Transmembrane Tumor Necrosis Factor (TNF)-α Inhibits Adipocyte Differentiation by Selectively Activating TNF Receptor 1

Tumor necrosis factor α (TNFα) is a potent cytokine with multiple biological activities and exists in two forms as follows: a 17-kDa soluble form that is a cleaved product of the 26-kDa transmembrane form (mTNFα). It has been suggested that the transmembrane form of TNFα is mainly responsible for localized responses via cell-cell contact. Here, we have examined the activities of transmembrane TNFα in cultured adipocytes. A non-cleavable transmembrane form of TNFα (mTNFΔ1–9K11E) was expressed in several preadipocyte cell lines using retroviral gene transfer. In wild type preadipocytes carrying both TNF receptors, expression of mTNFΔ1–9K11E resulted in inhibition of the differentiation program. The extent of this varied depending on the nature and strength of the adipogenic stimuli. The TNF receptor responsible for this function was determined by expressing mTNFΔ1–9K11E in preadipocyte cell lines lacking either TNF receptor 1 (TNFR1), 2 (TNFR2), or both. In order to confirm the results in the same cellular background, TNF receptors were also reconstituted in the cell lines lacking corresponding receptors. These experiments demonstrated that TNFR1 was necessary and sufficient for mediating mTNFΔ1–9K11E-induced inhibition of adipogenesis and that this action was similar to that of soluble TNFα. In conclusion, our results indicate that mTNFΔ1–9K11E is biologically active in cultured adipocytes and can alter the adipogenic program of these cells by selectively activating TNFR1. This may have physiological implications where local TNFα actions are thought to be generated at sites such as adipose tissue. Tumor necrosis factor α (TNFα) is a potent cytokine with multiple biological activities and exists in two forms as follows: a 17-kDa soluble form that is a cleaved product of the 26-kDa transmembrane form (mTNFα). It has been suggested that the transmembrane form of TNFα is mainly responsible for localized responses via cell-cell contact. Here, we have examined the activities of transmembrane TNFα in cultured adipocytes. A non-cleavable transmembrane form of TNFα (mTNFΔ1–9K11E) was expressed in several preadipocyte cell lines using retroviral gene transfer. In wild type preadipocytes carrying both TNF receptors, expression of mTNFΔ1–9K11E resulted in inhibition of the differentiation program. The extent of this varied depending on the nature and strength of the adipogenic stimuli. The TNF receptor responsible for this function was determined by expressing mTNFΔ1–9K11E in preadipocyte cell lines lacking either TNF receptor 1 (TNFR1), 2 (TNFR2), or both. In order to confirm the results in the same cellular background, TNF receptors were also reconstituted in the cell lines lacking corresponding receptors. These experiments demonstrated that TNFR1 was necessary and sufficient for mediating mTNFΔ1–9K11E-induced inhibition of adipogenesis and that this action was similar to that of soluble TNFα. In conclusion, our results indicate that mTNFΔ1–9K11E is biologically active in cultured adipocytes and can alter the adipogenic program of these cells by selectively activating TNFR1. This may have physiological implications where local TNFα actions are thought to be generated at sites such as adipose tissue. tumor necrosis factor α secreted tumor necrosis factor α wild type transmembrane tumor necrosis factor α TNF receptor peroxisome proliferator-activated receptor γ a non-cleavable murine TNFα mutant Dulbecco's modified Eagle's medium phosphate-buffered saline lipopolysaccharide wild type Originally identified as a mediator of necrosis of certain tumor cells, tumor necrosis factor α (TNFα)1 has now been shown to have a wide array of biological activities (1Beutler B. Cerami A. Annu. Rev. Immunol. 