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Biomedical subjects

E R Stanley

Publications and source records attributed to E R Stanley.

At least 19 recordsLinked to original sources
PubMed2000

The Drosophila shark tyrosine kinase is required for embryonic dorsal closure.

Dorsal closure (DC) in the Drosophila embryo requires the coordinated interaction of two different functional domains of the epidermal cell layer-the leading edge (LE) and the lateral epidermis. In response to activation of a conserved c-Jun amino-terminal kinase (JNK) signaling module, the dorsal-most layer of cells, which constitute the LE of the stretching epithelial sheet, secrete Dpp, a member of the TGFbeta superfamily. Dpp and other LE cell-derived signaling molecules stimulate the bilateral dorsal elongation of cells of the dorsolateral epidermis over the underlaying amnioserosa and the eventual fusion of their LEs along the dorsal midline. We have found that flies bearing a Shark tyrosine kinase gene mutation, shark(1), exhibit a DC-defective phenotype. Dpp fails to be expressed in shark(1) mutant LE cells. Consistent with these observations, epidermal-specific reconstitution of shark function or overexpression of an activated form of c-Jun in the shark(1) mutant background, rescues the DC defect. Thus, Shark regulates the JNK signaling pathway leading to Dpp expression in LE cells. Furthermore, constitutive activation of the Dpp pathway throughout the epidermis fails to rescue the shark(1) DC defect, suggesting that Shark may function in additional pathways in the LE and/or lateral epithelium.

Animals↗
PubMed2000

Regulation of mouse podocyte process dynamics by protein tyrosine phosphatases rapid communication.

BACKGROUND: Effacement of podocyte foot processes occurs early in many glomerular diseases associated with proteinuria and is accompanied by a reorganization of the actin cytoskeleton. The molecular mechanisms regulating these structural changes are poorly understood. METHODS: To address these questions, we analyzed the effect of the polycation, protamine sulfate (PS), and puromycin aminonucleoside (PA) on the morphology, cytoskeleton, and tyrosine phosphorylation of differentiated process-bearing cultured podocytes. RESULTS: PS and PA induced similar profound morphological alterations, including retraction and detachment of podocyte processes from the extracellular matrix (ECM). The effects of PS occurred within six hours, whereas PA showed its most severe effects after 72 hours. Structural changes included reorganization of the actin cytoskeleton and focal contacts and were accompanied by an increase in tyrosine phosphorylation. The same effects were induced by application of vanadate, an inhibitor of protein tyrosine phosphatases (PTPs), suggesting that PTPs regulate podocyte process structure. Since disruption of the actin cytoskeleton with cytochalasin B protected the cells from PS-induced effacement and detachment, cytoplasmic PTPs were implicated in these events. Using reverse transcription-polymerase chain reaction (RT-PCR), we demonstrated the expression of four cytoplasmic PTPs in podocytes: SHP-2, PTP-PEST, PTP-1B, and PTP-36. CONCLUSIONS: These studies indicate an important role for cytoplasmic PTPs as regulators of podocyte process dynamics. Future studies will aim at restoring the normal foot process architecture of podocytes in glomerular diseases associated with proteinuria by modulating the activity of cytoplasmic PTPs.

Actins↗
PubMed1999

SHP-1 regulation of p62(DOK) tyrosine phosphorylation in macrophages.

