MicroRNA (miRNA) cloning analysis reveals sex differences in miRNA expression profiles between adult mouse testis and ovary

MicroRNAs (miRNAs) are endogenous non-coding small RNAs that can regulate the expression of complementary mRNA targets. Identifying tissue-specific miRNAs is the first step toward understanding the biological functions of miRNAs, which include the regulation of tissue differentiation and the maintenance of tissue identity. In this study, we performed small RNA library sequencing in adult mouse testis and ovary to reveal their characteristic organ- and gender-specific profiles and to elucidate the characteristics of the miRNAs expressed in the reproductive system. We obtained 10,852 and 11 744 small RNA clones from mouse testis and ovary respectively (greater than 10,000 clones per organ), which included 6630 (159 genes) and 10,192 (154 genes) known miRNAs. A high level of efficiency of miRNA library sequencing was achieved: 61% (6630 miRNA clones/10,852 small RNA clones) and 87% (10,192/11,744) for adult mouse testis and ovary respectively. We obtained characteristic miRNA signatures in testis and ovary; 55 miRNAs were detected highly, exclusively, or predominantly in adult mouse testis and ovary, and discovered two novel miRNAs. Male-biased expression of miRNAs occurred on the X-chromosome. Our data provide important information on sex differences in miRNA expression that should facilitate studies of the reproductive organ-specific roles of miRNAs.

PIASxbeta is a key regulator of osterix transcriptional activity and matrix mineralization in osteoblasts

We recently reported that tensile stress induces osteoblast differentiation and osteogenesis in the mouse calvarial suture in vitro. Using this experimental system, we identified PIASxbeta, a splice isoform of Pias2, as one of the genes most highly upregulated by tensile stress. Further study using cell culture revealed that this upregulation was transient and was accompanied by upregulation of other differentiation markers, including osterix, whereas expression of Runx2 was unaffected. Runx2 and osterix are the two master proteins controlling osteoblast differentiation, with Runx2 being upstream of osterix. Targeted knockdown of PIASxbeta by small interfering RNA (siRNA) markedly suppressed osteoblastic differentiation and matrix mineralization, whereas transient overexpression of PIASxbeta caused the exact opposite effects. Regardless of PIASxbeta expression level, Runx2 expression remained constant. Reporter assays demonstrated that osterix enhanced its own promoter activity, which was further stimulated by PIASxbeta but not by its sumoylation-defective mutant. NFATc1 and NFATc3 additionally increased osterix transcriptional activity when co-transfected with PIASxbeta. Because osterix has no consensus motif for sumoylation, other proteins are probably involved in the PIASxbeta-mediated activation and NFAT proteins may be among such targets. This study provides the first line of evidence that PIASxbeta is indispensable for osteoblast differentiation and matrix mineralization, and that this signaling molecule is located between Runx2 and osterix.

MMP-9 antisense oligodeoxynucleotide exerts an inhibitory effect on osteoclastic bone resorption by suppressing cell migration

We have previously shown that matrix metalloproteinases (MMPs) play a role in osteoclastic bone resorption by facilitating migration of osteoclastic cells toward bone surface through matrices. Of MMPs identified so far, MMP-9 is likely the most important proteinase for the action, since osteoclasts express this enzyme at a tremendously high level. However, no direct evidence has been provided to demonstrate its contribution to bone resorption. In this study, to address this point, we used an MMP-9 antisense phosphothiorate oligodeoxynucleotide (S-ODN), which was shown to inhibit the protein synthesis of MMP-9 efficiently. We demonstrated that the antisense S-ODN inhibited osteoclastic pit formation on matrigel-coated dentine slices in a concentration-dependent manner with a maximum reduction of total pit volume by 53% at 10 microM. These results, taken together, suggest that MMP-9 is involved in osteoclastic bone resorption process possibly by facilitating migration of osteoclasts through proteoglican-rich matrices.

Serologic evidence for hepatitis E virus infection in mongoose

Although pig and wild boar are considered to be the reservoirs of hepatitis E virus (HEV) in Japan, the spread of HEV to other animals is unknown. Serum samples from 84 mongooses (Small Asian mongoose; Herpestes javanicus) collected in Okinawa, Japan were examined for antibodies to HEV by enzyme-linked immunosorbent assay and RNA was analyzed by reverse transcription-polymerase chain reaction. Seven (8.3%) of 84 mongooses were positive for IgG antibodies to HEV, and the antibody-positive rate increased with body weight and size, whereas HEV RNA was not detected in these samples. These results are consistent with the possibility that mongooses in Okinawa are occasionally infected with HEV; however, they are not considered the major zoonotic reservoir of HEV.

