Biomedical subjects

X Feng

Publications and source records attributed to X Feng.

At least 55 records · Page 3Linked to original sources

PubMed2001

Effects of dietary fat and endurance exercise on plasma cortisol, prostaglandin E2, interferon-gamma and lipid peroxides in runners.

OBJECTIVE: Exercise and the neuroendocrine and oxidative stress it elicits on immune function is modulated by dietary fat intake. The effects of increasing dietary fat on endurance exercise-induced alterations 80% of VO2max for 2 hours) in the plasma levels of cortisol and prostaglandin E2 (PGE2), interferon-gamma (IFN-gamma) and lipid peroxides were investigated. As higher levels of cortisol, PGE2 and lipid peroxides could be immunosuppressive, the effects of different levels of dietary fat on these measures in runners were determined. METHODS: Healthy trained runners (males and females) consumed serially 15% fat diet (of daily energy), 30% fat diet and 40% fat diets for four weeks each. In the last week of each diet period the subjects ran to exhaustion at 80% of their VO2max and blood was drawn pre- and post-run. Cortisol, IFN-gamma, PGE2 and lipid peroxides were determined using standard techniques. RESULTS: Pre-exercise levels of plasma cortisol were elevated, IFN-gamma was unchanged and PGE2 and lipid peroxides decreased on the 40%F diet compared to 30%F and 15%F. Post-exercise levels of plasma cortisol (p < 0.004), PGE2 (p < 0.0057) and lipid peroxide levels increased (p < 0.0001) after endurance exercise on all diets. The rates of increase of plasma cortisol levels during exercise were similar on all three diets. Although absolute cortisol levels were higher in the high fat group, the rate of increase of plasma cortisol level during exercise was similar on each diet. The dietary fat levels did not affect IFN-gamma, however, PGE2 and lipid peroxides decreased with increasing fat at baseline at 40%F level (p < 0.01; 30%F vs. 40% F: p < 0.002; 15%F vs. 40%F: p < 0.007). CONCLUSIONS: Data from the present study suggest that higher levels of fat in the diet, up to 40%, increase endurance running time without adverse effects on plasma cortisol, IFN-gamma, and lipid peroxide levels.

Adult↗

PubMed2001

Structures of three cis-beta1 and three cis-beta2 isomers of [Co(trien)(aminoacidato)]2+ complexes.

The crystal structures and absolute configurations of three cis-beta(1) and three cis-beta(2) isomers of [Co(trien)(L-aminoacidato)](2+), namely beta(1)-Lambda(SSS)(lambdalambdadelta)/(lambdadeltadelta)-[Co(trien)(L-isoleucinato)](ClO(4))(2), L-isoleucinato(triethylenetetramine)cobalt(III) diperchlorate (1), beta(1)-Lambda(SRS)(lambdadeltalambda)-[Co(trien)(L-valinato)](ClO(4))(2), L-valinato(triethylenetetramine)cobalt(III) diperchlorate (2), beta(1)-Delta(RSS)(deltalambdadelta)-[Co(trien)(L-pyroglutamato)]ClO(4), L-pyroglutamato(triethylenetetramine)cobalt(III) perchlorate (3), beta(2)-Delta(RRS)(deltadeltalambda)-[Co(trien)(L-isoleucinato)]I(2).H(2)O, L-isoleucinato(triethylenetetramine)cobalt(III) diiodide monohydrate (4), beta(2)-Delta(RRS)(deltadeltalambda)-[Co(trien)(L-isoleucinato)](ClO(4))(2).2H(2)O, L-isoleucinato(triethylenetetramine)cobalt(III) diperchlorate dihydrate (5), and beta(2)-Lambda(SSS)(deltalambdalambda)[Co(trien)(L-leucinato)](ClO(4))(2).2H(2)O, L-leucinato(triethylenetetramine)cobalt(III) diperchlorate dihydrate (6), have been determined. Both beta(1) and beta(2) isomers form inter-cation hydrogen-bonding interactions through double or triple hydrogen bonds which link the cations into helices. However, the motifs of the interactions are different in beta(1) and beta(2) isomers, resulting in different packing structures. A localized hydrophobic area is observed in the packing structure of (1), a unique feature amongst these six structures. This work describes the first synthesis of the beta(1) isomer by direct reaction between amino acids and cis-alpha-[Co(trien)Cl(2)]Cl in mildly basic solution.

