Association of dystrophin-related protein with dystrophin-associated proteins in mdx mouse muscle

Dystrophin is associated with a complex of muscle membrane (sarcolemmal) glycoproteins that provide a linkage to the extracellular matrix protein, laminin. The absence of dystrophin leads to a dramatic reduction of the dystrophin-associated proteins (156DAG, 59DAP, 50DAG, 43DAG and 35DAG) in the sarcolemma of patients with Duchenne muscular dystrophy and mdx mice. Here we demonstrate that dystrophin-related protein (DRP, utrophin), an autosomal homologue of dystrophin, is associated with an identical or antigenically similar complex of sarcolemmal proteins and that DRP and the dystrophin/DRP-associated proteins colocalize to the neuromuscular junction in Duchenne muscular dystrophy and mdx muscle. The DRP and dystrophin/DRP-associated proteins are found throughout the sarcolemma in small-calibre skeletal muscles and cardiac muscle of adult mdx mice. Because these muscles show minimal pathological changes, our results could provide a basis for the upregulation of DRP as a potential therapeutic approach.

An ancient retrotransposal insertion causes Fukuyama-type congenital muscular dystrophy

Fukuyama-type congenital muscular dystrophy (FCMD), one of the most common autosomal recessive disorders in Japan (incidence is 0.7-1.2 per 10,000 births), is characterized by congenital muscular dystrophy associated with brain malformation (micropolygria) due to a defect in the migration of neurons. We previously mapped the FCMD gene to a region of less than 100 kilobases which included the marker locus D9S2107 on chromosome 9q31. We have also described a haplotype that is shared by more than 80% of FCMD chromosomes, indicating that most chromosomes bearing the FCMD mutation could be derived from a single ancestor. Here we report that there is a retrotransposal insertion of tandemly repeated sequences within this candidate-gene interval in all FCMD chromosomes carrying the founder haplotype (87%). The inserted sequence is about 3 kilobases long and is located in the 3' untranslated region of a gene encoding a new 461-amino-acid protein. This gene is expressed in various tissues in normal individuals, but not in FCMD patients who carry the insertion. Two independent point mutations confirm that mutation of this gene is responsible for FCMD. The predicted protein, which we term fukutin, contains an amino-terminal signal sequence, which together with results from transfection experiments suggests that fukutin is a secreted protein. To our knowledge, FCMD is the first human disease to be caused by an ancient retrotransposal integration.

Structures of sialylated O-linked oligosaccharides of bovine peripheral nerve alpha-dystroglycan. The role of a novel O-mannosyl-type oligosaccharide in the binding of alpha-dystroglycan with laminin

alpha-Dystroglycan is a heavily glycosylated protein, which is localized on the Schwann cell membrane as well as the sarcolemma, and links the transmembrane protein beta-dystroglycan to laminin in the extracellular matrix. We have shown previously that sialidase treatment, but not N-glycanase treatment, of bovine peripheral nerve alpha-dystroglycan greatly reduces its binding activity to laminin, suggesting that the sialic acid of O-glycosidically-linked oligosaccharides may be essential for this binding. In this report, we analyzed the structures of the sialylated O-linked oligosaccharides of bovine peripheral nerve alpha-dystroglycan by two methods. O-Glycosidically-linked oligosaccharides were liberated by alkaline-borotritide treatment or by mild hydrazinolysis followed by 2-aminobenzamide-derivatization. Acidic fractions obtained by anion exchange column chromatography that eluted at a position corresponding to monosialylated oligosaccharides were converted to neutral oligosaccharides by exhaustive sialidase digestion. The sialidases from Arthrobacter ureafaciens and from Newcastle disease virus resulted in the same degree of hydrolysis. The neutral oligosaccharide fraction, thus obtained, gave a major peak with a mobility of 3.8-3.9 glucose units upon gel filtration, and its reducing terminus was identified as a mannose derivative. Based on the results of sequential exoglycosidase digestion, lectin column chromatography, and reversed-phase high-performance liquid chromatography, we concluded that the major sialylated O-glycosidically-linked oligosaccharide of the alpha-dystroglycan was a novel O-mannosyl-type oligosaccharide, the structure of which was Siaalpha2-3Galbeta1-4GlcNAcbeta1-2Man-Ser/Thr (where Sia is sialic acid). This oligosaccharide constituted at least 66% of the sialylated O-linked sugar chains. Furthermore, a laminin binding inhibition study suggested that the sialyl N-acetyllactosamine moiety of this sugar chain was involved in the interaction of the alpha-dystroglycan with laminin.

