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At least 127 records · Page 7Linked to original sources
PubMed1994

Enhanced leucocyte adhesion to interleukin-1 beta stimulated vascular smooth muscle cells is mainly through intercellular adhesion molecule-1.

OBJECTIVE: The aim was to investigate whether interleukin-1 beta (IL-1 beta) plays a role in modulating the adhesion of monocytes and neutrophils to vascular smooth muscle cells, and to identify what molecules on these cells may be involved in the adhesion. METHODS: Rat aortic smooth muscle cells were challenged with IL-1 beta and tested for adhesion of prelabelled monocytes and neutrophils. Northern analysis, reverse transcription/polymerase chain reaction (RT/PCR), and immunocytochemical staining were used to measure the changes of intercellular adhesion molecule-1 (ICAM-1) and other adhesion molecules in response to IL-1 beta stimulation. Neutralising antibody against ICAM-1 was used to demonstrate a role of ICAM-1 in this IL-1 beta induced adhesion. RESULTS: IL-1 beta induced the adhesion of monocytes and neutrophils to aortic smooth muscle cells in a concentration and time dependent manner. IL-1 beta-induced adhesion was inhibited by preincubation of the cells with an IL-1 receptor antagonist (IL-1ra). Northern analysis and RT/PCR showed that ICAM-1 mRNA represents a predominant adhesion molecule induced by IL-1 beta, and that the expression of ICAM-1 mRNA precedes and parallels the induced adhesion profiles of aortic smooth muscle cells for leucocytes. Immunocytochemical staining confirmed the IL-1 beta induced ICAM-1 expression on the smooth muscle cells. Moreover, a monoclonal anti-rat ICAM-1 antibody produced a concentration dependent inhibition of the IL-1 beta induced adhesion of monocytes and neutrophils to the smooth muscle cells. CONCLUSIONS: IL-1 beta actively regulates functional ICAM-1 expression in vascular smooth muscle cells. The IL-1 beta-induced expression of ICAM-1 on the smooth muscle cells may be an important contributor to the increased adhesion by monocytes and neutrophils to these cells and suggests that IL-1 beta might play a role in the proinflammatory and immune functions of the modified smooth muscle cells during atherosclerosis and restenosis.

Animals↗
PubMed1993

The phospholipase-A2 reaction leads to increased monocyte adhesion of endothelial cells via the expression of adhesion molecules.

Mononuclear cell invasion into the vascular-vessel wall is a very important initial step in the development of atherosclerotic lesions. Hypercholesterolemia leads to a marked adhesion of circulating blood monocytes to arterial endothelial cells in vivo, and minimally oxidized low-density lipoprotein enhances monocyte adhesion to endothelial cells in vitro. The activation of phospholipase A2 (PLA2) is also important in the oxidation of low-density lipoprotein by endothelial cells. In this study, we investigated the role of PLA2 activation in the adhesion of a leukemic monocyte cell line (THP-1 cells) to endothelial cells in vitro using an adhesion assay and a cell-ELISA technique. The treatment of human umbilical-cord-vein endothelial cells with PLA2 stimulators such as interleukin-1 beta, tumor necrosis factor and lipopolysaccharide all increased the adhesion of THP-1 cells to endothelial cells. Exogenous PLA2 also increased the adhesion of these cell types. The increased adhesion induced by these PLA2 stimulators, as well as PLA2 itself, was reversed by various inhibitors of the PLA2 reaction. A product of the PLA2 reaction, lysophosphatidylcholine, also increased cell adhesion. A cell-ELISA technique showed the enhanced expression of vascular-cell-adhesion-molecule 1 and intercellular-adhesion-molecule 1 to endothelial cells after treatment with PLA2 stimulators, PLA2 or lysophosphatidylcholine. These results suggest that the PLA2 reaction enhances monocyte adhesion to endothelial cells through the expression of cellular adhesion molecules.

Cell Adhesion↗
PubMed2002

Expression of leukocyte-endothelial cell adhesion molecules on monocyte adhesion to human endothelial cells on plasma treated PET and PTFE in vitro.

