Colony-stimulating Factor Receptor Expression Research Articles

Complementation of growth factor receptor-dependent mitogenic signaling by a truncated type I phosphatidylinositol 4-phosphate 5-kinase.

Substitution of phenylalanine for tyrosine at codon 809 (Y809F) of the human colony-stimulating factor 1 (CSF-1) receptor (CSF-1R) impairs ligand-stimulated tyrosine kinase activity, prevents induction of c-MYC and cyclin D1 genes, and blocks CSF-1-dependent progression through the G1 phase of the cell cycle. We devised an unbiased genetic screen to isolate genes that restore the ability of CSF-1 to stimulate growth in cells that express mutant CSF-1R (Y809F). This screen led us to identify a truncated form of the murine type Ibeta phosphatidylinositol 4-phosphate 5-kinase (mPIP5K-Ibeta). This truncated protein lacks residues 1 to 238 of mPIP5K-Ibeta and is catalytically inactive. When we transfected cells expressing CSF-1R (Y809F) with mPIP5K-Ibeta (delta1-238), CSF-1-dependent induction of c-MYC and cyclin D1 was restored and ligand-dependent cell proliferation was sustained. CSF-1 normally triggers the rapid disappearance of CSF-1R (Y809F) from the cell surface; however, transfection of cells with mPIP5K-Ibeta (delta1-238) stabilized CSF-1R (Y809F) expression on the cell surface, resulting in elevated levels of ligand-activated CSF-1R (Y809F). These results suggest a role for PIP5K-Ibeta in receptor endocytosis and that the truncated enzyme compensated for a mitogenically defective CSF-1R by interfering with this process.

Localization and expression of CSF-1 receptor in rat dental follicle cells.

Colony-stimulating factor-1 (CSF-1) accelerates tooth eruption in rats and is localized in the dental follicle, a loose connective tissue sac that is necessary for eruption to occur. CSF-1 enhances the cellular events that occur in the follicle prior to eruption--namely, an influx of monocytes into the follicle early post-natally to form the osteoclasts needed to resorb bone for the eruption pathway. Because CSF-1 levels are at a peak at day 3 post-natally, and because CSF-1 has an autocrine effect on its own gene expression, the question remains as to what causes the subsequent decline in CSF-1 protein and mRNA after day 3 post-natally. To determine if the autocrine effect is inhibited through the CSF-1 receptor, analysis of the CSF-1 receptor mRNA levels in cultured dental follicle cells reveals that high concentrations of CSF-1 reduce the gene expression of the CSF-1 receptor. Interleukin 1 alpha, a molecule that enhances CSF-1 gene expression, has no effect on CSF-1 receptor mRNA levels. Immunostaining for the CSF-1 receptor protein shows that it is present in the dental follicle early post-natally and is either absent or greatly reduced by day 10 post-natally. Earlier studies showed that the mRNA levels of the CSF-1 receptor also parallel this time course. Thus, the above results suggest that the feedback inhibition of the autocrine effect of CSF-1 on its own expression is through the effect of CSF-1 inhibiting the translation and transcription of its receptor. In turn, these molecular interactions possibly regulate the cellular events that occur in the follicle prior to and during eruption.

Granulocyte colony-stimulating factor receptor expression on human transitional cell carcinoma of the bladder.

Receptors for granulocyte colony-stimulating factor (G-CSFRs) have been confirmed on the cell surfaces of several non-haematopoietic cell types, including bladder cancer cells. This observation has naturally led to the hypothesis that the expression of G-CSFR on these cells may enhance their growth by G-CSF. In this study, the expression of G-CSFR was determined in both established human bladder cancer cell lines and primary bladder cancers. We studied five different human bladder cancer cell lines (KU-1, KU-7, T-24, NBT-2 and KK) and 26 newly diagnosed bladder tumours. G-CSFR mRNA expressions on cultured cell lines were determined using the reverse transcriptase polymerase chain reaction (RT-PCR) method. Furthermore, the G-CSFR binding experiments on the cultured cell lines were conducted using the Na(125)I-labelled G-CSF ligand-binding assay method. Moreover, the G-CSFR mRNA expressions on primary bladder tumour specimens were assessed using the in situ RT-PCR method. Three out of the five cultured cell lines (KU-1, NBT-2 and KK) exhibited G-CSFR mRNA signals when the RT-PCR method was used. The G-CSFR binding experiments showed an equilibrium dissociation constant (K[d]) of 490 pM for KU-1, 340 pM for NBT-2 and 103 pM for KK cells. With in situ RT-PCR, the tumour cells of 6 out of 26 primary bladder tumour specimens (23.1%) presented positive G-CSFR mRNA signals. Thus, in this study, G-CSFR expression was frequently observed on bladder cancer cells. Therefore, the clinical use of G-CSF for patients with bladder cancer should be selected with great care.