1989; 7: 625-655Crossref PubMed Scopus (1494) Google Scholar, 2Grunfeld C. Feingold K.R. Biotherapy. 1991; 3: 143-158Crossref PubMed Scopus (171) Google Scholar). It is also implicated in the pathogenesis of several diseases such as septic shock, rheumatoid arthritis, autoimmune disorders, and insulin resistance (1Beutler B. Cerami A. Annu. Rev. Immunol. 1989; 7: 625-655Crossref PubMed Scopus (1494) Google Scholar, 3Hotamisligil G.S. Spiegelman B.M. Diabetes. 1994; 43: 1271-1278Crossref PubMed Google Scholar). TNFα is primarily produced by activated macrophages and lymphocytes but is also expressed in endothelial cells and other cell types including adipocytes (1Beutler B. Cerami A. Annu. Rev. Immunol. 1989; 7: 625-655Crossref PubMed Scopus (1494) Google Scholar, 2Grunfeld C. Feingold K.R. Biotherapy. 1991; 3: 143-158Crossref PubMed Scopus (171) Google Scholar, 4Hotamisligil G.S. Shargill N.S. Spiegelman B.M. Science. 1993; 259: 87-91Crossref PubMed Scopus (6088) Google Scholar). It exists in two forms as follows: a 17-kDa soluble form (sTNFα) that is cleaved from the 26-kDa transmembrane protein (mTNFα) at the cell surface by TNFα-converting enzyme (5Moss M.L. Jin S.L. Milla M.E. Burkhart W. Carter H.L. Chen W.J. Clay W.C. Didsbury J.R. Hassler D. Hoffman C.R. Kost T.A. Lambert M.H. Leesnitzer M.A. McCauley P. McGeehan G. Mitchell J. Moyer M. Pahel G. Rocque W. Overton L.K. Schoenen F. Seaton T. Su J.L. Warner J. Becherer J.D. Nature. 1997; 385: 733-736Crossref PubMed Scopus (1476) Google Scholar, 6Kriegler M. Ferez C. DeFay K. Albert I. Lu S.D. Cell. 1988; 53: 45-53Abstract Full Text PDF PubMed Scopus (930) Google Scholar). Although the majority of TNFα-induced responses has been attributed to sTNFα, a few studies have shown that mTNFα is also biologically active and capable of mediating similar responses including apoptosis, proliferation, B cell activation, and some inflammatory responses (7Grell M. Douni E. Wajant H. Lohden M. Clauss M. Maxeiner B. Georgopoulos S. Lesslauer W. Kollias G. Pfizenmaier K. Schearich P. Cell. 1995; 83: 793-802Abstract Full Text PDF PubMed Scopus (1151) Google Scholar, 8Decoster E. Vanhaesebroeck B. Vandenabeele P. Grooten J. Fiers W. J. Biol. Chem. 1995; 270: 18473-18478Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar). Furthermore, mTNFα has been implicated in some disease states such as experimental hepatitis where serum sTNFα levels were found to be within the normal range (9Kusters S. Tiegs G. Alexopoulou L. Pasparakis M. Douni E. Kunstle G. Bluethmann H. Wendel A. Pfizenmaier K. Kollias G. Grell M. Eur. J. Immunol. 1997; 27: 2870-2875Crossref PubMed Scopus (173) Google Scholar), indicating the relevance of localized TNFα responses. The existence of two different forms of TNFα makes its physiology more complicated. Furthermore, the fact that mTNFα relies on cell contact-dependent signaling may render the actions of mTNFα cell type-specific in vivo. In support of this, mTNFα has been reported to trigger inflammatory responses in astrocytes but not in neurons, whereas sTNFα can induce similar effects in both cell types (10Akassoglou K. Probert L. Kontogeorgos G. Kollias G. J. Immunol. 1997; 158: 438-445PubMed Google Scholar). The biological functions of both mTNFα and sTNFα can be signaled by two distinct TNF receptors: TNFR1 (55 kDa) and TNFR2 (75 kDa). The lack of homology in intracellular domains of two TNF receptors indicates that they can mediate distinct biological activities. Indeed, whereas a broad array of cellular responses has been attributed to TNFR1, many other effects are mediated by TNFR2 (11Tartaglia L.A. Goeddel D.V. Immunol. Today. 1992; 13: 151-153Abstract Full Text PDF PubMed Scopus (1002) Google Scholar, 12Grell M. J. Inflammat. 