Imaging soft X-ray microscope at Rits Synchrotron Radiation Center

An imaging soft X-ray microscope with zone plates has been installed at Rits SR Center (Ritsumeikan University, Kusatsu, Japan). With this microscope, specimens were set in air, which made it possible to investigate the specimens without breaking the vacuum of the microscope. The specimens can be prefocused with an optical microscope. Dry and wet biospecimens in air were observed. A new optical system was designed to improve the resolution.

The effects of coenzyme Q10 treatment on maternally inherited diabetes mellitus and deafness, and mitochondrial DNA 3243 (A to G) mutation

The characteristic clinical features of diabetes mellitus with mitochondrial DNA (mtDNA) 3243(A-G) mutation are progressive insulin secretory defect, neurosensory deafness and maternal inheritance, referred to as maternally inherited diabetes mellitus and deafness (MIDD). A treatment for MIDD to improve insulin secretory defects and reduce deafness has not been established. The effects of coenzyme Q10 (CoQ10) treatment on insulin secretory response, hearing capacity and clinical symptoms of MIDD were investigated. 28 MIDD patients (CoQ10-DM), 7 mutant subjects with impaired glucose tolerance (IGT), and 15 mutant subjects with normal glucose tolerance (NGT) were treated daily with oral administration of 150 mg of CoQ10 for 3 years. Insulin secretory response, blood lactate after exercise, hearing capacity and other laboratory examinations were investigated every year. In the same way we evaluated 16 MIDD patients (control-DM), 5 mutant IGT and 5 mutant NGT subjects in yearly examinations. The insulin secretory response assessed by glucagon-induced C-peptide secretion and 24 h urinary C-peptide excretion after 3 years in the CoQ10-DM group was significantly higher than that in the control-DM group. CoQ10 therapy prevented progressive hearing loss and improved blood lactate after exercise in the MIDD patients. CoQ10 treatment did not affect the diabetic complications or other clinical symptoms of MIDD patients. CoQ10 treatment did not affect the insulin secretory capacity of the mutant IGT and NGT subjects. There were no side effects during therapy. This is the first report demonstrating the therapeutic usefulness of CoQ10 on MIDD.

The formation of thyrotropin receptor (TSHR) antibodies in a Graves' animal model requires the N-terminal segment of the TSHR extracellular domain

Immunization of AKR/N mice with murine fibroblasts, transfected with the TSH receptor (TSHR) and a murine major histocompatibility complex class II molecule having the same H-2k haplotype (but not either alone), induces immune thyroid disease with the humoral and histological features of human Graves', including the presence of two different TSHR antibodies (TSHRAbs): stimulating TSHRAbs, which cause hyperthyroidism; and TSH-binding-inhibiting immunoglobulins. The primary functional epitope for both types of antibodies in Graves' patients is on the N-terminal portion of the extracellular domain of the TSHR, residues 25 to 165; most require residues 90-165 to express TSHRAb activity, as evidenced in studies using chimeras of the TSHR and lutropin-choriogonadotropin receptor (LH-CGR). To evaluate the role of this region of the TSHR in the formation of Graves' TSHRAbs, we immunized AKR/N mice with fibroblasts transfected with three human TSHR chimeras with residues 9-165 (Mc1+2), 90-165 (Mc2), or 261-370 (Mc4) substituted by equivalent residues of the rat LH-CGR. Mice immunized with the Mc1+2 and Mc2 chimeras, with the N-terminal portion of the extracellular domain of the TSHR substituted by LH-CGR residues, did not develop TSHRAbs. Mice immunized with the Mc4 chimera, having a major portion of the C-terminal portion of the extracellular domain of the TSHR replaced by comparable LH-CGR residues, can develop TSHRAbs. The results suggest that the N-terminal segment of the TSHR extracellular domain is not only a critical functional epitope for Graves' TSHRAbs, but it is important also in their formation in a mouse model of Graves' disease.