We used a coculture model to evaluate the inflammatory potential of ammonia gas plasma modified PET and PTFE by flow cytometry and immunohistochemistry. In these studies, human endothelial cells from umbilical cord (HUVEC) and promonocytic U937 cells were used. HUVECs grown on polystyrene tissue culture coverslips and HUVECs stimulated with tumour necrosis factor (TNF-alpha) were used as controls. U937 adhesion to endothelium on each surface was evaluated at day 1 and day 7. To further investigate the role of leukocyte-endothelial cell adhesion molecules (CAMs) in cell-to-cell interaction on material surfaces, the expression of the leukocyte-endothelial CAMs: ICAM-1, VCAM-1, PECAM-1, and E-selectin on HUVECs were evaluated after U937 cell adhesion. The results demonstrated that plasma treated PET (T-PET) and treated PTFE (T-PTFE) did not increase U937 cell adhesion compared to the negative control. Maximal adhesion of U937 cells to HUVEC was observed on TNF-alpha stimulated endothelium with significant differences between day 1 and day 7, which is consistent with our prior observation that T-PET and T-PTFE did not cause HUVECs to increase the expression of adhesion molecules. After U937 cell adhesion, the expression of ICAM-1 and VCAM-1 of HUVECs were not different on T-PET and T-PTFE compared with the negative control. However, the expression of E-selectin was reduced on day 1, but not on day 7. The effects of plasma treated PET and PTFE on HUVEC adhesion and proliferation were also studied. On day 1 there were slight increases in the growth of HUVECs on both of T-PET and T-PTFE but this was not statistically significant. On day 7, the cell number increased significantly on the surfaces compared to the negative control. The results demonstrate that the plasma treatment of PET and PTFE with ammonia improves the adhesion and growth of endothelial cells and these surfaces do not exhibit a direct inflammatory effect in terms of monocyte adhesion and expression of leukocyte-endothelial CAMs. The monocyte adhesion to endothelial cells on surfaces can be used as a tool for the evaluation of material surface modification and further to study the mechanisms of cell-to-cell interactions in response to surfaces.

Biocompatible Materials↗
PubMed1996

Inhibition of focal adhesion kinase (FAK) signaling in focal adhesions decreases cell motility and proliferation.

It has been proposed that the focal adhesion kinase (FAK) mediates focal adhesion formation through tyrosine phosphorylation during cell adhesion. We investigated the role of FAK in focal adhesion structure and function. Loading cells with a glutathione-S-transferase fusion protein (GST-Cterm) containing the FAK focal adhesion targeting sequence, but not the kinase domain, decreased the association of endogenous FAK with focal adhesions. This displacement of endogenous FAK in both BALB/c 3T3 cells and human umbilical vein endothelial cells loaded with GST-Cterm decreased focal adhesion phosphotyrosine content. Neither cell type, however, exhibited a reduction in focal adhesions after GST-Cterm loading. These results indicate that FAK mediates adhesion-associated tyrosine phosphorylation, but not the formation of focal adhesions. We then examined the effect of inhibiting FAK function on other adhesion-dependent cell behavior. Cells microinjected with GST-Cterm exhibited decreased migration. In addition, cells injected with GST-Cterm had decreased DNA synthesis compared with control-injected or noninjected cells. These findings suggest that FAK functions in the regulation of cell migration and cell proliferation.

3T3 Cells↗
PubMed1998

Rapid adhesion and spread of non-adherent colon cancer Colo201 cells induced by the protein kinase inhibitors, K252a and KT5720 and suppression of the adhesion by the immunosuppressants FK506 and cyclosporin A.

We examined alterations in cell morphology and expression of adhesion molecules in response to a general protein kinase inhibitor K252a treatment of non-adherent colon adenocarcinoma Colo201 cells. K252a induced rapid cell adhesion and spreading with concomitant formation of actin stress fibers. A protein kinase A inhibitor KT5720 also induced cell adhesion, but the rate of spread was slower than that seen with K252a. These adhesions were mediated by integrin molecules since cell adhesion required Mg2+, Mn2+ or Ca2+, and was inhibited by monoclonal antibodies for integrins alpha2 and beta1. Indirect immunofluorescence microscopic observations revealed that integrin alpha2 and beta1 molecules in K252a-treated cells were concentrated at sites of focal adhesion, but expressions of integrin molecules were not modulated. Tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin increased during K252a- or KT5720-induced cell adhesion. Immunosuppressants FK506 and cyclosporin A suppressed the K252a-induced cell adhesion and abolished tyrosine phosphorylation of cellular proteins including FAK and paxillin. Furthermore, W7 and calmidazolium, inhibitors of calmodulin, also inhibited the cell adhesion. Based on findings that FK506 and cyclosporin A are inhibitors of the calcium calmodulin-dependent protein phosphatase, calcineurin, this phosphatase may regulate integrin-dependent cell adhesion and spread of Colo201 cells. This Colo201 cell model provides a pertinent system for studying molecules involved in signal transduction pathways and can shed light on mechanisms of metastasis and invasion of colon carcinoma cells.

