Inhibition of neutrophil chemokinesis on vitronectin by inhibitors of calcineurin

REPS2 downregulation facilitates FGF-induced adhesion and migration in human lens epithelial cells through FAK/Cdc42 signaling and contributes to posterior capsule opacification

Posterior capsular opacification (PCO) can cause postoperative visual loss after cataract surgery. Residual human lens epithelial cell (HLEC) proliferation, migration, epithelial-mesenchymal transition (EMT) and synthesis of extracellular matrix (ECM) are the entitative reasons for PCO. Low expression of Ral-binding protein 1-associated Eps domain-containing 2 (REPS2) and high levels of basic fibroblast growth factor (b-FGF) were observed in the lens and postoperative aqueous humor of cataract patients. REPS2 was identified as a negative regulator in growth factor signaling; however, its function in HLECs is unknown. This was first investigated in the present study by evaluating REPS2 expression in anterior lens capsules from cataract patients, a mouse cataract model, and HLE-b3 cells. The biological function of REPS2 in HLE-B3 cells was assessed by REPS2 silencing and Cell Counting Kit 8, wound healing, Transwell migration, F-actin staining, G-protein pulldown and western blot assays. In the present study, REPS2 was significantly downregulated in human and mouse cataract capsules and H₂O₂-treated HLE-B3 cells. REPS2 knockdown increased fibronectin, type I collagen, and α-smooth muscle actin expression levels and stimulated HLECs proliferation and migration; these effects were enhanced by FGF treatment and accompanied with focal adhesion kinase (FAK) phosphorylation, cell division cycle 42 (Cdc42) activation, focal adhesion protein upregulation, and F-actin cytoskeleton reorganization. However, treatment with the FAK inhibitor PF573228 abolished these effects. Thus, REPS2 downregulation in cataract HLECs induces their proliferation and facilitates FGF-induced ECM synthesis, EMT, cell adhesion and migration by activating FAK/Cdc42 signaling, which may underlie PCO pathogenesis.

Carabin Deficiency Aggravates Hepatic Ischemia-Reperfusion Injury Through Promoting Neutrophil Trafficking via Ras and Calcineurin Signaling

Neutrophil infiltration plays an important role in the initial phase of hepatic ischemia and reperfusion injury (HIRI). Despite many different key molecules that have been reported to meditate neutrophil trafficking in HIRI, the mechanism of this process has not been fully elucidated. In this study, we found that Carabin deficiency in myeloid cells (LysMCre : Carabinfl/fl) aggravated IRI-induced hepatic injury and apoptosis through increasing the infiltration of CD11b⁺Ly6G⁺ neutrophils. ImmGen Datasets further revealed that Carabin was expressed in bone marrow neutrophils (GM.BM) but was significantly downregulated in thio-induced peripheral neutrophils (GN.Thio.PC), which was consistently verified by comparing GM.BM and liver-infiltrating neutrophils induced by IRI. Mechanistically, up-regulation of Carabin in GM.BM in vitro reduced the expression levels of P-selectin, E-selectin, and αvβ3 integrin through inhibiting Ras-ERK and Calcineurin-NFAT signaling. Furthermore, blocking P-selectin, E-selectin, and αvβ3 integrin in LysMCre : Carabinfl/fl mice decreased the frequency and number of CD11b⁺Ly6G⁺ neutrophils and reversed hepatic ischemia−reperfusion damage. In conclusion, our results provide a new understanding of Carabin, such that it is expressed and functions not only in adaptive immune cells (T and B cells) but also in innate immune cells (neutrophils), contributing to the migration of neutrophils. These findings provide novel and promising therapeutic targets for the prevention of HIRI during liver transplantation or hepatic surgery.

The Role of Calmodulin in Tumor Cell Migration, Invasiveness, and Metastasis

Calmodulin (CaM) is the principal Ca²⁺ sensor protein in all eukaryotic cells, that upon binding to target proteins transduces signals encoded by global or subcellular-specific changes of Ca²⁺ concentration within the cell. The Ca²⁺/CaM complex as well as Ca²⁺-free CaM modulate the activity of a vast number of enzymes, channels, signaling, adaptor and structural proteins, and hence the functionality of implicated signaling pathways, which control multiple cellular functions. A basic and important cellular function controlled by CaM in various ways is cell motility. Here we discuss the role of CaM-dependent systems involved in cell migration, tumor cell invasiveness, and metastasis development. Emphasis is given to phosphorylation/dephosphorylation events catalyzed by myosin light-chain kinase, CaM-dependent kinase-II, as well as other CaM-dependent kinases, and the CaM-dependent phosphatase calcineurin. In addition, the role of the CaM-regulated small GTPases Rac1 and Cdc42 (cell division cycle protein 42) as well as CaM-binding adaptor/scaffold proteins such as Grb7 (growth factor receptor bound protein 7), IQGAP (IQ motif containing GTPase activating protein) and AKAP12 (A kinase anchoring protein 12) will be reviewed. CaM-regulated mechanisms in cancer cells responsible for their greater migratory capacity compared to non-malignant cells, invasion of adjacent normal tissues and their systemic dissemination will be discussed, including closely linked processes such as the epithelial–mesenchymal transition and the activation of metalloproteases. This review covers as well the role of CaM in establishing metastatic foci in distant organs. Finally, the use of CaM antagonists and other blocking techniques to downregulate CaM-dependent systems aimed at preventing cancer cell invasiveness and metastasis development will be outlined.

Mitochondrial permeability transition pore is involved in oxidative burst and NETosis of human neutrophils

Neutrophils release neutrophil extracellular traps (NETs) in response to numerous pathogenic microbes as the last suicidal resource (NETosis) in the fight against infection. Apart from the host defense function, NETs play an essential role in the pathogenesis of various autoimmune and inflammatory diseases. Therefore, understanding the molecular mechanisms of NETosis is important for regulating aberrant NET release. The initiation of NETosis after the recognition of pathogens by specific receptors is mediated by an increase in intracellular Ca²⁺ concentration, therefore, the use of Ca²⁺ ionophore A23187 can be considered a semi-physiological model of NETosis. Induction of NETosis by various stimuli depends on reactive oxygen species (ROS) produced by NADPH oxidase, however, NETosis induced by Ca²⁺ ionophores was suggested to be mediated by ROS produced in mitochondria (mtROS). Using the mitochondria-targeted antioxidant SkQ1 and specific inhibitors of NADPH oxidase, we showed that both sources of ROS, mitochondria and NADPH oxidase, are involved in NETosis induced by A23187 in human neutrophils. In support of the critical role of mtROS, SkQ1-sensitive NETosis was demonstrated to be induced by A23187 in neutrophils from patients with chronic granulomatous disease (CGD). We assume that Ca²⁺-triggered mtROS production contributes to NETosis either directly (CGD neutrophils) or by stimulating NADPH oxidase. The opening of the mitochondrial permeability transition pore (mPTP) in neutrophils treated by A23187 was revealed using the electron transmission microscopy as a swelling of the mitochondrial matrix. Using specific inhibitors, we demonstrated that the mPTP is involved in mtROS production, NETosis, and the oxidative burst induced by A23187.