Mitochondrial deoxyribonucleic acid 3256C-T mutation in a Japanese family with noninsulin-dependent diabetes mellitus

Accumulating reports indicate a relationship between mitochondrial DNA mutation and impaired glucose-induced insulin secretion leading to a subtype of noninsulin-dependent diabetes mellitus. DNA from a 45-yr-old Japanese woman with noninsulin-dependent diabetes mellitus and muscle atrophy was isolated and studied for mitochondrial DNA mutations. We identified a mitochondrial DNA C-T heteroplasmic mutation at nucleotide position 3256. The mutation was located in the transfer ribonucleic acidLeu in a region conserved in evolution. Eight other members of her family were examined for the mutation. Six of them had the same mutation together with noninsulin-dependent diabetes mellitus, and one teenage boy had the mutation and impaired glucose tolerance. The other family member who did not have this mutation had normal glucose tolerance. The enzyme activity of the mitochondrial oxidative phosphorylation pathway in the muscle of the proband was measured. The enzyme activity was decreased in the proband, especially in complex I. This mutation might be responsible for the abnormal glucose metabolism.

Newly synthesized Rho A, not Ras, is isoprenylated and translocated to membranes coincident with progression of the G1 to S phase of growth-stimulated rat FRTL-5 cells

Ras and Rho are involved in the regulation of signal transduction events governing cell growth and cell proliferation. Protein prenylation is essential for the activation and/or the translocation of these small GTPases; however, protein geranylgeranylation rather than farnesylation is required for G1/S transition. We studied prenylation and translocation of Ras and Rho A during G1/S progression in growth-stimulated rat thyroid FRTL-5 cells. Immunoblot analysis revealed that both Ras and Rho A were detected in membrane fractions at G0. Rho A was eliminated from the membrane fraction during G1 and was not detected on the membrane at mid-G1. Translocation of Rho A from the cytoplasm back to the membranes was observed during late G1 phase. In contrast, Ras remains in the membrane fraction through the cell cycle progression from G1 to S phase. The immunoprecipitation of Rho A from the membrane fraction demonstrated that newly synthesized Rho A, labeled by pulsing cells with [35S]methionine and [35S]cysteine, was geranylgeranylated and associated with the membrane in late G1. These results indicate that Rho A, not Ras, was eliminated from membrane fraction during G1 progression and that newly synthesized Rho A is geranylgeranylated and translocated to membranes during G1/S progression in growth-stimulated FRTL-5 cells.

Geranylgeranylpyrophosphate, a metabolite of mevalonate, regulates the cell cycle progression and DNA synthesis in human lymphocytes

We investigated the role of the intrinsic mevalonate cascade in DNA synthesis and cell cycle progression in human peripheral blood mononuclear cells (PBMC) stimulated by phytohemagglutinin (PHA). PHA stimulated the expression of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase mRNA prior to the DNA synthesis (S phase). Pravastatin, an HMG-CoA reductase inhibitor, inhibited DNA synthesis and blocked the entry to S phase in PHA-stimulated PBMC. Mevalonate restored these inhibitory effects. Thus, we examined two major metabolites of mevalonate, geranylgeranyl-pyrophosphate (GGPP) and farnesyl-pyrophosphate (FPP), using a novel liposome system for uptake into the cells. GGPP, not FPP, restored the pravastatin-induced inhibitions. These data indicated that 1) the intrinsic mevalonate cascade plays critical roles for the entry to S phase and DNA synthesis, and that 2) GGPP is an essential metabolite of mevalonate cascade for cell cycle progression in PBMC stimulated by PHA.

Transcript levels of tandem-arranged alternative oxidase genes in rice are increased by low temperature

We identified two genes for alternative oxidase (AOX) from rice. One AOX gene (designated AOX1a) is located approx. 1.9 kb downstream of another AOX gene (designated AOX1b). Comparison of the genomic and cDNA sequences of the two AOX genes showed that the AOX1a gene is interrupted by three introns, as are AOX genes of other plants. On the other hand, two introns are inserted in the AOX1b gene. The predicted AOX1a and AOX1b precursor proteins consist of 332 and 335 amino acid residues, respectively. A genomic Southern hybridization analysis indicated that rice has several AOX genes other than the two tandem-arranged AOX genes. Steady-state mRNA levels of both of the genes for AOX1a and AOX1b were increased under low temperature (4 degrees C). However, no difference in the pattern of induction of transcription between the genes for AOX1a and AOX1b was observed.

