Affinage

GPR174

Probable G-protein coupled receptor 174 · UniProt Q9BXC1

Length
333 aa
Mass
38.5 kDa
Annotated
2026-04-28
23 papers in source corpus 14 papers cited in narrative 14 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

GPR174 is an X-linked class A GPCR that functions as a lysophosphatidylserine (LysoPS) receptor to regulate immune cell activation, differentiation, and positioning. LysoPS binds GPR174 via a lateral portal between TM4 and TM5, with its L-serine head group inserting into a positively charged sub-cavity, and the receptor couples primarily to Gαs to elevate cAMP, activating PKA-dependent signaling that suppresses IL-2 production and T cell activation, constrains regulatory T cell generation and function, and controls amphiregulin expression through the cAMP/PKA→EGR1→AREG axis (PMID:23178570, PMID:26077720, PMID:29457279, PMID:36473866, PMID:36823105). GPR174 also responds to CCL21 to direct B cell positioning toward the T–B border, associates with Gαi in a testosterone-dependent manner in male B cells, and thereby suppresses germinal center formation, imparting sexual dimorphism to humoral immunity (PMID:31875850). Cryo-EM structures reveal that GPR174 exhibits high constitutive Gαs activity due to co-purified endogenous LysoPS and employs a non-canonical Gs coupling mode involving deep insertion of the αH5 helix and a hydration-mediated signaling network linking the sodium-binding pocket to the G protein interface (PMID:36823105, PMID:37737235, PMID:38048360).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 2012 High

    Establishing that GPR174 is not an orphan receptor but a constitutively active Gαs-coupled GPCR activated by LysoPS resolved its basic signaling identity and linked it to lipid-mediated signaling.

    Evidence Stable expression in CHO cells with cAMP measurement, Erk phosphorylation assay, and pharmacological Gαs blockade with NF449

    PMID:23178570

    Open questions at the time
    • Physiological context of LysoPS–GPR174 signaling unknown
    • No in vivo functional data
    • Structural basis of LysoPS recognition unresolved
  2. 2015 High

    Demonstrating that GPR174 constrains regulatory T cell generation in thymus and periphery established its first immunological function and linked LysoPS sensing to immune homeostasis.

    Evidence Gpr174 knockout mice with flow cytometry, in vitro Treg differentiation assays, and EAE disease model

    PMID:26077720

    Open questions at the time
    • Downstream signaling pathway in Tregs not delineated
    • Mechanism by which LysoPS suppresses Treg generation not defined
    • Ligand SAR for GPR174-specific tools still developing
  3. 2015 High

    Systematic SAR of synthetic LysoPS analogues defined the pharmacophore requirements for GPR174 selectivity versus related receptors GPR34 and P2Y10, enabling future tool compound development.

    Evidence Synthetic analogue screening with functional GPCR subtype-selective assays

    PMID:25970039

    Open questions at the time
    • No high-affinity selective antagonist developed
    • In vivo utility of analogues not tested
  4. 2017 High

    Showing that LysoPS suppresses IL-2 production specifically through GPR174 in activated CD4+ T cells identified the key cytokine output controlled by this receptor during T cell activation.

    Evidence Gpr174 KO splenocytes and CD4+ T cells, qPCR and ELISA for IL-2

    PMID:29017923

    Open questions at the time
    • G protein coupling requirement not yet confirmed for IL-2 suppression
    • Transcription factor targets downstream of GPR174 in T cells unknown
  5. 2018 High

    Confirming that Gαs is the required coupling partner for GPR174-mediated suppression of IL-2, CD25, and CD69 on T cells established the proximal signaling mechanism and its in vivo relevance for controlling T cell proliferation.

    Evidence Gpr174 KO mice with in vitro Gαs inhibition, in vivo irradiation and Treg depletion models

    PMID:29457279

    Open questions at the time
    • Downstream effectors of Gαs/cAMP in T cells not fully mapped
    • Whether Gαi coupling occurs in T cells untested
  6. 2019 High

    Identification of CCL21 as a second GPR174 ligand, and the discovery that GPR174 couples to Gαi in a testosterone-dependent manner in B cells to suppress germinal center formation, revealed a mechanism for sexual dimorphism in humoral immunity.

    Evidence Biochemical fractionation of conditioned media, calcium flux, B cell migration, Co-IP of GPR174–Gαi, orchidectomy/testosterone treatment, conditional KO mice with intravital imaging

    PMID:31875850

    Open questions at the time
    • Structural basis for CCL21 recognition by GPR174 unknown
    • Mechanism of testosterone-dependent Gαi coupling preference unresolved
    • Whether CCL21 and LysoPS compete or cooperate at the receptor unclear
  7. 2019 Medium

    Demonstrating that GPR174-deficient Tregs upregulate CTLA-4 and IL-10 and promote M2 macrophage polarization extended the receptor's function to the Treg–macrophage axis and sepsis protection.