1995; 47: 8-17PubMed Google Scholar). These two receptors can also act in concert under many circumstances (9Kusters S. Tiegs G. Alexopoulou L. Pasparakis M. Douni E. Kunstle G. Bluethmann H. Wendel A. Pfizenmaier K. Kollias G. Grell M. Eur. J. Immunol. 1997; 27: 2870-2875Crossref PubMed Scopus (173) Google Scholar, 13Lazdins J.K. Grell M. Walker M.R. Woods-Cook K. Scheurich P. Pfizenmaier K. J. Exp. Med. 1997; 185: 81-90Crossref PubMed Scopus (62) Google Scholar). The role of TNFR1 and TNFR2 in mediating the actions of sTNFα and the downstream signaling mechanisms has been studied extensively. In contrast, little information is available regarding the pathways and mechanisms utilized by mTNFα. Some early studies have demonstrated that transmembrane TNFα is superior to sTNFα in activating TNFR2 (7Grell M. Douni E. Wajant H. Lohden M. Clauss M. Maxeiner B. Georgopoulos S. Lesslauer W. Kollias G. Pfizenmaier K. Schearich P. Cell. 1995; 83: 793-802Abstract Full Text PDF PubMed Scopus (1151) Google Scholar, 12Grell M. J. Inflammat. 1995; 47: 8-17PubMed Google Scholar). However, subsequent reports have indicated that transmembrane TNFα can signal through both receptors depending on the cellular context (8Decoster E. Vanhaesebroeck B. Vandenabeele P. Grooten J. Fiers W. J. Biol. Chem. 1995; 270: 18473-18478Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar). Other studies have to that both receptors were as in the of experimental hepatitis (9Kusters S. Tiegs G. Alexopoulou L. Pasparakis M. Douni E. Kunstle G. Bluethmann H. Wendel A. Pfizenmaier K. Kollias G. Grell M. Eur. J. Immunol. 1997; 27: 2870-2875Crossref PubMed Scopus (173) Google and L. Pasparakis M. Kollias G. Eur. J. Immunol. 1997; 27: PubMed Scopus Google Scholar), whereas TNFR2 is sufficient to mediate the effects of transmembrane TNF in experimental P. E. M. D. C. C. T. Fiers W. Bluethmann H. Eur. J. Immunol. 1997; 27: PubMed Scopus Google Scholar). TNFα role in of It has effects on including of and inhibition of insulin action C. Feingold K.R. Biotherapy. 1991; 3: 143-158Crossref PubMed Scopus (171) Google Scholar, 3Hotamisligil G.S. Spiegelman B.M. Diabetes. 1994; 43: 1271-1278Crossref PubMed Google Scholar). In can the expression of several G.S. Shargill N.S. Spiegelman B.M. Science. 1993; 259: 87-91Crossref PubMed Scopus (6088) Google and the of and active in G.S. A. D. Spiegelman B.M. J. 1994; PubMed Scopus Google Scholar, G.S. J. 1997; PubMed Scopus Google Scholar). studies demonstrated that TNFα is a mediator of insulin resistance in The expression of TNFα in adipose is in a of G.S. Shargill N.S. Spiegelman B.M. Science. 1993; 259: 87-91Crossref PubMed Scopus (6088) Google and also in G.S. P. Spiegelman B.M. J. 1995; PubMed Scopus Google Scholar, M. J. 1995; PubMed Scopus Google Scholar). TNFα has been shown to insulin action in cultured adipocytes G.S. Spiegelman B.M. S. A. 1994; PubMed Scopus Google and other cell types H. B. A. J. Biol. Chem. 1993; Full Text PDF PubMed Google Scholar, G. B. M. E. B. A. L. H. A. H. 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It is that be where TNFα action is localized to the of such as adipose tissue. mTNFα may be a mediator of such local However, the effects of mTNFα on and In this we have examined the effects of transmembrane TNFα on cultured adipocytes and determined the TNF receptor responsible for its functions by using and preadipocyte cell lines in our K. H. K. T. S. M. L. and G. for K. H. K. T. S. M. L. and G. for These studies that transmembrane TNFα is biologically active in cultured adipocytes and that the differentiation program of adipocytes by selectively activating TNFR1. and cell lines were from with in the corresponding using the cell lines were for and for to adipocytes. cell with the of differentiation was and for the and preadipocytes were