The lipid raft proteins flotillins/reggies interact with Galphaq and are involved in Gq-mediated p38 mitogen-activated protein kinase activation through tyrosine kinase.
The heterotrimeric G protein alpha q subunit (Galphaq) mediates a variety of cell functions by activating the effector molecule phospholipase Cbeta. Galphaq activity is regulated by G protein betagamma subunits, G protein-coupled receptors, RGS proteins, and Ric-8. In this study, we identified the lipid raft resident proteins, flotillin-1/reggie-2 and flotillin-2/reggie-1, as Galphaq-binding proteins. The interactions of Galphaq and flotillins were independent of the nucleotide-binding state of Galphaq, and the N-terminal portion of flotillins was critical for the interaction. A short interfering RNA-mediated knockdown of flotillins, particularly flotillin-2, attenuated the UTP-induced activation of p38 mitogen-activated protein kinase (MAPK) but not that of ERK1/2. The activation of p38 MAPK was inhibited by the Src family tyrosine kinase inhibitor PP2 and the cholesterol-depleting agent methyl-beta-cyclodextrin, which is generally used for the disruption of lipid rafts. In contrast, the activation of ERK1/2 was not inhibited by these compounds. These lines of evidence suggested that a Gq-coupled receptor activates specifically p38 MAPK through lipid rafts and Src kinase activation, in which flotillins positively modulate the Gq signaling.
Sugawara
Yo
Y
Laboratory of Signal Transduction, Department of Cell Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
Nishii
Hiroko
H
Takahashi
Tomoko
T
Yamauchi
Junji
J
Mizuno
Norikazu
N
Tago
Kenji
K
Itoh
Hiroshi
H
D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058473:Receptors, Purinergic P2Y2; D020798:Two-Hybrid System Techniques; D014544:Uridine Triphosphate / Q000494:pharmacology; D047392:beta-Cyclodextrins / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism*
D008565:Membrane Proteins; C546385:P2RY2 protein, human; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D047392:beta-Cyclodextrins; C106354:flotillins; D019061:src-Family Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; C031215:betadex; D014544:Uridine Triphosphate