The fifth epidermal growth factor-like domain of thrombomodulin does not have an epidermal growth factor-like disulfide bonding pattern.

The disulfide bonding pattern of the fourth and fifth epidermal growth factor (EGF)-like domains within the smallest active fragment of thrombomodulin have been determined. In previous work, this fragment was expressed and purified to homogeneity, and its cofactor activity, as measured by Kcat for thrombin activation of protein C, was the same as that for full-length thrombomodulin. CNBr cleavage at the single methionine in the connecting region between the domains and subsequent deglycosylation yielded the individual EGF-like domains. The disulfide bonds were mapped by partial reduction with tris(2-carboxyethyl)phosphine according to the method of Gray [Gray, W. R. (1993) Protein Sci. 2, 1732-1748], which provides unambiguous results. The disulfide bonding pattern of the fourth EGF-like domain was (1-3, 2-4, 5-6), which is the same as that found previously in EGF and in a synthetic version of the fourth EGF-like domain. Surprisingly, the disulfide bonding pattern of the fifth domain was (1-2, 3-4, 5-6), which is unlike that found in EGF or in any other EGF-like domain analyzed so far. This result is in line with an earlier observation that the (1-2, 3-4, 5-6) isomer bound to thrombin more tightly than the EGF-like (1-3, 2-4, 5-6) isomer. The observation that not all EGF-like domains have an EGF-like disulfide bonding pattern reveals an additional element of diversity in the structure of EGF-like domains.     

类表皮生长因子域7与动脉粥样硬化斑块内血管生成关系

目的 研究类表皮生长因子域7( Egfl7)在动脉粥样硬化斑块内的表达水平和小分子干扰RNA(siRNA)对内皮细胞株血管生长因子表达的影响. 方法 利用免疫组化和免疫荧光染色检测人髂动脉和小鼠无名动脉粥样硬化斑块内Egfl7的表达水平;并利用以Egfl7为靶标的siRNA,通过脂质体将siRNA转入人脐静脉内皮细胞株(HUVEC),以未转染siRNA细胞和转染无关siRNA细胞为对照,在干扰后0h,12 h,24 h,48 h,反转录聚合酶链反应(PT-PCR)检测Egfl7、血管内皮生长因子(VEGF)、血小板衍生生长因子A、B(PDGF-A、PDGF-B) mRNA水平的改变,免疫印迹法检测Egfl7、VEGF、PDGF、血管细胞黏附分子(VCAM)及细胞间黏附分子(ICAM)蛋白表达水平的变化.结果 人髂动脉和小鼠无名动脉粥样硬化斑块内Egfl7表达水平上调;HUVEC内Egfl7在siRNA干扰后0h、12 h、24 h、48 h时mRNA表达分别为(0.31±0.05)、(0.14±0.02)、(0.09±0.01)、(0.02±0.01),蛋白表达为(0.93±0.08)、(0.71±0.11)、(0.39±0.09)、(0.07±0.01).Egfl7、VEGF、PDGF-A、PDGF-B mRNA及其蛋白表达水平随干扰时间延长均下降或抑制,与siRNA干扰0h比较差异有统计学意义(均P＜0.05). 结论 动脉粥样硬化斑块内Egfl7表达水平提高;siRNA抑制HUVEC Egfl7表达水平的同时,其他血管生长因子和黏附分子表达水平亦下降.     

Protein S Tokushima: abnormal molecule with a substitution of Glu for Lys-155 in the second epidermal growth factor-like domain of protein S

A 29-year-old female patient with heterozygous congenital protein S deficiency suffering from thrombotic disease had normal levels of both total and free protein S antigen (70% and 65%, respectively), but low cofactor activity (31%) for activated protein C, indicating that she had a variant of protein S, protein S Tokushima. Western blotting using the polyclonal anti-protein S antibody showed that approximately half of the patient's protein S appeared to be the variant with a higher molecular weight than normal protein S. The partially purified variant protein S bound neither to the monoclonal antibody recognizing calcium- dependent conformation of protein S nor to the antibody recognizing the thrombin-sensitive domain of protein S. Among the exons from II to XV of the patient's protein S gene encoding from the NH2-terminal end to the COOH-terminal end of protein S, only one missense mutation (A to G) was found in exon VI of the protein S alpha-gene, which results in amino acid substitution of Glu(GAG) for Lys-155(AAG) in the second epidermal growth factor-like domain of protein S. The recombinant protein S Tokushima expressed in BHK cells had a slightly higher molecular weight than the recombinant normal one, did not bind to the antibody specific for the thrombin-sensitive domain, and did not show the cofactor activity. These findings suggest that the protein S Tokushima molecule is structurally and functionally a variant of protein S, and that this variant protein S is the cause of severe thrombosis in this patient.     

Differential expression of heparin-binding epidermal growth factor-like growth factor in the rat ovary

We investigated the expression of heparin-binding epidermal growth factor-like growth factor (HB-EGF) and its receptors in the rat ovary to define the role of HB-EGF in the ovarian function. The expression pattern of HB-EGF mRNA and protein were studied by semi-quantitative RT-PCR and immuno-histochemistry using an antibody that was specifically stained for the precursor form of HB-EGF in naturally cycling rats and immature pseudo-pregnant rat models. The immuno-histochemical study showed that in naturally cycling rats, HB-EGF was expressed in most granulosa cells of early follicles and all the developing follicles but not in preovulatory follicles. This was supported by the semi-quantitative RT-PCR results in that the lowest level of HB-EGF mRNA during the estrous cycle was found in the evening of proestrous when the HB-EGF negative preovulatory follicles were most prominent. The results suggest that HB-EGF might be a mitogen for granulosa cells and down regulation of its expression may be necessary for the final maturation of follicles. In corpora lutea, luteal cells of older generation stained stronger than those of younger generation. Moreover, luteal cells of late luteal phase stained stronger than those of the mid and early luteal phases in the immature pseudo-pregnant rat models, indicating that the precursor form may be associated with death of luteal cells. Finally, of the two cognate receptors for HB-EGF, erbB1 was expressed in the rat ovary, but erbB4 was specifically not expressed in this organ. The spatial and temporal pattern of HB-EGF expression suggest that HB-EGF may an important local regulator of ovarian function and structure.     

Heparin-binding epidermal growth factor-like growth factor signaling in flow-induced arterial remodeling

Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) is activated by reduced endothelial shear stress and stimulates smooth muscle cell proliferation in vitro. Moreover, HB-EGF is augmented at sites of intimal hyperplasia and atherosclerosis, conditions favored by low/disturbed shear stress. We thus tested whether HB-EGF contributes to low flow-induced negative hypertrophic remodeling (FINR) of a mouse carotid artery. Blood flow was surgically decreased in the left and increased in the right common carotid arteries. After 21 days, the left carotid artery exhibited lumen narrowing, thickening of intima-media and adventitia, and increased circumference that were inhibited by approximately 50% in HB-EGF(+/-) and approximately 90% in HB-EGF(-/-) mice. FINR was also inhibited by the EGF receptor inhibitor AG1478. In contrast, eutrophic outward remodeling of the right carotid artery was unaffected in HB-EGF(+/-) and HB-EGF(-/-) mice, nor by AG1478. FINR-induced proliferation and leukocyte accumulation were reduced in HB-EGF(-/-). FINR was associated with increased reactive oxygen species, increased expression of pro-HB-EGF and tumor necrosis factor alpha-converting enzyme (pro-HB-EGF sheddase), increased phosphorylation of EGF receptor and extracellular signal-regulated kinase 1/2, and increased nuclear factor kappaB activity. Apocynin and deletion of p47(phox) inhibited FINR, whereas deletion of HB-EGF abolished nuclear factor kappaB activation in smooth muscle cells. These findings suggest that HB-EGF signaling is required for low flow-induced hypertrophic remodeling and may participate in vascular wall disease and remodeling.     