Homeobox protein MSX2 acts as a molecular defense mechanism for preventing ossification in ligament fibroblasts

Ligaments and tendons are comprised of tough yet flexible connective tissue. Little is known, however, about the precise characteristics of the cells in ligaments and tendons due to the absence of specific markers and cell lines. We recently reported a periodontal ligament cell line, PDL-L2, with suppressed Runx2/Osf2 transcriptional activity and an inability to form mineralized nodules. The present study demonstrates that the homeobox protein Msx2 is a key factor in suppressing those two functions. Msx2 colocalizes with Runx2/Osf2 and suppresses its activity cooperatively, acting with another corepressor, TLE1, as a complex to recruit histone deacetylase 1 activity. Reverse transcription-PCR and in situ hybridization demonstrated that Msx2 expression is higher in periodontal ligament and tendon cells than in osteoblasts. Stable reduction of Msx2 expression in PDL-L2 cells induces osteoblastic differentiation, thereby causing matrix mineralization. Conversely, stable, forced Msx2 expression in MC3T3-E1 cells prevented osteoblast differentiation and matrix mineralization. Msx2-induced suppression of osteoblast differentiation was repressed by bone morphogenetic protein 2. In addition, Msx2 was downregulated in a symptom- and calcification-dependent manner at the affected region in patients with ossification of the posterior longitudinal ligament. Our findings indicate that Msx2 plays a central role in preventing ligaments and tendons from mineralizing.

Recruitment of osteoclasts in the mandible of osteopetrotic (op/op) mice

Osteoclasts in osteopetrotic (op/op) mice are substantially reduced by the absence of functional activities of macrophage colony-stimulating factor (M-CSF). However, it is known that osteoclasts appear in op/op skeletal bones with aging, although the molecular mechanism for this is unknown. In order to investigate osteoclastic recruitment in the jaw bones of op/op mice, osteoclastic distribution was analysed for 2 yr after birth by histochemistry for tartrate-resistant acid phosphatase activity and immunohistochemistry for cathepsin K. Osteoclasts in op/op mandibular bones decreased rapidly in number after birth and disappeared by 3 d, although there was no difference in the osteoclastic distribution between op/op and normal littermates at birth. At 2 wk, osteoclasts began to reappear around op/op tooth germs, where no apparent connective tissue layer intervened between tooth germs and bone trabeculae. They increased in number and were scattered over the mandible, reaching a maximum at 8 wk, when periodontal ligament-like structures were recognizable around incisor germs. Osteoclasts then again decreased gradually, and after 62 wk few osteoclasts were seen in op/op mandibular bones, whose marrow space disappeared. These findings suggest that osteoclasts are recruited in an M-CSF-independent manner in op/op mandibles, especially in areas around tooth germs.

[Advanced lung cancer of performance status 3 successfully treated by gefitinib--a case report]

The prognosis in cases of advanced lung cancer with poor performance status is poor. We report here a patient with advanced non-small cell lung cancer of performance status 3 who had severe cancer-induced pain, which was not controlable with morphine and radiation therapy. The cancer was successfully treated by oral administration of gefitinib (250 mg/day) without serious adverse effects of worsening of quality of life. Not only was the tumor controlled but rapid relief of severe cancer-induced pain was achieved.

Tensile stress induces alpha-adaptin C production in mouse calvariae in an organ culture: possible involvement of endocytosis in mechanical stress-stimulated osteoblast differentiation

We previously demonstrated that tensile stress (TS)-induced osteoblast differentiation eventually led to osteogenesis in an organ culture of mouse calvarial sutures. In the present study, we employed RNA-fingerprinting using an arbitrarily primed polymerase chain reaction (RAP-PCR) to identify alpha-adaptin C, a component of the endocytosis machinery AP2, as a TS-inducible gene. Protein production, as well as the gene expression of alpha-adaptin C, was induced by TS as early as 3 h following the initiation of loading. In situ hybridization and immunohistochemical analysis revealed that the induction of alpha-adaptin C mostly occurred in fibroblastic cells in the sutures, suggesting that it precedes TS-induced osteoblast differentiation. Consistent with this result, TS significantly increased the number of coated pits (CPs) and coated vesicles (CVs) in the undifferentiated fibroblastic cells but not in the osteoblastic cells around calvarial bones. Further, TS-induced osteoblast differentiation was suppressed when endocytosis was inhibited by potassium depletion. These results, taken together, suggest that TS accelerates osteoblast differentiation and osteogenesis, possibly through the induction of the alpha-adaptin C expression and consequent activation of receptor-mediated endocytosis.