Dystrophin-related protein is localized to neuromuscular junctions of adult skeletal muscle

Dystrophin-related protein (DRP) is an autosomal gene product with high homology to dystrophin. We have used highly specific antibodies to the unique C-terminal peptide sequences of DRP and dystrophin to examine the subcellular localization and biochemical properties of DRP in adult skeletal muscle. DRP is enriched in isolated sarcolemma from control and mdx mouse muscle, but is much less abundant than dystrophin. Immunofluorescence microscopy localized DRP almost exclusively to the neuromuscular junction region in rabbit and mouse skeletal muscle, as well as mdx mouse muscle and denervated mouse muscle. DRP is also present in normal size and abundance and localizes to the neuromuscular junction region in muscle from the dystrophic mouse model dy/dy. Thus, DRP is a junction-specific membrane cytoskeletal protein that may play an important role in the organization of the postsynaptic membrane of the neuromuscular junction.

Deletion of fcgamma receptor IIB renders H-2(b) mice susceptible to collagen-induced arthritis

Autoimmune diseases, like rheumatoid arthritis, result from a dysregulation of the immune response culminating in hyperactivation of effector cells leading to immune-mediated injury. To maintain an appropriate immune response and prevent the emergence of autoimmune disease, activation signals must be regulated by inhibitory pathways. Biochemical and genetic studies indicate that the type IIB low-affinity receptor for immunoglobulin (Ig)G (FcgammaRIIB) inhibits cellular activation triggered through antibody or immune complexes and may be an important component in preventing the emergence of autoimmunity. To investigate the role of FcgammaRIIB in the development of type II collagen (CII)-induced arthritis (CIA), a model for rheumatoid arthritis in humans, we have examined its contribution in determining the susceptibility to CIA in the nonpermissive H-2(b) haplotype. H-2(b) mice immunized with bovine CII do not develop appreciable disease. In contrast, immunization of the FcgammaRIIB-deficient, H-2(b) mice with bovine CII induced CIA at an incidence of 42.2%. The maximal arthritis index of the FcgammaRIIB-deficient mice developing CIA (6.9 +/- 3.6) was comparable to that of DBA/1 mice (8.6 +/- 1.9), an H-2(q) strain susceptible for CIA induction. IgG1, IgG2a, and IgG2b antibody responses against CII were elevated in the FcgammaRIIB-deficient animals, especially in those mice showing arthritis, but less pronounced than DBA/1 mice. Histological examinations of the arthritic paws from FcgammaRIIB-deficient mice revealed that cartilage was destroyed and bone was focally eroded in association with marked lymphocyte and monocyte/macrophage infiltration, very similar to the pathologic findings observed in DBA/1 mice. These results indicate that a nonpermissive H-2(b) haplotype can be rendered permissive to CIA induction through deletion of FcgammaRIIB, suggesting that FcgammaRIIB plays a critical role in suppressing the induction of CIA.

New and reliable MRI diagnosis for progressive supranuclear palsy

OBJECTIVE

To evaluate the area of the midbrain and pons on mid-sagittal MRI in patients with progressive supranuclear palsy (PSP), Parkinson disease (PD), and multiple-system atrophy of the Parkinson type (MSA-P), compare these appearances and values with those of normal control subjects, and establish diagnostic MRI criteria for the diagnosis of PSP.

