Basic fibroblast growth factor enters the nucleolus and stimulates the transcription of ribosomal genes in ABAE cells undergoing G0----G1 transition

The nucleolus is the site for inflammatory RNA decay during infection

Inflammatory cytokines are key signaling molecules that can promote an immune response, thus their RNA turnover must be tightly controlled during infection. Most studies investigate the RNA decay pathways in the cytosol or nucleoplasm but never focused on the nucleolus. Although this organelle has well-studied roles in ribosome biogenesis and cellular stress sensing, the mechanism of RNA decay within the nucleolus is not completely understood. Here, we report that the nucleolus is an essential site of inflammatory pre-mRNA instability during infection. RNA-sequencing analysis reveals that not only do inflammatory genes have higher intronic read densities compared with non-inflammatory genes, but their pre-mRNAs are highly enriched in nucleoli during infection. Notably, nucleolin (NCL) acts as a guide factor for recruiting cytosine or uracil (C/U)-rich sequence-containing inflammatory pre-mRNAs and the Rrp6-exosome complex to the nucleolus through a physical interaction, thereby enabling targeted RNA delivery to Rrp6-exosomes and subsequent degradation. Consequently, Ncl depletion causes aberrant hyperinflammation, resulting in a severe lethality in response to LPS. Importantly, the dynamics of NCL post-translational modifications determine its functional activity in phases of LPS. This process represents a nucleolus-dependent pathway for maintaining inflammatory gene expression integrity and immunological homeostasis during infection.

The nucleolus is the traditional site for ribosomal RNA biogenesis. Here, the authors find that the nucleolus is a site of inflammatory pre-mRNA turnover and elucidated how immune homeostasis can be maintained by controlling inflammatory gene expression.

Cellular and Molecular Preconditions for Retinal Pigment Epithelium (RPE) Natural Reprogramming during Retinal Regeneration in Urodela

Many regeneration processes in animals are based on the phenomenon of cell reprogramming followed by proliferation and differentiation in a different specialization direction. An insight into what makes natural (in vivo) cell reprogramming possible can help to solve a number of biomedical problems. In particular, the first problem is to reveal the intrinsic properties of the cells that are necessary and sufficient for reprogramming; the second, to evaluate these properties and, on this basis, to reveal potential endogenous sources for cell substitution in damaged tissues; and the third, to use the acquired data for developing approaches to in vitro cell reprogramming in order to obtain a cell reserve for damaged tissue repair. Normal cells of the retinal pigment epithelium (RPE) in newts (Urodela) can change their specialization and transform into retinal neurons and ganglion cells (i.e., actualize their retinogenic potential). Therefore, they can serve as a model that provides the possibility to identify factors of the initial competence of vertebrate cells for reprogramming in vivo. This review deals mainly with the endogenous properties of native newt RPE cells themselves and, to a lesser extent, with exogenous mechanisms regulating the process of reprogramming, which are actively discussed.

Mechanisms Regulating Protein Localization

Cellular functions are dictated by protein content and activity. There are numerous strategies to regulate proteins varying from modulating gene expression to post-translational modifications. One commonly used mode of regulation in eukaryotes is targeted localization. By specifically redirecting the localization of a pool of existing protein, cells can achieve rapid changes in local protein function. Eukaryotic cells have evolved elegant targeting pathways to direct proteins to the appropriate cellular location or locations. Here, we provide a general overview of these localization pathways, with a focus on nuclear and mitochondrial transport, and present a survey of the evolutionarily conserved regulatory strategies identified thus far. We end with a description of several specific examples of proteins that exploit localization as an important mode of regulation.

"Nuclear FGF receptor-1 and CREB binding protein: an integrative signaling module"

In this review we summarize the current understanding of a novel integrative function of Fibroblast Growth Factor Receptor-1 (FGFR1) and its partner CREB Binding Protein (CBP) acting as a nuclear regulatory complex. Nuclear FGFR1 and CBP interact with and regulate numerous genes on various chromosomes. FGFR1 dynamic oscillatory interactions with chromatin and with specific genes, underwrites gene regulation mediated by diverse developmental signals. Integrative Nuclear FGFR1 Signaling (INFS) effects the differentiation of stem cells and neural progenitor cells via the gene-controlling Feed-Forward-And-Gate mechanism. Nuclear accumulation of FGFR1 occurs in numerous cell types and disruption of INFS may play an important role in developmental disorders such as schizophrenia, and in metastatic diseases such as cancer. Enhancement of INFS may be used to coordinate the gene regulation needed to activate cell differentiation for regenerative purposes or to provide interruption of cancer stem cell proliferation.

Bent bone dysplasia syndrome reveals nucleolar activity for FGFR2 in ribosomal DNA transcription

Fibroblast growth factor receptor 2 (FGFR2) promotes osteoprogenitor proliferation and differentiation during bone development, yet how the receptor elicits these distinct cellular responses remains unclear. Analysis of the FGFR2-skeletal disorder bent bone dysplasia syndrome (BBDS) demonstrates that FGFR2, in addition to its canonical signaling activities at the plasma membrane, regulates bone formation from within the nucleolus. Previously, we showed that the unique FGFR2 mutations that cause BBDS reduce receptor levels at the plasma membrane and diminish responsiveness to extracellular FGF2. In this study, we find that these mutations, despite reducing canonical signaling, enhance nucleolar occupancy of FGFR2 at the ribosomal DNA (rDNA) promoter. Nucleolar FGFR2 activates rDNA transcription via interactions with FGF2 and UBF1 by de-repressing RUNX2. An increase in the nucleolar activity of FGFR2 in BBDS elevates levels of ribosomal RNA in the developing bone, consequently promoting osteoprogenitor cell proliferation and decreasing differentiation. Identifying FGFR2 as a transcriptional regulator of rDNA in bone unexpectedly reveals a nucleolar route for FGF signaling that allows for independent regulation of osteoprogenitor cell proliferation and differentiation.

The ins and outs of fibroblast growth factor receptor signalling

FGFR (fibroblast growth factor receptor) signalling plays critical roles in embryogensis, adult physiology, tissue repair and many pathologies. Of particular interest over recent years, it has been implicated in a wide range of cancers, and concerted efforts are underway to target different aspects of FGFR signalling networks. A major focus has been identifying the canonical downstream signalling pathways in cancer cells, and these are now relatively well understood. In the present review, we focus on two distinct but emerging hot topics in FGF biology: its role in stromal cross-talk during cancer progression and the potential roles of FGFR signalling in the nucleus. These neglected areas are proving to be of great interest clinically and are intimately linked, at least in pancreatic cancer. The importance of the stroma in cancer is well accepted, both as a conduit/barrier for treatment and as a target in its own right. Nuclear receptors are less acknowledged as targets, largely due to historical scepticism as to their existence or importance. However, increasing evidence from across the receptor tyrosine kinase field is now strong enough to make the study of nuclear growth factor receptors a major area of interest.

