Related Experiment Videos
Calcium-controlled secretion is effected through a guanine nucleotide regulatory protein in parathyroid cells
Abstract:
Calcium regulates parathyroid secretion through mechanisms yet to be elucidated. We have investigated this phenomenon through use of pertussis toxin which catalyzes ADP-ribosylation and inactivation of a guanine nucleotide regulatory protein, possibly Ni or No. Calcium inhibition of PTH release is blocked in cells treated with pertussis toxin, and there is concomitant ADP-ribosylation of a 40-kilodalton protein. The ionophore A23187 inhibits secretion in toxin-treated as well as in control cells. We conclude that a guanine nucleotide regulatory protein is involved in calcium regulation of PTH secretion at a locus proximal to the intracellular site effecting inhibition of secretion.
Insights
Calcium regulation of parathyroid hormone (PTH) secretion involves a guanine nucleotide regulatory protein. Pertussis toxin blocks calcium
Area of Science:
- Endocrinology
- Cell Signaling
- Molecular Biology
Background:
- Calcium is a key regulator of parathyroid hormone (PTH) secretion.
- The precise molecular mechanisms underlying calcium's regulation of PTH secretion remain unclear.
Purpose of the Study:
- To investigate the role of guanine nucleotide regulatory proteins in calcium-mediated PTH secretion.
- To elucidate the signaling pathway involved in calcium's inhibitory effect on PTH release.
Main Methods:
- Utilized pertussis toxin to ADP-ribosylate and inactivate guanine nucleotide regulatory proteins.
- Assessed the effect of pertussis toxin on calcium-induced inhibition of PTH secretion.
- Examined the ADP-ribosylation of cellular proteins in response to toxin treatment.
Main Results:
- Pertussis toxin treatment blocked the inhibitory effect of calcium on PTH secretion.
- Concomitant ADP-ribosylation of a 40-kilodalton protein was observed in toxin-treated cells.
- The ionophore A23187 inhibited PTH secretion in both control and toxin-treated cells, indicating a distinct pathway.
Conclusions:
- A guanine nucleotide regulatory protein is implicated in the calcium regulation of PTH secretion.
- This regulatory protein acts proximally to the intracellular mechanism that inhibits secretion.
- The findings suggest a specific signaling pathway involving G proteins in calcium homeostasis and PTH release.