    Evidence Gpr174 KO mice in LPS and CLP sepsis models, flow cytometry, ELISA, co-culture assays

    PMID:30850582

    Open questions at the time
    • Signaling pathway linking GPR174 to CTLA-4/IL-10 upregulation not delineated
    • Single-lab finding in sepsis models
  8. 2022 High

    Mapping the Gαs/cAMP/PKA→EGR1→AREG signaling axis in Tregs resolved how GPR174 constrains tissue-repair functions and connected GPR174 to endothelial recovery and macrophage reprogramming after ischemia.

    Evidence Conditional Treg KO, hindlimb ischemia model, nuclear-cytoplasmic fractionation, cAMP/PKA assays, EGR1 ChIP/reporter assays, AREG ELISA

    PMID:36473866

    Open questions at the time
    • Whether EGR1–AREG axis operates in other GPR174-expressing immune cells unknown
    • Direct binding of EGR1 to AREG promoter in primary Tregs not shown by ChIP-seq
  9. 2023 High

    Cryo-EM structures of LysoPS-bound GPR174–Gs complex revealed the atomic basis of LysoPS recognition (lateral TM4–TM5 entry, positively charged sub-cavity for L-serine head group) and non-canonical Gs coupling, establishing the structural framework for drug design.

    Evidence Cryo-EM structure determination by three independent groups with mutagenesis validation and signaling assays

    PMID:36823105 PMID:37737235 PMID:38048360

    Open questions at the time
    • No GPR174–Gi structure from peer-reviewed source
    • Structural basis of CCL21 binding unresolved
    • No co-crystal with antagonist available
  10. 2025 Medium

    Extension of GPR174 signaling to the cAMP–PKA–CREB axis in esophageal squamous cell carcinoma showed the receptor promotes invasion and metastasis, indicating a pathological role beyond immune regulation.

    Evidence LC-MS, Western blotting, nuclear fractionation, Transwell/wound healing assays, GPR174 overexpression, nude mouse metastasis model

    PMID:40229851

    Open questions at the time
    • Single cancer type examined
    • No genetic loss-of-function in the tumor model
    • Clinical relevance of GPR174 expression in cancer not established

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include the structural basis of CCL21 recognition by GPR174, the molecular mechanism of testosterone-dependent Gαi versus Gαs coupling bias, whether selective GPR174 antagonists can be developed for therapeutic use, and the in vivo relevance of GPR174 in human autoimmunity and cancer.
  • No selective GPR174 antagonist with in vivo efficacy reported
  • No human genetic studies linking GPR174 variants to disease phenotypes in the timeline
  • Mechanism of biased G protein coupling by sex hormones unresolved

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0008289 lipid binding 3 GO:0060089 molecular transducer activity 2
Localization
GO:0005886 plasma membrane 3
Pathway
R-HSA-162582 Signal Transduction 5 R-HSA-168256 Immune System 5 GO:0005886 plasma membrane 1
Partners
AREGCCL21EGR1GNAI1GNAS

