Molecular and cellular analyses of HLA class II-associated susceptibility to autoimmune diseases in the Japanese population

Abstract It is well known that individuals who are positive for particular HLA class II alleles show a high risk of developing autoimmune diseases. HLA class II molecules expressed on antigen-presenting cells present antigenic peptides to CD4(+) T cells. Their extensive polymorphism affects the structures of peptides bound to HLA class II molecules to create individual differences in immune responses to antigenic peptides. In order to gain a better understanding of mechanisms of the association between HLA class II alleles and susceptibility to autoimmune diseases, it is important to identify self-peptides presented by disease-susceptible HLA class II molecules and triggering disease-causative T cells. Many of the autoimmune diseases are observed in all ethnic groups, whereas the incidence of diseases, clinical manifestations and disease-susceptible HLA class II alleles are different among various ethnic groups for some autoimmune diseases. These phenomena suggest that differences in autoimmune self-peptide(s) in the context of disease-susceptible HLA class II molecules may cause these differences. Therefore, comparisons among disease-susceptible HLA class II alleles, autoantigenic peptides, and clinical manifestations of autoimmune diseases in different ethnic groups would be helpful in elucidating the pathogenesis of the diseases. In this review, we describe our recent findings on (1) the uniqueness of both clinical manifestations and the HLA-linked genetic background of Asian-type (opticospinal form) multiple sclerosis, (2) the characteristics of glutamic acid decarboxylase 65 (GAD65) or β2-glycoprotein I (β2-GPI) autoreactive T cells in Japanese patients with insulin-dependent diabetes mellitus (IDDM) or anti-β2-GPI antibody-associated autoimmunity, respectively, and (3) the generation of an efficient delivery system of peptides to the HLA class II-restricted antigen presentation path-way by utilizing a class II-associated invariant chain peptide (CLIP)-substituted invariant chain, which may be applicable to an evaluation of the "molecular mimicry hypothesis" for the activation of autoreactive T cells.

Acute toxicity and mutagenicity study on branched corn syrup and evaluation of its laxative effect in humans

We developed a branched corn syrup (BCS, average molecular weight: 500, content of indigestible portion: 45%) by heat treatment of indigestible dextrin with hydrochloric acid. To confirm the safety of BCS, we conducted both an acute toxicity test and a mutagenicity test. Moreover, we observed gastroenteric effects of BCS in fifty healthy humans. The results are summarized as follows. 1) There was no death observed after oral administration of BCS in Sprague-Dawley-strain rats. Lethal dose (LD)50, value was estimated to be more than 10 g/kg body weight. 2) No mutagenicity was observed in Salmonella typhimurium TA98, TA100, TA1535, TA1537, or Escherichia coli WP2uvrA. 3) Fifty adults were divided into five groups often (five of each sex) and orally administered BCS at 0.2, 0.3, 0.4. 0.5 and 0.6 g/kg body weight as indigestible portion. Although no diarrhea was observed in females, BCS at 0.6 g/kg as indigestible portion caused diarrhea in two out of five males. The maximum non-effective dose of indigestible portion of BCS was estimated to be 0.5 g/kg in males and more than 0.6 g/kg in females.

Congenital insensitivity to pain with anhidrosis (CIPA): effect of TRKA (NTRK1) missense mutations on autophosphorylation of the receptor tyrosine kinase for nerve growth factor

Human TRKA (NTRK1) encodes the receptor tyrosine kinases (RTKs) for nerve growth factor (NGF) and is the gene responsible for congenital insensitivity to pain with anhidrosis (CIPA), an autosomal recessive disorder characterized by a lack of pain sensation and anhidrosis. We reported 11 putative missense mutations in 31 CIPA families from various ethnic groups. Here we have introduced the corresponding mutations into the TRKA cDNA and examined NGF-stimulated autophosphorylation. We find that wild-type TRKA precursor proteins in a neuronal and a non-neuronal cell line were differentially processed and phosphorylated in an NGF-dependent and -independent manner, respectively. Two mutants (L93P and L213P) in the extracellular domain were aberrantly processed and showed diminished autophosphorylation in neuronal cells. Five mutants (G516R, G571R, R643W, R648C and G708S) in the tyrosine kinase domain were processed as wild-type TRKA but showed significantly diminished autophosphorylation in both neuronal and non-neuronal cells. In contrast, R85S and (H598Y; G607V), detected previously as double and triple mutations, are probably polymorphisms in a particular ethnic background. The other putative mutant D668Y might be a rare polymorphism or might impair the function of TRKA without compromising autophosphorylation. Mutated residues in the tyrosine kinase domain are conserved in various RTKs and probably contribute to critical function of these proteins. Thus, naturally occurring TRKA missense mutations with loss of function provide considerable insight into the structure-function relationship in the RTK family. Our data may aid in developing a drug which targets the clinically devastating 'complex regional pain syndrome'.

