Golgi localized β1-adrenergic receptors stimulate Golgi PI4P hydrolysis by PLCε to regulate cardiac hypertrophy

Abstract

Increased adrenergic tone resulting from cardiovascular stress leads to development of heart failure, in part, through chronic stimulation of b1 adrenergic receptors (bARs) on cardiac myocytes. Blocking these receptors is part of the basis for b-blocker therapy for heart failure. Recent data demonstrate that G protein-coupled receptors (GPCRs), including bARs, are activated intracellularly, although the biological significance is unclear. Here we investigated the functional role of Golgi bARs in cardiac myocytes and found they activate Golgi localized, prohypertrophic, phosphoinositide hydrolysis, that is not accessed by cell surface bAR stimulation. This pathway is accessed by the physiological neurotransmitter norepinephrine (NE) via an Oct3 organic cation transporter. Blockade of Oct3 or specific blockade of Golgi resident b1ARs prevents NE dependent cardiac myocyte hypertrophy. This clearly defines a physiological pathway activated by internal GPCRs in a biologically relevant cell type and has implications for development of more efficacious b-blocker therapies.

β-arrestin mediates communication between plasma membrane and intracellular GPCRs to regulate signaling

“…This result is inconsistent with the spare receptor model. Furthermore, in agreement with previous work 6,7,49 , this suggests that while cells often use some of the same signaling machinery, the localization of a signaling event can lead to different cellular responses. Since βarrestin-1 plays a role in activating internal CXCR4, we investigated whether inhibition Many new questions regarding the molecular mechanism and physiological relevance of plasma membrane and intracellular CXCR4 activation remain unanswered.…”

“…These observations may resolve the paradox that while CXCR4 overexpression is associated with metastatic potential, plasma membrane localization is not 22,23 . Additionally, this work supports a growing amount of evidence supporting that targeting specifically intracellular GPCR populations or the downstream signaling cascades activated by these pools might lead to improved therapeutic strategies for treating cancer, cardiovascular disease, and pain management 6,7,40 . HEK293T cells were obtained from ATCC and grown in DMEM (Corning) media supplemented with 10% FBS.…”

“…Over the last decade, we have learned that GPCR spatiotemporal signaling is one mechanism used by cells to translate diverse environmental information into actionable intracellular decisions while using seemingly redundant signaling cascades 1 . Extensive research has illustrated that GPCRs elicit distinct signaling events at different plasma membrane micro-domains as well as endocytic compartments that are important for cell physiology and disease pathogenesis [1][2][3][4][5][6][7][8][9] . These studies support a model where the location, in addition to magnitude, of a signaling event is important for cellular decision-making.…”

“…GPCR signaling at intracellular compartments has become increasingly apparent and has been shown to activate different signaling cascades compared to plasma membrane-localized counterparts 1,3,48,49 . Recent work has shown that activation of G protein signaling at the Golgi and endosomes regulates PI4P hydrolysis and PCK1 transcription respectively 7,49 .…”

“…Next, we focused on identifying the proteins responsible for agonist-dependent internal CXCR4 PTM. G proteins are master regulators for GPCR signaling and recent studies have revealed tight spatiotemporal regulation of G protein signaling events 6,7,45 . Upon ligand binding, G protein Gαi and Gβγ subunits are released from the GPCR due to guanidine exchange factor activity.…”