scholarly journals Junctophilin-4 is essential for signalling at plasma membrane-endoplasmic reticulum junctions in sensory neurons

2019 ◽  
Author(s):  
Alexandra Hogea ◽  
Shihab Shah ◽  
Frederick Jones ◽  
Chase M Carver ◽  
Han Hao ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
G Protein ◽  
Sensory Neurons ◽  
Inflammatory Pain ◽  
Pain Mechanisms ◽  
Excitatory Action ◽  
Peripheral Sensory ◽  
G Protein Coupled

AbstractJunctions of endoplasmic reticulum and plasma membrane (ER-PM junctions) serve as signaling hubs in prokaryotic cells. ER-PM junctions are present in peripheral sensory neurons and are necessary for pro-inflammatory G protein coupled receptor signalling and for inflammatory pain generation. Yet, the principles of ER-PM junctions assembly and maintenance, as well as their role in inflammatory signaling in sensory neurons are only beginning to emerge. Here we discovered that a member of the junctophilin family of proteins, JPH4, is abundantly expressed in rat dorsal root ganglion (DRG) neurons and is necessary for the formation of store operated Ca2+ entry (SOCE) complex at the ER-PM junctions in response to the G-protein induced ER Ca2+ store depletion. Furthermore, we demonstrate a key role of the JPH4 and ER Ca2+ stores in the maintenance of inflammatory pain. Indeed, knockdown of JPH4 expression in DRG in vivo significantly reduced the duration of pain produced by inflammatory mediator bradykinin. Since the ER supplies Ca2+ for the excitatory action of multiple inflammatory mediators, we suggest that junctional Ca2+ signalling maintained by JPH4 is an important contributor to the inflammatory pain mechanisms.

scholarly journals MRGPRX4 is a G protein-coupled receptor activated by bile acids that may contribute to cholestatic pruritus

2019 ◽  
Vol 116 (21) ◽  
pp. 10525-10530 ◽  
Author(s):  
James Meixiong ◽  
Chirag Vasavda ◽  
Solomon H. Snyder ◽  
Xinzhong Dong
Keyword(s):  
Bile Acids ◽  
G Protein ◽  
Sensory Neurons ◽  
G Protein Coupled Receptor ◽  
Humanized Mouse ◽  
Chronic Itch ◽  
Targeted Expression ◽  
Acute Injection ◽  
G Protein Coupled

Patients suffering from cholestasis, the slowing or stoppage of bile flow, commonly report experiencing an intense, chronic itch. Numerous pruritogens are up-regulated in cholestatic patient sera, including bile acids (BAs). Acute injection of BAs results in itch in both mice and humans, and BA-modulating therapy is effective in controlling patient itch. Here, we present evidence that human sensory neuron-expressed Mas-related G protein-coupled receptor X4 (MRGPRX4), an orphan member of the Mrgpr family of GPCRs, is a BA receptor. Using Ca2+ imaging, we determined that pathophysiologically relevant levels of numerous BAs activated MRGPRX4. No mouse Mrgpr orthologs were activated by BAs. To assess the in vivo relevance of BA activation of MRGPRX4, we generated a humanized mouse with targeted expression of MRGPRX4 in itch-encoding sensory neurons. BAs activated MRGPRX4+ sensory neurons at higher levels compared with WT neurons. Compared with control animals, MRGPRX4+ mice scratched more upon acute injection of BAs and in a model of cholestatic itch. Overall, these data suggest that targeting MRGPRX4 is a promising strategy for alleviating cholestatic itch.

scholarly journals A striatal-enriched intronic GPCR modulates huntingtin levels and toxicity

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Yuwei Yao ◽  
Xiaotian Cui ◽  
Ismael Al-Ramahi ◽  
Xiaoli Sun ◽  
Bo Li ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
G Protein ◽  
Neurodegenerative Disorders ◽  
Treatment Strategies ◽  
Mutant Huntingtin ◽  
Potential Treatment ◽  
Mutant Huntingtin Protein ◽  
G Protein Coupled

Huntington's disease (HD) represents an important model for neurodegenerative disorders and proteinopathies. It is mainly caused by cytotoxicity of the mutant huntingtin protein (Htt) with an expanded polyQ stretch. While Htt is ubiquitously expressed, HD is characterized by selective neurodegeneration of the striatum. Here we report a striatal-enriched orphan G protein-coupled receptor(GPCR) Gpr52 as a stabilizer of Htt in vitro and in vivo. Gpr52 modulates Htt via cAMP-dependent but PKA independent mechanisms. Gpr52 is located within an intron of Rabgap1l, which exhibits epistatic effects on Gpr52-mediated modulation of Htt levels by inhibiting its substrate Rab39B, which co-localizes with Htt and translocates Htt to the endoplasmic reticulum. Finally, reducing Gpr52 suppresses HD phenotypes in both patient iPS-derived neurons and in vivo Drosophila HD models. Thus, our discovery reveals modulation of Htt levels by a striatal-enriched GPCR via its GPCR function, providing insights into the selective neurodegeneration and potential treatment strategies.

scholarly journals SAT-LB137 Rescue of Misfolded G-Protein Coupled Estrogen Receptor, GPER, from the Endoplasmic Reticulum via Natural and Synthetic Estrogens