Fermi surface nesting and structural transition on a metal surface: In /Cu(001)

Peierls-type instability and structural phase transition are shown to occur on the surface of a normal metal. An In overlayer on Cu(001) undergoes a reversible transition at approximately 350 K. Scanning tunneling microscopy of the low-temperature, reduced-symmetry phase indicates a strong periodic lattice distortion (PLD). Angle-resolved photoemission of the high-temperature phase reveals that the In-derived surface resonance constitutes a square-shaped, quasi-two-dimensional Fermi surface within the projected bulk Cu bands. The Fermi surface exhibits one-dimensional nesting upon the transition, which is in agreement with the PLD periodicity.

Flow cytometric analysis of hemetopoietic progenitor cells in peripheral blood stem cell harvest from patients with CD34 positive acute leukemia

We analyzed CD34 positive cells in peripheral blood stem cell harvest (PBSCH) using flow cytometry. PBSCH from CD34 positive acute myelogeous leukemia (AML-M2) patient contained 1.87% CD34 positive cells, of which 1.21% was represented by MRD.PBSCH from CD34 positive acute lymphoblast leukemia (ALL) patient contained 3.14% CD34 positive cells, of which 0.11% was accounted for by minimal residual disease (MRD). If PBSCH from CD34 positive acute leukemia patient is analyzed for CD34 monoclonal antibody alone, the presence of CD34 positive MRD may escape attention so that CD34 positive hematopoietic progenitor cells may be overestimated. To avoid this risk, it is necessary to analyze PBSCH using both CD34 monoclonal antibody and characteristic markers of leukemia cells that were found pre-treatment.

[Perspectives on postgenome medicine: Inborn error of metabolism]

The news that human DNA structure will be completely analyzed in very near future does not mean the whole human genomes being clarified including own function and interaction between each gene. Concerning the diseases of inborn error of metabolism, we should clarify the implication of mutant gene, especially on non-cording regions, and genotype and phenotype relationship in each disease. Additional factors producing different phenotypes, even the same mutant gene being involved, such as environmental factors, modifier genes and SNPs in the affected gene are also the project of further discussion. Such information will be most useful for genetic counseling, and treatment and prevention of the diseases. New drugs designed by unique idea, gene therapy and therapy using hES cells should be developed for clinical practice, and for this purpose, fundamental research is indispensable.

Prevention of hepatic and peritoneal metastases by the angiogenesis inhibitor fr-118487 after removal of growing tumor in mice

We established a mouse rising dbl quote, left (low)primary tumor resection model" in which a transplanted tumor was resected after an orthotopic transplantation of colorectal cancer tissue to estimate the therapeutic effect of an angiogenesis inhibitor on metastasis. The angiogenesis inhibitor FR-118487 is a member of the fumagillin family. Here, 1 mg / kg / day of FR-118487 was subcutaneously administered to nude mice for 1 week, 2 weeks, or 4 weeks through an osmotic pump. Liver metastasis developed in 7 of 9 control mice, 2 of 6 mice that underwent the tumor resection 2 weeks after transplantation (early resection), and in all 7 of the mice that underwent the tumor resection 4 weeks after transplantation (late resection). In the short treatment trial, the FR-118487 administration immediately after the early resection completely inhibited both hepatic and peritoneal metastases, whereas its administration after the late resection had no effect on liver metastasis. In the prolonged treatment trial, inhibitory effects of prolonged treatment with FR-118487 on both hepatic and peritoneal metastases after the late resection were clearly demonstrated. The mice of the resection-alone group all died within 106 days after tumor inoculation, due to metastases of colon carcinoma. In contrast, half of the mice that underwent resection and then received antiangiogenic therapy were alive at the end of the observation period (160 days after transplantation). In conclusion, the combination of surgery and subsequent antiangiogenic therapy may be useful to prevent the distant metastasis of colorectal cancer and to improve the prognosis of patients with colorectal cancer.

