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N Tanahashi

Publications and source records attributed to N Tanahashi.

At least 19 recordsLinked to original sources
PubMed2000

Hybrid proteasomes. Induction by interferon-gamma and contribution to ATP-dependent proteolysis.

Eukaryotic cells contain various types of proteasomes. Core 20 S proteasomes (abbreviated 20 S below) have two binding sites for the regulatory particles, PA700 and PA28. PA700-20 S-PA700 complexes are known as 26 S proteasomes and are ATP-dependent machines that degrade cell proteins. PA28 is found both in previously described complexes of the type PA28-20 S-PA28 and in complexes that also contain PA700, as PA700-20 S-PA28. We refer to the latter as "hybrid proteasomes." The relative amounts of the various types of proteasomes in HeLa extracts were determined by a combination of immunoprecipitation and immunoblotting. Hybrid proteasomes accounted for about a fourth of all proteasomes in the extracts. Association of PA28 and proteasomes proved to be ATP-dependent. Hybrid proteasomes catalyzed ATP-dependent degradation of ornithine decarboxylase (ODC) without ubiquitinylation, as do 26 S proteasomes. In contrast, the homo-PA28 complex (PA28-20 S-PA28) was incapable of degrading ODC. Intriguingly, a major immunomodulatory cytokine, interferon-gamma, appreciably enhanced the ODC degradation in HeLa and SW620 cells through induction of the hybrid proteasome, which may also be responsible for the immunological processing of intracellular antigens. Taken together, we report here for the first time the existence of two types of ATP-dependent proteases, the 26 S proteasome and the hybrid proteasome, which appear to share the ATP-dependent proteolytic pathway in mammalian cells.

Adenosine Triphosphate↗
PubMed2000

A critical role for the proteasome activator PA28 in the Hsp90-dependent protein refolding.

The 90-kDa heat shock protein, Hsp90, was previously shown to capture firefly luciferase during thermal inactivation and prevent it from undergoing an irreversible off-pathway aggregation, thereby maintaining it in a folding-competent state. While Hsp90 by itself was not sufficient to refold the denatured luciferase, addition of rabbit reticulocyte lysate remarkably restored the luciferase activity. Here we demonstrate that Hsc70, Hsp40, and the 20 S proteasome activator PA28 are the effective components in reticulocyte lysate. Purified Hsc70, Hsp40, and PA28 were necessary and sufficient to fully reconstitute Hsp90-initiated refolding. Kinetics of substrate binding support the idea that PA28 acts as the molecular link between the Hsp90-dependent capture of unfolded proteins and the Hsc70- and ATP-dependent refolding process.

Amino Acid Sequence↗
PubMed2000

Nob1p, a new essential protein, associates with the 26S proteasome of growing saccharomyces cerevisiae cells.

Nob1p, which interacts with Nin1p/Rpn12, a subunit of the 19S regulatory particle (RP) of the yeast 26S proteasome, has been identified by two-hybrid screening. NOB1 was found to be an essential gene, encoding a protein of 459 amino acid residues. Nob1p was detected in growing cells but not in cells in the stationary phase. During the transition to the stationary phase, Nob1p was degraded, at least in part, by the 26S proteasome. Nob1p was found only in proteasomal fractions in a glycerol gradient centrifugation profile and immuno-coprecipitated with Rpt1, which is an ATPase component of the yeast proteasomes. These results suggest that association of Nob1p with the proteasomes is essential for the function of the proteasomes in growing cells.

Carrier Proteins↗
PubMed2000

Degradation of ornithine decarboxylase by the 26S proteasome.

Ornithine decarboxylase (ODC) is a key enzyme in polyamine biosynthesis. Turnover of ODC is extremely rapid and highly regulated, and is accelerated when polyamine levels increase. Polyamine-stimulated ODC degradation is mediated by association with antizyme (AZ), an ODC inhibitory protein induced by polyamines. ODC, in association with AZ, is degraded by the 26S proteasome in an ATP-dependent, but ubiquitin-independent, manner. The 26S proteasome irreversibly inactivates ODC prior to its degradation. The inactivation, possibly due to unfolding, is coupled to sequestration of ODC within the 26S proteasome. This process requires AZ and ATP, but not proteolytic activity of the 26S proteasome. The carboxyl-terminal region of ODC presumably exposed by interaction with AZ plays a critical role for being trapped by the 26S proteasome. Thus, the degradation pathway of ODC proceeds as a sequence of multiple distinct processes, including recognition, sequestration, unfolding, translocation, and ultimate degradation mediated by the 26S proteasome.

Animals↗
PubMed2000

Association between platelet glycoprotein Ibalpha genotype and ischemic cerebrovascular disease.