A cell line with characteristics of the periodontal ligament fibroblasts is negatively regulated for mineralization and Runx2/Cbfa1/Osf2 activity, part of which can be overcome by bone morphogenetic protein-2

The periodontal ligament (PDL) is a connective tissue located between the cementum of teeth and the alveolar bone of the mandibula. It plays an integral role in the maintenance and regeneration of periodontal tissue. The cells responsible for maintaining this tissue are thought to be fibroblasts, which can be either multipotent or composed of heterogenous cell populations. However, as no established cell lines from the PDL are available, it is difficult to assess what type of cell promotes all of these functions. As a first step to circumvent this problem, we have cloned and characterized cell lines from the PDL from mice harboring a temperature-sensitive SV 40 large T-antigen gene. RT-PCR and in situ hybridization studies demonstrated that a cell line, designated PDL-L2, mimics the gene expression of the PDL in vivo: it expresses genes such as alkaline phosphatase, type I collagen, periostin, runt-related transcription factor-2 (Runx2) and EGF receptor, but does not express genes such as bone sialoprotein and osteocalcin. Unlike osteoblastic cells and a mixed cell population from the PDL, PDL-L2 cells do not produce mineralized nodules in the mineralization medium. When PDL-L2 cells were incubated in the presence of recombinant human bone morphogenetic protein-2 alkaline phosphatase activity increased and mineralized nodules were eventually produced, although the extent of mineralization is much less than that in osteoblastic MC3T3-E1 cells. Furthermore, PDL-L2 cells appeared to have a regulatory mechanism by which the function of Runx2 is normally suppressed.

Tamoxifen agonism and estrogen antagonism of c-fos gene promoter activity through non-consensus-responsive elements in MC3T3-E1 osteoblasts

We find that the activity of a 0.4-kb human c-fos gene promoter (-404/+41), which lacks consensus estrogen-responsive elements (EREs), is regulated by estrogen receptor (ER) ligands in MC3T3-E1 osteoblastic cells through ERs in a manner distinct from ERE-mediated regulation. When ERalpha is coexpressed, both estrogens and antiestrogens upregulate promoter activity. When ERbeta is coexpressed, however, three tested antiestrogens affect c-fos promoter activity, with tamoxifen exerting the greatest effect, while estrogens have no such effect. The tamoxifen agonism through ERbeta is antagonized by 17beta-estradiol, while the 17beta-estradiol agonism through ERalpha is canceled by excess-level coexpression of ERbeta. Deletion analysis revealed that the sequence -206/-110 plays a crucial role in the ERbeta-mediated tamoxifen agonism. Interestingly, there is no ERbeta-mediated tamoxifen agonism when nonosteoblastic cells are tested. Taken together, these results suggest that the transcription of the c-fos gene is regulated by ER ligands possibly through non-ERE elements in ligand structure-, cell type-, and ER subtype-dependent manners.

Brefeldin A inhibits osteoclastic bone resorption through induction of apoptosis

Brefeldin A (BFA), a fungal metabolite with a macrocyclic lactone structure, has been developed for the treatment of cancer, and its major biological activity is the inhibition of intracellular protein transport from the endoplasmic reticulum to the cis-Golgi apparatus. In this study, we investigated the effect of BFA on osteoclastic pit formation in vitro. BFA reduced pit formation in a concentration-dependent manner, and the IC50 values on the pit number and the pit volume were 11.3 +/- 2.2 and 13.3 +/- 2.0 nM, respectively. In parallel with the inhibitory effect on pit formation, BFA also reduced the cell viability of osteoclasts-enriched bone cells with an IC50 value of 13.9 +/- 2.2 nM. These results suggest that the inhibition of bone resorption by BFA is caused by the induction of osteoclast cell death. BFA at a concentration of 100 nM induced DNA fragmentation in purified osteoclasts, assessed by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and DNA ladder formation, demonstrating that BFA induces cell death of osteoclasts in an apoptotic manner. In addition, the accumulation of p53 proteins to the nuclei was observed in the osteoclasts treated with 100 nM BFA. These results, taken together, suggest that BFA inhibits osteoclastic bone resorption by inducing apoptosis in osteoclasts through a p53-dependent mechanism.