Mutations in the 4-hydroxyphenylpyruvic acid dioxygenase gene are responsible for tyrosinemia type III and hawkinsinuria

The enzyme 4-hydroxyphenylpyruvic acid dioxygenase (HPD) catalyzes the reaction of 4-hydroxyphenylpyruvic acid to homogentisic acid in the tyrosine catabolism pathway. A deficiency in the catalytic activity of HPD may lead to tyrosinemia type III, an autosomal recessive disorder characterized by elevated levels of blood tyrosine and massive excretion of tyrosine derivatives into urine. It has been postulated that hawkinsinuria, an autosomal dominant disorder characterized by the excretion of 'hawkinsin,' may also be a result of HPD deficiency. Hawkinsin is a sulfur amino acid identified as (2-l-cystein-S-yl, 4-dihydroxycyclohex-5-en-1-yl)acetic acid. Patients with hawkinsinuria excrete this metabolite in their urine throughout their life, although symptoms of metabolic acidosis and tyrosinemia improve in the first year of life. We performed analyses of the HPD gene in a patient with tyrosinemia type III and two unrelated patients with hawkinsinuria. A homozygous missense mutation predicting an Ala to Val change at codon 268 (A268V) in the HPD gene was found in the patient with tyrosinemia type III. A heterozygous missense mutation predicting an Ala to Thr change at codon 33 (A33T) was found in the same HPD gene in the two patients with hawkinsinuria. These findings support the hypothesis that alterations in the structure and activity of HPD are causally related to two different metabolic disorders, tyrosinemia type III and hawkinsinuria.

[Arterial infusion chemotherapy for liver metastases from colorectal cancer--therapeutic effects of different protocols]

The therapeutic effects of different protocols for arterial infusion chemotherapy were compared in patients with multiple liver metastases from colorectal cancer. A total of 49 patients with colorectal multiple liver metastases treated in our hospital since 1988 were the subjects. In order to compare the therapeutic effects on the regression of cancer and the survival rate, the subjects were assigned into Groups A-D, which were treated using different protocols. Group A received ADR, EPI, CDDP or 5-FU alone at first. If this drug was not effective, it was replaced with another of those mentioned here, and so on. Group B received CDDP 50 mg on day 1, 5-FU 500 mg/day from day 2 to day 7 and 5-FU 500 mg/day for 2 weeks thereafter (FP treatment). Group C received CDDP 50 mg at the time of reservoir insertion and 5-FU 1,000 mg for 5 hours thereafter (WHF treatment). Group D received 5-FU 1,000 mg for 24 hours on day 1, day 3, and day 5 of every week with combination of CDDP 5-10 mg/day from day 1 to day 5 and none on day 6 and day 7 (intermittent F + low-dose P treatment) for 3 weeks. The response rate was 33% for Group A (n = 18), 46% for Group B (n = 13), 25% for Group C (n = 8) and 80% for Group D (n = 10), showing significant differences between Group D and other groups. The 1-year survival rate was 50% for Group A, 46% for Group B, 29% for Group C and 89% for Group D. Significant differences in survival rate were found between Group B and D, and Group C and D.

Frequency of Shiga toxin-producing Escherichia coli in cattle at a breeding farm and at a slaughterhouse in Japan

To investigate the frequency of Shiga toxin-producing Escherichia coli (STEC) infected calves at a breeding farm and cattle at a slaughterhouse in Tohoku area of Japan, the polymerase chain reaction (PCR) was used for detection of genes for Shiga toxin(s). The fecal samples from a total of 204 calves and 306 cattle were examined. The prevalence rates in calves less than 2 months of age, cattle 2-8 months of age, and adults greater than 1 year of age were 39.4, 78.9, and 40.8%, respectively. Detection frequency of STEC in the fecal specimens from calves aged 0-8 months was not different among the breeds of cattle (Holstein: H, Japanese black cattle: B, and F1: HxB). On the other hand, for calves over 12 months of age, the frequency of STEC in Japanese black cattle and F1 were significantly higher than in Holstein cattle. Serogroups of STEC usually identified in human cases of food poisoning (O157, O26, and O111) were not frequently found in the feces of the cattle.