Nuclear translocation of FGFR1 and FGF2 in pancreatic stellate cells facilitates pancreatic cancer cell invasion

Pancreatic cancer is characterised by desmoplasia, driven by activated pancreatic stellate cells (PSCs). Over-expression of FGFs and their receptors is a feature of pancreatic cancer and correlates with poor prognosis, but whether their expression impacts on PSCs is unclear. At the invasive front of human pancreatic cancer, FGF2 and FGFR1 localise to the nucleus in activated PSCs but not cancer cells. In vitro, inhibiting FGFR1 and FGF2 in PSCs, using RNAi or chemical inhibition, resulted in significantly reduced cell proliferation, which was not seen in cancer cells. In physiomimetic organotypic co-cultures, FGFR inhibition prevented PSC as well as cancer cell invasion. FGFR inhibition resulted in cytoplasmic localisation of FGFR1 and FGF2, in contrast to vehicle-treated conditions where PSCs with nuclear FGFR1 and FGF2 led cancer cells to invade the underlying extra-cellular matrix. Strikingly, abrogation of nuclear FGFR1 and FGF2 in PSCs abolished cancer cell invasion. These findings suggest a novel therapeutic approach, where preventing nuclear FGF/FGFR mediated proliferation and invasion in PSCs leads to disruption of the tumour microenvironment, preventing pancreatic cancer cell invasion.

Effect of bFGF on the MCF-7 Cell Cycle with CD44(+)/CD24(-): Promoting the G0/G1→G2/S Transition

Purpose

Few cells with stem cell characteristics possess capabilities of self-renewal and differentiation, which leads to high tumorigenesis and resistance to standard chemotherapeutic agents. These cells are mostly quiescent, and arrest occurs at the mitotic G0/G1 phase in mitosis. We explored the effects of basic fibroblast growth factor (bFGF) on the MCF-7 cell cycle with CD44⁺/CD24^-.

Methods

Cancer-initiating cells were propagated as mammospheres. The CD44⁺/CD24^- subpopulation was sorted by a fluorescence activating cell sorter-Vantage flow cytometer. A cell cycle analysis was performed with different bFGF concentrations.

Results

Differences in the CD44⁺/CD24^- cell proliferation under different bFGF concentrations were observed (p=0.001). When the bFGF concentration was increased, the proportion of CD44⁺/CD24^- at G0/G1 decreased (p=0.023).

Conclusion

We conclude that bFGF may sustain CD44⁺/CD24^- cell proliferation and could promote cell progression through the G0/G1→G2/S phase transition.

The pseudopeptide HB-19 binds to cell surface nucleolin and inhibits angiogenesis

Background

Nucleolin is a protein over-expressed on the surface of tumor and endothelial cells. Recent studies have underlined the involvement of cell surface nucleolin in tumor growth and angiogenesis. This cell surface molecule serves as a receptor for various ligands implicated in pathophysiological processes such as growth factors, cell adhesion molecules like integrins, selectins or laminin-1, lipoproteins and viruses (HIV and coxsackie B). HB-19 is a synthetic multimeric pseudopeptide that binds cell surface expressed nucleolin and inhibits both tumor growth and angiogenesis.

Methodology/principal findings

In the present work, we further investigated the biological actions of pseudopeptide HB-19 on HUVECs. In a previous work, we have shown that HB-19 inhibits the in vivo angiogenesis on the chicken embryo CAM assay. We now provide evidence that HB-19 inhibits the in vitro adhesion, migration and proliferation of HUVECs without inducing their apoptosis. The above biological actions seem to be regulated by SRC, ERK1/2, AKT and FAK kinases as we found that HB-19 inhibits their activation in HUVECs. Matrix metalloproteinases (MMPs) play crucial roles in tumor growth and angiogenesis, so we investigated the effect of HB-19 on the expression of MMP-2 and we found that HB-19 downregulates MMP-2 in HUVECs. Finally, down regulation of nucleolin using siRNA confirmed the implication of nucleolin in the biological actions of these peptides.

Conclusions/significance

Taken together, these results indicate that HB-19 could constitute an interesting tool for tumor therapy strategy, targeting cell surface nucleolin.

Nucleolar localization of a netrin-1 isoform enhances tumor cell proliferation

Netrin-1 displays proto-oncogenic activity in several cancers, which is thought to be due to the ability of this secreted cue to stimulate survival when bound to its receptors. We showed that in contrast to full-length, secreted netrin-1, some cancer cells produced a truncated intranuclear form of netrin-1 (ΔN-netrin-1) through an alternative internal promoter. Because of a nucleolar localization signal located in its carboxyl terminus, ΔN-netrin-1 was targeted to the nucleolus, where it interacted with nucleolar proteins, affected nucleolar ultrastructure, and interacted with the promoters of ribosomal genes. Moreover, ΔN-netrin-1 stimulated cell proliferation in vitro and tumor growth in vivo. Thus, some cancer cells produce not only a full-length, secreted form of netrin-1 that promotes cell survival but also a truncated netrin-1 that stimulates cell proliferation, potentially by enhancing ribosome biogenesis.

Nucleophosmin is essential for c-Myc nucleolar localization and c-Myc-mediated rDNA transcription

The transcription factor c-Myc has a critical role in cell proliferation and growth. The control of ribosome biogenesis by c-Myc through the regulation of transcription mediated by all three RNA polymerases is essential for c-Myc-driven proliferation. Specifically, in the nucleolus, c-Myc has been shown to be recruited to ribosomal DNA and activate RNA polymerase (pol) I-mediated transcription of ribosomal RNA (rRNA) genes. In addition, c-Myc accumulates in nucleoli upon inhibition of the proteasome, suggesting nucleolar localization also has a role in c-Myc proteolysis. Nucleophosmin (NPM), a predominantly nucleolar protein, is also critical in ribosome biogenesis and, like c-Myc, is found overexpressed in many types of tumors. Previously, we demonstrated that NPM directly interacts with c-Myc and controls c-Myc-induced hyperproliferation and transformation. Here, we show that NPM is necessary for the localization of c-Myc protein to nucleoli, whereas c-Myc nucleolar localization is independent of p53, Mdm2 and ARF. Conversely, high transient NPM expression enhances c-Myc nucleolar localization, leading to increased c-Myc proteolysis. In addition, NPM is necessary for the ability of c-Myc to induce rRNA synthesis in the nucleolus, and constitutive NPM overexpression stimulates c-Myc-mediated rRNA synthesis. Taken together, these results demonstrate an essential role for NPM in c-Myc nucleolar localization and c-Myc-mediated rDNA transcription.