UVB Radiation Interrupts Cytokine-mediated Support of an Epidermal-derived Dendritic Cell Line (XS52) By a Dual Mechanism

We have established long-term dendritic cell lines from the epidermis of newborn mice. These cell lines (XS series) proliferate maximally in response to granulocyte/macrophage-colony stimulating factor, as well as to CSF-1, which is produced by skin-derived NS fibroblast lines and by keratinocytes (albeit in smaller amounts). The purpose of this study was to examine the impact of UVB radiation on CSF-1-mediated interaction of dendritic cells with fibroblasts and keratinocytes. Exposure of NS cells to UVB radiation (unfiltered FS20 sunlamp) decreased CSF-1 production at mRNA and protein levels. Both changes occurred in a dose-dependent fashion, with 50 J/m2 causing a significant reduction. UVB radiation also downregulated CSF-1 mRNA expression by Pam 212 keratinocytes. UVB exposure of XS cells diminished the surface expression of CSF-1 receptors, with 50 J/m2 causing a significant reduction. Thus, UVB radiation interrupts CSF-1-mediated cell-cell interaction by a dual mechanism: downregulating CSF-1 production and abrogating CSF-1 receptor expression. Importantly, granulocyte/macrophage-colony stimulating factor receptor expression by XS cells was also inhibited by UVB radiation, once again, with 50 J/m2 producing significant inhibition. We propose that the resulting CSF-1 deficiency in epidermal microenvironment and unresponsiveness by dendritic cells to relevant growth factors may contribute to UVB-mediated loss of resident epidermal dendritic cells (i.e., Langerhans cells) in skin.

Macrophage colony-stimulating factor release and receptor expression in bone cells.

Colony-stimulating factors (CSF) may play a role in bone resorption. To examine whether osteoblasts secrete colony-stimulating activity (CSA) in response to parathyroid hormone (PTH) and parathyroid hormone-related peptide (PTHrP), conditioned medium (CM) from ROS 17/2.8 cells and primary rat osteoblasts were examined for induction of clonal growth of cultured rat bone marrow cells. Untreated cells constitutively secreted CSA, which increased with PTH and PTHrP treatment. The colonies formed were principally comprised of macrophages, and preincubation of CM with antiserum to murine macrophage colony-stimulating factor (M-CSF) neutralized most of the CSA, suggesting that the osteoblast-derived CSA was predominantly due to M-CSF. PTHrP treatment upregulated steady-state M-CSF mRNA levels. To investigate a paracrine role for M-CSF in bone we examined bone tissue and cells for the M-CSF receptor c-fms using immunohistochemical techniques and demonstrated staining of mature osteoclasts both in situ and after isolation. We conclude that M-CSF is responsible for the majority of the CSA released by PTH- and PTHrP-treated rat osteoblasts. In addition we identified CSF-1 receptor expression in mature osteoclasts. These data suggest that M-CSF is a mediator of osteoblast-osteoclast interaction in PTH- and PTHrP-induced bone resorption.

TGF-beta is a bidirectional modulator of cytokine receptor expression on murine bone marrow cells. Differential effects of TGF-beta 1 and TGF-beta 3.

Transforming growth factor beta (TGF-beta), an immunomodulator, has inhibitory as well as stimulatory effects on bone marrow cells. In this study, we demonstrate that TGF-beta 1 also is a bidirectional modulator of CSF receptor expression on murine bone marrow cells. TGF-beta 1 up-regulated granulocyte-macrophage (GM)-CSF receptor expression in a time- and dose-dependent manner, with a maximum up-regulation of 64% by 48 h at 20 ng/ml. In contrast, TGF-beta 1 down-modulated IL-3 and CSF-1 receptor expression by 54 and 55%, respectively, by 24 h. TGF-beta 1 did not affect G-CSF receptor expression, in agreement with its inability to affect G-CSF-induced proliferation. The CSF receptor modulation induced by TGF-beta 1 preceded its effects on CSF-stimulated proliferation. The effects of TGF-beta on CSF receptor expression were isoform dependent, thus TGF-beta 3 was a 10-fold more potent inhibitor of both IL-3-induced colony formation and IL-3 receptor expression than TGF-beta 1, whereas TGF-beta 1 was a more potent stimulator of GM-CSF-stimulated colonies and GM-CSF receptor expression than TGF-beta 3. Therefore, the ability of TGF-beta to modulate the CSF receptor density/cell and/or the actual number of progenitors expressing CSF receptors directly correlates with the multifunctional effects of TGF-beta in hematopoiesis.