BACKGROUND AND PURPOSE: Platelets play pivotal roles in the development of ischemic cerebrovascular disease (CVD). The platelet glycoprotein (GP) Ib/IX/V complex is a receptor for von Willebrand factor, which plays a major role in the initial phase of platelet activation under high shear stress conditions. This study was designed to investigate the association between a genetic variation of this receptor and the prevalence of CVD. METHODS: Two hundred patients with ischemic CVD, as confirmed by brain CT and/or MRI, and 317 age- and sex-matched control subjects without clinical evidence of CVD or cardiovascular disease were analyzed for their genotype frequencies of the (145)Thr/Met dimorphism of the alpha-chain of GPIb (GPIbalpha). RESULTS: Genotypes with (145)Met (T/M and M/M) were more frequently found in the CVD patients (26.5%) than in control subjects (14.2%, P=0.0005). The genotype effect was more obvious in those <60 years of age or without acquired cardiovascular risk factors. The odds ratio for nonsmoking women <60 years of age was 10. 6 (95% confidence intervals, 2.2 to 51.7). Although the number of patients studied was small (n=24), transient ischemic attack showed the highest odds ratio (4.3, P=0.0004), followed by lacunar infarction (OR=2.2, P=0.0024) and atherothrombotic infarction (OR=1. 5, P=0.3143). Logistic regression analysis revealed that the presence of Met-allele was independently associated with CVD. CONCLUSIONS: Our study suggests that the platelet GPIbalpha genotype is a genetic risk factor for ischemic CVD.

Alleles↗
PubMed2000

C242T polymorphism of NADPH oxidase p22 PHOX gene and ischemic cerebrovascular disease in the Japanese population.

BACKGROUND AND PURPOSE: Superoxide has been implicated in the pathogenesis of ischemic stroke and atherosclerosis. NADPH oxidase, a major source of superoxide generation in neutrophils and the vascular system, plays a critical role in ischemic injury and atherogenesis. Recently, an association between the C242T polymorphism of p22 PHOX, an essential component of NADPH oxidase, and coronary artery disease (CAD) has been reported in several studies. To investigate the relationship between the C242T polymorphism of p22 PHOX and ischemic cerebrovascular disease (CVD), we conducted a case-control study. METHODS: We recruited 226 CVD patients (atherothrombotic infarction, lacunar infarction, and transient ischemic attack) and 301 control subjects and analyzed C242T polymorphism of p22 PHOX by detection of restriction fragment length polymorphism. RESULTS: The TC+TT genotype frequencies in the CVD group and control group were 21.7% and 13.3%, respectively, and the prevalence of the TC+TT genotype was significantly higher in the CVD patients (chi(2)=6.477, P=0.01, OR 1.81, 95% CI 1.15 to 2.86). Analysis by CVD subtypes showed that the OR for the TC+TT genotype was higher in the CVD patients with atherothrombotic infarction than in those with lacunar infarction and transient ischemic attack. CONCLUSIONS: The C242T polymorphism of the NADPH oxidase p22 PHOX gene is a novel pathogenetic risk factor for CVD.

Asian People↗
PubMed1999

Platelet adhesion to human brain microvascular endothelial cells in vitro. Observation with video-enhanced contrast microscopy.

Employing video-enhanced contrast (VEC) microscopy and perfusion systems, we examined whether platelets adhere directly to human brain microvascular endothelial cells (HBEC) in vitro after thrombin treatment and whether adenosine diphosphate (ADP) or thromboxane A2-stimulated platelets adhere directly to HBEC at a low flow state in vitro. HBECs were cultured on a coverglass and put in the observation chamber of VEC microscopy. Following pretreatment with human alpha-thrombin 1.0 units/ml (n = 8) for 20 min, thrombin was thoroughly washed out. Platelet rich plasma (PRP) was perfused over HBEC at a low shear rate of 10 s(-1) for 30 min. Platelets adhered directly to thrombin-treated HBEC. Activated platelets by ADP (2 microM, n = 8) or thromboxane A2 (U-46619 10 microM, n = 5) were perfused over HBEC for 30 min and washed out. Platelets also adhered directly to HBEC. However, platelets did not adhere to HBEC when PRP only (n = 6) was perfused over HBEC for 30 min and washed out. Platelet adhesion directly to HBEC following thrombin treatment or platelet activation may play a pivotal role in secondary thrombus formation and microcirculatory disturbance in the ischemic brain.

Adenosine Diphosphate↗
PubMed1999

Pathologic findings of silent hyperintense white matter lesions on MRI.

