Biomedical subjects

A Maeda

Publications and source records attributed to A Maeda.

At least 91 records · Page 5Linked to original sources

PubMed1999

Release of coronavirus E protein in membrane vesicles from virus-infected cells and E protein-expressing cells.

Coronavirus E protein is a small viral envelope protein that plays an essential role in coronavirus assembly; coexpression of coronavirus M and E proteins results in the production of virus-like particles. The present study demonstrated that mouse hepatitis virus (MHV) E protein was released as an integral membrane protein in lipid vesicles from E-protein-expressing mammalian cells, in the absence of other MHV proteins. Furthermore, our data indicated that the E-protein-containing vesicles, which had a slightly lighter buoyant density than that of MHV, were released from MHV-infected cells. These data implied that E protein alone can drive the production and release of coronavirus envelope in the absence of M protein.

Animals↗

PubMed1999

Molecular and functional characterization of a novel mouse transient receptor potential protein homologue TRP7. Ca(2+)-permeable cation channel that is constitutively activated and enhanced by stimulation of G protein-coupled receptor.

Characterization of mammalian homologues of Drosophila transient receptor potential protein (TRP) is an important clue to understand molecular mechanisms underlying Ca(2+) influx activated in response to stimulation of G(q) protein-coupled receptors in vertebrate cells. Here we have isolated cDNA encoding a novel seventh mammalian TRP homologue, TRP7, from mouse brain. TRP7 showed abundant RNA expression in the heart, lung, and eye and moderate expression in the brain, spleen, and testis. TRP7 recombinantly expressed in human embryonic kidney cells exhibited distinctive functional features, compared with other TRP homologues. Basal influx activity accompanied by reduction in Ca(2+) release from internal stores was characteristic of TRP7-expressing cells but was by far less significant in cells expressing TRP3, which is structurally the closest to TRP7 in the TRP family. TRP7 induced Ca(2+) influx in response to ATP receptor stimulation at ATP concentrations lower than those necessary for activation of TRP3 and for Ca(2+) release from the intracellular store, which suggests that the TRP7 channel is activated independently of Ca(2+) release. In fact, TRP7 expression did not affect capacitative Ca(2+) entry induced by thapsigargin, whereas TRP7 greatly potentiated Mn(2+) influx induced by diacylglycerols without involvement of protein kinase C. Nystatin-perforated and conventional whole-cell patch clamp recordings from TRP7-expressing cells demonstrated the constitutively activated and ATP-enhanced inward cation currents, both of which were initially blocked and then subsequently facilitated by extracellular Ca(2+) at a physiological concentration. Impairment of TRP7 currents by internal perfusion of the Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid revealed an essential role of intracellular Ca(2+) in activation of TRP7, and their potent activation by the diacylglycerol analogue suggests that the TRP7 channel is a new member of diacylglycerol-activated cation channels. Relative permeabilities indicate that TRP7 is slightly selective to divalent cations. Thus, our findings reveal an interesting correspondence of TRP7 to the background and receptor stimulation-induced cation currents in various native systems.

Amino Acid Sequence↗

PubMed1999

Effects of humid heat exposure on human sleep stages and body temperature.

The objective of this study was to confirm the effect of humid heat exposure on sleep stages and body temperature. Seven healthy male volunteers with a mean age of 22.7+/-1.63, served as the subjects. The experiments were carried out under four different conditions of room temperature and relative humidity: 29 degrees C RH 50% (29/50), 29 degrees C RH 75% (29/75), 35 degrees C RH 50% (35/50), and 35 degrees C RH 75% (35/75). The subjects wearing only shorts slept from 23:00 to 7:00 on a bed, which was covered with a 100% cotton sheet. EEG, EOG, and mental EMG were recorded through the night. Rectal temperature (Tr) and skin temperature were measured continuously. The 35/75 condition caused more wake and a lower sleep efficiency index (SEI) and stage S3+S4 than 29/50 and 29/75. Stage REM and stage 3 were significantly decreased at 35/75 than at 29/50 and 35/50. Tr was maintained at a higher level at 35/75 than under the other conditions. Mean skin temperature was higher at 35/50 and 35/75 than at 29/50 and 29/75. These results suggest that humid heat exposure during night sleep increases the thermal load to supress the sleep-evoked Tr decrease, stage 3, SWS, and REM, and increase wakefulness.

Adult↗

PubMed1999

Effect of anion binding on iodopsin studied by low-temperature fourier transform infrared spectroscopy.

The effect of anion binding on iodopsin, the chicken red-sensitive cone visual pigment, was studied by measurements of the Fourier transform infrared spectra of chloride- and nitrate-bound forms of iodopsin at 77 K. In addition to the blue shift of the absorption maximum upon substituting nitrate for chloride, the C=C stretching vibrations of iodopsin and its photoproducts were upshifted 5-6 cm(-)(1). The C=NH and C=ND stretching vibrations were the same in wavenumber between the chloride- and nitrate-bound forms, indicating that the binding of either chloride or nitrate has no effect on the interaction between the protonated Schiff base and the counterion. The vibrational bands of iodopsin in the fingerprint and the hydrogen out-of-plane wagging regions were insensitive to anion substitution, suggesting that local chromophore interactions with the anions are not crucial for the absorption spectral shift. In contrast, bathoiodopsin in the chloride-bound form exhibited an intense C(14)H wagging mode, whose intensity was considerably weakened upon substitution of nitrate for chloride. These results suggest that binding of chloride changes the environment near the C(14) position of the chromophore, which could be one of the factors in the thermal reverse reaction of bathoiodopsin to iodopsin in the chloride-bound form.

Anions↗

PubMed1999

Structural change of threonine 89 upon photoisomerization in bacteriorhodopsin as revealed by polarized FTIR spectroscopy.

The all-trans to 13-cis photoisomerization of the retinal chromophore of bacteriorhodopsin occurs selectively, efficiently, and on an ultrafast time scale. The reaction is facilitated by the surrounding protein matrix which undergoes further structural changes during the proton-transporting reaction cycle. Low-temperature polarized Fourier transform infrared difference spectra between bacteriorhodopsin and the K intermediate provide the possibility to investigate such structural changes, by probing O-H and N-H stretching vibrations [Kandori, Kinoshita, Shichida, and Maeda (1998) J. Phys. Chem. B 102, 7899-7905]. The measurements of [3-18O]threonine-labeled bacteriorhodopsin revealed that one of the D2O-sensitive bands (2506 cm(-1) in bacteriorhodopsin and 2466 cm(-1) in the K intermediate, in D2O exhibited 18(O)-induced isotope shift. The O-H stretching vibrations of the threonine side chain correspond to 3378 cm(-1) in bacteriorhodopsin and to 3317 cm(-1) in the K intermediate, indicating that hydrogen bonding becomes stronger after the photoisomerization. The O-H stretch frequency of neat secondary alcohol is 3340-3355 cm(-1). The O-H stretch bands are preserved in the T46V, T90V, T142N, T178N, and T205V mutant proteins, but diminished in T89A and T89C, and slightly shifted in T89S. Thus, the observed O-H stretching vibration originates from Thr89. This is consistent with the atomic structure of this region, and the change of the S-H stretching vibration of the T89C mutant in the K intermediate [Kandori, Kinoshita, Shichida, Maeda, Needleman, and Lanyi (1998) J. Am. Chem. Soc. 120, 5828-5829]. We conclude that all-trans to 13-cis isomerization causes shortening of the hydrogen bond between the OH group of Thr89 and a carboxyl oxygen atom of Asp85.

Aspartic Acid↗

PubMed1999

Existence of two L photointermediates of halorhodopsin from Halobacterium salinarium, differing in their protein and water FTIR bands.

FTIR difference spectra were recorded for the photoreactions of halorhodopsin from Halobacterium salinarium at 170 and 250 K. Obvious differences at the two temperatures were noted in neither the visible spectra nor the FTIR bands of the chromophore. However, perturbation of Asp141 is observed in the L intermediate at 250 K but not at 170 K. We named these photoproducts La (at 170 K) and Lb (at 250 K). The spectrum of Lb is distinct from that of La also in the different shifts of water O-H stretching bands, and larger changes in the bands from the protein backbone with different sensitivities to varying the halide. These results suggest that the photocycle of halorhodopsin contains two L states, La and Lb, in which the structure of protein and internal water molecules is different but chloride stays at the same site close to the Schiff base.

Bacteriorhodopsins↗

PubMed1999

Chromophore-protein-water interactions in the L intermediate of bacteriorhodopsin: FTIR study of the photoreaction of L at 80 K.

Using FTIR spectroscopy, perturbations of several residues and internal water molecules have been detected when light transforms all-trans bacteriorhodopsin (BR) to its L intermediate having a 13-cis chromophore. Illumination of L at 80 K results in an intermediate L' absorbing around 550 nm. L' thermally converts to the original BR only at >130 K. In this study, we used the light-induced transformation of L to L' at 80 K to identify some amino acid residues and water molecules that closely interact with the chromophore and distinguish them from those residues not affected by the photoreaction. The L minus L' FTIR difference spectrum shows that the chromophore in L' is in the all-trans configuration. The perturbed states of Asp96 and Val49 and of the environment along the aliphatic part of the retinal and Lys216 seen in L are not affected by the L --> L' photoreaction. On the other hand, the environments of the Schiff base of the chromophore, of Asp115, and of water molecules close to Asp85 returned in L' to their state in which they originally had existed in BR. The water molecules that are affected by the mutations of Thr46 and Asp96 also change to a different state in the L --> L' transition, as indicated by transformation of a water O-H vibrational band at 3497 cm-1 in L into an intense peak at 3549 cm-1 in L'. Notably, this change of water bands in the L --> L' transition at 80 K is entirely different from the changes observed in the BR --> K photoreaction at the same temperature, which does not show such intense bands. These results suggest that these water molecules move closer to the Schiff base as a hydrogen bonding cluster in L and L', presumably to stabilize its protonated state during the BR to L transition. They may contribute to the structural constraints that prevent L from returning to the initial BR upon illumination at 80 K.

Alanine↗

PubMed1999

Paired immunoglobulin-like receptor B (PIR-B) inhibits BCR-induced activation of Syk and Btk by SHP-1.

Coligation of paired immunoglobulin-like receptor B (PIR-B) with B cell antigen receptor (BCR) blocks antigen-induced B cell activation. This inhibition is mediated in part by recruitment of SHP-1 and SHP-2 to the phosphorylated ITIMs in the cytoplasmic domain of PIR-B; however the molecular target(s) of these phosphatases remain elusive. Here we show that PIR-B ligation inhibits the BCR-induced tyrosine phosphorylation of Igalpha/Igbeta, Syk, Btk and phospholipase C (PLC)-gamma2. Overexpression of a catalytically inactive form of SHP-1 prevents the PIR-B-mediated inhibition of tyrosine phosphorylation of Syk, Btk, and PLC-gamma2. Dephosphorylation of Syk and Btk mediated by SHP-1 leads to a decrease of their kinase activity, which in turn inhibits tyrosine phosphorylation of PLC-gamma2. Furthermore, we define a requirement for Lyn in mediating tyrosine phosphorylation of PIR-B. Based on these results, we propose a model of PIR-B-mediated inhibitory signaling in which coligation of PIR-B and BCR results in phosphorylation of ITIMs by Lyn, subsequent recruitment of SHP-1, and a resulting inhibition of the BCR-induced inositol 1,4,5-trisphosphate generation by dephosphorylation of Syk and Btk.

Agammaglobulinaemia Tyrosine Kinase↗

PubMed1999

Encoding of Ca2+ signals by differential expression of IP3 receptor subtypes.

