Thrombospondin-1 is an endogenous substrate of cereblon responsible for immunomodulatory drug-induced thromboembolism

ABSTRACT

Immunomodulatory drugs (IMiDs) are key drugs for treating multiple myeloma and myelodysplastic syndrome with chromosome 5q deletion. IMiDs exert their pleiotropic effects through the interaction between cell-specific substrates and cereblon, a substrate receptor of the E3 ubiquitin ligase complex. Thus, identification of cell-specific substrates is important for understanding the effects of IMiDs. IMiDs increase the risk of thromboembolism, which sometimes results in fatal clinical outcomes. In this study, we sought to clarify the molecular mechanisms underlying IMiDs-induced thrombosis. We investigated cereblon substrates in human megakaryocytes using liquid chromatography-mass spectrometry and found that thrombospondin-1 (THBS-1), which is an inhibitor of a disintegrin-like and metalloproteinase with thrombospondin type 1 motifs 13, functions as an endogenous substrate in human megakaryocytes. IMiDs inhibited the proteasomal degradation of THBS-1 by impairing the recruitment of cereblon to THBS-1, leading to aberrant accumulation of THBS-1. We observed a significant increase in THBS-1 in peripheral blood mononuclear cells as well as larger von Willebrand factor multimers in the plasma of patients with myeloma, who were treated with IMiDs. These results collectively suggest that THBS-1 represents an endogenous substrate of cereblon. This pairing is disrupted by IMiDs, and the aberrant accumulation of THBS-1 plays an important role in the pathogenesis of IMiDs-induced thromboembolism.

GPAM mediated lysophosphatidic acid synthesis regulates mitochondrial dynamics in acute myeloid leukemia

Metabolic alterations, especially in the mitochondria, play important roles in several kinds of cancers, including acute myeloid leukemia (AML). However, AML-specific molecular mechanisms that regulate mitochondrial dynamics remain elusive. Through the metabolite screening comparing CD34⁺ AML cells and healthy hematopoietic stem/progenitor cells, we identified enhanced lysophosphatidic acid (LPA) synthesis activity in AML. LPA is synthesized from glycerol-3-phosphate by glycerol-3-phosphate acyltransferases (GPATs), rate-limiting enzymes of the LPA synthesis pathway. Among the four isozymes of GPATs, glycerol-3-phosphate acyltransferases, mitochondrial (GPAM) was highly expressed in AML cells, and the inhibition of LPA synthesis by silencing GPAM or FSG67 (a GPAM-inhibitor) significantly impaired AML propagation through the induction of mitochondrial fission, resulting in the suppression of oxidative phosphorylation and the elevation of reactive oxygen species. Notably, inhibition of this metabolic synthesis pathway by FSG67 administration did not affect normal human hematopoiesis in vivo. Therefore, the GPAM-mediated LPA synthesis pathway from G3P represents a critical metabolic mechanism that specifically regulates mitochondrial dynamics in human AML, and GPAM is a promising potential therapeutic target.

[TIM-3 signaling hijacks the canonical Wnt/β-catenin pathway to maintain cancer stemness in human acute myeloid leukemia]

Acute myeloid leukemia (AML) is one of the most common hematologic malignancies derived from self-renewing and highly propagating leukemic stem cells (LSCs). We have previously identified T-cell immunoglobulin mucin-3 (TIM-3) as an AML LSC-specific surface molecule by comparing the gene expression profiles of LSCs and hematopoietic stem cells (HSCs). TIM-3 expression clearly discriminates LSCs from HSCs within the CD34⁺CD38^- stem cell fraction. Furthermore, AML cells secrete galectin-9 (Gal-9, a TIM-3 ligand) in an autocrine manner, resulting in constitutive TIM-3 signaling, which maintains LSC self-renewal capacity through β-catenin accumulation. In this study, we investigated the LSC-specific mechanisms of TIM-3 signaling. We found that TIM-3 signaling drove the canonical Wnt pathway, which was independent of Wnt ligands, to maintain cancer stemness in LSCs. Gal-9 ligation activated the cytoplasmic Src homology 2 (SH2) binding domain of TIM-3 to recruit hematopoietic cell kinase (HCK), a Src family kinase that is highly expressed in LSCs. HCK phosphorylated p120-catenin to promote the formation of the LDL receptor-related protein 6 (LRP6) signalosome, hijacking the canonical Wnt pathway. This TIM-3/HCK/p120-catenin axis was employed principally in immature LSCs compared to TIM-3-expressing exhausted T-cells.

Granulocyte collection by polymorphonuclear cell-targeting apheresis with medium-molecular-weight hydroxyethyl starch

Granulocyte transfusion (GTX) is a therapeutic option for patients with prolonged neutropenia suffering from severe infections. Efficient granulocyte collection by apheresis from donors requires clear separation of granulocytes from red blood cells (RBCs), and infusion of high-molecular-weight (MW) hydroxyethyl starch (HES) facilitates RBC sedimentation. Recent research has shown that apheresis with medium-MW HES may prevent adverse effects of high-MW HES on donors, but the rationale for collection with medium-MW HES has yet to be evaluated. To validate the use of medium-MW HES, we first performed experiments with whole blood samples to determine how efficiently high-, medium- and low-MW HES separated granulocytes from RBCs, and found that medium-MW HES was just as efficient as high-MW HES. We also reviewed clinical data of granulocyte apheresis at our institution to evaluate granulocyte yields. Retrospective analysis of granulocyte collection revealed that apheresis with medium-MW HES yielded sufficient granulocytes for GTX and that donor anemia reduced collection efficiency. These results collectively may help us to establish a safer method for apheresis targeting polymorphonuclear granulocytes as an alternative to high-MW HES.

Optimization of lymphapheresis for manufacturing autologous CAR-T cells

Collection of CD3+ lymphocytes via lymphapheresis is essential for manufacturing autologous chimeric antigen receptor (CAR) T cells. Optimization of timing and procedures for lymphapheresis for each patient is critical because patients often have progressive diseases and receive medications that could reduce T cell counts. We conducted a retrospective study of clinical data from 28 patients who underwent lymphapheresis for CD19-directed CAR-T therapy with tisagenlecleucel to identify factors that could affect CD3+ lymphocyte yields. The numbers of CD3+ cells in peripheral blood were significantly correlated with CD3+ cell yields (correlation coefficient r = 0.84), which enabled us to estimate the volume of blood to process before apheresis. We also found that small cell ratio (SCR) at the apheresis site precisely reflected the proportion of lymphocytes, especially in patients without circulating blasts (coefficient of determination: r² = 0.9). We were able to predict the CD3+ cell yield and prevent excessive apheresis by measuring pre-apheresis circulating CD3+ cell counts and monitoring SCR. Collectively, these results will help us to establish a strategy for optimization of lymphapheresis procedures for CAR-T cell production on a patient-by-patient basis.

