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Ryutaro Shirakawa, Hisanori Horiuchi
No abstract text is available yet for this article.
October 2014: Seikagaku. the Journal of Japanese Biochemical Society
Nicolas Personnic, Goran Lakisic, Edith Gouin, Alix Rousseau, Alexis Gautreau, Pascale Cossart, Hélène Bierne
Ral proteins are small GTPases that play critical roles in normal physiology and in oncogenesis. There is little information on the GTPase-activating proteins (GAPs) that downregulate their activity. Here, we provide evidence that the noncatalytic β subunit of RalGAPα1/2 β complexes is involved in mitotic control. RalGAPβ localizes to the Golgi and nucleus during interphase, and relocalizes to the mitotic spindle and cytokinetic intercellular bridge during mitosis. Depletion of RalGAPβ causes chromosome misalignment and decreases the amount of mitotic cyclin B1, disturbing the metaphase-to-anaphase transition...
July 2014: FEBS Journal
Qiaoli Chen, Chao Quan, Bingxian Xie, Liang Chen, Shuilian Zhou, Rachel Toth, David G Campbell, Shuangshuang Lu, Ryutaro Shirakawa, Hisanori Horiuchi, Chaojun Li, Zhongzhou Yang, Carol MacKintosh, Hong Yu Wang, Shuai Chen
Insulin and muscle contraction each stimulate translocation of the glucose transporter GLUT4 to the plasma membrane in skeletal muscle, an important process regulating whole-body glucose homeostasis. RalA mediates insulin-stimulated GLUT4 translocation; however, it is unclear how this small GTPase is regulated in skeletal muscle in response to insulin. Here, we identified GARNL1/RalGAPα1, a major α subunit of the Ral-GTPase activating protein in skeletal muscle, as a protein whose phosphorylation and binding to the regulatory 14-3-3 proteins is stimulated by insulin and also by muscle contraction...
August 2014: Cellular Signalling
(no author information available yet)
A RalGAP-RalB pathway regulates mTORC1 activity independent of Rheb.
March 2014: Cancer Discovery
Timothy D Martin, Xiao-Wei Chen, Rebecca E W Kaplan, Alan R Saltiel, Cheryl L Walker, David J Reiner, Channing J Der
Diverse environmental cues converge on and are integrated by the mTOR signaling network to control cellular growth and homeostasis. The mammalian Tsc1-Tsc2 GTPase activating protein (GAP) heterodimer is a critical negative regulator of Rheb and mTOR activation. The RalGAPα-RalGAPβ heterodimer shares sequence and structural similarity with Tsc1-Tsc2. Unexpectedly, we observed that C. elegans expresses orthologs for the Rheb and RalA/B GTPases and for RalGAPα/β, but not Tsc1/2. This prompted our investigation to determine whether RalGAPs additionally modulate mTOR signaling...
January 23, 2014: Molecular Cell
Dara Leto, Maeran Uhm, Anja Williams, Xiao-wei Chen, Alan R Saltiel
RGC1 and RGC2 comprise a functional RalGAP complex (RGC) that suppresses RalA activity. The PI3-kinase/Akt signaling pathway activates RalA through phosphorylation-mediated inhibition of the RGC. Here we identify a novel phosphorylation-dependent interaction between 14-3-3 and the RGC. 14-3-3 binds to the complex through an Akt-phosphorylated residue, threonine 715, on RGC2. Interaction with 14-3-3 does not alter in vitro activity of the GTPase-activating protein complex. However, blocking the interaction between 14-3-3 and RGC2 in cells increases suppression of RalA activity by the RGC, suggesting that 14-3-3 inhibits the complex through a non-catalytic mechanism...
March 29, 2013: Journal of Biological Chemistry
R Saito, R Shirakawa, H Nishiyama, T Kobayashi, M Kawato, T Kanno, K Nishizawa, Y Matsui, T Ohbayashi, M Horiguchi, T Nakamura, T Ikeda, K Yamane, E Nakayama, E Nakamura, Y Toda, T Kimura, T Kita, O Ogawa, H Horiuchi
The small GTPase Ral is known to be highly activated in several human cancers, such as bladder, colon and pancreas cancers. It is reported that activated Ral is involved in cell proliferation, migration and metastasis of bladder cancer. This protein is activated by Ral guanine nucleotide exchange factors (RalGEFs) and inactivated by Ral GTPase-activating proteins (RalGAPs), the latter of which consist of heterodimers containing a catalytic α1 or α2 subunit and a common β subunit. In Ras-driven cancers, such as pancreas and colon cancers, constitutively active Ras mutant activates Ral through interaction with RalGEFs, which contain the Ras association domain...
February 14, 2013: Oncogene
Ryutaro Shirakawa, Shuya Fukai, Mitsunori Kawato, Tomohito Higashi, Hirokazu Kondo, Tomoyuki Ikeda, Ei Nakayama, Katsuya Okawa, Osamu Nureki, Takeshi Kimura, Toru Kita, Hisanori Horiuchi
The small GTPases RalA and RalB are multifunctional proteins regulating a variety of cellular processes. Like other GTPases, the activity of Ral is regulated by the opposing effects of guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Although several RalGEFs have been identified and characterized, the molecular identity of RalGAP remains unknown. Here, we report the first molecular identification of RalGAPs, which we have named RalGAP1 and RalGAP2. They are large heterodimeric complexes, each consisting of a catalytic alpha1 or alpha2 subunit and a common beta subunit...
August 7, 2009: Journal of Biological Chemistry
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