Factor VNew Brunswick: Ala221-to-Val substitution results in reduced cofactor activity

We have characterized the factor V protein and cDNA of a patient displaying factor V deficiency (parahemophilia) and correlated the reduced activity with a missense mutation of Ala221-to-Val. Plasma from the subject individual (C1) presented reduced factor V antigen (39% of normal) that displayed reduced activity (approximately 26% of normal). Factor V purified from this individual by standard techniques shows normal migration on sodium dodecyl sulfate gels and a normal pattern of activation by thrombin. Purified antigen from sibling C2 gives a much reduced specific activity of 263 U/mg (17% of normal). Sibling C3, the mother, and the father have antigen within the normal range (57% to 200%) that has approximately normal specific activity. The cDNA encoding the factor Va heavy and light chains of the subject individual was polymerase chain reaction-amplified and sequenced and revealed an A- to-G substitution at position 3 of codon 51 (silent mutation), a C-to-T substitution in position 2 of codon 221 (Ala221-Val), a T-to-C substitution at position 3 of codon 708 (silent mutation), and a G-to-A substitution at position 1 of codon 2185 (Thr2185-Ala). The latter mutation was also observed in control individuals and is proposed to be a possible polymorphism. Restriction analyses demonstrated the presence of one mutant and one normal allele in the father. The subject individual (C1) and sibling C2 carry only the mutant allele. The mother and sibling C3 carry only the normal allele. The inheritance pattern suggests the presence of a missing or nonexpressed allele in the mother that is passed on to all the siblings. Expression of only the mutant allele by the subject individual (C1) and sibling C2 is consistent with reduced factor V antigen and activity in these patients. We have designated this mutant as Factor VNew Brunswick.     

Expression of heparin-binding epidermal growth factor-like growth factor in pancreatic adenocarcinoma.

BACKGROUND: Previous studies demonstrated that heparin-binding epidermal growth factor-like growth factor (HB-EGF) contributes to carcinogenesis and carcinoma progression. In this study, we investigated its expression in human pancreatic adenocarcinoma. METHODS: We immunohistochemically investigated the expression of HB-EGF in 40 cases of pancreatic adenocarcinoma. RESULTS: HB-EGF was only occasionally and faintly expressed in normal and hyperplastic pancreas duct epithelia. In pancreatic adenocarcinoma, 22 (55.0%) of the 40 cases were classified as positive for HB-EGF. Its expression was more frequently observed in cases with a low Ki-67 labeling index, well differentiated. early stage, small size, without lymph node metastasis and low EGF-R expression. CONCLUSION: These results suggest that HB-EGF mainly plays a role in early phase of the progression of pancreatic adenocarcinoma.     

The epidermal growth factor-like domain of recombinant human thrombomodulin exhibits mitogenic activity for Swiss 3T3 cells

Thrombomodulin (TM) is an anticoagulant endothelial cell surface glycoprotein containing six tandem epidermal growth factor (EGF)-like structures. We prepared a recombinant TM peptide (rTME1-6, from R214GHWA to DSGK466 of native TM) composed of these six EGF-like structures and investigated the effect of rTME1-6 peptide on the growth of the Swiss 3T3 fibroblast cell line. It was found that rTME1-6 induced proliferation of Swiss 3T3 cells and accelerated [3H]thymidine uptake into their DNA. [3H]Thymidine uptake increased in a dose- dependent manner, plateauing at 50 ng/mL rTME1-6, which was 1.8 times the control level. rTME1-6 peptide (50 ng/mL) also accelerated the DNA synthesis of human dermal fibroblasts (HDFs), A549 (a human lung cancer cell line), HepG2 (a human hepatocarcinoma cell line), and U937 cells (a human monocytic cell line) to 1.5, 1.6, 1.4, and 1.2 times the control level, respectively. The magnitude of the acceleration of DNA synthesis in Swiss 3T3 induced by rTME1-6 was approximately 20% of that of EGF on a molar basis. The uptake of [3H]thymidine was accelerated synergistically by coculture of the cells with rTME1-6 and insulin, similar to the coculture with EGF and insulin. The effects of rTME1-6 were abolished by addition of polyclonal antihuman TM IgG, whereas the actions of insulin and EGF were not influenced. Glucose uptake in Swiss 3T3 cells also increased 1.6 times over control levels by culture with 50 ng/mL rTME1-6 (1.25 nmol/L), compared with 2.7 times by 10 ng/mL EGF (1.66 nmol/L). Binding of [125I]EGF (0.5 ng/mL, 0.083 nmol/L) by the cells was inhibited by about 60% by addition of an eight-fold molar excess of nonlabeled EGF (0.664 nmol/L), whereas no inhibition of [125I]EGF binding was observed, even in the presence of a 1,000-fold molar excess (83 nmol/L) of rTME1-6. Specific binding of [125I]rTME1-6 on the cells showed a saturation curve, and the apparent concentration of rTME1-6 required for half maximum binding of the peptide on the cells was calculated to be 31.5 ng/mL. Thus, the overall results indicated that the rTME1-6 peptide had mitogenic activity for Swiss 3T3 cells, accelerated DNA synthesis and glucose uptake, and that the mitogenic activity might be mediated by binding of the peptide to a specific site different from the EGF receptor.     