Journal Article↗

PubMed2001

A Glanzmann's mutation in beta 3 integrin specifically impairs osteoclast function.

Osteoclastic bone resorption requires cell-matrix contact, an event mediated by the alpha v beta 3 integrin. The structural components of the integrin that mediate osteoclast function are, however, not in hand. To address this issue, we generated mice lacking the beta 3 integrin gene, which have dysfunctional osteoclasts. Here, we show the full rescue of beta 3(-/-) osteoclast function following expression of a full-length beta 3 integrin. In contrast, truncated beta 3, lacking a cytoplasmic domain (h beta 3c), is completely ineffective in restoring function to beta 3(-/-) osteoclasts. To identify the components of the beta 3 cytoplasmic domain regulating osteoclast function, we generated six point mutants known, in other circumstances, to mediate beta integrin signaling. Of the six, only the S(752)P substitution, which also characterizes a form of the human bleeding disorder Glanzmann's thrombasthenia, fails to rescue beta 3(-/-) osteoclasts or restore ligand-activated signaling in the form of c-src activation. Interestingly, the double mutation Y(747)F/Y(759)F, which disrupts platelet function, does not affect the osteoclast. Thus similarities and distinctions exist in the mechanisms by which the beta 3 integrin regulates platelets and osteoclasts.

Amino Acid Sequence↗

PubMed2001

Aberrant alternative splicing of thyroid hormone receptor in a TSH-secreting pituitary tumor is a mechanism for hormone resistance.

Patients with TSH-secreting pituitary tumors (TSHomas) have high serum TSH levels despite elevated thyroid hormone levels. The mechanism for this defect in the negative regulation of TSH secretion is not known. We performed RT-PCR to detect mutations in TRbeta from a surgically resected TSHoma. Analyses of the RT-PCR products revealed a 135-bp deletion within the sixth exon that encodes the ligand-binding domain of TRbeta2. This deletion was caused by alternative splicing of TRbeta2 mRNA, as near-consensus splice sequences were found at the junction site and no deletion or mutations were detected in the tumoral genomic DNA. This TRbeta variant (TRbeta2spl) lacked thyroid hormone binding and had impaired T3-dependent negative regulation of both TSHbeta and glycoprotein hormone alpha-subunit genes in cotransfection studies. Furthermore, TRbeta2spl showed dominant negative activity against the wild-type TRbeta2. These findings strongly suggest that aberrant alternative splicing of TRbeta2 mRNA generated an abnormal TR protein that accounted for the defective negative regulation of TSH in the TSHoma. This is the first example of aberrant alternative splicing of a nuclear hormone receptor causing hormonal dysregulation. This novel posttranscriptional mechanism for generating abnormal receptors may occur in other hormone-resistant states or tumors in which no receptor mutation is detected in genomic DNA.

Adenoma↗

PubMed2001

Genetic mutations of precore region of hepatitis B virus in hepatitis B e antigen-negative patients with fulminant hepatitis B and translation of precore variants in vitro.