Adenocarcinoma↗
PubMed2000

Lateral clustering of cadherin-4 without homophilic interaction: possible involvement in the concentration process at cell-cell adhesion sites as well as in the cell adhesion activity.

It is thought that the concentration of classic cadherins at cell-cell adhesion sites is essential for generating strong cell-cell adhesion activity, but the mechanism is not well understood. To clarify the structural basis of the concentration process and the cell adhesion activity, we constructed various mutants of cadherin-4 and examined the adhesion properties of the transfectants. A deletion mutant lacking the entire cytoplasmic domain had weak, but significant Ca(2+)-dependent cell adhesion activity. Interestingly, the deletion mutant showed intrinsic cluster formation in the absence of cell-cell adhesion, possible lateral cluster formation. The cytoplasmic domain-deleted cadherin-4 containing the mutation of Trp-2 to Ala, which is known to inhibit the strand dimer formation required for the cell-cell adhesion, retained the possible activity of lateral cluster formation, supporting this notion. These results suggest that the extracellular domain has intrinsic activity of lateral cluster formation. Indeed, deletion of a cadherin repeat in the extracellular domain significantly reduced or abolished the lateral cluster formation as well as the concentration of cadherin-4 at cell-cell contact sites and cell adhesion activity. When transfectants of the cytoplasmic domain-deleted cadherin-4 made cell-cell contact and formed intimate cell-cell adhesion, the lateral clusters of cadherin-4 initially gathered at cell-cell contact sites, and a smooth linear concentration was gradually formed along the cell-cell adhesion interface. The results suggest that the lateral cluster formation is involved in the concentration process of cadherin-4 at cell-cell adhesion sites, hence in the strong cell adhesion activity of cadherin-4 as well.

Amino Acid Substitution↗
PubMed1985

Hepatocyte adhesion on plastic. Different mechanisms for serum- and fibronectin-mediated adhesion.

Hepatocytes adhere well on plastic in the presence of serum or fibronectin and subsequent spreading is not prevented when protein synthesis was blocked by cycloheximide. Protein synthesis-independent spreading was also observed in cultures containing serum depleted of fibronectin by affinity chromatography. This indicates that serum-mediated adhesion is independent of fibronectin and suggests the existence of an adhesion factor other than fibronectin in serum. The involvement of different membrane components for fibronectin- and serum-mediated adhesion was demonstrated by experiments where the different adhesion-inhibiting activities of antisera raised against plasma membranes of rat liver and Morris hepatoma 7777 (Neumeier et al., FEBS lett 168 (1984) 241-244) were used. Whereas anti-liver antibodies inhibited both types of adhesion, anti-hepatoma antibodies were only able to prevent fibronectin-mediated adhesion. This indicates again that two different mechanisms are responsible for fibronectin- and serum-mediated adhesion. Fractionation of fetal calf serum (FCS) by size exclusion HPLC revealed that proteins of molecular weights of 60-80 kD promoted attachment and spreading of hepatocytes. Spreading was not perturbated by anti-hepatoma antibodies, indicating that an adhesion factor of 60-80 kD is responsible for serum-mediated adhesion. 'Serum-spreading factor', also called vitronectin, from human plasma has been described as having a similar molecular weight. The purified factor was found to mediate hepatocyte adhesion which was not inhibited by anti-hepatoma antibodies. This suggests that serum-mediated adhesion depends on an adhesion factor present in FCS, which is similar to or identical with vitronectin.

Animals↗
PubMed2005

Extension of a one-step self-etch adhesive into a multi-step adhesive.