The pathologic features of silent hyperintense white matter lesions in T2-weighted images on MRI were studied in patients with no neurologic signs or symptoms. The small patchy hyperintense white matter lesions represented myelin pallor associated with vessels showing hypertension and arteriosclerotic changes. 'Caps' also showed myelin pallor with dilated perivascular spaces. There were no lacunar infarcts in these lesions. Some of 'caps' was shown to be elongated normal lateral ventricle. 'Rims' of early stage revealed subependymal gliosis that was a part of normal aging processes.

Aged↗
PubMed1999

Transient vasodilatory effects of adrenomedullin on cerebral parenchymal microvessels in cats.

We studied the effects of adrenomedullin, structural homology of calcitonin gene-related peptide (CGRP), on the cerebral parenchymal microvessels in cats by our photoelectric method. Adrenomedullin significantly increased cerebral blood volume (CBV) at 0.5 and 1 min after intracarotid injection (0.01-1 nmol/kg, maximum; +0.71 vol% for 0.1 nmol/kg adrenomedullin). Adrenomedullin antagonist, adrenomedullin22-62 (0.01-10 nmol/kg), caused no significant changes in CBV and mean arterial blood pressure. Preinjection of 10 nmol/kg adrenomedullin22-52 blocked the vasodilatory effect of 0.01 nmol/kg adrenomedullin (P < 0.05). Pretreatment of 1 nmol/kg CGRP8-37, which has antagonistic activity against CGRP, also inhibited the vasodilatation of adrenomedullin. The degree of CBV reduction after adrenomedullin22-52 injection was greater than that after CGRP8-37 injection. Adrenomedullin has no major role in the maintenance of resting tone of intracerebral parenchymal vessels. Intravascularly administered adrenomedullin dilates cortical microvessels mainly through the specific adrenomedullin receptor.

Adrenomedullin↗
PubMed1999

The proteasome-dependent proteolytic system.

The 20S proteasome is an intriguingly large complex that acts as a proteolytic catalytic machine. Accumulating evidence indicates the existence of multiple factors capable of regulating the proteasome function. They are classified into two different categories, one type of regulator is PA700 or PA28 that is reversibly associated with the 20S proteasome to form enzymatically active proteasomes and the other type including a 300-kDa modulator and PI31 indirectly influences proteasome activity perhaps by promoting or suppressing the assembly of the 20S proteasome with PA700 or PA28. Thus, there have been documented two types of proteasomes composed of a core catalytic proteasome and a pair of symmetrically disposed PA700 or PA28 regulatory particle. Moreover, the recently-identified proteasome containing both PA28 and PA700 appears to play a significant role in the ATP-dependent proteolytic pathway in cells, as can the 26S proteasome which is known as a eukaryotic ATP-dependent protease.

Adenosine Triphosphatases↗
PubMed1999

ATP-Dependent inactivation and sequestration of ornithine decarboxylase by the 26S proteasome are prerequisites for degradation.

The 26S proteasome is a eukaryotic ATP-dependent protease, but the molecular basis of its energy requirement is largely unknown. Ornithine decarboxylase (ODC) is the only known enzyme to be degraded by the 26S proteasome without ubiquitinylation. We report here that the 26S proteasome is responsible for the irreversible inactivation coupled to sequestration of ODC, a process requiring ATP and antizyme (AZ) but not proteolytic activity. Neither the 20S proteasome (catalytic core) nor PA700 (the regulatory complex) by itself contributed to this ODC inactivation. Analysis with a C-terminal mutant ODC revealed that the 26S proteasome recognizes the C-terminal degradation signal of ODC exposed by attachment of AZ, and subsequent ATP-dependent sequestration of ODC in the 26S proteasome causes irreversible inactivation, possibly unfolding, of ODC and dissociation of AZ. These processes may be linked to the translocation of ODC into the 20S proteasomal inner cavity, centralized within the 26S proteasome, for degradation.

Adenosine Triphosphate↗
PubMed1999

Pathologic findings of silent, small hyperintense foci in the basal ganglia and thalamus on MRI.

We analyzed the pathologic features of silent, small hyperintense foci in the basal ganglia and thalamus on MRI T2-weighted images (T2WI). Eight foci were histologically lacunar infarcts (LI), and 21 were dilated perivascular spaces (DPS). The foci with smooth margins were mostly DPS, whereas those with irregular margins were mostly LI (p = 0.018). Most putaminal foci were DPS, whereas most thalamic foci were LI (p = 0.001). The mean areas of LI and DPS overlapped below 19.6 mm2. The shape and site of hyperintense foci on T2WI are important for differentiating LI from DPS.

Aged↗
PubMed1998

Contribution of proline residue for efficient production of MHC class I ligands by proteasomes.