OBJECTIVE: To detect mutations in precore region of hepatitis B virus of HBeAg negative- patients with fulminant hepatitis and to determine the effect of T1862 mutants on synthesis of precursor of hepatitis B e antigen. METHODS: The entire precore and core region were amplified from sera of nine HBeAg negative-patients with fulminant hepatitis B by polymerase chain reaction (PCR). PCR products were cloned into plasmid pUC18, and sequencing for analysis of precore mutations. Precore and core sequence of T1862 variant were also cloned into expression plasmid pGEMT for in vitro transcription and translation study on synthesis and procession of e antigen. RESULTS: Three variants, A1896, A1899 and T1862, whose nucleotide mutation led to amino acids substitutions, were detected in patients with fulminant hepatitis. T1862 variant didn't effect the synthesis of precursor of e antigen. Also there was no variant detected in precore region of hepatitis B virus in two patients. CONCLUSIONS: The causes for negative of e antigen in fulminant hepatitis patients may be partially explained by precore mutation of A1896 and T1862, and the latter variant may effect the process of precursor of e antigen, rather than the synthesis of precursor protein.

Base Sequence↗

PubMed2001

[Correlation between liver fibrosis stage and serum liver fibrosis markers in patients with chronic hepatitis B].

OBJECTIVE: To evaluate the diagnostic value of serum liver fibrosis markers by analyzing the correlation between liver fibrosis stage in patients with chronic hepatitis B and serum liver fibrosis markers, such as hyaluronate, type III procollagen, laminin, and type IV collagen. METHODS: There were 278 patients with chronic hepatitis B in this series. Before liver biopsy, the serum was collected to test hyaluronate, type III procollagen, laminin, and type IV collagen. Data were analyzed statistically. RESULTS: Liver fibrosis stage was correlated to inflammation degree. In patients with moderate or serious liver inflammation and fibrosis, serum hyaluronate was above normal level, and correlated to liver inflammation and fibrosis. For patients with chronic hepatitis B, serum type III procollagen, laminin, and type IV collagen increased apparently. While laminin was correlated to liver fibrosis, type III procollagen and type IV collagen correlated to liver inflammation. CONCLUSIONS: Serum hyaluronate, type III procollagen, laminin, and type IV collagen could reflect the state of liver fibrosis. Hyaluronate may be a useful marker for liver cirrhosis.

Adolescent↗

PubMed2001

[Treatment of dilute solution anilines-containing with displacement by extraction].

It was found that the biodegradability (indicated by BOD5/CODCr value of water solution containing anilire or chloroaniline declined with the increasing of their concentration. In order to bio-treat such water, decrease of the solute's concentration was necessary. Based on the research of organic solvents' and complexing agent's biodegradability, a series of extraction experiments were conducted for aniline and m-chloroaniline with complexing agent or physical solvent. The factors influencing the distribution ratio were discussed. The BOD5/CODCr value of raffinates showed that the raffinate can be treated by biological degradation without dilution if suitable solvent was choosed. It was proved that displacement by extraction had great potentiality for treating wastewater containing non-biodegradable organic contaminant.

Aniline Compounds↗

PubMed2001

[The granulation of PCP-degrading anaerobic sludge with industrial organic wastewater as co-substrate].

The granulation of PCP degrading anaerobic sludge in two improved UASB reactors under co-existence of two types of industrial wastewater and PCP were studied. It was found that the granulation of PCP degrading anaerobic sludge could be divided into three stages, i.e. sludge acclimation, granular pre-formation and granular maturation. The changes in biomass, sludge bioactivity, population and ecological distribution of three group bacteria involved in anaerobic digestion during the course of granulation were also examined. Anaerobic granules from two reactors showed high dechlorination activity at meta, otho and para position. Rod-shaped and filamentous shaped Methanosaeta-like spp. were found in anaerobic granules. Results of electron microscopy revealed the presence of synthophic microcolonies and non-layed microstructure in PCP-degrading granules. The types of industrial wastewater used as co-substrate had affected the course of sludge granulation, dechlorinating activity and pre-dominant methanogens in PCP-degrading anaerobic granules.

Anaerobiosis↗

PubMed2001

[Preliminary study on anaerobic bioremediation process for pentachlorophenol (PCP)-contaminated soil].