Surface Area to Volume Ratio of Electrospun Polydioxanone Templates Regulates the Adsorption of Soluble Proteins from Human Serum

Neutrophils, the first cells that interact with surface-adsorbed proteins on biomaterials, have been increasingly recognized as critical maestros in the foreign body response for guided tissue regeneration. Recent research has shown that small diameter (SD) fibers of electrospun tissue regeneration templates, which have a high surface area to volume ratio (SAVR), enhance the release of neutrophil extracellular traps (NETs) compared to large diameter (LD) fibers, resulting in impaired tissue regeneration. In this study, we evaluated the adsorption of eight human serum proteins on the surface of electrospun templates to investigate how protein adsorption may regulate the release of NETs. Electrospun polydioxanone templates made from SD fibers with high SAVR and LD fibers with low SAVR, were incubated with 0.2% human serum and in situ protein adsorption was quantified with infrared-based immunodetection. Of the detected proteins, IgM and vitronectin adsorbed at low levels, suggesting that they do not play a central role in the release of NETs. Contrastingly, albumin and IgG adsorbed rapidly to the surface of the templates. One-hundred to 200 times more IgG adsorbed on the templates compared to albumin, with significantly greater adsorption occurring on the SD templates with high SAVR. Given that neutrophils express receptors that interact with IgG during phagocytosis and NET release, these results suggest that SAVR-dependent adsorption of IgG on the SD electrospun templates may contribute to the up-regulated release of NETs. Overall, this study may aid in the design of immunomodulatory biomaterials that regulate NET release and thus the potential for neutrophil-driven tissue regeneration.

Syntrophins entangled in cytoskeletal meshwork: Helping to hold it all together

Syntrophins are a family of 59 kDa peripheral membrane-associated adapter proteins, containing multiple protein-protein and protein-lipid interaction domains. The syntrophin family consists of five isoforms that exhibit specific tissue distribution, distinct sub-cellular localization and unique expression patterns implying their diverse functional roles. These syntrophin isoforms form multiple functional protein complexes and ensure proper localization of signalling proteins and their binding partners to specific membrane domains and provide appropriate spatiotemporal regulation of signalling pathways. Syntrophins consist of two PH domains, a PDZ domain and a conserved SU domain. The PH1 domain is split by the PDZ domain. The PH2 and the SU domain are involved in the interaction between syntrophin and the dystrophin-glycoprotein complex (DGC). Syntrophins recruit various signalling proteins to DGC and link extracellular matrix to internal signalling apparatus via DGC. The different domains of the syntrophin isoforms are responsible for modulation of cytoskeleton. Syntrophins associate with cytoskeletal proteins and lead to various cellular responses by modulating the cytoskeleton. Syntrophins are involved in many physiological processes which involve cytoskeletal reorganization like insulin secretion, blood pressure regulation, myogenesis, cell migration, formation and retraction of focal adhesions. Syntrophins have been implicated in various pathologies like Alzheimer's disease, muscular dystrophy, cancer. Their role in cytoskeletal organization and modulation makes them perfect candidates for further studies in various cancers and other ailments that involve cytoskeletal modulation. The role of syntrophins in cytoskeletal organization and modulation has not yet been comprehensively reviewed till now. This review focuses on syntrophins and highlights their role in cytoskeletal organization, modulation and dynamics via its involvement in different cell signalling networks.

Assessment of Neutrophil Chemotaxis Upon G-CSF Treatment of Healthy Stem Cell Donors and in Allogeneic Transplant Recipients

Neutrophils are crucial for the human innate immunity and constitute the majority of leukocytes in circulation. Thus, blood neutrophil counts serve as a measure for the immune system's functionality. Hematological patients often have low neutrophil counts due to disease or chemotherapy. To increase neutrophil counts and thereby preventing infections in high-risk patients, recombinant G-CSF is widely used as adjunct therapy to stimulate the maturation of neutrophils. In addition, G-CSF is utilized to recruit stem cells (SCs) into the peripheral blood of SC donors. Still, the actual functionality of neutrophils resulting from G-CSF treatment remains insufficiently understood. We tested the ex vivo functionality of neutrophils isolated from blood of G-CSF-treated healthy SC donors. We quantified chemotaxis, oxidative burst, and phagocytosis before and after treatment and detected significantly reduced chemotactic activity upon G-CSF treatment. Similarly, in vitro treatment of previously untreated neutrophils with G-CSF led to reduced chemotactic activity. In addition, we revealed that this effect persists in the allogeneic SC recipients up to 4 weeks after neutrophil engraftment. Our data indicates that neutrophil quantity, as a sole measure of immunocompetence in high-risk patients should be considered cautiously as neutrophil functionality might be affected by the primary treatment.

Extremely low frequency electromagnetic fields promote mesenchymal stem cell migration by increasing intracellular Ca2+ and activating the FAK/Rho GTPases signaling pathways in vitro

Background

The ability of mesenchymal stem cells (MSCs) to migrate to the desired tissues or lesions is crucial for stem cell-based regenerative medicine and tissue engineering. Optimal therapeutics for promoting MSC migration are expected to become an effective means for tissue regeneration. Electromagnetic fields (EMF), as a noninvasive therapy, can cause a lot of biological changes in MSCs. However, whether EMF can promote MSC migration has not yet been reported.

Methods

We evaluated the effects of EMF on cell migration in human bone marrow-derived MSCs. With the use of Helmholtz coils and an EMF stimulator, 7.5, 15, 30, 50, and 70 Hz/1 mT EMF was generated. Additionally, we employed the l-type calcium channel blocker verapamil and the focal adhesion kinase (FAK) inhibitor PF-573228 to investigate the role of intracellular calcium content, cell adhesion proteins, and the Rho GTPase protein family (RhoA, Rac1, and Cdc42) in EMF-mediated MSC migration. Cell adhesion proteins (FAK, talin, and vinculin) were detected by Western blot analysis. The Rho GTPase protein family activities were assessed by G-LISA, and F-actin levels, which reflect actin cytoskeletal organization, were detected using immunofluorescence.

Results

All the 7.5, 15, 30, 50, and 70 Hz/1 mT EMF promoted MSC migration. EMF increased MSC migration in an intracellular calcium-dependent manner. Notably, EMF-enhanced migration was mediated by FAK activation, which was critical for the formation of focal contacts, as evidenced by increased talin and vinculin expression. Moreover, RhoA, Rac1, and Cdc42 were activated by FAK to increase cytoskeletal organization, thus promoting cell contraction.

Conclusions

EMF promoted MSC migration by increasing intracellular calcium and activating the FAK/Rho GTPase signaling pathways. This study provides insights into the mechanisms of MSC migration and will enable the rational design of targeted therapies to improve MSC engraftment.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0883-4) contains supplementary material, which is available to authorized users.

Calcium oscillations in wounded fibroblast monolayers are spatially regulated through substrate mechanics

The maintenance of tissue integrity is essential for the life of multicellular organisms. Healing of a skin wound is a paradigm for how various cell types localize and repair tissue perturbations in an orchestrated fashion. To investigate biophysical mechanisms associated with wound localization, we focus on a model system consisting of a fibroblast monolayer on an elastic substrate. We find that the creation of an edge in the monolayer causes cytosolic calcium oscillations throughout the monolayer. The oscillation frequency increases with cell density, which shows that wound-induced calcium oscillations occur collectively. Inhibition of myosin II reduces the number of oscillating cells, demonstrating a coupling between actomyosin activity and calcium response. The spatial distribution of oscillating cells depends on the stiffness of the substrate. For soft substrates with a Young's modulus E ~ 360 Pa, oscillations occur on average within 0.2 mm distance from the wound edge. Increasing substrate stiffness leads to an average localization of oscillations away from the edge (up to ~0.6 mm). In addition, we use traction force microscopy to determine stresses between cells and substrate. We find that an increase of substrate rigidity leads to a higher traction magnitude. For E  <  ~2 kPa, the traction magnitude is strongly concentrated at the monolayer edge, while for E  >  ~8 kPa, traction magnitude is on average almost uniform beneath the monolayer. Thus, the spatial occurrence of calcium oscillations correlates with the cell-substrate traction. Overall, the experiments with fibroblasts demonstrate a collective, chemomechanical localization mechanism at the edge of a wound with a potential physiological role.

