissues and paired paracancerous tissues from patients with NSCLC were performed. The correlation between ITGAL expression and clinical factors, as well as the immunophenotypes of tumor-infiltrating immune cells, were also analyzed.

Results

In NSCLC tumor tissues, ITGAL was downregulated compared with matched paracancerous tissues, and low ITGAL expression was associated with a poor prognosis of NSCLC patients. Subsequently, immunohistochemistry results for tissue microarray showed that ITGAL expression was mainly elevated in tumor stroma and areas with highly infiltrated immune cells. ITGAL expression was higher in paracancerous tissues than tumor tissues. Furthermore, mIF results indicated that the patients with ITGAL-high expression tend had significantly higher CD8+ T cells, CD68+ macrophages, CD4+ T cells, and CD20+ B cells infiltration in their tumor tissues. Immunophenotypes were classified into three categories, that is deserted, excluded, and inflamed types, according to each kind of immune cell distribution in or around the cancer cell nest. MIF results showed that ITGAL expression level was correlated with the immunophenotypes. Furthermore, ITGAL expression was associated with the prognosis of NSCLC in patients with immune checkpoint inhibitor therapy and the patients with high ITGAL expression tends have better outcomes.

Conclusions

ITGAL may be used as a biomarker for assessing the immune microenvironment in patients with NSCLC.

Ramipril therapy in integrin α1-null, autosomal recessive Alport mice triples lifespan: mechanistic clues from RNA-seq analysis

The standard of care for patients with Alport syndrome (AS) is angiotensin-converting enzyme (ACE) inhibitors. In autosomal recessive Alport (ARAS) mice, ACE inhibitors double lifespan. We previously showed that deletion of Itga1 in Alport mice [double-knockout (DKO) mice] increased lifespan by 50%. This effect seemed dependent on the prevention of laminin 211-mediated podocyte injury. Here, we treated DKO mice with vehicle or ramipril starting at 4 weeks of age. Proteinuria and glomerular filtration rates were measured at 5-week intervals. Glomeruli were analyzed for laminin 211 deposition in the glomerular basement membrane (GBM) and GBM ultrastructure was analyzed using transmission electron microscopy (TEM). RNA sequencing (RNA-seq) was performed on isolated glomeruli at all time points and the results were compared with cultured podocytes overlaid (or not) with recombinant laminin 211. Glomerular filtration rate declined in ramipril-treated DKO mice between 30 and 35 weeks. Proteinuria followed these same patterns with normalization of foot process architecture in ramipril-treated DKO mice. RNA-seq revealed a decline in the expression of Foxc2, nephrin (Nphs1), and podocin (Nphs2) mRNAs, which was delayed in the ramipril-treated DKO mice. GBM accumulation of laminin 211 was delayed in ramipril-treated DKO mice, likely due to a role for α1β1 integrin in CDC42 activation in Alport mesangial cells, which is required for mesangial filopodial invasion of the subendothelial spaces of the glomerular capillary loops. Ramipril synergized with Itga1 knockout, tripling lifespan compared with untreated ARAS mice. © 2023 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Collagen VI deposition mediates stromal T cell trapping through inhibition of T cell motility in the prostate tumor microenvironment

The tumor extracellular matrix (ECM) is a barrier to anti-tumor immunity in solid tumors by disrupting T cell-tumor cell interaction underlying the need for elucidating mechanisms by which specific ECM proteins impact T cell motility and activity within the desmoplastic stroma of solid tumors. Here, we show that Collagen VI (Col VI) deposition correlates with stromal T cell density in human prostate cancer specimens. Furthermore, motility of CD4+ T cells is completely ablated on purified Col VI surfaces when compared with Fibronectin and Collagen I. Importantly, T cells adhered to Col VI surfaces displayed reduced cell spreading and fibrillar actin, indicating a reduction in traction force generation accompanied by a decrease in integrin β1 clustering. We found that CD4+ T cells largely lack expression of integrin α1 in the prostate tumor microenvironment and that blockade of α1β1 integrin heterodimers inhibited CD8+ T cell motility on prostate fibroblast-derived matrix, while re-expression of ITGA1 improved motility. Taken together, we show that the Col VI-rich microenvironment in prostate cancer reduces the motility of CD4+ T cells lacking integrin α1, leading to their accumulation in the stroma, thus putatively inhibiting anti-tumor T cell responses.

Accumulation of tissue-resident natural killer cells, innate lymphoid cells, and CD8+ T cells towards the center of human lung tumors

Lung cancer is a leading cause of cancer-related death worldwide. Despite recent advances in tissue immunology, little is known about the spatial distribution of tissue-resident lymphocyte subsets in lung tumors. Using high-parameter flow cytometry, we identified an accumulation of tissue-resident lymphocytes including tissue-resident NK (trNK) cells and CD8+ tissue-resident memory T (TRM) cells toward the center of human non-small cell lung carcinomas (NSCLC). Chemokine receptor expression patterns indicated different modes of tumor-infiltration and/or residency between trNK cells and CD8+ TRM cells. In contrast to CD8+ TRM cells, trNK cells and ILCs generally expressed low levels of immune checkpoint receptors independent of location in the tumor. Additionally, granzyme expression in trNK cells and CD8+ TRM cells was highest in the tumor center, and intratumoral CD49a+CD16- NK cells were functional and responded stronger to target cell stimulation than their CD49a- counterparts, indicating functional relevance of trNK cells in lung tumors. In summary, the present spatial mapping of lymphocyte subsets in human NSCLC provides novel insights into the composition and functionality of tissue-resident immune cells, suggesting a role for trNK cells and CD8+ TRM cells in lung tumors and their potential relevance for future therapeutic approaches.

Obacunone inhibits RANKL/M-CSF-mediated osteoclastogenesis by suppressing integrin- FAK-Src signaling

Disrupted osteoblastogenesis or aberrant activation of osteoclastogenesis usually results in the break of bone homeostasis thus causing bone-associated diseases like osteoporosis. Obacunone, as a natural compound present in citrus fruits, has been demonstrated for various biological activities including anti-cancer and anti-inflammatory properties. However, the role of obacunone in regulating osteoclastogenesis has not been elucidated so far. Here, using in vitro cell models of RANKL (Receptor activator of nuclear factor-kB ligand) and M-CSF (Macrophage-colony-stimulating factor)-induced osteoclastogenesis, we showed that obacunone inhibited osteoclast differentiation in RAW264.7 cells and bone marrow macrophages (BMMs), as evidenced by obacunone dose-dependent reduction in numbers of osteoclasts and downregulated expressions of osteoclastogenesis-associated key genes. The anti-osteoclastic properties of obacunone were associated with downregulated expressions of Integrin α1 and attenuated activation of Focal adhesion kinase (FAK) and Steroid receptor coactivator (Src) signaling. Functional Integrin α1 blockade or FAK-Src inhibition suppressed RANKL/M-CSF-induced osteoclastogenesis, while Integrin α1 overexpression or FAK/Src activation partially attenuated obacunone's effects on suppressing RANKL/M-CSF-induced osteoclast differentiation. Furthermore, in vivo administration of obacunone displayed super therapeutic effects in attenuating ovariectomy-induced bone loss in mice, as indicated by decreases in serum biomarkers of bone turnover, restoring of femur fracture maximum force, and reversing of the worsened bone-related parameters in ovariectomized animals. Taken together, these findings demonstrate that obacunone has pharmacological activities to suppress osteoclast differentiation through modulating the Integrin-FAK-Src pathway, and suggest that obacunone is a therapeutic candidate for the treatment and prevention of bone diseases such as osteoporosis.

Antiviral Responses of Tissue-resident CD49a+ Lung Natural Killer Cells Are Dysregulated in Chronic Obstructive Pulmonary Disease

Rationale: Tissue-resident natural killer (trNK) cells have been identified in numerous organs, but little is known about their functional contribution to respiratory immunity, in particular during chronic lung diseases such as chronic obstructive pulmonary disease (COPD). Objectives: To investigate the phenotype and antiviral responses of trNK cells in murine cigarette smoke-induced experimental COPD and in human lung parenchyma from COPD donors. Methods: Mice were exposed to cigarette smoke for 12 weeks to induce COPD-like lung disease. Lung trNK cell phenotypes and function were analyzed by flow cytometry in both murine and human disease with and without challenge with influenza A virus. Measurements and Main Results: In the mouse lung, CD49a+CD49b+EOMES+ and CD49a+CD49b-EOMESlo NK cell populations had a distinct phenotype compared with CD49a- circulating NK cells. CD49a+ NK cells were more extensively altered earlier in disease onset than circulating NK cells, and increased proportions of CD49a+ NK cells correlated with worsening disease in both murine and human COPD. Furthermore, the presence of lung disease delayed both circulating and trNK cell functional responses to influenza infection. CD49a+ NK cells markedly increased their NKG2D, CD103, and CD69 expression in experimental COPD after influenza infection, and human CD49a+ NK cells were hyperactive to ex vivo influenza infection in COPD donors. Conclusions: Collectively, these results demonstrate that trNK cell function is altered in cigarette smoke-induced disease and suggests that smoke exposure may aberrantly prime trNK cell responsiveness to viral infection. This may contribute to excess inflammation during viral exacerbations of COPD.