Inositol 1,4,5-trisphosphate (IP3) plays a key role in Ca2+ signalling, which exhibits a variety of spatio-temporal patterns that control important cell functions. Multiple subtypes of IP3 receptors (IP3R-1, -2 and -3) are expressed in a tissue- and development-specific manner and form heterotetrameric channels through which stored Ca2+ is released, but the physiological significance of the differential expression of IP3R subtypes is not known. We have studied the Ca2+-signalling mechanism in genetically engineered B cells that express either a single or a combination of IP3R subtypes, and show that Ca2+-signalling patterns depend on the IP3R subtypes, which differ significantly in their response to agonists, i.e. IP3, Ca2+ and ATP. IP3R-2 is the most sensitive to IP3 and is required for the long lasting, regular Ca2+ oscillations that occur upon activation of B-cell receptors. IP3R-1 is highly sensitive to ATP and mediates less regular Ca2+ oscillations. IP3R-3 is the least sensitive to IP3 and Ca2+, and tends to generate monophasic Ca2+ transients. Furthermore, we show for the first time functional interactions between coexpressed subtypes. Our results demonstrate that differential expression of IP3R subtypes helps to encode IP3-mediated Ca2+ signalling.

Adenosine Triphosphate↗

PubMed1999

Significant role of intragraft lymphoid tissues in preventing insulin-dependent diabetes mellitus recurrence in whole pancreaticoduodenal transplantation.

Graft recurrence of insulin-dependent diabetes mellitus (IDDM) was examined. Islet transplantation or pancreas-alone transplantation excluding the duodenum and peripancreatic lymph nodes was compared with whole pancreaticoduodenal transplantation. A Wistar Furth (WF; RT1(u), RT6.2) to major histocompatibility complex (MHC)-compatible diabetes-prone (DP; RT1(u), RT6.1 gene carrier)-biobreeding (BB) rat transplantation model was used. Only DP recipients that had been transplanted with whole pancreaticoduodenal grafts were free from IDDM recurrence (>60 days postgrafting) when treated with anti-intercellular adhesion moluecule-1 (ICAM)-1/leukocyte function-associated antigen-1 (LFA-1) monoclonal antibodies (mAbs). In the spleen cells of the DP rats that had accepted pancreatic grafts (60 days postgrafting), flow cytometric analysis showed that NKR-P1(+)TCRalphabeta(+) (NKT) cells had proliferated markedly, with the proportion of 12.8 +/- 1.7% in the total splenic T cells, most of which (86.2%) were derived from the donor (RT6.2(+)). By enzyme-linked immunonosorbent assay (ELISA), serum interferon gamma (IFN-gamma) was not detected (<13 pg/ml) in all rats. However, interleukin-4 (IL-4) was detected as 158.8 +/- 28.0 pg/ml in the nonrecurrent DP recipients. These data suggested that to prevent IDDM recurrence in the pancreatic graft, the lymphocytes in the pancreaticoduodenal grafts are necessary. Also, the donor-derived NKT cells might have some immunoregulatory functions with a Th2 deviation.

Animals↗

PubMed1999

Expression of C-C chemokines in bronchoalveolar lavage cells from patients with granulomatous lung diseases.

To determine the role of C-C chemokines in the pathogenesis of granulomatous lung diseases, we studied the mRNA levels of C-C chemokines, regulated on activation normal T expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and monocyte chemoattractant protein (MCP)-1 in bronchoalveolar lavage (BAL) cells obtained from patients with sarcoidosis (n = 17), hypersensitivity pneumonitis (HP) (n = 4), and cryptogenic fibrosing alveolitis (CFA) (n = 10) using the reverse transcription-polymerase chain reaction (RT-PCR) technique. The mRNA levels of RANTES, MIP-1alpha, and MIP-1beta in BAL cells were significantly correlated with the lavaged lymphocyte proportion, and a significant inverse correlation was observed between the mRNA level of MIP-1beta and the CD4/CD8 ratio of lavaged lymphocytes. Among the three diseases, the mRNA levels of RANTES and MIP-1alpha were significantly higher in the patients with sarcoidosis or HP compared with those in the patients with CFA. The level of MIP-1beta mRNA was significantly higher in the HP patients compared with that in the patients with sarcoidosis or CFA. No significant differences were observed in the level of MCP-1 mRNA among the three diseases. Thus, RANTES and MIP-1alpha were suggested to be important in the pathogenesis of granulomatous inflammation in sarcoidosis and HP. MIP-1beta might play an important role in the pathogenesis of HP, mediating the recruitment of lymphocytes specific to HP.

Adult↗

PubMed1999