UNLABELLED: One-step self-etch adhesives are undoubtedly the most user-friendly adhesives, but have been associated with lower bonding effectiveness as compared to two-step and three-step adhesives. Conversion of a one-step self-etch system into a two-step self-etch adhesive by adding a bonding step, or into a three-step etch&rinse adhesive by adding a beforehand etching step and a bonding step might be tempting in order to improve bond strength. OBJECTIVES: The objective of this study was to investigate whether adding application steps influences the bond strength of a one-step self-etch adhesive. METHODS: In this study, the bonding effectiveness of two experimental one-step self-etch adhesives and three different commercial adhesives to enamel and dentin was determined using a micro-tensile bond-strength protocol. This procedure was repeated for the experimental adhesives transformed into two-step self-etch and three-step etch&rinse adhesives. In addition, their interaction with tooth tissue was investigated using TEM and Feg-SEM. RESULTS: Transforming a one-step into a two-step self-etch adhesive did improve the bond strength to enamel and dentin, though not significantly. By adding a preceding etching step, the bond strength to enamel was significantly improved, but that to dentin was decreased considerably. The latter must be attributed to hampered resin infiltration of the one-step self-etch adhesive within the relatively deeply exposed collagen fibril network. SIGNIFICANCE: Additional application of a hydrophobic bonding agent slightly improved bonding effectiveness. Adding a preceding etching step is beneficial for enamel but should be avoided for dentin as this will decrease bond strengths, and may even jeopardize the bonding durability.

Acetone↗
PubMed1994

Identification of epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor in surgically induced pelvic adhesions in the rat and intraperitoneal adhesions in the human.

OBJECTIVE: Our purpose was to determine the presence and cellular distribution of epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor in surgically induced pelvic fibrous adhesions in rat uterine horns subjected to burn, crush, and debridement injury and intraperitoneal fibrous adhesions formed to various organs in the human. STUDY DESIGN: A total of 15 injured and five uninjured rats were used in this study, and fibrous adhesions and intact peritoneum were removed for processing 2 weeks after surgery. Fibrous adhesions formed to uterine, ovarian, and oviductal tissues and the peritoneal wall from eight patients who had gynecologic surgery were also collected. The tissues were processed for immunohistochemical localization of epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor with specific antibodies to human and rat epidermal growth factor and transforming growth factor-alpha and the extracellular binding domain of the epidermal growth factor receptor. RESULTS: All the cell types in the rat fibrous adhesion immunostained for epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor. The highest immunostaining intensity for epidermal growth factor was associated with inflammatory cells infiltrated into the fibrous adhesion, followed by arteriole endothelial and smooth muscle cells, fascial striated muscle, and fibroblasts of the fibrous adhesion. In the uterine tissue at the site of injuries myometrial smooth muscle cells, in addition to inflammatory cells that migrated among stromal cells, also immunostained for epidermal growth factor. Fibrous adhesions also immunostained for transforming growth factor-alpha with three separate polyclonal antibodies to the amino and carboxy termini of transforming growth factor-alpha precursor and the mature transforming growth factor-alpha, with no substantial differences in their intensity and pattern compared with epidermal growth factor. The pattern and cellular distribution of epidermal growth factor receptor was similar to that seen for epidermal growth factor and transforming growth factor-alpha. Fibrous adhesions from patients with intraperitoneal adhesions immunostained for epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor with a pattern and intensity similar to that observed in fibrous adhesions in the rats. CONCLUSIONS: The data suggest that epidermal growth factor and transforming growth factor-alpha may play a key role both in normal mechanism of peritoneal repair after injury and formation and maintenance of fibrous adhesions.

Animals↗
PubMed1998

The rates of adhesion development and the effects of crystalloid solutions on adhesion development in pelvic surgery.