LFA-1/ ICAM-1 promotes NK cell cytotoxicity associated with the pathogenesis of ocular toxoplasmosis in murine model

Ocular toxoplasmosis (OT) is one of the most common causes of posterior uveitis. However, the pathogenic mechanisms of OT have not been well elucidated. Here, we used C57BL/6 (B6) mice to establish OT by peroral infection with 20 cysts of the TgCtWh6 strain, and severe ocular damage was observed by histopathological analysis in the eyes of infected mice. RNA-sequencing results showed that infection with T. gondii increased the expression of the NK-mediated cytotoxicity gene pathway at Day 30 after ocular T. gondii infection. Both NK-cell and CD49a+ NK-cell subsets are increased in ocular tissues, and the expression levels of LFA-1 in NK cells and ICAM-1 in the OT murine model were upregulated upon infection. Furthermore, inhibition of the interaction between LFA-1 and ICAM-1 with lifitegrast, a novel small molecule integrin antagonist, inhibited the protein expression of LFA-1 and ICAM-1 in murine OT and NK cells, improved the pathology of murine OT and influenced the secretion of cytokines in the OT murine model. In conclusion, the interaction between LFA-1 and ICAM-1 plays a role in the early regulation of the CD49a+ NK-cell proportion in an OT murine model. LFA-1/ ICAM-1 may be a key molecule in the pathogenesis of OT, and may provide new insights for potential immunotherapy.

Severe COVID-19 patients display hyper-activated NK cells and NK cell-platelet aggregates

COVID-19 is characterised by a broad spectrum of clinical and pathological features. Natural killer (NK) cells play an important role in innate immune responses to viral infections. Here, we analysed the phenotype and activity of NK cells in the blood of COVID-19 patients using flow cytometry, single-cell RNA-sequencing (scRNA-seq), and a cytotoxic killing assay. In the plasma of patients, we quantified the main cytokines and chemokines. Our cohort comprises COVID-19 patients hospitalised in a low-care ward unit (WARD), patients with severe COVID-19 disease symptoms hospitalised in intensive care units (ICU), and post-COVID-19 patients, who were discharged from hospital six weeks earlier. NK cells from hospitalised COVID-19 patients displayed an activated phenotype with substantial differences between WARD and ICU patients and the timing when samples were taken post-onset of symptoms. While NK cells from COVID-19 patients at an early stage of infection showed increased expression of the cytotoxic molecules perforin and granzyme A and B, NK cells from patients at later stages of COVID-19 presented enhanced levels of IFN-γ and TNF-α which were measured ex vivo in the absence of usual in vitro stimulation. These activated NK cells were phenotyped as CD49a⁺CD69a⁺CD107a⁺ cells, and their emergence in patients correlated to the number of neutrophils, and plasma IL-15, a key cytokine in NK cell activation. Despite lower amounts of cytotoxic molecules in NK cells of patients with severe symptoms, majority of COVID-19 patients displayed a normal cytotoxic killing of Raji tumour target cells. In vitro stimulation of patients blood cells by IL-12+IL-18 revealed a defective IFN-γ production in NK cells of ICU patients only, indicative of an exhausted phenotype. ScRNA-seq revealed, predominantly in patients with severe COVID-19 disease symptoms, the emergence of an NK cell subset with a platelet gene signature that we identified by flow and imaging cytometry as aggregates of NK cells with CD42a⁺CD62P⁺ activated platelets. Post-COVID-19 patients show slow recovery of NK cell frequencies and phenotype. Our study points to substantial changes in NK cell phenotype during COVID-19 disease and forms a basis to explore the contribution of platelet-NK cell aggregates to antiviral immunity against SARS-CoV-2 and disease pathology.

T cell interaction with activated endothelial cells primes for tissue-residency

Tissue-resident memory T cells (TRM) are suspected drivers of chronic inflammation, but their induction remains unclear. Since endothelial cells (EC) are obligate interaction partners for T cells trafficking into inflamed tissues, they may play a role in TRM development. Here, we used an in vitro co-culture system of human cytokine-activated EC and FACS-sorted T cells to study the effect of EC on T(RM) cell differentiation. T cell phenotypes were assessed by flow cytometry, including proliferation measured by CellTrace Violet dilution assay. Soluble mediators were analyzed by multiplex immunoassay. Co-culture of T cells with cytokine-activated, but not resting EC induced CD69 expression without activation (CD25, Ki67) or proliferation. The dynamic of CD69 expression induced by EC was distinct from that induced by TCR triggering, with rapid induction and stable expression over 7 days. CD69 induction by activated EC was higher in memory than naive T cells, and most pronounced in CD8+ effector memory T cells. Early CD69 induction was mostly mediated by IL-15, whereas later effects were also mediated by interactions with ICAM-1 and/or VCAM-1. CD69+ T cells displayed a phenotype associated with tissue-residency, with increased CD49a, CD103, CXCR6, PD-1 and CD57 expression, and decreased CD62L and S1PR1. EC-induced CD69+ T cells were poised for high production of pro-inflammatory cytokines and showed increased expression of T-helper 1 transcription factor T-bet. Our findings demonstrate that activated EC can induce functional specialization in T cells with sustained CD69 expression, increased cytokine response and a phenotypic profile reminiscent of TRM. Interaction with activated EC during transmigration into (inflamed) tissues thus contributes to TRM-residency priming.

CD49a Identifies Polyfunctional Memory CD8 T Cell Subsets that Persist in the Lungs After Influenza Infection

CD8 T cell memory offers critical antiviral protection, even in the absence of neutralizing antibodies. The paradigm is that CD8 T cell memory within the lung tissue consists of a mix of circulating TEM cells and non-circulating TRM cells. However, based on our analysis, the heterogeneity within the tissue is much higher, identifying TCM, TEM, TRM, and a multitude of populations which do not perfectly fit these classifications. Further interrogation of the populations shows that TRM cells that express CD49a, both with and without CD103, have increased and diverse effector potential compared with CD49a negative populations. These populations function as a one-man band, displaying antiviral activity, chemokine production, release of GM-CSF, and the ability to kill specific targets in vitro with delayed kinetics compared with effector CD8 T cells. Together, this study establishes that CD49a defines multiple polyfunctional CD8 memory subsets after clearance of influenza infection, which act to eliminate virus in the absence of direct killing, recruit and mature innate immune cells, and destroy infected cells if the virus persists.

Hsa_circ_0110757 upregulates ITGA1 to facilitate temozolomide resistance in glioma by suppressing hsa-miR-1298-5p

Temozolomide (TMZ) is the internationally recognized and preferred drug for glioma chemotherapy treatment. However, TMZ resistance in glioma appears after long-term use and is an urgent problem that needs to be solved. Circular RNAs (circRNAs) are noncoding RNAs and play an important role in the pathogenesis and progression of tumors. Hsa_circ_0110757 was identified in TMZ-resistant glioma cells by high-throughput sequencing analysis and was derived from reverse splicing of myeloid cell leukemia-1 (Mcl-1) exons. The role of hsa_circ_0110757 in TMZ-resistant glioma was evaluated both in vitro and in vivo. It was found that hsa_circ_0110757 and ITGA1 are more highly expressed in TMZ-resistant glioma than in TMZ-sensitive glioma. The overexpression of hsa_circ_0110757 in glioma patients treated with TMZ was obviously associated with tumor invasion. This study indicates that hsa_circ_0110757 inhibits glioma cell apoptosis by sponging hsa-miR-1298-5p to promote ITGA1 expression. Thus, hsa_circ_0110757/hsa-miR-1298-5p/ITGA could be a potential therapeutic target for reversing the resistance of glioma to TMZ.

A discrete subset of epigenetically primed human NK cells mediates antigen-specific immune responses

Adaptive features of natural killer (NK) cells have been reported in various species with different underlying mechanisms. It is unclear, however, which NK cell populations are capable of mounting antigen-specific recall responses and how such functions are regulated at the molecular level. Here, we identify and characterize a discrete population of CD49a+CD16- NK cells in the human liver that displays increased epigenetic potential to elicit memory responses and has the functional properties to exert antigen-specific immunity in the skin as an effector site. Integrated chromatin-based epigenetic and transcriptomic profiling revealed unique characteristics of hepatic CD49a+CD16- NK cells when compared with conventional CD49a-CD16+ NK cells, thereby defining active genomic regions and molecules underpinning distinct NK cell reactivity. In contrast to conventional NK cells, our results suggest that adaptive CD49a+CD16- NK cells are able to bypass the KIR receptor-ligand system upon antigen-specific stimulation. Furthermore, these cells were highly migratory toward chemokine gradients expressed in epicutaneous patch test lesions as an effector site of adaptive immune responses in the skin. These results define pathways operative in human antigen-specific adaptive NK cells and provide a roadmap for harnessing this NK cell subset for specific therapeutic or prophylactic vaccine strategies.