Nuclear translocation of FGF8 and its implication to induce Sprouty2

Fibroblast growth factor 8 (FGF8) functions as a local organizing signal for the tectum and cerebellum. FGF8 activates Ras-ERK signaling pathway to induce cerebellar development. We paid attention to the difference in the expression pattern of the molecules that are induced by FGF8 in the mid-hind brain region during normal development and after FGF8 misexpression; some are expressed in the area corresponding to the ERK activation domain but the others are expressed corresponding to the Fgf8 expression domain. Since some of the FGF family members are localized in the nucleus, we wondered if FGF8 could localize in the nuclei and function in the nucleus. We first show that in cultured NIH3T3 cells transfected FGF8b could localize in the nucleus. Transfected FGF8b could also localize in the nucleus of the cells in the chick neural tube. In mouse embryonic neural tube, we detected endogenous FGF8 in the nuclei. Implantation of an FGF8b-soaked bead showed that exogenous FGF8b could be translocated to the nuclei in the isthmus. Furthermore, signal-peptide-deletion mutant of FGF8b mainly localized in the nuclei, and induced Sprouty2 without activating ERK in the mesencephalon. Signal-peptide-deletion mutant of FGF8b could not induce Pax2 expression. Taken together, we concluded that FGF8b could be translocated to the nuclei, and that the nuclear FGF8 could function as transcriptional regulator to induce Sprouty2 in the isthmus.

Glycosilated nucleolin as marker for human gliomas

Nucleolin is a multifunctional DNA and RNA binding protein involved in regulation of gene transcription, chromatin remodeling, RNA metabolism, and ribosomal RNA synthesis. Nucleolin seems to be over-expressed in highly proliferative cells and is involved in many aspect of gene expression: DNA recombination and replication, RNA transcription by RNA polymerase I and II, rRNA processing, mRNA stabilization, cytokinesis, and apoptosis. Although nucleolin is localized predominantly in the nucleolus, it has also been shown to be localized in a phosphorylated/glycolsilated form on the cell surface of different cells. Numerous articles dealing with surface nucleolin targeting for tumor therapy have been recently published. However, at present, no extensive informations are so far available for the presence of nucleolin in human gliomas. In the present work we investigated on the presence and localization of nucleolin in glioma on glioma specimens at different grade of malignancy and on primary glioma cell cultures derived by surgical resection, trying to correlate the presence of glycosilated membrane nucleolin with the malignancy grade. To this purpose an antibody produced by us against gp273 protein, demonstrated to recognized the glycosilated surface nucleolin, has been used. The results obtained demonstrate that surface nucleolin increase with the malignancy grade thus suggesting that it may constitute a histopathological marker for glioma grading and a possible tool for targeted therapy.

JNK/ERK/FAK mediate promigratory actions of basic fibroblast growth factor in astrocytes via CCL2 and COX2

While the role of cytokines in causing pro- and anti-inflammatory cascades in the brain and that of chemokines in promoting chemotaxis is well recognized, the immunomodulatory actions of neurotrophins released during brain injury remains largely undetermined. This knowledge gap affects basic fibroblast growth factor (FGF2), which in the brain is mainly produced by astrocytes and characteristically upregulated in reactive astrocytes. The goal of this study was to characterize the inflammatory actions of FGF2 in astrocytes using primary cultures. We report that FGF2 induced the upregulation of monocyte chemoattractant protein (CCL2) and cyclo-oxygenase type 2 (COX2), and the inhibition of lipopolysaccharide-elicited ICAM1 upregulation. The effects of FGF2 were: (i) dependent on gene transcription as revealed by the concomitant regulation of CCL2 or ICAM1 mRNAs; (ii) mediated by the FGF2 receptor type 2; (iii) dependent on ERK, JNK and FAK, and (iv) NF-κB-independent. FGF2 also caused accelerated wound closure dependent on CCL2, COX2, ERK, JNK and FAK in a scratch assay. We conclude that the signaling network triggered by FGF2 in astrocytes converged into accelerating directed motion. It follows that astrocyte migration to injury sites may be a key factor in the repair mechanisms orchestrated by FGF2.

G protein-coupled receptor signalling in the cardiac nuclear membrane: evidence and possible roles in physiological and pathophysiological function

G protein-coupled receptors (GPCRs) play key physiological roles in numerous tissues, including the heart, and their dysfunction influences a wide range of cardiovascular diseases. Recently, the notion of nuclear localization and action of GPCRs has become more widely accepted. Nuclear-localized receptors may regulate distinct signalling pathways, suggesting that the biological responses mediated by GPCRs are not solely initiated at the cell surface but may result from the integration of extracellular and intracellular signalling pathways. Many of the observed nuclear effects are not prevented by classical inhibitors that exclusively target cell surface receptors, presumably because of their structures, lipophilic properties, or affinity for nuclear receptors. In this topical review, we discuss specifically how angiotensin-II, endothelin, β-adrenergic and opioid receptors located on the nuclear envelope activate signalling pathways, which convert intracrine stimuli into acute responses such as generation of second messengers and direct genomic effects, and thereby participate in the development of cardiovascular disorders.

Lessons from in vitro studies and a related intracellular angiotensin II transgenic mouse model

In the classical renin-angiotensin system, circulating ANG II mediates growth stimulatory and hemodynamic effects through the plasma membrane ANG II type I receptor, AT1. ANG II also exists in the intracellular space in some native cells, and tissues and can be upregulated in diseases, including hypertension and diabetes. Moreover, intracellular AT1 receptors can be found associated with endosomes, nuclei, and mitochondria. Intracellular ANG II can function in a canonical fashion through the native receptor and also in a noncanonical fashion through interaction with alternative proteins. Likewise, the receptor and proteolytic fragments of the receptor can function independently of ANG II. Participation of the receptor and ligand in alternative intracellular pathways may serve to amplify events that are initiated at the plasma membrane. We review historical and current literature relevant to ANG II, compared with other intracrines, in tissue culture and transgenic models. In particular, we describe a new transgenic mouse model, which demonstrates that intracellular ANG II is linked to high blood pressure. Appreciation of the diverse, pleiotropic intracellular effects of components of the renin-angiotensin system should lead to alternative disease treatment targets and new therapies.

CIAPIN1 as a therapeutic target in cancer

IMPORTANCE OF THE FIELD

Cytokine-induced apoptosis inhibitor 1 (CIAPIN1) is a newly identified cytokine-induced apoptosis inhibitor, which has roles in cell division and angiogenesis. Owing to its prognostic value for human tumors and involvement in cancer progression and tumor cell resistance to anticancer agents, CIAPIN1 has been proposed as an attractive target for new anticancer interventions.

AREAS COVERED IN THIS REVIEW

We define CIAPIN1's potential function as a new therapeutic target for anticancer interventions and this review covers all related literature on CIAPIN1 in cancer from the past 5 years

WHAT THE READER WILL GAIN

Several preclinical studies have demonstrated that CIAPIN1 is associated with chemotherapy resistance, increased tumor recurrence and shorter patient survival in different human tumor models, making anti-CIAPIN1 therapy an attractive cancer treatment strategy. Recent studies also suggest that CIAPIN1 is expressed at low levels in some types of malignant tumors and that its overexpression may inhibit their proliferation or tumorigenesis.