Potential role of Gab1 and phospholipase C-gamma in osmotic shock-induced glucose uptake in 3T3-L1 adipocytes

Osmotic shock induces GLUT4 translocation and glucose uptake through a mechanism independent of PI 3-kinase, but dependent on tyrosine phosphorylation of cellular proteins. To identify the tyrosine phosphorylated proteins required for osmotic shock-stimulated glucose uptake, we examined tyrosine phosphorylation of candidate proteins, and found that the 60-80kDa species including paxillin and the 120-130kDa species including p130Cas, PYK2, FAK and Gab1 were tyrosine-phosphorylated in response to osmotic shock. Inhibition of actin polymerization by cytochalasin D significantly decreased the tyrosine phosphorylation of paxillin, p130Cas, PYK2 and FAK but not Gab1, but had no effect on 2-deoxyglucose (DOG) uptake, suggesting a role for Gab1 in osmotic shock-induced glucose transport. Also, we found that osmotic shock increases the association of phospholipase C-gamma (PLC-gamma) with Gab1 and stimulates tyrosine phosphorylation of PLC-gamma itself. The PLC inhibitor, U73122, inhibited osmotic shock-induced 2-DOG uptake. These results suggest that tyrosine phosphorylation of Gab1 and subsequent recruitment and activation of PLC-gamma may play a role in osmotic shock-induced glucose transport.

Cloning and characterization of the functional promoter of mouse estrogen receptor beta gene

The recently discovered estrogen receptor beta (ERbeta) exhibits some properties distinct from those of the classical estrogen receptor, ERalpha. To elucidate the mechanism underlying the regulation of ERbeta gene expression, we cloned and characterized the 5'-flanking (promoter) region of the mouse ERbeta (mERbeta) gene. A TATA-like motif was found in the 5'-flanking region, and transcription initiation sites were mapped 24 bp and 27 bp downstream from the motif by primer extension analysis and 5'-rapid amplification of cDNA ends. The mERbeta promoter contains several putative cis-acting elements, many of which are also found in the mouse ERalpha promoter. Therefore, the expression of both ERs may be partially regulated by a common mechanism. Luciferase assays revealed that the mERbeta promoter activity paralleled the endogenous expression levels of mERbeta in several cell lines. Successive 5'-deletion analyses showed that element(s) critical for its basal activity and negative regulatory element(s) are located in the sequences -90/+33 and -505/-372, respectively. The characterization of the mERbeta promoter will allow further studies to investigate the transcriptional regulation of mERbeta.

Pioglitazone ameliorates tumor necrosis factor-alpha-induced insulin resistance by a mechanism independent of adipogenic activity of peroxisome proliferator--activated receptor-gamma

Tumor necrosis factor (TNF)-alpha is one of the candidate mediators of insulin resistance associated with obesity, a major risk factor for the development of type 2 diabetes. The insulin resistance induced by TNF-alpha is antagonized by thiazolidinediones (TZDs), a new class of insulin-sensitizing drugs. The aim of the current study was to dissect the mechanism whereby pioglitazone, one of the TZDs, ameliorates TNF-alpha-induced insulin resistance in 3T3-L1 adipocytes. Pioglitazone restored insulin-stimulated 2-deoxyglucose (DOG) uptake, which was reduced by TNF-alpha, with concomitant restorations in tyrosine phosphorylation and protein levels of insulin receptor (IR) and insulin receptor substrate (IRS)-1, as well as association of the p85 regulatory subunit of phosphatidylinositol (PI) 3-kinase with IRS-1 and PI 3-kinase activity. Adenovirus-mediated gene transfer of either wild-type human peroxisome proliferator-activated receptor (PPAR)-gamma2 or a mutant carrying a replacement at the consensus mitogen-activated protein kinase phosphorylation site (hPPAR-gamma2-S112A) promoted adipogenesis of 3T3-L1 fibroblasts and restored TNF-alpha-induced decrease of triglyceride in adipocytes as effectively as pioglitazone. Overexpression of the PPAR-gamma proteins in TNF-alpha-treated adipocytes restored protein levels of IR/IRS-1, but did not improve insulin-stimulated tyrosine phosphorylation of IR/IRS-1 or insulin-stimulated 2-DOG uptake. These results indicate that the ability of pioglitazone to restore insulin-stimulated tyrosine phosphorylation of IR/IRS-1, which is necessary for amelioration of TNF-alpha-induced insulin resistance, may be independent of the adipogenic activity of PPAR-gamma that regulates protein levels of IR/IRS-1.

