Contribution of a prosegment lysine residue to the function and structure of porcine pepsinogen A and its active form pepsin A

A conserved lysine residue, Lys36p, on the prosegment of pepsinogen was replaced with a positively charged arginine (K36pR), a negatively charged glutamic acid (K36pE), and a neutral side chain methionine (K36pM). K36pM and K36pE mutants were extremely unstable and degraded rapidly, especially K36pE, which was inactivated during purification. This instability was confirmed by microcalorimetry where the denaturing temperatures for K36pM and K36pE were 6 degrees C and 10 degrees C lower than the wild-type, respectively. As a function of pH, K36pM and K36pR were activated over a broader range of pH as compared with wild-type. The mutant pepsinogens were activated faster than wild-type with K36pM being activated approximately 10 times faster. The activated pepsins from the various mutant pepsinogens showed lower kinetic efficiency than wild-type enzyme. Catalytic rate constants were reduced by half. The results suggested Lys36p is important for the correct folding of the active-centre residues. The molecular modeling calculation suggested that the position of Asp215 was substantially altered. In conclusion, the above results would suggest that Lys36p was important not only for stability of the prosegment and pepsinogen, but also for the correct alignment of the active-centre residues.

CIPER, a novel NF kappaB-activating protein containing a caspase recruitment domain with homology to Herpesvirus-2 protein E10

We have identified and characterized CIPER, a novel protein containing a caspase recruitment domain (CARD) in its N terminus and a C-terminal region rich in serine and threonine residues. The CARD of CIPER showed striking similarity to E10, a product of the equine herpesvirus-2. CIPER formed homodimers via its CARD and interacted with viral E10 but not with several apoptosis regulators containing CARDs including ARC, RAIDD, RICK, caspase-2, caspase-9, or Apaf-1. Expression of CIPER induced NF-kappaB activation, which was inhibited by dominant-negative NIK and a nonphosphorylable IkappaB-alpha mutant but not by dominant-negative RIP. Mutational analysis revealed that the N-terminal region of CIPER containing the CARD was sufficient and necessary for NF-kappaB-inducing activity. Point mutations in highly conserved residues in the CARD of CIPER disrupted the ability of CIPER to activate NF-kappaB and to form homodimers, indicating that the CARD is essential for NF-kappaB activation and dimerization. We propose that CIPER acts in a NIK-dependent pathway of NF-kappaB activation.

Identification of regulatory and catalytic domains in the apoptosis nuclease DFF40/CAD

The DNA fragmentation factor (DFF) is composed of two subunits, the 40-kDa caspase-3-activated nuclease (DFF40/CAD) and its 45-kDa inhibitor (DFF45/ICAD). During apoptosis, DFF-40/CAD is activated by caspase-3-mediated cleavage of DFF45/ICAD. Mutational analysis of DFF40/CAD revealed that DFF40/CAD is composed of a C-terminal catalytic domain and an N-terminal regulatory domain. Deletion of the catalytic domain (residues 290-345) abrogated the caspase-3-induced nuclease activity of DFF40/CAD but not its ability to interact with DFF45/ICAD. Conversely, removal of the regulatory domain (residues 1-83) yielded a constitutively active DFF40/CAD nuclease that neither bound to its inhibitor nor required caspase-3 for activation. Amino acid alignment revealed that the regulatory domain of DFF40/CAD has homology to the N-terminal region of mammalian and Drosophila DFF45/ICAD and CIDE-N, a regulatory domain previously identified in pro-apoptotic CIDE proteins. Mutational analysis of the N-terminal region revealed mutants with diminished nuclease activity but with intact ability to bind DFF45/ICAD. Thus, CIDE-N represents a new type of domain that is associated with the regulation of the apoptosis/DNA fragmentation pathway.