in Dulbecco's modified Eagle's medium with serum cells were in the same medium in the of cells were at on in with serum were to and to adipogenic for to by for more in medium insulin murine soluble TNFα were at and the experiments with a 2 at the indicated were either with for or for insulin was at a of at 1 at and at 1 The TNF was from The was from The was by The was by The was by of adipocytes were from in the of 2 2 2 and for 1 at the of with a cell were at for and the was The was at for 2 to the and The were in 2 2 and and at in a The were and of protein from were for of sTNFα, medium was from cell and to a of 1 The TNF was for as G.S. Nature. 1997; PubMed Scopus Google Scholar). were using insulin receptor and and were with for the and for to The of differentiation was as of cells by the of under were for and the S.D. was for The of the murine TNFα (mTNFΔ1–9K11E) was by and Fiers K. L. in (7Grell M. Douni E. Wajant H. Lohden M. Clauss M. Maxeiner B. Georgopoulos S. Lesslauer W. Kollias G. Pfizenmaier K. Schearich P. Cell. 1995; 83: 793-802Abstract Full Text PDF PubMed Scopus (1151) Google Scholar). The was by and and the The of the product was by The was with by The mTNFΔ1–9K11E was in the of the retroviral the B resistance gene H. PubMed Scopus Google Scholar). The of TNFR1 was by and using The product was was by and by on the M. L.A. A. Chen Goeddel D.V. S. A. 1991; PubMed Scopus Google Scholar). The of TNFR1 was with and the of the retroviral the resistance gene H. PubMed Scopus Google Scholar). The of murine TNFR2 was from D. T. Cell. Biol. 1991; PubMed Scopus Google Scholar). The was with by and the by of the retroviral the resistance gene H. PubMed Scopus Google Scholar). the expression were to confirm the and of the of the was by the expression cells, a cell M.L. D. S. A. 1993; PubMed Scopus Google Scholar), with the from cells was and through cells were at a of 2 cells were with a of a cells were with and to to in were at a of for and corresponding were the was in B and of 1 and 1 cells were in experiments to expression levels of TNFR1, and were to the G.S. Shargill N.S. Spiegelman B.M. Science. 1993; 259: 87-91Crossref PubMed Scopus (6088) Google Scholar). were on a G.S. Shargill N.S. Spiegelman B.M. Science. 1993; 259: 87-91Crossref PubMed Scopus (6088) Google Scholar). were to a and at for 1 with and subsequent were as G.S. Shargill N.S. Spiegelman B.M. Science. 1993; 259: 87-91Crossref PubMed Scopus (6088) Google Scholar). were by using and was for were on in with modified phosphate-buffered saline 1 and cells were in in cells were with and 2 with serum This was by a at in serum and of a TNF were with and 2 with serum a with cells were with with and with were under as J. S. M. J. Biol. 1997; PubMed Scopus Google Scholar). The mTNFΔ1–9K11E expression or was with a gene by K. of using The was determined by a and for as by the effects of transmembrane TNFα in cultured we have expressed a non-cleavable transmembrane form of murine TNFα in several preadipocyte cell These the cells and the preadipocyte cell lines in TNFR1, or The non-cleavable form of TNFα (mTNFΔ1–9K11E) has been generated by and from to in the of TNFα and in and cells (8Decoster E. Vanhaesebroeck B. Vandenabeele P. Grooten J. Fiers W. J. Biol. Chem. 1995; 270: 18473-18478Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar). In this we a retroviral expression to the non-cleavable mutant of its This also expression in a of cells and the of The TNFα was identified in cells is the produced by macrophages 1 levels of mTNFΔ1–9K11E expression were demonstrated by in preadipocyte cell lines 1 levels of both TNF receptors were also determined in cell types to the and of the TNF receptors. The TNFR2 in cells expressing mTNFΔ1–9K11E was expressing 1 and of mTNFΔ1–9K11E in cells not