SHP-1 plays key roles in the modulation of hematopoietic cell signaling. To ascertain the impact of SHP-1 on colony-stimulating factor-1 (CSF-1)-mediated survival and proliferative signaling, we compared the CSF-1 responses of primary bone marrow macrophages (BMM) from wild-type and SHP-1-deficient motheaten (me/me) mice. CSF-1-induced protein tyrosine phosphorylation levels were similar in wild-type and me/me BMM, except for the constitutive hyperphosphorylation of a 62-kDa phosphoprotein (pp62) in me/me macrophages. pp62 was identified as the RASGAP-associated p62(DOK) and was shown to be the major CSF-1R-associated tyrosine-phosphorylated protein in CSF-1-treated BMM. p62(DOK) was found to be constitutively associated with SHP-1 in BMM and in 293T cells, co-expressing p62(dok) and either wild-type or catalytically inert SHP-1 (SHP-1 C453S). In both cell types, the interaction of SHP-1 with p62(DOK) occurred independently of p62(DOK) tyrosine phosphorylation, but only the tyrosine-phosphorylated p62(DOK) was bound by SHP-1 C453S in a far Western analysis. These findings suggest a constitutive association of SHP-1 and p62(DOK) that is either conformation-dependent or indirect as well as a direct, inducible association of the SHP-1 catalytic domain with tyrosine-phosphorylated p62(DOK). p62(DOK) hyperphosphorylation is not associated with altered CSF-1-induced RAS signaling or proliferation. However, whereas wild-type macrophages undergo cell death following CSF-1 removal, me/me macrophages exhibit prolonged survival in the absence of growth factor. Thus, p62(DOK) is a major SHP-1 substrate whose tyrosine phosphorylation correlates with growth factor-independent survival in macrophages.

Animals↗
PubMed1999

The Cbl protooncoprotein stimulates CSF-1 receptor multiubiquitination and endocytosis, and attenuates macrophage proliferation.

Colony-stimulating factor-1 (CSF-1) activation of the CSF-1 receptor (CSF-1R) causes Cbl protooncoprotein tyrosine phosphorylation, Cbl-CSF-1R association and their simultaneous multiubiquitination at the plasma membrane. The CSF-1R is then rapidly internalized and degraded, whereas Cbl is deubiquitinated in the cytoplasm without being degraded. We have used primary macrophages from gene-targeted mice to study the role of Cbl. Cbl-/- macrophages form denser colonies and, at limiting CSF-1 concentrations, proliferate faster than Cbl+/+ macrophages. Their CSF-1Rs fail to exhibit multiubiquitination and a second wave of tyrosine phosphorylation previously suggested to be involved in preparation of the CSF-1-CSF-1R complex for endocytosis. Consistent with this result, Cbl-/- macrophage cell surface CSF-1-CSF-1R complexes are internalized more slowly, yet are still lysosomally degraded, and the CSF-1 utilization by Cbl-/- macrophages is reduced approximately 2-fold. Thus, attenuation of proliferation by Cbl is associated with its positive regulation of the coordinated multiubiquitination and endocytosis of the activated CSF-1R, and a reduction in the time that the CSF-1R signals from the cell surface. The results provide a paradigm for studies of the mechanisms underlying Cbl attenuation of proliferative responses induced by ligation of receptor tyrosine kinases.

Animals↗
PubMed1999

CSF-1 stimulated multiubiquitination of the CSF-1 receptor and of Cbl follows their tyrosine phosphorylation and association with other signaling proteins.

Addition of colony stimulating factor-1 (CSF-1) to macrophages stimulates the rapid, transient tyrosine phosphorylation, membrane association and multiubiquitination of Cbl (Wang et al. [1996] J. Biol. Chem. 271:17-20). Kinetic analysis reveals that the tyrosine phosphorylation of Cbl is coincident with its plasma membrane translocation and association with the activated tyrosine phosphorylated CSF-1 R, p85, Grb2, and tyrosine phosphorylated p58Shc and that these events precede the simultaneous multiubiquitination of Cbl and the CSF-1 R. Tyrosine phosphorylation and multiubiquitination of the cell surface CSF-1 R are stoichiometric and the multiubiquitinated CSF-1 R is degraded. Similarly, the membrane associated Cbl is almost stoichiometrically ubiquitinated, but the ubiquitinated Cbl is not degraded, being recovered, deubiquitinated, in the cytosol 3-10 min after stimulation at 37 degrees C. In the membrane fraction of cells stimulated at 4 degrees C, the association of p58Shc and Grb2 with Cbl is stable, whereas its association with Sos and p85 is transient and their dissociation occurs at the time CSF-1 R and Cbl multiubiquitination commence. The membrane translocation and the pattern of association of Sos with the CSF-1R, p85, Grb2, and p58Shc resemble those of Cbl but Sos is not tyrosine phosphorylated, nor multiubiquitinated and the coprecipitation of these proteins, other than Grb2, with Sos is much less. Complexes formed by Sos and Cbl are largely independent and membrane complexes of Cbl with other tyrosine phosphorylated proteins, p85 and Grb2 also contain CSF-1 R. These data raise the possibility that the predicted negative regulatory role of Cbl in macrophages is its enhancement of ligand-induced CSF-1 R internalization/degradation.