Quantification of the expression levels of lysosomal cysteine proteinases in purified human osteoclastic cells by competitive RT-PCR

Cathepsin K is a lysosomal cysteine proteinase (LCP) predominantly expressed in osteoclasts. This study was conducted to evaluate the importance of human cathepsin K for osteoclastic bone resorption relative to that of other LCPs. To accomplish this, we quantitatively determined the expression levels of major LCPs (cathepsins B, K, L, and S) in human osteoclastic cells by using competitive RT-PCR. Giant cell tumor of bone (GCT) was used as a source of human osteoclastic cells, since the tissue was shown to contain a large number of cells satisfying the criteria for typical osteoclasts. The involvement of LCPs in the bone-resorption process by the GCT cells was confirmed by showing that trans-epoxysucciny-L-leucylamido-(4-guanidino) butane (E-64), a nonselective cysteine proteinase inhibitor, exerted an inhibitory effect on the pit formation. We isolated osteoclast-like cells (OLCs) positive for tartrate-resistant acid phosphatase (TRAP) and cathepsin K from the GCT tissue to a degree of almost 95% purity. In these cells, the expression of cathepsin K was shown to be approximately 20-, 130-, and 410-fold stronger than that of cathepsins B, L, and S, respectively. A similar result was obtained when human bone marrow cells in culture were used as another source of OLCs. Further, we found that cathepsin K was expressed in OLCs far more strongly than in several human nonosteoclastic cells including osteoblastic cell lines. The abundant and selective expression of cathepsin K in OLCs relative to that of other LCPs suggests that cathepsin K is mainly responsible for osteoclastic degradation of human bone matrix.

Tensile stress induces bone morphogenetic protein 4 in preosteoblastic and fibroblastic cells, which later differentiate into osteoblasts leading to osteogenesis in the mouse calvariae in organ culture

Mechanical stress is an important factor controlling bone remodeling, which maintains proper bone morphology and functions. However, the mechanism by which mechanical stress is transduced into biological stimuli remains unclear. Therefore, the purpose of this study is to examine how gene expression changes with osteoblast differentiation and which cells differentiate into osteoblasts. Tensile stress was applied to the cranial suture of neonatal mouse calvaria in a culture by means of helical springs. The suture was extended gradually, displaying a marked increase in cell number including osteoblasts. A histochemical study showed that this osteoblast differentiation began in the neighborhood of the existing osteoblasts, which can be seen by 3 h. The site of osteoblast differentiation moved with time toward the center of the suture, which resulted in an extension of osteoid. Scattered areas of the extended osteoid were calcified by 48 h. Reverse-transcription polymerase chain reaction (RT-PCR) revealed that tensile stress increased bone morphogenetic protein 4 (BMP-4) gene expression by 6 h and it remained elevated thereafter. This was caused by the induction of the gene in preosteoblastic cells in the neighborhood of osteoblasts and adjacent spindle-shaped fibroblastic cells. These changes were evident as early as 3 h and continued moving toward the center of the suture. The expression of Cbfa1/Osf-2, an osteoblast-specific transcription factor, followed that of BMP-4 and those cells positive with these genes appeared to differentiate into osteoblasts. These results suggest that BMP-4 may play a pivotal role by acting as an autocrine and a paracrine factor for recruiting osteoblasts in tensile stress-induced osteogenesis.

Tensile stress induced osteoblast differentiation and osteogenesis in mouse calvarial suture in culture: possible involvement of BMP-4 and other genes

Mechanical stress is one of the most potent inducer of bone formation. The mechanism by which cells receive and transduce the signal into osteogenesis, however, remains unknown. Previous studies have demonstrated that mechanical stress causes changes in expression levels of many genes in osteoblasts and osteocytes both in vivo and in vitro. However, none of these changes are specific to bone cells. Moreover it is not clear which types of cells contributed to the increased osteoblasts induced by mechanical stress. The purpose of this study, therefore, was to identify which cells differentiate into osteoblasts and to examine how the expression of genes that are specific to osteogenic cells changes.

Differential effects of palmitate on glucose uptake in rat-1 fibroblasts and 3T3-L1 adipocytes

Non-esterified fatty acids are thought to be one of the causes for insulin resistance. However, the molecular mechanism of fatty acid-induced insulin resistance is not clearly known. In this study, we first examined the effect of palmitate on insulin signaling in 3T3-L1 adipocytes. We found that 1h treatment with 1 mmol/l palmitate had no effect on insulin binding, tyrosine phosphorylation of insulin receptors, 185 kDa proteins and Shc, and PI3 kinase activity in 3T3-L1 adipocytes. Then, the effects of palmitate on MAP kinase activity and glucose uptake in fully differentiated 3T3-L1 adipocytes were compared with those in poorly differentiated 3T3-L1 cells and in HIRc-B cells. Palmitate treatment had no effect on MAP kinase activity in fully differentiated 3T3-L1 adipocytes, while it inhibited MAP kinase in poorly differentiated 3T3-L1 cells and HIRc-B cells. Glucose transport in 3T3-L1 adipocytes treated with palmitate for 1 h, 4 h and 16 h was higher than that in control cells, but palmitate treatment caused a rightward shift of the insulin-dose responsive curve for glucose uptake in HIRc-B cells. Palmitate treatment did not significantly affect basal and insulin-stimulated GLUT4 translocation. When the cells were treated with PD98059, a specific MEK inhibitor, insulin-stimulated glucose uptake was not affected in 3T3-L1 adipocytes, while it was almost completely inhibited in HIRc-B cells. These results suggest the primary effect of palmitate on adipocytes may not involve insulin resistance of adipocytes themselves.

Breast cancer cells express cathepsins B and L but not cathepsins K or H

Lysosomal cysteine proteinases (cathepsins) are considered to play a role in bone degradation mediated by metastatic breast cancers. To evaluate which cathepsin contributes to the osteolysis, we quantitatively determined the expression levels of four cathepsins in two breast cancer cell lines, MCF-7 and MDA-MB-231, by competitive RT-PCR. Cathepsin K, which is the most abundant cathepsin in osteoclasts, was not detected in either cell lines. We also failed to detect cathepsin H mRNA. By contrast, we found significant expression of cathepsins B and L in both cell lines. By Northern blot analysis cathepsin B mRNA was detected in a single form in these cells, whereas osteoclasts contained multiple forms of the mRNA. Cathepsin B protein was also detected by Western blotting as a single immunoreactive band corresponding to its mature enzyme. These findings suggest that osteolysis associated with metastatic breast cancers takes place in a different way from osteoclast-mediated bone resorption.

Matrix metalloproteinases and lysosomal cysteine proteases in osteoclasts contribute to bone resorption through distinct modes of action

The effects of inhibitors of matrix metalloproteinases (MMPs) and lysosomal cysteine proteases on osteoclastic pit formation in dentine slices were investigated. A nonspecific cysteine protease inhibitor, E-64, inhibited pit formation on naked slices in a concentration-dependent manner, and at 10 microM E-64 reduced the pit volume by 70%. However, up to 10 microM of the MMP inhibitor, BB-94, did not show any inhibition of pit formation. On the other hand, on slices coated with reconstituted basement membrane, both BB-94 and E-64 at 10 microM showed a marked decrease in pit volume by 73% and 68%, respectively. By a combination of treatment with both BB-94 and E-64, pit formation could be completely suppressed. These results suggest that MMPs are necessary for the migration of precursor and/or immature osteoclasts to bone surface through basement membranes, while cysteine proteases are essential for the osteoclastic degradation of bone collagen.