Characterization of monoclonal thyroid-stimulating and thyrotropin binding-inhibiting autoantibodies from a Hashimoto's patient whose children had intrauterine and neonatal thyroid disease

A multiplicity of TSH receptor autoantibodies (TSHRAbs) have been characterized after subcloning heterohybridomas produced from the lymphocytes of a patient who has Hashimoto's thyroiditis and had three children with intrauterine or neonatal hyperthyroidism. Twelve clones produced stimulating TSHRAbs that increased cAMP levels and iodide uptake in rat FRTL-5 thyroid cells and increased cAMP levels in Chinese hamster ovary (CHO) cells transfected with the human TSHR; like 95% of Graves' stimulating TSHRAbs, all 12 have their functional epitope on the N-terminus of the TSHR extracellular domain, requiring residues 90-165 for activity. All 12 bind to human thyroid membranes in the absence, but not the presence, of TSH, but are only weak inhibitors of TSH binding in assays measuring TSH binding-inhibiting Igs (TBIIs). In contrast, 8 different clones produced TSHRAbs that did not increase cAMP levels, but, instead, exhibited significant TBII activity. Four inhibited the ability of TSH or a stimulating TSHRAb to increase cAMP levels and had their functional epitope on the C-terminal portion of the TSHR external domain, residues 261-370, mimicking the properties of blocking TSHRAbs that cause hypothyroidism in patients with idiopathic myxedema. The 4 other TBIIs inhibited the ability of TSH, but not that of a stimulating TSHRAb, to increase cAMP levels, like TBIIs in Graves' patients. The functional epitope for 3 of these Graves'-like TBIIs was residues 90-165; the functional epitope for the fourth was residues 24-89. The fourth also increased arachidonic acid release and inositol phosphate levels in FRTL-5 thyroid cells and exhibited conversion activity, i.e. the ability to increase cAMP levels in the presence of an anti-human IgG. Thus, this TBII exhibited signal transduction activity, unlike the other 3 Graves'-like TBIIs. The patient, therefore, has stimulating TSHRAbs and 3 different types of TBIIs, each with different functional properties and different epitopes on the TSHR.

Epitopes for thyroid stimulating and blocking autoantibodies on the extracellular domain of the human thyrotropin receptor

The majority (97%) of functional epitopes for stimulating thyrotropin receptor (TSHR) antibodies (stimulating TSHRAbs) in a large cohort (n = 59) of Japanese Graves' patients exists on the N-terminal region of the extracellular domain of TSHR, between residues 25 and 165 numbering from the methionine start site. This was determined by measuring the loss of stimulating activity in the Cos-7 cells transfected with TSHR/lutropin-choriogonadotropin receptor (LH-CGR) chimeras wherein TSHR residues 89-165 (Mc2) or 8-165 (Mc1 + 2) are replaced by comparable LH-CGR residues. There is no comparable loss when stimulating TSHRAb activity is measured in an Mc4 chimera, wherein TSHR residues 261 to 370 are replaced. In contrast, immunoglobulin (IgG) preparations from 35 patients with Hashimoto's disease or idiopathic myxedema, who have blocking TSHRAbs causing hypothyroidism, loose blocking TSHRAb activity in the Mc4 chimera, but not the Mc2 or Mc1 + 2 chimeras. Thus, in a large population of Japanese patients with autoimmune thyroid disease caused by TSHR autoantibodies, the major functional epitope for stimulating TSHRAbs is on the N-terminal portion of the TSHR extracellular domain, whereas that for blocking TSHRAbs is on the C-terminal portion of the extracellular domain. To further evaluate the nature of the critical functional epitope between residues 90 to 165, we divided this region approximately in half, creating chimeras Mc2a and Mc2b with, respectively, residues 90-124 or 125-165 replaced by comparable LH-CGR residues. IgGs from all patients tested lost significant stimulating activity using the Mc2a and Mc2b chimeras; however, when present, residual stimulating TSHRAb activity was evident on one or the other half of the region or on both halves, indicating that both segments are required for expression of the stimulating TSHRAb epitope within residues 90-165. Finally, we have identified a complex epitope involving both the N- and C-terminal portion of the extracellular domain that appears to account for the small fraction of stimulating TSHRAbs whose activity is not solely dependent on residues 25 to 165. Thus, using chimeras Mc1 + 2 + 4, with TSHR residues 8-165 and 261-370 substituted, or chimera Mc1 + 2 + 3 + 4, with residues 8-370 substituted, as well as Mc2, Mc1 + 2, and Mc4, we show that the Graves' IgGs which maintain stimulating TSHRAb activity when residues 8-165 of the TSHR are replaced by LH-CGR residues have an epitope involving residues 90-165 and the immunogenic 15mer peptide (YYVFFEEQEDEIIGF), residues, 352-366. Because that peptide can decrease the stimulating TSHRAb activity of these Graves IgGs in assays with the Mc2 chimera alone, we speculate that this complex epitope may be important in an epitope spreading process involved in the formation of stimulating TSHRAbs.