Scattered DUSP28 is a novel biomarker responsible for aggravating malignancy via the autocrine and paracrine signaling in metastatic pancreatic cancer

Pancreatic cancer remains one of the most dangerous cancers with a grave prognosis. We have reported that dual specificity phosphatise 28 (DUSP28) could be secreted in pancreatic cancer cells. However, its biological function is poorly understood. Here, we distinguish the function of scattered DUSP28 in human pancreatic cancer. DUSP28 was specifically secreted to cultured medium in metastatic pancreatic cancer cells. Treatment with recombinant DUSP28 significantly increased the migration, invasion, and viability of metastatic pancreatic cancer cells through the activation of CREB, AKT, and ERK1/2 signaling pathways. In addition, administration of recombinant DUSP28 elicited pro-angiogenic effects in human umbilical vein endothelial cells. Injection of recombinant DUSP28 also produced tumor growth in vivo. Of interest, DUSP28 formed an autocrine loop with integrin α1 (ITGα1) by transcriptional regulation and recombinant DUSP28 acted as an oncogenic reagent through the interaction with ITGα1. Notably, scattered DUSP28 could be detected in whole blood samples of pancreatic cancer patients by accessible immunoassay. These results provide the basis for DUSP28 as a promising therapeutic target and a biomarker for metastatic pancreatic cancer.

Influence of collagen-based integrin α1 and α2 mediated signaling on human mesenchymal stem cell osteogenesis in three dimensional contexts

Collagen I interactions with integrins α1 and α2 are known to support human mesenchymal stem cell (hMSC) osteogenesis. Nonetheless, elucidating the relative impact of specific integrin interactions has proven challenging, in part due to the complexity of native collagen. In the present work, we employed two collagen-mimetic proteins-Scl2-2 and Scl2-3- to compare the osteogenic effects of integrin α1 versus α2 signaling. Scl2-2 and Scl2-3 were both derived from Scl2-1, a triple helical protein lacking known cell adhesion, cytokine binding, and matrix metalloproteinase sites. However, Scl2-2 and Scl2-3 were each engineered to display distinct collagen-based cell adhesion motifs: GFPGER (binding integrins α1 and α2 ) or GFPGEN (binding only integrin α1 ), respectively. hMSCs were cultured within poly(ethylene glycol) (PEG) hydrogels containing either Scl2-2 or Scl2-3 for 2 weeks. PEG-Scl2-2 gels were associated with increased hMSC osterix expression, osteopontin production, and calcium deposition relative to PEG-Scl2-3 gels. These data indicate that integrin α2 signaling may have an increased osteogenic effect relative to integrin α1 . Since p38 is activated by integrin α2 but not by integrin α1 , hMSCs were further cultured in PEG-Scl2-2 hydrogels in the presence of a p38 inhibitor. Results suggest that p38 activity may play a key role in collagen-supported hMSC osteogenesis. This knowledge can be used toward the rational design of scaffolds which intrinsically promote hMSC osteogenesis. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2594-2604, 2018.

Murine liver-resident group 1 innate lymphoid cells regulate optimal priming of anti-viral CD8+ T cells

The liver contains 2 transcriptionally distinct group 1 ILC subsets: CD49a+ ILC1s and CD49b+ NK cells. However, little is known about how group 1 ILCs contribute to hepatic immune responses. Therefore, we characterized murine liver-resident group 1 ILCs and found that CD49a+ ILC1s express high levels of the inhibitory receptor NKG2A and localize near DCs in perivascular spaces surrounding the portal triads. Upon hepatic viral infection, NKG2A signaling in group 1 ILCs, especially in CD49a+ ILC1s, inhibits CXCL9 expression required for robust accumulation of IFN-γ+CD49b+ NK cells. As a consequence, NKG2A-/- mice showed increased numbers of IFN-γ-producing NK cells that preferentially activate liver CD103+ DCs, leading to the sustained proliferation of adoptively transferred, virus-specific CD8+ T cells. Collectively, these data suggest that group 1 ILCs play a role in maintaining the liver as a tolerogenic site by limiting the recruitment of peripheral NK cells during the early phase of viral infection. Furthermore, our findings implicate that the inhibition of NKG2A signaling on group 1 ILCs may be a novel vaccine strategy to induce robust CD8+ T cell responses against persistent liver pathogens.

Influence of extracellular matrix components on the expression of integrins and regeneration of adult retinal ganglion cells

PURPOSE

Retinal ganglion cells (RGCs) are exposed to injury in a variety of optic nerve diseases including glaucoma. However, not all cells respond in the same way to damage and the capacity of individual RGCs to survive or regenerate is variable. In order to elucidate factors that may be important for RGC survival and regeneration we have focussed on the extracellular matrix (ECM) and RGC integrin expression. Our specific questions were: (1) Do adult RGCs express particular sets of integrins in vitro and in vivo? (2) Can the nature of the ECM influence the expression of different integrins? (3) Can the nature of the ECM affect the survival of the cells and the length or branching complexity of their neurites?

METHODS

Primary RGC cultures from adult rat retina were placed on glass coverslips treated with different substrates: Poly-L-Lysine (PL), or PL plus laminin (L), collagen I (CI), collagen IV (CIV) or fibronectin (F). After 10 days in culture, we performed double immunostaining with an antibody against βIII-Tubulin to identify the RGCs, and antibodies against the integrin subunits: αV, α1, α3, α5, β1 or β3. The number of adhering and surviving cells, the number and length of the neurites and the expression of the integrin subunits on the different substrates were analysed.

RESULTS

PL and L were associated with the greatest survival of RGCs while CI provided the least favourable conditions. The type of substrate affected the number and length of neurites. L stimulated the longest growth. We found at least three different types of RGCs in terms of their capacity to regenerate and extend neurites. The different combinations of integrins expressed by the cells growing on different substrata suggest that RGCs expressed predominantly α1β1 or α3β1 on L, α1β1 on CI and CIV, and α5β3 on F. The activity of the integrins was demonstrated by the phosphorylation of focal adhesion kinase (FAK).

CONCLUSIONS

Adult rat RGCs can survive and grow in the presence of different ECM tested. Further studies should be done to elucidate the different molecular characteristics of the RGCs subtypes in order to understand the possible different sensitivity of different RGCs to damage in diseases like glaucoma in which not all RGCs die at the same time.

Dendrofalconerol A suppresses migrating cancer cells via EMT and integrin proteins

BACKGROUND/AIM

Enhanced cell motility is a hallmark of highly metastatic cancer cells. The anti-migratory activity of Dendrofalconerol A (DF-A), a pure bis(bibenzyls) isolated from the stem of Dendrobium falconeri (Orchidaceae) is reported in the present study.

MATERIALS AND METHODS

Cytotoxicity effects of DF-A on H460 lung cancer cells was determined by the MTT assay. We also investigated the mechanism of DF-A-mediated EMT and integrin proteins level by western blotting.

RESULTS

DF-A at concentrations of 0.5-5 μM significantly reduced the protein level of migrating cells in a dose-dependent manner. The expression of migration-related integrins, including integrin β1 and integrin α4 was significantly reduced in response to DF-A treatment. Also, DF-A was shown to suppress epithelial to mesenchymal transition (EMT), as indicated by cadherin switch from N- to E-cadherin and decrease of Snail, Slug and vimentin.

CONCLUSION

This study revealed the potential of DF-A, an anti-metastasis agent and the underlying mechanism in this in vitro assay with H460 cells, which leads to the development of a novel anti-metastatic agent.

Porphyromonas gingivalis GroEL induces osteoclastogenesis of periodontal ligament cells and enhances alveolar bone resorption in rats

Porphyromonas gingivalis is a major periodontal pathogen that contains a variety of virulence factors. The antibody titer to P. gingivalis GroEL, a homologue of HSP60, is significantly higher in periodontitis patients than in healthy control subjects, suggesting that P. gingivalis GroEL is a potential stimulator of periodontal disease. However, the specific role of GroEL in periodontal disease remains unclear. Here, we investigated the effect of P. gingivalis GroEL on human periodontal ligament (PDL) cells in vitro, as well as its effect on alveolar bone resorption in rats in vivo. First, we found that stimulation of PDL cells with recombinant GroEL increased the secretion of the bone resorption-associated cytokines interleukin (IL)-6 and IL-8, potentially via NF-κB activation. Furthermore, GroEL could effectively stimulate PDL cell migration, possibly through activation of integrin α1 and α2 mRNA expression as well as cytoskeletal reorganization. Additionally, GroEL may be involved in osteoclastogenesis via receptor activator of nuclear factor κ-B ligand (RANKL) activation and alkaline phosphatase (ALP) mRNA inhibition in PDL cells. Finally, we inoculated GroEL into rat gingiva, and the results of microcomputed tomography (micro-CT) and histomorphometric assays indicated that the administration of GroEL significantly increased inflammation and bone loss. In conclusion, P. gingivalis GroEL may act as a potent virulence factor, contributing to osteoclastogenesis of PDL cells and resulting in periodontal disease with alveolar bone resorption.