IRS pleckstrin homology domains bind to acidic motifs in proteins

Using a yeast two-hybrid system, we identified several proteins that interact with the PH domains in IRS-1 and IRS-2, including Lon protease, myeloblast protein, and nucleolin. Although the roles of these molecules in insulin action are not yet known, each protein contained an acidic motif that interacted with the PH domain of IRS-2. However, only the acidic motif in nucleolin bound to IRS-1, suggesting that the PH domain in IRS-1 and IRS-2 are not identical. Moreover, synthetic peptides based on the acidic motif in Lon protease and myeloblast protein inhibited the binding of nucleolin to the PH domain of IRS-2 but not to the PH domain of IRS-1, confirming the selectivity of these PH domains. The ability to bind acidic motifs may be a specific function of the PH domain in IRS proteins, because the PH domains in betaARK, phospholipase Cgamma, or spectrin did not bind nucleolin. In 32D cells, nucleolin bound to both IRS-1 and IRS-2, and expression of the acidic motif of nucleolin inhibited insulin-stimulated tyrosine phosphorylation of IRS-1 and IRS-2. These results suggest that the binding of acidic motifs to the PH domain of IRS-1 and IRS-2 disrupts coupling to the activated insulin receptor. Our results are consistent with the hypothesis that the PH domain in the IRS proteins may ordinarily bind acidic peptide motifs in membrane proteins or other acidic membrane elements that couple IRS proteins to activated membrane receptors.

Suppression of prostanoid formation and regulation of peripheral circulation after surgery using thrombin inhibitor (MD805)

We studied the effects of thrombin generation due to surgical stress on prostanoid formation and peripheral circulation in anesthetized dogs. Three experimental groups were used, consisting of a control group (group 1), a thoracotomized group (group 2), and a thoracotomized group treated with thrombin inhibitor (MD805: a synthetic arginine derivative) (group 3). The plasma concentrations of thrombin-antithrombin III complex (TAT) and prostanoids were measured along with the hemodynamic parameters. The plasma concentrations of TAT and thromboxane B2 significantly increased 1h after a thoracotomy in group 2. However, neither concentration increased after a thoracotomy in group 3. The flow ratio of the brachial and femoral arteries to cardiac output significantly decreased 1h after a thoracotomy in group 2. This study indicates that thromboxane A2 was thus synthesized by the stimulation of endogenous thrombin, while it also reduced the peripheral blood flow after surgery.

Involvement of heat shock protein 90 in the degradation of mutant insulin receptors by the proteasome

We previously reported three families with type A insulin-resistant syndrome who had mutations, either Asp1179 or Leu1193, in the kinase domain of the insulin receptor. The extreme insulin resistance of these patients was found to be caused by the decreased number of insulin receptors on the cell surface, due to the intracellular rapid degradation (Imamura, T., Takata, Y., Sasaoka, T., Takada, Y., Morioka, H., Haruta, T., Sawa, T., Iwanishi, M., Yang, G. H., Suzuki, Y., Hamada, J., and Kobayashi, M. (1994) J. Biol. Chem. 269, 31019-31027). In the present study, we first examined whether these mutations caused rapid degradation of unprocessed proreceptors, using the exon 13 deleted mutant insulin receptors (DeltaEx13-IR), which were accumulated in the endoplasmic reticulum as unprocessed proreceptors. The addition of Asp1179 or Leu1193 mutation to DeltaEx13-IR caused accelerated degradation of the unprocessed DeltaEx13-IR in the transfected COS-7 cells. Next, we tested whether these mutant receptors were degraded by the proteasome. Treatment with proteasome inhibitors Z-Leu-Leu-Nva-H (MG-115) or Z-Leu-Leu-Leu-H (MG-132) prevented the accelerated degradation of these mutant receptors, resulting in increased amounts of the mutant receptors in the COS-7 cells. Essentially the same results were obtained in the patient's transformed lymphocytes. Finally, we found that these mutant receptors bound to heat shock protein 90 (Hsp90). To determine whether Hsp90 played an important role in the accelerated receptor degradation, we examined the effect of anti-Hsp90 antibody on the mutant receptor degradation. The microinjection of anti-Hsp90 antibody into cells prevented the accelerated degradation of both Asp1179 and Leu1193 mutant insulin receptors. Taken together, these results suggest that Hsp90 is involved in dislocation of the mutant insulin receptors out of the endoplasmic reticulum into the cytosol, where the mutant receptors are degraded by the proteasome.