TAKE HOME MESSAGE

Considering that the exact expression and function of CIAPIN1 are still not well characterized and understood, better knowledge of CIAPIN1 in normal versus tumor tissues will be instrumental for the design of optimal strategies to selectively disrupt CIAPIN1 in cancer.

Proportionally constant quantitative transmission of nucleolin and protein B23 in cycling cancer cells

Objective-To investigate whether and to what extent the two major AgNOR proteins, nucleolin and protein B23, are maintained after one cell division in proliferating cells.Design-Using three asynchronously growing human cancer cell lines, TG, SJNKP, and CHP 212 cells, nucleolin and protein B23 were first identified on SDS-polyacrylamide separated nucleolar proteins, transferred to nitrocellulose and silver stained for AgNOR proteins. Measurement of doubling time indicated a period very close to 24h for each of the cell lines. To quantify the percentage of nucleolin and protein B23 maintained in daughter cells after duplication, cells were labelled with [(35)S]-methionine and a 24h cold chase performed. Nucleolin and protein B23 labelling was evaluated by densitometric analysis on nitrocellulose autoradiograms.Results-The radioactivity relative to nucleolin and protein B23 bands maintained in the daughter cells was a constant fraction of that present before cell duplication. In the three cell lines the percentage of residual radioactivity measured in the nucleolin bands was 42.2, 40.6, and 41.2 and in protein B23 bands 48.0, 46.2, and 44.1.Conclusions-After one cell division the nucleolin and protein B23 quantity present in cells may be highly variable, depending on the amount of the two proteins present in the mother cell. This is important in relation to the correct utilisation of AgNOR protein quantity as an index for evaluating cell kinetics.

Heparan sulfate proteoglycans: structure, protein interactions and cell signaling

Heparan sulfate proteoglycans are ubiquitously found at the cell surface and extracellular matrix in all the animal species. This review will focus on the structural characteristics of the heparan sulfate proteoglycans related to protein interactions leading to cell signaling. The heparan sulfate chains due to their vast structural diversity are able to bind and interact with a wide variety of proteins, such as growth factors, chemokines, morphogens, extracellular matrix components, enzymes, among others. There is a specificity directing the interactions of heparan sulfates and target proteins, regarding both the fine structure of the polysaccharide chain as well precise protein motifs. Heparan sulfates play a role in cellular signaling either as receptor or co-receptor for different ligands, and the activation of downstream pathways is related to phosphorylation of different cytosolic proteins either directly or involving cytoskeleton interactions leading to gene regulation. The role of the heparan sulfate proteoglycans in cellular signaling and endocytic uptake pathways is also discussed.

Effects of basic fibroblast growth factor on angiogenin expression and cell proliferation in H7402 human hepatoma cells

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Basic fibroblast growth factor (bFGF), which is highly expressed in developing tissues and malignant cells, regulates cell growth, differentiation, and migration. Its expression is essential for the progression and metastasis of HCC. This study aims to investigate the effects of bFGF on the expression of angiogenin, another growth factor, which plays an important role in tumor angiogenesis, and on cell proliferation in H7402 human hepatoma cells. The bFGF sense cDNA or antisense cDNA was stably transfected into H7402 cells. Genomic DNA PCR analysis demonstrated that human bFGF sense cDNA or antisense cDNA was inserted into the genome. Furthermore, the expression of bFGF and angiogenin was examined by RT-PCR and Western blot assays. MTT and colony formation assays were employed to determine cell proliferation. Stable bFGF over-expressing and under-expressing transfectants were successfully established. Expression of angiogenin was decreased in the over-expressing bFGF cells (sense transfectants) and was increased in the under-expressing bFGF cells (antisense transfectants). Cell proliferation increased in the bFGF sense transfectants and decreased in the bFGF antisense transfectants. These results demonstrated that the endogenous bFGF may not only negatively regulate the angiogenin expression but also contribute to the overall cell proliferation in H7402 human hepatoma cells. This study may be helpful in finding a potential therapeutic approach to HCC.

Ultrastructural and antigenic properties of neural stem cells and their progeny in adult rat subventricular zone

Neural stem cells (NSCs) in the subventricular zone (SVZ) continuously generate olfactory bulb interneurons in the adult rodent brain. Based on their ultrastructural and antigenic properties, NSCs, transient amplifying precursor cells, and neuroblasts (B, C, and A cells, respectively) have been distinguished in mouse SVZ. Here, we aimed to identify these cell types in rat SVZ ultrastructurally and at the light microscopy level, and to determine the antigenic properties of each cell type using gold and fluorescence immunolabeling. We found astrocytes with single cilia (NSCs, correspond to B cells) and neuroblasts (A cells). We also observed mitotic cells, ependymal cells, displaced ependymal cells, and mature astrocytes. In contrast, transient amplifying precursor cells (C cells) were not detected. The NSCs and neuroblasts had epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor alpha (PDGFRalpha) expressed on the ciliary apparatus and were the only cell types incorporating the proliferation marker BrdU. Throughout mitosis, EGFR and PDGFRalpha were associated with the microtubule of the mitotic spindle. Ependymal and displaced ependymal cells also expressed EGFR and PDGFRalpha on their cilia but did not incorporate BrdU. Our findings indicate that the NSCs in adult rat SVZ give rise directly to neuroblasts. During mitosis, the NSCs disassemble the primary cilium and symmetrically distribute EGFR and PDGFRalpha among their progeny.

High molecular weight FGF2: the biology of a nuclear growth factor

Fibroblast growth factor 2 (FGF2) is one of the most studied growth factors to date. Most attention has been dedicated to the smallest, 18 kDa FGF2 variant that is released by cells and acts through activation of cell-surface FGF-receptor tyrosine kinases. There are, however, several higher molecular weight (HMW) variants of FGF2 that rarely leave their producing cells, are retained in the nucleus and act independently of FGF-receptors (FGFR). Despite significant evidence documenting the expression and intracellular trafficking of HMW FGF2, many important questions remain about the physiological roles and mechanisms of action of HMW FGF2. In this review, we summarize the current knowledge about the biology of HMW FGF2, its role in disease and areas for future investigation.

