Regulation of GTP-binding protein alpha q (Galpha q) signaling by the ezrin-radixin-moesin-binding phosphoprotein-50 (EBP50).
Although ezrin-radixin-moesin-binding phosphoprotein 50 (EBP50) is a PDZ domain-containing protein known to bind to various channels, receptors, cytoskeletal elements, and cytoplasmic proteins, there is still very little evidence for a role of EBP50 in the regulation of receptor signal transduction. In this report, we show that EBP50 inhibits the phospholipase C (PLC)-beta-mediated inositol phosphate production of a Galpha(q)-coupled receptor as well as PLC-beta activation by the constitutively active Galpha(q)-R183C mutant. Coimmunoprecipitation experiments revealed that EBP50 interacts with Galpha(q) and to a greater extent with Galpha(q)-R183C. Agonist stimulation of the thromboxane A(2) receptor (TP receptor) resulted in an increased interaction between EBP50 and Galpha(q), suggesting that EBP50 preferentially interacts with activated Galpha(q). We also demonstrate that EBP50 inhibits Galpha(q) signaling by preventing the interaction between Galpha(q) and the TP receptor and between activated Galpha(q) and PLC-beta1. Investigation of the EBP50 regions involved in Galpha(q) binding indicated that its two PDZ domains are responsible for this interaction. This study constitutes the first demonstration of an interaction between a G protein alpha subunit and another protein through a PDZ domain, with broad implications in the regulation of diverse physiological systems.
Rochdi
Moulay Driss
MD
Service de Rhumatologie, Faculté de Médecine and Centre de Recherche Clinique-CHUS, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada.
Watier
Valérie
V
La Madeleine
Carole
C
Nakata
Hiroko
H
Kozasa
Tohru
T
Parent
Jean-Luc
JL
D002352:Carrier Proteins / Q000502:physiology*; D002460:Cell Line; D004789:Enzyme Activation; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D054799:Phospholipase C beta; D010750:Phosphoproteins / Q000502:physiology*; D011233:Precipitin Tests; D011485:Protein Binding; D017482:Receptors, Thromboxane / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D017923:Sodium-Hydrogen Exchangers; D010738:Type C Phospholipases / Q000378:metabolism
D002352:Carrier Proteins; D007527:Isoenzymes; D010750:Phosphoproteins; D017482:Receptors, Thromboxane; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D010738:Type C Phospholipases; C518033:PLCB1 protein, human; D054799:Phospholipase C beta; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins