Phospholamban regulates the Ca2+-ATPase through intramembrane interactions
Y Kimura1, K Kurzydlowski, M Tada
1Banting and Best Department of Medical Research, University of Toronto, Charles H. Best Institute, Toronto, Ontario M5G 1L6, Canada.
The Journal of Biological Chemistry
|September 6, 1996
Summary
Phospholamban (PLN) regulates cardiac calcium ATPase (SERCA2a) function through intramembrane interactions. These interactions affect calcium affinity, influencing heart muscle contraction.
Area of Science:
- Biochemistry
- Molecular Biology
- Cardiology
Background:
- Phospholamban (PLN) is known to regulate the cardiac sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) via cytoplasmic interactions.
- Evidence for regulatory interactions within the transmembrane domains of PLN and SERCA2a is less clear.
Purpose of the Study:
- To investigate intramembrane interactions between phospholamban (PLN) and SERCA isoforms in the absence of cytoplasmic interactions.
- To elucidate the role of transmembrane domains of PLN in modulating SERCA2a activity.
Main Methods:
- Coexpression of SERCA isoforms with modified transmembrane sequences of PLN (e.g., Met-PLN28-52, HA-PLN28-52, PLN1-20-PLN30-52).
- Assessment of Ca2+ transport inhibition and apparent Ca2+ affinity.
- Use of antibodies to confirm construct orientation and reversibility of inhibition.
Main Results:
- Coexpression of PLN transmembrane sequences inhibited Ca2+ transport by reducing apparent Ca2+ affinity.
- Specific modifications to the PLN transmembrane sequence further decreased Ca2+ affinity without uncoupling transport from ATP hydrolysis.
- Inhibition was reversible and dependent on the presence and orientation of the inhibitory PLN constructs.
Conclusions:
- PLN modulates SERCA2a apparent Ca2+ affinity through intramembrane interactions.
- These intramembrane interactions are distinct from and can act in concert with cytoplasmic interactions.
- The findings highlight the importance of transmembrane domain interactions in PLN-SERCA regulation.
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