The performances of soil-slurry process with supplement of anaerobic granular sludge for remediating PCP-contaminated soil was investigated. The results showed that inherent anaerobic microbes in soil exhibited a little dechlorinating activity for simulative contaminated soil with 30 mg.kg-1 of PCP, the average PCP degradation rates within 28 d was 0.258 mg.kg-1.d-1. In soil slurry processes with 5 g.kg-1 granular sludge at aerobic, aerobic/anaerobic and anaerobic operation, the average PCP degradation rates within 28 d were 0.269, 0.291/0.842 and 0.892 mg.kg-1.d-1, respectively. PCP degradation rates were increased with increasing the amounts of anaerobic granular sludge, 0.834, 0.843, 0.928 mg.kg-1.d-1 of the average PCP degradation rates within 35 d were achieved in soil slurry processes supplemented with 5, 10, 25 g.kg-1 of granular sludge, respectively. This bioremediation process also presented higher initial PCP degradation rate for higher concentration(60 mg.kg-1) of PCP in soil.

Anaerobiosis↗

PubMed2001

[Clinical application of the reversed digital arteial island flap with digital wein and digital dorsal nerve anastomosis].

OBJECTIVE: To introduce clinical application of the reversed digital arteial island flap with digital wein and digital dorsal nerve anastomosis to repair digital soft tissue defect. METHODS: Since 1999, 10 cases involving 14 digital defects associated with exposure of bone or tendon were treated by using the reversed digital arterial island flap with digital vein and digital dorsal cutaneous nerves anastomosis. RESULTS: All the flaps were 100% survived and the result is satisfactory. CONCLUSIONS: The reversed digital arterial island flap with anastomosing the digital vein and dorsa digita nerve is a safe, and simple technique, which can maintain the finger's normal appearance and reduce the incidence of venous crisis and improve the survival rate of the flap.

Adolescent↗

PubMed2001

Epidemiological investigation of Histoplasma capsulatum infection in China.

OBJECTIVE: To provide reliable information concerning the presence or the absence of Histoplasma capsulatum (H. capsulatum) infection in China, and data concerning this respect. METHODS: Three hundred normal people and 435 hospitalized patients, who lived in Hunan and Jiangsu provinces, and the Xinjiang Autonomous Region, were tested with yeast-phase histoplasmin (ALK/Berkerley Biologicals Laboratories, USA) and human pure protein derivative of tuberculin (PPD) on the volar surface of the forearm. Any reaction to the antigens over 5.0 mm in diameter of induration at 48-72 hours was considered positive. RESULTS: A total of 138 subjects (18.8%) in 735 patients reacted to histoplasmin with 5.0-45.0 (9.1 +/- 4.3) mm indurations. Significant differences of positive skin reaction rates in normal subjects were found in Hunan, Jiangsu and Xinjiang (8.9% vs 15.1% vs 2.1%). The overall positive rate of patients was 25.5%. Patients with tuberculosis [31.7% (78/246)] had a significantly higher positive skin reaction rate in comparison with those suffering from pneumonia [17.7% (11/62)], lung cancer [20.9% (9/43)], chronic obstructive pulmonary disease [17.3% (9/52)] and other diseases [12.5% (4/32)] (P < 0.01). Of 562 cases, 292 cases (52.0%) reacted to PPD with indurations of 5-50 (13.7 +/- 4.9) mm in diameter, 63 cases (11.2%) reacted to both histoplasmin and PPD, while 38 cases (6.9%) reacted to histoplasmin but not to PPD. CONCLUSIONS: The data suggest that there is H. capsulatum herd infection in China. The infection rate in Southeast China is higher than that in the Northwest, and the infection rate of patients with pulmonary tuberculosis is higher than that of normal persons and other pneumonopathy patients.

Adult↗

PubMed2001

Th1/Th2 type cytokines in hepatitis B patients treated with interferon-alpha.