TNFR2 1 and This indicates that either the of TNFR2 expression by mTNFΔ1–9K11E the of TNFR1, or TNFR2 expression in these cells is at TNFR1 levels were by the of expression and of mTNFΔ1–9K11E as a protein was determined by both in cells and of cellular shown in expression of mTNFΔ1–9K11E protein on cells be by the of a TNFα by a The of is with confirm this we of cellular of adipocytes 1 that mTNFΔ1–9K11E was in a This is with as by the of 1 is a A. A. J. 1992; PubMed Scopus Google Scholar). receptor was also in this not The mTNFΔ1–9K11E protein was expressed as a protein with the wild type 26-kDa mTNFα. In both mTNFΔ1–9K11E and cells, two have been in the These are to be of sites as reported P. J. PubMed Scopus Google Scholar). protein in cell from different cell lines was also similar as determined by not The protein expression of the non-cleavable mutant in our is to be of the produced by macrophages by of mTNFΔ1–9K11E protein was in This is with as by for 1 we also examined in our experimental the mTNFΔ1–9K11E be cleaved at other sites to sTNFα of not TNFα from and cells but the of sTNFα from cells 1 protein of kDa) S. M. G. J. Biol. Chem. 1995; 270: Full Text Full Text PDF PubMed Scopus Google Scholar, E. P. Spiegelman B.M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), a secreted protein in was as a for protein to the from these cells 1 These demonstrated that mTNFΔ1–9K11E was expressed on the cell surface and not These results are to in lymphocytes using the same (8Decoster E. Vanhaesebroeck B. Vandenabeele P. Grooten J. Fiers W. J. Biol. Chem. 1995; 270: 18473-18478Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar). The preadipocyte cell is as experimental for differentiation in Annu. Rev. 1995; PubMed Scopus Google Scholar, B.M. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). These cells both TNF receptors but not levels of TNFα 1 In these cells, we examined expression of mTNFΔ1–9K11E to in the differentiation different for differentiation were to cells to expressing The were as follows: insulin and insulin and for the adipogenic factor peroxisome proliferator-activated receptor γ and a of the the of differentiation with these for cells were in insulin for more were for and of cells with expressing In the of adipogenic of cells whereas of differentiation was in cells The of insulin as the resulted in the differentiation of cells, but this was by the of mTNFΔ1–9K11E 2 a of and was cells However, of cells cells under this The of a as a for the of mTNFΔ1–9K11E on The of was with insulin but in with and these effects of mTNFΔ1–9K11E to sTNFα, cells were also with murine soluble TNFα. a of 1 sTNFα generated effects similar to with the The of cells under the different were and and and of a of sTNFα differentiation under not experiments with both mTNFΔ1–9K11E and soluble cells were under and was the of was to cell and was and The that differentiation are by in expression of of are in and the B.M. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). expression of a of can be to as of the of In order to the effects of mTNFΔ1–9K11E on differentiation at the we examined the levels of that are expressed in a in adipocytes. These were the adipogenic factor the protein the and the were with the The expression levels of of these were also in cells with the 2 B the of the expression levels of and in and The of mTNFΔ1–9K11E expression of these in cells to with insulin whereas was and of or and the expression of of these in and This also the of mTNFΔ1–9K11E on differentiation The of adipogenic the of and in gene expression be and cells under this and However, cells were to in the of the of mTNFΔ1–9K11E be the was 2 This was with a expression of mTNFΔ1–9K11E in the of these was the experiments The TNF receptor responsible for mediating the