Diva, a Bcl-2 homologue that binds directly to Apaf-1 and induces BH3-independent cell death

We have identified and characterized Diva, which is a novel regulator of apoptosis. Sequence analysis revealed that Diva is a member of the Bcl-2 family of proteins containing Bcl-2 homology domain 1, 2, 3, and 4 (BH1, BH2, BH3, and BH4) regions and a carboxyl-terminal hydrophobic domain. The expression of Diva mRNA was detected in multiple embryonic tissues but was restricted to the ovary and testis in adult mice. The expression of Diva promoted the death of 293T, Ramsey, and T47D cells as well as that of primary sensory neurons, indicating that Diva is a proapoptotic protein. Significantly, Diva lacks critical residues in the conserved BH3 region that mediate the interaction between BH3-containing proapoptotic Bcl-2 homologues and their prosurvival binding partners. Consistent with this, Diva did not bind to cellular Bcl-2 family members including Bcl-2, Bcl-XL, Bcl-w, Mcl-1, and A1/Bfl-1. Furthermore, mutants of Diva lacking the BH3 region fully retained their proapoptotic activity, confirming that Diva promotes apoptosis in a BH3-independent manner. Significantly, Diva interacted with a viral Bcl-2 homologue (vBcl-2) encoded by the Kaposi's sarcoma-associated herpesvirus. Consistent with these associations, apoptosis induced by Diva was inhibited by vBcl-2 but not by Bcl-XL. Importantly, Diva interacted with Apaf-1, an adapter molecule that activates caspase-9, a central death protease of the apoptotic pathway. The expression of Diva inhibited the binding of Bcl-XL to Apaf-1, as determined by immunoprecipitation assays. Thus, Diva represents a novel type of proapoptotic Bcl-2 homologue that promotes apoptosis independently of the BH3 region through direct binding to Apaf-1, thus preventing Bcl-XL from binding to the caspase-9 regulator Apaf-1.

Actinobacillus actinomycetemcomitans toxin induces both cell cycle arrest in the G2/M phase and apoptosis

We found that the culture supernatant of the periodontopathic bacterium Actinobacillus actinomycetemcomitans had a cytotoxic effect on several cell lines. In this study, we purified the toxin from the culture supernatant of A. actinomycetemcomitans Y4 by a four-step procedure: ammonium sulfate precipitation, POROS HQ/M column chromatography, polymyxin B matrix column chromatography, and Mono-Q column chromatography. The purified toxin gave two major bands of protein with molecular masses of 80 and 85 kDa upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The mechanism of cell death of the B-cell hybridoma cell line HS-72 was examined by observing changes in nuclear morphology, an increase in the proportion of fragmented DNA, and the typical ladder pattern of degraded chromosomal DNA, indicating the induction of apoptosis. Overexpression of human Bcl-2 suppressed apoptosis in HS-72 cells, indicating that the toxin from A. actinomycetemcomitans induces apoptosis by a Bcl-2-inhibitable mechanism. Flow cytometric analysis revealed that the toxin caused cell cycle arrest in the G2/M phase and apoptosis in HS-72 cells. In addition, aurintricarboxylic acid, a DNA endonuclease inhibitor, markedly decreased the percentage of apoptotic cells but had no effect on cell cycle arrest in the G2/M phase. Taken together, these findings suggest that the toxin from A. actinomycetemcomitans could mediate the development of periodontal diseases through cell cycle arrest in the G2/M phase and apoptosis in B lymphocytes of periodontal tissue.

The role of activin type I receptors in activin A-induced growth arrest and apoptosis in mouse B-cell hybridoma cells

Activins transduce their signals by binding to activin type I receptors and activin type II receptors, both of which contain a serine/threonine kinase domain. In this study, we established stable transfectants expressing two types of activin receptors, ActRI and ActRIB, to clarify the role of these receptors in activin signalling for growth inhibition in HS-72 mouse B-cell hybridoma cells. Over-expression of ActRI suppressed activin A-induced cell-cycle arrest in the G1 phase caused by inhibition of retinoblastoma protein phosphorylation through induction of p21CIP1/WAF1, a cyclin-dependent kinase inhibitor, and subsequent apoptosis. In contrast, HS-72 clones that over-expressed ActRIB significantly facilitated activin A-induced apoptosis. These results indicate that ActRI and ActRIB are distinct from each other and that the ActRI/ActRIB expression ratio could regulate cell-cycle arrest in the G1 phase and subsequent apoptosis in HS-72 cells induced by activin A.

