Key Points
- To determine the molecular mechanism responsible for the ligand-induced desensitization of the guanylyl cyclase-A receptor.
- Expressed guanylyl cyclase-A (GC-A) in human embryonic 293 cells labeled with 32P to assess basal and ligand-stimulated phosphorylation states.
- Treated cells with atrial natriuretic peptide (ANP), protein phosphatase 2A, and the phosphatase inhibitor okadaic acid.
- Assayed receptor phosphorylation, electrophoretic mobility shifts using SDS-PAGE, and ANP-stimulatable guanylyl cyclase enzymatic activity.
- GC-A was identified as a phosphoprotein primarily modified at phosphoserine residues, which underwent time-dependent dephosphorylation and functional desensitization upon ANP exposure without receptor protein loss.
- Protein phosphatase 2A induced identical electrophoretic mobility shifts, catalyzed GC-A dephosphorylation, and directly reduced ANP-stimulatable guanylyl cyclase activity.
- Inhibition of protein phosphatase 2A with okadaic acid blocked both GC-A dephosphorylation and desensitization.
Structured PICO
PPopulationhuman embryonic 293 cells expressing guanylyl cyclase-A (GC-A) receptor
IInterventionAtrial natriuretic peptide (ANP), protein phosphatase 2A, and Okadaic acid
OOutcomeDephosphorylation and desensitization of the GC-A receptorsurrogate
The study demonstrates that the guanylyl cyclase-A receptor is desensitized by ligand-induced dephosphorylation, contrasting with the mechanism of many other cell surface receptors.