Biomedical subjects

T Imamura

Publications and source records attributed to T Imamura.

At least 145 records · Page 8Linked to original sources

PubMed1999

Anomalous cadherin expression in osteosarcoma. Possible relationships to metastasis and morphogenesis.

Two isoforms of the human cadherin-11/OB-cadherin gene, the intact and the variant forms, had been isolated from an osteosarcoma cDNA library. The intact form has a typical cadherin structure, whereas the variant form, generated by alternative splicing, encodes a cytoplasmic domain that is completely different from that of the intact form and lacks a homophilic cell-cell adhesion ability. At the protein level, the secreted form generated from the intact cadherin-11 is present. We examined the expression of the intact and the variant forms of cadherin-11 in 23 primary and metastatic osteosarcomas from 22 patients by reverse transcriptase-polymerase chain reaction (RT-PCR) analyses, revealing that all 23 tumors in the patients expressed the variant form and three of them expressed it prominently. On the other hand, Western blot analyses of six tumors showed that the secreted form was strongly expressed, and furthermore, expression of N-cadherin was extremely low. Overexpression of the intact cadherin-11 cDNA in osteosarcoma cell lines demonstrated that the secreted form is derived from the intact form of cadherin-11 in osteosarcoma. Immunohistochemically, cadherin-11, N-cadherin, and beta-catenin were expressed at the cell surface of fetal osteoblasts, whereas in osteosarcoma cells, they were expressed only focally or weakly in the cytoplasm. Considering the function of cadherin in carcinomas, it is suggested that the anomalous expression of human cadherin-11 in osteosarcoma and the reduced expression of N-cadherin play a role in metastasis and the irregular morphology in the highly malignant mesenchymal tumor.

Bone Development↗

PubMed1999

Hyperthermic isolated regional perfusion for the treatment of osteosarcoma in the lower extremity.

BACKGROUND: In order to reduce the systemic toxity of cisplatin and to increase the effect on the local tumor, facilitating limb-preserving procedures, we have been using hyperthermic isolated regional perfusion (HIRP) for the treatment of osteosarcoma in addition to preoperative chemotherapy. MATERIALS AND METHODS: Twenty patients with an osteosarcoma in a lower extremity were treated with both preoperative chemotherapy and HIRP. RESULTS: The chemotherapeutic effects of preoperative chemotherapy with HIRP was grade III in 6, and grade IV (no viable cell areas observed) in 7. The surgical margins could be reduced in these 13 cases of good responders showing over 90% necrosis (grade III or grade IV), which mainly involved postnecrotic fibrosis and osteosclerosis. CONCLUSION: HIRP can help to control the tumor locally. A more conservative operation was then possible in cases of good responders to preoperative chemotherapy with HIRP.

Adolescent↗

PubMed1999

An autocrine or a paracrine role of adrenomedullin in modulating cardiac fibroblast growth.

OBJECTIVE: The aim of the present study was to determine the role of adrenomedullin (AM) in cardiac fibroblasts. METHODS: The production and secretion of AM were examined in cultured neonatal rat cardiac fibroblasts, and the effects of AM on proliferation and protein synthesis of these cells were assessed by [3H]thymidine and [3H]phenylalanine incorporation, respectively. RESULTS: Cultured cardiac fibroblasts secreted AM into the medium time-dependently at a rate of 20.3 +/- 3.0 fmol/5 x 10(4) cells/48 h, mean +/- S.D. Northern blot analysis showed expression of preproAM mRNA of 1.6 kb in these cells. In addition, 10(-6) mol/l of angiotensin II (Ang II) and endothelin-1 (ET-1) significantly increased the AM secretion by 55 and 48%, respectively. Synthetic AM significantly reduced 10(-6) mol/l Ang II- or 10(-7) mol/l ET-1-stimulated [3H]thymidine and [3H]phenylalanine incorporation in a dose-dependent manner, and these effects were attenuated by a calcitonin gene-related peptide (CGRP) type 1 receptor antagonist, CGRP(8-37). Synthetic AM also had a dose-dependent stimulatory effect on cAMP accumulation in these cells, which was significantly attenuated by CGRP(8-37). A cAMP analogue, 8-bromo-cAMP, mimicked the AM effects, inhibiting the Ang II-stimulated [3H]thymidine and [3H]phenylalanine incorporation. Blockage of the effect of endogenous AM by anti-AM monoclonal antibody not only significantly reduced the basal level of intracellular cAMP, but also enhanced the [3H]thymidine and [3H]phenylalanine incorporation into the cells. CONCLUSIONS: Cultured neonatal rat cardiac fibroblasts produce and secrete AM, and the secreted AM may inhibit proliferation and protein synthesis of these cells. AM may exert these inhibitory effects partly by elevating intracellular cAMP. It is suggested that AM has an important role in modulating the growth of cardiac fibroblasts in an autocrine or a paracrine manner.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1999

Secretion and clearance of the mature form of adrenomedullin in humans.

