Yuichi Endo

Hrs Is Associated with STAM, a Signal-transducing Adaptor Molecule ITS SUPPRESSIVE EFFECT ON CYTOKINE-INDUCED CELL GROWTH

We previously reported a new type of signal-transducing adaptor molecule, STAM, which was shown to be involved in cytokine-mediated intracellular signal transduction. In this study, we molecularly cloned a 110-kDa phosphotyrosine protein inducible by stimulation with interleukin 2 (IL-2). The 110-kDa molecule was found to be a human counterpart of mouse Hrs (hepatocyte growth factor-regulated tyrosine kinase substrate) and to be associated with STAM. Tyrosine phosphorylation of Hrs is induced rapidly after stimulation with IL-2 and granulocyte-macrophage colony-stimulating factor as well as hepatocyte growth factor. The mutual association sites of Hrs and STAM include highly conserved coiled-coil sequences, suggesting that their association is mediated by the coiled-coil structures. Exogenous introduction of the wild-type Hrs significantly suppressed DNA synthesis upon stimulation with IL-2 and granulocyte-macrophage colony-stimulating factor, while the Hrs mutant deleted of the STAM-binding site lost such suppressive ability. These results suggest that Hrs counteracts the STAM function which is critical for cell growth signaling mediated by the cytokines.

Possible involvement of a novel STAM-associated molecule "AMSH" in intracellular signal transduction mediated by cytokines.

STAM containing an SH3 (Src homology 3) domain and an immunoreceptor tyrosine-based activation motif was previously revealed to be implicated in signaling pathways immediately downstream of Jak2 and Jak3 tyrosine kinases associated with cytokine receptors. We molecularly cloned a novel molecule interacting with the SH3 domain of STAM, which was named AMSH (associatedmolecule with the SH3 domain of STAM). AMSH contains a putative bipartite nuclear localization signal and a homologous region of a c-Jun activation domain-binding protein 1 (JAB1) subdomain in addition to a binding site for the SH3 domain of STAM. AMSH mutant deleted of the C-terminal half conferred dominant negative effects on signaling for DNA synthesis and c-myc induction mediated by interleukin 2 and granulocyte macrophage-colony-stimulating factor. These results suggest that AMSH plays a critical role in the cytokine-mediated intracellular signal transduction downstream of the Jak2/Jak3·STAM complex.

Favelines, novel tricyclic benzocycloheptenes with cytotoxic activities from brazilian plant, doscolus phyllacanthus

Abstract Novel cytotoxic benzocycloheptene derivatives, faveline methyl ether (1) , faveline (2) , and deoxofaveline (3) , have been isolated from the bark of Cnidoscolus phyllacanthus . Those structures were determined on the basis of spectroscopic analysis.

The formation of phosphoenzyme of sarcoplasmic reticulum. Requirement for membrane-bound Ca2+.

Membrane-bound Ca or Mg of sarcoplasmic reticulum fragments were removed by treating the membrane with EDTA or an acidic solution, and the changes in the enzymatic activities of sarcoplasmic reticulum fragments induced by these treatments were examined. With the decrease in the amount of membrane-bound Ca below 1-3-10(-8) mol/mg protein, it was demonstrated that the activity of (Ca2+ + Mg2+)-ATPase transiently increased and then diminished, that the Ca-uptake and phosphoenzyme formation declined gradually, and that the activity of Mg2+-ATPase was affected to a less extent. Sodium dodecyl sulfate-gel electrophoretic patterns of peptides from the metal-deficient membranes were the same as those of the untreated material. The level of the phosphoenzyme formation of the metal-deficient membrane was restored by increasing the amount of membrane-bound Ca, but not by increasing the amount of membrane-bound Mg.

Faveloxide, a new isoprenoid derivative from the Brazilian plant, Cnidoscolus phyllacanthus

A new isoprenoid derivative, faveloxide, was isolated from the bark of Cnidoscolus phyllacanthus. The relative stereostructure (1) was determined on the basis of a spectroscopic analysis and a chemical transformation

Absolute stereochemistry of benzocycloheptenone derivatives from Cnidoscolus phyllacanthus

Abstract Three new benzocycloheptenone derivatives, favelol (1), isofavelol (2), and favelone (3), were isolated from the bark of Cnidoscolus phyllacanthus. Their structures were elucidated on the basis of the spectroscopic analysis. Application of the CD exciton chirality method to 4-methoxybenzoates of 1 and 2 led to determination of the R absolute configuration at C-9, which was confirmed by X-ray crystallographic analysis of the 4-bromobenzoyl derivative of 2.

The Study of MASPs Knockout Mice

Plasma proteases, e.g. thrombin, factor X, complement factor D and C1s are responsible for the physiological activities, such as coagulation and complement system. These proteases circulate as their zymogen in blood and are activated by various stimulations. In this chapter, we focus on a family of plasma serine proteases, called MASP (MBL/ficolinassociated serine protease) that can activate the complement. Three distinct MASP, MASP-1, MASP-2 and MASP-3 have been identified in many species of vertebrates. Although the contribution of MASP-2 in activation of complement was well defined, the substrates for MASP-1 and MASP-3 were still obscure. We have generated MASP-1and MASP-3-deficient mice (Masp1/3-/-) to verify roles of MASP-1 and MASP-3 proteases in vivo. One major finding is that MASP-1, considered being a lectin pathway component—also acts as a pro-factor D (Df) convertase, the initiator of the alternative pathway. Our results emphasize a unique feature of MASP-1, participating two complement pathways. We also generated MASP-2 deficient mice. In here, we would like to summarize the results obtained from these knockout mice.