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2012 GPR174 is a constitutively active Gαs-coupled receptor; its expression in CHO cells elevates intracellular cAMP and induces morphological changes and proliferation delay. Lysophosphatidylserine (LysoPS) was identified as a ligand that further stimulates cAMP increase and Erk phosphorylation, both inhibited by the Gαs inhibitor NF449. Stable expression in CHO cells, intracellular cAMP measurement, Erk phosphorylation assay, pharmacological inhibition with NF449 Biochemical and biophysical research communications High 23178570
2015 GPR174 is abundantly expressed in regulatory T (Treg) cells and constrains Treg generation in the thymus and peripheral CD103+ Treg accumulation. LysoPS acting via GPR174 suppresses T cell proliferation and Treg generation in vitro, and GPR174 deficiency in Treg cells reduces EAE susceptibility in vivo. Gpr174 knockout mice, flow cytometry, in vitro proliferation assays, EAE model, adoptive transfer The Journal of experimental medicine High 26077720
2015 Structure-activity relationships of synthetic LysoPS analogues established that specific structural modules (fatty acid, glycerol, L-serine head group) are required for potency and selectivity at GPR174 (LPS3) versus GPR34 and P2Y10, identifying GPR174 as a LysoPS-specific GPCR within a receptor family. Synthetic LysoPS analogue screening, functional GPCR assays for receptor subtype selectivity Journal of medicinal chemistry High 25970039
2017 GPR174 (LPS3) mediates LysoPS-induced suppression of IL-2 production at the mRNA and protein levels in activated CD4+ T cells; this suppressive effect is absent in Gpr174-deficient splenocytes and CD4+ T cells, and LysoPS species are upregulated upon T cell activation. Gpr174 knockout mice, qPCR, ELISA, in vitro T cell activation assays Biochemical and biophysical research communications High 29017923
2018 LysoPS-mediated suppression of T cell activation via GPR174 requires Gαs proteins; mechanistically, GPR174/Gαs signaling suppresses IL-2 production and limits upregulation of CD25 and CD69 on activated T cells. In vivo, GPR174 constrains T cell proliferation induced by sublethal irradiation or Treg depletion. Gpr174 KO mice, in vitro Gαs inhibition, in vivo T cell proliferation models (irradiation, Treg depletion), flow cytometry, ELISA Immunology and cell biology High 29457279
2019 CCL21 is a GPR174 ligand identified by biochemical fractionation of conditioned media. GPR174 responds to CCL21 by triggering calcium flux and inducing B cell migration. GPR174 associates preferentially with Gαi in male B cells in a testosterone-dependent manner, and GPR174 suppresses germinal center formation by positioning B cells toward the T-B border rather than the follicle center. Biochemical fractionation of conditioned media, calcium flux assay, B cell migration assay, Co-immunoprecipitation (GPR174–Gαi), orchidectomy/testosterone treatment, Gpr174 conditional KO mice, intravital imaging/histology Nature High 31875850
2019 GPR174 deficiency in Treg cells promotes CTLA-4 and IL-10 expression, and Gpr174-deficient Tregs promote M2 macrophage polarization while dampening pro-inflammatory cytokines (IL-6, TNF-α), thereby protecting mice from LPS- and CLP-induced septic shock. Gpr174 KO mice, LPS and CLP sepsis models, flow cytometry, ELISA, in vitro macrophage polarization co-culture assays Cell death & disease Medium 30850582
2022 GPR174 deficiency in Tregs upregulates amphiregulin (AREG) expression by inhibiting nuclear accumulation of EGR1 via the Gαs/cAMP/PKA signaling pathway, enhancing endothelial cell function and reducing pro-inflammatory macrophage polarization to promote blood flow recovery after hindlimb ischemia. Gpr174 conditional KO in Tregs, hindlimb ischemia model, nuclear-cytoplasmic fractionation, cAMP/PKA pathway assays, AREG ELISA, EGR1 ChIP/reporter assays Nature communications High 36473866
2023 Cryo-EM structure of LysoPS-bound human GPR174 in complex with Gs protein reveals: (1) the negatively charged LysoPS head group makes extensive polar interactions with key pocket residues; (2) the L-serine moiety inserts into a positively charged sub-cavity; (3) ligand enters via a partially open lateral portal between TM4 and TM5; (4) Gs is engaged via deep insertion of the αH5 helix with extensive polar interactions. Cryo-EM structure determination, mutagenesis-based functional validation Nature communications High 36823105
2023 GPR174 exhibits high constitutive Gαs/cAMP activity due to copurification of endogenous LysoPS. Cryo-EM structures of ligand-free GPR174-Gs complex were determined. GPR174 mutants with reduced LysoPS affinity respond dose-dependently to exogenous LysoPS but not other lipids, confirming LysoPS selectivity. GPR174 adopts a non-canonical Gs coupling mode. Cryo-EM without exogenous ligand, cAMP activity assays, affinity-reducing mutant rescue assays, lipid specificity assays Nature communications High 37737235
2023 Cryo-EM structures of human GPR34 and GPR174 in complex with LysoPS and G protein elucidated distinct lipid-binding modes for these two receptors and structural features of their active states, providing a comparative framework for LysoPS receptor signaling and drug design. Cryo-EM structure determination, functional validation by mutagenesis and signaling assays PLoS biology High 38048360
2025 LysoPS/GPR174 signaling activates the cAMP-PKA-CREB pathway in esophageal squamous cell carcinoma cells: LysoPS stimulates GPR174 expression, GPR174 increases cAMP, active PKA translocates to the nucleus and phosphorylates CREB, promoting invasion and metastasis in vitro and in vivo. LC-MS for LysoPS quantification, Western blotting, nuclear-cytoplasmic fractionation, wound healing/Transwell assays, GPR174 overexpression, nude mouse metastasis model Journal of translational medicine Medium 40229851
2025 Molecular dynamics simulations of GPR174 bound to an antagonist (mPS) versus LysoPS reveal that LysoPS engages conserved activation motifs (PIF, DRY, N/DPxxY) to couple the ligand-binding site to the G-protein interface via lateral membrane entry, whereas mPS disrupts these pathways and reduces conformational dynamics. Membrane lipids including PIP2 modulate ligand dynamics and receptor conformational states. Molecular dynamics simulations, network analysis, protein-lipid interaction analysis bioRxivpreprint Low 41000684
2025 High-resolution cryo-EM structures of LysoPS-activated GPR174 bound to Gs (2.0 Å) and Gi (3.4 Å) reveal a continuous hydration-mediated signaling transduction network bridging the sodium-binding pocket, NPxxY and DRY motifs, and the G protein-binding interface. This hydration network stabilizes the active state and enables differential Gs and Gi engagement. Molecular dynamics and functional assays confirmed the hydration network is essential for activation and G protein selectivity. Cryo-EM structure determination (2.0 Å and 3.4 Å), molecular dynamics simulations, functional signaling assays bioRxivpreprint Medium bio_10.1101_2025.10.06.680656