In the biosynthesis of adrenomedullin (AM), glycine-extended AM, an intermediate form (iAM) processed from proAM is converted to AM[1-52]-NH2, the bioactive mature form of AM (mAM), by enzymatic amidation. We earlier showed that both molecular forms of AM circulate in human plasma. In the present study, to investigate the secretion and clearance sites of mAM and iAM in humans, we examined the plasma mAM and iAM concentrations in the femoral artery and vein (FA and FV), the aortic root and coronary sinus (AO and CS), and the pulmonary artery and capillary (PA and PC) of patients with ischemic heart disease. Plasma mAM in FV was significantly (p<0.001) higher than in FA. There also was a significant (p<0.001) step-up in the plasma mAM of the CS as compared to the AO. In contrast, plasma mAM was significantly (p<0.001) reduced in the PC as compared to the PA. However, such differences were not observed in plasma iAM levels. These findings suggest that in humans the vasculature of the lower extremities and the heart produce and secrete mAM and that the lung is a clearance site of circulating mAM.

Adrenomedullin↗

PubMed1999

The AATPAP sequence is a very efficient signal for O-glycosylation in CHO cells.

The peptide signal sequence for protein O-glycosylation is not fully characterized, although a recent in vitro study proposed that the sequence motif, XTPXP, serves as a signal for mucin-type O-glycosylation. Here, we show that the AATPAP sequence acts as an efficient O-glycosylation signal, in vivo. A secreted fibroblast growth factor (secFGF) was used as a model to analyze glycosylation and its effects on the biological activity of FGF. Two constructs encoding [AATPAP]secFGF in which AATPAP was introduced at the N- or C-terminus of secFGF were constructed in an eukaryotic expression vector. [AATPAP]secFGF proteins were then expressed in Chinese hamster ovary (CHO) cells and secreted into the surrounding medium, primarily as modified forms sensitive to sialidase but not to peptide N-glycosidase F. The modifying groups were not seen when the AATPAP sequence was converted to AAAPAP or when [AATPAP]secFGF was expressed in mutant cells incapable of UDP-GalNAc biosynthesis. The results indicate that the modifying groups were mucin-type O-glycans and that the AATPAP served as an efficient O-glycosylation signal sequence. The O-glycosylated forms of [AATPAP]secFGF were as mitogenic toward human vascular endothelial cells as unmodified secFGF, suggesting that introduction of the signal into biologically active polypeptides is a promising approach with which O-glycosylation may be achieved without affecting original activity.

Amino Acid Sequence↗

PubMed1999

Region between alpha-helices 3 and 4 of the mad homology 2 domain of Smad4: functional roles in oligomer formation and transcriptional activation.

BACKGROUND: Smad4 has a unique region of 35 amino acids between alpha-helices 3 and 4 (termed H3/4 loop) of the Mad homology (MH) 2 domain. In order to elucidate the functional importance of the H3/4 loop, we prepared chimeric constructs of Smad4 containing the region corresponding to the alpha-helix 3, H3/4 loop and alpha-helix 4 of different Smads, including a chimera containing that of Smad2 (Smad4-HL2). RESULTS: Smad4-HL2 constitutively induced the transcriptional activation of p3TP-Lux, a TGF-beta-responsive reporter construct. However, co-transfection of Smad2 with Smad4-HL2 did not induce a further increase in the activation of p3TP-Lux. Smad4-HL2 did not induce the activation of pAR3-Lux, which contains FAST1-binding sites and is activated by a complex composed of FAST1, Smad2 and Smad4. Smad4-HL2 formed a homo-oligomer more efficiently than wild-type Smad4 in mammalian cells. Moreover, Smad4-HL2 bound to DNA containing the Smad-binding sites with a gretaer affinity than the wild-type Smad4. CONCLUSION: Smad4-HL2 spontaneously forms a homo-oligomer, which may bind to DNA with relatively high affinity and induce transcriptional activation of p3TP-Lux. The H3/4 loop of Smad4 may thus play a role in precluding the spontaneous oligomer formation of Smad4.