Factor VII R110C: a novel missense mutation (Arg110Cys) in the second epidermal growth factor-like domain causing factor VII deficiency in members of a Japanese family.

This report describes the findings of a genetic analysis of the factor VII (FVII) gene in a Japanese, male patient with FVII deficiency. The proband showed FVII activity level of 25% and FVII antigen level of 28% of the normal value, but he had no severe bleeding episodes. We identified the mutation by direct sequencing of polymerase chain reaction products representing all exons except 1b and their flanking intronic regions of his FVII gene. We detected a single point mutation, a C-->T substitution at nucleotide position 7863 in exon 5, which results in an amino acid replacement of Arg (CGC) to Cys (TGC) at codon 110 in the second epidermal growth factor-like domain. Homozygosity was confirmed in the propositus by loss of a site for the restriction endonuclease Eco47III. Furthermore, his parents, who had moderately reduced levels of factor VII activity and antigen, carried this mutation site as a heterozygote. Although the Arg11O residue is located distal to the tissue factor (TF) in the soluble TF-FVIIa crystal structure, we infer that the replacement of the positively charged and larger Arg residue with a neutral Cys residue may be likely to impair proper folding, resulting in destabilization of the protein structure.     

Aspartyl beta-hydroxylase: in vitro hydroxylation of a synthetic peptide based on the structure of the first growth factor-like domain of human factor IX.

beta-Hydroxylation of aspartic acid is a post-translational modification that occurs in several vitamin K-dependent coagulation proteins. By use of a synthetic substrate comprised of the first epidermal growth factor-like domain in human factor IX and either mouse L-cell extracts or rat liver microsomes as the source of enzyme, in vitro aspartyl beta-hydroxylation was accomplished. Aspartyl beta-hydroxylase appears to require the same cofactors as known alpha-ketoglutarate-dependent dioxygenases. The hydroxylation reaction proceeds with the same stereospecificity and occurs only at the aspartate corresponding to the position seen in vivo. Further purification and characterization of this enzymatic activity should now be possible.     

Identification of epidermal growth factor-like activity in human male reproductive tissues and fluids

Epidermal growth factor-like activity (EGF-LA) has been detected in human seminal plasma in concentrations of 5-150 ngeq/ml (36.4 +/- 2.1, mean +/- SEM), using a heterologous RRA with murine EGF. The samples were obtained from normal, subfertile and azoospermic men, aged 21-50 yr. No correlation was found between EGF concentration and age of donor, sperm count, sperm motility, or period of sexual abstinence before sample collection. High performance liquid chromatography of the seminal plasma resulted in a main peak of EGF-LA which eluted at 29% acetonitrile, compared to 33% for murine EGF. Microsomal membranes were prepared from several tissues from the human male reproductive tract and were tested for their ability to bind radioiodinated murine EGF. Specific EGF binding activity was detectable in testicular membrane preparations but was not detectable in membranes prepared from human prostate, seminal vesicle, epididymis, or spermatozoa. Endogenous EGF-LA was detectable in human testis, seminal vesicle, prostate, and epididymis.     

A Leu55 to Pro substitution in the integrin alphaIIb is responsible for a case of Glanzmann's thrombasthenia

Glanzmann's thrombasthenia (GT) is a hereditary bleeding disorder caused by a quantitative or qualitative defect in the integrin alphaIIbbeta3. A new mutation, a T to C substitution at base 258 in the alphaIIb gene, leading to the replacement of Leu55 with Pro, was found by sequence analysis of a patient's alphaIIb cDNA. In transfection experiments using COS7 cells, the cells co-transfected with the mutated alphaIIb cDNA containing C258 and wild-type beta3 cDNA scarcely expressed the alphaIIbbeta3 complex. The Leu55 to Pro substitution in the alphaIIb gene was found to be responsible for this case of Glanzmann's thrombasthenia.     

