06-174 Sigma-AldrichAnti-Fms/CSF-1 Receptor Antibody, extracellular domain

Gastrointestinal (GI) homeostasis requires the action of multiple pathways. There is some controversy regarding whether small intestine (SI) Paneth cells (PCs) play a central role in orchestrating crypt architecture and their relationship with Lgr5+ve stem cells. Nevertheless, we previously showed that germline CSF-1 receptor (Csf1r) knock out (KO) or Csf1 mutation is associated with an absence of mature PC, reduced crypt proliferation and lowered stem cell gene, Lgr5 expression. Here we show the additional loss of CD24, Bmi1 and Olfm4 expression in the KO crypts and a high resolution 3D localization of CSF-1R mainly to PC. The induction of GI-specific Csf1r deletion in young adult mice also led to PC loss over a period of weeks, in accord with the anticipated long life span of PC, changed distribution of proliferating cells and this was with a commensurate loss of Lgr5 and other stem cell marker gene expression. By culturing SI organoids, we further show that the Csf1r(-/-) defect in PC production is intrinsic to epithelial cells as well as definitively affecting stem cell activity. These results show that CSF-1R directly supports PC maturation and that in turn PCs fashion the intestinal stem cell niche.

Colony stimulating factor-1 (CSF-1) and its receptor (CSF-1R) are key regulators of macrophage biology, and their elevated expression in cancer cells has been linked to poor prognosis. CSF-1Rs are thought to function at the plasma membrane. We show here that functional CSF-1Rs are present at the nuclear envelope of various cell types, including primary macrophages, human cancer cell lines, and primary human carcinomas. In response to CSF-1, added to intact cells or isolated nuclei, nucleus-associated CSF-1R became phosphorylated and triggered the phosphorylation of Akt and p27 inside the nucleus. Extracellularly added CSF-1 was also found to colocalize with nucleus-associated CSF-1Rs. All these activities were found to depend selectively on the activity of the p110δ isoform of phosphoinositide 3-kinase (PI3K). This finding was related to the p110δ-dependent translocation of exogenous CSF-1 to the nucleus-associated CSF-1Rs, correlating with a prominent role of p110δ in activation of the Rab5 GTPase, a key regulator of the endocytic trafficking. siRNA-silencing of Rab5a phenocopied p110δ inactivation and nuclear CSF-1 signaling. Our work demonstrates for the first time the presence of functional nucleus-associated CSF-1Rs, which are activated by extracellular CSF-1 by a mechanism that involves p110δ and Rab5 activity. These findings may have important implications in cancer development.

Colony-stimulating factor-1 (CSF-1), released by osteoblasts, stimulates the proliferation of osteoclast progenitors via the c-fms receptor (CSF-1R) and, in combination with receptor activator of nuclear factor-kappaB ligand (RANKL), leads to the formation of mature osteoclasts. Whether the CSF-1R is expressed by osteoblasts and mediates specific biological effects in osteoblasts has not been explored. Wild-type primary calvaria osteoblasts (OB) were analyzed for CSF-1R expression (RT-PCR and Western blot) and functionality (immunocomplex kinase assay). OB were serum starved for 24 h, and the effect of CSF-1 (0-100 ng/ml) on OB biological activities was determined at 48 h. In wild-type mouse bone marrow cultures, CSF-1 was tested for its effect on RANKL mRNA and osteoclast formation. Because ROS influence osteoblast RANKL expression, studies analyzed the effect of CSF-1 on reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and Nox1 and Nox4 proteins. Results indicate that OB express CSF-1R mRNA and protein and that CSF-1R could be phosphorylated in the presence of CSF-1. In osteoblasts, CSF-1 decreased RANKL mRNA in a dose- and time-dependent manner. Incubation of bone marrow cultures with CSF-1 resulted in a significant decline in tartrate-resistant acid phosphatase (TRACP) activity and CTR expression. RANKL-decreased expression by CSF-1 was correlated with a decrease of NADPH oxidase activity as well as Nox1 and Nox4 protein levels. These findings provide the first evidence that osteoblasts express CSF-1R and are a target for CSF-1 ligand. CSF-1-mediated inhibition of RANKL expression on osteoblasts may provide an important mechanism for coupling bone formation/resorption and preventing excessive osteoclastogenesis during normal skeletal growth.