OBJECTIVE: To document rates of adhesion development after abdomino-pelvic surgery, stratified by adhesion type, access method, and use of crystalloid solution instillates. DESIGN: Reports from a MEDLINE search (1/1/1966-12/18/1996) detailing rates of adhesion development and meeting the inclusion criteria were subjected to meta-analysis. SETTING: Meta-analysis. PATIENT(S): Patients undergoing abdomino-pelvic surgery. INTERVENTION(S): Intraperitoneal crystalloid solution instillates. MAIN OUTCOME MEASURE(S): Percentage adhesion-free outcome in patients ("patients") or surgical sites ("sites"). RESULT(S): Adhesion-free outcome (sites) was lowest for reformed (26.3% laparotomy; 14.3% laparoscopy), higher for de novo 1b (direct trauma) (45.2% laparotomy, 37.2% laparoscopy), and highest for de novo 1a (indirect trauma) adhesions (82.4% laparoscopy). Crystalloid solution instillates reduced adhesion-free outcome at sites (45.2% versus 20% de novo 1b adhesions in laparotomy) and in patients (43.5% versus 19.9% reformed, laparotomy; 71.7% versus 25% de novo 1b, laparoscopy). CONCLUSION(S): Adhesion-free outcome was lowest for reformed, higher for de novo 1b, and highest for de novo 1a adhesions. Surprisingly, it was lower in laparoscopy than in laparotomy for de novo 1b and reformed adhesions. Crystalloid instillates did not increase adhesion-free outcome. Although limited by the retrospective and heterogeneous nature of the data, these conclusions nonetheless provide a basis on which to formulate future hypotheses.

Crystallization↗
PubMed1992

Cell adhesion in a dynamic flow system as compared to static system. Glycosphingolipid-glycosphingolipid interaction in the dynamic system predominates over lectin- or integrin-based mechanisms in adhesion of B16 melanoma cells to non-activated endothelial cells.

Initial adhesion of B16 melanoma variants to non-activated endothelial cells is mediated through specific interaction between GM3 (NeuAc alpha 2----3Gal beta 1----4Glc beta 1----Cer) expressed on melanoma cells and lactosylceramide (LacCer, Gal beta 1----4Glc beta 1----Cer) expressed on endothelial cells. This adhesion is predominant over integrin- or lectin-mediated adhesion in a dynamic flow experimental system employing a parallel plate laminar flow chamber (Lawrence, M. B., Smith, C. W., Eskin, S. G., and McIntire, L. V. (1990) Blood 75, 227-237). In this system, a tumor cell suspension flows over a glass plate coated with glycosphingolipid, lectin, or fibronectin, and adhesion is recorded on videotape. These conditions were designed to mimic the microvascular environment in which tumor metastatic deposition takes place. In contrast, lectin- and fibronectin-based mechanisms are predominant in previously used static adhesion systems. Under static conditions, the relative degree of adhesion of the four B16 variants to endothelial cells or to LacCer-coated plates was the same as their relative degree of GM3 expression (i.e. BL6 approximately F10 greater than F1 greater than WA4), and adhesion was inhibited in the presence of methyl-beta-lactoside, or liposomes containing LacCer or GM3. Adhesion was also inhibited by pretreatment of B16 cells with anti-GM3 antibody DH2 or sialidase and by pretreatment of endothelial cells with anti-LacCer antibody T5A7. Under dynamic flow conditions, WA4 cells did not adhere to mouse endothelial cells at high shear stress (greater than 2.5 dynes/cm2) but did adhere at lower shear stress. In contrast, BL6 and F10 cells adhered strongly at both low and high shear stress. BL6 cell adhesion to endothelial cells at both low and high shear stress was inhibited in the presence of antibody DH2, ethyl-beta-lactoside, or lactose, as well as by pretreatment of BL6 cells with sialidase. Thus, some clear differences, as well as similarities, in cell adhesion under static versus dynamic conditions are demonstrated. These findings suggest that melanoma cell adhesion to endothelial cells, based on GM3/LacCer interaction, initiates metastatic deposition, which may trigger a series of "cascade" reactions leading to activation of endothelial cells and expression of Ig family or selectin receptors, thereby promoting adhesion and migration of tumor cells.

Animals↗
PubMed1994

Adhesion of committed human hematopoietic progenitors to synthetic peptides from the C-terminal heparin-binding domain of fibronectin: cooperation between the integrin alpha 4 beta 1 and the CD44 adhesion receptor.

