Crystal structure of a thermophilic GrpE protein: insight into thermosensing function for the DnaK chaperone system.

A homodimeric GrpE protein functions as a nucleotide exchange factor of the eubacterium DnaK molecular chaperone system. The co-chaperone GrpE accelerates ADP dissociation from, and promotes ATP binding to, DnaK, which cooperatively facilitates the DnaK chaperone cycle with another co-chaperone, DnaJ. GrpE characteristically undergoes two-step conformational changes in response to elevation of the environmental temperature. In the first transition at heat-shock temperatures, a fully reversible and functionally deficient structural alteration takes place in GrpE, and then the higher temperatures lead to the irreversible dissociation of the GrpE dimer into monomers as the second transition. GrpE is also thought to be a thermosensor of the DnaK system, since it is the only member of the DnaK system that changes its structure reversibly and loses its function at heat-shock temperatures of various organisms. We here report the crystal structure of GrpE from Thermus thermophilus HB8 (GrpE(Tth)) at 3.23 A resolution. The resolved structure is compared with that of GrpE from mesophilic Escherichia coli (GrpE(Eco)), revealing structural similarities, particularly in the DnaK interaction regions, and structural characteristics for the thermal stability of GrpE(Tth). In addition, the structure analysis raised the possibility that the polypeptide chain in the reported GrpE(Eco) structure was misinterpreted. Comparison of these two GrpE structures combined with the results of limited proteolysis experiments provides insight into the protein dynamics of GrpE(Tth) correlated with the shift of temperature, and also suggests that the localized and partial unfolding at the plausible DnaK interaction sites of GrpE(Tth) causes functional deficiency of nucleotide exchange factor in response to the heat shock

Physiological roles of dietary glutamate signaling via gut–brain axis due to efficient digestion and absorption

Dietary glutamate (Glu) stimulates to evoke the umami taste, one of the five basic tastes, enhancing food palatability. But it is also the main gut energy source for the absorption and metabolism for each nutrient, thus, only a trace amount of Glu reaches the general circulation. Recently, we demonstrated a unique gut sensing system for free Glu (glutamate signaling). Glu is the only nutrient among amino acids, sugars and electrolytes that activates rat gastric vagal afferents from the luminal side specifically via metabotropic Glu receptors type 1 on mucosal cells releasing mucin and nitrite mono-oxide (NO), then NO stimulates serotonin (5HT) release at the enterochromaffin cell. Finally released 5HT stimulates 5HT(3) receptor at the nerve end of the vagal afferent fiber. Functional magnetic resonance imaging (f-MRI, 4.7 T) analysis revealed that luminal sensing with 1 % (w/v) monosodium l-glutamate (MSG) in rat stomach activates both the medial preoptic area (body temperature controller) and the dorsomedial hypothalamus (basic metabolic regulator), resulting in diet-induced thermogenesis during mealing without changes of appetite for food. Interestingly, rats were forced to eat a high fat and high sugar diet with free access to 1 % (w/w) MSG and water in a choice paradigm and showed the strong preference for the MSG solution and subsequently, they displayed lower fat deposition, weight gain and blood leptin. On the other hand, these brain functional changes by the f-MRI signal after 60 mM MSG intubation into the stomach was abolished in the case of total vagotomized rats, suggesting that luminal glutamate signaling contributes to control digestion and thermogenesis without obesity

Estimation of springback of stainless steel sheet part taking influence of anisotropic property of plastic-deformation-dependent young's modulus into account

A kinematic hardening model proposed by Yoshida and Uemori (Y-U model) was applied to the prediction of springback of stainless steel sheet part. From the experiments for the determination of the material constants, an anisotropic property of change in Young’s modulus was observed; namely, the anisotropy was different at 0°, 45° and 90° from the rolling direction. The Y-U model for the stainless steel sheet was used to a calculation of a forming process of a part to examine the accuracy of the prediction of the springback by compar-ing the calculated result with the actual part formed. In order to consider the anisotropic property of change in Young’s modulus, the calculated result to the actual part formed. In order to consider the anisotropic property of the change in Young’s modulus, the calculations were performed using the different material constants at 0°, 45° and 90° from the rolling direction. With the material constants at 90° from the rolling direction, which was the direction of springback of the part, the prediction accuracy can be improved. Therefore, the consideration of the anisotropic property of the change in Young’s modulus was found to be effective for more accurate prediction of the springback of the stainless steel part

Hepatocyte growth factor and Met in tumor biology and therapeutic approach with NK4

金沢大学がん研究所分子標的がん医療研究開発センターHepatocyte growth factor (HGF) and Met/HGF receptor tyrosine kinase play a role in the progression to invasive and metastatic cancers. A variety of cancer cells secrete molecules that enhance HGF expression in stromal fibroblasts, while fibroblast-derived HGF, in turn, is a potent stimulator of the invasion of cancer cells. In addition to the ligand-dependent activation, Met receptor activation is negatively regulated by cell-cell contact and Ser985 phosphorylation in the juxtamembrane of Met. The loss of intercellular junctions may facilitate an escape from the cell-cell contact-dependent suppression of Met-signaling. Significance of juxtamembrane mutations found in human cancers is assumed to be a loss-of-function in the negative regulation of Met. In attempts to block the malignant behavior of cancers, NK4 was isolated as a competitive antagonist against HGF-Met signaling. Independently on its HGF-antagonist action, NK4 inhibited angiogenesis induced by vascular endothelial cell growth factor and basic fibroblast growth factor, as well as HGF. In experimental models of distinct types of cancers, NK4 inhibited Met activation and this was associated with inhibition of tumor invasion and metastasis. NK4 inhibited tumor angiogenesis, thereby suppressing angiogenesis-dependent tumor growth. Cancer treatment with NK4 suppresses malignant tumors to be "static" in both tumor growth and spreading. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA

Anti-cancer Approach with NK4 and Anti-angiogenic Mechanism of NK4: Inhibition of Endothelial Fibronectin Assembly and Colon Cancer Metastasis

Division of Tumor Dynamics and Regulatio