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  • Title: The lipid raft proteins flotillins/reggies interact with Galphaq and are involved in Gq-mediated p38 mitogen-activated protein kinase activation through tyrosine kinase.
    Author: Sugawara Y, Nishii H, Takahashi T, Yamauchi J, Mizuno N, Tago K, Itoh H.
    Journal: Cell Signal; 2007 Jun; 19(6):1301-8. PubMed ID: 17307333.
    Abstract:
    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.
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