Platelet decrease and efficacy of platelet-rich plasma return following peripheral blood stem cell apheresis

BACKGROUND

Peripheral blood stem cell (PBSC) transplantation is a key treatment option for hematological diseases and is widely performed in clinical practice. Platelet loss is one of the major complications of PBSC apheresis, and platelet-rich plasma (PRP) return is considered in case of platelet decrease following apheresis; however, little is known about the frequency and severity of platelet loss and the efficacy of PRP return postapheresis.

METHODS

We assessed changes in platelet counts following PBSC-related apheresis in 270 allogeneic (allo)- and 105 autologous (auto)-PBSC settings. We also evaluated the efficacy of PRP transfusion on platelet recovery postapheresis.

RESULTS

In both allo- and auto-PBSC settings, the preapheresis platelet count (range, 84-385 and 33-558 × 10⁹ /L, respectively) decreased postapheresis (range, 57-292 and 20-429 × 10⁹ /L, respectively), whereas severe platelet decrease (<50 × 10⁹ /L) was only observed in auto-PBSC patients (n = 9). We confirmed that platelet count before apheresis was a risk factor for severe platelet decrease (<50 × 10⁹ /L) following auto-PBSC apheresis (odds ratio 0.749, P < .049). PRP return postapheresis facilitated platelet recovery in more than 80% of cases in both allo and auto settings.

CONCLUSION

Lower platelet count preapheresis is a useful predictor of severe platelet decrease following auto-PBSC apheresis and PRP return is an effective process to facilitate platelet recovery postapheresis.

Recurrent Subcutaneous Sweet's Disease in a Myelofibrosis Patient Treated with Ruxolitinib before Allogeneic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (allo-SCT) has a curative potential for myelofibrosis (MF) patients; however, its association with a high therapy-related mortality (TRM) remains a big obstacle that needs to be overcome. Ruxolitinib (RUXO), a novel JAK1/2 inhibitor, can be used as a bridging therapy until allo-SCT can be performed to reduce TRM. We herein report a RUXO-treated MF patient who developed recurrent subcutaneous Sweet's disease (SSD) that was successfully treated by the administration of systemic glucocorticoids. We performed allo-SCT as previously scheduled, resulting in a good clinical course without deterioration of SSD. RUXO administration, as well as MF itself, might therefore sometimes cause this rare non-infectious event.

Evaluation of the efficacy and safety of olopatadine and fexofenadine compared with placebo in Japanese cedar pollinosis using an environmental exposure unit

BACKGROUND

Second-generation oral H1-antihistamines have become a mainstay of treatment for the symptoms of seasonal allergic rhinitis; however, the effect of olopatadine has not been widely reported to date.

OBJECTIVES

To evaluate the efficacy of 2 oral H1-antihistamines, olopatadine and fexofenadine, in the treatment of the nasal symptoms of Japanese cedar pollinosis and their possible side effects.

METHODS

This was a randomized, double-blind, placebo-controlled, crossover study conducted in an environmental exposure unit (EEU). Twenty volunteers suffering from Japanese cedar pollinosis were randomly divided into 3 groups and exposed to cedar pollen in the EEU with oral administration of olopatadine hydrochloride (5 mg), fexofenadine hydrochloride (60 mg), or placebo 1 hour prior to pollen exposure. Nasal symptoms, activity impairment, and subjective sleepiness were self-assessed during the study period. Attention was measured using the digit cancellation test. The trial was repeated after 4 and 7 weeks.

RESULTS

Compared with placebo, olopatadine significantly improved nasal symptoms and activity impairment during pollen exposure (P < .05). There was no significant relief of nasal discharge or nasal congestion with fexofenadine throughout the 5-hour exposure to cedar pollen. Furthermore, olopatadine significantly reduced nasal congestion during the first 2 hours, as well as sneezing and nasal discharge 4 hours after admission to the EEU compared with fexofenadine (P < .05). There was no significant difference in the effect on subjective sleepiness among the 3 groups, and all 3 agents had little effect on attention.

CONCLUSIONS

These findings suggest that olopatadine is more effective than placebo and fexofenadine in improving nasal symptoms of Japanese cedar pollinosis.

Topography of corticothalamic projections from the auditory cortex of the rat

Corticothalamic projections from cortical auditory field to the medial geniculate body (MG) in the rat were systematically examined by making small injections of biocytin in cortical area Te1. All injections, confined to 400 microm in diameter, resulted in two projections terminating in the ventral (MGV) and dorsal divisions (MGD) of the MG. The projections to the MGV were evidently topographic. The rostral and caudal portions of area Te1 projected to the ventromedial and dorsolateral parts of the MGV, respectively, forming narrow bands of terminal axons that extended in the mediolateral direction in the coronal plane of the MGV. The minimum dorsoventral width of the bands ranged approximately from 100 to 300 microm. Besides, the more rostral portion of area Te1 tended to project to the more rostral side of the MGV. The projections to the MGD consistently arborized in its ventral margin made up of the deep dorsal nucleus of the MGD. A similar weak topography along the rostrocaudal direction was observed in the projections to the MGD. Large terminals were occasionally found in the MGD after the injections involving cortical layer V. The distribution of large terminals also appeared topographic along with small terminals that were the major component of labeling. Collaterals of labeled axons produced slabs of terminal field in the thalamic reticular nucleus, which also exhibited a weak topography of distribution. These results provide insights into the structural basis of corticofugal modulations related to the tonotopic organizations in the cortex and MG.

Auditory thalamic nuclei projections to the temporal cortex in the rat

Thalamocortical projections from the auditory thalamic nuclei were examined systematically in the rat, including those from the dorsal division (MGD) of the medial geniculate body (MG), which were less clearly determined in previous studies. Injections of biocytin confined in each thalamic nucleus revealed characteristic features of projections in terms of cortical areas and layers of termination. In contrast to exclusively selective projections to cortical area Te1 from the ventral division (MGV) of the MG, diffuse and selective terminations were observed in the projections from the dorsal (MGD) and medial divisions (MGM) of the MG and the suprageniculate nucleus (SG). Diffuse termination was continuous in layer I or VI of the temporal cortex, while selective termination was in layers III and IV of discrete cortical areas. In addition to diffuse termination in the upper half of layer I of cortical areas Te1, Te2d and Te3v, the MGD and SG projections formed plexuses of axons selectively in lower layer III and layer IV of Te2d and Te3v. The SG projections targeted further the dorsal bank of the perirhinal cortex (PRh), while the MGD projections targeted in part the ventral fringe of Te1. The MGM projections terminated diffusely in layer VI of Te1 and Te3v, and selectively in lower layer III and layer IV of the rostral part of Te3v. Diffuse projections to layers I and VI from the SG and MGM extended in cortical regions over the dorsal fringe of Te1. Selective dense projections to middle cortical layers of Te2d and Te3v (especially its rostral part) indicate the existence of auditory areas, which could be involved in cross-modal interaction with visual and somatosensory system, respectively. Diffuse projections are supposed to bind information processings in these areas and the primary auditory area (Te1).