Immunohistochemical localization of epidermal growth factor-like activity in the hamster ovary with a polyclonal antibody.

A polyclonal antibody to murine epidermal growth factor (EGF) was generated in rabbits and characterized by RIA, Western blots, and dot blotting. The antibody detected as little as 0.01 ng of mouse EGF in dot blots at 1:100,000 dilution and 5 pg of EGF in RIA at 1:50,000 dilution; it did not cross-react with transforming growth factor-alpha, insulin-like growth factor, or fibroblast growth factor. Ovarian EGF content peaked (17 +/- 2 pg/nonluteal ovary) on Day 1 (estrus as determined by copious vaginal discharge) and declined by DAy 3 as measured by RIA of immunoaffinity-purified ovarian extract. Frozen sections of hamster ovaries were stained immunohistochemically for EGF using a Zymed kit. Intense red staining specific for EGF was localized only in granulosa cells of small (1-2 layers of granulosa cells) and medium (3-6 layers of granulosa cells) preantral follicles; moderate staining was observed in the granulosa and theca cells of small antral follicles. Staining intensity faded in granulosa and theca cells of large antral follicles, especially on Day 4 (proestrus) and disappeared in pyknotic granulosa cells of atretic follicles. Follicular EGF staining peaked on Days 1 and 2 and thereafter declined to low levels. On Day 2, oocytes of the primordial follicles showed distinct coloration. Sections of Day 2 ovary incubated with preneutralized antibody or normal rabbit IgG did not show any coloration. For intact hamsters, 10 micrograms of follicle-stimulating hormone (FSH), twice daily for Days 1 and 2, intensified EGF staining in granulosa cells compared with corresponding untreated Day 3 hamsters, whereas similar treatment with luteinizing hormone for 2 days expanded the interstitium with localized staining of interstitial cells only around follicles with 2 and 3 layers of granulosa cells and lacking theca. Hypophysectomy for 13 days resulted in almost complete absence of EGF-specific staining in the remaining nonatretic follicles; however, exogenous FSH (5 micrograms, twice daily) for 2 days dramatically increased staining intensity associated with newly developed follicles. Luteinizing hormone (0.4 micrograms, twice daily) for 2 days, however, induced significant development of only the interstitium with increased staining of small preantral follicles. These results provide strong evidence for the presence of EGF-like activity in hamster ovarian follicles and suggest that its expression is controlled by gonadotropins, especially FSH.     

Autoantibodies directed against the epidermal growth factor-like domains of thrombomodulin inhibit protein C activation in vitro

Summary No consensus has been obtained about the question whether autoantibodies, in particular antiphospholipid antibodies (aPL), may cause thrombosis by inhibiting thrombomodulin (TM) mediated protein C activation. In order to clarify the mechanism by which autoantibodies inhibit TM-mediated protein C activation, we have screened 12 patients with autoimmune diseases for the presence of circulating autoantibodies inhibiting TM function. In a cross-sectional study we found that IgG fractions from two patients (who were aPL negative) inhibited TM mediated protein C activation in an assay system using purified components. A longitudinal study of six patients with a history of thrombosis of which two were aPL positive showed that all had at some time circulating antibodies inhibiting TM function, suggesting that the presence of these antibodies is transient. Three different TMs were used to identify the epitope of the antithrombomodulin antibodies (aTM): rabbit TM, which contains the entire TM molecule: Solulin, which contains the extracellular part of TM, and rEGF-TM, which contains the six epidermal growth factor (EGF) domains of TM. We showed that the aTM inhibited protein C activation mediated by all three TMs, indicating that the aTM are directed against the region containing the EGF domains. When TM was incorporated in phospholipid vesicles, no inhibition by these aTM could be demonstrated. In addition, protein C activation mediated by cultured endothelial cells (EC) could not be inhibited by aTM. The lack of inhibition of TM in phospholipid vesicles and EC-TM by aTM suggests that aTM only inhibit soluble TM. In conclusion, we demonstrated the transient presence of circulating autoantibodies directed against the region of TM containing the EGF domains in SLE patients with a history of thrombotic complications. We postulate that the presence of antibodies to soluble TM may be, in addition to aPL, a risk factor for the occurrence of thrombosis in patients with autoimmune diseases.