Animals↗

PubMed1999

Distribution of fibroblast growth factor-5 in rat hypothalamus, and its possible role as a regulator of feeding behaviour.

We previously reported that a transcript of fibroblast growth factor-5 (FGF-5) was more abundant in the brain of postnatal and adult mice than in the embryonic brain. This suggested that FGF-5 plays some role in the mature brain. Here, we have investigated the spatiotemporal expression and function of FGF-5 in the adult rat hypothalamus with the emphasis on feeding behaviour. In situ hybridization experiments demonstrated that, in both adequately fed and fasted (20 h) rats, FGF-5 transcripts were present within several nuclei in the hypothalamus (viz. the magnocellular part of the paraventricular nucleus, supraoptic nucleus, arcuate nucleus, median eminence, and ventromedial hypothalamic nucleus), but not in the lateral hypothalamic area. Quantitative detection of FGF-5 mRNA in the hypothalamus (especially in the paraventricular nucleus) indicated that food deprivation (20 h) reduced the expression of this gene to almost one-half of that seen in the control (fed) rats. The expression recovered to the control level after 1 h re-feeding, and this recovery persisted for several hours. Furthermore, FGF-5, when infused into the third ventricle, consistently reduced food intake, water intake and body weight gain, all in a dose-dependent manner. These results suggest that FGF-5 in the hypothalamus acts as a physiological regulator of feeding behaviour, and that its decreased expression during food deprivation may be important in stimulating appetite.

Animals↗

PubMed1999

Hereditary sensory neuropathy with deafness and dementia: a clinical and neuroimaging study.

We describe three sibling patients with autosomal dominantly inherited sensory neuropathy, sensorineural hearing loss and dementia. The features of cognitive-behavioral deficits in the patients, including executive dysfunction, apathy, indifference and inattention, were consistent with a frontal lobe dysfunction. Magnetic resonance imaging showed a diffuse brain atrophy. A fluorodeoxyglucose positron emission tomography in one patient and a single photon emission computed tomography in another demonstrated a glucose hypometabolism or a hypoperfusion in the medial frontal and thalamic regions. Primary frontal involvement or frontal dysfunction secondary to thalamic lesions may contribute to the nature of dementia in these patients.

Deafness↗

PubMed1999

Roles of bone morphogenetic protein type I receptors and Smad proteins in osteoblast and chondroblast differentiation.

The biological effects of type I serine/threonine kinase receptors and Smad proteins were examined using an adenovirus-based vector system. Constitutively active forms of bone morphogenetic protein (BMP) type I receptors (BMPR-IA and BMPR-IB; BMPR-I group) and those of activin receptor-like kinase (ALK)-1 and ALK-2 (ALK-1 group) induced alkaline phosphatase activity in C2C12 cells. Receptor-regulated Smads (R-Smads) that act in the BMP pathways, such as Smad1 and Smad5, also induced the alkaline phosphatase activity in C2C12 cells. BMP-6 dramatically enhanced alkaline phosphatase activity induced by Smad1 or Smad5, probably because of the nuclear translocation of R-Smads triggered by the ligand. Inhibitory Smads, i.e., Smad6 and Smad7, repressed the alkaline phosphatase activity induced by BMP-6 or the type I receptors. Chondrogenic differentiation of ATDC5 cells was induced by the receptors of the BMPR-I group but not by those of the ALK-1 group. However, kinase-inactive forms of the receptors of the ALK-1 and BMPR-I groups blocked chondrogenic differentiation. Although R-Smads failed to induce cartilage nodule formation, inhibitory Smads blocked it. Osteoblast differentiation induced by BMPs is thus mediated mainly via the Smad-signaling pathway, whereas chondrogenic differentiation may be transmitted by Smad-dependent and independent pathways.

Activin Receptors↗

PubMed1999

Intracellular signaling of the TGF-beta superfamily by Smad proteins.