Month of birth, atopic disease, and atopic sensitization

BACKGROUND

Japanese cedar (Cryptmeria japonica; CJ) pollen and house dust mites are the two important aeroallergens in Japan. However, no epidemiological survey has been performed in Japan to investigate the relationship between month of birth and manifestations of allergic disease and sensitization.

OBJECTIVE

This study evaluates the correlation between month of birth and sensitization to aeroallergens or the occurrence of allergic disease on 755 Japanese school children aged 12-13 years.

METHODS

The personal history of atopic disease (bronchial asthma, allergic rhinitis, eczema, and allergic conjunctivitis) as recorded by questionnaires was investigated in relation to total serum IgE and specific IgE toward house dust mites and CJ pollen.

RESULTS

Positive specific IgE toward house dust mites was significantly less prevalent in the children born between January and March than those born during the rest of the year (p < 0.01). Positive specific IgE toward CJ pollen was significantly more prevalent in the children born between December and January than those born during the rest of the year (p < 0.05). High total IgE was less prevalent in the children born between February and April than in children born during the rest of the year (p = 0.05). The prevalence of bronchial asthma was 26.2% among children born between November and December, compared with a ratio of 17.3% among children born during the rest of the year (p < 0.05). A significantly higher proportion of the children with allergic rhinitis was born between August and October than during the rest of the year (p < 0.05). The prevalence of allergic conjunctivitis was 15.8% among the children who were born between December and January, compared with 9.1% among children born during the rest of the year (p < 0.01). No relationship between prevalence of eczema and season of birth was found.

CONCLUSION

Month of birth appears to influence the risk in the development of allergic sensitization and atopic diseases. The findings concerning higher CJ pollen sensitization in children born in the months that proceed the CJ pollen seasons are as evident as the house-dust-mite-related findings.

[Japanese cedar pollen in house dust]

Caring for oneself against Japanese cedar pollinosis is important as well as receiving medical-care. Although the importance of avoiding pollen is described in the guideline for nasal allergy medical treatment, however, there is no information for effective dust cleaning for the home. This study examined how many cedar pollens were included in indoor dust in order to obtain basic data whether dust removal for cedar pollen is available for pollinosis suffers. As a result, the study found that there were many Japanese cedar pollens in indoor dust even before the pollen season. Cedar pollen increased with the increasing number of airborne pollen. The highest number of pollen found in one week was approximately 450 pollens in a square meter of a living room floor. The study concluded that cleaning is one of the best way to remove Japanese cedar pollens found in indoor dust.

Heparin and heparan sulfate inhibit extracellular signal-regulated kinase activation and myocardial cell hypertrophy induced by endothelin-1

Heparan sulfate (HS) is one of the components of extracellular matrix and a potent anti-growth factor in various cells. Heparin has a similar structure to HS and is demonstrated to inhibit myocardial cell hypertrophy. We examined the intracellular signal mechanisms linking to the inhibitory effects of heparin and HS on endothelin-1 (ET-1)-induced hypertrophy in cultured rat neonatal myocardial cells (MCs). Heparin inhibited ET-1-induced c-fos mRNA expression. Heparin and HS inhibited ET-1-induced activation of c-fos promoter/enhancer in MCs. Although heparin and HS inhibited ET-1-induced activation of the wild-type c-fos serum response element (SRE), the activation of a mutated c-fos SRE that contains an intact binding site for the serum response factor (SRF) but lacks the ternary complex factor (TCF) binding site, was not inhibited. In addition, heparin and HS inhibited the activation of TPA response element (TRE). However, heparin did not inhibit the activation of cyclic AMP response element (CRE). Furthermore, heparin and HS inhibited ET-1-induced activation of extracellular signal-regulated kinase (ERK) and phosphorylation of Elk-1, which is one of the TCFs. These results indicate that heparin and HS inhibited ET-1-induced ERK activation, resulting in suppression of Elk-1 phosphorylation, and lead to inhibition of c-fos gene expression through SRF-independent manner. Moreover, heparin and HS inhibited ET-1-induced [3H] leucine incorporation. These results suggest that heparin and HS inhibit ET-1 induced myocardial cell hypertrophy through the inhibition of gene expression and protein synthesis.

Serotonin-induced hypercontraction through 5-hydroxytryptamine 1B receptors in atherosclerotic rabbit coronary arteries

BACKGROUND

Augmented vasoconstriction to serotonin (5-hydroxytryptamine [5-HT]) in atherosclerotic vessels plays a crucial role in the development of myocardial ischemia. We investigated mechanisms for serotonin-evoked hypercontraction in atherosclerotic rabbit coronary arteries.

METHODS AND RESULTS

Contractile responses to serotonergic agents of endothelium-denuded coronary arteries from control and Watanabe heritable hyperlipidemic rabbits (WHHL) were examined. WHHL coronary arteries exhibited hypercontraction to 5-HT(1)-receptor agonists; the constrictor threshold concentrations and E:D(50) to serotonin, 5-carboxamidotryptamine, and sumatriptan in WHHL were significantly lower, and the E:(max) in WHHL to these agents were increased 55% to 59% above those of the control. Serotonin-evoked contractions in both groups were inhibited by GR127935 (5-HT(1B/1D) antagonist; 0.1 to 1 nmol/L) and pertussis toxin but not by ketanserin (5-HT(2) antagonist; 0.01 to 1 micromol/L), suggesting that the hypercontraction is most likely mediated by 5-HT(1B/1D) receptors through a pertussis toxin-sensitive pathway. Furthermore, simultaneous measurements of [Ca(2+)](i) and isometric tension of fura-2-loaded arteries revealed that the hypercontraction was concomitant with the augmented elevation of [Ca(2+)](i) in the smooth muscle. The 5-HT(1B) mRNA levels in WHHL coronary arteries increased to 2.5-fold over those in control arteries, whereas neither 5-HT(1D) nor 5-HT(2A) mRNA was detected in either group.

CONCLUSIONS

Atherosclerotic rabbit coronary arteries exhibited the enhancement in contraction and Ca(2+) mobilization in response to serotonin. The 5-HT(1B) receptor, which is upregulated by atherosclerosis, most likely mediates the augmenting effects of serotonin.

[An office technique for myringoplasty without the use of fibrin glue]

A simple method for office closure of eardrum perforation using an atero-collagen graft used for dermal defects (Terdermis) without fibrin glue was developed. Eardrum perforations were successfully closed in 71.4% of all cases (63 ears) after the initial treatment. Neither skin incision nor the use of temporal fascial grafts was necessary in this method. The merit of the method is that there is no possibility of blood infection because no blood materials are used.