Phosphorylation of fibroblast growth factor (FGF) receptor 1 at Ser777 by p38 mitogen-activated protein kinase regulates translocation of exogenous FGF1 to the cytosol and nucleus

Exogenous fibroblast growth factor 1 (FGF1) signals through activation of transmembrane FGF receptors (FGFRs) but may also regulate cellular processes after translocation to the cytosol and nucleus of target cells. Translocation of FGF1 occurs across the limiting membrane of intracellular vesicles and is a regulated process that depends on the C-terminal tail of the FGFR. Here, we report that translocation of FGF1 requires activity of the alpha isoform of p38 mitogen-activated protein kinase (MAPK). FGF1 translocation was inhibited after chemical inhibition of p38 MAPK or after small interfering RNA knockdown of p38alpha. Translocation was increased after stimulation of p38 MAPK with anisomycin, mannitol, or H2O2. The activity level of p38 MAPK was not found to affect endocytosis or intracellular sorting of FGF1/FGFR1. Instead, we found that p38 MAPK regulates FGF1 translocation by phosphorylation of FGFR1 at Ser777. The FGFR1 mutation S777A abolished FGF1 translocation, while phospho-mimetic mutations of Ser777 to Asp or Glu allowed translocation to take place and bypassed the requirement for active p38 MAPK. Ser777 in FGFR1 was directly phosphorylated by p38alpha in a cell-free system. These data demonstrate a crucial role for p38alpha MAPK in the regulated translocation of exogenous FGF1 into the cytosol/nucleus, and they reveal a specific role for p38alpha MAPK-mediated serine phosphorylation of FGFR1.

Gene transfer and protein dynamics in stem cells using single cell electroporation in a microfluidic device

There is great interest in genetic modification of bone marrow-derived mesenchymal stem cells (MSC), not only for research purposes but also for use in (autologous) patient-derived-patient-used transplantations. A major drawback of bulk methods for genetic modifications of (stem) cells, like bulk-electroporation, is its limited yield of DNA transfection (typically then 10%). This is even more limited when cells are present at very low numbers, as is the case for stem cells. Here we present an alternative technology to transfect cells with high efficiency (>75%), based on single cell electroporation in a microfluidic device. In a first experiment we show that we can successfully transport propidium iodide (PI) into single mouse myoblastic C2C12 cells. Subsequently, we show the use of this microfluidic device to perform successful electroporation of single mouse myoblastic C2C12 cells and single human MSC with vector DNA encoding a green fluorescent-erk1 fusion protein (EGFP-ERK1 (MAPK3)). Finally, we performed electroporation in combination with live imaging of protein expression and dynamics in response to extracellular stimuli, by fibroblast growth factor (FGF-2). We observed nuclear translocation of EGFP-ERK1 in both cell types within 15 min after FGF-2 stimulation. Due to the successful and promising results, we predict that microfluidic devices can be used for highly efficient small-scale 'genetic modification' of cells, and biological experimentation, offering possibilities to study cellular processes at the single cell level. Future applications might be small-scale production of cells for therapeutic application under controlled conditions.

Nucleolin is a receptor that mediates antiangiogenic and antitumor activity of endostatin

The exact molecular mechanism of how endostatin inhibits angiogenesis and tumor growth remains uncharacterized. Here, we report that endostatin specifically binds to the cell surface nucleolin with high affinity. Blockage of nucleolin by a neutralizing antibody or knockdown of nucleolin by the RNA interference results in loss of antiendothelial activities of endostatin. Importantly, a neutralizing antinucleolin antibody abrogates the antiangiogenic and antitumor activities of endostatin in vivo. Nucleolin and endostatin are colocalized on the cell surface of endothelial cells of angiogenic blood vessels in the tumor environment. Finally, we found that endostatin is internalized and transported into cell nuclei of endothelial cell via nucleolin. In the nucleus, the phosphorylation of nucleolin, which is critical for cell proliferation, can be inhibited by endostatin. Our studies demonstrate that nucleolin is a novel functional receptor for endostatin, and mediates the antiangiogenic and antitumor activities of endostatin. These findings also provide mechanistic insights of how endostatin specifically inhibits proliferating endothelial cell growth and angiogenesis.

Dose response of angiogenesis to basic fibroblast growth factor in rat corneal pocket assay: II. Numerical simulations

Angiogenesis involves interactions among various molecules and cells. To understand the complexity of interactions, we developed a mathematical model to numerically simulate angiogenesis induced by basic fibroblast growth factor (bFGF) in the corneal pocket assay. The model considered interstitial transport of bFGF, cellular uptake of bFGF, and dynamics of vessel growth. The model was validated by comparing simulated vascular networks, induced by bFGF at three different doses: 5 ng, 15 ng, and 50 ng, with experimental data obtained in the first part of the study, in terms of migration distance of vascular network, total vessel length, and number of vessels. The model was also used to simulate growth dynamics of vascular networks as well as spatial and temporal distribution of bFGF, which could not be measured experimentally. Taken together, results of the study suggested that the coupling between diffusion and cellular uptake of bFGF was critical for determining structures of vascular networks and that the mathematical model was appropriate for simulation of angiogenesis in the cornea.

Inactivation of nucleolin leads to nucleolar disruption, cell cycle arrest and defects in centrosome duplication

BACKGROUND

Nucleolin is a major component of the nucleolus, but is also found in other cell compartments. This protein is involved in various aspects of ribosome biogenesis from transcription regulation to the assembly of pre-ribosomal particles; however, many reports suggest that it could also play an important role in non nucleolar functions. To explore nucleolin function in cell proliferation and cell cycle regulation we used siRNA to down regulate the expression of nucleolin.

RESULTS

We found that, in addition to the expected effects on pre-ribosomal RNA accumulation and nucleolar structure, the absence of nucleolin results in a cell growth arrest, accumulation in G2, and an increase of apoptosis. Numerous nuclear alterations, including the presence of micronuclei, multiple nuclei or large nuclei are also observed. In addition, a large number of mitotic cells showed a defect in the control of centrosome duplication, as indicated by the presence of more than 2 centrosomes per cell associated with a multipolar spindle structure in the absence of nucleolin. This phenotype is very similar to that obtained with the inactivation of another nucleolar protein, B23.

CONCLUSION

Our findings uncovered a new role for nucleolin in cell division, and highlight the importance of nucleolar proteins for centrosome duplication.

The fibroblast growth factor-2 antisense gene inhibits nuclear accumulation of FGF-2 and delays cell cycle progression in C6 glioma cells

Fibroblast growth factor-2 (FGF-2) is a potent heparin-binding protein with growth-promoting and anti-apoptotic activity. Transcription of the GFG/NUDT6 gene on the opposite DNA strand generates an overlapping antisense RNA (FGF-AS) implicated in the post-transcriptional regulation of FGF-2. C6 glioma cells coordinately express FGF-2 and FGF-AS mRNA in a cell cycle-dependent manner. Cellular FGF-2 immunoreactivity was also cell cycle-dependent, with marked nuclear accumulation during S-phase. Stable transfection and overexpression of the FGF-AS RNA resulted in suppression of total cellular FGF-2, and a reduction in nuclear accumulation of FGF-2 isoforms. Serum stimulation of growth-arrested wild-type cells evoked a rapid nuclear translocation of FGF-2, and cell cycle re-entry. FGF-AS transfectants, in contrast, showed a significant delay in recovery of both nuclear FGF-2 staining and S-phase re-entry. Similar results were observed when cells were released from aphidicolin-induced G1 arrest or subjected to heat shock. These findings indicate that FGF-AS RNA inhibits expression and cell cycle-dependent nuclear accumulation of FGF-2, and this is associated with a marked delay in S-phase progression. The results suggest that the endogenous FGF antisense RNA may play a significant functional role in the regulation of FGF-2 dependent cell proliferation in FGF-2 expressing cells.