Presence of activated B-1 cells in chronic inflamed gingival tissue

B-1 cells are physically and functionally unique B cells that produce polyreactive natural antibody. This study examined the activation of B-1 cells in inflamed gingival tissue. Serum IgG antibodies to phosphorylcholine, E. coli LPS, DNA, and some commensal bacteria were examined in adult periodontitis patients and healthy subjects. In addition, the proportion of B-1a (CD20+CD5+) cells and the amount of IL-6 and IL-10 in the inflamed gingival tissues were examined. The serum levels of IgG antibodies to phosphorylcholine, E. coli LPS, and commensal bacteria were significantly higher in the adult periodontitis patients than the healthy subjects. The proportion of B-1a cells and the amount of IL-6 and IL-10 were significantly higher in the inflamed gingival tissues than in peripheral blood from the healthy subjects. These results suggest the activation of B-1 cells in the inflamed gingival tissue of adult periodontitis patients, and that B-1 cells may serve as the first line of defense by producing polyreactive antibodies to phosphorylcholine, LPS, and commensal bacteria.

Purification and characterization of a feruloylesterase from Aspergillus awamori

A feruloylesterase was purified from the extracellular broth of Aspergillus awamori grown on wheat bran culture. The purified enzyme gave a single band on SDS-polyacrylamide gel electrophoresis and isoelectric focusing, with an apparent M(r) of 35,000 and a pI of 3.8, respectively. The substrate specificity of the purified enzyme differed obviously from that of acetylesterase of A. awamori. The enzyme bound to microcrystalline cellulose.

Correlation between Bcl-X expression and B-cell hybridoma apoptosis induced by activin A

In this study, we examined the role of bcl-XL and bcl-XS in apoptotic cell death of HS-72 cells induced by activin A. Immunoblot analysis revealed that a band of Bcl-XL was detected in HS-72 cells cultured with or without activin A. Although untreated HS-72 cells did not express Bcl-XS, the expression of Bcl-XS was significantly increased when cultured with activin A. We also investigated the expression of Bcl-XS and Bcl-XL in HS-72 cells cultured with activin A in the presence of protein kinase C inhibitor 1-(5-isoquinotinesulfonyl)-2-methylpiperazine dihydrochloride (H7), which suppressed apoptosis in HS-72 cells induced by activin A. Exposure to H7 apparently increased the level of Bcl-XL in HS-72 cells cultured with or without activin A. In contrast, no detectable band of Bcl-XS was found in HS-72 cells cultured with activin A and H7. These findings indicate that Bcl-XL upregulation and Bcl-XS downregulation induced by H7 might correlate with the suppression of activin A-induced apoptosis in B-lineage cells.

Two different types of humoral immune response to Actinobacillus actinomycetemcomitans in high-responder periodontitis patients

Actinobacillus actinomycetemcomitans is considered to be an aetiological agent in various forms of periodontitis, with serotype b-specific carbohydrate being the immunodominant antigen of A. actinomycetemcomitans Y4 in high-responder patients. Lipopolysaccharide (LPS) of the organism may also be an important antigen. The purpose of the present study was to clarify the importance of LPS as an antigen of A. actinomycetemcomitans. Twenty patients who had high antibody titres to strain Y4 were selected, and the reactivity of their sera with LPS was determined by ELISA and Western blotting. Two groups of patients were observed: group 1 had high IgG titres only to serotype b strain, whereas group 2 had high IgG titres to serotypes a, b and c strains. The results of adsorption tests showed that anti-A. actinomycetemcomitans Y4 antibody in group 1 patients mostly consisted of antibody reactive with the serotype b-specific carbohydrate, whereas the antibody in group 2 patients mostly consisted of antibody reactive with the LPS of all serotypes. These data show that anti-LPS antibody is present and predominant in anti-A. actinomycetemcomitans Y4 antibody from some high-responder patients, and indicate an important role for LPS as an antigen in the humoral immune response to the organism.

RICK, a novel protein kinase containing a caspase recruitment domain, interacts with CLARP and regulates CD95-mediated apoptosis

Signaling through the CD95/Fas/APO-1 death receptor plays a critical role in the homeostasis of the immune system. RICK, a novel protein kinase that regulates CD95-mediated apoptosis was identified and characterized. RICK is composed of an N-terminal serine-threonine kinase catalytic domain and a C-terminal region containing a caspase-recruitment domain. RICK physically interacts with CLARP, a caspase-like molecule known to bind to Fas-associated protein with death domain (FADD) and caspase-8. Expression of RICK promoted the activation of caspase-8 and potentiated apoptosis induced by Fas ligand, FADD, CLARP, and caspase-8. Deletion mutant analysis revealed that both the kinase domain and caspase-recruitment domain were required for RICK to promote apoptosis. Significantly, expression of a RICK mutant in which the lysine of the putative ATP-binding site at position 38 was replaced by a methionine functioned as an inhibitor of CD95-mediated apoptosis. Thus, RICK represents a novel kinase that may regulate apoptosis induced by the CD95/Fas receptor pathway.

Installation of new damped cavities at the Photon Factory storage ring

New damped cavities have been installed in the Photon Factory (PF) storage ring and successfully operated in the last scheduled user run of 1996. The new damped cavity is a simple single-cell cavity with somewhat large beam-duct holes. The part of the beam duct that is attached to the cavity is made of SiC, which works as a microwave absorber and damps the higher-order modes excited in the cavity. Because of its simple structure, the operation of the cavity is very stable and also a high power input of more than 150 kW is possible. No coupled-bunch instabilities due to the new cavity were observed during operation.

CIDE, a novel family of cell death activators with homology to the 45 kDa subunit of the DNA fragmentation factor

DFF45 is a subunit of the DNA fragmentation factor (DFF) that is cleaved by caspase-3 during apoptosis. However, the mechanism by which DFF45 regulates apoptotic cell death remains poorly understood. Here we report the identification and characterization of two mammalian genes, CIDE-A and CIDE-B, encoding highly related proteins with homology to the N-terminal region of DFF45. CIDE-A and CIDE-B were found to activate apoptosis in mammalian cells, which was inhibited by DFF45 but not by caspase inhibitors. Expression of CIDE-A induced DNA fragmentation in 293T cells, which was inhibited by DFF45, further suggesting that DFF45 inhibits the apoptotic activities of CIDEs. In addition to mammalian CIDE-A and CIDE-B, we identified DREP-1, a Drosophila melanogaster homolog of DFF45 that could inhibit CIDE-A-mediated apoptosis. Mutant analysis revealed that the C-terminal region of CIDE-A was necessary and sufficient for killing whereas the region with homology to DFF45 located in the N-terminus was required for DFF45 to inhibit CIDE-A-induced apoptosis. CD95/Fas-mediated apoptosis was enhanced by CIDEs but inhibited by DFF45. These studies suggest that DFF45 is evolutionarily conserved and implicate CIDEs as DFF45-inhibitable effectors that promote cell death and DNA fragmentation.

ARC, an inhibitor of apoptosis expressed in skeletal muscle and heart that interacts selectively with caspases

We have identified and characterized ARC, apoptosis repressor with caspase recruitment domain (CARD). Sequence analysis revealed that ARC contains an N-terminal CARD fused to a C-terminal region rich in proline/glutamic acid residues. The CARD domain of ARC exhibited significant homology to the prodomains of apical caspases and the CARDs present in the cell death regulators Apaf-1 and RAIDD. Immunoprecipitation analysis revealed that ARC interacts with caspase-2, -8, and Caenorhabditis elegans CED-3, but not with caspase-1, -3, or -9. ARC inhibited apoptosis induced by caspase-8 and CED-3 but not that mediated by caspase-9. Further analysis showed that the enzymatic activity of caspase-8 was inhibited by ARC in 293T cells. Consistent with the inhibition of caspase-8, ARC attenuated apoptosis induced by FADD and TRADD and that triggered by stimulation of death receptors coupled to caspase-8, including CD95/Fas, tumor necrosis factor-R1, and TRAMP/DR3. Remarkably, the expression of human ARC was primarily restricted to skeletal muscle and cardiac tissue. Thus, ARC represents an inhibitor of apoptosis expressed in muscle that appears to selectively target caspases. Delivery of ARC by gene transfer or enhancement of its endogenous activity may provide a strategy for the treatment of diseases that are characterized by inappropriately increased cell death in muscle tissue.