Requirement of activation of the extracellular signal-regulated kinase cascade in myocardial cell hypertrophy

The signal transduction mechanisms mediating hypertrophic responses in myocardial cells (MCs) remain uncertain. We investigated the role of the extracellular signal-regulated kinase (ERK) cascade in myocardial cell hypertrophy by the strategy of using the adenovirus-mediated overexpression of mitogen-activated protein kinase (MAPK)/ERK kinase (MEK), which is the upstream activator of ERK. We generated recombinant adenoviruses expressing constitutively active MEK1 (MEK1 EE) and dominant negative MEK1 (MEK1 DN). Overexpression of MEK1 EE in MCs activated ERK1/2 and subsequently induced atrial natriuretic peptide (ANP) mRNA expression. In addition, MEK1 EE overexpression resulted in an increase in cell size and sarcomeric reorganization. In contrast, overexpression of MEK1 DN in MCs inhibited endothelin-1 (ET-1)-, phenylephrine (PE)-, leukemia inhibitory factor (LIF)-, isoproterenol (ISP)-, and mechanical stretch-induced ERK activation and ANP mRNA expression. MEK1 DN overexpression inhibited ET-1-, PE-, LIF-, and ISP-induced increases in cell size and sarcomeric reorganization. Consistent with the observed effects on cellular morphology, overexpression of MEK1 EE resulted in an increase in amino acid incorporation, while overexpression of MEK1 DN inhibited ET-1-, PE-, LIF-, ISP-, and mechanical stretch-induced increases in amino acid incorporation. These results indicate that the ERK cascade plays an important role in the signaling pathway leading to the development of myocardial cell hypertrophy.

[The positivity rate of specific IgE antibody to Japanese cedar pollen in Wakayama Prefecture]

The incidence of Japanese cedar pollinosis has been increasing each year in Japan. Japanese cedar pollinosis is a state of allergic response, mediated by IgE. So, it is important to know the state of sensitization against Japanese cedar pollen. The subjects were 1321 nonselective cases who were more than 16 years of age and who live in Wakayama Prefecture. Specific IgE antibodies to Japanese cedar pollen were measured by Lumiward immunoassay system. The results showed that positivity for sera class 2 or higher was 30.9%. Furthermore, the positivity in 1995 was higher than the positivity in either 1985 (13.9%) or 1990 (18.3%). The incidence of specific IgE antibody positivity was higher in males. Also the age distribution of the positivity was highest in the 20-29 years old group, and the positivity was decreased with age. We examined the kinds of factors influencing the positivity of specific IgE antibodies. However, the relation between the positivity of specific IgE antibodies and the various environmental factors was unclear.

A high-titer lentiviral production system mediates efficient transduction of differentiated cells including beating cardiac myocytes

Human immunodeficiency virus (HIV, lentivirus) type-1 based vectors have a number of attractive features for gene therapy, including the ability to transduce non-dividing cells and long term transgene expression. We used a three-plasmid expression system to generate pseudotyped lentivirus-based vectors by transient transfection of human embryonic kidney 293T cells in the presence of sodium butyrate, which is known to activate the long terminal repeat-directed expression of HIV. Using this system we successfully generated versatile high titer lentivirus at titers of up to 2 x 10(8) transducing units/ml (TU/ml), and improved transduction efficiency in various cell types from seven to over twenty fold. We demonstrate its applicability of these vectors for the efficient transduction of non-dividing cells, including post mitotic beating rat cardiac myocytes and well-differentiated rat L6 myofibers. While both lentivirus-based and murine retrovirus-based vectors effectively transduced dividing cardiac fibroblasts and L6 muscle myoblasts in culture, lentivirus-based vectors also efficiently transduced cardiac myocytes and yielded titers of (6.3 +/- 1.2) x 10(5) TU/ml; however murine retrovirus-based vectors showed low transduction efficiency with titers reaching only (8.9 +/- 2.1) x 10(2) TU/ml. Furthermore, even 12 days after induction of differentiation of L6 myofibers, lentivirus-mediated transduction of beta-galactosidase (beta-Gal) at approximately 30-40% of the maximum expression levels achieved in replicating myoblasts. In contrast, the expression of beta-Gal following transduction of the myofibers by murine retrovirus-based vectors fell to less than 1% of an already reduced level of transduction in undifferentiated confluent myoblasts. These results demonstrate that lentivirus-based vectors can efficiently transduce both well-differentiated cardiac myocytes and differentiated myofibers. This appears to be an efficient method and provides a new tool for research and therapy for cardiovascular diseases.

Endothelin-1 activates p38 mitogen-activated protein kinase via endothelin-A receptor in rat myocardial cells

In myocardial cells (MCs), endothelin-1 (ET-1) exerts various effects such as hypertrophy, and causes cellular injury. Long-term treatment with an endothelin-A (ET(A)) receptor antagonist improves the survival of rats with heart failure, suggesting that myocardial endothelin system contributes to the progression of heart failure. p38 mitogen-activated kinase (MAPK) is a member of the MAPK family and activated by several forms of environmental stresses. We show here the effect of ET-1 on p38 MAPK activation and the role of ET-1-activated p38 MAPK on morphological changes in MCs. ET-1-stimulated p38 MAPK phosphorylation was detectable within 2 min and maximal at 5 min and was concentration dependent. The maximum effect was obtained at 10 nM. An ET(A) receptor antagonist, BQ-123, but not an endothelin-B receptor antagonist, BQ-788, inhibited these reactions. A p38 MAPK inhibitor, SB203580, failed to inhibit the morphological changes associated with ET-1-induced myocardial cell hypertrophy. These results indicate that p38 MAPK is activated by ET-1 but does not contribute to the development of ET-1-induced myocardial cell hypertrophy.

[Environmental control for allergic diseases--avoiding and killing effect on housedust-mite by eastern red cedar]

Housedust-mite has been a trigger factor for allergic diseases such as asthma, rhinitis and eczema. Therefore, it is important to remove housedust-mite from the environment of an allergic patient. Eastern red cedar is one kind of cypress tree which grows naturally in Northern America. It is used for the material of pencils, and the essence of soap. Its oil is used for oily substance for microscope lens. Using original system, we examined eastern red cedar and its oil, and found that it is effective for killing and preventing housedust-mites. The result was very effective. In conclusion the eastern red cedar and its oil seems to be useful for controlling mites in the home environment of allergic patients.

Identification of mRNA for 5-HT1 and 5-HT2 receptor subtypes in human coronary arteries

OBJECTIVE

Although pharmacological studies have indicated that serotonin (5-HT)-evoked contraction of the human coronary artery is mediated by 5-HT1-like and 5-HT2 receptors, the gene expression of 5-HT receptors is still unclear. We examined mRNA expression of 5-HT1 and 5-HT2 receptor subtypes in human coronary arteries.

METHODS

Total RNA was extracted from human coronary arteries of 14 patients at autopsy by the guanidine method. Reverse transcription-polymerase chain reaction (RT-PCR) and ribonuclease protection assays were performed to identify 5-HT1 and 5-HT2 receptor mRNA expression in human coronary artery.

