Protein Kinase C ζ Interacts with a Novel Binding Region of Gαq to Act as a Functional Effector

Abstract

Heterotrimeric G proteins play an essential role in the initiation of G protein-coupled receptor (GPCR) signaling through specific interactions with a variety of cellular effectors. We have recently reported that GPCR activation promotes a direct interaction between G␣q and protein kinase C (PKC), leading to the stimulation of the ERK5 pathway independent of the canonical effector PLC␤. We report herein that the activation-dependent G␣q/PKC complex involves the basic PB1-type II domain of PKC and a novel interaction module in G␣q different from the classical effector-binding site. Point mutations in this G␣q region completely abrogate ERK5 phosphorylation, indicating that G␣q/PKC association is required for the activation of the pathway. Indeed, PKC was demonstrated to directly bind ERK5 thus acting as a scaffold between G␣q and ERK5 upon GPCR activation. The inhibition of these protein complexes by G proteincoupled receptor kinase 2, a known G␣q modulator, led to a complete abrogation of ERK5 stimulation. Finally, we reveal that G␣q/ PKC complexes link G␣q to apoptotic cell death pathways. Our data suggest that the interaction between this novel region in G␣q and the effector PKC is a key event in G␣q signaling.

G Protein-Coupled Receptor Kinase 2 (GRK2) as a Potential Therapeutic Target in Cardiovascular and Metabolic Diseases

“…All GRKs are serine/threonine kinases that belong to the large AGC kinase family and share a catalytic domain displaying the characteristic bilobular fold of protein kinases, with high similarity to other AGC members, such as PKA, PKB, and PKC (Pearce et al., 2010). This catalytic core is preceded by a domain displaying homology to RGS proteins (thus termed RH domain) that, in the case of GRK2 subfamily members, has been shown to specifically interact with Gαq/11 subunits, thus blocking its interaction with their effectors (Carman et al., 1999; Sanchez-Fernandez et al., 2016). The RH domain displays at its far N-terminus a N-terminal helix (αN) characteristic of GRKs and important for receptor recognition.…”

Gαq activation modulates autophagy by promoting mTORC1 signaling

“…Gαq and p62 appear to associate through a PB1-like interaction, involving the PB1 domain of p62 and the acidic PB1-binding region of Gαq, different from the specific interface involved in the association of Gαq with the canonical PLCβ or p63RhoGEF effectors 19 . This acidic Gαq region has been shown to interact with the PB1 domain of PKCζ 29 or with the cold-activated channel TRPM8 42 , consistent with this Gαq region being a functional module. Our data suggest that key Gαq acidic residues such as E234/E245 would engage in specific electrostatic interactions with canonical type II (positively charged) PB1 domains such as that present in p62.…”

“…6a ), suggesting that an additional effector binding through a different region was involved in Gαq-dependent mTORC1 modulation. A novel acidic region in Gαq responsible for its direct interaction with the PB1-containing protein Protein kinase C ζ (PKCζ) has been reported, and glutamic acid residues 234 and 245 proven to be critical for such interaction 29 . Remarkably, the stimulation of the mTORC1 pathway triggered by transient expression of Gαq WT in low-serum conditions was not mimicked upon overexpression of the Gq-EEAA mutant (Fig.…”

“…The Gαq mutant proteins that lack the ability to interact with GRK2 (Gαq-T257E, W263D, Y261F) were a gift from Dr. T. Kozasa (The University of Tokyo, Japan). The PB1-binding region Gαq mutants (Gαq E234A, D236A, D243A, E245A, E234/E245-AA, Gq-R183C-E234/E245-AA) were generated in our laboratory using the QuickChange® site-directed mutagenesis kit (Stratagene) following the manufacturer’s instructions 29 . GRK2, GRK2-K220R, GRK2-D110A cDNAs were a gift from Dr. J. L. Benovic (The Kimmel Cancer Center, USA).…”

Identifying and Analyzing Novel Epilepsy-Related Genes Using Random Walk with Restart Algorithm

“…Two of our predicted candidates, PRKCA and PRKCG, can be clustered into another functional family, the family of serine- and threonine-specific protein kinases. Such two genes turn out to be functional components of the protein kinase C, a core member of the protein family we mentioned above [ 77 – 79 ]. The protein kinase C associated signaling pathway has been widely reported to be associated with epilepsy and may be a candidate therapeutic target for such disease [ 80 ].…”