G Protein-coupled Receptor-promoted Trafficking of Gβ₁γ₂Leads to AKT Activation at Endosomes via a Mechanism Mediated by Gβ₁γ₂-Rab11a Interaction

Abstract

G-protein coupled receptors activate heterotrimeric G proteins at the plasma membrane in which most of their effectors are intrinsically located or transiently associated as the external signal is being transduced. This paradigm has been extended to the intracellular compartments by studies in yeast showing that trafficking of G␣ activates phosphatidylinositol 3-kinase (PI3K) at endosomal compartments, suggesting that vesicle trafficking regulates potential actions of G␣ and possibly G␤␥ at the level of endosomes. Here, we show that G␤␥ interacts with Rab11a and that the two proteins colocalize at early and recycling endosomes in response to activation of lysophosphatidic acid (LPA) receptors. This agonist-dependent association of G␤␥ to Rab11a-positive endosomes contributes to the recruitment of PI3K and phosphorylation of AKT at this intracellular compartment. These events are sensitive to the expression of a dominant-negative Rab11a mutant or treatment with wortmannin, suggesting that Rab11a-dependent G␤␥ trafficking promotes the activation of the PI3K/AKT signaling pathway associated with endosomal compartments. In addition, RNA interference-mediated Rab11a depletion, or expression of a dominant-negative Rab11a mutant attenuated LPA-dependent cell survival and proliferation, suggesting that endosomal activation of the PI3K/AKT signaling pathway in response to G␤␥ trafficking, via its interaction with Rab11, is a relevant step in the mechanism controlling these fundamental events.

Polarity mediates asymmetric trafficking of the Gβ heterotrimeric G-protein subunit GPB-1 inC. elegansembryos

“…Association of heterotrimeric G protein components with endosomal compartments has been observed in mammalian cells in the context of their function in receptor-mediated signaling Garcia-Regalado et al, 2008;Hynes et al, 2004;Saini et al, 2007). Our work demonstrates that heterotrimeric G protein subunits are also very dynamic in the context of their role in asymmetric cell division, which is thought to be receptor independent (for reviews, see Gönczy, 2008;Knoblich, 2008).…”

Early Endosomal Antigen 1 (EEA1) Is an Obligate Scaffold for Angiotensin II-induced, PKC-α-dependent Akt Activation in Endosomes

“…More specifically, lipid rafts have been implicated as a domain where PKC-␣-dependent phosphorylation of Akt occurs (24). Other investigators, however, reported evidence indicating that in some signaling pathways, endocytosis is required for Akt activation (15,26,53). For example, the APPL1 protein, a marker of APPL endosomes (precursors of EEA1 early endosomes (16)), is required for Akt phosphorylation in zebrafish (15).…”

“…In the conventional model, Akt activation mainly occurs at the plasma membrane in lipid rafts and nonlipid raft microdomains (23,24). We and others (15,(25)(26)(27)(28) reported that general inhibitors of endocytosis and/or intracellular membrane trafficking modulate signaling events initiated at the plasma membrane. For example, a dynamin dominant negative mutant, concanavalin A and methyl-␤-cyclodextrin prevent Akt activation in several cell types (27,29).…”

Activation of Swelling-activated Chloride Current by Tumor Necrosis Factor-α Requires ClC-3-dependent Endosomal Reactive Oxygen Production

“…Rab11 controls movement of proteins through a recycling compartment that forms via processing of early endosomes and mediates movement of endocytosed proteins back to the plasma membrane (48,49). S25N Rab11 disrupts this process and impairs both processing of and signaling via G-protein-coupled receptors, including the lysophosphatidic acid receptor (48,50). Both S34N Rab5 and S25N Rab11 profoundly impaired the ability of TNF-␣ (Fig.…”