Chemical biology
A glutathione probe finds caffeine as a CaSR PAM
Open access · cc by · source: Europe PMC
Photoaffinity GSH analog DAZ-G labels the CaSR amino-acid site and shows caffeine is a positive allosteric modulator.
How this study connects
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Evidence for the claim as stated.
Photoaffinity GSH analog DAZ-G labels the CaSR amino-acid site and shows caffeine is a positive allosteric modulator.
Evidence for the claim as stated.
Study at a glance
- Design
- Animal / in-vitro — DAZ-G photoaffinity labeling of CaSR in HEK293 cells plus intracellular Ca2+ flux
- N
- Competition and Ca2+ assays across caffeine concentrations rather than a single N
- Population
- HEK293 cells expressing calcium-sensing receptor
- Outcome
- Caffeine is a positive allosteric modulator of CaSR, enhancing DAZ-G labeling at low micromolar concentrations when extracellular Ca2+ is present
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Inspect source passages
A glutathione probe finds caffeine as a CaSR PAM
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
What new CaSR ligand did DAZ-G reveal?
finding that caffeine is a potent PAM for CaSR
Where was human CaSR expressed for labeling?
Human CaSR was ectopically expressed in HEK293 cells
Key findings
DAZ-G binds the amino-acid binding site and is a potent PAM. Caffeine at 0–1 μM enhances labeling via the calcium-binding site, while higher concentrations compete at the amino-acid site; caffeine raises Ca2+ only when extracellular Ca2+ is present.
Methodology
Authors synthesized DAZ-G (diazirine/alkyne GSH), photocrosslinked it to CaSR in HEK293 cells, competed with known ligands, and read intracellular Ca2+ flux to test whether caffeine activates the receptor.
Limitations
The probe is currently a Western-blot tool, not a high-throughput screen, and caffeine’s in vivo CaSR contribution versus adenosine receptors is not measured here.
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