TGF-beta is a potent inhibitor of cell growth, and accumulating evidence suggests that perturbation of the TGF-beta signaling pathway leads to tumorigenesis. Smads are recently identified proteins that mediate intracellular signaling of the TGF-beta superfamily. Smads 2 and 3 are phosphorylated by the TGF-beta type I receptor. Smad4 was originally identified as a candidate tumor suppressor gene in pancreatic cancers. Smads 2 and 3 form complexes with Smad4 upon TGF-beta stimulation. The heteromeric Smad complexes translocate into the nucleus, where they activate expression of target genes. Our recent study demonstrated that Smads exist as monomers in the absence of TGF-beta. Smads 2 and 3 form homo- as well as hetero-oligomers with Smad4 upon ligand stimulation. Both homo-oligomers and hetero-oligomers directly bind to DNA, suggesting that the signaling pathway of Smads may be multiplex. Smads 2 and 3 associate with transcriptional coactivators such as p300 in a ligand-dependent manner, p300 enhances transactivation by TGF-beta, suggesting that coactivators link Smads to the basal transcriptional machinery. A missense mutation of Smad2 identified in colorectal and lung cancers was introduced to Smad3. The mutant, Smad3(DE), blocked the activation of wild-type Smad2 and Smad3. Thus, the missense mutation not only disrupts the function of the wild-type Smad but also creates a dominant-negative Smad, which could actively contribute to oncogenesis.

Animals↗

PubMed1999

G alpha-q/11 protein plays a key role in insulin-induced glucose transport in 3T3-L1 adipocytes.

We evaluated the role of the G alpha-q (Galphaq) subunit of heterotrimeric G proteins in the insulin signaling pathway leading to GLUT4 translocation. We inhibited endogenous Galphaq function by single cell microinjection of anti-Galphaq/11 antibody or RGS2 protein (a GAP protein for Galphaq), followed by immunostaining to assess GLUT4 translocation in 3T3-L1 adipocytes. Galphaq/11 antibody and RGS2 inhibited insulin-induced GLUT4 translocation by 60 or 75%, respectively, indicating that activated Galphaq is important for insulin-induced glucose transport. We then assessed the effect of overexpressing wild-type Galphaq (WT-Galphaq) or a constitutively active Galphaq mutant (Q209L-Galphaq) by using an adenovirus expression vector. In the basal state, Q209L-Galphaq expression stimulated 2-deoxy-D-glucose uptake and GLUT4 translocation to 70% of the maximal insulin effect. This effect of Q209L-Galphaq was inhibited by wortmannin, suggesting that it is phosphatidylinositol 3-kinase (PI3-kinase) dependent. We further show that Q209L-Galphaq stimulates PI3-kinase activity in p110alpha and p110gamma immunoprecipitates by 3- and 8-fold, respectively, whereas insulin stimulates this activity mostly in p110alpha by 10-fold. Nevertheless, only microinjection of anti-p110alpha (and not p110gamma) antibody inhibited both insulin- and Q209L-Galphaq-induced GLUT4 translocation, suggesting that the metabolic effects induced by Q209L-Galphaq are dependent on the p110alpha subunit of PI3-kinase. In summary, (i) Galphaq appears to play a necessary role in insulin-stimulated glucose transport, (ii) Galphaq action in the insulin signaling pathway is upstream of and dependent upon PI3-kinase, and (iii) Galphaq can transmit signals from the insulin receptor to the p110alpha subunit of PI3-kinase, which leads to GLUT4 translocation.

3T3 Cells↗

PubMed1999

An SH2 domain-containing 5' inositolphosphatase inhibits insulin-induced GLUT4 translocation and growth factor-induced actin filament rearrangement.

