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Updated: Aug 6, 2026

Drug-induced Sensitization of Adenylyl Cyclase: Assay Streamlining and Miniaturization for Small Molecule and siRNA Screening Applications
Published on: January 27, 2014
Guanylyl cyclase stimulatory coupling to K(Ca) channels
M Nara1, P D Dhulipala, G J Ji
1Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6046, USA.
Nitric oxide donors stimulate large-conductance, calcium-activated potassium (K(Ca)) channels via cGMP-dependent phosphorylation. Two specific serine residues (855 and 869) on the channel alpha-subunit are crucial for this stimulatory coupling mechanism.
Area of Science:
- Molecular Biology
- Ion Channel Physiology
- Cell Signaling
Background:
- Large-conductance, calcium-activated potassium (K(Ca)) channels play vital roles in cellular excitability.
- The precise mechanisms by which signaling molecules like atrial natriuretic peptide (ANP) and nitric oxide (NO) modulate K(Ca) channel activity are not fully elucidated.
Purpose of the Study:
- To investigate the guanylyl cyclase-dependent signaling pathway linking ANP receptors to K(Ca) channel activation.
- To identify the specific molecular sites involved in the stimulatory coupling of K(Ca) channels by NO donors.
Main Methods:
- Coexpression of human K(Ca) channel subunits (alpha and beta) and rat ANP receptor genes in Xenopus oocytes.
- Electrophysiological recordings (whole-cell K(Ca) currents) to assess channel activity.
- Site-directed mutagenesis of putative phosphorylation sites on the K(Ca) channel alpha-subunit.
Main Results:
- ANP and spermine NONOate (a NO donor) significantly increased K(Ca) currents in oocytes.
- Inhibition of cGMP-dependent protein kinase (PKG) blocked ANP-stimulated K(Ca) currents.
- Mutating serine residues S855 and S869 on the K(Ca) channel alpha-subunit abolished NO donor-induced stimulation.
Conclusions:
- Nitric oxide donors stimulate K(Ca) channels through a cGMP-dependent phosphorylation pathway.
- Serine residues 855 and 869 are critical for the stimulatory coupling of K(Ca) channels by NO.
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