RESULTS

By RT-PCR, 5-HT1b, 5-HT2A and 5-HT2B mRNAs were detected in all of the 14 patients. 5-HT1A, 5-HT1D, and 5-HT1E mRNAs were detected in only some patients. However, neither 5-HT1F mRNA nor 5-HT2C mRNA was detected in any patient. By ribonuclease protection assay, 5-HT1B and 5-HT2A signals were detected in all patients examined, but neither 5-HT1A, 5-HT1D nor 5-HT2B signal was detected in any patient.

CONCLUSIONS

Of 5-HT1/2 receptor subtypes, 5-HT1B and 5-HT2A receptor mRNAs were predominantly expressed in human coronary arteries. Our finding provides molecular evidence that the 5-HT1B receptor may be the 5-HT1-like receptor which mediates constriction of human coronary arteries.

Hypotension and reduced nitric oxide-elicited vasorelaxation in transgenic mice overexpressing endothelial nitric oxide synthase

Nitric oxide (NO), constitutively produced by endothelial nitric oxide synthase (eNOS), plays a major role in the regulation of blood pressure and vascular tone. We generated transgenic mice overexpressing bovine eNOS in the vascular wall using murine preproendothelin-1 promoter. In transgenic lineages with three to eight transgene copies, bovine eNOS-specific mRNA, protein expression in the particulate fractions, and calcium-dependent NOS activity were confirmed by RNase protection assay, immunoblotting, and L-arginine/citrulline conversion. Immunohistochemical studies revealed that eNOS protein was predominantly localized in the endothelial cells of aorta, heart, and lung. Blood pressure was significantly lower in eNOS-overexpressing mice than in control littermates. In the transgenic aorta, basal NO release (estimated by Nomega-nitro-L-arginine-induced facilitation of the contraction by prostaglandin F2alpha) and basal cGMP levels (measured by enzyme immunoassay) were significantly increased. In contrast, relaxations of transgenic aorta in response to acetylcholine and sodium nitroprusside were significantly attenuated, and the reduced vascular reactivity was associated with reduced response of cGMP elevation to these agents as compared with control aortas. Thus, our novel mouse model of chronic eNOS overexpression demonstrates that, in addition to the essential role of eNOS in blood pressure regulation, tonic NO release by eNOS in the endothelium induces the reduced vascular reactivity to NO-mediated vasodilators, providing several insights into the pathogenesis of nitrate tolerance.

[Epidemiologic study of Chlamydia pneumoniae with ELISA]

Chlamydia Pneumoniae (C. pneumoniae) is a bacterium involved in infections of the upper airway as well as in lower respiratory diseases. It has been reported that infections from this bacterium are prevalent worldwide and that the proportion of the population having the antibody is high. It is, however, difficult to identify the pathogen by routine bacterial examination because it is an obligate cytozoic bacterium. In addition, the examination has been feasible in only a limited number of laboratories because the determination of the serum antibody titer has required preparation of the antigen as well as sophisticated skill. We conducted an epidemiological survey of 320 healthy males and females in their 20s living in the three cities of Osaka, Kobe and Oita using "HITAZYME C. Pneumoniae", which is a recently developed kit for determination of anti-C. pneumoniae specific antibody. The statistical method used was the chi square test for the comparison of proportions. Mean proportion of the population showing positive antibody test was 58.1%. IgA antibody was positive in 42.8% and IgG in 46.5% of the above population. There were no statistically significant differences between districts of between genders in the percentages of cases positive for these antibodies. The results were comparable to those previously reported suggesting that C. pneumoniae is prevalent all over Japan. This kit was found to be an easy way to use the ELISA method and therefore to be clinically useful.

Transforming growth factor-beta1 and protein kinase C synergistically activate the c-fos serum response element in myocardial cells

We previously reported that transforming growth factor-beta1 (TGF-beta1) potentiated alpha1-adrenergic and stretch-induced c-fos mRNA expression and norepinephrine (NE)-induced amino acid incorporation in rat cultured myocardial cells (MCs). In the present study, we attempted to explore the mode of TGF-beta1 action for c-fos gene expression in MCs. In the transient transfection assay, TGF-beta1 potentiated NE- or 12-O-tetradecanoylphorbol-13-acetate (TPA)-activated c-fos promoter/enhancer, but not forskolin-activated c-fos promoter/enhancer. The c-fos serum response element (SRE) and the TPA response element (TRE) were responsible for TGF-beta1-induced potentiation of the NE or TPA action. Although TGF-beta1 activated not only the wild-type c-fos SRE, but also the mutated c-fos SRE, which contains an intact binding site for the serum response factor (SRF) but lacks the ternary complex factor (TCF) binding site, TPA activated the wild-type c-fos SRE but not the mutated c-fos SRE. TGF-beta1 did not potentiate the effects of TPA on the activation of mitogen-activated protein kinase (MAPK) and the phosphorylation of Elk-1 and SAP-1a, which belong to TCF at the c-fos SRE. These results indicate that TGF-betaf potentiates the c-fos SRE activated by PKC through the SRF binding site. TGF-beta1 is involved in the regulation of c-fos gene expression through the c-fos SRE and is subsequently involved in the regulation of the gene which has the TRE in the promoter/enhancer region.

5-HT1Dbeta receptor mediates the supersensitivity of isolated coronary artery to serotonin in variant angina

Although serotonin (5-hydroxytryptamine; 5-HT) is used for provocation of coronary spasm, 5-HT receptor subtypes in spastic coronary arteries remain undetermined. We demonstrated the supersensitivity of isolated coronary artery to ergonovine, 5-HT, and sumatriptan, a 5-HT1D receptor agonist, in a patient with variant angina. Furthermore, we detected gene expression of 5-HT1Dbeta and 5-HT2A receptors in spastic coronary artery using RNase protection assay. These findings suggest that the leftward shift of the dose-response curve for 5-HT, which plays an important role in the pathogenesis of coronary spasm, is mediated by activation of 5-HT1Dbeta receptor.

[Cochlear implantation in a child with a "common cavity" cochlear malformation]

A nucleus multichannel 22-electrode cochlear prosthesis was successfully implanted into a 4-year-old girl with a cochlear "common cavity" deformity. Preoperative radiologic studies showed bilateral common cavity cochlear malformations but no narrow internal auditory canal. Because left common cavity was larger than the right common cavity, the patient underwent a left cochlear implant. The facial nerve was found on the promontrium and interfered with accessing the hypoplastic round window. The cochlear cavity was entered through the hypoplastic semicircular canal to prevent facial nerve injury. In the postoperative rehabilitation phase, the child was able to distinguish phonemes, and word identification had started.