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Milad Rouhimoghadam ◽  
Jing Dong ◽  
Peter Thomas ◽  
Edward Joseph Filardo
Keyword(s):  
Quality Control ◽  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Cell Surface ◽  
G Protein ◽  
Surface Expression ◽  
Membrane Expression ◽  
Plasma Membrane Expression ◽  
17Β Estradiol ◽  
G Protein Coupled

Abstract GPER bears structural and functional characteristics shared by members of the G-protein coupled receptor (GPCR) superfamily, the largest class of cell surface receptors, with more than 800 members encoded in the human genome. GPER is localized predominately in intracellular membranes, in many but not all cell types, and its surface expression is modulated by steroid hormones and during tissue homeostasis. An intracellular staining pattern is not unique among GPCRs, which deploy a diverse array of posttranslational regulatory mechanisms to determine cell surface expression, effectively regulating cognate ligand binding and activity. Here, we show nascent GPER undergoes strict quality control via endoplasmic reticulum associated degradation (ERAD) requiring direct poly-ubiquitinylation of GPER and valosin-containing protein VCP/p97-mediated segregation of misfolded proteins from the ER membrane to the cytoplasm for delivery to the 26S proteasome. Specifically, we find that inhibition of p97 using the pharmacological compound, CB-5083, or by doxycycline-inducible p97 shRNA results in the accumulation of immature glycosylated GPER in the ER. Inhibition of proteasome function facilitates anterograde trafficking with the transport of nonfunctional GPER to the plasma membrane as indicated by no increase in specific estrogen binding using 3H-17β-estradiol in a radioreceptor assay. The forward trafficking of misfolded GPER requires transit through the Golgi as treatment with brefeldin A (BFA) prevents GPER plasma membrane expression. Substitution of all three lysines (K333, K342, and K357) encoded in the cytoplasmic tail of GPER with arginines blunts its polyubiquitinylation and allows GPER to evade degradation by quality control but does not result in increased plasma membrane expression suggesting that additional structural motifs encoded within GPER control its anterograde trafficking. In contrast, functional GPER is recovered at the plasma membrane of human SKBR3 breast cancer cells treated with either 17β-estradiol or the GPER selective antagonist, G15, in the presence of cycloheximide resulting in increased surface GPER. Thus, our findings suggest that estrogens, both natural and synthetic, can function as pharmacochaperones capable of promoting the correct folding of GPER and enhanced expression of functional GPER at the plasma membrane.

Rab1 interacts directly with the β2-adrenergic receptor to regulate receptor anterograde trafficking

2012 ◽  
Vol 393 (6) ◽  
pp. 541-546 ◽  
Author(s):  
Maha M. Hammad ◽  
Yi-Qun Kuang ◽  
Alexa Morse ◽  
Denis J. Dupré
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
G Protein ◽  
Adrenergic Receptor ◽  
Direct Interaction ◽  
Potential Interaction ◽  
G Protein Coupled Receptors ◽  
Endocytic Pathway ◽  
Β2 Adrenergic Receptor ◽  
G Protein Coupled

Abstract Very little is understood about the trafficking of G protein-coupled receptors (GPCRs) from the endoplasmic reticulum (ER) to the plasma membrane. Rab guanosine triphosphatases (GTPases) are known to participate in the trafficking of various GPCRs via a direct interaction during the endocytic pathway, but whether this occurs in the anterograde pathway is unknown. We evaluated the potential interaction of Rab1, a GTPase known to regulate β2-adrenergic receptor (β2AR) trafficking, and its effect on export from the ER. Our results show that GTP-bound Rab1 interacts with the F(x)6LL motif of β2AR. Receptors lacking the interaction motif fail to traffic properly, suggesting that a direct interaction with Rab1 is required for β2AR anterograde trafficking.

scholarly journals The G protein–coupled receptor GPR31 promotes membrane association of KRAS

2017 ◽  
Vol 216 (8) ◽  
pp. 2329-2338 ◽  
Author(s):  
Nicole Fehrenbacher ◽  
Israel Tojal da Silva ◽  
Craig Ramirez ◽  
Yong Zhou ◽  
Kwang-Jin Cho ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Tumor Cells ◽  
G Protein ◽  
Secretory Pathway ◽  
Membrane Association ◽  
G Protein Coupled Receptor ◽  
Genome Wide ◽  
A Genome ◽  
G Protein Coupled

The product of the KRAS oncogene, KRAS4B, promotes tumor growth when associated with the plasma membrane (PM). PM association is mediated, in part, by farnesylation of KRAS4B, but trafficking of nascent KRAS4B to the PM is incompletely understood. We performed a genome-wide screen to identify genes required for KRAS4B membrane association and identified a G protein–coupled receptor, GPR31. GPR31 associated with KRAS4B on cellular membranes in a farnesylation-dependent fashion, and retention of GPR31 on the endoplasmic reticulum inhibited delivery of KRAS4B to the PM. Silencing of GPR31 expression partially mislocalized KRAS4B, slowed the growth of KRAS-dependent tumor cells, and blocked KRAS-stimulated macropinocytosis. Our data suggest that GPR31 acts as a secretory pathway chaperone for KRAS4B.

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