Conserved and Diverged Functions of the Calcineurin-Activated Prz1 Transcription Factor in Fission Yeast

Gene regulation in response to intracellular calcium is mediated by the calcineurin-activated transcription factor Prz1 in the fission yeast Schizosaccharomyces pombe Genome-wide studies of the Crz1 and CrzA fungal orthologs have uncovered numerous target genes involved in conserved and species-specific cellular processes. In contrast, very few target genes of Prz1 have been published. This article identifies an extensive list of genes using transcriptome and ChIP-chip analyses under inducing conditions of Prz1, including CaCl2 and tunicamycin treatment, as well as a ∆pmr1 genetic background. We identified 165 upregulated putative target genes of Prz1 in which the majority contained a calcium-dependent response element in their promoters, similar to that of the Saccharomyces cerevisiae ortholog Crz1 These genes were functionally enriched for Crz1-conserved processes such as cell-wall biosynthesis. Overexpression of prz1(+)increased resistance to the cell-wall degradation enzyme zymolyase, likely from upregulation of theO-mannosyltransferase encoding gene omh1(+) Loss of omh1(+)abrogates this phenotype. We uncovered a novel inhibitory role in flocculation for Prz1. Loss of prz1(+)resulted in constitutive flocculation and upregulation of genes encoding the flocculins Gsf2 and Pfl3, as well as the transcription factor Cbf12. The constitutive flocculation of the ∆prz1 strain was abrogated by the loss of gsf2(+) or cbf12(+) This study reveals that Prz1 functions as a positive and negative transcriptional regulator of genes involved in cell-wall biosynthesis and flocculation, respectively. Moreover, comparison of target genes between Crz1/CrzA and Prz1 indicate some conservation in DNA-binding specificity, but also substantial rewiring of the calcineurin-mediated transcriptional regulatory network.

Moving towards a paradigm: common mechanisms of chemotactic signaling in Dictyostelium and mammalian leukocytes

Chemotaxis, or directed migration of cells along a chemical gradient, is a highly coordinated process that involves gradient sensing, motility, and polarity. Most of our understanding of chemotaxis comes from studies of cells undergoing amoeboid-type migration, in particular the social amoeba Dictyostelium discoideum and leukocytes. In these amoeboid cells the molecular events leading to directed migration can be conceptually divided into four interacting networks: receptor/G protein, signal transduction, cytoskeleton, and polarity. The signal transduction network occupies a central position in this scheme as it receives direct input from the receptor/G protein network, as well as feedback from the cytoskeletal and polarity networks. Multiple overlapping modules within the signal transduction network transmit the signals to the actin cytoskeleton network leading to biased pseudopod protrusion in the direction of the gradient. The overall architecture of the networks, as well as the individual signaling modules, is remarkably conserved between Dictyostelium and mammalian leukocytes, and the similarities and differences between the two systems are the subject of this review.

Efficient neutrophil extracellular trap induction requires mobilization of both intracellular and extracellular calcium pools and is modulated by cyclosporine A

Excessive or aberrant generation of neutrophil extracellular traps (NETs) has recently become implicated in the underlying aetiology of a number of human pathologies including preeclampsia, systemic lupus erythromatosus, rheumatoid arthritis, auto-antibody induced small vessel vasculitis, coagulopathies such as deep vein thrombosis or pulmonary complications. These results imply that effective pharmacological therapeutic strategies will need to be developed to counter overt NETosis in these and other inflammatory disorders. As calcium flux is implicated in the generation of reactive oxygen species and histone citrullination, two key events in NETosis, we analysed the roles of both extra- and intracellular calcium pools and their modulation by pharmacological agents in the NETotic process in detail. Interleukin-8 (IL-8) was used as a physiological stimulus of NETosis. Our data demonstrate that efficient induction of NETosis requires mobilisation of both extracellular and intracellular calcium pools. Since modulation of the calcineurin pathway by cyclosporine A has been described in neutrophils, we investigated its influence on NETosis. Our data indicate that IL-8 induced NETosis is reduced by ascomycin and cyclosporine A, antagonists of the calcineurin pathway, but not following treatment with rapamycin, which utilizes the mTOR pathway. The action of the G protein coupled receptor phospholipase C pathway appears to be essential for the induction of NETs by IL-8, as NETosis was diminished by treatment with either pertussis toxin, a G-protein inhibitor, the phospholipase C inhibitor, U73122, or staurosporine, an inhibitor of protein kinase C. The data regarding the calcineurin antagonists, ascomycin and cyclosporine A, open the possibility to therapeutically supress or modulate NETosis. They also provide new insight into the mechanism whereby such immune suppressive drugs render transplant patients susceptible to opportunistic fungal infections.

FK506 and Cyclosporin A Enhance IL-6 Production in Monocytes: A single-Cell Assay

The effect of FK506 and cyclosporin A (CsA) on the production of interleukin 6 (IL-6) in adherent monocytes was studied at a single-cell level by the avidinbiotin- peroxidase complex methods. The percentage of IL-6-producing monocytes increased when stimulated with lipopolysaccharide (LPS) at concentrations between 10 ng/ml and 10 μg/ml, in a dose dependent manner. Both FK506 and CsA enhanced the percentage of IL-6- producing monocytes stimulated with 100 pg/ml-1 μg/ml of LPS up to values near those obtained with 10 μg/ml of LPS. The enhancement by FK506 and CsA was not seen when monocytes were stimulated with a high concentration of LPS (10 μg/ml). When monocytes were stimulated with a low concentration of LPS (10 ng/ml), FK506 and CsA enhanced IL-6 production in a dose dependent manner, at a drug concentration of 0.12 nM–1.2 μM (0.1–1 000 ng/ml) for FK506 and 0.83 nM–8.3 μM (1–10 000 ng/ml) for CsA. The optimal effect of FK506 was achieved at a concentration 7-fold lower than that of CsA. In contrast, production of turnout necrosis factor-α (TNFα and interleukin 1β (IL-1β) was slightly suppressed by FK506 and CsA at the concentrations tested. Moreover, pretreatment of monocytes with FK506 and CsA had a significant enhancing effect on LPS-induced IL-6 production, while treatment with FK506 or CsA after LPS stimulation had no effects on IL-6 production, suggesting that the enhancing effect of each drug is exerted before LPS stimulation or at an early stage of the post-receptor pathway after LPS stimulation. These experiments demonstrate that FK506 and CsA can selectively enhance IL-6 production in monocytes under certain conditions in vitro and, possibly, also in vivo.

Genetic screening for regulators of Prz1, a transcriptional factor acting downstream of calcineurin in fission yeast

Calcineurin phosphatase plays crucial roles in a wide variety of cell types and organisms. Dephosphorylation of the nuclear factor of activated T-cell (NFAT) family of transcriptional factors by calcineurin is essential for activating immune-responsive genes in mammals. NFAT activity is also regulated by diverse signaling pathways, which affect NFAT kinases and nuclear partner proteins. In fission yeast, calcineurin dephosphorylates and activates Prz1, a C2H2-type zinc finger transcriptional factor. Calcineurin-Prz1 signaling regulates the expression of the Pmc1 Ca(2+) pump. Prz1-overexpressing cells showed extremely slow growth and high transcriptional activity of Prz1 in the absence of stimulation. Here, we isolated seven genes as dosage-dependent suppressors of this slow growth phenotype. These seven genes encode Rad24, Rad25, Pka1, Msn5 (SPAC328.01c), Pac1, Ape2, and Tfs1. All of them decreased the high transcriptional activity caused by Prz1 overexpression. Overexpression of Pka1, Rad24, and Rad25 also repressed the Ca(2+)-induced transcriptional activity in cells with Prz1 expressed at wild-type levels. Knock-out of rad24 or rad25 significantly enhanced the transcriptional activity of Prz1, whereas knock-out or mutation of other genes did not enhance the activity. The 14-3-3 proteins, Rad24 and Rad25, bound Prz1 and the Rad24-binding site located at residues 421-426 of Prz1. In msn5 deletion mutants, GFP-Prz1 localized at nucleus in the absence of Ca(2+) stimulation, suggesting that Msn5 functions as an exportin for Prz1. In summary, our data suggest that Rad24 and Rad25 negatively regulate Prz1 and that Pka1, Msn5, Pac1, Tfs1, and Ape2 also regulate Prz1.