Close interaction of human hematopoietic progenitors with the bone marrow microenvironment is important for the ordered progression of human hematopoiesis. Progenitor cell adhesion to stroma has a complex molecular basis, involving various cell-extracellular matrix and cell-cell interactions. We have previously shown that adhesion of colony-forming cells (CFC) to fibronectin, present in stromal extracellular matrix, involves multiple sites, including two heparin-binding synthetic peptides (FN-C/H I and FN-C/H II) and the alpha 4 beta 1 integrin-binding peptide CS1. These synthetic peptides are located in close proximity in the type III repeat 14 and the immediately adjacent type IIIcs region of fibronectin. In the current study, we evaluate receptors expressed by CFC responsible for their adhesion to fibronectin. We show that the alpha 4 beta 1 integrin mediates adhesion to CFC to the peptides FN-C/H I and CS1. Adhesion of CFC to fibronectin is also mediated by proteoglycans, because removal of cell surface chondroitin-sulfate proteoglycans resulted in decreased adhesion of CFC to FN-C/ I and FN-C/H II. The core protein of this proteoglycan was identified by immunoprecipitation as a 90-kD member of the CD44 group of adhesion molecules. Interestingly, although the proteoglycan core protein failed to adhere to FN-C/H II affinity columns, anti-CD44 monoclonal antibodies blocked CFC adhesion to FN-C/H II, indicating that these monoclonal antibodies may interfere with core protein-mediated intracellular signalling. Finally, we show that CD44 and alpha 4 beta 1 may cooperate in establishing progenitor adhesion, because anti-CD44 antibodies potentiated the adhesion-inhibitory effects of suboptimal concentrations of anti-alpha 4 or anti-beta 1 monoclonal antibodies. These results provide a working model for progenitor cell recognition of fibronectin (and possibly the marrow micro-environment) in which the coordinated action of integrins and cell surface proteoglycans is necessary for cell adhesion. This model can now be used to study the complex relationship between progenitor cell adhesion and the regulation of their proliferation and differentiation.

Amino Acid Sequence↗
PubMed2000

C3a and C5a enhance granulocyte adhesion to endothelial and epithelial cell monolayers: epithelial and endothelial priming is required for C3a-induced eosinophil adhesion.

Effects of the anaphylatoxins C3a and C5a on eosinophil and neutrophil adhesion to HUVEC and to primary culture human bronchial epithelial cells (HBEC) were investigated. Activities on both leukocytes and on structural cells were examined. C3a upregulated beta2 integrin expression and caused shedding of L-selectin on eosinophils, but had no effect on neutrophil adhesion molecule expression. C5a upregulated beta2 integrins and caused shedding of L-selectin on both eosinophils and neutrophils. The potency of C5a was equivalent on both cell types; however, the magnitude of the changes in each of these adhesion molecules was significantly greater in neutrophils than eosinophils. Neither C3a nor C5a altered expression of ICAM-1, VCAM-1, E-selectin or P-selectin on either HUVEC or HBEC. C5a induced adhesion of both neutrophils and eosinophils to unstimulated HUVEC or HBEC, and adhesion was further enhanced when HUVEC and HBEC were "primed" with TNF-alpha and IFN-gamma, respectively. C3a failed to enhance adhesion of either eosinophils or neutrophils to unprimed HUVEC or HBEC, and enhanced only eosinophil adhesion to cytokine-primed HUVEC or HBEC. Similar to C3a, C3a(desArg) and a C3a-analog peptide E7 also enhanced eosinophil adhesion only to cytokine-primed HUVEC and HBEC. These results support the traditional view of anaphylatoxins as leukocyte-specific mediators. The specificity of C3a for eosinophils implicates this molecule as a potential participant in allergic inflammation. The pro-adhesive effects of C3a(desArg) suggest that this molecule, previously characterized as a spasmogenically inactive derivative of C3a, may also alter leukocyte dynamics and migration. Finally, activation of endothelium may represent an important control mechanism for C3a-mediated adhesion preventing unchecked eosinophil adhesion to uninflamed systemic vasculature.

CD18 Antigens↗
PubMed2004

Transforming growth factor beta regulates cell-cell adhesion through extracellular matrix remodeling and activation of focal adhesion kinase in human colon carcinoma Moser cells.

