Chemical Activated LUciferase gene eXpression (CALUX) is a

ligand In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...

-dependent nuclear receptor-based

bioassay A bioassay is an analytical method to determine the potency or effect of a substance by its effect on animal testing, living animals or plants (''in vivo''), or on living cells or tissues (''in vitro''). A bioassay can be either quantal or quantit ...

used in the detection of specific chemicals or classes of chemicals in samples. It consists of a modified

cell line An immortalised cell line is a population of cells from a multicellular organism that would normally not proliferate indefinitely but, due to mutation, have evaded normal cellular senescence and instead can keep undergoing division. The cells ...

that has been stably transfected with a

DNA construct A DNA construct is an artificially-designed segment of DNA borne on a Vector (molecular biology), vector that can be used to incorporate genetic material into a target Biological tissue, tissue or Cell (biology), cell. A DNA construct contains a DNA ...

with a

luciferase Luciferase is a generic term for the class of oxidative enzymes that produce bioluminescence, and is usually distinguished from a photoprotein. The name was first used by Raphaël Dubois who invented the words ''luciferin'' and ''luciferase'' ...

reporter gene Reporter genes are molecular tools widely used in molecular biology, genetics, and biotechnology to study gene function, expression patterns, and regulatory mechanisms. These genes encode proteins that produce easily detectable signals, such as ...

under control of receptor-specific

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

response elements ''Response elements'' are short sequences of DNA within a gene Promoter (genetics), promoter or Enhancer (genetics), enhancer region that are able to bind specific transcription factors and regulate Transcription (genetics), transcription of genes. ...

that can stimulate

transcription Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including: Genetics * Transcription (biology), the copying of DNA into RNA, often th ...

of the inserted luciferase

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

and produce the light-generating enzyme which can be easily measured. The DNA response elements can be varied in order to provide binding sites for other receptors that are regulated by a chemical or class of chemicals of interest that want to be detected. Thus, numerous CALUX bioassays have been developed for detection of diverse chemicals of interest. Most applications have been directed toward the detection of environmentally harmful chemicals, such as those affecting the endocrine system ( environmental hormones). CALUX is an effect based screening method, as it measures the total effect

ligands In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's ...

(from a sample) have on a specific receptor. Unlike

chemical analysis Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separa ...

, CALUX is thus able to measure total activity on the receptor of interest. This includes both identified and unidentified activators (

agonists An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agon ...

) and inhibitors (

receptor antagonists A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of recep ...

Applications

The aryl hydrocarbon receptor (AhR)-responsive (AhR-CALUX) bioassay is commonly used in the detection of

dioxins and dioxin-like compounds Dioxins and dioxin-like compounds (DLCs) are a group of chemical compounds that are persistent organic pollutants (POPs) in the environmental pollutant, environment. They are mostly by-products of burning or various industrial processes or, in the ...

in sample extracts. It is based on the molecular mechanism by which the

AhR Ahr () is a river in Germany, a left tributary of the Rhine. Its source is at an elevation of approximately above sea level in Blankenheim in the Eifel, in the cellar of a timber-frame house near the castle of Blankenheim. After it crosses f ...

activates gene expression. AhR-CALUX is used by researchers and companies that want to screen for the presence of

in a wide variety of biological and environmental matrices, commercial and consumer products and in food and feed in order to evaluate their safety and/or level of contamination. While the measurement of dioxin and related dioxin-like chemicals in a sample extract using the AhR-CALUX bioassay is significantly cheaper than the chemical analysis requiring gas chromatography - high-resolution mass spectrometry (GC-HRMS), it only provides a measurement of the total level of AhR-active dioxins and related dioxin-like chemicals in a sample extract and determination of the specific congeners requires analysis any GC-HRMS. Additionally, given the recently established role of the AhR in human health and disease, the AhR-CALUX bioassay is also being used widely as a high-throughput screening method to identify and characterize AhR-active chemicals as potential human therapeutic drugs. Environmental chemicals having sex hormone-like activity are detected by similar bioassays as well, including the Estrogen Receptor-Responsive CALUX (ER-CALUX) and Androgen Receptor-Responsive CALUX (AR-CALUX).

References

{{reflist, 30em Biotechnology Toxicology Environmental technology

Applications

See also

References