action of mTNFΔ1–9K11E on differentiation was determined by expressing this in and preadipocyte cell In lack both TNF receptors, the expression of mTNFΔ1–9K11E on differentiation as by both and gene expression and results were in preadipocytes wild type TNFR2 but not a TNFR1 was and cells on of the cells or gene expression and This that TNFR2 mediate this In preadipocytes carrying wild type TNFR1 but the expression of mTNFΔ1–9K11E resulted in inhibition of differentiation and 1 of cells under this of indicated that the expression levels of and were and of in These results that the of TNFR1 is sufficient for signaling the of mTNFΔ1–9K11E on the that TNFR2 function be in cells, was determined in these shown in mTNFΔ1–9K11E in both and cells but not in that the signaling of TNFR2 was in These results that TNFR1 is necessary for the inhibition of differentiation by also examined the of soluble TNFα on differentiation in these cellular murine TNFα was 2 at two of 1 and of or cells with sTNFα not differentiation at both in experiments not In contrast, in the of 1 sTNFα, differentiation was in of the the of sTNFα differentiation These indicate that both sTNFα and mTNFα can differentiation through TNFR1, and the extent of inhibition is or expression confirm the role of TNFR1 in mediating the of mTNFΔ1–9K11E within the same cellular background, we TNFR1 the preadipocytes expressing these cells are to and the retroviral resistance gene was for TNFR1 cell lines were expressing with B and resistance with B resistance gene and TNFR1, mTNFΔ1–9K11E and with resistance and mTNFΔ1–9K11E and TNFR1. In cells expressing both mTNFΔ1–9K11E and TNFR1, TNFR1 expression levels were expressing TNFR1 of the gene is not is that of levels of both mTNFΔ1–9K11E and TNFR1 is cells with TNFR1 expression levels the the was cells were in cell lines were also for shown in mTNFΔ1–9K11E-induced inhibition of adipogenesis was both mTNFΔ1–9K11E and TNFR1 were expressed in TNFR2 with TNFR1 in TNFR2 expression was also reconstituted in preadipocytes expressing The retroviral resistance gene was to The cell lines were expressing the with B and resistance with B resistance gene and mTNFΔ1–9K11E and with resistance and mTNFΔ1–9K11E and TNFR2 expression levels were in cells expressing both mTNFΔ1–9K11E and TNFR2 in cells expressing The of mTNFΔ1–9K11E to differentiation was not in preadipocytes TNFR2 with the cells TNFR2 not the functions of mTNFΔ1–9K11E on differentiation mediated by TNFR1. These results that the transmembrane TNFα differentiation by TNFR1 The wide array of biological actions of TNFα is at many The of both transmembrane and secreted forms of TNFα a of to TNFα the local actions of this are in both physiological and the of its cell form more However, in to the function and signaling of sTNFα, information regarding mTNFα is The actions of sTNFα on adipocytes have also been reports have shown that sTNFα has effects on differentiation B. B. Cerami A. Science. PubMed Scopus Google Scholar, J. Biol. 1989; PubMed Scopus Google Scholar, D. J. 1992; PubMed Scopus Google Scholar, H. J.R. Su J.L. 1997; PubMed Scopus Google Scholar). Furthermore, the of TNFα in cultured murine adipocytes has indicated that TNFR1 can mediate this B. B. Cerami A. Science. PubMed Scopus Google Scholar, J. Biol. 1989; PubMed Scopus Google Scholar). the other the biological activities and signaling mechanisms of mTNFα have not been determined in this In this we have generated several preadipocyte cell lines expressing a non-cleavable form of TNFα (mTNFΔ1–9K11E) to its actions in adipocytes. These studies that mTNFΔ1–9K11E is biologically active in several preadipocyte cell lines and can induce in the differentiation program. In wild type cells carrying both TNF receptors, expression of mTNFΔ1–9K11E to inhibition of