Adaptor Proteins, Signal Transducing↗
PubMed1998

A novel macrophage actin-associated protein (MAYP) is tyrosine-phosphorylated following colony stimulating factor-1 stimulation.

An approximately 37-kDa cytoplasmic protein is rapidly tyrosine-phosphorylated in the response of mouse BAC1.2F5 macrophages to colony stimulating factor-1 (CSF-1). pp37 was purified from the cytosolic fraction by anti-Tyr(P) affinity chromatography, size exclusion chromatography, and C4 reverse phase high pressure liquid chromatography. The sequences of four peptides derived from the purified protein matched portions of an expressed sequence tag (EST) sequence, and the EST clone was used to obtain cDNA clones encoding the pp37 protein, which shares sequence similarity with the PST PIP (proline, serine, threonine phosphatase interacting protein)/CDC15 family of protein-tyrosine phosphatase substrates. pp37 is predicted to contain a Fes/CIP4 homology (FCH) domain and an actin-binding domain-like sequence. It is expressed selectively in macrophages, macrophage cell lines, and at low levels in macrophage-containing tissues. pp37 is predominantly found in the cytosol, where it is associated with actin. However, approximately 4% resides in the membrane fraction, and the trace amount in the cytoskeletal fraction is increased by CSF-1 stimulation. Termed macrophage actin-associated tyrosine-phosphorylated protein (MAYP), p37 is the major F-actin-associated protein that is tyrosine-phosphorylated in macrophages and is likely to play a role in regulating the CSF-1-induced reorganization of the actin cytoskeleton.

Actins↗
PubMed1998

The major SHP-1-binding, tyrosine-phosphorylated protein in macrophages is a member of the KIR/LIR family and an SHP-1 substrate.

The SH2 domain-containing cytoplasmic protein tyrosine phosphatase, SHP-1, negatively regulates hematopoietic cell signaling. SHP-1 is associated with a tyrosine phosphorylated, plasma membrane-spanning glycoprotein, pp130, in colony stimulating factor-1 stimulated or unstimulated macrophages. This association is phosphotyrosine dependent and is mediated by the amino-terminal SH2 domain of SHP-1. pp130 behaves as a substrate of SHP-1 in vitro and is hyperphosphorylated on tyrosine in SHP-1 deficient macrophages from viable-motheaten mice. Co-immunoprecipitation data indicate that pp130 is the product of the mouse p91/PIR-B gene that encodes a member of the killer cell inhibitory receptor (KIR)/leukocyte immunoglobulin-like receptor (LIR) family. By analogy to the KIRs, p91/PIR-B may represent a novel class of macrophage receptors which act to suppress macrophage activation. These observations identify SHP-1 interactions with and regulation of p91/PIR-B as a potential mechanism for inhibiting the signaling cascades linking extracellular stimuli to macrophage activation and/or development.

Amino Acid Sequence↗
PubMed1998

Colony-stimulating factor-1 stimulates the formation of multimeric cytosolic complexes of signaling proteins and cytoskeletal components in macrophages.