Force- and Ca2+-dependent internalization of integrins in cultured endothelial cells

The effects of mechanical force applied to the integrin clusters at focal contacts were examined in cultured human umbilical vein endothelial cells. When a fibronectin-coated glass bead was attached to the apical cell surface, focal contacts formed beneath the bead that became linked to focal contacts at the basal cell membrane by actin stress fibers in 5 minutes. Integrin dynamics at the basal focal contacts were monitored in live cells in response to a localized mechanical stimulus generated by displacing the glass bead. Traction force transmitted to the basal focal contacts through the stress fibers was monitored by measuring the deformation of the polyacrylamide gel substratum. The force declined in a few seconds, probably owing to decreases in the elastic modulus of the stress fibers. This transient mechanical stimulus caused the dephosphorylation of paxillin and disassembly of integrin clusters at the basal cell membrane in 20 minutes. The disassembly was mediated mainly by clathrin-dependent endocytosis of integrins. The integrin internalization was inhibited in Ca2+- and K+-free solution, and by phenylarsine oxide, a phosphatase inhibitor. These results suggest that a transient mechanical stimulus applied to focal contacts induces Ca2+-dependent dephosphorylation of some proteins, including paxillin, and facilitates clathrin-dependent endocytosis of integrins.

α-Syntrophin is required for the hepatocyte growth factor-induced migration of cultured myoblasts

Syntrophins are adaptor proteins that link intracellular signaling molecules to the dystrophin based scaffold. In this study, we investigated the function of syntrophins in cell migration, one of the early steps in myogenic differentiation and in regeneration of adult muscle. Hepatocyte growth factor (HGF) stimulates migration and lamellipodia formation in cultured C2 myoblasts. In the migrating cells, syntrophin concentrated in the rear-lateral region of the cell, opposite of the lamellipodia, instead of being diffusely present throughout the cytoplasm of non-migrating cells. When the expression of α-syntrophin, the major syntrophin isoform of skeletal muscle, was reduced by transfection with the α-syntrophin-specific siRNA, HGF stimulation of lamellipodia formation was prevented. Likewise, migration of myoblasts from α-syntrophin knockout mice could not be stimulated by HGF. However, HGF-induced migration was restored in myoblasts isolated from a transgenic mouse expressing α-syntrophin only in muscle cells. Treatment of C2 myoblasts with inhibitors of PI3-kinase not only reduced the rate of cell migration, but also impaired the accumulation of syntrophins in the rear-lateral region of the migrating cells. Phosphorylation of Akt was reduced in the α-syntrophin siRNA-treated C2 cells. These results suggest that α-syntrophin is required for HGF-induced migration of myoblasts and for proper PI3-kinase/Akt signaling.

The endogenous pro-resolving mediators lipoxin A4 and resolvin E1 preserve organ function in allograft rejection

Allograft rejection remains a major limitation to successful solid organ transplantation. Here, we investigated the biosynthesis and bioactions of the pro-resolving mediators lipoxin A(4) and resolvin E1 in host responses to organ transplantation. In samples obtained during screening bronchoscopy after human lung transplantation, bronchoalveolar lavage fluid levels of lipoxin A(4) were increased in association with the severity of allograft rejection that was graded independently by clinical pathology. Lipoxin A(4) significantly inhibited calcineurin activation in human neutrophils, and lipoxin A(4) stable analogs prevented acute rejection of vascularized cardiac and renal allografts. Transgenic animals expressing human lipoxin A(4) receptors revealed important sites of action in host tissues for lipoxin A(4)'s protective effects. Resolvin E1 displays counter-regulatory actions for leukocytes, in part, via increased lipoxin A(4) biosynthesis, yet RvE1 administered (1μg, iv) to donor (days -1 and 0) and recipient mice (days -1, 0 and +4) was even more potent than a lipoxin stable analog (1μg, iv) in prolonging renal allograft survival (median survival time=74.0 days with RvE1 and 37.5 days with a LXA(4) analog). Together, these results highlight the potential for pro-resolving mediators in prolonging survival of solid organ transplants.

Clathrin mediates integrin endocytosis for focal adhesion disassembly in migrating cells

Focal adhesion disassembly is regulated by microtubules (MTs) through an unknown mechanism that involves dynamin. To test whether endocytosis may be involved, we interfered with the function of clathrin or its adaptors autosomal recessive hypercholesteremia (ARH) and Dab2 (Disabled-2) and found that both treatments prevented MT-induced focal adhesion disassembly. Surface labeling experiments showed that integrin was endocytosed in an extracellular matrix-, clathrin-, and ARH- and Dab2-dependent manner before entering Rab5 endosomes. Clathrin colocalized with a subset of focal adhesions in an ARH- and Dab2-dependent fashion. Direct imaging showed that clathrin rapidly accumulated on focal adhesions during MT-stimulated disassembly and departed from focal adhesions with integrin upon their disassembly. In migrating cells, depletion of clathrin or Dab2 and ARH inhibited focal adhesion disassembly and decreased the rate of migration. These results show that focal adhesion disassembly occurs through a targeted mechanism involving MTs, clathrin, and specific clathrin adaptors and that direct endocytosis of integrins from focal adhesions mediates their disassembly in migrating cells.

Calreticulin and focal-contact-dependent adhesion

Cell adhesion is regulated by a variety of Ca2+-regulated pathways that depend on Ca2+-binding proteins. One such protein is calreticulin, an ER-resident protein. Calreticulin signalling from within the ER can affect processes outside the ER, such as expression of several adhesion-related genes, most notably vinculin and fibronectin. In addition, changes in the expression level of calreticulin strongly affect tyrosine phosphorylation of cellular proteins, which is known to affect many adhesion-related functions. While calreticulin has been localized to cellular compartments other than the ER, it appears that only the ER-resident calreticulin affects focal-contact-dependent adhesion. In contrast, calreticulin residing outside the ER may be involved in contact disassembly and other adhesion phenomena. Here, we review the role of calreticulin in focal contact initiation, stabilization, and turnover. We propose that calreticulin may regulate cell-substratum adhesion by participating in an "ER-to-nucleus" signalling and in parallel "ER-to-cell surface" signalling based on posttranslational events.

Mechano-chemical signaling maintains the rapid movement of Dictyostelium cells

The survival of Dictyostelium cells depends on their ability to efficiently chemotax, either towards food or to form multicellular aggregates. Although the involvement of Ca2+ signaling during chemotaxis is well known, it is not clear how this regulates cell movement. Previously, fish epithelial keratocytes have been shown to display transient increases in intracellular calcium ([Ca2+]i) that are mediated by stretch-activated calcium channels (SACs), which play a role in retraction of the cell body [J. Lee, A. Ishihara, G. Oxford, B. Johnson, and K. Jacobson, Regulation of cell movement is mediated by stretch-activated calcium channels. Nature, 1999. 400(6742): p. 382-6.]. To investigate the involvement of SACs in Dictyostelium movement we performed high resolution calcium imaging in wild-type (NC4A2) Dictyostelium cells to detect changes in [Ca2+]i. We observed small, brief, Ca2+ transients in randomly moving wild-type cells that were dependent on both intracellular and extracellular sources of calcium. Treatment of cells with the SAC blocker gadolinium (Gd3+) inhibited transients and decreased cell speed, consistent with the involvement of SACs in regulating Dictyostelium motility. Additional support for SAC activity was given by the increase in frequency of Ca2+ transients when Dictyostelium cells were moving on a more adhesive substratum or when they were mechanically stretched. We conclude that mechano-chemical signaling via SACs plays a major role in maintaining the rapid movement of Dictyostelium cells.