Maintenance of chloroplast-derived sequences in the mitochondrial DNA of Gramineae

Evidence for the transfer of DNA from the chloroplast to the mitochondrion has been reported in many higher plants and, in most cases, the transferred chloroplast genes do not have the ability to encode functional products as a consequence of base substitutions and/or multiple rearrangements. We reported previously that the sequence of one end of a chloroplast-derived (ct-derived) fragment of DNA that contained the rps19 and trnH genes has been maintained in most gramineous plants and that its presence seems to be correlated with gene expression in this region. In the present study, we have investigated whether or not the ct-derived sequences in mitochondrial DNA (mtDNA) from some gramineous plants and species of Oryza are conserved, and whether or not such conservation is related to gene expression in these regions. We identified two junctions between ct-derived and mitochondrial sequences that were conserved among some gramineous plants. Around these regions, we found a ct-derived gene for tRNA and the promoter of a mitochondrial gene on the ct-derived sequences, respectively, and these regions were transcribed through the junctions. This result indicates that the junctions and/or regions that are transcribed and functional in mitochondria have been strongly conserved and maintained during their evolution. In Oryza, some junctions between ct-derived and mitochondrial sequences were conserved and other junctions were not. These variations seem to have been caused by deletions and/or rearrangements, and appear to be specific to the type of genome. In the case of Oryza, the timing of deletions and/or rearrangements of ct-derived sequences is likely to have coincided with the divergence of the various genome types.

Characterization of the gene family for alternative oxidase from Arabidopsis thaliana

We investigated the copy number of the gene for alternative oxidase (AOX) of Arabidopsis thaliana by amplification by PCR and Southern hybridization. These studies indicated that there are at least four copies of the AOX gene in Arabidopsis. We isolated genomic clones containing individual copies (designated as AOX1a, AOX1b, AOX1c and AOX2) of the AOX genes. Interestingly, two of the AOX genes (AOX1a and AOX1b) were located in tandem in a ca. 5 kb region on one of the chromosomes of Arabidopsis. Comparison between genomic and cDNA sequences of the four AOX genes showed that all AOX genes are divided by three introns and the positions of the introns in AOX1a, AOX1b, AOX1c and AOX2 are the same. We examined whether expression of Arabidopsis AOX genes, like the tobacco AOX1a gene, is enhanced by treatment with antimycin A, an inhibitor of complex III in the mitochondrial respiratory chain. We found that, in young plants, the amount of Arabidopsis AOX1a mRNA was dramatically increased by addition of antimycin A, while the transcription of the other three genes (AOX1b, AOX1c and AOX2) did not respond to antimycin A. Amplification by RT-PCR showed that AOX1a and AOX1c were expressed in all organs examined (flowers and buds, stems, rosette, and roots of 8-week old plants). In contrast, transcripts of AOX1b were detected only in the flowers and buds, and transcripts of AOX2 were detected mainly in stems, rosette and roots. These results suggested that transcriptions of the four genes for alternative oxidase of Arabidopsis are differentially regulated.