Stimulation of macrophages with colony-stimulating factor-1 (CSF-1) results in the protein tyrosine phosphorylation of the CSF-1 receptor (CSF-1R) and many other, primarily cytosolic, proteins. Stimulation by CSF-1 at 4 degreesC was used to facilitate the purification and identification of the proteins of the cytosolic anti-phosphotyrosine (PY)-reactive fraction (alphaPY-RF) involved in downstream signaling pathways. Confocal microscopy revealed that the PY proteins are in close proximity to the CSF-1R at the plasma membrane. The alphaPY-RF contained pre-existing complexes of PY proteins and non-PY proteins which generally increased in size and PY protein content following CSF-1 stimulation. PY proteins identified by microsequencing and Western blotting include Cbl, STAT3, STAT5a, STAT5b, SHP-1, Shc, and two novel proteins pp57 and pp37. Other proteins included cytoskeletal/contractile proteins (paxillin, vimentin, elongation factor-1alpha, F-actin, tropomyosin, and myosin regulatory light chain), Ras family signaling proteins (p85 (phosphoinositide 3-kinase), Vav, Ras-GTPase-activating protein SH3 domain-binding protein, and Grb2), DnaJ-like protein, and glyceraldehyde-3-phosphate dehydrogenase. CSF-1 induced the de novo recruitment of Cbl, STAT3, STAT5a, STAT5b, p85, SHP-1, Shc, vimentin, and Grb2 to complexes and caused pre-existing complexes involving Vav, elongation factor-1alpha, and F-actin to increase in size. These studies indicate that CSF-1-induced protein tyrosine phosphorylation is associated with the reorganization of complexes of cytoskeletal, signaling, and other proteins that mediate CSF-1-regulated motility and growth.

Actins↗
PubMed1998

The effects of colony-stimulating factor-1 on the distribution of mononuclear phagocytes in the developing osteopetrotic mouse.

Colony-stimulating factor-1 (CSF-1), the primary regulator of mononuclear phagocyte (Mphi) production, exists as either a circulating or cell surface, membrane-spanning molecule. To establish transplacental transfer of maternal CSF-1, gestational day-17 mothers were injected intravenously with 125I-mouse CSF-1 or human rCSF-1, and the 125I-cpm or human CSF-1 concentrations were measured in fetal tissue, placenta, and fetal/maternal sera. Biologically active CSF-1 crossed the placenta and peaked in fetal tissue, placenta, and serum 10 minutes after injection. The role of CSF-1 in perinatal Mphi development was examined by studying the CSF-1-deficient osteopetrotic (csfmop/csfmop) mouse. Fetal/neonatal mice, derived from matings of either +/csfmop females with csfmop/csfmop males or the reciprocal pairings, were genotyped and tissue Mphi identified and quantified. In the presence of circulating maternal CSF-1 (+/csfmop mother), Mphi development in csfmop/csfmop liver was essentially complete at birth relative to +/csfmop littermates, but significantly reduced in spleen, kidney, and lung. In the absence of circulating maternal CSF-1 (csfmop/csfmop mother), Mphi numbers at birth were reduced in csfmop/csfmop liver relative to the offspring of +/csfmop mothers, but were similar in spleen, kidney, and lung. We conclude that CSF-1 is required for the perinatal development of most Mphi in these tissues. Compensation for total absence of local CSF-1 production by circulating, maternal CSF-1 is tissue-specific and most prominent in liver, the first fetal organ perfused by placental blood. However, because some Mphi developed in the complete absence of CSF-1, other factors must also be involved in the regulation of macrophage development.

Animals↗
PubMed1998

Synthesis and breakdown of fibrillar collagens: concomitant phenomena in ovarian cancer.

The synthesis and degradation of type I and type III interstitial collagens releases several antigenic metabolites, whose measurement allows the metabolism of connective tissue to be evaluated under a variety of different conditions. In this study we investigated the influence of benign and malignant ovarian neoplasms on the metabolism of these collagens. The study population comprised patients with benign (n = 53), borderline (n = 6) or malignant (n = 36) ovarian neoplasms. We quantified the serum, cyst fluid and peritoneal/ascitic fluid concentrations of the amino-terminal propeptide of type I (PINP) and III (PIIINP) procollagens, indicators of the synthesis of type I and III collagen, respectively and the cross-linked carboxy-terminal telopeptide of type I collagen (ICTP), an indicator of type I collagen degradation. Macrophage colony-stimulating factor 1 (CSF-1) concentration was also assayed as its serum level is increased in ovarian cancer and CSF-1 may be involved in the regulation of collagen metabolism. The concentration of each antigen was significantly higher in patients with malignant tumour than with benign neoplasm in each comparison, except for ICTP in peritoneal fluid and for CSF-1 in cyst fluid. The high ascitic fluid concentration of PINP, PIIINP or CSF-1 correlated with malignancy, and the low cyst fluid concentration of any of the four markers was indicative of benign tumour. Levels of CSF-1 did not correlate with the levels of any of the markers of collagen turnover. The concentration of PINP in ascites was about 50 times higher and in cyst fluid about eight times higher than that in the serum from patients with malignant tumour, whereas the respective ratios for ICTP were only 2.5 and 1.3. In such patients, the ratio of ascitic fluid to serum concentration was also about 80-fold higher for PIIINP and about 20-fold higher for PINP than for ICTP. The different distributions of PIIINP, PINP and ICTP suggests dominance of synthetic processes or retarded elimination of PIIINP and PINP in ovarian cancer. In advanced malignancies, the accumulation of PINP and PIIINP in abdominal space, possibly due to increased synthesis and/or failed resorption, may promote ascites formation. This study shows that both accelerated synthesis and breakdown of fibrillar collagens are characteristic of ovarian malignancy, and suggests that measurements of cyst fluid or ascitic fluid concentrations of collagen metabolites or CSF-1 could be used in the differential diagnosis of benign and malignant ovarian neoplasms.

Adult↗
PubMed1997

Lipopolysaccharide induces synthesis of mouse colony-stimulating factor-1 in vivo.

CSF-1 is a hemopoietic growth factor that regulates the survival, proliferation, and differentiation of mononuclear phagocytes, cells that are critical in the inflammatory response. In the case of Gram-negative infection, LPS plays an important role by inducing several cell types to produce the proinflammatory cytokines, IL-1, IL-6, and TNF-alpha. In this study, we examined the effects of i.p. administration of LPS on CSF-1 expression in the mouse. Two- to sevenfold increases in the CSF-1 concentrations determined by RIA were evident within hours of LPS administration in serum, liver, kidney, lung, spleen, brain, intestine, and heart. While alterations in the CSF-1 receptor-mediated clearance of CSF-1 appeared not to account for the increased growth factor concentrations in LPS-treated animals, there was an early LPS-induced reduction of splenic [125I]CSF-1 uptake consistent with tissue-specific down-modulation of CSF-1 receptors. The results of Northern analysis revealed increased expression of a CSF-1 mRNA species in liver, lung, kidney, spleen, intestine, and heart following LPS treatment, demonstrating that increased synthesis was responsible for the increased tissue CSF-1 concentrations. The increased expression and synthesis of CSF-1 in response to LPS may be essential for mobilizing and activating mononuclear phagocytes in the inflammatory response.

Animals↗
PubMed1997

Increased circulating colony-stimulating factor-1 (CSF-1) in SJL/J mice with radiation-induced acute myeloid leukemia (AML) is associated with autocrine regulation of AML cells by CSF-1.

