Shigeto Miura

Hgs (Hrs), a FYVE Domain Protein, Is Involved in Smad Signaling through Cooperation with SARA

ABSTRACT Smad proteins are effector molecules that transmit signals from the receptors for the transforming growth factor β (TGF-β) superfamily to the nucleus; of the Smad proteins, Smad2 and Smad4 are essential components for mouse early embryogenesis. We demonstrated that Hgs, a FYVE domain protein, binds to Smad2 in its C-terminal half and cooperates with another FYVE domain protein, the Smad anchor for receptor activation (SARA), to stimulate activin receptor-mediated signaling through efficient recruitment of Smad2 to the receptor. Furthermore, a LacZ knock-in allele of the C-terminal half-deletion mutant of mouse Hgs was created by gene targeting. The introduced mutation causes an embryonic lethality between embryonic days 8.5 and 10.5. Mutant cells showed significantly decreased responses to stimulation with activin and TGF-β. These findings suggest that the two FYVE domain proteins, Hgs and SARA, are prerequisites for receptor-mediated activation of Smad2.

Mannose-Binding Lectin (MBL)-Associated Serine Protease (MASP)-1 Contributes to Activation of the Lectin Complement Pathway

The complement system plays an important role in innate immunity. In the lectin complement pathway, mannose-binding lectin (MBL) and ficolins act as recognition molecules, and MBL-associated serine protease (MASP) is a key enzyme. It has been suggested that MASP-2 is responsible for the activation of C4. Other serine proteases (MASP-1 and MASP-3) are also associated with MBL or ficolins; however, their functions are still controversial. In this study, a MASP-1- and MASP-3-deficient mouse model (MASP1/3−/−) was generated by a gene targeting strategy to investigate the roles of MASP-1 and MASP-3 in the lectin pathway. Serum derived from MASP1/3−/− mice showed significantly lower activity of both C4 and C3 deposition on mannan-agarose, and this low activity was restored by the addition of recombinant MASP-1. MASP-1/3-deficient serum showed a significant delay for activation of MASP-2 compared with normal serum. Reconstitution of recombinant MASP-1 in MASP-1/3-deficient serum was able to promote the activation of MASP-2. From these results, we propose that MASP-1 contributes to the activation of the lectin pathway, probably through the activation of MASP-2.

Loss of Hippocampal CA3 Pyramidal Neurons in Mice Lacking STAM1

ABSTRACT STAM1, a member of the STAM (signal transducing adapter molecule) family, has a unique structure containing a Src homology 3 domain and ITAM (immunoreceptor tyrosine-based activation motif). STAM1 was previously shown to be associated with the Jak2 and Jak3 tyrosine kinases and to be involved in the regulation of intracellular signal transduction mediated by interleukin-2 (IL-2) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro. Here we generated mice lacking STAM1 by using homologous recombination with embryonic stem cells. STAM1−/− mice were morphologically indistinguishable from their littermates at birth. However, growth retardation in the third week after birth was observed for the STAM1−/− mice. Unexpectedly, despite the absence of STAM1, hematopoietic cells, including T- and B-lymphocyte and other hematopoietic cell populations, developed normally and responded well to several cytokines, including IL-2 and GM-CSF. However, histological analyses revealed the disappearance of hippocampal CA3 pyramidal neurons in STAM1−/− mice. Furthermore, we observed that primary hippocampal neurons derived from STAM1−/− mice are vulnerable to cell death induced by excitotoxic amino acids or an NO donor. These data suggest that STAM1 is dispensable for cytokine-mediated signaling in lymphocytes but may be involved in the survival of hippocampal CA3 pyramidal neurons.

Hrs, a mammalian master molecule in vesicular transport and protein sorting, suppresses the degradation of ESCRT proteins signal transducing adaptor molecule 1 and 2.

The degradation and sorting of cytoplasmic and cell-surface proteins are crucial steps in the control of cellular functions. We previously identified three mammalian Vps (vacuolar protein sorting) proteins, Hrs (hepatocyte growth factor-regulated tyrosine kinase substrate) and signal transducing adaptor molecule (STAM) 1 and -2, which are tyrosine-phosphorylated upon cytokine/growth factor stimulation. Hrs and the STAMs each contain a ubiquitin-interacting motif and through formation of a complex are involved in the vesicle transport of early endosomes. To explore the mechanism and cellular function of this complex in mammalian cells, we established an Hrs-defective fibroblastoid cell line (hrs-/-); embryos with this genotype died in utero. In the hrs-/- cells only trace amounts of STAM1 and STAM2 were detected. Introduction of wild-type Hrs or an Hrs mutant with an intact STAM binding domain (Hrs-dFYVE) fully restored STAM1 and STAM2 expression, whereas mutants with no STAM binding ability (Hrs-dC2, Hrs-dM) failed to express the STAMs. This regulated control of STAM expression by Hrs was independent of transcription. Interestingly, STAM1 degradation was mediated by proteasomes and was partially dependent on the ubiquitin-interacting motif of STAM1. Revertant Hrs expression in hrs-/- cells not only led to the accumulation of ubiquitinated proteins, including intracytoplasmic vesicles, but also restored STAM1 levels in early endosomes and eliminated the enlarged endosome phenotype caused by the absence of Hrs. These results suggest that Hrs is a master molecule that controls in part the degradation of STAM1 and the accumulation of ubiquitinated proteins.