OBJECTIVE: To investigate the relationship between the expression of Th1/Th2 type cytokines and the effect of interferon-alpha therapy. METHODS: Th1/Th2 type cytokines were assayed by enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR) on 23 patients with chronic hepatitis B who were treated with interferon-alpha. RESULTS: Levels of IFN-gamma in the supernatant of peripheral blood mononuclear cells (PBMC) cultures from the patients with hepatitis B were slightly lower than those of controls (P = 0.07). However, the levels of IL-4 were higher than those of controls (P = 0.01). Cytokines measurements during IFN-alpha treatment showed a trend to decreasing levels of IL-4 at 4, 12, and 24 weeks. Levels of IFN-gamma were slightly increased following IFN-alpha treatment (P = 0.09). In patients with a complete response to IFN-alpha, the levels of IFN-gamma were higher at 24 weeks following IFN-alpha treatment than that of pre-treatment (P = 0.04), and the levels of IL-4 decreased markedly at 12 and 24 weeks (P = 0.02, 0.03, respectively). mRNA expression positively correlated with the level of Th1/Th2 type cytokines in the supernatant. CONCLUSION: The expression of Th2 type cytokines is predominant in patients with chronic hepatitis B. Interferon-alpha therapy can modulate the balance of Th1/Th2 type cytokines, and this is related to its clinical effect. Levels of Th1/Th2 type cytokines could be a predictor of clinical response during Interferon-alpha treatment.

Antiviral Agents↗

PubMed2001

[Renal protective effects of vitamin E in diabetic rats].

OBJECTIVE: To investigate the renal protective effect of vitamin E on streptozotocin induced diabetic rats, as well as the possible mechanism involved in. METHODS: Vitamin E 20 mg x kg(-1) x d(-1) was given to diabetic rats for 8 weeks. Urinary albumin excretion (UAE) was measured by radioimmunoassay. The changes of creatinine clearance rate (Ccr), nitric oxide(NO), nitric oxide synthase (NOS) and endothelin(ET) in the plasma and renal cortical tissue, membrane protein kinase C(PKC) in the renal glomeruli were observed. RESULTS: At two weeks, diabetic rats had supernormal Ccr[(6.47 +/- 1.51) ml x min(-1) x kg(-1)], UAE[(15.60 +/- 1.64) microg/24h], NO[(37.30 +/- 3.77) micromol/L], NOS[(34.89 +/- 3.83) U/L] and PKC[(86.85 +/- 11.37) pmol x min(-1) x mg protein(-1)] of diabetic rats were increase but ET was decreased. At 8 weeks, PKC[(84.18 +/- 12.14 ) pmol x min(-1) x mg protein(-1)] and ET of diabetic rats was increased significantly, but NO[(22.75 +/- 2.89) micromol/L] and NOS[(21.34 +/- 1.92) U/L] of diabetic rats was lowered. After treated with vitamin E, Ccr[(4.46 +/- 0.49) ml x min(-1) x kg(-1)], UAE[(16.31 +/- 1.12) microg/24h], PKC[(65.19 +/- 8.83) pmol x min(-1) x mg protein(-1)] at 8 weeks were decreased significantly. Both NO[(33.13 +/- 3.77) micromol/L] and NOS[(30.16 +/- 2.89) U/L] in plasma and kidney tissue were lowered as compared with untreated diabetic group in two weeks. Vitamin E also delayed the NO and NOS lowering in 8 weeks. CONCLUSION: Vitamin E could ameliorate early diabetic renal hemodynamic abnormality via inhibiting PKC, in which inhibition of NO production might be involved. It is important to reduced the PKC activity so as to prevent or delay the development of diabetic nephropathy.

Animals↗

PubMed2001

[Diagnostic and differential diagnostic potential of mitochondrial DNA assessment in patients with Leber's hereditary optic neuropathy].