Fibronectin, vitronectin, and collagen I induce chemotaxis and haptotaxis of human and rabbit mesenchymal stem cells in a standardized transmembrane assay

The mesenchymal stem cell (MSC) is a critical element in tissue repair and regeneration. Its ability to differentiate into multiple connective tissue cell types and to self-renew has made it a prime candidate in regenerative medicine strategies. Currently, the environmental cues responsible for in situ recruitment and control of MSC distribution at repair sites are not entirely revealed and in particular the role of extracellular matrix (ECM) proteins as motogenic factors has not been studied. Here we have used a standardized transmembrane chemotaxis assay to assess the chemotactic and haptotactic potential of fibronectin, vitronectin, and collagen type 1 on MSCs from both rabbit and human origin. The use of both cell types was based in part on the widespread use of rabbit models for musculoskeletal-related tissue engineering and repair models and their unknown correspondence to human in terms of MSC migration. The optimized assay yielded a greatly increased chemotactic response toward known factors such as platelet-derived growth factor-BB (PDGF)-BB compared to previous studies. Our primary finding was that all three ECM proteins tested (fibronectin, vitronectin, and collagen I) induced significant motogenic activity, in both soluble and insoluble forms, for both rabbit and human MSCs. These results suggest that ECM proteins could play roles as significant as cytokines in the recruitment of pluripotential repair cells wound and tissue repair sites. Furthermore, designed ECM coatings of scaffolds or implants could provide a new tool to control both cell influx and outflux from the scaffold post-implantation. Finally, the similarity of motogenic behavior of both rabbit and human cells suggests the rabbit is a reliable model for assessing MSC recruitment in repair and regeneration strategies.

Calcium signalling during chemotaxis

The role of Ca2+ in chemotaxis of eosinophils from the newt Taricha granulosa was investigated using fluorescent indicators and digital imaging microscopy. In response to serum chemoattractant, cytoplasmic Ca2+ concentration ([Ca2+]i) rises prior to polarization. In polarized locomoting cells [Ca2+]i gradients (tail-high-front-low) are always seen, and when cells turn [Ca2+]i rises transiently and falls fastest and furthest in the new direction of cell motion. These Ca2+ signals, which are required for polarization and locomotion, arise from Ca2+ derived from internal stores released in response to inositol 1,4,5-trisphosphate (InsP3) (because microinjected heparin fully blocks them). 1,2-Diacyl-sn-glycerol (DAG), which is co-produced with InsP3, has an inhibitory effect on Ca2+ signals, an effect apparently mediated by protein kinase C. Studies with caged InsP3 reveal that InsP3-responsive stores appear to be concentrated in the nuclear and microtubule-organizing centre regions and that InsP3 moves so rapidly within the cell that it is effectively a global secondary messenger. Thus, stable [Ca2+] gradients observed during unidirectional migration appear to result from the concentration of InsP3-responsive Ca2+ stores in the rear of the cell. By contrast, we propose that reorientation of the [Ca2+] gradient prior to a change in direction of motion results from the joint actions of InsP3 and DAG, with InsP3 acting as a global secondary messenger stimulating Ca2+ release and DAG, through protein kinase C, acting as a spatially restricted secondary messenger inhibiting [Ca2+] increases locally near the site of chemotactic stimulation.

A novel function of capsaicin-sensitive TRPV1 channels: Involvement in cell migration

Cell migration relies on a tight temporal and spatial regulation of the intracellular Ca2+ concentration ([Ca2+]i). [Ca2+]i in turn depends on Ca2+ influx via channels in the plasma membrane whose molecular nature is still largely unknown for migrating cells. A mechanosensitive component of the Ca2+ influx pathway was suggested. We show here that the capsaicin-sensitive transient receptor potential channel TRPV1, that plays an important role in pain transduction, is one of the Ca2+ influx channels involved in cell migration. Activating TRPV1 channels with capsaicin leads to an acceleration of human hepatoblastoma (HepG2) cells pretreated with hepatocyte growth factor (HGF). The speed rises by up to 50% and the displacement is doubled. Patch clamp experiments revealed the presence of capsaicin and resiniferatoxin (RTX)-sensitive currents. In contrast, HepG2 cells kept in the absence of HGF are not accelerated by capsaicin and express no capsaicin- or RTX-sensitive current. The TRPV1 antagonist capsazepine prevents the stimulation of migration and inhibits capsaicin-sensitive currents. Finally, we compared the contribution of capsaicin-sensitive TRPV1 channels to cell migration with that of mechanosensitive TRPV4 channels that are also expressed in HepG2 cells. A specific TRPV4 agonist, 4alpha-phorbol 12,13-didecanoate, does not increase the displacement. In summary, we assigned a novel role to capsaicin-sensitive TRPV1 channels. They are important Ca2+ influx channels required for cell migration.

Differential effects of immunosuppressive drugs on T-cell motility

The best-characterized mechanism of the action of immunosuppressive drugs is to prevent T-cell clonal expansion, thus containing the magnitude of the ensuing immune response. As T-cell recruitment to the inflammatory site is another key step in the development of T-cell-mediated inflammation, we analyzed and compared the effects of two commonly used immunosuppressants, cyclosporin A (CsA) and the rapamycin-related compound SDZ-RAD, on the motility of human CD4+ T cells. We show that CsA, but not SDZ-RAD, inhibits T-cell transendothelial migration in vitro. CsA selectively impaired chemokine-induced T-cell chemotaxis while integrin-mediated migration was unaffected. The inhibition of T-cell chemotaxis correlated with reduced AKT/PKB but not ERK activation following exposure to the chemokine CXCL-12/SDF-1. In addition, CsA, but not SDZ-RAD, prevents some T-cell receptor-mediated effects on T-cell motility. Finally, we show that CsA, but not SDZ-RAD inhibits tissue infiltration by T cells in vivo. Our data suggest a prominent antiinflammatory role for CsA in T-cell-mediated tissue damage, by inhibiting T-cell trafficking into tissues in addition to containing clonal expansion.

Identification of SK3 channel as a new mediator of breast cancer cell migration

Potassium channels have been involved in epithelial tumorigenesis but the role of small-conductance Ca(2+)-activated K(+) channels is unknown. We report here that small-conductance Ca(2+)-activated K(+) channels are expressed in a highly metastasizing mammary cancer cell line, MDA-MB-435s. Patch-clamp recordings showed typical small-conductance Ca(2+)-activated K(+) channel-mediated currents sensitive to apamin, 4-aminopyridine, and tetraethylammonium. Moreover, the cells displayed a high intracellular calcium concentration, which was decreased after 24 hours of apamin treatment. By regulating membrane potential and intracellular calcium concentration, these channels were involved in MDA-MB-435s cell migration, but not in proliferation. Only SK3 protein expression was observed in these cells in contrast to SK2, which was expressed both in cancer and noncancer cell lines. Whereas small interfering RNA directed against SK3 almost totally abolished MDA-MB-435s cell migration, transient expression of SK3 increased migration of the SK3-deficient cell lines, MCF-7 and 184A1. SK3 channel was solely expressed in tumor breast biopsies and not in nontumor breast tissues. Thus, SK3 protein channel seems to be a new mediator of breast cancer cell migration and represents a potential target for a new class of anticancer agents.

