Gpr161 anchoring of PKA consolidates GPCR and cAMP signaling

Abstract

Scaffolding proteins organize the information flow from activated G protein-coupled receptors (GPCRs) to intracellular effector cascades both spatially and temporally. By this means, signaling scaffolds, such as A-kinase anchoring proteins (AKAPs), compartmentalize kinase activity and ensure substrate selectivity. Using a phosphoproteomics approach we identified a physical and functional connection between protein kinase A (PKA) and Gpr161 (an orphan GPCR) signaling. We show that Gpr161 functions as a selective high-affinity AKAP for type I PKA regulatory subunits (RI). Using cell-based reporters to map protein-protein interactions, we discovered that RI binds directly and selectively to a hydrophobic protein-protein interaction interface in the cytoplasmic carboxyl-terminal tail of Gpr161. Furthermore, our data demonstrate that a binary complex between Gpr161 and RI promotes the compartmentalization of Gpr161 to the plasma membrane. Moreover, we show that Gpr161, functioning as an AKAP, recruits PKA RI to primary cilia in zebrafish embryos. We also show that Gpr161 is a target of PKA phosphorylation, and that mutation of the PKA phosphorylation site affects ciliary receptor localization. Thus, we propose that Gpr161 is itself an AKAP and that the cAMP-sensing Gpr161:PKA complex acts as cilium-compartmentalized signalosome, a concept that now needs to be considered in the analyzing, interpreting, and pharmaceutical targeting of PKA-associated functions.interaction network | molecular interactions | scaffolding function | phosphorylation | primary cilium

The regulators of G protein signaling RGS16 and RGS18 inhibit protease‐activated receptor 2/Gi/o signaling through distinct interactions with Gα in live cells

“…PAR1 binds transforming growth factor b (TGF-b) receptor II (TGFR-bII) and inhibits dimerization of TGFR-bI/TGFR-bII, which leads to downregulation of TGF-b signaling and modulation of embryonic stem cell differentiation [12]. Gpr161, an orphan GPCR, contains a motif for A-kinase anchoring protein in its C-terminal tail and binds the regulatory subunits of PKA, leading to the modulation of cAMP signaling [13]. GPCRs interact directly or indirectly with RGS proteins as well as Ga. Adrenergic, muscarinic acetylcholine and opioid receptors have been identified as binding factors of RGS proteins [5].…”

Genome-wide CRISPR screening identifies new regulators of glycoprotein secretion

“…Our results showing that GPR161 is both localised to the Golgi and involved in regulation of Golgi morphology and glycoprotein traffic fit with this emerging idea that GPCRs can regulate protein trafficking. The BioPlex network for GPR161 shows an interaction with golgin A5, as well as with five PKA subunits 20,21 ; other work has also demonstrated an interaction between GPR161 and PKA 35 .…”

Androgen receptor-deficient islet β-cells exhibit alteration in genetic markers of insulin secretion and inflammation. A transcriptome analysis in the male mouse

“…These include genes coding for GPRs such as Gpr161 (Bachmann et al, 2016), Gpr126 (Mogha et al, 2013), Gpr26 (Zhang et al, 2011), ion channels altering membrane polarization like the potassium inwardly-rectifying channel, subfamily J, member 5 ( kcnj5 ), the potassium voltage-gated channel, subfamily Q, member 1 ( kcnq1 ) (33), and trpc4 (Islam, 2011), as well as proteins involved in β-cell exocytosis machinery such as the Ca(2+)-sensor synaptotagmin-10 ( Syt10 ) (Cao, Maximov, & Sudhof, 2011), the GTP binding protein rabphilin 3a ( Rph3a ) (Arribas, Regazzi, Garcia, Wollheim, & De Camilli, 1997), heparan sulfate (glucosamine) 3-O-sulfotransferase 1 ( Hs3st1 ) (Takahashi, Ohashi, & Nata, 2012) and enzymes involved in glucose metabolism, hexokinase 2 ( hk2 ), hexokinase domain containing 1 ( hkdc1 ) (Ludvik et al, 2016), glucokinase binding protein 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 ( Pfkfb3 ) (Arden et al, 2008) and zinc transport in βcells like the zinc transporter, member 4 ( Slc39a4 ) (Hardy et al, 2015). …”