Activated RhoA stimulates c-fos gene expression in myocardial cells

Rho regulates various cell functions, including cell morphology and motility. However, the functional role of Rho on the signaling pathway in myocardial cells (MCs) is unknown. In the present study, we attempted to explore the mode of Rho action for c-fos gene expression in MCs. Expression of the c-fos promoter/enhancer linked to the luciferase reporter gene (c-fos luciferase) was stimulated by the wild type of RhoA and the point-mutated active form of RhoA (RhoA Val14) but not the biologically inactive effector domain mutant of RhoA. Rho GDP dissociation inhibitor inhibited the action of RhoA on c-fos luciferase expression. The deletion analysis revealed that the c-fos serum response element (SRE) and the 12-O-tetradecanoylphorbol-13-acetate response element (TRE) mainly account for c-fos luciferase expression by RhoA Val14. The c-fos SRE mutant, which contains an intact binding site for the serum response factor but lacks the ternary complex factor binding site, was activated by RhoA Val14. The action of RhoA Val14 on c-fos luciferase expression was not inhibited by downregulation of protein kinase C, protein kinase C inhibitors, or tyrosine kinase inhibitors. These results indicate that activated RhoA stimulates c-fos gene expression through the c-fos SRE and TRE and that the signaling pathway from activated RhoA to the c-fos promoter/enhancer is independent of these inhibitor-sensitive pathways in MCs.

Ex vivo study of the effects of dietary magnesium deficiency on the formation and release of NO from endothelial cells and the sensitivity to NO of smooth muscle cells of thoracic aortas isolated from rats

We found that the contractile responses to phenylephrine (PE) of isolated endothelium-intact thoracic aortas were enhanced by a nitric oxide (NO) synthase inhibitor, nitro-L-arginine (LNAG). and the magnitude of this enhancement was significantly greater in Mg-deficient than control rats. In this study, we used a sandwich method to evaluate the effects of dietary Mg deficiency on the ability of vascular endothelial cells to form and/or release NO and on the sensitivity to NO of vascular smooth muscle cells. Male Wistar rats were fed a Mg-deficient (10 mg Mg/kg diet) or control (700 mg Mg/kg diet) diet for 30 days. With the sandwich method, when endothelium-denuded thoracic aortas from chow fed rats were used as the assay vessels, and endothelium-intact aortas from control or Mg-deficient rats were used as the NO-donor vessels, neither the aortic contractile responses to PE nor the enhancement by LNAG of these responses in control and Mg-deficient rats differed significantly. When endothelium-denuded thoracic aortas from control or Mg deficient rats were used as the assay vessels and endothelium-intact aortas from chow fed rats were used as NO-donor vessels, LNAG enhanced PE-induced contractions to a significantly greater extent in Mg-deficient than control rats. Furthermore, sodium nitroprusside (a NO donor) had a greater relaxant effect on endothelium-denuded thoracic aortas isolated from Mg-deficient than control rats. These ex vivo results suggest that dietary Mg deficiency in rats has little effect on the formation and/or release of NO by aortic endothelial cells. but it does appear to increase the sensitivity to NO of aortic smooth muscle cells.

Myristoylation of endothelial cell nitric oxide synthase is important for extracellular release of nitric oxide

Endothelial cell nitric oxide synthase (NOS) is known to have a N-myristoylation consensus sequence. Such a consensus sequence is not evident in the macrophage, smooth muscle and neuronal NOS. A functional role for this N-terminal myristoylation is not clear yet. In the present study, we examined the effect of N-terminal myristoylation on the NOS activity determined by the conversion of L-[3H]arginine to L-[3H]citrulline and extracellular NO release determined by nitrite production in the conditioned medium from the COS-7 cells transfected with wild-type bovine aortic endothelial cell (BAEC) NOS cDNA or non-myristoylated BAEC-NOS mutant cDNA. NOS activity of wild type BAEC-NOS in COS-7 cells was localized in the particulate fraction and that of mutant NOS was in the cytosolic fraction. In contrast, nitrite production from COS-7 cells transfected with wild type BAEC-NOS cDNA was greater than that of mutant cDNA in a time dependent and a concentration dependent manner. These results suggest that membrane localization of NOS with myristoylation facilitates extracellular transport of NO and leads to enhanced NO signaling on the vascular smooth muscle cells and the intravascular blood cells including neutrophils, macrophages and platelets.

Low concentration of oxidized low-density lipoprotein and lysophosphatidylcholine upregulate constitutive nitric oxide synthase mRNA expression in bovine aortic endothelial cells

Endothelium-dependent relaxation is markedly reduced in atherosclerotic arteries. Recently, the endothelium-dependent relaxing factor has been identified as nitric oxide (NO). We used RNase protection assay and immunoblotting to elucidate the effect of atherogenic lipoprotein on the expression of constitutive NO synthase (cNOS) mRNA and protein levels in bovine aortic endothelial cells. Twenty-four-hour exposure to a low concentration of oxidized low-density lipoprotein (10 micrograms protein/mL) upregulated cNOS mRNA levels (2.4 +/- 0.4-fold, P < .01). However, native low-density lipoprotein and high-density lipoprotein did not have any effect on cNOS mRNA levels. Furthermore, 5 micrograms/mL of lysophosphatidylcholine (LPC) also upregulated cNOS mRNA levels (2.6 +/- 0.5-fold, P < .01) at 8 hours. This action of LPC was abolished with cycloheximide but not with staurosporine. We concluded that atherogenic lipoproteins upregulate cNOS mRNA and protein levels in bovine aortic endothelial cells. This observation supports the hypothesis that an impairment of endothelium-dependent vasodilatation in atherosclerotic vessels may not be due to a decrease in cNOS expression. Moreover, the LPC action on cNOS mRNA levels requires new protein synthesis.

Inhibition of endothelial nitric oxide synthase activity by protein kinase C

Nitric oxide (NO) is an important molecular messenger accounting for endothelium-derived relaxing factor. Recently, NO synthase (NOS) from cultured endothelial cells has been purified and molecularly cloned. To evaluate the effect of phosphorylation by protein kinase C (PKC) and cyclic AMP-dependent protein kinase (PKA) on endothelial constitutive NOS catalytic activity, we incubated purified endothelial NOS with PKC or PKA. Endothelial NOS was stoichiometrically phosphorylated by PKC and PKA. In intact bovine aortic endothelial cells (BAECs), NOS was phosphorylated by stimulation with 12-O-tetradecanoylphorbol-13-acetate (TPA). NOS activity measured by the conversion of [3H]arginine to [3H]citrulline in homogenates of BAECs treated with TPA or phorbol 12,13-dibutyrate was reduced by 30%, whereas dibutylyl cyclic AMP did not affect NOS activity. Moreover, we measured NO release from cultured BAECs by a chemiluminescence method to examine the effect of PKC and PKA on endothelial NOS activity. In cultured BAECs, ATP gamma S and A23187 induced NO release in time- and dose-dependent manners. Phorbol esters such as TPA and phorbol 12,13-dibutyrate dose dependently inhibited NO release stimulated by A23187 as well as ATP gamma S. Reduction of NO release by TPA was almost completely prevented by pretreatment with staurosporine, an inhibitor of PKC. NO release by A23187 was increased in PKC-downregulated BAECs. In contrast, dibutylyl cyclic AMP or 8-bromo cyclic GMP had no effect on NO release from BAECs induced by A23187 or ATP gamma S. These results indicate that phosphorylation of NOS by PKC is associated with a reduction of its catalytic activity in vascular endothelial cells.