Tyrosine kinase receptors lead to rapid activation of phosphatidylinositol 3-kinase (PI3 kinase) and the subsequent formation of phosphatidylinositides (PtdIns) 3,4-P2 and PtdIns 3,4, 5-P3, which are thought to be involved in signaling for glucose transporter GLUT4 translocation, cytoskeletal rearrangement, and DNA synthesis. However, the specific role of each of these PtdIns in insulin and growth factor signaling is still mainly unknown. Therefore, we assessed, in the current study, the effect of SH2-containing inositol phosphatase (SHIP) expression on these biological effects. SHIP is a 5' phosphatase that decreases the intracellular levels of PtdIns 3,4,5-P3. Expression of SHIP after nuclear microinjection in 3T3-L1 adipocytes inhibited insulin-induced GLUT4 translocation by 100 +/- 21% (mean +/- the standard error) at submaximal (3 ng/ml) and 64 +/- 5% at maximal (10 ng/ml) insulin concentrations (P < 0.05 and P < 0.001, respectively). A catalytically inactive mutant of SHIP had no effect on insulin-induced GLUT4 translocation. Furthermore, SHIP also abolished GLUT4 translocation induced by a membrane-targeted catalytic subunit of PI3 kinase. In addition, insulin-, insulin-like growth factor I (IGF-I)-, and platelet-derived growth factor-induced cytoskeletal rearrangement, i.e., membrane ruffling, was significantly inhibited (78 +/- 10, 64 +/- 3, and 62 +/- 5%, respectively; P < 0.05 for all) in 3T3-L1 adipocytes. In a rat fibroblast cell line overexpressing the human insulin receptor (HIRc-B), SHIP inhibited membrane ruffling induced by insulin and IGF-I by 76 +/- 3% (P < 0.001) and 68 +/- 5% (P < 0.005), respectively. However, growth factor-induced stress fiber breakdown was not affected by SHIP expression. Finally, SHIP decreased significantly growth factor-induced mitogen-activated protein kinase activation and DNA synthesis. Expression of the catalytically inactive mutant had no effect on these cellular responses. In summary, our results show that expression of SHIP inhibits insulin-induced GLUT4 translocation, growth factor-induced membrane ruffling, and DNA synthesis, indicating that PtdIns 3,4,5-P3 is the key phospholipid product mediating these biological actions.

3T3 Cells↗

PubMed1999

Case-control study of presenilin-1 intronic polymorphism in sporadic early and late onset Alzheimer's disease.

OBJECTIVE: Presenilin-1 is a major causative gene for early onset familial Alzheimer's disease, and the apolipoprotein E epsilon4 allele is a major genetic risk factor known to influence late onset and sporadic early onset Alzheimer's disease. The presenilin-1 1/1 genotype has recently been reported to be associated with sporadic Alzheimer's disease. The purpose of this study is to determine whether Alzheimer's disease is associated with presenilin-1 gene polymorphism and the apolipoprotein E genotype in an extended case-control study. METHODS: An examination was conducted on 217 patients with Alzheimer's disease, along with an equal number of age and sex matched controls derived from the same community in a Japanese population, by using a chi2 test for homogeneity and a logistic regression analysis. A meta-analysis of data from the literature on allele frequencies in Alzheimer's disease and control populations was used for comparison with the Japanese allele frequencies obtained in this study. RESULTS: The presenilin-1 allele-1 frequencies were similar in patients with early onset Alzheimer's disease (0.61) and younger controls (0.61), and in those with late onset Alzheimer's disease (0.63) and elderly controls (0. 63). We found no evidence for a possible association between the presenilin-1 polymorphism and the apolipoprotein E epsilon4 allele. However, the meta-analysis showed that the association between the presenilin-1 1/1 genotype and Alzheimer's disease was significant (Peto odds ratio=1.16, 95% confidence interval=1.04-1.31). CONCLUSIONS: These results suggest a subtle but positive association of presenilin-1 gene polymorphism with Alzheimer's disease, although Japanese data in this study which failed to support such a relation would indicate an ethnic variation.

Adult↗

PubMed1999

Amygdalar volume and emotional memory in Alzheimer's disease.

OBJECTIVE: Everyday experience suggests that highly emotional events are often the most memorable. Experimental work in animals and humans has demonstrated that the amygdaloid complex plays a crucial role in emotional memory, i.e., memory of events arousing strong emotions. The aim of this study was to elucidate the relationship between medial temporal damage and impaired memory of real-life emotional events in patients with Alzheimer's disease. METHOD: In 36 patients with probable Alzheimer's disease who experienced the 1995 earthquake in Kobe, Japan, memories of events surrounding the earthquake were examined as an index of emotional memory with the use of a semistructured interview, and amygdalar and hippocampal volumes were quantified by magnetic resonance imaging. The effects of the atrophy of these structures on recall performance were determined by multiple regression analysis. RESULTS: Irrespective of generalized brain atrophy and cognitive impairments, emotional memory was correlated more with normalized amygdalar volume (right and left averaged) than with normalized hippocampal volume. General knowledge of the earthquake was correlated with neither amygdalar nor hippocampal volume. CONCLUSIONS: The results indicate that impairment of emotional event memory in patients with Alzheimer's disease is related to intensity of amygdalar damage and provide evidence of the amygdala's involvement in emotional memory in humans.

Aged↗

PubMed1999

Lack of effect of apolipoprotein E E4 allele on neuropsychiatric manifestations in Alzheimer's disease.