METHODS

The authors prospectively studied MRI of 21 patients with PSP, 23 patients with PD, 25 patients with MSA-P, and 31 age-matched normal control subjects. The areas of the midbrain tegmentum and the pons were measured on mid-sagittal MRI using the display tools of a workstation. The ratio of the area of the midbrain to the area of the pons was also evaluated in all subjects.

RESULTS

The average midbrain area of the patients with PSP (56.0 mm2) was significantly smaller than that of the patients with PD (103.0 mm2) and MSA-P (97.2 mm2) and that of the age-matched control group (117.7 mm2). The values of the area of the midbrain showed no overlap between patients with PSP and patients with PD or normal control subjects. However, patients with MSA-P showed some overlap of the values of individual areas with values from patients with PSP. The ratio of the area of the midbrain to the area of pons in the patients with PSP (0.124) was significantly smaller than that in those with PD (0.208) and MSA-P (0.266) and in normal control subjects (0.237). Use of the ratio allowed differentiation between the PSP group and the MSA-P group.

CONCLUSION

The area of the midbrain on mid-sagittal MRI can differentiate PSP from PD, MSA-P, and normal aging.

Endothelial cells of the rat brain vasculature express cyclooxygenase-2 mRNA in response to systemic interleukin-1 beta: a possible site of prostaglandin synthesis responsible for fever

We previously showed that intraperitoneal injection of lipopolysaccharide induced cyclooxygenase-2 (COX-2) mRNA in as yet unidentified cells of blood vessels and leptomeninges in the rat brain and proposed a possible role of these cells as the source of prostaglandin E2 in the genesis of fever (Cao et al., Brain Res., 697 (1995) 187-196). In the present study, to proceed further with this line of research, we addressed the following two questions: first, does a pyrogenic dose of interleukin-1 beta (IL-1 beta), an endogenous pyrogen, induce COX-2 mRNA in the brain blood vessels and leptomeninges? Secondly, if it does, what type of cells are positive for COX-2 mRNA? Intraperitoneal injection of recombinant human IL-1 beta (30 micrograms/kg) induced fever in rats and an in situ hybridization study revealed that faint but significant COX-2 mRNA signals appeared in the blood vessels and leptomeninges at 1.5 h after the injection (the early rising phase of fever). The mRNA signals increased in number and intensity at 4 h (early plateau phase), decreased at 6.5 h (early recovery phase), and completely disappeared by 10 h after the injection (late recovery phase). The COX-2 mRNA positive cells in the blood vessels were likely to be the endothelial cells since the corresponding cells in the adjacent mirror-imaged section also expressed mRNAs for intracellular adhesion molecule-1 and the type-I interleukin-1 receptor, although those in the leptomeninges still remained unidentified. These results imply that circulating IL-1 beta acts on its receptor on the endothelial cells of the brain vasculature to induce COX-2 mRNA, which is possibly responsible for the elevated level of PGE2 seen during fever.

Overexpression of dystrophin in transgenic mdx mice eliminates dystrophic symptoms without toxicity

Duchenne and Becker muscular dystrophy (DMD and BMD) are X-linked recessive diseases caused by defective expression of dystrophin. The mdx mouse, an animal model for DMD, has a mutation that eliminates expression of the 427K muscle and brain isoforms of dystrophin. Although these animals do not display overt muscle weakness or impaired movement, the diaphragm muscle of the mdx mouse is severely affected and shows progressive myofibre degeneration and fibrosis which closely resembles the human disease. Here we explore the feasibility of gene therapy for DMD by examining the potential of a full-length dystrophin transgene to correct dystrophic symptoms in mdx mice. We find that expression of dystrophin in muscles of transgenic mdx mice eliminates the morphological and immunohistological symptoms of muscular dystrophy. In addition, overexpression of dystrophin prevents the development of the abnormal mechanical properties associated with dystrophic muscle without causing deleterious side effects. Our results provide functional evidence for the feasibility of gene therapy for DMD.