Loss of Neurons in the Hippocampus and Cerebral Cortex of AMSH-Deficient Mice

ABSTRACT AMSH, a molecule that associates with STAM1, is involved in the in vitro cell growth signaling mediated by interleukin 2 and granulocyte-macrophage colony-stimulating factor. To investigate the in vivo functional role of AMSH, we have generated AMSH-deficient mice by gene targeting. The AMSH-deficient mice were morphologically indistinguishable from their littermates at birth, and histopathological examinations revealed normal morphogenesis in all tissues tested. However, all the AMSH-deficient mice exhibited postnatal growth retardation and died between postnatal day 19 (P19) and P23. Examination of brain sections at P6 demonstrated significant loss of neurons and apoptotic cells in the CA1 subfield of the hippocampus. Brain atrophy developed by P16 and was accompanied by complete loss of the CA1 neurons in the hippocampus and marked atrophy of the cerebral cortex. Furthermore, AMSH-deficient hippocampal neuronal cells were unable to survive in vitro, even in the presence of several stimulatory cytokines, while AMSH-deficient cerebellar neurons, thymocytes, and embryonic fibroblasts survived normally. Taken together, these observations indicate that AMSH is an essential molecule for the survival of neuronal cells in early postnatal mice.

Magnetization of YbFe2O4+x

Magnetizations of hexagonal compounds YbFe 2 O 4+ x (polycrystals with x =-0.027, -0.003 and +0.015 and a single crystal with x =+0.03) have been measured in a temperature range between 4.2 K and room temperature. Remanent magnetizations are induced by magnetic fields applied during cooling below about 250 K. Dependences of lattice parameters on x and temperature have also been determined. No lattice distortion occurs at low temperatures in contrast to the case of YFe 2 O 4 .

Shift in the chemical equilibrium of the LaCo5H system by strong magnetic fields

Abstract The equilibrium hydrogen pressure in the β+γ region of the LaCo5-H system has been observed under the influence of magnetic fields up to 14 T. The logarithmic pressure change, In(PH/P0), is 0.19 in 14 T. This corresponds to a 21% change in the equilibrium constant.

Field-induced transitions in intermetallic compounds Mn3GaC and Mn3ZnC

Abstract Field-induced transitions in Mn 3 GaC and Mn 3 ZnC were studied inmagnetic fields up to 320 kOe. Antiferromagnetic (AF)-ferromagnetic (F) field-induced transitions in Mn 3 GaC are of the 1st order and (AF+F)−(F) ones in Mn 3 ZnC are of the 2nd order. Temperature variations of transition fields were determined.

10 nmf perpendicular-anisotropy CoFeB-MgO magnetic tunnel junction with over 400°C high thermal tolerance by boron diffusion control

We have developed a perpendicular-anisotropy magnetic tunnel junction (p-MTJ) stack with CoFeB free layer and Co/Pt multilayer based synthetic ferrimagnetic (SyF) pinned layer that withstand annealing at a temperature up to 420°C (that compatible with CMOS BEOL process) by controlling boron diffusion. We demonstrated the 10 nmφ p-MTJ with double CoFeB/MgO interface tolerable against 400°C annealing which is a requisite building block for realization of high density spin transfer torque magnetic random access memory (STT-MRAM) in reduced dimensions.

Thermodynamic theory of magnetic field effects on chemical equilibria and applications to metal–hydrogen systems

Abstract A general thermodynamic theory was constructed on magnetic field effects on chemical equilibria. Introducing the magnetochemical potential or the electromagnetic chemical potential leads to the magnetic field-induced changes in the equilibrium constant in an ideal gas reaction and the electromotive force in an electrochemical system. Applying these general results to metal–hydrogen systems gives the relationships between the equilibrium hydrogen pressure or the equilibrium electrode potential and magnetic fields, which correspond to experimental data.