The association between the apolipoprotein E epsilon 4 (APOE E4) allele and a wide spectrum of behavioral symptoms of Alzheimer's disease (AD) was investigated. Neither the severity nor the presence of any behavioral changes was associated with the number of APOE E4 alleles, even after controlling for the effects of age at onset, sex, education level, duration of illness, and severity of dementia. The findings do not support the hypothesis that neuropsychiatric manifestations of AD are different in patients with the APOE E4 allele.

Aged↗

PubMed1999

Distinctive neurobehavioral features among neurodegenerative dementias.

The distinctive neuropsychiatric features of Alzheimer's disease (AD), dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD) were investigated by using the Neuropsychiatric Inventory. The patients with FTD had significantly more euphoria, aberrant motor activity, and disinhibition and significantly fewer delusions compared with the patients with AD or DLB. The patients with DLB had significantly more hallucinations compared with the AD or FTD patients. The findings clearly demonstrate that AD, DLB, and FTD have distinctive neuropsychiatric features, which may correspond to different patterns of cerebral involvement characteristic of these three major degenerative dementias.

Aged↗

PubMed1999

Characterization of bone morphogenetic protein-6 signaling pathways in osteoblast differentiation.

Bone morphogenetic protein (BMP)-6 is a member of the transforming growth factor (TGF)-(&bgr;) superfamily, and is most similar to BMP-5, osteogenic protein (OP)-1/BMP-7, and OP-2/BMP-8. In the present study, we characterized the endogenous BMP-6 signaling pathway during osteoblast differentiation. BMP-6 strongly induced alkaline phosphatase (ALP) activity in cells of osteoblast lineage, including C2C12 cells, MC3T3-E1 cells, and ROB-C26 cells. The profile of binding of BMP-6 to type I and type II receptors was similar to that of OP-1/BMP-7 in C2C12 cells and MC3T3-E1 cells; BMP-6 strongly bound to activin receptor-like kinase (ALK)-2 (also termed ActR-I), together with type II receptors, i.e. BMP type II receptor (BMPR-II) and activin type II receptor (ActR-II). In addition, BMP-6 weakly bound to BMPR-IA (ALK-3), to which BMP-2 also bound. In contrast, binding of BMP-6 to BMPR-IB (ALK-6), and less efficiently to ALK-2 and BMPR-IA, together with BMPR-II was detected in ROB-C26 cells. Intracellular signalling was further studied using C2C12 and MC3T3-E1 cells. Among the receptor-regulated Smads activated by BMP receptors, BMP-6 strongly induced phosphorylation and nuclear accumulation of Smad5, and less efficiently those of Smad1. However, Smad8 was constitutively phosphorylated, and no further phosphorylation or nuclear accumulation of Smad8 by BMP-6 was observed. These findings indicate that in the process of differentiation to osteoblasts, BMP-6 binds to ALK-2 as well as other type I receptors, and transduces signals mainly through Smad5 and possibly through Smad1.

3T3 Cells↗

PubMed1999

Activation of protein C by arginine-specific cysteine proteinases (gingipains-R) from Porphyromonas gingivalis.

In order to determine the effect of bacterial proteinases on activation of the protein C system, a negative regulator of blood coagulation, two arginine-specific cysteine proteinases (gingipains R) from Porphyromonas gingivalis, a causative bacterium of adult periodontitis, were examined. Each enzyme activated human protein C in a dose- and incubation time-dependent manner. Interestingly, the form of enzyme being composed of a non-covalent complex containing both catalytic and adhesion domains (RgpA) produced activated protein C 14-fold more efficiently than RgpB which contained the catalytic domain alone. The kcat/Km value of RgpA was 18-fold higher than that of RgpB and comparable to that of the thrombin-thrombomodulin complex, the physiological activator of protein C. RgpA catalyzed protein C activation was augmented 1.4-fold by phospholipids, ubiquitous cell membrane components. Furthermore, RgpA, but not RgpB, could activate protein C in plasma and this resulted in a decrease of the protein C concentration in plasma, which is often observed in patients with sepsis during the development of disseminated intravascular coagulation (DIC). These data indicate that RgpA is a more potent activator of protein C than RgpB and suggest that only the former enzyme can cause protein C activation in vivo. The present study further suggests that bacterial proteinases may possibly contribute to the consumption of plasma protein C which predisposes to DIC and/or promotes a thrombotic tendency towards DIC in sepsis.

Adhesins, Bacterial↗