Dystrophin-glycoprotein complex: its role in the molecular pathogenesis of muscular dystrophies

Dystrophin, the protein product of the Duchenne muscular dystrophy (DMD) gene, is associated with a large oligomeric complex of sarcolemmal glycoproteins, including dystroglycan which provides a linkage to the extracellular matrix component, laminin. In patients with DMD, the absence of dystrophin leads to the loss in all of the dystrophin-associated proteins, causing the disruption of the linkage between the subsarcolemmal cytoskeleton and the extracellular matrix. This may render the sarcolemma vulnerable to physical stress. These recent developments in the research concerning the function of the dystrophin-glycoprotein complex pave a way for the better understanding of the pathogenesis of muscular dystrophies.

The febrile response to lipopolysaccharide is blocked in cyclooxygenase-2(-/-), but not in cyclooxygenase-1(-/-) mice

Various lines of evidence have implicated inducible cyclooxygenase-2 (COX-2) in fever production. Thus, its expression is selectively enhanced in brain after peripheral exogenous (e.g., lipopolysaccharide [LPS]) or endogenous (e.g., interleukin-1) pyrogen administration, while selective COX-2 inhibitors suppress the fever induced by these pyrogens. In this study, we assessed the febrile response to LPS of congenitally constitutive COX-1 (COX-1-/-) and COX-2 (COX-2-/-)-deficient C57BL/6J-derived mice. COX-1+/- and COX-2+/- mice were also evaluated; controls were wild-type C57BL/6J mice (Jackson Labs.). All the animals were pretrained daily for two weeks to the experimental procedures. LPS was injected intraperitoneally at 1 microgram/mouse; pyrogen-free saline (PFS) was the vehicle and control solution. Core temperatures (Tcs) were recorded using thermocouples inserted 2 cm into the colon. The presence of the COX isoforms was determined in cerebral blood vessels immunocytochemically after the experiments, without knowledge of the functional results. The data showed that the wild-type, COX-1+/-, and COX-1-/- mice all responded to LPS with a 1 degrees C rise in Tc within 1 h; the fever gradually abated over the next 4 h. By contrast, COX-2+/- and COX-2-/- mice displayed no Tc rise after LPS. PFS did not affect the Tc of any animal. It would appear therefore that COX-2 is necessary for LPS-induced fever production.

Induction by lipopolysaccharide of cyclooxygenase-2 mRNA in rat brain; its possible role in the febrile response

Cyclooxygenase 2 (COX-2) is a newly discovered isoform of cyclooxygenase that is inducible by lipopolysaccharide (LPS) or cytokines. This enzyme is considered to play a major role in inflammatory processes by catalyzing the production of prostaglandins. In the present study, induction of COX-2 mRNA in the rat brain by intraperitoneal injection of LPS was studied by the in situ hybridization technique with special attention paid to timing and sites of induction along with the time course of fever. In situ hybridization was carried out on sections of rat brain, 1 h (latent phase), 2.5 h (maximally febrile phase), 4 h (plateau phase), and 7 h (recovery phase) after the LPS injection, as well as on those from the brains of untreated and saline-injected rats. Injection of LPS induced COX-2 mRNA in the brain in two different constituents: neuronal cells and non-parenchymal cells of the blood vessels and leptomeninges. Induction in the neuronal cells was restricted to some telencephalic areas where the COX-2 mRNA signal was also detected in control animals. The signal was maximally enhanced by 50 to 80% over the basal level 1 h after LPS injection. The COX-2 mRNA signal was hardly detectable in neuronal and glial cells in other brain regions, including the preoptic area, either in control or LPS-injected rats. Strong COX-2 mRNA signals, however, appeared in the inner surface of blood vessels and the leptomeninges over the entire brain, including the preoptic area and its vicinity. The signals were not detectable in the brains of control rats and were most intense in the brains of rats treated with LPS for 2.5 h or 4 h. These results demonstrate that two major cell groups in the brain, neuronal cells and non-parenchymal cells, are responsible for the enhanced production of prostaglandins after systemic LPS treatment. Considering the site and timing of induction, we propose a possible role for blood vessels and leptomeninges as the source of prostaglandin E2 in the genesis of fever.