Integrin-mediated type II TGF-β receptor tyrosine dephosphorylation controls SMAD-dependent profibrotic signaling

Tubulointerstitial fibrosis underlies all forms of end-stage kidney disease. TGF-β mediates both the development and the progression of kidney fibrosis through binding and activation of the serine/threonine kinase type II TGF-β receptor (TβRII), which in turn promotes a TβRI-mediated SMAD-dependent fibrotic signaling cascade. Autophosphorylation of serine residues within TβRII is considered the principal regulatory mechanism of TβRII-induced signaling; however, there are 5 tyrosine residues within the cytoplasmic tail that could potentially mediate TβRII-dependent SMAD activation. Here, we determined that phosphorylation of tyrosines within the TβRII tail was essential for SMAD-dependent fibrotic signaling within cells of the kidney collecting duct. Conversely, the T cell protein tyrosine phosphatase (TCPTP) dephosphorylated TβRII tail tyrosine residues, resulting in inhibition of TβR-dependent fibrotic signaling. The collagen-binding receptor integrin α1β1 was required for recruitment of TCPTP to the TβRII tail, as mice lacking this integrin exhibited impaired TCPTP-mediated tyrosine dephosphorylation of TβRII that led to severe fibrosis in a unilateral ureteral obstruction model of renal fibrosis. Together, these findings uncover a crosstalk between integrin α1β1 and TβRII that is essential for TβRII-mediated SMAD activation and fibrotic signaling pathways.

[Change of expression of integrins on multipotent mesenchymal stromal cells isolated from human adipose tissue during long cultivation]

An expression ofintegrins on multipotent mesenchymal stromal cells (MMSCs), isolated from human subcutaneous adipose tissue during long cultivation was studied. Results of the comparative analysis of MMSCs on the 2nd and 17th passages of cultivation revealed considerable distinctions in expression of α1, α4 and α6 integrins on these cells. Strong decrease for 87.2 and 11.2%, quantities of the cells which have been positively stained by AT against CD49a (α1 integrin) and CD49d (α4 integrin), respectively was observed. The share of the cells which have been positively stained by AT against CD49f (α6 integrin) and CD49b (α2 integrin) on the contrary was increased during long cultivation by 9.9 and 2.3%, respectively. The high expression of β1 integrin (98%) on MMSCs, wasn't changed significantly in the course of long cultivation. As a result of induction of MMSCs to a differentiation in the osteogenic direction it was revealed that cells on the 17th passage of cultivation concede by efficiency of formation of cells of bone tissue and extracellular matrix in vitro to cells which induced on the 2nd passage. Thus, long cultivation of MMSCs which is required for building of cellular population after isolation, influences on a cytoskeleton and adhesive abilities of cells that it is necessary to consider when using them for cellular technologies, including for modeling of this or that tissue in three-dimensional scaffolds.

Enhanced integrin-mediated human osteoblastic adhesion to porous amorphous calcium phosphate/poly (L-lactic acid) composite

BACKGROUND

The initial osteoblastic adhesion to materials characterizes the first phase of cell-material interactions and influences all the events leading to the formation of new bone. In a previous work, we developed a novel amorphous calcium phosphate (ACP)/poly(L-lactic acid) (PLLA) material that demonstrated morphologic variations in its microstructure. The aim of this study was to investigate the initial interaction between this material and osteoblastic cells. Cellular attachment and the corresponding signal transduction pathways were investigated.

METHODS

A porous ACP/PLLA composite and PLLA scaffold (as a control) were incubated in fetal bovine serum (FBS) containing phosphate-buffered saline (PBS), and the protein adsorption was determined. Osteoblastic MG63 cells were seeded on the materials and cultured for 1, 4, 8, or 24 hours. Cell attachment was evaluated using the MTS method. Cell morphology was examined using scanning electron microscopy (SEM). The expression levels of the genes encoding integrin subunits α1, α5, αv, β1, focal adhesion kinase (FAK), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were determined using real-time reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

The ACP/PLLA material significantly increased the protein adsorption by 6.4-fold at 1 hour and 2.4-fold at 24 hours, compared with the pure PLLA scaffold. The attachment of osteoblastic cells to the ACP/PLLA was significantly higher than that on the PLLA scaffold. The SEM observation revealed a polygonal spread shape of cells on the ACP/ PLLA, with the filopodia adhered to the scaffold surface. In contrast, the cells on the PLLA scaffold exhibited a spherical or polygonal morphology. Additionally, real-time RT-PCR showed that the genes encoding the integrin subunits α1, αv, β1, and FAK were expressed at higher levels on the ACP/PLLA composite.

CONCLUSIONS

The ACP/PLLA composite promoted protein adsorption and osteoblastic adhesion. The enhanced cell adhesion may be mediated by the binding of integrin subunits α1, αv, and β1, and subsequently may be regulated through the FAK signal transduction pathways.

The structure of integrin α1I domain in complex with a collagen-mimetic peptide

We have determined the structure of the human integrin α1I domain bound to a triple-helical collagen peptide. The structure of the α1I-peptide complex was investigated using data from NMR, small angle x-ray scattering, and size exclusion chromatography that were used to generate and validate a model of the complex using the data-driven docking program, HADDOCK (High Ambiguity Driven Biomolecular Docking). The structure revealed that the α1I domain undergoes a major conformational change upon binding of the collagen peptide. This involves a large movement in the C-terminal helix of the αI domain that has been suggested to be the mechanism by which signals are propagated in the intact integrin receptor. The structure suggests a basis for the different binding selectivity observed for the α1I and α2I domains. Mutational data identify residues that contribute to the conformational change observed. Furthermore, small angle x-ray scattering data suggest that at low collagen peptide concentrations the complex exists in equilibrium between a 1:1 and 2:1 α1I-peptide complex.

Integrin α1 has a long helix, extending from the transmembrane region to the cytoplasmic tail in detergent micelles

Integrin proteins are very important adhesion receptors that mediate cell-cell and cell-extracellular matrix interactions. They play essential roles in cell signaling and the regulation of cellular shape, motility, and the cell cycle. Here, the transmembrane and cytoplasmic (TMC) domains of integrin α1 and β1 were over-expressed and purified in detergent micelles. The structure and backbone relaxations of α1-TMC in LDAO micelles were determined and analyzed using solution NMR. A long helix, extending from the transmembrane region to the cytoplasmic tail, was observed in α1-TMC. Structural comparisons of α1-TMC with reported αIIb-TMC domains indicated different conformations in the transmembrane regions and cytoplasmic tails. An NMR titration experiment indicated weak interactions between α1-TMC and β1-TMC through several α1-TMC residues located at its N-terminal juxta-transmembrane region and C-terminal extended helix region.

Upregulated expression of integrin α1 in mesangial cells and integrin α3 and vimentin in podocytes of Col4a3-null (Alport) mice

Alport disease in humans, which usually results in proteinuria and kidney failure, is caused by mutations to the COL4A3, COL4A4, or COL4A5 genes, and absence of collagen α3α4α5(IV) networks found in mature kidney glomerular basement membrane (GBM). The Alport mouse harbors a deletion of the Col4a3 gene, which also results in the lack of GBM collagen α3α4α5(IV). This animal model shares many features with human Alport patients, including the retention of collagen α1α2α1(IV) in GBMs, effacement of podocyte foot processes, gradual loss of glomerular barrier properties, and progression to renal failure. To learn more about the pathogenesis of Alport disease, we undertook a discovery proteomics approach to identify proteins that were differentially expressed in glomeruli purified from Alport and wild-type mouse kidneys. Pairs of cy3- and cy5-labeled extracts from 5-week old Alport and wild-type glomeruli, respectively, underwent 2-dimensional difference gel electrophoresis. Differentially expressed proteins were digested with trypsin and prepared for mass spectrometry, peptide ion mapping/fingerprinting, and protein identification through database searching. The intermediate filament protein, vimentin, was upregulated ∼2.5 fold in Alport glomeruli compared to wild-type. Upregulation was confirmed by quantitative real time RT-PCR of isolated Alport glomeruli (5.4 fold over wild-type), and quantitative confocal immunofluorescence microscopy localized over-expressed vimentin specifically to Alport podocytes. We next hypothesized that increases in vimentin abundance might affect the basement membrane protein receptors, integrins, and screened Alport and wild-type glomeruli for expression of integrins likely to be the main receptors for GBM type IV collagen and laminin. Quantitative immunofluorescence showed an increase in integrin α1 expression in Alport mesangial cells and an increase in integrin α3 in Alport podocytes. We conclude that overexpression of mesangial integrin α1 and podocyte vimentin and integrin α3 may be important features of glomerular Alport disease, possibly affecting cell-signaling, cell shape and cellular adhesion to the GBM.