Glutathione metabolism in mice is enhanced more with hapten-induced allergic contact dermatitis than with irritant contact dermatitis

Cutaneous inflammation induced by electrophilic compounds involves irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD). Reduced glutathione (GSH) and related thiols have been postulated to play important roles in detoxification of electrophilic xenobiotics, protection of tissues against reactive oxygen species, and modulation of immunologic functions in normal and diseased subjects. The dynamic aspects of GSH metabolism, however, and its significance in patients with ICD and ACD remain to be clarified. The current study was carried out to elucidate the pathogenesis and possible involvement of GSH in both types of inflammation. Normal mice and mice sensitized with dinitrochlorobenzene (DNCB) were challenged by cutaneous administration of DNCB, and changes in GSH metabolism in skin and liver were determined. Kinetic analysis revealed that 24 h after challenge with DNCB, levels of hepatic glutathione and its secretion increased more markedly in the sensitized mice than in the unsensitized animals. Administration of buthionine-L-sulfoximine (BSO), a specific inhibitor of GSH synthesis, inhibited the increase in glutathione levels in the liver and the skin of both groups. Histologic examination revealed that cutaneous inflammation was enhanced by BSO more significantly in mice with ACD than with ICD. These results suggest that GSH might play an important role in the suppression of the immune reaction in mice with ACD.

[Surgical treatment for colorectal carcinoma combined with liver cirrhosis]

Surgical treatment for colorectal carcinoma associated with liver cirrhosis is discussed. Resection of this carcinoma is considered safe for patients whose liver function belongs to clinical stage I, II or Grade A, B of Child-Pugh classification or KICG more than 0.06/min. When hepatocellular carcinoma (HCC) is associated and the remnant liver function is feasible, hepatic resection should be undertaken at a favorable opportunity. When risky esophageal varices are present, endoscopic variceal ligation (EVL) or sclerotherapy (EIS) should be performed preoperatively. Lymph node dissection should be restricted to D1 or D2. In the postoperative phase, attention should be paid to maintaining liver function and hepatic circulation. Dobutamine or dopamine is useful for increasing hepatic blood flow. Fresh frozen plasma or platelet transfusion is used when needed.

[Findings of genetic changes in small intestinal carcinomas]

There is now good evidence that a series of genetic lesions in both dominant oncogenes and tumor suppressor genes are involved in the pathogenesis of human digestive tract carcinomas. Small intestinal carcinomas are very rare, accounting for only about 0.19% of all primary gastrointestinal malignant tumors in Japan, so there are few reports investigating genetic changes of small intestinal carcinoma. We analyzed 3 microsatellite loci and the status of K-ras and p53 genes isolated from tumors and surrounding normal tissue samples obtained during surgery. The polymerase chain reaction (PCR) technique used frequent genetic instability to assess differences between tumor and matched DNAs. Replication errors (RERs) were observed in 3 of the 29 cases (10%) of gastric carcinoma and in 11 of the 72 cases (15%) of colorectal carcinoma. None of the 13 (0%) esophageal carcinoma cases showed any RER, but 5 of 11 cases of small intestinal carcinoma (45%) had RERs, reflecting a significantly high incidence. None of the 11 small intestinal carcinoma cases exhibited K-ras gene mutations. Of 7 case amplified successfully by polymerase chain reaction (PCR) in exon 5-8 loci in p53 gene, 2 exhibited abnormally migrated bands in polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. It is thus clear that the genetic carcinogenesis in the small intestine is different from other parts of the digestive tract. These results suggest that genetic instability plays an important role in the pathogenesis of small intestinal carcinomas.