Deficiency of the 50K dystrophin-associated glycoprotein in severe childhood autosomal recessive muscular dystrophy

X-linked recessive Duchenne muscular dystrophy (DMD) is caused by the absence of dystrophin, a membrane cytoskeletal protein. Dystrophin is associated with a large oligomeric complex of sarcolemmal glycoprotein. The dystrophin-glycoprotein complex has been proposed to span the sarcolemma to provide a link between the subsarcolemmal cytoskeleton and the extracellular matrix component, laminin. In DMD, the absence of dystrophin leads to a large reduction in all of the dystrophin-associated protein. We have investigated the possibility that a deficiency of a dystrophin-associated protein could be the cause of severe childhood autosomal recessive muscular dystrophy (SCARMD) with a DMD-like phenotype. Here we report the specific deficiency of the 50K dystrophin-associated glycoprotein (M(r) 50,000) in sarcolemma of SCARMD patients. Therefore, the loss of this glycoprotein is a common denominator of the pathological process leading to muscle cell necrosis in two forms of muscular dystrophy, DMD and SCARMD.

Duchenne muscular dystrophy: deficiency of dystrophin-associated proteins in the sarcolemma

Dystrophin, the protein product of the Duchenne muscular dystrophy (DMD) gene, is a major component of the subsarcolemmal cytoskeleton and exists in a large oligomeric complex tightly associated with several sarcolemmal glycoproteins which provide a linkage to the extracellular matrix protein, laminin. In the present study, we investigated the status of the dystrophin-associated proteins in the skeletal muscle from 17 DMD patients of various ages. The results revealed a dramatic reduction in all of the dystrophin-associated proteins in the sarcolemma of DMD muscle compared with normal muscle and muscle from a variety of other neuromuscular diseases. This abnormality was common in all 17 DMD patients, irrespective of age. Our results indicate that the absence of dystrophin leads to the loss in all of the dystrophin-associated proteins, which renders DMD muscle fibers susceptible to necrosis. The analysis of dystrophin-associated proteins is important in the assessment of experimental therapies that attempt to replace dystrophin in DMD muscle.

Immunomodulatory effects of ursodeoxycholic acid on immune responses

Ursodeoxycholic acid was recently recognized as an effective agent in the treatment of primary biliary cirrhosis. Experimental evidence supporting the usefulness of ursodeoxycholic acid as a potentially beneficial therapeutic agent for primary biliary cirrhosis has been reported from the biochemical and physiological aspects. In this study, we investigated the direct effects of ursodeoxycholic acid on immunoglobulin and cytokine production in vitro using plaque-forming cell assay and enzyme-linked immunosorbent assay. It was demonstrated that ursodeoxycholic acid suppressed the production of IgM, IgG and IgA induced by Staphylococcus aureus Cowan I in peripheral blood mononuclear cells derived from healthy subjects and patients with primary biliary cirrhosis and also in human B lymphoma cell lines. Furthermore, ursodeoxycholic acid suppressed interleukin-2 and interleukin-4 production induced by concanavalin A and interferon-gamma production induced by polyinosinic-polycytidylic acid, but it did not affect interleukin-1 and interleukin-6 production induced by lipopolysaccharide in peripheral blood mononuclear cells. In addition, ursodeoxycholic acid suppressed the concanavalin A-induced thymocyte proliferation mediated by interleukin-1. Cytotoxicity against lymphocytes was not observed at the concentrations of ursodeoxycholic acid used. These results suggest that the beneficial effect of ursodeoxycholic acid in primary biliary cirrhosis is mediated in part by immunosuppression.