Source papers

Stage 0 corpus · 23 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2019 A GPR174-CCL21 module imparts sexual dimorphism to humoral immunity. Nature 92 31875850
2015 The lysophosphatidylserine receptor GPR174 constrains regulatory T cell development and function. The Journal of experimental medicine 67 26077720
2013 An X chromosome-wide association analysis identifies variants in GPR174 as a risk factor for Graves' disease. Journal of medical genetics 51 23667180
2019 Gpr174-deficient regulatory T cells decrease cytokine storm in septic mice. Cell death & disease 45 30850582
2015 Structure-activity relationships of lysophosphatidylserine analogs as agonists of G-protein-coupled receptors GPR34, P2Y10, and GPR174. Journal of medicinal chemistry 42 25970039
2017 Lysophosphatidylserine suppresses IL-2 production in CD4 T cells through LPS3/GPR174. Biochemical and biophysical research communications 41 29017923
2018 Lysophosphatidylserine suppression of T-cell activation via GPR174 requires Gαs proteins. Immunology and cell biology 37 29457279
2022 GPR174 knockdown enhances blood flow recovery in hindlimb ischemia mice model by upregulating AREG expression. Nature communications 31 36473866
2015 Role of the X-linked gene GPR174 in autoimmune Addison's disease. The Journal of clinical endocrinology and metabolism 28 25295623
2012 Expression of orphan G-protein coupled receptor GPR174 in CHO cells induced morphological changes and proliferation delay via increasing intracellular cAMP. Biochemical and biophysical research communications 25 23178570
2023 Structural basis of lysophosphatidylserine receptor GPR174 ligand recognition and activation. Nature communications 24 36823105
2022 Gpr174 Knockout Alleviates DSS-Induced Colitis via Regulating the Immune Function of Dendritic Cells. Frontiers in immunology 23 35669778
2013 rs3827440, a nonsynonymous single nucleotide polymorphism within GPR174 gene in X chromosome, is associated with Graves' disease in Polish Caucasian population. Tissue antigens 22 24289805
2023 Specific binding of GPR174 by endogenous lysophosphatidylserine leads to high constitutive Gs signaling. Nature communications 15 37737235
2019 GPR174 suppression attenuates retinopathy in angiotensin II (Ang II)-treated mice by reducing inflammation via PI3K/AKT signaling. Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie 14 31918274
2019 The increased marginal zone B cells attenuates early inflammatory responses during sepsis in Gpr174 deficient mice. International immunopharmacology 11 31786099
2023 Structural basis for ligand recognition and signaling of the lysophosphatidylserine receptors GPR34 and GPR174. PLoS biology 10 38048360
2020 GPR174 and ITM2A Gene Polymorphisms rs3827440 and rs5912838 on the X chromosome in Korean Children with Autoimmune Thyroid Disease. Genes 10 32727090
2017 RNASET2, GPR174, and PTPN22 gene polymorphisms are related to the risk of liver damage associated with the hyperthyroidism in patients with Graves' disease. Journal of clinical laboratory analysis 10 28568286
2012 Genetic map of lps3: a new short petiole gene in soybeans. Genome 8 22276917
2022 Activation of CCL21-GPR174/CCR7 on cardiac fibroblasts underlies myocardial ischemia/reperfusion injury. Frontiers in genetics 3 36159993
2025 The LysoPS/GPR174 axis drives metastatic progression in esophageal squamous cell carcinoma through cAMP-PKA-CREB signaling activation. Journal of translational medicine 1 40229851
2025 GPR174 Antagonism: Structure, Function, and Dynamics. bioRxiv : the preprint server for biology 0 41000684