Summary: A new study from Hiroshima University identifies G protein-coupled receptor 3 (GPR3) as an immediate-early–like molecule that helps initiate stem cell differentiation into neurons. The team found that GPR3 is rapidly induced—within 30 minutes of growth factor exposure—and functions as an autonomous amplifier of the cAMP–CREB signaling pathway, linking early gene responses to downstream programs that support neuronal survival and synapse formation.
This fast-acting cascade promotes expression of the NR4A family of survival genes, directly connecting prompt transcriptional events to healthy synaptogenesis and highlighting a potential target for therapies addressing neurodevelopmental disorders such as autism.
Key Facts
- Unusually fast receptor activation: GPR3 is induced within 30 minutes of growth factor stimulation, displaying kinetics similar to classical immediate-early genes.
- Autonomous signal amplification: GPR3 can activate downstream signaling without the immediate presence of an external ligand, converting transient cues into sustained intracellular programs.
- Boosts cAMP–CREB signaling: Early GPR3 expression strongly amplifies the cAMP–CREB pathway, enabling short-term extracellular signals to trigger long-term genetic programs for neuronal maturation.
- Direct link to synaptic development: The GPR3-driven cascade elevates NR4A expression, which supports synapse formation and the survival of new neurons.
- Clinical relevance: Mapping how early transcriptional events shape brain plasticity may reveal therapeutic targets for neurodevelopmental and neuropsychiatric disorders.
Source: Hiroshima University
Background: Cell surface receptors are central to how cells sense and respond to their environment. Most receptors accumulate on the membrane as cells mature, functioning later in development. The Hiroshima University group reports that GPR3 behaves differently: it is induced early and drives downstream programs that promote the transition of progenitor cells into neurons.
The research, published March 20 in iScience, shows that GPR3 acts like an immediate-early gene—triggering rapid downstream signaling—rather than the delayed response typical of most G protein-coupled receptors (GPCRs). According to corresponding author Shigeru Tanaka, associate professor of molecular and pharmacological neuroscience at Hiroshima University, understanding these early transcriptional responses is crucial because they determine neuronal development, synapse formation, and plasticity; when dysregulated, these programs are associated with neurological conditions such as autism and cognitive dysfunction.
To study this mechanism, the team used rodent PC12 cells, a well-established model for nerve growth factor (NGF)-induced neuronal differentiation. After NGF stimulation, PC12 cells extend neurites over a 48-hour period, a process that can lead to mature neuronal networks. The researchers observed that GPR3 mRNA and transcriptional activity rose within 30 minutes of NGF exposure—an induction speed comparable to classical immediate-early genes and unprecedented for a GPCR family member.
Tanaka and colleagues describe GPR3 as a “signal amplifier.” Its early induction converts brief upstream signals into prolonged intracellular activity required for neuronal maturation. Genetic and molecular analyses showed that early GPR3 expression enhances cAMP–CREB signaling, a pathway known to translate transient signals into sustained transcriptional responses. This amplification subsequently increases expression of NR4A genes, immediate-early transcription factors essential for neuron survival and presynaptic development.
Functional experiments support this cascade: GPR3 induction promotes NR4A (Nr4a1–3) expression and increases Synapsin1 (Syn1) transcription through an Nr4a1-dependent route. In primary cortical neurons, deletion of Gpr3 reduced the developmental upregulation of Nr4a genes and Syn1, and lowered SYN1-positive vesicle density—evidence that early GPR3 activity contributes to presynaptic maturation.
“These results reveal a previously unrecognized signaling cascade that links immediate transcriptional responses to synapse development,” Tanaka said. The team plans to explore how GPR3 influences synaptic function, neural circuit formation, and the mechanisms by which its dysregulation may contribute to neurodevelopmental disorders.
The study’s ultimate aim is to clarify how activity-dependent transcriptional programs guide brain development and to identify potential therapeutic targets for neurodevelopmental and neuropsychiatric diseases.
Contributors: Fumiaki Ikawa, Hiroko Shiraki, Kana Harada, Izumi Hide, and Norio Sakai, Department of Molecular and Pharmacological Neuroscience, Graduate School of Biomedical and Health Sciences, Hiroshima University.
Funding: Supported by the Japan Society for the Promotion of Science.
Key Questions Answered
A: Immediate-early genes respond within minutes to stimuli and jumpstart fundamental cellular programs. GPCRs are typically expressed later in development as cells mature. Discovering a GPCR that is rapidly induced flips the conventional view: a receptor can act as an early director of neural development instead of only serving matured cells.
A: GPR3 amplifies intracellular cAMP–CREB signaling shortly after induction. This amplification bridges transient extracellular cues and sustained transcriptional programs, driving expression of genes like NR4A that are required for neurite outgrowth and lasting synapse formation.
A: Precise timing of activity-dependent transcriptional programs is critical for correct circuit assembly. Disruptions in those early programs can miswire brain circuitry. Identifying GPR3 as a key early controller allows researchers to investigate whether its dysregulation contributes to disorders such as autism and to explore targeted interventions.
Editorial Notes
- Edited by a Neuroscience News editor.
- Original journal paper reviewed in full.
- Additional context provided by editorial staff.
About this research news
Author: Lika Araki
Source: Hiroshima University
Contact: Lika Araki – Hiroshima University
Image: Image credited to Neuroscience News
Original Research: Open access. “GPR3 is an immediate-early gene-like GPCR regulating CREB-dependent neuronal differentiation” by Tanaka S, Ikawa F, Shiraki H, Harada K, Hide I, Sakai N. iScience
DOI: 10.1016/j.isci.2026.114944
Abstract
GPR3 is an immediate-early gene-like GPCR regulating CREB-dependent neuronal differentiation
GPR3 is a constitutively active Gs-coupled receptor whose transcriptional regulation during neuronal differentiation had been unclear. The authors identify Gpr3 as an immediate-early–like transcript rapidly induced by nerve growth factor (NGF) and cAMP signaling in PC12 cells, with biphasic activation revealed by native elongating transcript-cap analysis of gene expression (NET-CAGE) at a core promoter near the transcription start site.
Five cAMP response elements (CREs) within the 1-kb regulatory region cooperatively mediated stimulus-responsive transcription, and phospho-CREB was selectively enriched at a proximal CRE. Early Gpr3 induction promoted delayed Nr4a1–3 expression and enhanced Synapsin1 (Syn1) transcription via an Nr4a1-dependent pathway. In primary cortical neurons, Gpr3 deletion reduced developmental upregulation of Nr4a1–3 and Syn1 and decreased SYN1-positive vesicle density.
These results support a model in which GPR3 functions as an activity-dependent cAMP amplifier that links early CREB activation to transcriptional programs governing NR4A signaling and presynaptic maturation during neuronal differentiation.