OBJECTIVE: To study the primary mutations of mitochondrial DNA (mtDNA) associated with Leber's hereditary optic neuropathy (LHON) in patients with optic neuropathy. METHODS: Seventy-nine patients with a variety of bilateral optic neuropathy were examined. Mutations at np 3,460, np 11,778 and np 14,484 of mtDNA were tested by PCR-restriction fragment length polymorphism technique to detect DNA in peripheral blood. The samples were taken from 16 cases of clinically diagnosed LHON, 44 cases of suspected LHON, two cases of alcohol amblyopia, four cases of multiple sclerosis, five cases of autosomal dominant hereditary optic atrophy, 4 cases with primary open-angle glaucoma, three cases of spinocerebellar degeneration, and one case of ethambutol-induced optic neuropathy. RESULTS: The mutation at np 11,778 was identified in 31 cases (39.2%), consisting of all the 16 clinically diagnosed LHON cases, thirteen cases (29.5%) of the suspected LHON, and the two cases of alcohol amblyopia. The remaining 48 cases were negative for mtDNA mutations at np 3,460, np 11,778, or np 14,484. CONCLUSION: Assessment of mtDNA provides a useful diagnostic aid in confirming and excluding the diagnosis of LHON, particularly useful in cases without a family hereditary history and cases with cause unknown bilateral optic neuritis.

Adult↗

PubMed2001

[A clinicopathologic study on 9 cases of epithelioid hemangioendothelioma].

OBJECTIVE: To study the clinicopathological features of epithelioid (histiocytoid) hemangioendothelioma (EHE). METHODS: 9 cases of EHE were examined by light microscopy and immunohistochemistry, 1 case with ultrastructural observation. RESULTS: The patients' age ranged from 16 to 47 years (mean 32 years). The lesions occurred in both sexes and presented at a variety of sites including head and facial area (4 cases), upper limbs (3 cases) and lower limbs (2 cases). The morphological characters were: (1) "epithelioid" or "histiocytoid" tumor cells; (2) rounded or polygonal tumor cells arranged in nests, cords and irregular patterns; (3) the tumor cells were embedded in myxoid or hyaline matrix; (4) primitive lumen formation within a single tumor cell (intracytoplasmic lumens); (5) lack of pleomorphism, mitotic activity and necrosis; (6) presence of spindle cell hemangioendothelioma in some cases; (7) osteoclast like giant cells scattered throughout the entire lesion were observed in one case. Immunohistochemistry studies on 7 cases found that tumor cells were positive for vimentin (7/7), factor VIII-RAg (5/7), CD31 (5/7), CD34 (5/7), cytokeratin (2/7), CD68 and alpha-AT (1/7). Ultrastructural study of 1 case demonstrated Weibel-Palade bodies and an abundance of intermediate filaments in the cytoplasm. The follow-up of 6 cases found that 3 cases developed local recurrences but none of them metastasized. CONCLUSIONS: EHE is a distinctive low-grade sarcoma whose etiology remains unknown. Recognizing its morphological characters is important to avoid confusion with other similar lesions.

Adolescent↗

PubMed2001

[A study on transmission of pathogenic bacteria of rampant caries from mothers to children].