Transforming growth factor (TGF) beta is a potent regulator of cell-matrix and cell-cell adhesions (collectively termed cellular adhesions). Cellular adhesions play crucial roles in controlling the differentiation of epithelial cells and in maintaining the integrity of the epithelium. Loss of TGF beta-responsiveness is thought to be an important early initiating event in the malignant progression of epithelial cancer. In the TGFbeta-responsive human colon adenocarcinoma Moser cells, TGFbeta promotes cellular adhesions and suppresses their malignant phenotype. TGFbeta promotes cell-matrix adhesion by inducing the synthesis of extracellular matrix (ECM) adhesion molecules and the expression of integrin receptors for these molecules (termed ECM remodeling). TGFbeta promotes cell-cell adhesion through the induction of E-cadherin expression, an epithelial associated homotypic cell-cell adhesion molecule, which also functions as a tumor suppressor in colon cancer. How TGFbeta regulates E-cadherin expression is not known. In this study, we showed that the induction of E-cadherin by TGFbeta was mediated through the activation of focal adhesion kinase (FAK), a major signaling molecule in focal adhesion contacts and that the activation of FAK was due to ECM remodeling and increased cell-matrix interactions. Thus, TGFbeta regulates cell-cell adhesion through its ability to remodel the ECM and to activate FAK through ECM remodeling.

Adenocarcinoma↗
PubMed2004

Pressure activates colon cancer cell adhesion by inside-out focal adhesion complex and actin cytoskeletal signaling.

BACKGROUND AND AIMS: Few circulating tumor cells implant or cause metastasis. We hypothesized that venous or lymphatic pressure or iatrogenic pressure during resection activates signals governing malignant colonocyte adhesion. METHODS: We studied the effect of 15 mm Hg increased pressure for 30 minutes on adhesion of primary human colon cancer cells and SW620 colonocytes to collagen and endothelial cells. We modulated integrin affinity with extracellular cations. We assessed binding affinity by detachment assay; integrin surface expression by flow cytometry; and focal adhesion kinase (FAK), Src, and extracellular signal-regulated kinase (ERK) activation by Western analysis and Src in vitro kinase assay. We inhibited Src (PP2), FAK (small RNA interference, SiRNA, or FRNK transfection), MEK (PD98059), PKC (calphostin C), and actin destabilization (phalloidin). RESULTS: Pressure and manganese stimulated primary and SW620 colonocyte adhesion to collagen. Pressure also stimulated SW620 adhesion to endothelial monolayers. Pressure strengthened SW620 binding force to matrix without changing integrin surface expression. Pressure activated SW620 FAK and Src, but not ERK. Manganese did not. Calcium-inhibited adhesion but stimulated FAK (but not Src). PP2 prevented pressure activation of Src, Src phosphorylation of FAK576, and pressure-stimulated adhesion but not FAK397 autophosphorylation. FRNK transfection or FAK SiRNA also prevented pressure-stimulated adhesion. FAK SiRNA ablated pressure-activated FAK397, Src, and FAK576 phosphorylation. Neither Src nor FAK inhibition blocked cation effects. Phalloidin prevented pressure-stimulated adhesion. PD98059 or calphostin C did not. CONCLUSIONS: In contrast to divalent cations, extracellular pressure may increase integrin affinity and promote colon cancer adhesion via actin dependent inside-out FAK and Src signals. This mechanotransduced pathway may regulate metastasizing tumor cell adhesion.

Actins↗
PubMed1996

Identification of LIM3 as the principal determinant of paxillin focal adhesion localization and characterization of a novel motif on paxillin directing vinculin and focal adhesion kinase binding.