Real-time monitoring of calcineurin activity in living cells: evidence for two distinct Ca2+-dependent pathways in fission yeast

In fission yeast, calcineurin dephosphorylates and activates the Prz1 transcription factor. Here, we identified the calcineurin-dependent response element (CDRE) in the promoter region of prz1(+) gene and monitored the calcineurin activity in living cells using a destabilized luciferase reporter gene fused to three tandem repeats of CDRE. Elevated extracellular CaCl(2) caused an increase in calcineurin activity with an initial peak and then approached a sustained constant level in a concentration-dependent manner. In CaCl(2)-sensitive mutants such as Deltapmc1, the response was markedly enhanced, reflecting its high intracellular Ca(2+). Agents expected to induce Ca(2+) influx showed distinct patterns of the CDRE-reporter activity, suggesting different mechanisms of calcineurin activation. Knockout of yam8(+) or cch1(+) encoding putative subunits of a Ca(2+) channel abolished the activation of calcineurin upon exposure to various stimuli, including high extracellular NaCl and cell wall-damaging agents. However, knockout of yam8(+) or cch1(+) did not affect the activation of calcineurin upon stimulation by elevated extracellular Ca(2+). The Pck2 protein kinase C-Pmk1 mitogen-activate protein kinase pathway was required for the stimulation of calcineurin via Yam8/Cch1-mediated Ca(2+) influx, but it was not required for the stimulation by elevated extracellular Ca(2+), suggesting two distinct pathways for calcineurin activation.

Local calcium transients contribute to disappearance of pFAK, focal complex removal and deadhesion of neuronal growth cones and fibroblasts

Cell adhesion is crucial for migration of cells during development, and cell-substrate adhesion of motile cells is accomplished through the formation and removal of focal complexes that are sites of cell-substrate contact. Because Ca2+ signaling regulates the rate of axon outgrowth and growth cone turning, we investigated the potential role of Ca2+ in focal complex dynamics. We describe a novel class of localized, spontaneous transient elevations of cytosolic Ca2+ observed both in Xenopus neuronal growth cones and fibroblasts that are 2-6 mum in spatial extent and 2-4 s in duration. They are distributed throughout growth cone lamellipodia and at the periphery of fibroblast pseudopodia, which are regions of high motility. In both cell types, these Ca2+ transients lead to disappearance of phosphorylated focal adhesion kinase (pFAK) and deadhesion from the substrate as assessed by confocal and internal reflection microscopy, respectively. The loss of pFAK is inhibited by cyclosporin A, suggesting that these Ca2+ transients exert their effects via calcineurin. These results identify an intrinsic mechanism for local cell detachment that may be modulated by agents that regulate motility.

Cell migration: mechanisms of rear detachment and the formation of migration tracks

Cell migration is central to many biological and pathological processes, including embryogenesis, tissue repair and regeneration as well as cancer and the inflammatory response. In general, cell migration can be usefully conceptualized as a cyclic process. The initial response of a cell to a migration-promoting agent is to polarize and extend protrusions in the direction of migration. These protrusions can be large, broad lamellipodia or spike-like filopodia, are usually driven by actin polymerization, and are stabilized by adhering to the extracellular matrix (ECM) via transmembrane receptors of the integrin family linked to the actin cytoskeleton. These adhesions serve as traction sites for migration as the cell moves forward over them, and they must be disassembled at the cell rear, allowing it to detach. The mechanisms of rear detachment and the regulatory processes involved are not well understood. The disassembly of adhesions that is required for detachment depends on a coordinated interaction of actin and actin-binding proteins, signaling molecules and effector enzymes including proteases, kinases and phosphatases. Originally, the biochemically regulated processes leading to rear detachment of migrating cells were thought not to be necessarily accompanied by any loss of cell material. However, it has been shown that during rear detachment long tubular extensions, the retracting fibers, are formed and that "membrane ripping" occurs at the cell rear. By this process, a major fraction of integrin-containing cellular material is left behind forming characteristic migration tracks that exactly mark the way a cell has taken.

Ca2+ influx through L-type Ca2+ channels controls the trailing tail contraction in growth factor-induced fibroblast cell migration

Growth factor-induced cell migration underlies various physiological and pathological processes. The mechanisms by which growth factors regulate cell migration are not completely understood. Although intracellular elevation of Ca2+ is known to be critical in cell migration, the source of this Ca2+ elevation and the mechanism by which Ca2+ modulates this process in fibroblast cells are not well defined. Here we show that increase of cellular Ca2+ through Ca2+ influx, rather than Ca2+ release from intracellular stores, is essential for growth factor-induced fibroblast cell migration. Voltage-gated L-type Ca2+ channels, previously known to exist in excitable cells such as neurons and muscle cells, are shown here to be present in fibroblasts as well. Furthermore, these channels are responsible for the Ca2+ influx. L-type Ca2+ channel inhibitors block growth factor-induced Ca2+ influx and fibroblast cell migration. One mechanism by which Ca2+ signals control cell migration is to regulate the contraction of the trailing edge of migrating fibroblasts; this process is controlled by the small GTPase Rho in fast migrating cells such as leukocytes. Downstream of Ca2+, both calmodulin and myosin light chain kinase, but not calcineurin, are involved leading to phosphorylation of the myosin light chain at the trailing end. Thus, trailing edge contraction is critically regulated by Ca2+ influx through L-type Ca2+ channels in growth factor-induced fibroblast cell migration.

Cyclic changes in keratocyte speed and traction stress arise from Ca2+-dependent regulation of cell adhesiveness

The activation of stretch-activated calcium channels (SACs) in keratocytes can induce spatially coordinated increases in traction stress that promote protrusion at the cell front, while simultaneously inducing retraction at the rear. To investigate how this occurs, we correlated calcium-induced changes in traction stress with alterations in cell speed and shape. Cyclic changes in these parameters were associated with each calcium transient. In addition, an inverse relationship was found between traction stress and cell speed, suggesting that alternating changes in adhesiveness were occurring at the rear. We investigated this further by inhibiting or inducing calcium transients and observing the effects on traction stress, cell speed and shape. Inhibition of calcium transients prevented retraction and led to a slow increase in traction stress. In addition, large aggregates of vinculin developed at the lateral rear edges of treated keratocytes, consistent with an increase in adhesiveness. Induction of a calcium transient resulted in a rapid retraction, involving both increased traction stress and adhesion disassembly at the rear. We also found that keratocytes exhibiting frequent transients generated larger traction stress and moved significantly faster than other cells. Together, these data suggest that calcium transients coordinate changes in adhesiveness with SAC-mediated cycles of mechano-chemical feedback.

IL-12 gene therapy is an effective therapeutic strategy for hepatocellular carcinoma in immunosuppressed mice

Immunosuppressive therapy for organ transplantation is essential for controlling rejection. When liver transplantation is performed as a therapy for hepatocellular carcinoma (HCC), recurrent HCC is one of the most fatal complications. In this study, we show that intratumoral murine IL-12 (mIL-12) gene therapy has the potential to be an effective treatment for malignancies under immunosuppression. C3H mice (H-2(k)), injected with FK506 (3 mg/kg) i.p., were s.c. implanted with 2.5 x 10(6) MH134 cells (H-2(k)) and we treated the established HCC with electroporation-mediated gene therapy using mIL-12 plasmid DNA. Intratumoral gene transfer of mIL-12 elevated intratumoral mIL-12, IFN-gamma, and IFN-gamma-inducible protein-10, significantly reduced the number of microvessels and inhibited the growth of HCC, compared with HCC-transferred control pCAGGS plasmid. The inhibition of tumor growth in immunosuppressed mice was comparable with that of mIL-12 gene therapy in immunocompetent mice. Intratumoral mIL-12 gene therapy enhanced lymphocytic infiltration into the tumor and elicited the MH134-specific CTL response even under FK506. The dose of FK506 was sufficient to prevent the rejection of distant allogenic skin grafts (BALB/c mice, H-2(d)) and tumors, B7-p815 (H-2(d)) used as transplants, during mIL-12 gene therapy against MH134. Ab-mediated depletion studies suggested that the inhibition of tumor growth, neovascularization, and spontaneous lung metastasis by mIL-12 was dependent almost entirely on NK cells and partially on T cells. These results suggest that intratumoral mIL-12 gene therapy is a potent effective strategy not only to treat recurrences of HCC in liver transplantation, but also to treat solid malignant tumors in immunosuppressed patients with transplanted organ.

