biology

GPR15

GPR15 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 GPR15 rather than just read about it. In short: G protein-coupled receptor 15 is a protein that in humans is encoded by the GPR15 gene. GPR15 is a class A orphan G protein-coupled receptor (heterotrimeric guanine nucleotide-binding protein, GPCR).

Key takeaways

GPR15 belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect GPR15 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of GPR15 from memory before moving on to harder problems.

Reference excerpt

G protein-coupled receptor 15 is a protein that in humans is encoded by the GPR15 gene. GPR15 is a class A orphan G protein-coupled receptor (heterotrimeric guanine nucleotide-binding protein, GPCR). The GPR15 gene is localized at chromosome 3q11.2-q13.1. It is found in epithelial cells, synovial macrophages, endothelial cells and lymphocytes especially T cells. From the mRNA sequence, a 40.8 kD molecular weight of GPR15 is proposed. In an epithelial tumor cell line (HT-29), however, a 36 kD band, composed of GPR15 and galactosyl ceramide, was detected. Protein expression in lymphocytes is strongly associated with hypomethylation of its gene.

Tissue distribution High gene expression was described for colonic mucosa, small bowel mucosa, liver, and spleen. Moderate gene expression was found in blood, lymph node, thymus, testis, and prostate. In peripheral blood, GPR15 is mainly found on T cells, especially on CD4+ T helper cells, and less prominent on B cells. By immunohistochemistry, GPR15 is found specifically in glandular cells of the stomach, α-cells of islet of Langerhans in pancreas, surface epithelium of small intestine and colon, hepatocytes in liver, tubular epithelium of the kidney and in diverse tumor tissues, such as glioblastoma, melanoma, small cell lung carcinoma or colon carcinoma.

Function The overall physiological role remains elusive. It seems to play a role in the homing of single T cell types to the colon. In humans, GPR15 controls, together with α4β7-integrin, the homing of effector T cells to the inflamed gut of ulcerative colitis. With respect to the homing of GPR15-expressing immune cells to the colon there are divergent mechanisms between human and rodents like mouse.

Ligands There are at least two endogenous ligands found recently. One ligand encoded by the human gene GPR15LG was identified as a robust marker for psoriasis whose abundance decreased after therapeutic treatment with anti-interleukin-17 antibody. Transcripts of GPR15LG are abundant in the cervix and colon. It is currently unknown whether GPR15LG causes disease symptoms or is the consequence of a disturbed epithelial barrier. It does not act as a chemotactic agent but rather decrease T cell migration suggesting a mechanism of heterologous receptor desensitization. The second ligand is a fragment of thrombomodulin exerting anti-inflammatory function in mice.

Clinical significance Human GPR15 was originally cloned as a co-receptor for HIV or the simian immunodeficiency virus. HIV-induced activation of GPR15 in enterocytes seems to cause HIV enteropathy accompanied by diarrhea and lipid malabsorption. In inflammatory bowel diseases (IBD) such as Crohn's disease and ulcerative colitis the proportion of GPR15-expressing cells among regulatory T cells is slightly increased in peripheral blood. In mouse, GPR15-deficient mice were prone to develop severe large intestine inflammation, which was rescued by the transfer of GPR15-sufficient T regs.

Lifestyle Chronic tobacco smoking is a very strong inducer of GPR15-expressing T cells in peripheral blood. Although the proportion of GPR15-expressing cells among T-cells in peripheral blood is a highly sensitive and specific biomarker for chronic tobacco smoking. It does not indicate a disturbed homeostasis in the lung.

References

Illustrations

Worked examples

Example 1 — a first encounter with GPR15

Start with the simplest possible case. Write down what GPR15 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 GPR15 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 GPR15 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 GPR15

In research: GPR15 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 GPR15 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: GPR15 is common in secondary-school and first-year university syllabi. It links to neighbouring topics G protein-coupled receptors, Genes on human chromosome 3, so understanding it makes those chapters shorter.
In everyday life: Look for GPR15 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 GPR15 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what GPR15 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 GPR15 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is GPR15 in simple terms?

G protein-coupled receptor 15 is a protein that in humans is encoded by the GPR15 gene. GPR15 is a class A orphan G protein-coupled receptor (heterotrimeric guanine nucleotide-binding protein, GPCR).

Why does GPR15 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 GPR15?

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 GPR15.