Expression of fibroblast growth factor-2 and brain-derived neurotrophic factor mRNA in the medial prefrontal cortex and hippocampus after uncontrollable or controllable stress

Neurotrophic factors, including basic fibroblast growth factor (FGF-2) and brain-derived neurotrophic factor (BDNF) are known to be affected by exposure to stressful experiences. Here, we examine the effects of behaviorally controllable (escapable tailshock, ES) or uncontrollable (inescapable tailshock, IS) stress on the expression of FGF-2 and BDNF mRNA in subregions of the medial prefrontal cortex (mPFC) and the hippocampal formation (HF) of male Sprague-Dawley rats. ES rats were placed in Plexiglas boxes equipped with a free spinning wheel and IS rats were placed in identical boxes with the wheels fixed. ES and IS rats were yoked such that they received the same tailshocks, but the ES rat could terminate each shock for both rats. No stress controls (NS) remained in their home cages. Rats were killed 0, 2, 24, or 72 h after termination of the stress session. In situ hybridization was performed to measure FGF-2 and BDNF mRNA in the mPFC and HF. In the mPFC, ES produced a significant increase in FGF-2 mRNA expression at 0 and 2 h post-stress. In the HF, ES produced a greater increase in FGF-2 mRNA expression than IS and NS only in CA2. ES also produced an increase in BDNF mRNA expression in the anterior cingulate at 0 h post-stress. No effects of stressor controllability on BDNF were observed in the HF, although both ES and IS decreased BDNF mRNA in the DG. FGF-2 in the mPFC may be involved in emotional regulation ("coping") during stressful experiences.

Transmural communication at a subcellular level may play a critical role in the fallout based-endothelialization of dacron vascular prostheses in canine

A microporous and permeable wall is important for the healing of vascular prostheses, however, the significance of its permeability to soluble substances at subcellular level has not been demonstrated. Polyester arterial prostheses were prepared in such a way that each of them contained three segments, of which at least one segment was impervious and another segment was permeable to water but impermeable to cells. Twenty graft segments were implanted in 7 dogs as a thoraco-abdominal bypass for 2 months. The prostheses were then harvested, photographed, and treated for histological and morphological studies. The low porosity graft capped by two thrombogenic segments was fully endothelialized, proving the fallout mechanism. The striking contrast with its impermeable counterpart demonstrated that a wall permeable to small substances of subcellular level was critical for the endothelial healing. A wide range of water permeabilities did not reveal advantages of high water permeable segments over low water permeable ones. Endothelial ingrowth from anastomoses was also jeopardized in the absence of wall permeability. In conclusion, transmural communication at a subcellular level may have played a critical role in the fallout based-endothelialization of arterial prostheses in canine. This highlights the potential function of perigraft cytokines and growth factors in endothelial healing.

Functions of the histone chaperone nucleolin in diseases

Alteration of nuclear morphology is often used by pathologist as diagnostic marker for malignancies like cancer. In particular, the staining of cells by the silver staining methods (AgNOR) has been proved to be an important tool for predicting the clinical outcome of some cancer diseases. Two major argyrophilic proteins responsible for the strong staining of cells in interphase are the nucleophosmin (B23) and the nucleolin (C23) nucleolar proteins. Interestingly these two proteins have been described as chromatin associated proteins with histone chaperone activities and also as proteins able to regulate chromatin transcription. Nucleolin seems to be over-expressed in highly proliferative cells and is involved in many aspect of gene expression: chromatin remodeling, DNA recombination and replication, RNA transcription by RNA polymerase I and II, rRNA processing, mRNA stabilisation, cytokinesis and apoptosis. Interestingly, nucleolin is also found on the cell surface in a wide range of cancer cells, a property which is being used as a marker for the diagnosis of cancer and for the development of anti-cancer drugs to inhibit proliferation of cancer cells. In addition to its implication in cancer, nucleolin has been described not only as a marker or as a protein being involved in many diseases like viral infections, autoimmune diseases, Alzheimer's disease pathology but also in drug resistance. In this review we will focus on the chromatin associated functions of nucleolin and discuss the functions of nucleolin or its use as diagnostic marker and as a target for therapy

Differences of Cell Growth and Cell Cycle Regulators Induced by Basic Fibroblast Growth Factor Between Nifedipine Responders and Non-responders

Differences of cell proliferation, cell cycle, and G(1)/S transition regulatory proteins of gingival fibroblasts derived from nifedipine-reactive patient (NIFr) and nifedipine-non-reactive patient (NIFn) in the presence of basic fibroblast growth factor (bFGF) were investigated to elucidate the mechanism of gingival overgrowth associated with nifedipine, one of the Ca(2+)-channel blockers. The proliferation rate of NIFr cells in the presence of bFGF significantly increased than NIFn cells. The proportion of NIFr cells that had undergone progression to the S and G(2)/M phases from the G(0)/G(1) phase significantly increased compared to that in NIFn cells. Increases of pRB (Ser807/811), pCDK2 (Thr160), CDK2, and cyclin E protein levels in NIFr cells were greater than those in NIFn cells. The elevations of pRB (Ser780), RB, and cyclin A protein levels in NIFr cells did not differ from those of NIFn cells. The growth of NIFr cells was greater than that of NIFn cells as a result of the active G(1)/S transition of NIFr cells, as assessed by the increments of cyclin E, pCDK2, and pRB (ser807/811) protein in NIFr cells.

Nuclear trafficking of secreted factors and cell-surface receptors: new pathways to regulate cell proliferation and differentiation, and involvement in cancers

Secreted factors and cell surface receptors can be internalized by endocytosis and translocated to the cytoplasm. Instead of being recycled or proteolysed, they sometimes translocate to the nucleus. Nuclear import generally involves a nuclear localization signal contained either in the secreted factor or its transmembrane receptor, that is recognized by the importins machinery. In the nucleus, these molecules regulate transcription of specific target genes by direct binding to transcription factors or general coregulators. In addition to the transcription regulation, nuclear secreted proteins and receptors seem to be involved in other important processes for cell life and cellular integrity such as DNA replication, DNA repair and RNA metabolism.

Nuclear secreted proteins and transmembrane receptors now appear to induce new signaling pathways to regulate cell proliferation and differentiation. Their nuclear localization is often transient, appearing only during certain phases of the cell cycle. Nuclear secreted and transmembrane molecules regulate the proliferation and differentiation of a large panel of cell types during embryogenesis and adulthood and are also potentially involved in wound healing. Secreted factors such as CCN proteins, EGF, FGFs and their receptors are often detected in the nucleus of cancer cells. Nuclear localization of these molecules has been correlated with tumor progression and poor prognosis for patient survival. Nuclear growth factors and receptors may be responsible for resistance to radiotherapy.

