Functionally distinct and selectively phosphorylated GPCR subpopulations co-exist in a single cell

Abstract

G protein-coupled receptors (GPCRs) transduce pleiotropic intracellular signals in a broad range of physiological responses and disease states. Activated GPCRs can undergo agonist-induced phosphorylation by G protein receptor kinases (GRKs) and second messenger-dependent protein kinases such as protein kinase A (PKA). Here, we characterize spatially segregated subpopulations of β2-adrenergic receptor (β2AR) undergoing selective phosphorylation by GRKs or PKA in a single cell. GRKs primarily label monomeric β2ARs that undergo endocytosis, whereas PKA modifies dimeric β2ARs that remain at the cell surface. In hippocampal neurons, PKA-phosphorylated β2ARs are enriched in dendrites, whereas GRK-phosphorylated β2ARs accumulate in soma, being excluded from dendrites in a neuron maturation-dependent manner. Moreover, we show that PKA-phosphorylated β2ARs are necessary to augment the activity of L-type calcium channel. Collectively, these findings provide evidence that functionally distinct subpopulations of this prototypical GPCR exist in a single cell.

Postsynaptic localization and regulation of AMPA receptors and Cav1.2 by β2 adrenergic receptor/PKA and Ca 2+ /CaMKII signaling

“…Obviously, displacement of the β 2 AR from Ca v 1.2 would create a situation during which the β 2 AR could easily be endocytosed although endocytosis does not contribute to the refractory period of Ca v 1.2 regulation by β 2 AR stimulation (Patriarchi et al, ). Furthermore, most recent work now shows that GRKs phosphorylate only β 2 AR monomers while the β 2 ARs in Ca v 1.2 complexes are dimers and those dimers are only phosphorylated by PKA (Shen et al, ). The PKA phosphorylation sites are different from the GRK sites.…”

“…The PKA phosphorylation sites are different from the GRK sites. Only GRK‐ but not PKA‐phosphorylated β 2 ARs undergo endocytosis (Shen et al, ) (see also Staus et al, ), suggesting that Ca v 1.2‐associated β 2 ARs are not destined for endocytosis. Finally, phosphorylation of not only Ca v 1.2 itself on S1928 but also the β 2 ARs on its PKA sites S261/S262 is required for upregulation of Ca v 1.2 activity by β 2 AR signaling (Shen et al, ).…”

“…ª 2018 The Authors The EMBO Journal 37: e99771 | 2018 regulation by b 2 AR stimulation (Patriarchi et al, 2016). Furthermore, most recent work now shows that GRKs phosphorylate only b 2 AR monomers while the b 2 ARs in Ca v 1.2 complexes are dimers and those dimers are only phosphorylated by PKA (Shen et al, 2018). The PKA phosphorylation sites are different from the GRK sites.…”

Free fatty acid receptor 4 agonists induce lysophosphatidic acid receptor 1 (LPA1) desensitization independent of LPA1 internalization and heterodimerization

“…These data suggest the involvement of different internalization processes and that these receptors might move to different cellular locations (i. e., different endosomal compartments). There is already published information indicating that GPCRs might internalize into different compartments under different conditions (see, for example and references therein).…”

“…These data suggest the involvement of different internalization processes and that these receptors might move to different cellular locations (i. e., different endosomal compartments). There is already published information indicating that GPCRs might internalize into different compartments under different conditions (see, for example [54,55] and references therein). Hetero-dimerization of GPCRs has been observed with increasing frequency and there is evidence that these receptor-receptor interactions can modify their signaling, pharmacological properties and cellular localization [27,28].…”