Infiltration of leukocytes into tissue is a common feature of many physiological and pathological conditions. Histopathologically, the diversity of leukocytes that infiltrate a tissue associated with a pathophysiologic response cannot be appreciated and/or examined unless highly selective immunologic detection methods are utilized. Specific populations of infiltrating leukocytes into squamous tissues harboring pre-malignant and/or malignant keratinocytes have recently been demonstrated to play a functionally significant role in the pathogenesis of squamous carcinomas. To evaluate immune cell types and quantify changes in their relative presence and localization during multi-stage neoplastic progression, we performed flow cytometry and histochemical detection using lineage-selective markers. Herein, we provide detailed methodology facilitating these analyses.

A number of recent studies have suggested that the colony-stimulating factor (CSF-1) and its receptor c-fms may be involved in the development of mammary glands during lactation and breast cancer. To study the role of CSF-1 or its receptor in initiation of mammary tumorigenesis, we have generated two independent lines of transgenic mice that overexpress either CSF-1 or c-fms under the control of the mouse mammary tumor virus promoter. Mammary glands of the virgin CSF-1 transgenic mice show increased ductal branching, hyperplasia, dysplasia, and other preneoplastic changes, which are indicative of increased cellular proliferation. Similar changes were also evident in the mammary glands of the c-fms transgenic mice. These changes became more prominent with age and resulted in mammary tumor formation. Moreover, secondary events like dimethylbenz(a)anthracene treatment accelerated mammary tumor formation in these mice. Although the expression of estrogen receptor alpha was not significantly changed in either of the transgenic mouse strains, progesterone receptor levels was higher in both transgenic lines as compared with the nontransgenic littermates. Expression of G1 cyclins was prominently increased in the mammary glands of both the CSF-1 and c-fms transgenic lines, suggesting increased cell cycle progression in these strains. In addition, the proliferation marker proliferating cell nuclear antigen (PCNA) and the mitogen-responsive transcription factor c-jun were also increased as compared with the nontransgenic controls. These findings, along with the histological data, support the hypothesis that CSF-1 and its receptor are involved in the etiology of breast cancer.

To investigate whether the c-fms proto-oncogene plays a role in the CNS, we examined its expression in mouse brain. We found that c-fms-positive Purkinje cells first appeared in caudal cerebellum at postnatal day 0 (P0) arranged in a parasagittal manner, and most Purkinje cells gradually became positive by P6. This differential expression was not seen from P7 to adulthood, and the parasagittal pattern until P5 was different from those of L7, zebrins, and the integrin beta1 subunit. No neuronal expression of c-fms was found in the other brain regions examined. In both reeler and weaver mutant mice in the adult stage, all Purkinje cells were positive for c-fms as in the wild-type controls; however, the parasagittal bands of c-fms-positive Purkinje cells were observed even in the adult staggerer mutant. To check the neurotrophic effect of macrophage colony-stimulating factor (M-CSF), we immunostained cerebella derived from osteopetrotic mutant mice, that is, those devoid of active M-CSF. We found that the number of calbindin-positive Purkinje cells in a given cerebellum began to decrease substantially during the initial 4-5 weeks of the postnatal period. In addition, cultured Purkinje cells were dependent on M-CSF for their survival. These data suggest that expression of the c-fms gene is intrinsically programmed in the Purkinje cells and never affected by the afferent synaptic input and that neuronal survival of Purkinje cells is dependent on M-CSF after weaning. Therefore, c-fms is considered to be a new developmental marker for Purkinje cells.

Oncogenic activation of the macrophage colony stimulating factor (M-CSF) receptor (c-Fms) requires mutation or truncation of the carboxyl terminus and specific amino acid substitutions in or near the fourth immunoglobulin (Ig)-like loop in the extracellular domain. Using a murine c-Fms system, we investigated the effect of C-terminal truncation, substitutions at amino acids 301 and 374 in the fourth Ig-like loop of the extracellular domain, or the combined mutations on individual steps in receptor activation. The mutations at amino acids 301 and 374 were necessary, but not sufficient, for receptor dimerization in the absence of M-CSF. Only receptors with a truncated C-terminus as well as the extracellular domain mutations dimerized efficiently in the absence of M-CSF, suggesting that the C-terminus of c-Fms also regulates receptor oligomerization. Truncation of the C-terminus alone did not cause receptor dimerization and did not activate the kinase enzymatic activity. Thus, truncation of the C-terminus did not activate receptor monomers in cis. Receptors with both a truncated C-terminus and the extracellular domain mutations underwent ligand-independent aggregation, transphosphorylation, and phosphorylation of cellular proteins, followed by rapid internalization and degradation. These results suggest that M-CSF binding to c-Fms initiates activation by inducing conformational changes in both the cytoplasmic C-terminal domain and the fourth Ig-like loop of the extracellular domain, leading to the formation of stable receptor dimers.