Mechanical response to photolytic ATP pulses of skinned muscle fibres pre-activated with a small pulse of ATP

(1) Skinned fibres from rat psoas muscle were placed in oil and activated at 10 degrees C by pulse photolysis of caged ATP. From the force and stiffness transients on small ATP pulses, we estimated the concentration and rate of ATP hydrolysis of the crossbridges in the fibres. They were 0.14 mM and 0.16 mMs-1, respectively, and thus the turnover rate was 1.1 s-1. (2) To examine the mechanical properties of the physiological ADP-bound crossbridges, we took a double-pulse protocol: the skinned fibre was first activated with a conditioning ATP pulse (0.2-0.5 mM). Several (3-5) seconds later, when almost all the ATP should have been hydrolysed into ADP+P(i), we applied another ATP pulse (0.2-1 mM) to test the fibre. (3) An analysis of the transients on the test pulses indicated that the conditioning pulse slowed the rate of crossbridge detachment. The time course of force development was thus expected to be also delayed, but was not. (4) We suggested that the rigor crossbridge might differ from the nucleotide-free intermediate in the physiological reaction cycle.

Rabphilin-3A, a putative target protein for smg p25A/rab3A p25 small GTP-binding protein related to synaptotagmin

In a previous study (H. Shirataki, K. Kaibuchi, T. Yamaguchi, K. Wada, H. Horiuchi, and Y. Takai, J. Biol. Chem. 267:10946-10949, 1992), we highly purified from bovine brain crude membranes the putative target protein for smg p25A/rab3A p25, a ras p21-related small GTP-binding protein implicated in neurotransmitter release. In this study, we have isolated and sequenced the cDNA of this protein from a bovine brain cDNA library. The cDNA had an open reading frame encoding a protein of 704 amino acids with a calculated M(r) of 77,976. We tentatively refer to this protein as rabphilin-3A. Structural analysis of rabphilin-3A revealed the existence of two copies of an internal repeat that were homologous to the C2 domain of protein kinase C as described for synaptotagmin, which is known to be localized in the membrane of the synaptic vesicle and to bind to membrane phospholipid in a Ca(2+)-dependent manner. The isolated cDNA was expressed in COS7 cells, and the encoded protein was recognized with an anti-rabphilin-3A polyclonal antibody and was identical in size with rabphilin-3A purified from bovine brain by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Moreover, both rabphilin-3A purified from bovine brain and recombinant rabphilin-3A made a complex with the GTP gamma S-bound form of rab3A p25 but not with the GDP-bound form of rab3A p25. Immunoblot and Northern (RNA) blot analyses showed that rabphilin-3A was highly expressed in bovine and rat brains. These results indicate that rabphilin-3A is a novel protein that has C2 domains and selectively interacts with the GTP-bound form of rab3A p25.

67Ga citrate and 99mTc(v)-DMSA scintigraphy in a case of maxillary sinus liposarcoma

Scintigraphic images with 67Ga citrate and 99mTc(v)-dimercaptosuccinic acid and MR image of a 16-year-old male with maxillary sinus liposarcoma (predominantly myxoid type) are reported. The MR image clearly indicated the exact location, size and anatomical relationship of the tumor. Scintigraphic evaluation was useful in suggesting the malignant nature of the tumor and showed no distant metastasis. Both examinations were effective in treating this case.

Time course of rise of muscle stiffness at onset of contraction induced by photorelease of ATP

Isometric contraction (9-10 degrees C) of skinned fibres from rat psoas muscle was elicited by photorelease of ATP (1.3-1.4 mM), and force (F), in-phase (I) and quadrature (Q) stiffness were monitored. The sinusoidal length change for the stiffness measurement was approximately 0.09% fibre length and 200-1000 Hz. On photolysis, F and I initially fell, and then rose. The half-time of the rise of I was shorter than that of F. Contrary to the previous assumption, Q rose even earlier than I. Although the time courses of the rise of F and I were greatly affected by the presence of phosphate ion (Pi; 4 mM), its effect on Q was modest. We propose the following hypothesis: the rigor crossbridges, after binding ATP, initially enter a state characterized by high Q with low I and none or little F, and then, releasing Pi during passing the state with the increased I, reach the final force generating state.

smg/rap1/Krev-1 p21s inhibit the signal pathway to the c-fos promoter/enhancer from c-Ki-ras p21 but not from c-raf-1 kinase in NIH3T3 cells

smg/rap1A/Krev-1 p21 cDNA is known to inhibit v-Ki-ras p21-induced cell transformation in NIH3T3 cells, but the inhibitory mechanism is not clear at present. In the present study, we examined the effect of smg p21s on the c-fos promoter/enhancer linked to the luciferase reporter gene (c-fos-luciferase). After transfection of c-fos-luciferase into NIH3T3 cells constitutively expressing c-Ki-ras(val-12) p21 or activated c-raf-1 kinase, expression of c-fos-luciferase was much higher than after transfection into control NIH3T3 cells. Addition of platelet-derived growth factor (PDGF), 12-O-tetradecanoyl phorbol 13-acetate (TPA) or dibutyryl cyclic AMP (Bt2cAMP) to the control NIH3T3 cells stimulated c-fos-luciferase expression. Transfection of the smg p21 cDNAs inhibited the activated ras p21-, PDGF- or TPA-stimulated c-fos-luciferase expression, but did not inhibit the activated c-raf-1 kinase- or Bt2cAMP-stimulated reaction. These results indicate that smg p21s inhibit the signal pathways from the PDGF receptor, protein kinase C, and ras p21s to the c-fos promoter/enhancer, but not those from c-raf-1 kinase and cyclic AMP-dependent protein kinase to the c-fos promoter/enhancer.

The functional domain of the stimulatory GDP/GTP exchange protein (smg GDS) which interacts with the C-terminal geranylgeranylated region of rap1/Krev-1/smg p21

rap1/Krev-1/smg p21 (smg p21), a member of the small GTP-binding protein (G protein) superfamily, has a geranylgeranylated cysteine residue and clustered basic amino acids in the C-terminal region. The GDP/GTP exchange reaction of smg p21 is regulated by smg GDS, which is also active on Ki-ras p21 and rho p21. The C-terminal region of smg p21 is essential for its interaction with smg GDS. Moreover, smg p21 is phosphorylated by cyclic AMP- and cyclic GMP-dependent protein kinases at the serine residue between the polybasic region and the prenylated cysteine residue, and this phosphorylation initiates the smg GDS-induced smg p21 activation. Thus, the C-terminal cationic and hydrophobic region is important for the regulation of the smg p21 activity. In the present study, we attempted to determine the functional domain of smg GDS which interacts with the C-terminal region of smg p21 by use of a cross-link method and a site-directed mutagenesis method. The region of smg GDS cross-linked with the C-terminal region of smg p21B was residues 444-492, which is located at the C-terminal fifth of smg GDS. On deletion of these residues, smg GDS became inactive on smg p21B, Ki-ras p21 and rhoA p21. These results indicate that residues 444-492 of smg GDS are at least one of the domains which interact with the C-terminal region of its substrate small G proteins.