Paxillin is a 68-kD focal adhesion phosphoprotein that interacts with several proteins including members of the src family of tyrosine kinases, the transforming protein v-crk, and the cytoskeletal proteins vinculin and the tyrosine kinase, focal adhesion kinase (FAK). This suggests a function for paxillin as a molecular adaptor, responsible for the recruitment of structural and signaling molecules to focal adhesions. The current study defines the vinculin- and FAK-interaction domains on paxillin and identifies the principal paxillin focal adhesion targeting motif. Using truncation and deletion mutagenesis, we have localized the vinculin-binding site on paxillin to a contiguous stretch of 21 amino acids spanning residues 143-164. In contrast, maximal binding of FAK to paxillin requires, in addition to the region of paxillin spanning amino acids 143-164, a carboxyl-terminal domain encompassing residues 265-313. These data demonstrate the presence of a single binding site for vinculin, and at least two binding sites for FAK that are separated by an intervening stretch of 100 amino acids. Vinculin- and FAK-binding activities within amino acids 143-164 were separable since mutation of amino acid 151 from a negatively charged glutamic acid to the uncharged polar residue glutamine (E151Q) reduced binding of vinculin to paxillin by >90%, with no reduction in the binding capacity for FAK. The requirement for focal adhesion targeting of the vinculin- and FAK-binding regions within paxillin was determined by transfection into CHO.K1 fibroblasts. Significantly and surprisingly, paxillin constructs containing both deletion and point mutations that abrogate binding of FAK and/or vinculin were found to target effectively to focal adhesions. Additionally, expression of the amino-terminal 313 amino acids of paxillin containing intact vinculin- and FAK-binding domains failed to target to focal adhesions. This indicated other regions of paxillin were functioning as focal adhesion localization motifs. The carboxyl-terminal half of paxillin (amino acids 313-559) contains four contiguous double zinc finger LIM domains. Transfection analyses of sequential carboxyl-terminal truncations of the four individual LIM motifs and site-directed mutagenesis of LIM domains 1, 2, and 3, as well as deletion mutagenesis, revealed that the principal mechanism of targeting paxillin to focal adhesions is through LIM3. These data demonstrate that paxillin localizes to focal adhesions independent of interactions with vinculin and/or FAK, and represents the first definitive demonstration of LIM domains functioning as a primary determinant of protein subcellular localization to focal adhesions.

Animals↗
PubMed2003

Absence of adhesion triggers differential FAK and SAPKp38 signals in SW620 human colon cancer cells that may inhibit adhesiveness and lead to cell death.

BACKGROUND: Upon adhesion, anchorage-dependent cells transmit survival signals from the matrix into the cell. Loss of anchorage leads to anoikis. Resistance to anoikis may influence tumor progression and metastasis. To better understand the pathways that regulate the choice between adhesion and cell death, we examined FAK, c-Src andMAPKinase activities in SW620 human colon cancer cells. METHODS: SW620 cell suspensions were first allowed to adhere to collagen I for 30 minutes and adherent cells were subsequently counted. FAK, p38, c-Src and ERK1/2 phosphorylation were assessed by Western blot in adherent cells and in cells prevented from adhesion by plating unto BSA-pacificated dishes. p38 and FAK were inhibited by SB203580 (20 microM) or by specific FAK antisense nucleotides or FAK siRNA, respectively, and adhesion quantitated. Apoptosis (anoikis) after lack of adhesion was measured colorimetrically in control cells and in cells treated with SB203580. RESULTS: Adhesion to collagen I nearly doubled FAK phosphorylation at Y397, the autophosphorylation site, and decreased p38 activation by 60% (p<0.001) but did not affect FAK phosphorylation at Y576, the c-Src dependent site. Lowering FAK expression with FAK antisense decreased adhesion to collagen I; the larger decrease in FAK expression obtained with the siRNA (43 +/- 2%) resulted in significantly greater inhibition of adhesion not only to collagen I but also to collagen IV and fibronectin. The p38 inhibitor diminished anoikis and enhanced adhesion. Interestingly, the SB compound also significantly inhibited FAK phosphorylation at Y397 (23 +/- 3% in adherent, 30 +/- 4% in non-adherent cells at 30 minutes and 35 +/- 4% in adherent, 46 +/- 14% in non-adherent cells after 6 hours, p<0.05 for each) and greatly enhanced phosphorylation of ERK1/2, a putative anti-apoptotic component of the MAPK cascade. CONCLUSIONS: In the absence of adhesion, SW620 cells exhibit increased p38 but decreased FAK activation, signals that may promote cell death. Our observations with the p38 inhibitor SB203580 indicate that inside-out signals, from p38 to FAK, may regulate both adhesion and anoikis in SW620 cells. In addition, the data suggest the presence of cross-talk between the pro-apoptotic p38 and anti-apoptotic ERK1/2 pathways.

Apoptosis↗