Different abilities of the four FGFRs to mediate FGF-1 translocation are linked to differences in the receptor C-terminal tail

Members of the fibroblast growth factor family bind to one or more of the four closely related membrane-spanning FGF receptors. In addition to signaling through the receptors, exogenous FGF-1 and FGF-2 are endocytosed and translocated to the cytosol and nucleus where they stimulate RNA and DNA synthesis. Here we have studied the ability of the four FGF receptors to facilitate translocation of exogenous FGF-1 to the cytosol and nucleus. FGFR1 and FGFR4 were able to mediate translocation, whereas FGFR2 and FGFR3 completely lacked this ability. By analyzing mutant FGFRs we found that the tyrosine kinase domain could be deleted from FGFR1 without abolishing translocation, whereas the C-terminal tail of the FGFRs, constituted by approximately 50 amino acids downstream of the kinase domain, plays a crucial role in FGF-1 translocation. Three amino acids residues within the C-terminal tail were found to be of particular importance for translocation. For FGFR2, the two amino acid substitutions Q774M and P800H were sufficient to enable the receptor to support FGF-1 translocation. The results demonstrate a striking diversity in function of the four FGFRs determined by their C-terminal domain.

Subcellular localization of CIAPIN1

Cytokine-induced apoptosis inhibitor 1 (CIAPIN1) is a newly identified anti-apoptotic molecule. Our previous studies have demonstrated that CIAPIN1 is ubiquitously expressed in normal fetal and adult human tissues and confers multidrug resistance in gastric cancer cells, possibly by upregulating the expression of multidrug resistance gene 1 and multidrug resistance-related protein 1. However, fundamental biological functions of CIAPIN1 have not been elucidated. In this study, we first predicted the subcellular localization of CIAPIN1 with bioinformatic approaches and then characterized the intracellular localization of CIAPIN1 in both human and mouse cells by a combination of techniques including (a)immunohistochemistry and immunofluorescence, (b) His-tagged CIAPIN1 expression, and (c)subcellular fractionation and analysis of CIAPIN1 in the fractions by Western blotting. All methods produced consistent results; CIAPIN1 was localized in both the cytoplasm and the nucleus and was accumulated in the nucleolus. Bioinformatic prediction disclosed a putative nuclear localization signal and a putative nuclear export signal within both human and mouse CIAPIN1. These findings suggest that CIAPIN1 may undergo a cytoplasm-nucleus-nucleolus translocation.

An intracrine view of angiogenesis

Angiogenesis, the generation of new blood vessels from pre-existing vessels, is an integral component of wound healing, responses to inflammation and other physiologic processes. It is also an essential part of tumor growth; in the absence of new vessel formation, tumors cannot expand beyond a small volume. Although much is known about angiogenesis and its regulation, there is no overall theory that describes or explains this process. It is here suggested that the intracrine hypothesis, which ascribes to certain extracellular signaling peptides (whether hormones, growth factors, DNA-binding proteins or enzymes) a role in both intracellular biology and extracellular signaling, can contribute to a more general understanding of angiogenesis. Intracrine factors participate in angiogenesis in the following ways: (1) they can act within the cells that synthesized them (type I intracrine action), (2) they can be secreted and then taken up by their cell of synthesis to act intracellularly (type II intracrine action ), or (3) they can be secreted and internalized by a distant target cell (type III intracrine action). The parallels between the intracrine growth factor mechanisms cancer cells employ in stimulating their own growth and the mechanisms operative in endothelial cell proliferation during angiogenesis ("intracrine reciprocity") are discussed. Collectively, these explorations lead to testable hypotheses regarding the regulation of normal and pathological angiogenesis, and point to similarities between tumor-induced angiogenesis and tissue differentiation.

Fibroblast growth factor 2 induced proliferation in osteoblasts and bone marrow stromal cells: a whole cell model

Fibroblast growth factor 2 (FGF2) can enhance the proliferative capacity of bone and bone marrow stromal cells; however, the mechanisms behind this effect are not well described. We present a whole-cell kinetic model relating receptor-mediated binding, internalization, and processing of FGF2 to osteoblastic proliferative response. Focusing on one of the potential signaling complex stoichiometries, we utilized experimentally measured and modeled estimated rate constants to predict in vitro proliferation and distinguish between potential binding orders. We found that piecewise assemblage of a ternary signaling complex may occur in several ways depending on the local binding environment. Using experimental data of endocytosed FGF2 as a constraint, we have also shown evidence of potential multistep processes involved in heparan-sulfate proteoglycans-bound FGF2 release, internalization, and fragment formation in conjunction with the normal metabolism of the proteoglycan.

PDGF and microvessel wall remodeling in adult rat lung: imaging PDGF-AA and PDGF-Ralpha molecules in progenitor smooth muscle cells developing in experimental pulmonary hypertension

Smooth muscle cells are mostly absent from the walls of microvessels in the adult lung but develop in large numbers as part of the pathology of human and experimental pulmonary hypertensions (PHs). We have previously shown, in an in vivo model of experimental PH, that mesenchymal (interstitial) fibroblasts and intermediate cells are the progenitors of these cells. Although smooth muscle cell development is a defining pathophysiological feature of human PH, little is known about the angiogenic signaling molecules responsible. Here, we report data for platelet-derived growth factor AA (PDGF-AA) and PDGF-Ralpha, two components of an important signaling pathway for fibroblast and myofibroblast proliferation and migration. Using antibodies linked to protein-A gold and high-resolution imaging techniques, we analyzed the expression of these molecules as smooth muscle cells developed from progenitor cell populations and in endothelial cells of the same microvessels. PDGF-AA was highly expressed by each cell type in control lung. As PH developed, the number of antigenic sites for PDGF-AA decreased with time. PDGF-Ralpha expression levels in the control lung were low, relative to the ligand, and fell in PH. These data show, for the first time, a marked phenotypic shift in expression levels of the PDGF-AA isoform and its receptor tyrosine kinase in the progenitor smooth muscle cells developing in the microvessels of the adult hypertensive lung.

Functional diversity of FGF-2 isoforms by intracellular sorting

Regulation of the subcellular localization of certain proteins is a mechanism for the regulation of their biological activities. FGF-2 can be produced as distinct isoforms by alternative initiation of translation on a single mRNA and the isoforms are differently sorted in cells. High molecular weight FGF-2 isoforms are not secreted from the cell, but are transported to the nucleus where they regulate cell growth or behavior in an intracrine fashion. 18 kDa FGF-2 can be secreted to the extracellular medium where it acts as a conventional growth factor by binding to and activation of cell-surface receptors. Furthermore, following receptor-mediated endocytosis, the exogenous FGF-2 can be transported to the nuclei of target cells, and this is of importance for the transmittance of a mitogenic signal. The growth factor is able to interact with several intracellular proteins. Here, the mode of action and biological role of intracellular FGF-2 are discussed.