OBJECTIVE: In order to prevent rampant caries in children, the transmission from mothers to children of pathogenic bacteria of rampant caries will be investigated in this study. METHODS: By using fingerprint technique, the genetic diversities of Streptococcus mutans(S. mutans) were examined respectively in 10 children with rampant caries, 10 children without rampant caries S. mutans, 10 2-year-old caries-free children, and their mothers. The levels of S. mutans in saliva of mothers were also examined. For fingerprinting, chromosomal DNA of isolates obtained from plaques of these children and from saliva of their mothers were digested with restriction endonuclease HindIII and examined by electrophoresis on 0.7% agarose gel. DNA fingerprints were obtained and analyzed for genotypic similarities. RESULTS: The DNA fingerprint patterns showed that the proportion of children whose genotypes of S. mutans matched their mothers in the children with rampant caries was 70%, which is similar to that in the children without rampant caries and the caries-free children (60% respectively). The number of distinct genotypes of S. mutans harbored in children with rampant caries was, on average, greater than the number of genotypes present in children without rampant caries and caries-free children (1.7, 1.2 and 1.1 respectively, P < 0.05). Mothers of children with rampant caries had similar levels of S. mutans in saliva as those mothers of children without rampant caries and caries-free children. However, mothers of children with rampant caries had significantly higher DMFT scores and higher levels of Streptococcus sobrinus (S. sobrinus) in saliva than the mothers of caries-free children did. CONCLUSION: In all child groups, mothers were probably the main source of infection with S. mutans. Rampant caries in children is associated with DMFT scores and levels of S. sobrinus in saliva of mothers. In the initiation of rampant caries experienced by a child, the transmission of pathogenic bacteria from mothers to children may be the main source.

Adult↗

PubMed2001

[The isolation and identification of pathogenic bacteria from rampant caries in children].

OBJECTIVE: In order to prevent rampant caries in children, the predominant pathogenic bacteria of rampant caries in children were defined. METHODS: The pathogenic bacteria of rampant caries were isolated and identified in 30 children with rampant caries, aged from 2 to 5 years old. Samples were collected from the caries of labial surfaces of maxillary anterior deciduous teeth, including caries lesions and caries-free smooth enamel surfaces. Plaque were obtained from the cervical third areas of the maxillary labial anterior deciduous tooth surfaces in children without rampant caries and caries-free children and served as controls respectively. The isolates were identified by colony morphology, biochemical tests and DNA base contents (mol percent G + C). RESULTS: The prevalence of Streptococcus mutans (S. mutans) and Streptococcus sobrinus (S. sobrinus) in the plaque of caries lesions and the proportions of S. mutans and S. sobrinus in the plaque of 2 sampling sites of children with rampant caries were all significantly higher than those of children without rampant caries and caries-free children (P < 0.05). CONCLUSION: S. mutans and S. sobrinus are predominant pathogenic bacteria in rampant caries in children.

Child↗

PubMed2000

Caveolin-1 associates with TRAF2 to form a complex that is recruited to tumor necrosis factor receptors.

Tumor necrosis factor (TNF) receptor-associated factor (TRAF) 2 is an intracellular adapter protein, which, upon TNF stimulation, is directly recruited to the intracellular region of TNF receptor 2 (TNFR2) or indirectly, via TRADD, to the intracellular region of TNF receptor 1 (TNFR1). In cultured human umbilical vein endothelial cells, endogenous TRAF2 colocalizes with the membrane-organizing protein caveolin-1 at regions of enrichment subjacent to the plasma membrane as detected by confocal fluorescence microscopy. Both endogenous and transfected TRAF2 protein coimmunoprecipitate with caveolin-1 in the absence of ligand. Upon TNF treatment, the TRAF2-caveolin-1 complex transiently associates with TRADD, and upon overexpression of TNFR2, the TRAF2-caveolin-1 complex stably associates with and causes redistribution of this receptor as detected by confocal fluorescence microscopy. In human embryonic kidney 293 cells, which have minimal endogenous expression of caveolin-1, cotransfection of TRAF2 and caveolin-1 results in spontaneous association of these proteins which can further associate with and redistribute transfected TNFR2 molecules. The association of caveolin-1 with TNFR2 depends upon TRAF2. Cotransfection of caveolin-1 protein increases TRAF2 protein expression levels in HEK 293 cells, which correlates with enhancement of TNF and TRAF2 signaling, measured as transcription of a NF-kappaB promoter-reporter gene, although the caveolin-enhanced response to TNF is attenuated at higher caveolin levels. These findings suggest that intracellular distribution of activated TNF receptors may be regulated by caveolin-1 via its interaction with TRAF2.

Antigens, CD↗