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435 results on '"Kaziro, Yoshito"'

6. Unique multipotent cells in adult human mesenchymal cell populations

Author

Kuroda, Yasumasa, Kitada, Masaaki, Wakao, Shohei, Nishikawa, Kouki, Tanimura, Yukihiro, Makinoshima, Hideki, Goda, Makoto, Akashi, Hideo, Inutsuka, Ayumu, Niwa, Akira, Shigemoto, Taeko, Nabeshima, Yoko, Nakahata, Tatsutoshi, Nabeshima, Yo-ichi, Fujiyoshi, Yoshinori, Dezawa, Mari, and Kaziro, Yoshito

Published
2010

32. A glutamate residue at the C terminus regulates activity of inward rectifier [K.sup.+] channels: Implication for Andersen's syndrome

Author

Chen, Lei, Kawano, Takeharu, Bajic, Sibinka, Kaziro, Yoshito, Itoh, Hiroshi, Art, Jonathan J., Nakajima, Yasuko, and Nakajima, Shigehiro

Subjects
G proteins -- Physiological aspects, Glutamate -- Physiological aspects, Cell membranes -- Physiological aspects, Science and technology
Abstract

G protein-coupled inward rectifiers (GIRKs) are activated directly by G protein [beta][gamma], subunits, whereas classical inward rectifiers (IRKs) are constitutively active. We found that a glutamate residue of GIRK2 (E315), located on a hydrophobic domain of the C terminus, is crucial for the channel activation. This glutamate (or aspartate) residue is conserved in all members of the Kir family. Substitution of alanine for the glutamate on GIRK1, GIRK2, and IRK2, expressed in HEK293 cells, greatly reduced the whole-cell currents. The whole-cell current of GIRK channels with a constitutively active gate, GIRK2(V188A), [Yi, B. A., Lin, Y. F., Jan, Y. N. & Jan, L. Y. (2001) Neuron 29, 657-667] was also reduced by the same glutamate mutation. Mean open time and conductance of single channels in GIRK2 and IRK2 were not affected by the mutation, indicating that the reduced whole-cell current resulted from a lowered probability of channel activation. The mutated GIRK and IRK showed normal trafficking to the cell membrane. The mutated GIRK2 retained the ability to interact with G protein [beta][gamma] subunits, and it showed almost the same inwardly rectifying property as the wild type. The mutated GIRK1 and GIRK2 retained ion selectivity to K+ ions. This glutamate residue corresponds to one of the residues causing Andersen's syndrome [Plaster, N. M., Tawil, R., Tristani-Firouzi, M., Canun, S., Bendahhou, S., Tsunoda, A., Donaldson, M. R., lannaccone, S. T., Brunt, E., Barohn, R., etal. (2001) Cell 105, 511-519]. Our interpretation is that this region of the glutamate residue is crucial in relaying the activating message from the ligand sensor region to the gate.

Published
2002

36. G protein beta-gamma subunit-dependent Rac-guanine nucleotide exchange activity of Ras-GRFI/CDC25(super Mm)

Author

Kiyono, Mari, Satoh, Takaya, and Kaziro, Yoshito

Subjects
G proteins -- Research, Biochemistry -- Research, Amino acids -- Research, Cellular control mechanisms -- Research, Science and technology
Abstract

Ras-GRF1 has been implicated as a Ras-specific guanine nucleotide exchange factor (GEF), which mediates calcium- and muscarinic receptor-triggered signals in the brain. Although a Dbl homology domain known as a motif conserved among GEFs that target Rho family GTP-binding proteins exists in Ras-GRF1, GEF activity toward Rho family proteins has not been observed. Here we show that Ras-GRF1 exhibits Rac1-specific GEF activity when recovered from cells overexpressing G protein [Beta][Gamma] subunits ([G.sub.[Beta][Gamma]]). Substitution of conserved amino acids within the Dbl homology domain abolished this activity. Activation of the Rac pathway in the cell was further evidenced by synergistic activation of the stress kinase JNK1 by Ras-GRF1 and [G.sub.[Beta][Gamma]], which is sensitive to inhibitory action of dominant-negative Rac1(17N). In addition, association of Ras-GRF1 with Rac1(17N) was demonstrated by coimmunoprecipitation. Evidence for the involvement of tyrosine kinase(s) in [G.sub.[Beta][Gamma]]-mediated induction of Rac1-specific GEF activity was provided by the use of specific inhibitors. These results suggest a role of Ras-GRF1 for regulating Rac-dependent as well as Ras-dependent signaling pathways, particularly in the brain functions.

Published
1999

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