Differentiation of clinical isolates of Actinobacillus actinomycetemcomitans using an insertion sequence, ISAa1

We previously identified an IS200-like sequence (ISAa1) in the genome of Actinobacillus actinomycetemcomitans FDC Y4. One or more hybridizing bands to the ISAa1 probe were detected in each of several reference strains, representing three of the serotypes (a through c) of A. actinomycetemcomitans. In this study, we examined whether a restriction fragment-length polymorphism (RFLP) with ISAa1 as a probe could differentiate clinical isolates. One or more hybridizing bands were detected in each of the 27 strains examined, which could be divided into seven groups according to restriction fragment-length polymorphism pattern. Several strains were observed with identical restriction fragment-length polymorphism types but with different serotypes. Conversely, strains were also observed with differing restriction fragment-length polymorphism types and identical serotypes.

Increase in Bcl-2 level promoted by CD40 ligation correlates with inhibition of B cell apoptosis induced by vacuolar type H(+)-ATPase inhibitor

We have previously demonstrated that cell death of WEHI-231 cells induced by specific inhibitors of vacuolar type H(+)-ATPase (V-ATPase) occurs through apoptosis. CD40 is involved in regulating activation, differentiation, and apoptosis of B cells. Here we show that the CD40 ligation rescues WEHI-231 cells from apoptotic cell death induced by a specific V-ATPase inhibitor, concanamycin A. CD40 signaling with anti-CD40 antibody resulted in the induction of Bcl-2 and Bcl-XL proteins in WEHI-231 cells. Constitutive expression of Bcl-2 but not Bcl-XL inhibited concanamycin A-induced apoptosis. These findings suggest that the expression of Bcl-2 mediated through CD40 signaling rescues the apoptotic cell death induced by blockade of V-ATPase. Interestingly, the acidification of intracellular acidic compartments was completely inhibited when WEHI-231 cells were cultured with concanamycin A, even in the presence of anti-CD40 antibody. In addition, apoptosis in WEHI-231 cells induced by concanamycin A was strongly suppressed when cultured with imidazole, a cell-permeable base, suggesting that apoptosis induced by concanamycin A is preceded by intraacidification.

Structural characterization of the molten globule and native states of ovalbumin: a 1H NMR study

Molecular characteristics of ovalbumin (OVA) in the acidic (pD 3.08, the E-form) and neutral [pD 7.29, the N-form (native form)] regions were studied by measuring effective radii, 1H NMR spectra, spin-echo 1H NMR spectra and cross-relaxation times (TIS) from irradiated to observed protein protons which are particularly sensitive for detection of the mobile segments and/or structural looseness in proteins. 1H NMR spectra did not show significant differences between the N- and E-forms except for the spectral lines in the CH3, epsilon CH2 and aromatic regions. Effective radii and TIS values for main- and side-chains showed 1.08 and 1.5- to 2.0-fold increases on going from the N- to E-forms, respectively. The elongation of TIS values might indicate the appearance of the fluctuating tertiary structure in the E-form. Molecular characteristics of the E-form, inferred from reported far ultraviolet-circular dichroism (UV-CD) spectra in the peptide region, near UV-CD spectra in the aromatic region [Koseki et al. (1988) J. Biochem. 103, 425-430], effective radii and especially elongation of TIS values might indicate that the E-form could be in the molten globule state. The onset of denaturation of OVA using TIS measurements was also studied.