Olfactomedin 4 suppresses tumor growth and metastasis of mouse melanoma cells through downregulation of integrin and MMP genes

Olfactomedin 4 (OLFM4) is highly expressed in gastrointestinal cancers and has an anti-apoptotic function. The roles of OLFM4 in tumor growth and metastasis and how it functions in these processes remain elusive. We investigated the function of OLFM4 in tumor growth and metastasis using B16F10 mouse melanoma cells as an experimental system. Our results showed that OLFM4 had no positive effect on cell viability or cell cycle progression in B16F10 cells. However, it significantly suppressed the tumorigenicity of B16F10 cells, i.e., intradermal primary tumor growth and lung metastasis. OLFM4 also suppressed the migration and invasion of B16F10 cells in vitro. For further insight into the mechanisms underlying OLFM4-mediated suppression of tumor progression, we examined the effect of OLFM4 on the expression of integrin and matrix metalloproteinase (MMP), both of which are involved in tumor progression. Overexpression of OLFM4 clearly reduced the expression levels of integrin α1, integrin α4, integrin α5, integrin α6, and MMP9. Moreover, forced expression of MMP9 attenuated the inhibitory activity of OLFM4 on migration and invasiveness. Our findings provide the experimental evidence that OLFM4 may function as a tumor suppressor and an anti-metastatic gene during tumor progression.

Dynamic structural changes are observed upon collagen and metal ion binding to the integrin α1 I domain

We have applied hydrogen-deuterium exchange mass spectrometry, in conjunction with differential scanning calorimetry and protein stability analysis, to examine solution dynamics of the integrin α1 I domain induced by the binding of divalent cations, full-length type IV collagen, or a function-blocking monoclonal antibody. These studies revealed features of integrin activation and α1I-ligand complexes that were not detected by static crystallographic data. Mg(2+) and Mn(2+) stabilized α1I but differed in their effects on exchange rates in the αC helix. Ca(2+) impacted α1I conformational dynamics without altering its gross thermal stability. Interaction with collagen affected the exchange rates in just one of three metal ion-dependent adhesion site (MIDAS) loops, suggesting that MIDAS loop 2 plays a primary role in mediating ligand binding. Collagen also induced changes consistent with increased unfolding in both the αC and allosteric C-terminal helices of α1I. The antibody AQC2, which binds to α1I in a ligand-mimetic manner, also reduced exchange in MIDAS loop 2 and increased exchange in αC, but it did not impact the C-terminal region. This is the first study to directly demonstrate the conformational changes induced upon binding of an integrin I domain to a full-length collagen ligand, and it demonstrates the utility of the deuterium exchange mass spectrometry method to study the solution dynamics of integrin/ligand and integrin/metal ion interactions. Based on the ligand and metal ion binding data, we propose a model for collagen-binding integrin activation that explains the differing abilities of Mg(2+), Mn(2+), and Ca(2+) to activate I domain-containing integrins.

Structure of collagen receptor integrin α(1)I domain carrying the activating mutation E317A

We have analyzed the structure and function of the integrin α(1)I domain harboring a gain-of-function mutation E317A. To promote protein crystallization, a double variant with an additional C139S mutation was used. In cell adhesion assays, the E317A mutation promoted binding to collagen. Similarly, the double mutation C139S/E317A increased adhesion compared with C139S alone. Furthermore, soluble α(1)I C139S/E317A was a higher avidity collagen binder than α(1)I C139S, indicating that the double variant represents an activated form. The crystal structure of the activated variant of α(1)I was solved at 1.9 Å resolution. The E317A mutation results in the unwinding of the αC helix, but the metal ion has moved toward loop 1, instead of loop 2 in the open α(2)I. Furthermore, unlike in the closed αI domains, the metal ion is pentacoordinated and, thus, prepared for ligand binding. Helix 7, which has moved downward in the open α(2)I structure, has not changed its position in the activated α(1)I variant. During the integrin activation, Glu(335) on helix 7 binds to the metal ion at the metal ion-dependent adhesion site (MIDAS) of the β(1) subunit. Interestingly, in our cell adhesion assays E317A could activate collagen binding even after mutating Glu(335). This indicates that the stabilization of helix 7 into its downward position is not required if the α(1) MIDAS is already open. To conclude, the activated α(1)I domain represents a novel conformation of the αI domain, mimicking the structural state where the Arg(287)-Glu(317) ion pair has just broken during the integrin activation.

HMGN5: a potential oncogene in gliomas

Gliomas are the most common primary brain tumors in the central nervous system and a leading cause of tumor-related death. High-mobility group nucleosome binding domain 5 (HMGN5/NSBP1), which is highly expressed in breast cancer and in hormone-induced mouse uterine adenocarcinoma, acts as a potential oncogene in gliomas. In this study, the role of HMGN5 in the proliferation of human glioma cells was investigated by lentivirus-mediated RNA interference (RNAi). The decrease in HMGN5 expression in human glioma U251 and U87 cells caused cell cycle arrest in the G1 phase and a delay in cell proliferation, as well as resulting in more apoptosis and an inhibition of clonogenic growth in soft agar in U251 cells; these results suggest that HMGN5 is required for tumorigenesis in vitro. Furthermore, HMGN5 was highly expressed in both high-grade and low-grade glioma tissue samples compared with normal brain tissues. Collectively, our data suggest that HMGN5 may play a critical role in the development of gliomas.

An engineered alpha1 integrin-binding collagenous sequence

Collagen is an extracellular matrix structural component that can regulate cellular processes through its interaction with the integrins, α1β1, α2β1, α10β1, and α11β1. Collagen-like proteins have been identified in a number of bacterial species. Here, we used Scl2 from Streptococcus pyogenes serotype M28 strain MGAS6274 as a backbone for the introduction of discrete integrin-binding sequences. The introduced sequences GLPGER, GFPGER, or GFPGEN did not affect triple helix stability of the Scl (Streptococcal collagen-like) protein. Using ELISA and surface plasmon resonance, we determined that Scl2(GLPGER) and Scl2(GFPGER) bound to recombinant human α1 and α2 I-domains in a metal ion-dependent manner and without a requirement for hydroxyproline. We predicted a novel and selective integrin-binding sequence, GFPGEN, through the use of computer modeling and demonstrated that Scl2(GFPGEN) shows specificity toward the α1 I-domain and does not bind the α2 I-domain. Using C2C12 cells, we determined that intact integrins interact with the modified Scl2 proteins with the same selectivity as recombinant I-domains. These modified Scl2 proteins also acted as cell attachment substrates for fibroblast, endothelial, and smooth muscle cells. However, the modified Scl2 proteins were unable to aggregate platelets. These results indicate that Scl2 is a suitable backbone for the introduction of mammalian integrin-binding sequences, and these sequences may be manipulated to individually target α1β1 and α2β1.

Changes in chondrogenic phenotype and gene expression profiles associated with the in vitro expansion of human synovium-derived cells

We undertook this study to characterize changes in the proliferative capacities, chondrogenic phenotypes, and gene expression profiles of human synovium-derived progenitor cells from osteoarthritic patients during in vitro expansion. Cells isolated from osteoarthritic synovia were cultured, and growth rates during serial passages were evaluated. Surface molecule expressions were determined by flow cytometry and cytogenetic analyses were performed. After chondrogenic differentiation in cell pellets, we evaluated type II collagen and glycosaminoglycan (GAG) synthesis. To assess whether the in vitro expansion of synovium-derived cells affects gene expression, we performed microarray analyses on cells at passage 0, 1, 2, 4, 6, and 8. Synovium-derived cells were rapidly expanded in vitro through passage 8 (about 130 days), and after passage 6, the proliferation rates decreased slightly with a wide range of individual variations. The expressions of CD166, CD49a, and CD106 decreased, whereas those of CD10, CD29, CD44, CD73, CD90, and CD105 showed no significant change. Karyotype analysis revealed no evidence of chromosome abnormalities. The staining of type II collagen and GAG in differentiated cell pellets showed rapid weakening. Genome-wide microarray analysis showed that synovium-derived cells from late passages over-expressed genes associated with cell cycle prolongation and cell aging, and less-expressed genes associated with cell growth stimulation. The in vitro expansion of synovium-derived cells was accompanied with decreased proliferative capacity and the chondrogenic phenotype, which might be modulated by change in gene expression patterns.

Quantitative proteomics identifies a Dab2/integrin module regulating cell migration

Clathrin-associated endocytic adapters recruit cargoes to coated pits as a first step in endocytosis. We developed an unbiased quantitative proteomics approach to identify and quantify glycoprotein cargoes for an endocytic adapter, Dab2. Surface levels of integrins beta1, alpha1, alpha2, and alpha3 but not alpha5 or alphav chains were specifically increased on Dab2-deficient HeLa cells. Dab2 colocalizes with integrin beta1 in coated pits that are dispersed over the cell surface, suggesting that it regulates bulk endocytosis of inactive integrins. Depletion of Dab2 inhibits cell migration and polarized movement of integrin beta1 and vinculin to the leading edge. By manipulating intracellular and surface integrin beta1 levels, we show that migration speed correlates with the intracellular integrin pool but not the surface level. Together, these results suggest that Dab2 internalizes integrins freely diffusing on the cell surface and that Dab2 regulates migration, perhaps by maintaining an internal pool of integrins that can be recycled to create new adhesions at the leading edge.

FAK activation and the role of epithelial membrane protein 2 (EMP2) in collagen gel contraction

PURPOSE

Proliferative vitreoretinopathy (PVR) occurs in approximately 10% of patients after retinal detachment. PVR results from a multiphase process that leads to an aberrant wound-healing strategy with contractile cellular forces and tractional retinal detachment (TRD). Epithelial membrane protein (EMP) 2 controls cell surface expression and function of integrin isoforms associated with cellular contraction in many cell types. Since EMP2 is highly expressed in retinal pigment epithelium, this study investigates the role of EMP2 in collagen gel contraction.

