TY - JOUR
T1 - Ubiquitination of the heterotrimeric G protein α subunits Gαi2 and Gαq is prevented by the guanine nucleotide exchange factor Ric-8A
AU - Chishiki, Kanako
AU - Kamakura, Sachiko
AU - Yuzawa, Satoru
AU - Hayase, Junya
AU - Sumimoto, Hideki
N1 - Funding Information:
We thank Prof. Mitsuyoshi Nakao (Institute of Molecular Embryology and Genetics, Kumamoto University) for pCGN-HA–Ub; Namiko Kubo (Kyushu University) and Yohko Kage (Kyushu University) for technical assistance, and to Minako Nishino (Kyushu University) for secretarial assistance. This work was supported in part by MEXT (the Ministry of Education, Culture, Sports, Science and Technology) KAKENHI Grant Numbers 20117002 and 24113718 , and by JSPS (Japan Society for the Promotion of Science) KAKENHI Grant Number 24590385 .
PY - 2013/6/7
Y1 - 2013/6/7
N2 - The cytosolic protein Ric-8A acts as a guanine nucleotide exchange factor for Gα subunits of the Gi, Gq, and G12/13 classes of heterotrimeric G protein in vitro, and is also known to increase the amounts of these Gα proteins in vivo. The mechanism whereby Ric-8 regulates Gα content, however, has not been fully understood. Here we show that Ric-8 Astabilizes Gαi2 and Gαq by preventing their ubiquitination. Ric-8A interacts with and stabilizes Gαi2, Gαq, Gα12, but not Gαs, when expressed in COS-7 cells. The protein levels of Gαi2 and Gαq appear to be controlled via the ubiquitin-proteasome degradation pathway, because these Gα subunits undergo polyubiquitination and are stabilized with the proteasome inhibitor MG132. The ubiquitination of Gαi2 and Gαq is suppressed by expression of Ric-8A. The suppression likely requires Ric-8A interaction with these Gα proteins; the C-terminal truncation of Gαq and Gαi2 completely abrogates their interaction with Ric-8A, their stabilization by Ric-8A, and Ric-8A-mediated inhibition of Gα ubiquitination.
AB - The cytosolic protein Ric-8A acts as a guanine nucleotide exchange factor for Gα subunits of the Gi, Gq, and G12/13 classes of heterotrimeric G protein in vitro, and is also known to increase the amounts of these Gα proteins in vivo. The mechanism whereby Ric-8 regulates Gα content, however, has not been fully understood. Here we show that Ric-8 Astabilizes Gαi2 and Gαq by preventing their ubiquitination. Ric-8A interacts with and stabilizes Gαi2, Gαq, Gα12, but not Gαs, when expressed in COS-7 cells. The protein levels of Gαi2 and Gαq appear to be controlled via the ubiquitin-proteasome degradation pathway, because these Gα subunits undergo polyubiquitination and are stabilized with the proteasome inhibitor MG132. The ubiquitination of Gαi2 and Gαq is suppressed by expression of Ric-8A. The suppression likely requires Ric-8A interaction with these Gα proteins; the C-terminal truncation of Gαq and Gαi2 completely abrogates their interaction with Ric-8A, their stabilization by Ric-8A, and Ric-8A-mediated inhibition of Gα ubiquitination.
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U2 - 10.1016/j.bbrc.2013.04.103
DO - 10.1016/j.bbrc.2013.04.103
M3 - Article
C2 - 23665327
AN - SCOPUS:84878985768
VL - 435
SP - 414
EP - 419
JO - Biochemical and Biophysical Research Communications
JF - Biochemical and Biophysical Research Communications
SN - 0006-291X
IS - 3
ER -