Interaction of alpha1-syntrophin with multiple isoforms of heterotrimeric G protein alpha subunits.
Syntrophins are components of the dystrophin-glycoprotein complex of the plasma membrane in muscular and neuronal cells, and recruit signaling proteins such as neuronal nitric oxide synthase via their multiple protein-protein interaction motifs. In this study, we found that alpha1-syntrophin binds to various subtypes of guanine nucleotide-binding protein alpha subunits (Galpha). A pull-down analysis using full-length recombinant alpha1-syntrophin and MS analysis showed that alpha1-syntrophin was coprecipitated with several isoforms of Galpha proteins in addition to known binding partners such as dystrobrevin and neuronal nitric oxide synthase. Further analysis using recombinant Galpha isoforms showed that alpha1-syntrophin associates with at least Galphai, Galphao, Galphas and Galphaq subtypes. The region of alpha1-syntrophin required for its interaction with Galphas was determined as the N-terminal half of the first pleckstrin homology domain. In addition, the syntrophin unique domain of alpha1-syntrophin was suggested to contribute to this interaction. In COS-7 cells, downregulation of alpha1-syntrophin by RNAi resulted in enhanced cAMP production and cAMP response element-binding protein phosphorylation induced by isoproterenol treatment. These results suggest that alpha1-syntrophin provides a scaffold for the Galpha family of heterotrimeric G proteins in the brain to regulate the efficiency of signal transduction evoked by G-protein-coupled receptors.
Institute for Protein Research, Osaka University, Japan.
Akiko
A
Okumura
Katsuya
K
Nagai
Nobuaki
N
Okumura
D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D015536:Down-Regulation; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism*; D008297:Male; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D034622:RNA Interference; D051381:Rats; D017208:Rats, Wistar
D002135:Calcium-Binding Proteins; D044385:GTP-Binding Protein alpha Subunits; D008565:Membrane Proteins; D009124:Muscle Proteins; D020033:Protein Isoforms; C091825:syntrophin alpha1