Related Experiment Videos
A novel plasma membrane Ca(2+)-pump inhibitor: caloxin 1A1
Jyoti Pande1, Kanwaldeep K Mallhi, Ashok K Grover
1Department of Biology, McMaster University, Hamilton, Ontario, Canada L8N 3Z5.
European Journal of Pharmacology
|February 1, 2005
Summary
Researchers discovered caloxin 1A1, a novel peptide inhibitor of the plasma membrane calcium pump. This inhibitor targets the pump's extracellular domain, affecting calcium transport and cellular calcium levels.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Physiology
Background:
- The plasma membrane Ca(2+)-Mg(2+)-ATPase (PMCA) is crucial for extruding calcium ions (Ca2+) from cells.
- Understanding PMCA regulation is vital for cellular homeostasis and various physiological processes.
Purpose of the Study:
- To identify novel inhibitors of the PMCA.
- To investigate the mechanism of PMCA inhibition by a newly discovered peptide, caloxin 1A1.
Main Methods:
- Screening a cysteine bridge-constrained random peptide library.
- Assessing inhibition of PMCA and sarcoplasmic reticulum Ca(2+)-Mg(2+)-ATPase (SERCA) activity.
- Analyzing the effect of dithiothreitol (DTT) on inhibition.
- Studying the stabilization of the 140-kDa acylphosphate intermediate.
- Measuring cytosolic Ca2+ concentration in endothelial cells.
Main Results:
- Caloxin 1A1 was identified as a novel peptide inhibitor of PMCA with a Ki of 100 μM.
- Inhibition by caloxin 1A1 required the cysteine bridge constraint and was reversed by DTT.
- Caloxin 1A1 weakly inhibited SERCA and stabilized a PMCA reaction intermediate.
- Caloxin 1A1 increased cytosolic Ca2+ in endothelial cells.
Conclusions:
- Caloxin 1A1 inhibits PMCA by interacting with its first extracellular domain, suggesting a role for transmembrane domains 1 and 2 in the enzyme's cycle.
- The findings provide insights into PMCA structure-function relationships and potential therapeutic strategies for calcium dysregulation.