Mechanisms of enhanced production of PGI2 in cultured rat vascular smooth muscle cells enriched with eicosapentaenoic acid

The present investigation was performed to clarify the effect of EPA on PGI2 production in vitro using cultured rat vascular smooth muscle cells (VSMC). To simulate in vivo conditions, a triacylglycerol (TG) emulsified form of EPA was used. An increase in EPA content was achieved without alteration of arachidonic acid concentration. These experiments clearly demonstrated that co-incubation of EPA-TG increased PGI2 production by cultured VSMC in a dose dependent fashion. Among polyunsaturated fatty acid TG examined (docosahexaenoic acid, linoleic acid, oleic acid and EPA), only EPA-TG was effective. Cyclooxygenase (COX) was activated, but neither phospholipase A2 nor PGI2 synthase activity was changed. EPA treatment did not alter the amount of COX-1 and COX-2 protein in VSMC. Addition of antioxidants, such as butylated hydroxytoluene or vitamin E, decreased MDA levels in the medium and cells and reversed the enhanced PGI2 production in EPA rich-VSMC. Therefore, the high polyunsaturation of EPA could generate low levels of lipid peroxides and thereby lead to activation of COX and an increased PGI2 production. Although EPA increased PGI2 production, only a negligible amount of PGI3 was produced by rat aortic tissues. Enhanced production of PGI2 might contribute to the anti-atherogenic effect of EPA.

Glucocorticoid inhibition of fibroblast proliferation and regulation of the cyclin kinase inhibitor p21Cip1

Glucocorticoids inhibit the proliferation of fibroblastic cells in vivo and in culture; however, the molecular mechanism that accounts for this effect has remained obscure. We have undertaken to elucidate the mechanism whereby glucocorticoids decrease the rate of proliferation of mouse L929 fibroblastic cells. Addition of dexamethasone to mid-log phase fibroblasts prolongs G1 phase. This increase in the G1 interval is associated with, and probably due to, inhibition of phosphorylation of the product of the Rb-1 tumor suppressor gene, pRb. Inhibition of pRb phosphorylation by cyclin D-dependent kinases can be demonstrated in vitro. Nevertheless, there is no detectable change in the expression of cyclin D1, cyclin D2, or cyclin D3. Cyclin-dependent kinase-4 (Cdk4) and Cdk6 are not down-regulated in L929 cells after addition of glucocorticoids, and the abundance of cyclin D/Cdk4 complexes does not change. Inhibition of pRb kinase activity is associated with an increase in the abundance of one of the Cdk inhibitors, p21Cip1. The abundance of another cyclin kinase inhibitor, p27Kip1, remains constant. The amount of Cdk4 that is bound to p21Cip1 increases rapidly after addition of dexamethasone, and the activity of Cdk4-pRb kinase decreases in parallel. These results indicate that glucocorticoid inhibition of fibroblast proliferation is due to induction of p21Cip1, which binds to and inactivates cyclinD/Cdk4 complexes. The abundance of p21 mRNA increases about 5-fold within 2 h after addition of dexamethasone. This effect does not obtain in L929 mutants that are null for the glucocorticoid receptor, and a variant that expresses the glucocorticoid receptor from a tetracycline-repressible expression vector demonstrates induction of p21 mRNA only in the absence of tetracycline. Cycloheximide does not block induction of p21 mRNA, and dexamethasone has no detectable effect on the apparent rate of degradation of p21 mRNA. Nuclear run-on transcription of the Cip1 gene increases within 2 h after addition of dexamethasone. This effect can be blocked by tetracycline-mediated repression of the glucocorticoid receptor.

A chloroplast derived trnH gene is expressed in the mitochondrial genome of gramineous plants

We reported previously that the mitochondrial sequence that contains the chloroplast-derived trnH gene has been highly conserved in the region around one terminus of the junction between chloroplast-derived and mitochondrion-specific sequences in most of the gramineous plants analyzed [15]. The results of RT-PCR, northern hybridization, in vitro capping and ribonuclease protection experiments show that the chloroplast-derived trnH gene is transcribed from a putative promoter that is located in the mitochondrion-specific sequence. Gene expression in this region seems to be correlated with the conservation of the sequence at the junction between the chloroplast-derived fragment and the mitochondrion-specific sequence.