METHODS

EMP2 expression was recombinantly modified in the ARPE-19 cell line. Cell surface integrin expression was assessed by flow cytometry. Collagen gel contraction was assessed by using an in vitro assay and the percentage of contraction was quantified. Proliferation and migration were measured by BrdU incorporation and a wound-healing assay, respectively. Cellular invasion was investigated with polycarbonate membranes coated with collagen.

RESULTS

EMP2 expression levels correlated positively with the ability to contract collagen gels. Compared with wild-type ARPE-19 cells, the cells with increased EMP2 expression exhibited enhanced contraction (P = 0.02), and decreased EMP2 expression concomitantly resulted in decreased contraction (P = 0.002). EMP2 overexpression resulted in reduced proliferation, migration, and integrin alpha1 and alpha2 integrin expression. EMP2 overexpression was associated with a 70% increase in FAK activation (P = 0.0003) and relative resistance of gel contraction to inhibitors of FAK/Src activation.

CONCLUSIONS

ARPE-19-mediated collagen gel contraction is a multistep process that requires integrin ligation and activation of the FAK/Src complex. EMP2 positively modulates collagen gel contraction by ARPE-19 cells through increased FAK activation.

Multiple alpha subunits of integrin are involved in cell-mediated responses of the Manduca immune system

The cell-mediated responses of the insect innate immune system-phagocytosis, nodulation, encapsulation-involve multiple cell adhesion molecules of hemocyte surfaces. A hemocyte-specific (HS) integrin and a member of the immunoglobulin (Ig) superfamily (neuroglian) are involved in the encapsulation response of hemocytes in Manduca sexta. In addition, two new integrin alpha (alpha) subunits have been found on these hemocytes. The alpha2 subunit is mainly expressed in epidermis and Malphigian tubules, whereas the alpha3 subunit is primarily expressed on hemocytes and fat body cells. Of the three known alpha subunits, the alpha1 subunit found in HS integrin is the predominant subunit of hemocytes. Cell adhesion assays indicate that alpha2 belongs to the integrin family with RGD-binding motifs, confirming the phylogenetic analysis of alpha subunits based on the amino-acid sequence alignment of different alpha subunits. Double-stranded RNAs (dsRNAs) targeting each of these three integrin alpha subunits not only specifically decreased transcript expression of each alpha subunit in hemocytes, but also abolished the cell-mediated encapsulation response of hemocytes to foreign surfaces. The individual alpha subunits of M. sexta integrins, like their integrin counterparts in mammalian immune systems, have critical, individual roles in cell-substrate and cell-cell interactions during immune responses.

The alpha1beta1 integrin and TNF receptor II protect airway CD8+ effector T cells from apoptosis during influenza infection

Primary viral infections of the lung induce potent effector CD8 T cell responses. To function in the influenza-infected airways, CD8 T cells must be able to resist cell death. The majority of the CD8 T cells in the airways and lung parenchyma expressed CD49a, the alpha-chain of the type IV collagen receptor VLA-1, and these cells were highly activated, producing both IFN-gamma and TNF-alpha. In the airways, where type IV collagen is abundant, but not the spleen, the CD49a(+) CD8 cells had reduced proportions of annexin V and caspase 8, and >80% expressed the TNF-alpha receptor II, while Fas, TNFR-I, and CD27 expression were similar to CD49a(-) cells. Furthermore, the CD49a(+), but not CD49a(-), CD8 T cells from the airways were resistant to active induction of apoptosis in the presence of type IV collagen and TNF-alpha in vitro. We propose that TNFR-II and the VLA-1 synergize to protect effector CD8 T cells in the infected airways from apoptosis during the acute infection.

Role of the α1 integrin cytoplasmic tail in the formation of focal complexes, actin organization, and in the control of cell migration

Integrins play a key role in cellular motility; an essential process for embryonic development and tissue morphogenesis, and also for pathological processes such as tumor cell invasion and metastasis. Recently, we showed that the cytoplasmic tail of integrin alpha(1) regulates the formation of focal complexes, F-actin cytoskeleton reorganization, and migration. We now report that the alpha(1) tail directly engages in collagen IV-mediated migration by regulation of the small GTPase Rac1. Deletion variants of the alpha(1) integrin differ in their ability to activate Rac1. Constitutively active Rac1 rescues motility in otherwise immotile cells expressing a truncated alpha(1) integrin without any cytoplasmic tail. In these cells, levels of GTP-Rac1 are constitutively elevated, but kept non-functional in the cytoplasm. The conserved GFFKR motif is sufficient to convey Rac1 activation, but downregulates the amount of GTP-Rac1 in the absence of the alpha(1)-specific sequence PLKKKMEK. This sequence is also required for the recruitment of PI3K to focal adhesions following Rac1 activation. Our results demonstrate that the short alpha(1) cytoplasmic tail is crucial for Rac1 activation and PI3K localization, which in turn results in cytoskeletal rearrangement and subsequent migration.

Selection using the alpha-1 integrin (CD49a) enhances the multipotentiality of the mesenchymal stem cell population from heterogeneous bone marrow stromal cells

Bone marrow-derived mesenchymal stem cells consist of a developmentally heterogeneous population of cells obtained from colony forming progenitors. As these colonies express the alpha-1 integrin (CD49a), here we single-cell FACS sorted CD49a+ cells from bone marrow in order to create clones and then compared their colony forming efficiency and multilineage differentiation capacity to the unsorted cells. Following selection, 40% of the sorted CD49a+ cells formed colonies, whereas parental cells failed to form colonies following limited dilution plating at 1 cell/well. Following ex vivo expansion, clones shared a similar morphology to the parental cell line, and also demonstrated enhanced proliferation. Further analysis by flow cytometry using a panel of multilineage markers demonstrated that the CD49a+ clones had enhanced expression of CD90 and CD105 compared to unsorted cells. Culturing cells in adipogenic, osteogenic or chondrogenic medium for 7, 10 and 15 days respectively and then analysing them by quantitative PCR demonstrated that CD49a+ clones readily underwent multlineage differentiation into fat, bone and cartilage compared to unsorted cells. These results thus support the use of CD49a selection for the enrichment of mesenchymal stem cells, and describes a strategy for selecting the most multipotential cells from a heterogeneous pool of bone marrow mononuclear stem cells.

Role of alpha1beta1-integrin in arterial stiffness and angiotensin-induced arterial wall hypertrophy in mice

We examined the arterial phenotype of mice lacking alpha(1)-integrin (alpha(1)(-/-)) at baseline and after 4 wk of ANG II or norepinephrine (NE) administration. Arterial mechanical properties were determined in the carotid artery (CA). Integrin expression, MAPK kinases, and focal adhesion kinase (FAK) were assessed in the aorta. No change in arterial pressure was observed in alpha(1)(-/-) mice. Elastic modulus-wall stress curves were similar in alpha(1)(-/-) and alpha(1)(+/+) animals, indicating no change in arterial stiffness. The rupture pressure was lower in alpha(1)(-/-) mice, demonstrating decreased mechanical strength. Lack of alpha(1)-integrin was accompanied by an increase in beta(1)-, alpha(v)-, and alpha(5)-integrins but no change in alpha(2)-integrin. ANG II increased medial cross-sectional area of the CA in alpha(1)(+/+), but not alpha(1)(-/-), mice, whereas equivalent pressor doses of NE did not produce a significant increase in either group. In alpha(1)(+/+) mice, ANG II induced alpha(1)-integrin expression and smooth muscle cell (SMC) hypertrophy in the CA in association with increased aortic expression of alpha-smooth muscle actin and smooth muscle myosin heavy chain and phosphorylation of ERK1/2, p38 MAPK, and FAK. ANG II did not induce SMC hypertrophy or phosphorylation of p38 MAPK and FAK in alpha(1)(-/-) mice. A functional anti-alpha(1)-integrin antibody inhibited in vitro the ANG II-induced phosphorylation of FAK and p38 MAPK. In conclusion, alpha(1)(-/-) mice exhibit a reduced mechanical strength at baseline and a lack of ANG II-induced SMC hypertrophy. These results emphasize the importance of alpha(1)beta(1)-integrin in p38 MAPK and FAK phosphorylation during vascular hypertrophy in response to ANG II.

