G-1 (CAS 881639-98-1): Selective GPR30 Agonist for Cardiovascular and Oncology Research

Executive Summary: G-1 (CAS 881639-98-1) is a potent, selective agonist for the G protein-coupled estrogen receptor GPR30 (GPER1) with a Ki of ~11 nM, exhibiting negligible activity on classical estrogen receptors ERα and ERβ at micromolar concentrations (APExBIO). Activation of GPR30 by G-1 rapidly elevates intracellular calcium (EC50 = 2 nM) and induces PI3K-dependent nuclear PIP3 accumulation, modulating downstream signaling (Wang et al., 2021). In vitro, G-1 inhibits migration of breast cancer cell lines SKBr3 and MCF7 at nanomolar IC50, demonstrating functional selectivity. Chronic G-1 administration in heart failure models reduces cardiac fibrosis and improves contractile function by modulating β-adrenergic receptor expression. G-1’s molecular properties (C21H18BrNO3, MW 412.28) and high DMSO solubility enable reliable use in preclinical workflows.

Biological Rationale

GPR30 (GPER1) is a G protein-coupled receptor located primarily on the endoplasmic reticulum membrane. It mediates rapid, non-genomic estrogen signaling distinct from classical ERα and ERβ pathways (Wang et al., 2021). Endogenous GPR30 ligands include estradiol and aldosterone. GPR30 is implicated in cardiovascular homeostasis, immune modulation, and cancer cell migration. Unlike ERα/β, GPR30 activation leads to unique downstream effects such as rapid calcium mobilization and PI3K/Akt pathway activation. G-1 allows researchers to dissect GPR30-specific effects, eliminating confounding from nuclear ERs. This specificity is vital in studying disease models where estrogen signaling is pleiotropic, such as heart failure, immune dysfunction, and breast cancer metastasis.

Mechanism of Action of G-1 (CAS 881639-98-1), a selective GPR30 agonist

G-1 is a non-steroidal, small molecule agonist with high affinity for GPR30 (Ki ≈ 11 nM) and minimal activity on ERα and ERβ (no effect up to micromolar concentrations) (APExBIO). Upon binding, G-1 triggers GPR30-mediated G protein signaling, resulting in:

• Elevation of intracellular Ca²⁺ (EC50 = 2 nM) within minutes.
• PI3K activation and nuclear accumulation of PIP3, modulating downstream kinase cascades.
• Regulation of β-adrenergic receptor expression in cardiac tissue, including normalization of β1-AR and upregulation of β2-AR (Wang et al., 2021).
• Inhibition of cell migration in specific cancer cell lines (SKBr3, MCF7) via GPR30-dependent signaling.

G-1’s selectivity is confirmed by the lack of effect in cells lacking GPR30 or in the presence of GPR30 antagonists (e.g., G15). This enables clear attribution of observed phenotypes to GPR30 activation, as opposed to classical ER signaling.

Evidence & Benchmarks

• G-1 binds GPR30 with a Ki of ~11 nM; negligible activity at ERα/ERβ up to 1 μM (APExBIO).
• G-1 (EC50 = 2 nM) elevates intracellular calcium in GPR30-expressing cells (Wang et al., 2021).
• In vitro migration inhibition: IC50 = 0.7 nM (SKBr3), 1.6 nM (MCF7) (APExBIO).
• Chronic G-1 (120 μg/kg/day, 14 days) reduces brain natriuretic peptide, inhibits cardiac fibrosis, and normalizes cardiac β-adrenergic receptors in ovariectomized rat heart failure model (Wang et al., 2021).
• Beneficial immune modulation by G-1 is abolished by GPR30 antagonism (G15), confirming pathway specificity (Wang et al., 2021).

This article extends on previous mechanistic explorations by providing new quantitative benchmarks and clarifying tissue-specific effects of G-1. For a detailed workflow comparison, see our deep-dive on immune modulation; this article updates with the latest cardiovascular findings. For best-practice assay guidance, consult APExBIO’s technical workflow guide—this dossier provides stepwise parameters and pitfalls for translational users.

Applications, Limits & Misconceptions

G-1 is validated for:

• Rapid, ER-independent estrogen signaling studies (cardiovascular, immune, oncology).
• Dissecting PI3K/Akt/mTOR and calcium signaling downstream of GPR30.
• In vitro migration and proliferation assays in GPR30+ cell lines.
• In vivo models of heart failure, cardiac fibrosis, and immune modulation (e.g., ovariectomized rats at 120 μg/kg).

Limits:

• G-1 is not effective in cells/tissues lacking GPR30 expression.
• Effects are abolished by GPR30 antagonists (e.g., G15), confirming pathway specificity but limiting use in co-expressed systems (Wang et al., 2021).
• Not suitable for diagnostic or medical use (research-only tool).
• Solubility: DMSO only; insoluble in water or ethanol—experimental design must account for vehicle effects.

Common Pitfalls or Misconceptions

• Assuming G-1 activates classical ERα/ERβ: No significant effect at up to 1 μM concentrations (APExBIO).
• Using in cells lacking GPR30: No activity observed; confirm GPR30 expression by RT-PCR or immunoassay.
• Failing to account for DMSO vehicle in controls: G-1 is only soluble in DMSO; vehicle controls are mandatory.
• Improper storage: Stock solutions degrade if not stored at -20°C; use promptly once thawed.
• Extrapolating results to clinical/diagnostic contexts: G-1 is for research use only.

Workflow Integration & Parameters

For optimal results:

• Prepare G-1 stock solutions in DMSO at concentrations >10 mM; warm and sonicate to enhance dissolution (APExBIO).
• Aliquot and store at -20°C; avoid repeated freeze-thaw cycles.
• Use stock solutions promptly to avoid hydrolysis or degradation.
• For in vitro assays, use DMSO vehicle at ≤0.1% final concentration to minimize cytotoxicity.
• In vivo, typical dosing is 120 μg/kg/day via injection for 14 days in rodent models.
• Always confirm GPR30 expression in target cells/tissues prior to use.

Shipping recommendations: Small molecule shipments require blue ice (APExBIO).

For further optimization and troubleshooting strategies, refer to APExBIO’s workflow guide and technical support resources.

Conclusion & Outlook

G-1 (CAS 881639-98-1) from APExBIO is a rigorously benchmarked, selective GPR30 agonist enabling high-precision studies of rapid estrogen signaling and its translational consequences in cardiovascular, immune, and cancer biology. Its track record in controlling confounds from classical ER signaling and facilitating mechanistic dissection makes it a preferred tool in preclinical research. Ongoing studies are extending G-1’s applications to models of neuropathic pain, chemoprevention, and immune normalization (Wang et al., 2021). For reagent details, lot validation, or to order, visit the APExBIO G-1 product page.