Induction of colony-stimulating factor receptor expression on hematopoietic progenitor cells: proposed mechanism for growth factor synergism

In many cells systems, the cellular interaction between two or more humoral factors leads to a synergistic response in terms of cellular growth and function. In particular, the growth and differentiation of hematopoietic progenitor cells involves numerous synergistic interactions between colony-stimulating factors (CSFs) that individually stimulate hematopoiesis (granulocyte-CSF, granulocyte- macrophage-CSF, and interleukin-3 [IL-3]), as well as between these factors and other cytokines that individually have no proliferative effect on progenitor cell growth (IL-1 and IL-6). The present study investigated whether hematopoietic growth factor (HGF) synergy could be mediated by upregulation of CSF receptors. Synergistic effects on bone marrow (BM) progenitor cell colony formation, regardless of the combination of factors used, were consistently preceded by increased CSF receptor expression on highly enriched BM progenitor cells, but not on unfractionated BM cells. Induction of CSF receptors preceded detectable differentiation and did not require cell division because nocodazole, an inhibitor of mitosis, blocked CSF-mediated cell proliferation, but not receptor upregulation. Furthermore, combinations of cytokines that did not synergize also failed to affect the level of CSF receptors on BM progenitors. These results have led us to propose a model for HGF synergy whereby one mechanism of action the investigated synergistic cytokines might be the ability to induce increased expression of CSF receptors.

Induction of Colony-Stimulating Factor Receptor Expression on Hematopoietic Progenitor Cells: Proposed Mechanism for Growth Factor Synergism

In many cells systems, the cellular interaction between two or more humoral factors leads to a synergistic response in terms of cellular growth and function. In particular, the growth and differentiation of hematopoietic progenitor cells involves numerous synergistic interactions between colony-stimulating factors (CSFs) that individually stimulate hematopoiesis (granulocyte-CSF, granulocyte-macrophage-CSF, and interleukin-3 [IL-3]), as well as between these factors and other cytokines that individually have no proliferative effect on progenitor cell growth (IL-1 and IL-6). The present study investigated whether hematopoietic growth factor (HGF) synergy could be mediated by upregulation of CSF receptors. Synergistic effects on bone marrow (BM) progenitor cell colony formation, regardless of the combination of factors used, were consistently preceded by increased CSF receptor expression on highly enriched BM progenitor cells, but not on unfractionated BM cells. Induction of CSF receptors preceded detectable differentiation and did not require cell division because nocodazole, an inhibitor of mitosis, blocked CSF-mediated cell proliferation, but not receptor upregulation. Furthermore, combinations of cytokines that did not synergize also failed to affect the level of CSF receptors on BM progenitors. These results have led us to propose a model for HGF synergy whereby one mechanism of action the investigated synergistic cytokines might be the ability to induce increased expression of CSF receptors.

Alterations in CSF-1 Receptor Expression and Protein Tyrosine Phosphorylation in Autonomous Mutants of a CSF-1 Dependent Macrophage Cell Line

One approach to the problem of growth factor signal transduction is to identify alterations in growth factor-regulated events in mutants possessing an altered proliferative response. This approach was used in a study of the alterations in protein tyrosine phosphorylation in 22 independently-arising autonomous mutants of the CSF-1-dependent mouse macrophage cell line, BAC1.2F5. Only 4 of the mutants produced CSF-1 and/or factors that were capable of down-regulating the CSF-1 receptor (CSF-1R), suggesting that the majority were altered in the signal transduction pathway for proliferation. All of the mutants possessed lower numbers (13-89%) of cell surface CSF-1Rs than wild type cells. With two possible exceptions, the phosphorylation of the anti-phosphotyrosine-reactive cell surface CSF-1Rs from CSF-1 stimulated cells was directly proportional to cell surface CSF-1R number. In the absence of CSF-1, three of the 22 mutants exhibited tyrosine phosphorylation of proteins that was not observed in wild type cells under the same conditions. The results indicate that this approach will be useful in the analysis of the growth factor regulated pathway for cell proliferation.