Complete paternal uniparental isodisomy for chromosome 1 revealed by mutation analyses of the TRKA (NTRK1) gene encoding a receptor tyrosine kinase for nerve growth factor in a patient with congenital insensitivity to pain with anhidrosis

Uniparental disomy (UPD) is defined as the presence of a chromosome pair that derives from only one parent in a diploid individual. The human TRKA gene on chromosome 1q21-q22 encodes a receptor tyrosine kinase for nerve growth factor and is responsible for an autosomal recessive genetic disorder: congenital insensitivity to pain with anhidrosis (CIPA). We report here the second case of paternal UPD for chromosome 1 in a male patient with CIPA who developed normally at term and did not show overt dysmorphisms or malformations. He had only the usual features of CIPA with a homozygous mutation at the TRKA locus and a normal karyotype with no visible deletions or evidence of monosomy 1. Haplotype analysis of the TRKA locus and allelotype analyses of whole chromosome 1 revealed that the chromosome pair was exclusively derived from his father. Non-maternity was excluded by analyses of autosomes other than chromosome 1. Thus, we have identified a complete paternal isodisomy for chromosome 1 as the cause of reduction to homozygosity of the TRKA gene mutation, leading to CIPA. Our findings further support the idea that there are no paternally imprinted genes on chromosome 1 with a major effect on phenotype. UPD must be considered as a rare but possible cause of autosomal recessive disorders when conducting genetic testing.

Identification of a juxtamembrane segment of the glutamate receptor delta2 subunit required for the plasma membrane localization

Glutamate receptor delta2 subunit (GluRdelta2) is selectively expressed in cerebellar Purkinje cells and is specifically targeted to parallel fiber synapses, where GluRdelta2 plays important roles in synaptic plasticity, motor learning and synapse formation. Here, we investigated the mechanism of GluRdelta2 sorting using MDCK epithelial cells. Immunocytochemical analysis of subcellular localization showed that GluRdelta2 expressed in MDCK cells was predominantly distributed in the plasma membrane. By examining the subcellular localization of GluRdelta2 mutants with various deletions in the carboxyl-terminal cytoplasmic region, we identified J segment adjacent to transmembrane segment M4 as a key region for the efficient targeting of GluRdelta2 to the plasma membrane. On the other hand, the carboxyl terminus of GluRdelta2 essential for interaction with PDZ domain proteins was dispensable for the plasma membrane localization. Our results suggest that the juxtamembrane segment and the PDZ domain target site at the carboxyl terminus of GluRdelta2 play differential roles in plasma membrane targeting, synapse localization and signal transduction.

Detection of ornithine transcarbamylase deficiency heterozygotes by measuring of urinary uracil

The importance of detecting heterozygosity for X-linked ornithine transcarbamylase deficiency is well known. Although the DNA analysis and the allopurinol loading tests are commonly used for this purpose, both methods require complicated procedures. In order to establish a simple test for detecting female heterozygotes, we examined the uracil and orotic acid in single-voided urine samples from 70 healthy women, and from 12 asymptomatic females with ornithine transcarbamylase deficiency. Based on the results of healthy women, we were able to determine a screening cut-off line of 11.9 micromol/mmol creatinine (mean +/- 1SD in logarithmic form) for uracil. Using this cut-off line, the sensitivity of OCT heterozygotes was 100%. We were also able to establish a second cut-off line of 28.9 micromol/mmol creatinine (mean +/- 3SD in logarithmic form) for diagnosis. Using this second cut-off line, the specificity of OCT heterozygotes was 100%. Our study has shown that the measurement of urinary uracil is a relatively simple and effective method for detecting female heterozygotes.

New method for determining total dietary fiber by liquid chromatography

The molecular weight limit of water-soluble dietary fiber (SDF) determined by the Prosky method was studied by liquid chromatography (LC). It was confirmed that only SDF with an average degree of polymerization of 12 or higher can be determined by the Prosky method. Total dietary fiber (TDF) was determined by 2 additional methods using LC. In the first method, the total quantity of insoluble dietary fiber (IDF) and high molecular weight SDF (HMSDF) was determined according to the modified Prosky method (MES-TRIS buffer-based). The quantitatively collected final filtrate was analyzed by LC for the quantity of low molecular weight SDF (LMSDF), and the 2 quantities were totaled to obtain TDF. TDF values thus determined for rice, polished or unpolished, soybean flour, and pressed barley were higher than those determined by the Prosky method by approximately 6, 3.5, and 3.5%, respectively. In the second method, direct determination by LC analysis was done on samples after enzymatic treatment according to the Prosky method. Results showed that the determination of LMSDF, in particular, was highly accurate and more effective. In both of these methods, the quantity of LMSDF was determined from its chromatographic peak area ratio to glucose as an internal standard, which was produced by hydrolysis.

Statistical and mutational analysis of chronic granulomatous disease in Japan with special reference to gp91-phox and p22-phox deficiency

Chronic granulomatous disease (CGD) is a group of inherited disorders of host defense caused by a mutation in any of the four components of phagocyte NADPH oxidase, namely gp91-, p22-, p47-, and p67-phox. We have made a precise statistical analysis of 229 registered patients from 195 families in Japan and mutation analysis of 28 and 5 independent patients, respectively, with gp91- and p22-phox deficiency. The gp91- and p22-phox proteins form the membrane cytochrome b558, which plays important roles in the assembly of the active oxidase and electron-transfer reaction, and the lesions in either subunit account for more than 80% of cases. The ratio of male to female patients was 6.6/1, the incidence was calculated to be about 1 out of 220,000 birth, and the life expectancy of the patients born in the 1970s was estimated to be 25-30 years old. For the X-linked gp91-phox deficiency, we found five missense and nine nonsense mutations, seven deletions, three insertions, and four splice site mutations, which included the following novel mutations: four missense, five nonsense, six deletions, one insertion, and two splice site abnormalities. With regard to p22-phox deficiency, two homozygous nonsense mutations and one homozygous deletion, a missense mutation together with a splice site mutation, and two different missense mutations were found. These mutations have not been reported before. Based on the present and reported data from Japan, we discuss the molecular defects of the disease and the difference in statistics between western countries and Japan.

Mutation and polymorphism analysis of the TRKA (NTRK1) gene encoding a high-affinity receptor for nerve growth factor in congenital insensitivity to pain with anhidrosis (CIPA) families

The human TRKA gene encodes a high-affinity tyrosine kinase receptor for nerve growth factor. Congenital insensitivity to pain with anhidrosis (CIPA) is an autosomal recessive genetic disorder reported from various countries and characterized by anhidrosis (inability to sweat), the absence of reaction to noxious stimuli, and mental retardation. We have found that TRKA is the gene responsible for CIPA. We have studied TRKA in 46 CIPA chromosomes derived from 23 unrelated Japanese CIPA families. including three that have been previously reported, and identified 11 novel mutations. Four (L93P, G516R, R648 C, and D668Y) are missense mutations that result in amino acid substitutions at positions conserved in the TRK family, including TRKA, TRKB, and TRKC. Three (S131 fs, L579 fs, and D770 fs) are frameshift mutations. Three (E164X, Y359X, and R596X) are nonsense mutations. The other is an intronic branch-site (IVS7-33T-->A) mutation, causing aberrant splicing in vitro. We also report the characterization of eight intragenic polymorphic sites, including a variable dinucleotide repeat and seven single nucleotide polymorphisms, and describe the haplotypic associations of alleles at these sites in 106 normal chromosomes and 46 CIPA chromosomes. More than 50% of CIPA chromosomes share the frameshift mutation (R548 fs) that we described earlier. This mutation apparently shows linkage disequilibrium with a rare haplotype in normal chromosomes, strongly suggesting that it is a common founder mutation. These findings represent the first extensive analysis of CIPA mutations and associated intragenic polymorphisms; they should facilitate the detection of CIPA mutations and aid in the diagnosis and genetic counseling of this painless but severe genetic disorder with devastating complications.

Expression of Fas-Fas ligand in murine testis

PROBLEM

During spermatogenesis, it has been suggested that the number of germ cells to be matured is regulated and restricted through the apoptotic mechanism. In the present study, we investigated the expression and apoptotic role of Fas and Fas ligand (L) in the murine testis.