differentiation adipocytes. The biological activities generated by mTNFΔ1–9K11E in our experimental are to be the protein expression of the mutant is of the produced by experiments with sTNFα generated results with reports and demonstrated that differentiation can be by both mTNFΔ1–9K11E and sTNFα under the experimental in this In the that the of can the effects of mTNFΔ1–9K11E is also with demonstrated that similar the effects of sTNFα on differentiation J. S. J. K. S. T. H. 1994; PubMed Scopus Google Scholar, D. S. J. B. 1995; PubMed Google Scholar). The extent of inhibition of differentiation by both mTNFΔ1–9K11E and sTNFα was on the of and on the strength of the the experimental where mTNFΔ1–9K11E expression is is that or multiple adipogenic be by a of with this, we that levels of both sTNFα and mTNFΔ1–9K11E by 2 can differentiation under the is to that is a adipogenic and the of differentiation be determined by the strength of from either In this we have also determined the TNF receptor responsible for mediating this action of mTNFΔ1–9K11E by preadipocyte cell lines in TNFR1, or both receptors. These cells can adipocytes with and a experimental to signaling through TNF of mTNFΔ1–9K11E in and preadipocyte cell lines demonstrated that TNFR1 is necessary for the action of mTNFΔ1–9K11E on TNFR1 or TNFR2 the or cell we have demonstrated that mTNFΔ1–9K11E selectively through TNFR1 and signaling through this receptor is necessary and sufficient for its This also to the cellular to the of signaling TNFR1 and of TNFR1 in preadipocytes the of mTNFΔ1–9K11E on In contrast, of TNFR2 in preadipocytes not this action of mTNFΔ1–9K11E mediated by TNFR1. we that mTNFΔ1–9K11E differentiation by selectively activating TNFR1. The fact that mTNFΔ1–9K11E not TNFR2 to differentiation is other studies have shown that TNFR2 P. E. M. D. C. C. T. Fiers W. Bluethmann H. Eur. J. Immunol. 1997; 27: PubMed Scopus Google or both TNFR1 and TNFR2 (9Kusters S. Tiegs G. Alexopoulou L. Pasparakis M. Douni E. Kunstle G. Bluethmann H. Wendel A. Pfizenmaier K. Kollias G. Grell M. Eur. J. Immunol. 1997; 27: 2870-2875Crossref PubMed Scopus (173) Google Scholar, L. Pasparakis M. Kollias G. Eur. J. Immunol. 1997; 27: PubMed Scopus Google Scholar). TNFR2 is expressed in both preadipocytes and adipocytes and is in G.S. Shargill N.S. Spiegelman B.M. Science. 1993; 259: 87-91Crossref PubMed Scopus (6088) Google Scholar, G.S. P. Spiegelman B.M. Diabetes. 1997; PubMed Google Scholar). In a role in inhibition of insulin receptor signaling through TNFR1 M. K. H. J. Diabetes. 47: PubMed Scopus Google Scholar). However, is not in inhibition of adipogenesis by either transmembrane or soluble TNFα. these that mTNFα can both TNFR1 and but receptor or biological may be the cell type or the or the expression of the transmembrane studies have shown that TNFR1 can mediate other sTNFα functions in in to signaling the These of J.K. G.S. J. 3: Scholar, M. T. T. T. H. K. T. PubMed Scopus Google and inhibition of insulin signaling in murine adipocytes P. G.S. Spiegelman B.M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). studies be necessary to mTNFα similar and of TNFR1 is a in adipocytes. The fact that TNFα is biologically active in adipocytes on the cell surface makes a mediator of other local TNFα-induced responses. It is to that this be in disease states adipose local levels of such as or It is also that mTNFα produced in the of adipose from either preadipocytes or also adipocytes through cell-cell contact. mTNFα is active in mediating other effects that the of also have a on However, the of the of the studies in cultured cells to are in including of function are to the role of this form of TNFα in under physiological or K. M. and for in TNF cell are to and Fiers K. L. for the of the non-cleavable murine