1,25-Dihydroxyvitamin D3Modulates Colony-Stimulating Factor-1 Receptor Binding by Murine Bone Marrow Macrophage Precursors*

1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] has been shown to be a potent agent for monocyte/macrophage differentiation in leukemic cell lines. This study examines the differentiational effects of 1,25-(OH)2D3 in authentic murine bone marrow immature uncommitted precursor cells collected by pretreatment of murine bone marrow with 5-fluorouracil (5-FU). Early precursor cells, collected 1 day after 5-FU treatment, are characterized by low expression of the colony-stimulating factor-1. (CSF-1) receptor and dependence on both CSF-1 and interleukin-1 for growth. Intermediate precursors were collected 5 days after 5-FU treatment and required either CSF-1 or interleukin-3 for growth. Intermediate precursors expressed relatively higher levels of the CSF-1 receptor. Addition of 1,25-(OH)2D3 to these populations inhibited proliferation, as measured by [3H]thymidine incorporation and soft agar colony assay. Furthermore, 1,25-(OH)2D3 caused a more rapid appearance of the CSF-1 receptor in early precursor cells in a dose-dependent metabolite-specific manner. Conversely, CSF-1 receptor expression was decreased in intermediate precursors treated with the steroid. This decrease in receptor expression was also dose dependent and metabolite specific. These findings demonstrate that 1,25-(OH)2D3 1) targets to authentic bone marrow macrophages at various stages of differentiation and 2) modulates expression of the CSF-1 receptor, a protein which, in turn, regulates monocytic maturation.

Mouse mesangial cells produce colony-stimulating factor-1 (CSF-1) and express the CSF-1 receptor.

Abstract CSF-1 stimulates the survival, proliferation, and differentiation of mononuclear phagocytes and may also play a role in placental development. The expression of CSF-1 and the CSF-1 receptor (CSF-1R) and their regulation were examined in cultures of mouse mesangial cells (MC). The concentration of CSF-1 in the medium of cultured MC increased linearly with time over 24 h. IFN-gamma stimulated and dibutyryl cyclic AMP inhibited CSF-1 production in a dose-dependent manner. MC expression of CSF-1 mRNA was shown by Northern blot analysis, and CSF-1 mRNA levels were increased within 4 h of IFN-gamma addition and inhibited within 4 h of dibutyryl cyclic AMP addition. Indirect immunofluorescence indicated that 90% of the untreated cultured MC expressed CSF-1. In addition, CSF-1R expression by MC was demonstrated by immunofluorescence with anti-receptor antibody, specific binding of [125I] CSF-1, and expression of the CSF-1R mRNA by Northern blot analysis. Thus, mouse MC, specialized pericytes of non-bone marrow origin, not only produce CSF-1 but also express receptors for CSF-1. The effects of CSF-1 on MC may be important in the control of immune function in the glomerulus.

Functional Expression of the Human Receptor for Colony-Stimulating Factor 1 (CSF-1) in Hamster Fibroblasts: CSF-1 Stimulates Na+/H+Exchange and DNA-Synthesis in the Absence of Phosphoinositide Breakdown

The human CSF-1 receptor (c-fms protooncogene product) was introduced into CSF-1-unresponsive Chinese hamster lung fibroblasts (CCL39 cell line) in order to study its coupling to biochemical signal-transducing systems and to compare the growth-regulating properties of CSF-1 to those of other growth factors. Independent clones expressing different levels of CSF-1 receptors were isolated and characterized. CSF-1 increased [3H]thymidine incorporation in serum-starved cells and potentiated the mitogenic effects of FGF and thrombin. As already observed for other growth factors activating receptor tyrosine kinases (EGF, FGF, IGF-I), CSF-1 alone did not trigger inositol phosphate formation, but slightly enhanced the activity of phospholipase C agonists (thrombin, A1F4- complex). Activation of the CSF-1 receptor by its ligand was evidenced by the rapid activation of the Na+/H+ exchanger resulting in amiloride-sensitive cytoplasmic alkalinization (0.1-0.2 pH units) within minutes after stimulation. Whereas pertussis toxin does not affect the action of EGF, FGF, or IGF-I in CCL39 cells, it partially inhibited both DNA synthesis reinitiation and activation of Na+/H+ exchange by CSF-1, indicating that the CSF-1 receptor can communicate with a signal-transducing GTP binding protein. A point-mutated form of the c-fms gene product, in which Tyr 969, a residue negatively modulating signal transduction, had been replaced with Phe [fms (F969)], did not generate responses significantly different from those obtained with the wild-type c-fms gene product. In the absence of CSF-1, cells expressing either wild-type or fms (F969) showed a considerably higher basal level of thymidine incorporation and decreased anchorage dependence compared with parental CCL39 cells. Monoclonal antibodies that interfere with signal transduction by the human CSF-1 receptor inhibited both basal [3H]thymidine incorporation and soft agar colony formation, indicating that relaxation of growth control was dependent on CSF-1 receptor expression.