METHOD OF STUDY

The expression of Fas-FasL in the murine testis was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR)-Southern blot hybridization, in situ hybridization, and Western blot methods. The terminal deoxynucleotide transferase mediated dUTP-nick end label (TUNEL) and DNA fragmentation methods were applied to detect the generation of apoptosis in germ cells.

RESULTS

By means of RT-PCR-Southern blot hybridization, we demonstrated the positive expression of Fas in testicular germ cells, and of FasL in testicular cells. supporting the findings with in situ hybridization that Fas was localized in germ cells, whereas FasL was localized in Sertoli cells of murine testis. A specific band at 45 kDa was obtained in the lysates from testis and germ cells with Western blot analysis. Then, the co-incubation of germ cells with Spodoptera frugiperda (Sf9)-FasL cells in vitro resulted in the induction of apoptosis in germ cells detected by the TUNEL method. Furthermore, DNA fragmented ladders were also demonstrated in germ cells co-incubated with Sf9-FasL cells.

CONCLUSION

Fas-FasL system seemed to play an apoptotic role in spermatogenesis by the molecular interaction between FasL on Sertoli cells and Fas on germ cells.

Phylogenetic analysis of Pseudomonas syringae pathovars suggests the horizontal gene transfer of argK and the evolutionary stability of hrp gene cluster

Pseudomonas syringae are differentiated into approximately 50 pathovars with different plant pathogenicities and host specificities. To understand its pathogenicity differentiation and the evolutionary mechanisms of pathogenicity-related genes, phylogenetic analyses were conducted using 56 strains belonging to 19 pathovars. gyrB and rpoD were adopted as the index genes to determine the course of bacterial genome evolution, and hrpL and hrpS were selected as the representatives of the pathogenicity-related genes located on the genome (chromosome). Based on these data, NJ, MP, and ML phylogenetic trees were constructed, and thus 3 trees for each gene and 12 gene trees in total were obtained, all of which showed three distinct monophyletic groups: Groups 1, 2 and 3. The observation that the same set of OTUs constitute each group in all four genes suggests that these genes had not experienced any intergroup horizontal gene transfer within P. syringae but have been stable on and evolved along with the P. syringae genome. These four index genes were then compared with another pathogenicity-related gene, argK (the phaseolotoxin-resistant ornithine carbamoyltransferase gene, which exists within the argK-tox gene cluster). All 13 strains of pv. phaseolicola and pv. actinidiae used had been confirmed to produce phaseolotoxin and to have argK, whose sequences were completely identical, without a single synonymous substitution among the strains used (Sawada et al. 1997a). On the other hand, argK were not present on the genomes of the other 43 strains used other than pv. actinidiae and pv. phaseolicola. Thus, the productivity of phaseolotoxin and the possession of the argK gene were shown at only two points on the phylogenetic tree: Group 1 (pv. actinidiae) and Group 3 (pv. phaseolicola). A t test between these two pathovars for the synonymous distances of argK and the tandemly combined sequence of the four index genes showed a high significance, suggesting that the argK gene (or argK-tox gene cluster) experienced horizontal gene transfer and expanded its distribution over two pathovars after the pathovars had separated, thus showing a base substitution pattern extremely different from that of the noncluster region of the genome.

The long-term prognosis of congenital portosystemic venous shunt

Congenital portosystemic venous shunt (PSVS), considered to be a rare disease, can lead to hepatic encephalopathy (HE). With improvements in diagnostic imaging techniques, the number of infants and children with documented PSVS has increased. The natural course of the disease and indications for surgical closure of the shunt vessel have not been well defined. We reviewed 51 cases of congenital PSVS in Japan; 34 patients had an intrahepatic PSVS, and 17 had an extrahepatic PSVS. There were 12 patients with HE at the time of diagnosis. The frequency of HE increased in subjects over 60 years of age. Children with HE had a shunt ratio exceeding 60%. When the shunt ratio was less than 30%, HE did not occur. Twenty of 28 patients under the age of 15 years had hypergalactosemia at the time of neonatal screening. Part of the congenital intrahepatic PSVS spontaneously closed. Surgical closure of a PSVS may be an approach expected to prevent HE when the shunt ratio exceeds 60%.