Proteasomes are processing enzymes capable of generating major histocompatibility complex (MHC) class I ligands, but the mechanism of how they excise ligands without destroying them is largely unknown. Previously, we reported that most products of ornithine decarboxylase degraded in vitro by the 26 S ATP-dependent proteasome, which contained one or two Pro residues (Tokunaga, F., Goto, T., Koide, T., Murakami, Y., Hayashi, S., Tamura, T., Tanaka, K., and Ichihara, A. (1994) J. Biol. Chem. 269,17382-17385), which implied that the Pro residue has a role in the escape from random cleavage by proteasomes. Here, we examine the role of the Pro residue in producing MHC class I ligands in vitro. Proteasomes generated two cytotoxic T lymphocyte-epitopic precursor peptides, SIIPGLPLSL and DMYPHFMPTNL, from the 29-mer and 25-mer peptides harboring these sequences, which are derived from the c-akt proto-oncogene and the pp89 protein of mouse cytomagalovirus, respectively. Replacement of the first or second Pro residue within these epitopes by Ala resulted in a marked reduction of this epitope-derived production or their random cleavage by proteasomes, irrespective of the presence of PA28, which greatly accelerates the generation of unmodified ligands. Moreover, replacement of a single amino acid residue other than Pro in both epitopic and flanking regions by Ala or Leu had no or little appreciable effect on the SIIPGLPLSL or its derivative production. Thus, Pro residue(s) within these epitopic sequences presumably contributes to efficient production of MHC class I ligands through prevention of their random cleavage by proteasomes.

Amino Acid Sequence↗
PubMed1998

Platelet adhesion to aortic endothelial cells in vitro after thrombin treatment: observation with video-enhanced contrast microscopy.

Secondary thrombus formation following arterial occlusion is suggested to play an important role in the exacerbation of ischemic organ damage. We investigated the effect of thrombin on endothelial cells from the aspect of morphological changes and induction of platelet adhesion to the endothelial cells. Using a video-enhanced contrast microscopy, we observed human aortic endothelial cells (HAEC) following perfusion of human alpha-thrombin of 1.0 U/ml (n = 7) or vehicle (n = 7) for 30 minutes. The endothelial cells began to shrink 15 minutes after thrombin administration. Gaps between the cells were formed. The cells became rearranged orderly in the same direction 30 minutes later. In another study, following pretreatment with human alpha-thrombin 1.0 U/ml (n = 10) or vehicle (n = 7) for 20 minutes and washout, platelets were perfused over HAEC for 30 minutes. Platelets adhered directly to thrombin-treated endothelial cells and became flat on the endothelial cells. Then other platelets were observed to approach to the flattened platelets and aggregated onto it. After washout of floating platelets, adhesion of platelets was further confirmed. These results suggest that thrombin may be involved in the endothelial damage and formation of platelet thrombi on the endothelial cells after blood flow disturbance.

Aorta↗
PubMed1998

cDNA cloning and characterization of a human proteasomal modulator subunit, p27 (PSMD9).

We have employed cDNA cloning to deduce the complete primary structure of a new subunit, designated p27, of the modulator trimer complex that stimulates the association of the PA700 regulator with the catalytic 20S proteasome to form the ATP-dependent active 26S proteasome. We found two distinct cDNAs encoding two highly homologous proteins except in the C-terminal region, which are termed tentatively p27-1 and p27-2. The short p27-2 cDNA has a deletion of 65 bp near the 3'-end region of the long p27-1 cDNA, which encodes a large protein with an extended C-terminal region, designated p27-L, whereas the long p27-1 cDNA encodes a small protein named p27-S. The polypeptides of p27-L and p27-S consist of 223 and 209 amino acid residues with calculated molecular masses of 24,852 and 22,764 and isoelectric points of 6.50 and 5.28, respectively. Immunoblot analysis with anti-p27 antibody revealed that p27, together with two other ATPase components, TBP1 and p42, was associated with not only the modulator complex but also significantly with the 26S proteasome complex, suggesting that the three are common/sharing subunits in these two complexes. By the fluorescence in situ hybridization method, the p27 (PSMD9) gene was mapped to the q24.2-q24.3 band of human chromosome 12. Computer-assisted homology analysis revealed the high sequence similarities of p27-L with a possible counterpart in Caenorhabditis elegans and Saccharomyces cerevisiae whose function is yet unknown, the yeast gene that is here termed NAS2 (non-ATPase subunit 2). Disruption of NAS2 had no effect on cell viability, indicating that the subunit is not essential for proliferation of yeast cells.

Adenosine Triphosphatases↗