Transcatheter arterial embolization of ruptured pseudoaneurysms with coils and n-butyl cyanoacrylate

PURPOSE

To evaluate the clinical efficacy of transcatheter arterial embolization with n-butyl cyanoacrylate (NBCA) for ruptured pseudoaneurysms, which are difficult to control by coil embolization alone.

MATERIALS AND METHODS

Ruptured pseudoaneurysms developed at the celiac trunk (n = 1), gastroduodenal artery (n = 2), pancreatic arcade (n = 1), hepatic artery (n = 3), renal artery (n = 1), and intercostal artery (n = 1) in nine patients. NBCA was mixed with iodized-oil (1:2) and injected via the 3-F microcatheter under fluoroscopic guidance, after the catheter was advanced close to the pseudoaneurysm. Coil embolization was performed to control blood flow before administration of NBCA in seven patients. NBCA was injected immediately after coil embolization in four patients. Embolization with NBCA was performed for recurrent bleeding that occurred within 1-21 days (mean, 10.7 days) after initial coil embolization in three patients. Two patients with peripheral pseudoaneurysms underwent embolization with NBCA alone.

RESULTS

The NBCA mixture was visible under fluoroscopy, and was useful in monitoring the embolization process and deciding the endpoint. Embolization was technically successful without major complications in all patients. Pseudoaneurysms and afferent and efferent arteries were eliminated immediately after embolization. Bleeding was stopped after embolization in all cases. Rebleeding did not occur in any patient during their follow-up periods of 0.7-69.5 months (mean, 17.9 months).

CONCLUSION

Embolization with NBCA is a feasible and useful treatment for ruptured pseudoaneurysms, which are difficult to control by coil embolization alone.

Progression of myocardial necrosis during reperfusion of ischemic myocardium

BACKGROUND

The occurrence of myocyte necrosis during reperfusion of ischemic myocardium is controversial. This study measured myocardial 2-deoxyglucose uptake, correlated with histology, to determine whether loss of viability occurred during reperfusion of ischemic myocardium.

METHODS AND RESULTS

In 12 anesthetized dogs, the left anterior descending coronary artery was occluded for 90 minutes before 4 hours reperfusion. Myocardial blood flow was measured by microspheres and the tracers 14C-2-deoxyglucose and 18F-2-deoxyglucose were injected intravenously after 5 and 180 minutes of reperfusion, respectively. After 240 minutes, the heart was stained with thioflavin-S (size of no-reflow zone) and triphenyl-tetrazolium chloride (TTC, extent of necrosis). Samples from normal, salvaged, and necrotic myocardium were counted for 14C- and 18F-deoxyglucose and microspheres. With the use of a three-compartment model of 2-deoxyglucose uptake, the rate constant k3 for phosphorylation of 14C- and 18F-2-deoxyglucose was calculated for each sample. Viability was defined as k3> or = 0.125 min(-1) (predictive accuracy 88% versus electron microscopy and 97% versus TTC). Among 58 samples from no-reflow regions, 97% were nonviable after 5 minutes of reperfusion (k3=0.096 +/- 0.027 min[-1]). Among 164 samples from salvaged myocardium, 95% were viable after both 5 and 180 minutes of reperfusion (k3=0.170 +/- 0.056 min[-1] P<.01 versus no-reflow). Among 179 samples from infarcted myocardium, mean k3 after 5 minutes of reperfusion was 0.184 +/- 0.070 min(-1) and 65% of samples were viable, but after 180 minutes of reperfusion mean k3 had decreased to 0.077 +/- 0.032 min(-1) (P<.0001) and 98% of samples were nonviable.

CONCLUSIONS

A large proportion of samples from infarcted myocardium are viable at the end of the ischemic period but lose viability during the first hours of reperfusion.

