biology

GPR139

GPR139 is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand GPR139 rather than just read about it. In short: G-protein coupled receptor 139 (GPR139) is a G protein-coupled receptor that in humans is encoded by the GPR139 gene. It is coupled to the Gq/11 pathway, which is functionally opposite to the Gi/o inhibitory signaling of classical opioid receptors.

Key takeaways

GPR139 belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect GPR139 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of GPR139 from memory before moving on to harder problems.

Reference excerpt

G-protein coupled receptor 139 (GPR139) is a G protein-coupled receptor that in humans is encoded by the GPR139 gene. It is coupled to the Gq/11 pathway, which is functionally opposite to the Gi/o inhibitory signaling of classical opioid receptors. It is evolutionarily ancient and highly conserved across vertebrate phylogenetic taxa, suggesting a fundamental role in neurophysiology. In humans, the receptor is exclusively expressed in the brain tissue, particularly in the medial habenula, septum, striatum, and hypothalamus. Historically classified as an orphan receptor, activated only by L-tryptophan and L-phenylalanine in very high concentrations, GPR139 was deorphanized in 2025 as a novel, non-canonical opioid receptor specific to dynorphins, which selectively promote G protein activation of the receptor. It is proposed to function as a molecular homeostatic brake for excessive canonical opioid and D2 receptor signaling. Tryptamine is also a potent agonist of the GPR139 and has been reported to regulate sleep. Research has shown that mice with loss of GPR139 experience schizophrenia-like symptomatology that is rescued with the dopamine receptor antagonist haloperidol and the μ-opioid receptor antagonist naltrexone.

Interactions with μ-opioid receptor GPR139 appears to counter μ-opioid receptors (MOR) through multiple mechanisms. GPR139 constitutively promotes MOR desensitization. Expression of GPR139 at stoichiometric levels promoted β-arrestin recruitment to activated MORs. Appropriately, expression inhibited MOR — induced G protein activation. Overexpression of GPR139, but not stoichiometric expression, also decreased MOR at the cell surface. GPR139 counteracts MOR signaling at secondary effectors. GPR139 expression inhibited GIRK channel activity through a Gq/11-dependent pathway. GPR139 activation increased cAMP production, also through a Gq/11-dependent pathway.

Ligands

Agonists JNJ-63533054 TC-O 9311 [444932-31-4] Tryptamine Zelatriazin (TAK-41), (NBI-1065846) a potent, and GPR139 receptor selective agonist which was in clinical trials to gauge the efficacy for treating psychiatric conditions such as major depressive disorder and the negative symptoms of schizophrenia, but was later dropped from development.

Antagonists JNJ-3792165

References

Illustrations

Worked examples

Example 1 — a first encounter with GPR139

Start with the simplest possible case. Write down what GPR139 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to GPR139 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about GPR139 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of GPR139

In research: GPR139 appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses GPR139 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: GPR139 is common in secondary-school and first-year university syllabi. It links to neighbouring topics G protein-coupled receptors, Genes on human chromosome 16, Transmembrane receptor stubs, so understanding it makes those chapters shorter.
In everyday life: Look for GPR139 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study GPR139 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what GPR139 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain GPR139 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is GPR139 in simple terms?

Why does GPR139 matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study GPR139?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on GPR139.