Bcl-2 expression modulates cell adhesion and migration promoting branching of ureteric bud cells

Bcl-2 is the founding member of a family of proteins that influence apoptosis. During kidney development bcl-2 not only acts as a survival factor, but may also impact cell adhesive mechanisms and by extension branching morphogenesis. The interrelationship between cell adhesion, migration and apoptosis, important during development, is poorly understood. Here we examined the impact lack of bcl-2, an inhibitor of apoptosis, has on ureteric bud (UB) cell adhesion, migration, and branching morphogenesis. Bcl-2 -/- UB cells demonstrated increased cell migration, increased cell invasion and decreased adhesion to vitronectin and fibronectin compared with wild-type cells. Bcl-2 +/+ UB cells readily branched in collagen gel and Matrigel while bcl-2 -/- UB cells did not undergo significant branching in either matrix. Re-expression of bcl-2 in bcl-2 -/- UB cells restored their ability to undergo branching morphogenesis in Matrigel. Consistent with our in vitro data, we show that in the absence of bcl-2, embryonic kidneys undergo decreased UB branching. We observed decreased numbers of UB branch points, UB branch tips and a decreased distance to the first UB branch point in the absence of bcl-2. The alterations in bcl-2 -/- UB cell adhesion and migration was also associated with a significant alteration in expression of a number of extracellular matrix proteins. Bcl-2 -/- UB cells exhibited increased fibronectin expression and decreased thrombospondin-1 and osteopontin expression. Taken together, these data suggest that bcl-2 is required for the proper regulation of cell adhesive and migratory mechanisms, perhaps through modulation of the cellular microenvironment.

Dexamethasone induces the expression of metalloproteinase inhibitor TIMP-1 in the murine cerebral vascular endothelial cell line cEND

In many neuroinflammatory conditions, including multiple sclerosis (MS), encephalitis, meningitis, brain tumours and cerebral ischaemia, the matrix metalloproteinases (MMPs) play an important role in disrupting the blood-brain barrier (BBB). Normally under tight regulation, increased MMP-9 cerebrospinal fluid levels and excessive proteolytic activity is detected in the blood and cerebrospinal fluid in patients with acute MS. MMP-9 is a member of the type IV collagenases, which attack components of the endothelial basal lamina, including type IV collagen. The disruption of the BBB and clinical symptoms can be reduced with different inhibitors to MMPs including activators of tissue inhibitor of metalloproteinases-1 (TIMP-1), the cognate tissue inhibitor of MMP-9. Since intravenous glucocorticoid (GC) treatment reduces the levels of MMP-9 markedly in patients, we hypothesized that GC effects might be mediated by transcriptional activation of the TIMP-1 gene in addition to reported repressive effects on MMP-9 transcription. Our results provide direct evidence that GCs increase TIMP-1 in the brain endothelial cell line cEND, prevent alterations in microvascular integrin alpha1 subunit expression and help maintain endothelial barrier function in response to pro-inflammatory stimuli (TNFalpha administration). GC-induced up-regulation of TIMP-1 expression by the CNS vascular endo-thelium may thus play a role in preservation of the endothelial basal lamina and maintain integrin alpha1 and tight junction protein expression important for vessel wall integrity.

Importance of force linkage in mechanochemistry of adhesion receptors

The alpha subunit-inserted (I) domain of integrin alphaLbeta2 [lymphocyte function-associated antigen-1 (LFA-1)] binds to intercellular adhesion molecule-1 (ICAM-1). The C- and N-termini of the alpha I domain are near one another on the "lower" face, opposite the metal ion-dependent adhesion site (MIDAS) on the "upper face". In conversion to the open alpha I domain conformation, a 7 A downward, axial displacement of C-terminal helix alpha7 is allosterically linked to rearrangement of the MIDAS into its high-affinity conformation. Here, we test the hypothesis that when an applied force is appropriately linked to conformational change, the conformational change can stabilize adhesive interactions that resist the applied force. Integrin alpha I domains were anchored to the cell surface through their C- or N-termini using type I or II transmembrane domains, respectively. C-terminal but not N-terminal anchorage robustly supported cell rolling on ICAM-1 substrates in shear flow. In contrast, when the alphaL I domain was mutationally stabilized in the open conformation with a disulfide bond, it mediated comparable levels of firm adhesion with type I and type II membrane anchors. To exclude other effects as the source of differential adhesion, these results were replicated using alpha I domains conjugated through the N- or C-terminus to polystyrene microspheres. Our results demonstrate a mechanical feedback system for regulating the strength of an adhesive bond. A review of crystal structures of integrin alpha and beta subunit I domains and selectins in high- and low-affinity conformations demonstrates a common mechanochemical design in which biologically applied tensile force stabilizes the more extended, high-affinity conformation.

A mandibular propulsive appliance modulates collagen-binding integrins distribution in the young rat condylar cartilage

We have previously shown that a mandibular propulsive appliance (MPA) stimulates cell proliferation and the synthesis of growth factors in the rat condylar cartilage. The aim of this study was to evaluate the effects of a MPA in the distribution of the integrin subunits alpha1 and alpha2 in this cartilage. Twenty eight days-old male Wistar rats were divided into treated (T) and age-matched control groups (C). Treated rats wore the appliance during 3, 5, 7, 9, 11, 15, 20, 30 and 35 days. The condyles were fixed, decalcified and paraffin-embedded. The distribution of alpha1 and alpha2 was studied by immunohistochemistry. Alpha1 distribution was uniform along the cartilage, increasing in 48 days-old rats (C20). Treated animals anticipated this increase to the age of 36 days (T9). The number of alpha2-positive cells was increased in C9 in the anterior condylar region, in C9 and C20 in the middle region and showed no differences in the posterior region. The MPA apparently abolished all variations, leading to a single increase at T30 in all regions. These results suggest that integrins containing the alpha1 and alpha2 subunits are modulated by forces promoted by the MPA, participating of the biological response to this therapy.

Mesenchymal progenitor cells communicate via alpha and beta integrins with a three-dimensional collagen type I matrix

BACKGROUND/AIMS

The aim of our study was to investigate interactions of mesenchymal progenitor cells (MPCs) with collagen matrices.

METHODS

Human bone-marrow-derived MPCs were cultivated in collagen type I gels with and without inhibition of beta(1)-integrin by a specific antibody. Collagen gel contraction, cell morphology, expression of integrin subunits and several genes related to matrix synthesis and turnover as well as MPC differentiation were analyzed over 14 days.

RESULTS

Human MPCs markedly contracted free-floating collagen gels. Contraction was nearly completely inhibited by blocking beta(1)-integrin. Cellular morphology was elongated in the absence and mostly round in the presence of the antibody. Expression of integrin alpha(1), alpha(2) and beta(1) subunits showed several changes partly dependent on beta(1)-integrin blocking. Expression of matrix metalloproteinase-1 was elevated irrespective of beta(1)-integrin blocking and tenascin-C was subsequently induced during gel contraction. Spontaneous induction of chondrogenic, osteogenic or adipogenic differentiation was observed neither in the presence nor in the absence of the beta(1)-integrin antibody.

CONCLUSION

Our results indicate that the interaction of human MPCs with fibrillar collagen type I involves beta(1)- and alpha-integrin subunits and induces changes in gene expression related to extracellular matrix synthesis and turnover but not differentiation to the chondrogenic, osteogenic or adipogenic phenotype.

Glomerular injury is exacerbated in diabetic integrin α1-null mice

Excessive glomerular collagen IV and reactive oxygen species (ROS) production are key factors in the development of diabetic nephropathy. Integrin alpha1beta1, the major collagen IV receptor, dowregulates collagen IV and ROS production, suggesting this integrin might determine the severity of diabetic nephropathy. To test this possibility, wild-type and integrin alpha1-null mice were rendered diabetic with streptozotocin (STZ) (100 mg/kg single intraperitoneal injection), after which glomerular filtration rate (GFR), glomerular collagen deposition, and glomerular basement membrane (GBM) thickening were evaluated. In addition, ROS and collagen IV production by mesangial cells as well as their proliferation was measured in vitro. Diabetic alpha1-null mice developed worse renal disease than diabetic wild-type mice. A significant increase in GFR was evident in the alpha1-null mice at 6 weeks after the STZ injection; it started to decrease by week 24 and reached levels of non-diabetic mice by week 36. In contrast, GFR only increased in wild-type mice at week 12 and its elevation persisted throughout the study. Diabetic mutant mice also showed increased glomerular deposition of collagen IV and GBM thickening compared to diabetic wild-type mice. Primary alpha1-null mesangial cells exposed to high glucose produced more ROS than wild-type cells, which led to decreased proliferation and increased collagen IV synthesis, thus mimicking the in vivo finding. In conclusion, this study suggests that lack of integrin alpha1beta1 exacerbates the glomerular injury in a mouse model of diabetes by modulating GFR, ROS production, cell proliferation, and collagen deposition.

Identification of integrin alpha1 as an interacting protein of protein tyrosine phosphatase PRL-3

PRL-3 is a newly identified protein tyrosine phosphatase associated with tumor metastasis. It is over-expressed in various cancers, such as colorectal cancer, gastric cancer, and ovarian cancer, and is correlated with the progression and survival of cancers. Although PRL-3 plays a causative role in promoting cancer cell invasion and metastasis, the molecular mechanism is unknown. To investigate PRL-3's roles in tumorigenesis and signal transduction pathway, we screened the human placenta brain cDNA library with the bait of PRL-3 in yeast two-hybrid system. Then we identified integrin alpha1 as a PRL-3-interacting protein for the first time, and verified this physical association with pull-down and co-immunoprecipitation assays. Furthermore, we found that PRL-3 could down-regulate the tyrosine-phosphorylation level of integrin beta1 and increased the phosphorylation level of Erk1/2. Our present discovery will provide new clues for elucidating the molecular mechanism of PRL-3 in promoting cancer invasion and metastasis.