Apoptotic cell death and caspase-3 activation induced by N-methyl-D-aspartate receptor antagonists and their prevention by insulin-like growth factor I

The effect of N-methyl-D-aspartate (NMDA) receptor antagonists on cell viability was studied in rat primary cortical cells. NMDA antagonists [MK-801 and 2-amino-5-phosphonovalerate (APV)] induced cell shrinkage, nuclear condensation or fragmentation, and internucleosomal DNA fragmentation. Treatment of cells with MK-801 (an NMDA antagonist) for 1-2 days induced apoptotic cell death in a dose-dependent manner (1 nM to 10 microM). NMDA (25 microM), however, inhibited the MK-801 (0.1 microM)-induced apoptotic cell death. MK-801 and APV decreased the concentration of intracellular calcium ion. Activation of caspase-3 was accompanied by MK-801-induced cell death in a dose-dependent manner, and an inhibitor of caspase-3 reduced the cell death. Further, cycloheximide (0.2 microg/ml) completely protected the cells from MK-801-induced apoptotic cell death and caspase-3 activation. Insulin-like growth factor I completely attenuated MK-801-induced apoptotic cell death and caspase-3 activation. These results demonstrated that the moderate NMDA receptor activation is probably involved in the survival signal of the neuron.

A heterozygous mutation of beta-actin associated with neutrophil dysfunction and recurrent infection

A human disorder caused by mutation in nonmuscle actin has not been reported. We report here a variant of nonmuscle actin in a female patient with recurrent infections, photosensitivity, and mental retardation. She also had abnormalities in neutrophil chemotaxis, superoxide production, and membrane potential response. Two-dimensional PAGE analysis of proteins from neutrophils and other cell types from this patient demonstrated a unique protein spot migrating at 42 kDa with pI shifted slightly to neutral relative to normal beta- and gamma-actin. Digestion peptide mapping and Western blotting showed this spot to be an abnormal actin. A full-length cDNA library was constructed by using mRNA from patient's cells and cDNA encoding the mutant beta-actin molecule was identified by an in vitro translation method. Sequencing of the clones demonstrated a G-1174 to A substitution, predicting a glutamic acid-364 to lysine substitution in beta-actin and eliminating a HinfI DNase restriction site found in normal beta-actin sequence. By HinfI digestion and by sequencing, the mutation in one allele of patient's genomic DNA was confirmed. Though no defect in cell-free polymerization of actin was detected, this defect lies in a domain important for binding to profilin and other actin-regulatory molecules. In fact, the mutant actin bound to profilin less efficiently than normal actin did. Heterozygous expression of mutant beta-actin in neutrophils and other cells of this patient may act in a dominant-negative fashion to adversely affect cellular activities dependent on the function of nonmuscle actin.

Short-chain acyl-CoA-dependent production of oxalate from oxaloacetate by Burkholderia glumae, a plant pathogen which causes grain rot and seedling rot of rice via the oxalate production

In Burkholderia glumae (formerly named Pseudomonas glumae), isolated as the causal agent of grain rot and seedling rot of rice, oxalate was produced from oxaloacetate in the presence of short-chain acyl-CoA such as acetyl-CoA and propionyl-CoA. Upon purification, the enzyme responsible was separated into two fractions (tentatively named fractions II and III), both of which were required for the acyl-CoA-dependent production of oxalate. In conjugation with the oxalate production from oxaloacetate catalyzed by fractions II and III, acetyl-CoA used as the acyl-CoA substrate was consumed and equivalent amounts of CoASH and acetoacetate were formed. The isotope incorporation pattern indicated that the two carbon atoms of oxalate are both derived from oxaloacetate, and among the four carbon atoms of acetoacetate two are from oxaloacetate and two from acetyl-CoA. When the reaction was carried out with fraction II alone, a decrease in acetyl-CoA and an equivalent level of net utilization of oxaloacetate were observed without appreciable formation of CoASH, acetoacetate or oxalate. It appears that in the oxalate production from oxaloacetate and acetyl-CoA, fraction II catalyzes condensation of the two substrates to form an intermediate which is split into oxalate and acetoacetate by fraction III being accompanied by the release of CoASH.