Sequential phosphorylation of visual arrestin in intactLimulusphotoreceptors: Identification of a highly light-regulated site

The visual arrestins in rhabdomeral photoreceptors are multifunctional phosphoproteins. They are rapidly phosphorylated in response to light, but the functional relevance of this phosphorylation is not yet fully understood. The phosphorylation ofLimulusvisual arrestin is particularly complex in that it becomes phosphorylated on three sites, and one or more of these site are phosphorylated even in the dark. The purpose of this study was to examine in detail the light-stimulated phosphorylation of each of the three sites inLimulusvisual arrestin in intact photoreceptors. We found that light increased the phosphorylation of all three sites (S377, S381, and S396), that S381is a preferred phosphorylation site, and that S377and S381are highly phosphorylated in the dark. The major effect of light was to increase the phosphorylation of S396, the site located closest to the C-terminal and very close to the adaptin binding motif. We speculate that the phosphorylation of this site may be particularly important for regulating the light-driven endocytosis of rhabdomeral membrane.

Calcium transients induce spatially coordinated increases in traction force during the movement of fish keratocytes

The coordination of protrusion with retraction is essential for continuous cell movement. In fish keratocytes the activation of stretch-activated calcium channels, and the resulting increase in intracellular calcium, trigger release of the rear cell margin when forward movement is impeded. Although it is likely that retraction involves a calcium-dependent increase in cytoskeletal contractility, it is not known how the timing, magnitude and localization of contractile forces are organized during retraction. We have addressed this question using a new gelatin traction force assay in combination with calcium imaging to determine what changes in cytoskeletal force production accompany calcium-induced retraction. We find that individual calcium transients are followed within seconds by a rapid increase in traction stress that is maintained, or increases in a stepwise manner, until retraction occurs. Increases in traction stress are accompanied by a distinct sequence of changes in the spatial distribution of large traction stresses. Regions of increased traction stress enlarge at the lateral cell margins and expand forward along the cell margin. In particular, rearward facing propulsive' tractions at the leading edge of the cell, which are normally very low, increase several fold. Following retraction, a precipitous drop in traction stress is observed. Such distinct variations in traction stress are not observed in cells when calcium transients are absent. These results suggest a mechanism by which global increases in intracellular calcium can locally regulate contractile force production, in order to maintain a rapid highly directed mode of movement.

How do cells move along surfaces?

The movement of cells along surfaces is a complex phenomenon that consists of several interrelated processes, including cell-substratum adhesion, and extension and retraction of the cell edge, in which the actin cytoskeleton plays a crucial role. The past decade has seen increasingly detailed molecular-based investigations into cell motility, but it is still not known how molecular events are integrated to give cell movement. Molecular studies are now beginning to be linked to a more global concept of how whole cells move, and this combined approach promises to yield new insights into cell locomotion.

Cell migration: integrating signals from front to back

Cell migration is a highly integrated multistep process that orchestrates embryonic morphogenesis; contributes to tissue repair and regeneration; and drives disease progression in cancer, mental retardation, atherosclerosis, and arthritis. The migrating cell is highly polarized with complex regulatory pathways that spatially and temporally integrate its component processes. This review describes the mechanisms underlying the major steps of migration and the signaling pathways that regulate them, and outlines recent advances investigating the nature of polarity in migrating cells and the pathways that establish it.

Antiadhesive role of apical decay-accelerating factor (CD55) in human neutrophil transmigration across mucosal epithelia

Neutrophil migration across mucosal epithelium during inflammatory episodes involves the precise orchestration of a number a cell surface molecules and signaling pathways. After successful migration to the apical epithelial surface, apically localized epithelial proteins may serve to retain PMN at the lumenal surface. At present, identification of apical epithelial ligands and their PMN counter-receptors remain elusive. Therefore, to define the existence of apical epithelial cell surface proteins involved in PMN–epithelial interactions, we screened a panel of antibodies directed against epithelial plasma membranes. This strategy identified one antibody (OE-1) that both localized to the apical cell membrane and significantly inhibited PMN transmigration across epithelial monolayers. Microsequence analysis revealed that OE-1 recognized human decay-accelerating factor (DAF, CD55). DAF is a highly glycosylated, 70–80-kD, glycosyl-phosphatidyinositol–linked protein that functions predominantly as an inhibitor of autologous complement lysis. DAF suppression experiments using antisense oligonucleotides or RNA interference revealed that DAF may function as an antiadhesive molecule promoting the release of PMN from the lumenal surface after transmigration. Similarly, peptides corresponding to the antigen recognition domain of OE-1 resulted in accumulation of PMN on the apical epithelial surface. The elucidation of DAF as an apical epithelial ligand for PMN provides a target for novel anti-inflammatory therapies directed at quelling unwanted inflammatory episodes.

Macrophage--Mycobacterium tuberculosis interactions: role of complement receptor 3

Tuberculosis is the leading infectious disease in the world. Mycobacterium tuberculosis, the causal agent of this disease, invades macrophages and can replicate inside them. Because invasion of macrophages is a critical step for establishing a mycobacterial infection, there is much interest in understanding the mechanisms for M. tuberculosis entry into macrophages. Complement receptor 3 (CR3) is a heterodimeric surface receptor with multiple binding sites, which can mediate complement-opsonized as well as nonopsonic entrance of M. tuberculosis into macrophages. Here, we describe and discuss the role of CR3 in macrophage[bond]M. tuberculosis interactions. The actual information suggests that CR3 mediates a substantial amount of M. tuberculosis binding to macrophages, but CR3 is not related to the mechanisms that allow mycobacteria to survive and replicate intracellularly. Understanding the mechanisms of macrophage[bond]M. tuberculosis interaction will help developing more effective methods to prevent and treat tuberculosis in the future.

Zinc finger protein Prz1 regulates Ca2+ but not Cl- homeostasis in fission yeast. Identification of distinct branches of calcineurin signaling pathway in fission yeast

Calcineurin is an important mediator that connects the Ca(2+)-dependent signaling to various cellular responses in a wide variety of cell types and organisms. In budding yeast, activated calcineurin exerts its function mainly by regulating the Crz1p/Tcn1 transcription factor. Here, we cloned the fission yeast prz1(+) gene, which encodes a zinc finger transcription factor highly homologous to Crz1/Tcn1. Similar to the results in budding yeast, calcineurin dephosphorylated Prz1 and resulted in the trans-location of Prz1 from the cytoplasm to the nucleus. Prz1 expression was stimulated by high extracellular Ca(2+) in a calcineurin-dependent fashion. However, unlike in budding yeast, the prz1-null cells did not show any phenotype similar to those previously reported in calcineurin deletion such as aberrant cell morphology, mating defect, or hypersensitivity to Cl(-). Instead, the prz1-null cells showed hypersensitivity to Ca(2+), consistent with a dramatic decrease in transcription of Pmc1 Ca(2+) pump. Interestingly, overexpression of Prz1 did not suppress the Cl(-) hypersensitivity of calcineurin deletion, and overexpression of Pmp1 MAPK phosphatase suppressed the Cl(-) hypersensitivity of calcineurin deletion but not the Ca(2+) hypersensitivity of prz1 deletion. In addition, mutations in the its2(+)/cps1(+), its8(+), and its10(+)/cdc7(+) genes that showed synthetic lethal genetic interaction with calcineurin deletion did not exhibit synthetic lethality with the prz1 deletion. Our results suggest that calcineurin activates at least two distinct signaling branches, i.e. the Prz1-dependent transcriptional regulation and an unknown mechanism, which functions antagonistically with the Pmk1 MAPK pathway.