Fluorescently labeled collagen binding proteins allow specific visualization of collagen in tissues and live cell culture

Visualization of the formation and orientation of collagen fibers in tissue engineering experiments is crucial for understanding the factors that determine the mechanical properties of tissues. In this study, collagen-specific fluorescent probes were developed using a new approach that takes advantage of the inherent specificity of collagen binding protein domains present in bacterial adhesion proteins (CNA35) and integrins (GST-alpha1I). Both collagen binding domains were obtained as fusion proteins from an Escherichia coli expression system and fluorescently labeled using either amine-reactive succinimide (CNA35) or cysteine-reactive maleimide (GST-alpha1I) dyes. Solid-phase binding assays showed that both protein-based probes are much more specific than dichlorotriazinyl aminofluorescein (DTAF), a fluorescent dye that is currently used to track collagen formation in tissue engineering experiments. The CNA35 probe showed a higher affinity for human collagen type I than did the GST-alpha1I probe (apparent K(d) values of 0.5 and 50 microM, respectively) and showed very little cross-reactivity with noncollagenous extracellular matrix proteins. The CNA35 probe was also superior to both GST-alpha1I and DTAF in visualizing the formation of collagen fibers around live human venous saphena cells. Immunohistological experiments on rat tissue showed colocalization of the CNA35 probe with collagen type I and type III antibodies. The fluorescent probes described here have important advantages over existing methods for visualization of collagen, in particular for monitoring the formation of collagen in live tissue cultures over prolonged time periods.

Electroacupuncture up-regulates natural killer cell activity Identification of genes altering their expressions in electroacupuncture induced up-regulation of natural killer cell activity

As an important cellular component of the innate immune system, NK cells constitute a first line of defense against various infections and malignancies. Previous studies have reported electroacupuncture (EA) modulation of natural killer cell (NK cell) activities. Our study confirmed that EA treatment increases NK cell activity using (51)Cr release assay. Furthermore, in order to better understand the activation mechanism of NK cell by EA, we employed a cDNA microarray technique to elucidate how EA alters gene expressions in the spleen of rats. We screened EA responsive genes using a high-throughput screening and identified 154 genes. Among those genes we selected 4 genes that are known to play a crucial role in NK cell activation and examined their mRNA expressions after EA treatment using RT-PCR. Our data shows that EA treatment increased CD94, PTK and VCAM-1 expressions while decreased PTP and SHP-1. These results imply that EA treatment increase PTK expression, which increases NK cell activity, through induction of CD94 while decreases SHP-1, which inhibits NK cell activity, simultaneously so that it activates NK cell with high efficacy. It seems that increased VCAM-1 expression is due to INF-gamma produced by activated NK cell. Increased production of VCAM-1 is expected to play an important role in binding of NK cell to the target cell. The result of our study may provide key insights in understanding the mechanisms of activation of NK cell induced by EA.

Expression of alpha 1 and beta 3 integrins subunits in the endometrium of patients with tubal phimosis or hydrosalpinx

OBJECTIVE

To determine the expression of alpha1 and beta3 integrin subunit on the endometrium of infertile patients with hydrosalpinx and infertile patients with tubal phimosis.

DESIGN

Case-control study.

SETTING

Tertiary medical center.

PATIENT(S)

Infertile patients with radiologic or laparoscopic diagnosis of hydrosalpinx (n = 11) or tubal phimosis (n = 12) as the only cause of infertility, and fertile controls (n = 17).

INTERVENTION(S)

Immunohistochemical analysis of alpha1 and beta3 integrin subunits was performed on endometrial biopsies obtained during the implantation window.

MAIN OUTCOME MEASURE(S)

Histologic score (HSCORE) on luminal and glandular endometrium of the patients with hydrosalpinx or tubal phimosis and the normal fertile controls.

RESULT(S)

The median (+/-SEM) HSCORE for beta3 subunit expression in endometrial glands was 0.39 +/- 0.23 and 0.42 +/- 0.18 for tubal phimosis and hydrosalpinx, respectively, and 1.74 +/- 0.26 for fertile controls. The median HSCORE for beta3 subunit expression in luminal epithelium for tubal phimosis, hydrosalpinx, and fertile controls was 0.07 +/- 0.06, 0.21 +/- 0.18, and 1.03 +/- 0.31, respectively. No statistical difference was observed on the expression of alpha1 integrin subunit expression between the three groups.

CONCLUSION(S)

The endometrial expression of beta3 integrin subunit is reduced in the presence of tubal phimosis or hydrosalpinx, during the window of implantation.

Isolation of C15: A novel antibody generated by phage display against mesenchymal stem cell-enriched fractions of adult human marrow

Adult bone marrow stroma contains a source of mesenchymal stem cells (MSC) that have the capacity to self-renew and differentiate into multiple stromal lineages. These rare cells can be visualised indirectly by the formation of heterogeneous colonies, containing stem cells and their differentiated progeny in long-term culture. If MSC and their associated progenitor and precursor populations are to reach their full therapeutic potential, markers will be required to identify and characterize specific bone marrow stromal subsets. We sought to use phage display to generate antibodies against bone marrow mononuclear cells (BMMNC) enriched for colony forming cells. Initially, we identified our target cell population by comparing the colony forming efficiency (CFE) of CD49a-positive, STRO-1-positive and CD45-negative BMMNC subpopulations with unseparated BMMNC. Selection with anti-CD49a gave the greatest enrichment (19-fold) of colony forming cells and in light of these findings, we generated phage antibodies against CD49a-positive BMMNC by simultaneous positive/negative selection. A dominant clone (C15), generated after 3 rounds of selection, has been isolated and sequenced, then characterized for cell and tissue specificity. Sequence analysis showed that the V(H) and V(L) gene segments of C15 aligned most closely to the VH26/DP-47 and IGLV3S1/DPL16 germline V segments found in the synthetic repertoire. C15 bound to 4% of freshly isolated BMMNC and localized to osteoblastic cells and proximal marrow cells in areas of active bone formation in sections of osteophyte. C15 binding was upregulated in cultured bone marrow stromal cells (BMSC) and was also detected on bone-derived cell lines. This report demonstrates that phage display is a powerful tool for the isolation of antibodies against rare cell populations, and provides a platform for the future application of this technology in the search for antigens on MSC and other rare cell populations.

Endocytosis of beta1 integrins is an early event in migration promoted by the cell adhesion molecule L1

Directional cell motility is a complex process requiring orchestration of signals from diverse cell adhesion receptors for proper organization of neuronal groups in the brain. The L1 cell adhesion molecule potentiates integrin-dependent migration of neuronal cells and stimulates integrin endocytosis but its mechanism of action is unclear. The hypothesis was investigated that L1 stimulates cell motility by modulating surface levels of integrins through intracellular trafficking using a model cell system. Antibody-induced clustering of L1, which mimics ligand binding, induced formation of cell surface complexes of L1 and beta1 integrins in L1-expressing HEK293 cells. L1 formed cell surface complexes with integrin beta1 and alpha3 subunits but not with integrin alpha1. Following cell surface clustering, beta1 integrins and L1 became rapidly internalized into Rab5+ early endosomes. Internalization of L1 and beta1 integrins was prevented by treatment with monodansyl cadaverine (MDC), an inhibitor of clathrin-dependent endocytosis, and by deletion of the AP2/clathrin binding motif (RSLE) from the L1 cytoplasmic domain. MDC treatment coordinately inhibited L1-potentiated haptotactic migration of HEK293 cells to fibronectin in Transwell assays. These results suggested that downregulation of adhesive complexes of L1 and beta1 integrin at the plasma membrane by clathrin-mediated endocytosis is a potential mechanism for enhancing cell motility.

Phenotypic heterogeneity influences the behavior of rat aortic smooth muscle cells in collagen lattice

Phenotypic modulation of vascular smooth muscle cells (SMCs) in atherosclerosis and restenosis involves responses to the surrounding microenvironment. SMCs obtained by enzymatic digestion from tunica media of newborn, young adult (YA) and old rats and from the thickened intima (TI) and underlying media of young adult rat aortas 15 days after ballooning were entrapped in floating populated collagen lattice (PCL). TI-SMCs elongated but were poor at PCL contraction and remodeling and expressed less alpha2 integrin compared to other SMCs that appeared more dendritic. During early phases of PCL contraction, SMCs showed a marked decrease in the expression of alpha-smooth muscle actin and myosin. SMCs other than TI-SMCs required 7 days to re-express alpha-smooth muscle actin and myosin. Only TI-SMCs in PCL were able to divide in 48 h, with a greater proportion in S and G2-M cell cycle phases compared to other SMCs. Anti-alpha2 integrin antibody markedly inhibited contraction but not proliferation in YA-SMC-PLCs; anti-alpha1 and anti-alpha2 integrin antibodies induced a similar slight inhibition in TI-SMC-PCLs. Finally, TI-SMCs rapidly migrated from PCL on plastic reacquiring their epithelioid phenotype. Heterogeneity in proliferation and cytoskeleton as well the capacity to remodel the extracellular matrix are maintained, when SMCs are suspended in PCLs.