Relationship between labeling indices of Ki-67 and BrdUrd in human malignant tumors

The relationship between labeling indices of Ki-67 reactive antigen expressed by cycling cells and BrdUrd incorporated into S-phase cells was investigated in 20 patients with malignant tumors. Both of the labeling indices varied greatly from patient to patient; the labeling index of Ki-67 ranged from 37.5% to 1.9% with an average value of 16%, and the BrdUrd labeling index ranged from 23.4% to 1.6% with an average of 9.3%. The Ki-67 labeling index was higher than the BrdUrd labeling index. In general, the values of the Ki-67 labeling index were parallel to those of the BrdUrd labeling index, and the relation Y = 1.59X + 1.15 (r = 0.89) was obtained. In human solid tumors, therefore, the growth fraction can be easily estimated from the S-phase fraction size, and vice versa.

Conjugated linoleic acid accumulation via 10-hydroxy-12-octadecaenoic acid during microaerobic transformation of linoleic acid by Lactobacillus acidophilus

Specific isomers of conjugated linoleic acid (CLA), a fatty acid with potentially beneficial physiological and anticarcinogenic effects, were efficiently produced from linoleic acid by washed cells of Lactobacillus acidophilus AKU 1137 under microaerobic conditions, and the metabolic pathway of CLA production from linoleic acid is explained for the first time. The CLA isomers produced were identified as cis-9, trans-11- or trans-9, cis-11-octadecadienoic acid and trans-9, trans-11-octadecadienoic acid. Preceding the production of CLA, hydroxy fatty acids identified as 10-hydroxy-cis-12-octadecaenoic acid and 10-hydroxy-trans-12-octadecaenoic acid had accumulated. The isolated 10-hydroxy-cis-12-octadecaenoic acid was transformed into CLA during incubation with washed cells of L. acidophilus, suggesting that this hydroxy fatty acid is one of the intermediates of CLA production from linoleic acid. The washed cells of L. acidophilus producing high levels of CLA were obtained by cultivation in a medium containing linoleic acid, indicating that the enzyme system for CLA production is induced by linoleic acid. After 4 days of reaction with these washed cells, more than 95% of the added linoleic acid (5 mg/ml) was transformed into CLA, and the CLA content in total fatty acids recovered exceeded 80% (wt/wt). Almost all of the CLA produced was in the cells or was associated with the cells as free fatty acid.

Identification of the prfC gene, which encodes peptide-chain-release factor 3 of Escherichia coli

The termination of protein synthesis in bacteria requires two codon-specific polypeptide release factors, RF-1 and RF-2. A third factor, RF-3, which stimulates the RF-1 and RF-2 activities, was originally identified in Escherichia coli, but it has received little attention since the 1970s. To search for the gene encoding RF-3, we selected nonsense-suppressor mutations by random insertion mutagenesis on the assumption that a loss of function of RF-3 would lead to misreading of stop signals. One of these mutations, named tos-1 (for transposon-induced opal suppressor), mapped to the 99.2 min region on the E. coli chromosome and suppressed all three stop codons. Complementation studies and analyses of the DNA and protein sequences revealed that the tos gene encodes a 59,442-Da protein, with sequence homology to elongation factor EF-G, including G-domain motifs, and that the tos-1 insertion eliminated the C-terminal one-fifth of the protein. Extracts containing the overproduced Tos protein markedly increased the formation of ribosomal termination complexes and stimulated the RF-1 or RF-2 activity in the codon-dependent in vitro termination assay. The stimulation was significantly reduced by GTP, GDP, and the beta,gamma-methylene analog of GTP, but not by GMP. These results fit perfectly with those described in the original publications on RF-3, and the tos gene has therefore been designated prfC. A completely null prfC mutation made by reverse genetics affected the cell growth under the limited set of physiological and strain conditions.