Alternative splicing of the FHIT gene in colorectal cancers

In the present study, we examined the status of the FHIT gene in 112 colorectal cancer and 137 colorectal adenoma specimens. In a total of 5 specimens (4 colorectal cancers and 1 colorectal adenoma), a common smaller product was detected in addition to the normal size product. This smaller product had lost exon 4, the 5' noncoding region of the FHIT gene, owing to alternative splicing. Moreover, all of the 5 tumors with alternative splicing were located lower on the rectum than the anterior peritoneal reflection.

Geranylgeranylated rho small GTPase(s) are essential for the degradation of p27Kip1 and facilitate the progression from G1 to S phase in growth-stimulated rat FRTL-5 cells

Cyclin-dependent kinase (Cdk) enzymes are activated for entry into the S phase of the cell cycle. Elimination of Cdk inhibitor protein p27Kip1 during the G1 to S phase is required for the activation process. An inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase prevents its elimination and leads to G1 arrest. Mevalonate and its metabolite, geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate, restore the inhibitory effect of pravastatin on the degradation of p27 and allow Cdk2 activation. By the addition of geranylgeranyl pyrophosphate, Rho small GTPase(s) are geranylgeranylated and translocated to membranes during G1/S progression. The restoring effect of geranylgeranyl pyrophosphate is abolished with botulinum C3 exoenzyme, which specifically inactivates Rho. These results indicate (i) among mevalonate metabolites, geranylgeranyl pyrophosphate is absolutely required for the elimination of p27 followed by Cdk2 activation; (ii) geranylgeranylated Rho small GTPase(s) promote the degradation of p27 during G1/S transition in FRTL-5 cells.

Subtypes of anti-TSH receptor antibodies classified by various assays using CHO cells expressing wild-type or chimeric human TSH receptor

To analyze the heterogeneity of anti-TSH receptor antibodies (TSHRAb), we measured serum TSH-binding inhibitory immunoglobulin (TBII), thyroid-stimulating antibody (TSAb), and thyroid stimulation blocking antibody (TSBAb) activities in 31 patients with positive TSHRAb, using CHO cells expressing wild-type TSHR (WT) or TSHR chimera (Mc2) wherein residues 90-165 were substituted by the LH/CG receptor. Using membranes from WT cells, we detected TBII activity in all 31 patients; 10 (32%), all with TSAb activity only, completely lost TBII activity using Mc2 membranes. TSAb activity was found in 26 sera using WT cells; 20 (77%) completely lost TSAb activity in Mc2 cells. Comparisons of TBII and TSAb activity in WT cells did not exhibit a strong positive correlation (r = 0.52). Of the 20 sera that completely lost TSAb activity in Mc2 cells, 10 retained some TBII activity in Mc2 cells. In each of the sera with retained TBII activity, TSAb activity was recovered in Mc2 cells using the conversion assay, which measures the conversion of a nonstimulating TSHRAb to a TSAb by the action of an anti-human IgG. Additionally, the TBII and conversion assay values in Mc2 cells exhibited a strong positive correlation (r = 0.86). Of the 31 sera, TSBAb was found in 7 samples, with no difference in WT and Mc2 cells. TBII activity was detected in all 7 sera with WT cells; TSAb activity in only 2. In the 5 sera with TSBAb but no TSAb activity, and with only a minimal or no decrease in TBII activity in Mc2 cell membranes, the in vitro conversion assay uncovered TSAb activity. Analyzing these data, we classify the sera into 5 groups containing multiple, different TSHR autoantibodies, including two different TSAbs, three different TBIIs, and one nonfunctional antibody. The heterogeneity of TBIIs as well as TSAbs provides a basis to explain the lack of correlation between TBII and TSAb activities in some past studies of Graves' sera.