Expression profile of the transient receptor potential (TRP) family in neutrophil granulocytes: evidence for currents through long TRP channel 2 induced by ADP-ribose and NAD

An early key event in the activation of neutrophil granulocytes is Ca(2+) influx. Members of the transient receptor potential (TRP) channel family may be held responsible for this. The aim of the present study is to analyse the expression pattern of TRP mRNA and identify characteristic currents unambiguously attributable to particular TRP channels. mRNA was extracted from human neutrophils, isolated by gradient centrifugation and also by magnetically labelled CD15 antibodies. The presence of mRNA was demonstrated using reverse transcriptase-PCR in neutrophils (controlled to be CD5-negative) as well as in human leukaemic cell line 60 (HL-60) cells, for the following TRP species: the long TRPC2 (LTRPC2), the vanilloid receptor 1, the vanilloid receptor-like protein 1 and epithelial Ca(2+) channels 1 and 2. TRPC6 was specific for neutrophils, whereas only in HL-60 cells were TRPC1, TRPC2, TRPC3, melastatin 1 and melastatin-related 1 found. Patch-clamp measurements in neutrophils revealed non-selective cation currents evoked by intracellular ADP-ribose and by NAD(+). Both these modes of activation have been found to be characteristic of LTRPC2. Furthermore, single-channel activity was resolved in neutrophils and it was indistinguishable from that in LTRPC2-transfected HEK-293 cells. The results provide evidence that LTRPC2 in neutrophil granulocytes forms an entry pathway for Na(+) and Ca(2+), which is regulated by ADP-ribose and the redox state.

Fabrication of drug-eluting covered stents with micropores and differential coating of heparin and FK506

To reduce in-stent restenosis rates, we developed a novel drug-eluting covered stent with a microporous elastometric covered film, in which its luminal surface was flat and immobilized with heparin for anticoagulation and its outer surface immobilized with FK506 to prevent neointimal hyperplasia. One month after implantation into the bilateral common carotid arteries, all stented arteries were patent and the luminal surfaces were fully covered with a confluent of endothelial cells irrespective of the drug immobilization. In the control group, which consisted of covered stents without drug immobilization, intensive inflammatory cells adjacent to the stents and neointimal hyperplasia, indicating vascular injury, were observed. In contrast, in the developed drug-eluting stents, only a few inflammatory cells around the stent strut and covered film were observed, and there was no significant neointimal thickening.

Disruption of focal adhesions by integrin cytoplasmic domain-associated protein-1 alpha

Regulation of integrin affinity and clustering plays a key role in the control of cell adhesion and migration. The protein ICAP-1 alpha (integrin cytoplasmic domain-associated protein-1 alpha) binds to the cytoplasmic domain of the beta(1A) integrin and controls cell spreading on fibronectin. Here, we demonstrate that, despite its ability to interact with beta(1A) integrin, ICAP-1 alpha is not recruited in focal adhesions, whereas it is colocalized with the integrin at the ruffling edges of the cells. ICAP-1 alpha induced a rapid disruption of focal adhesions, which may result from the ability of ICAP-1 alpha to inhibit the association of beta(1A) integrin with talin, which is crucial for the assembly of these structures. ICAP-1 alpha-mediated dispersion of beta(1A) integrins is not observed with beta(1D) integrins that do not bind ICAP. This strongly suggests that ICAP-1 alpha action depends on a direct interaction between ICAP-1 alpha and the cytoplasmic domain of the beta(1) chains. Altogether, these results suggest that ICAP-1 alpha plays a key role in cell adhesion by acting as a negative regulator of beta(1) integrin avidity.

Effects of tacrolimus on ischemia-reperfusion injury

In addition to efficacious immunosuppression for the benefit of organ transplantation, tacrolimus has diverse actions that result in amelioration of ischemia-reperfusion injury. Knowledge is accumulating rapidly on the mechanisms through which tacrolimus exerts these cytoprotective effects, including alterations in microcirculation, free radical metabolism, calcium-activated pathways, inflammatory cascades, mitochondrial stability, apoptosis, stress-response proteins, and tissue recovery. Within the nucleus, actions mediating the effects of tacrolimus appear to be dominantly influenced by interactions with the transcription factor, nuclear factor-kappaB. Because tacrolimus is a cornerstone agent in immunosuppression regimens throughout the world and knowledge of its cellular mechanisms is evolving, it is important to update the clinical literature with this information. We reviewed the published literature with intent to portray the interactions of tacrolimus in the intricate cellular mechanisms initiated by ischemia and reperfusion.

Genome-wide analysis of gene expression regulated by the calcineurin/Crz1p signaling pathway in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, the Ca(2+)/calmodulin-dependent protein phosphatase, calcineurin, is activated by specific environmental conditions, including exposure to Ca(2+) and Na(+), and induces gene expression by regulating the Crz1p/Tcn1p transcription factor. We used DNA microarrays to perform a comprehensive analysis of calcineurin/Crz1p-dependent gene expression following addition of Ca(2+) (200 mm) or Na(+) (0.8 m) to yeast. 163 genes exhibited increased expression that was reduced 50% or more by calcineurin inhibition. These calcineurin-dependent genes function in signaling pathways, ion/small molecule transport, cell wall maintenance, and vesicular transport, and include many open reading frames of previously unknown function. Three distinct gene classes were defined as follows: 28 genes displayed calcineurin-dependent induction in response to Ca(2+) and Na(+), 125 showed calcineurin-dependent expression following Ca(2+) but not Na(+) addition, and 10 were regulated by calcineurin in response to Na(+) but not Ca(2+). Analysis of crz1Delta cells established Crz1p as the major effector of calcineurin-regulated gene expression in yeast. We identified the Crz1p-binding site as 5'-GNGGC(G/T)CA-3' by in vitro site selection. A similar sequence, 5'-GAGGCTG-3', was identified as a common sequence motif in the upstream regions of calcineurin/ Crz1p-dependent genes. This finding is consistent with direct regulation of these genes by Crz1p.

Changes in the motility of B16F10 melanoma cells induced by alterations in resting calcium influx

Alterations in the extracellular Ca(2+) or K(+) concentration had significant influences on the motility of B16F10 melanoma cells measured in the absence of exogenous integrins using a conventional Boyden chamber assay. At normal K(+) concentrations, motility increased slightly when the concentration of Ca(2+) was increased 10-fold. At normal Ca(2+) concentrations, motility increased by 290% when the extracellular K(+) concentration was reduced 10-fold (from control of 5.4 mM to 0.54 mM), and increased to 250% of control levels when the K(+) concentration was increased between 30 and 54 mM, but was relatively uninfluenced at K(+) concentrations between 5 and 30 mM. Simultaneous application of low concentrations (20 microM) of GdCl(3) completely prevented the effects of low and high K(+) on motility. Exposure to Gd(3+) or Tb(3+) also produced a flattening of the cells and enhanced cell attachment. Although the steady state intracellular Ca(2+) concentration was not significantly influenced by the K(+) concentration, the resting permeability to divalent cations, determined from Mn(2+) quench rates in fura-loaded cells, was significantly increased by a reduction in the K(+) concentration. These results indicate that resting Ca(2+) influx is critical to the movement of B16F10 melanoma cells, and demonstrate that lanthanides, which block resting Ca(2+) influx pathways, are potent antimotility agents.