[The prevalence of orthostatic dysregulation complicated with bronchial asthma]

Orthostatic dysregulation (OD) has been reported to be complicated with childhood bronchial asthma. 42 patients (28 females and 14 males) with adult-onset bronchial asthma were selected randomly to investigate the prevalence of OD. OD was diagnosed by both questionnaire for subjective symptoms and tilting test (Schellong test and upright ECG). Our results revealed that 64.3% (both 64.3% in females and males) of the patients were complicated with OD. There was no significant difference in the duration of asthma, FEV0.1, %FEV1.0, serum IgE level, and severity of asthma between patients with OD and without OD. Furthermore, no significant difference in the results of tilting test were observed. In serum level of theophylline we couldn't detect any subjective difference between the two groups, however there was significant difference between positive patients and negative patients in tilting test. In conclusion, OD is frequently complicated with adult-onset asthma and we should be careful of the subjective symptoms concerned with OD.

Prevalence of Actinobacillus actinomycetemcomitans serotypes in Japanese patients with periodontitis

Oral Actinobacillus actinomycetemcomitans strains are serologically classified into 5 distinct groups, a to e. We examined the distribution of A. actinomycetemcomitans serotypes in Japanese patients with periodontitis. A total of 157 A. actinomycetemcomitans clinical isolates from diseased sites of 39 patients with periodontitis were serotyped by using serotype-specific rabbit antisera against A. actinomycetemcomitans serotypes a, b, c, d and e strains. In the immunodiffusion assay, autoclaved extracts of 42, 6, 39, 9 and 41 A. actinomycetemcomitans clinical isolates reacted with serotypes a, b, c, d and e antisera, respectively. Although 37 patients were infected with a serotype strain, 2 patients harbored 2 different serotype strains, b/e and b/untypeable. To establish a correlation between serotype and genotype of A. actinomycetemcomitans clinical isolates from 2 patients who had different serotype strains, we used arbitrarily primed polymerase chain reaction (AP-PCR) to fingerprint clinical isolates of different serotypes. The AP-PCR genotypes among 4 clinical isolates (b/e and b/untypeable) were identical to that of A. actinomycetemcomitans Y4 (serotype b), indicating the presence of multiple A. actinomycetemcomitans serotypes which are genetically homogeneous in the periodontally diseased sites of patients with periodontitis.

[Results of a survey of Japanese cedar pollinosis in Hachijyojima]

We performed a questionnaire survey of Japanese cedar pollinosis among 7,946 residents of the Sakashita region (Mitsune, Ogago) and Sakaue region (Kashidate, Sueyoshi, Nakanogo) of Hachijyojima who were at least 15 years of age. The response rate was 21.3%. The percentage of respondents who reported three or more nasal symptoms concurrentry with two ocular symptoms in early spring (from the end of February to the end of March) was 1.8% in the Sakashita region and 0.3% in the Sakaue region. About 1.5% of Hachijyojima residents were suspected to have Japanese cedar pollinosis. On scratch tests of symptomatic subjects, 9.2% showed positive reactions for Japanese cedar antigen, and 12.1% had an IgE RAST score of 2 or more. The peak Japanese cedar pollen concentration between February 11 and March 31, 1992 was 74/cm2 on March 6 in the Sakashita region and 127/cm2 on the same day in the Sakaue region. This survey confirmed the presence of a low incidence of Japanese cedar pollinosis in Hachijyojima, an isolated island 290 km from Tokyo.

Serum levels of eosinophil cationic protein and IL-5 in patients with asthma without systemic corticosteroids

We measured the serum levels of eosinophil cationic protein (ECP) and interleukin-5 (IL-5) in 39 patients with asthma (symptomatic 12, asymtomatic 27) without systemic corticosteroids and 49 healthy subjects. There were significant differences in serum levels in both ECP and IL-5 between symptomatic and asymptomatic asthma, and healthy subjects. A significant positive correlation was found between serum levels of ECP and IL-5. No significant correlation was found between %FEV1 and serum level of ECP or IL-5, however, when the analysis was restricted to patients of less than 60 years of age, the correlations were significant. These results suggest that IL-5 is one of the factors that activate eosinophils even in peripheral blood, and that measurement of serum levels of ECP and IL-5 is useful for in vitro monitoring of asthma.