The SJL/J mouse strain has a high spontaneous incidence of a B-cell neoplasm, reticulum cell neoplasm type B (RCN B). In addition, following irradiation, 10% to 30% of these mice develop acute myelomonocytic leukemia (radiation-induced acute myeloid leukemia [RI-AML]), an incidence that can be increased to 50% by treatment of the mice with corticosteroids after irradiation. The role played by the mononuclear phagocyte growth factor, colony-stimulating factor-1 (CSF-1), in the development of RI-AML in SJL/J mice was investigated. Mice dying of RI-AML, but not those dying of RCN B or without disease, possessed elevated concentrations of circulating CSF-1. In addition, in mice developing RI-AML with a more prolonged latency, circulating CSF-1 concentrations were increased before overt expression of RI-AML. First-passage tumors from 14 different RI-AMLs all contained high concentrations of CSF-1, and six of six different first- or second-passage tumors expressed the CSF-1 receptor (CSF-1 R). Furthermore, in vitro colony formation by first- or second-passage tumor cells from 20 of 20 different RI-AMLs was blocked by neutralizing anti-CSF-1 antibody, and four of four of these tumors were inhibited by anti-CSF-1R antibody. The results of these antibody neutralization studies, coupled with the observation of elevated circulating CSF-1 in mice developing RI-AML, show an autocrine role for CSF-1 in RI-AML development in SJL/J mice. Southern blot analysis of tumor DNA from six of six of these tumors failed to reveal any rearrangements in the genes for CSF-1 or the CSF-1R. Studies in humans have shown that patients with AML possess elevated levels of circulating CSF-1 and that AML cells can express CSF-1 and the CSF-1R. Thus, RI-AML in the SJL/J mouse appears to be a useful model for human AML.

Acute Disease↗
PubMed1997

Biology and action of colony--stimulating factor-1.

Colony-stimulating factor-1 (CSF-1), also known as macrophage colony-stimulating factor, controls the survival, proliferation, and differentiation of mononuclear phagocytes and regulates cells of the females reproductive tract. It appears to play an autocrine and/or paracrine role in cancers of the ovary, endometrium, breast, and myeloid and lymphoid tissues. Through alternative mRNA splicing and differential post-translational proteolytic processing, CSF-1 can either be secreted into the circulation as a glycoprotein or chondroitin sulfate-containing proteoglycan or be expressed as a membrane-spanning glycoprotein on the surface of CSF-1-producing cells. Studies with the op/op mouse, which possesses an inactivating mutation in the CSF-1 gene, have established the central role of CSF-1 in directly regulating osteoclastogenesis and macrophage production. CSF-1 appears to preferentially regulate the development of macrophages found in tissues undergoing active morphogenesis and/or tissue remodeling. These CSF-1 dependent macrophages may, via putative trophic and/or scavenger functions, regulate characteristics such as dermal thickness, male fertility, and neural processing. Apart from its expression on mononuclear phagocytes and their precursors, CSF-1 receptor (CSF-1R) expression on certain nonmononuclear phagocytic cells in the female reproductive tract and studies in the op/op mouse indicate that CSF-1 plays important roles in female reproduction. Restoration of circulating CSF-1 to op/op mice has preliminarily defined target cell populations that are regulated either humorally or locally by the synthesis of cell-surface CSF-1 or by sequestration of the CSF-1 proteoglycan. The CSF-1R is a tyrosine kinase encoded by the c-fms proto-oncogene product. Studies by several groups have used cells expressing either the murine or human CSF-1R in fibroblasts to pinpoint the requirement of kinase activity and the importance of various receptor tyrosine phosphorylation sites for signaling pathways stimulated by CSF-1. To investigate post-CSF-1R signaling in the macrophage, proteins that are rapidly phosphorylated on tyrosine in response to CSF-1 have been identified, together with proteins associated with them. Studies on several of these proteins, including protein tyrosine phosphates 1C, the c-cbl proto-oncogene product, and protein tyrosine phosphatase-phi are discussed.

Animals↗
PubMed1997

Effect of the colony-stimulating factor-1 null mutation, osteopetrotic (csfm(op)), on the distribution of macrophages in the male mouse reproductive tract.

