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A glutathione probe finds caffeine as a CaSR PAM
Photoaffinity GSH analog DAZ-G labels the CaSR amino-acid site and shows caffeine is a positive allosteric modulator.
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What chemical tool did the authors design?
DAZ-G, a glutathione-derived photoaffinity probe for CaSR ligands.
Source: Glutathione-Based Photoaffinity Probe Identifies Caffeine as a Positive Allosteric Modulator of the Calcium-Sensing Receptor · DOI · quote verified
What new CaSR ligand did DAZ-G reveal?
Caffeine as a potent positive allosteric modulator.
Source: Glutathione-Based Photoaffinity Probe Identifies Caffeine as a Positive Allosteric Modulator of the Calcium-Sensing Receptor · DOI · quote verified
Where does DAZ-G primarily bind?
The amino-acid binding site (ABS), not the CBS or EBS.
Source: Glutathione-Based Photoaffinity Probe Identifies Caffeine as a Positive Allosteric Modulator of the Calcium-Sensing Receptor · DOI · quote verified
How does low-concentration caffeine affect labeling?
At 0–1 μM it likely occupies the CBS and increases DAZ-G conjugation at the ABS.
Source: Glutathione-Based Photoaffinity Probe Identifies Caffeine as a Positive Allosteric Modulator of the Calcium-Sensing Receptor · DOI · quote verified
At what extracellular Ca2+ was DAZ-G conjugation maximal?
2.5 mM; it fell again at 5 mM.
Source: Glutathione-Based Photoaffinity Probe Identifies Caffeine as a Positive Allosteric Modulator of the Calcium-Sensing Receptor · DOI · quote verified
How large was the DAZ-G Ca2+ fluorescence spike?
About 5.5-fold within 28–90 s at 100 μM DAZ-G.
Source: Glutathione-Based Photoaffinity Probe Identifies Caffeine as a Positive Allosteric Modulator of the Calcium-Sensing Receptor · DOI · quote verified
Name two approved CaSR PAMs cited as context.
Cinacalcet and etelcalcetide.
Source: Glutathione-Based Photoaffinity Probe Identifies Caffeine as a Positive Allosteric Modulator of the Calcium-Sensing Receptor · DOI · quote verified
What chemical handles does DAZ-G carry?
Photoaffinity diazirine and a clickable alkyne on the GSH scaffold.
Source: Glutathione-Based Photoaffinity Probe Identifies Caffeine as a Positive Allosteric Modulator of the Calcium-Sensing Receptor · DOI · quote verified
How was photocrosslinked probe detected?
Click chemistry with biotin-azide then analysis of lysates.
Source: Glutathione-Based Photoaffinity Probe Identifies Caffeine as a Positive Allosteric Modulator of the Calcium-Sensing Receptor · DOI · quote verified
Why is caffeine classified as a PAM rather than an agonist?
It does not raise intracellular Ca2+ without extracellular Ca2+.
Source: Glutathione-Based Photoaffinity Probe Identifies Caffeine as a Positive Allosteric Modulator of the Calcium-Sensing Receptor · DOI · quote verified
Where was human CaSR expressed for labeling?
Ectopically in HEK293 cells.
Source: Glutathione-Based Photoaffinity Probe Identifies Caffeine as a Positive Allosteric Modulator of the Calcium-Sensing Receptor · DOI · quote verified