CLARP, a death effector domain-containing protein interacts with caspase-8 and regulates apoptosis

We have identified and characterized CLARP, a caspase-like apoptosis-regulatory protein. Sequence analysis revealed that human CLARP contains two amino-terminal death effector domains fused to a carboxyl-terminal caspase-like domain. The structure and amino acid sequence of CLARP resemble those of caspase-8, caspase-10, and DCP2, a Drosophila melanogaster protein identified in this study. Unlike caspase-8, caspase-10, and DCP2, however, two important residues predicted to be involved in catalysis were lost in the caspase-like domain of CLARP. Analysis with fluorogenic substrates for caspase activity confirmed that CLARP is catalytically inactive. CLARP was found to interact with caspase-8 but not with FADD/MORT-1, an upstream death effector domain-containing protein of the Fas and tumor necrosis factor receptor 1 signaling pathway. Expression of CLARP induced apoptosis, which was blocked by the viral caspase inhibitor p35, dominant negative mutant caspase-8, and the synthetic caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-(OMe)-fluoromethylketone (zVAD-fmk). Moreover, CLARP augmented the killing ability of caspase-8 and FADD/MORT-1 in mammalian cells. The human clarp gene maps to 2q33. Thus, CLARP represents a regulator of the upstream caspase-8, which may play a role in apoptosis during tissue development and homeostasis.

An Aspergillus awamori acetylesterase: purification of the enzyme, and cloning and sequencing of the gene

An inducible acetylesterase was purified from the culture medium of Aspergillus awamori strain IFO4033 growing on wheat-bran culture by ion-exchange, gel-filtration and hydrophobic-interaction chromatographies. The purified enzyme had an Mr of 31000 and contained Asn-linked oligosaccharides. The enzyme liberated acetic acid from wheat bran, hydrolysed only alpha-naphthyl acetate and propionate when aromatic esters were used for the substrate, and was tentatively classified as a carboxylic esterase (EC 3.1.1.1). The gene encoding acetylesterase was cloned and sequenced. The deduced amino acid sequence showed that acetylesterase was produced as a 304-amino-acid-residue precursor, which was converted post-translationally into a 275-amino-acid-residue mature protein. Part of the sequence of acetylesterase was similar to the region near the active-site serine of lipases of Geotrichum candidum and Candida cylindracea. A unique site of putative Asn-linked oligosaccharides was presented.

Activin A induction of cell-cycle arrest involves modulation of cyclin D2 and p21CIP1/WAF1 in plasmacytic cells

Activins, members of the transforming growth factor-beta family, have been implicated in the regulation of growth and differentiation of various types of cells. We have recently found that activin A induces apoptotic cell death of plasmacytic cells including B cell hybridoma cells and myeloma cells. In the present study, we demonstrated that activin A caused cell-cycle arrest in the G1 phase before appearance of apoptotic cells in mouse B cell hybridoma cells. Phosphorylation of retinoblastoma protein (Rb) and in vitro Rb kinase activity of cyclin-dependent kinase (CDK)4 was inhibited in activin A-treated cells. Analysis of expression of genes regulating Rb phosphorylation revealed that activin A suppressed cyclin D2, the sole D-type cyclin gene expressed in the hybridoma cells, and activated p21CIP1/WAF1 but had no effect on expression of cyclin-dependent kinases (CDK2, CDK4, CDK6) and other CDK inhibitors (p27KIP1, p16INK4a, p15INK4b). Modulation of cyclin D2 and p21CIP1/WAF1 expression resulted in a decrease in level of cyclin D2-CDK4 complex and an increase in level of CDK4 complexed with p21CIP1/WAF1. Moreover, overexpression of cyclin D2 partially abrogated inhibition of Rb phosphorylation and G1 arrest in the hybridoma cells.