Effects of ethylene glycol and calcium on the kinetics of contraction induced by photo-release of low concentrations of ATP in rat psoas muscle fibres

To induce isometric contraction in the absence of Ca2+ (10 mM EGTA), low concentrations (130 microM) of ATP were photoreleased from caged ATP in skinned fibres from rat psoas muscle at 15-16 degrees C. The magnitude of contraction was independent of the concentration of EGTA (1-30 mM). Each isometric transient (i) was paired with another (s) obtained under the same conditions but with 0.4% muscle stretch to elevate the rigor force before photolysis. The algebraic difference (d) between i and s was assumed to represent detachment of the crossbridges. The time course of force development (f) by the reattached crossbridges could be estimated by subtracting an appropriately scaled d from i (or s). Ethylene glycol (20% in solvent) reduced the magnitude and the rate of rise of f, although it scarcely affected d, suggesting that ethylene glycol inhibited reattachment of the crossbridges but not their detachment. The presence of Ca2+ (50 microM) increased the magnitude of f, but did not affect its time course (130 microM ATP). Detachment, d, was not influenced by Ca2+ in terms of both extent and rate. The effect of Ca2+ in the presence of ethylene glycol was indistinguishable from that in its absence. Ethylene glycol did not seem to substantially affect the extent of Ca-regulation on the contractile activity.

Effects of ethylene glycol on the kinetics of contraction on flash photolysis of caged ATP in rat psoas muscle fibres

ATP (1-1.2 mM) was photoreleased from caged ATP (5 mM) in skinned fibres from rat psoas muscle at 15-17 degrees C, to examine the effects of ethylene glycol (EG; 20% in solvent) on the kinetics of isometric contraction. Muscle fibres were stretched by 0.5-2% before photolysis, so that force just before photolysis was almost equal to the steady-state force after photolysis. At the phase of steady-state contraction, force and 500 Hz-stiffness in the presence of EG were 50% and 70% of the controls, respectively, resulting in a higher stiffness-to-force with EG, as reported previously. Following photolysis, force fell before rising to a steady-state plateau. The estimated rate constant of the force decay was approximately 90 s-1, and in the presence of EG was 80-85% of the control. This suggested a small effect of EG on the crossbridge detachment induced by ATP. The rate of force redevelopment was approximately 70 s-1, and EG decreased this rate to 50% of the control. This suggested that EG greatly slows the transition of the crossbridges from the detached state to the reattached force-producing state. The time course of the stiffness signals was consistent with this interpretation. The high stiffness-to-force ratio with EG indicated that EG not only reduces the rate constants which were directly examined in this study but also modifies other aspects of the crossbridge reaction.

Molecular cloning of the human cDNA for a stimulatory GDP/GTP exchange protein for c-Ki-ras p21 and smg p21

We have previously purified smg GDP dissociation stimulator (GDS) from bovine brain and isolated its cDNA from a bovine brain cDNA library. smg GDS stimulates the GDP/GTP exchange reaction of a group of small GTP-binding proteins (G proteins), including at least c-Ki-ras p21, smg p21A, smg p21B, rhoA p21 and rhoB p21, by stimulating the dissociation of GDP from and the subsequent binding of GTP to each small G protein. In this study, we have isolated and sequenced the cDNA of smg GDS from a human brain cDNA library using the cloned bovine smg GDS cDNA. The cDNA has an open reading frame encoding a protein of 558 amino acids with a calculated Mr value of 61,122. Human smg GDS shares 93% nucleotide and 96% amino acid sequence homologies with bovine smg GDS. The isolated cDNA is expressed in Escherichia coli, and the encoded protein shows the physical and functional properties similar to those of bovine smg GDS.

Transforming and c-fos promoter/enhancer-stimulating activities of a stimulatory GDP/GTP exchange protein for small GTP-binding proteins

smg GDP dissociation stimulator (GDS) is a stimulatory GDP/GTP exchange protein for a group of ras p21-like small GTP-binding proteins (G proteins) including c-Ki-ras p21, smg p21A, smg p21B, and rhoA p21. smg GDS converts the GDP-bound inactive form to the GTP-bound active form of each small G protein by stimulating their GDP/GTP exchange reaction in a cell-free system. The point-mutated c-Ki-ras p21 (c-Ki-rasval12 p21) is known to strongly transform NIH/3T3 cells and to markedly stimulate the c-fos promoter/enhancer in this cell line, whereas the normal c-Ki-ras p21 is weak in these activities. In the present study, we examined the effect of smg GDS on these activities to explore its physiological function. Overexpression of both smg GDS and c-Ki-ras p21 strongly transformed NIH/3T3 cells, whereas overexpression of either smg GDS or c-Ki-ras p21 alone weakly transformed the cells. Furthermore, overexpression of both smg GDS and c-Ki-ras p21 markedly stimulated the c-fos promoter/enhancer in NIH/3T3 cells, whereas overexpression of either smg GDS or c-Ki-ras p21 alone weakly stimulated it. These results indicate that smg GDS transforms NIH/3T3 cells and stimulates the c-fos promoter/enhancer in this cell line in cooperation with c-Ki-ras p21.

A stimulatory GDP/GTP exchange protein for smg p21 is active on the post-translationally processed form of c-Ki-ras p21 and rhoA p21

We have purified a stimulatory GDP/GTP exchange protein for smg p21A and -B, ras p21-like small GTP-binding proteins (G proteins), cloned its cDNA, and named it GDP dissociation stimulator (smg p21 GDS). We show here that smg p21 GDS is active not only on smg p21A and -B but also on c-Ki-ras p21 and rhoA p21, all of which are post-translationally processed. Furthermore, we show that smg p21 GDS is inactive on the post-translationally unprocessed form of these proteins and on the post-translationally unprocessed form of c-Ha-ras p21 and smg p25A. All of the small G proteins recognized by smg p21 GDS have a cDNA-predicted C-terminal "CAAX" motif (where C is cysteine, A is an aliphatic amino acid, and X is any amino acid) and a polybasic region upstream of this motif. These results suggest that smg p21 GDS is at least active on a group of small G proteins having these unique C-terminal structures. Moreover, they suggest that the C-terminal post-translational processing of these small G proteins, by farnesylation or geranylgeranylation of the C-terminal cysteine residue, removal of amino acids in positions denoted "AAX", and carboxyl methylation of the exposed cysteine residue, is important for the smg p21 GDS action.