Impact of basic FGF expression in astrocytes on dopamine neuron synaptic function and development

Behavioural sensitization to amphetamine (AMPH) requires action of the drug in the ventral midbrain where dopamine (DA) neurons are located. In vivo studies suggest that AMPH sensitization requires enhanced expression of basic fibroblast growth factor (bFGF) in the nucleus of midbrain astrocytes. One idea is that the AMPH-induced increase in bFGF expression in astrocytes leads to enhanced secretion of this peptide and to long-term plasticity in DA neurons. To study directly the effects of astrocytic expression of bFGF on DA neurons, we established a cell-culture model of mesencephalic astrocytes and DA neurons. Immunolabelling showed that even in the absence of a pharmacological stimulus, the majority of mesencephalic astrocytes in culture express bFGF at a nuclear level. Arguing against the idea that bFGF was secreted, bFGF was undetectable in the extracellular medium (below 10 pg/mL). However, supplementing culture medium with exogenous bFGF at standard concentrations (20 ng/mL) led to a dramatic change in the morphology of astrocytes, increased spontaneous DA release, and inhibited synapse formation by individual DA neurons. RNA interference (siRNA) against bFGF mRNA, caused a reduction in DA release but produced no change in synaptic development. Together these data demonstrate that under basal conditions (in the absence of a pharmacological stimulus such as amphetamine) bFGF is not secreted even though there is abundant nuclear expression in astrocytes. The effects of bFGF seen here on DA neurons are thus likely to be mediated through more indirect glial-neuronal interactions, leading to enhanced DA release without a necessary change in synapse number.

Nuclear localization of SP, CGRP, and NK1R in a subpopulation of dorsal root ganglia subpopulation cells in rats

Signals generated by renal pelvic afferent nerves in response to stimulation are transmitted from peripheral processes of dorsal root ganglia neurons to their central terminals in the dorsal horn of the spinal cord to cause the release of neuropeptides, including SP and CGRP. All of the cellular activities of SP are considered to be mediated through interaction with NK(1)R located on the cell surface. We have investigated the colocalization and subcellular distribution of NK(1)R, SP, and CGRP in different subpopulations of neurons that innervate renal tissue. Our findings therefore provide the first evidence for the presence of NK(1)R, SP, and CGRP in the nuclei of DGR neural cells. The physiological significance of this localization remains unknown. One possibility is that pelvic sensory neurons may regulate their responses to different stimuli by modulating the ratio of CGRP and SP release and/or nuclear NK(1)R expression.

FGF-1 and FGF-2 Require the Cytosolic Chaperone Hsp90 for Translocation into the Cytosol and the Cell Nucleus

Similarly to many protein toxins, the growth factors fibroblast growth factor 1 (FGF-1) and FGF-2 translocate from endosomes into the cytosol. It was recently found that certain toxins are dependent on cytosolic Hsp90 for efficient translocation across the endosomal membrane. We therefore investigated the requirement for Hsp90 in FGF translocation. We found that low concentrations of the specific Hsp90 inhibitors, geldanamycin and radicicol, completely blocked the translocation of FGF-1 and FGF-2 to the cytosol and the nucleus. The drugs did not interfere with the initial binding of FGF-1 to the growth factor receptors at the cell-surface or with the subsequent internalization of the growth factors into endosomes. The activation of known signaling cascades downstream of the growth factor receptors was also not affected by the drugs. The data indicate that the drugs block translocation from endosomes to the cytosol implying that Hsp90 is required for translocation of FGF-1 and FGF-2 across the endosomal membrane.

Dehydrated form of plasmid expressing basic fibroblast growth factor-polyethylenimine complex is a novel and accurate method for gene transfer to the cornea

PURPOSE

We describe a novel vector system of nonviral gene transfer into the cornea using a dehydrated form of a plasmid expressing basic fibroblast growth factor-polyethylenimine (p-bFGF-PEI) complex to induce angiogenesis.

METHODS

Corneal neovascularization was evaluated in 48 eyes of Sprague-Dawley rats after implantation of a dehydrated form of PEI containing 1 microg green fluorescent protein (p-GFP-PEI; control group), or 10 microg, 1 microg, or 0.1 microg of p-bFGF-PEI introduced by spin vacuum at ambient temperature. Neovascularization was observed and quantified from day 1 to day 45. Eighteen kDa bFGF protein expression was analyzed by Western blot and immunohistochemistry.

RESULTS

Limbal vessels began to sprout on day 3 in the p-bFGF-PEI groups. The dehydrated form of the p-bFGF-PEI complex induced dose-dependent corneal neovascularization, which reached a maximum on days 24-30 in the 10 microg bFGF group, days 18-24 in the 1 microg bFGF group, and days 15-21 in 0.1 microg bFGF group, and then regressed progressively. No neovascularization was observed in the GFP group.

CONCLUSIONS

The dehydrated form of the p-bFGF-PEI complex is a novel and precise method for controlling the dose, localizing the reagents, and avoiding loss of liquid form during transfection into corneal tissue.

Changes in fibroblast growth factor 2 and its receptors in bovine follicles before and after GnRH application and after ovulation

The aim of this study was to evaluate the expression pattern of fibroblast growth factor 2 (FGF2), its receptor variants (FGFR1IIIc, FGFR2IIIc) and nucleolin in time-defined follicle classes before and after GnRH application and after ovulation in the cow. Ovaries containing preovulatory follicles or new corpora lutea (CL) were collected at approximately 0, 4, 10, 20 and 25 h (follicles) and 60 h (new CL) relative to injection of GnRH to induce an LH surge (n = 5 animals per group). The expressions of FGF2 and FGFR1IIIc mRNA were significantly up-regulated only in the follicle group 4 h after GnRH (during the LH surge) with a significant down-regulation immediately afterwards. Western blot analyses showed two protein bands with at 22 and 18 kDa with apparent up-regulation beginning with the LH surge (4 h) and maximum levels 20 h after GnRH. FGF2 protein in follicles collected at 0 h (before LH surge) was localised in theca tissue (endothelial and pericytes of blood vessels) but not in granulosa cells (GCs). The FGF2 staining (by immunohistochemistry) pattern changed dramatically after the LH surge for a short period (about 2 days) and FGF2 protein was localised dominantly in the nucleus of many GCs, while most capillary endothelial cells were FGF2 immunonegative. In conclusion, the novel observation of FGF2 up-regulation and the distinct change in FGF2 localisation from theca (cytoplasm of endothelial cells) to the nucleus of GCs after the LH surge may be important for survival of GCs or for the transition of the GCs to luteal cells.