Generation of dendritic cells and macrophages from human induced pluripotent stem cells aiming at cell therapy

This report describes generation of dendritic cells (DCs) and macrophages from human induced pluripotent stem (iPS) cells. iPS cell-derived DC (iPS-DC) exhibited the morphology of typical DC and function of T-cell stimulation and antigen presentation. iPS-DC loaded with cytomegalovirus (CMV) peptide induced vigorous expansion of CMV-specific autologous CD8+ T cells. Macrophages (iPS-MP) with activity of zymosan phagocytosis and C5a-induced chemotaxis were also generated from iPS cells. Genetically modified iPS-MPs were generated by the introduction of expression vectors into undifferentiated iPS cells, isolation of transfectant iPS cell clone and subsequent differentiation. By this procedure, we generated iPS-MP expressing a membrane-bound form of single chain antibody (scFv) specific to amyloid β (Aβ), the causal protein of Alzheimer's disease. The scFv-transfectant iPS-MP exhibited efficient Aβ-specific phagocytosis activity. iPS-MP expressing CD20-specific scFv engulfed and killed BALL-1 B-cell leukemia cells. Anti-BALL-1 effect of iPS-MP in vivo was demonstrated in a xeno-transplantation model using severe combined immunodeficient mice. In addition, we established a xeno-free culture protocol to generate iPS-DC and iPS-MP. Collectively, we demonstrated the possibility of application of iPS-DC and macrophages to cell therapy.

Dystroglycan is a binding protein of laminin and merosin in peripheral nerve

alpha-Dystroglycan, a 156 kDa dystrophin-associated glycoprotein, binds laminin in skeletal muscle. Here we demonstrate that alpha-dystroglycan is a binding protein of laminin (A/B1/B2) and merosin (M/B1/B2) in peripheral nerve. Immunocytochemical analysis demonstrates the localization of alpha-dystroglycan and merosin surrounding myelin sheath of peripheral nerve fibers. Biochemical analysis demonstrates that the 120 kDa peripheral nerve alpha-dystroglycan binds merosin as well as laminin. The binding of laminin and merosin is Ca2+ dependent and is inhibited by NaCl and heparin. Recently, merosin was shown to be deficient in the peripheral nerve of dy mice which have defects in myelination. The interaction between alpha-dystroglycan and merosin may play a role in the regulation of Schwann cell myelination and/or maintenance of myelin sheath.

Processing of beta-dystroglycan by matrix metalloproteinase disrupts the link between the extracellular matrix and cell membrane via the dystroglycan complex

The dystroglycan complex is a membrane-spanning complex composed of two subunits, alpha- and beta-dystroglycan. alpha-dystroglycan is a cell surface peripheral membrane protein which binds to the extracellular matrix (ECM), whereas beta-dystroglycan is an integral membrane protein which anchors alpha-dystroglycan to the cell membrane. The dystroglycan complex provides a tight link between the ECM and cell membrane. Dysfunction of the dystroglycan complex has commonly been implicated in the molecular pathogenesis of severe forms of hereditary neuromuscular diseases, including Duchenne muscular dystrophy, Fukuyama-type congenital muscular dystrophy and sarcoglycanopathy (LGMD2C, -D, -E and -F). To begin to clarify the pathway by which the dysfunction of the dystroglycan complex could lead to muscle cell degeneration, we investigated the proteolytic processing of the dystroglycan complex in this study. We demonstrate that (i) a 30 kDa fragment of beta-dystroglycan is expressed in peripheral nerve, kidney, lung and smooth muscle, but not skeletal muscle, cardiac muscle or brain, and (ii) this fragment is the product of proteolytic processing of the extracellular domain of beta-dystroglycan by the membrane-associated matrix metalloproteinase (MMP) activity. Importantly, furthermore, we demonstrate that this processing disintegrates the dystroglycan complex. Our results indicate that the processing of beta-dystroglycan by MMP causes the disruption of the link between the ECM and cell membrane via the dystroglycan complex, which could have profound effects on cell viability. Based on these and previously reported findings, we propose a hypothesis that this processing may play a crucial role in the molecular pathogenesis of sarcoglycanopathy.