Macrophages are found throughout the male reproductive tract and its accessory glands. Mice homozygous for a null mutation (csfm(op)) in the gene for the mononuclear phagocytic growth factor colony-stimulating factor-1 (CSF-1) have a significantly lower density of macrophages, defined by the mononuclear phagocytic antigen F4/80, in the testis, cauda and caput epididymis, prostate, seminal vesicles, and vas deferens. These data indicate that CSF-1 is the major growth factor regulating the occurrence of macrophages in male reproductive tissues. The residual macrophages were correctly located in the tissue except in the caput epididymis, where they failed to take up positions adjacent to the tubular epithelium. Restoration of circulating CSF-1 concentrations in csfm(op)/csfm(op) males totally restored F4/80+ cell density in the testis and caput and cauda epididymis and partially restored their density in the vas deferens and seminal vesicles but failed to affect density in the prostate. This failure to correct all populations with circulating CSF-1 suggests the requirement for local synthesis of CSF-1 at appropriate developmental stages and/or its expression in a cell surface-associated form. The absence of macrophages in the testis and epididymis of csfm(op)/csfm(op) mice correlates with dysfunction in these tissues, suggesting that macrophages play important nonimmunological roles in these tissues.

Animals↗
PubMed1996

Dietary n-3 fatty acids increase spleen size and postendotoxin circulating TNF in mice; role of macrophages, macrophage precursors, and colony-stimulating factor-1.

In experimental studies in mice, dietary supplementation with n-3 fatty acids (FA) alleviates inflammation and increases resistance to infection. Nevertheless, TNF production capacity was found to be increased in n-3 FA-fed mice. We previously found increased relative spleen weights in n-3 FA-fed mice. In this study, the nature of this increased spleen size was further investigated. Spleen cellularity was increased significantly in mice fed n-3 FA (fish oil 15% w/w), compared with controls fed corn oil (15%) or normal lab chow (p < 0.05). Experiments with T cell-deficient nude mice and experiments using macrophage depletion through liposomal dichloromethylene-biphosphonate revealed that the increase in spleen cellularity is T cell independent and largely due to macrophage accumulation in the spleen. Accumulation of marginal zone and red pulp macrophages was histologically and immunohistochemically confirmed. n-3 FA induced peripheral blood monocytosis and an aspecific increase in bone marrow cellularity. Postendotoxin circulating TNF concentrations were increased significantly in n-3 FA-fed mice compared with controls. Splenectomy did not abolish this increase in circulating TNF. However, after macrophage depletion through liposomal dichloromethylene-biphosphonate, circulating TNF was not detectable after endotoxin challenge. Circulating concentrations of CSF-1 did not differ between the various experimental groups. It is suggested that the cellular changes observed relate to increased constitutive production of TNF.

Animals↗
PubMed1996

c-Cbl is transiently tyrosine-phosphorylated, ubiquitinated, and membrane-targeted following CSF-1 stimulation of macrophages.

Early colony stimulating factor-1 (CSF-1)-induced changes in the behavior of p120c-cbl in mouse BAC1.2F5 macrophages were investigated. p120c-cbl is associated with Grb2 in the cytoplasm of unstimulated cells. Following a 1-min stimulation with CSF-1, p120c-cbl becomes tyrosine-phosphorylated and associates with tyrosine-phosphorylated Shc and an unknown phosphotyrosyl protein (pp80). Simultaneously, it is ubiquitinated and translocated to the membrane. By 10 min of stimulation, this c-Cbl exhibits substantially decreased tyrosine phosphorylation and is de-ubiquitinated and relocated in the cytosol. However, the association of p120c-cbl with Shc persists for at least 60 min. These data indicate that signaling via the CSF-1R involves the transient modification of p120c-cbl and its recruitment as a complex to membrane.

Animals↗