1. We have investigated the possible role of A-kinase anchoring proteins (A
KAPS) in protein kinase A (PKA) signalling to ATP-sensitive K+ (K-ATP) chan
nels of rat isolated mesenteric arterial smooth muscle cells using whole-ce
ll patch clamp and peptides that inhibit PKA-AKAP binding.
2. Intracellular Ht31 peptide (20 mum) which inhibits the PKA-AKAP interact
ion, blocked K-ATP current activation by either dibutyryl cAMP or calcitoni
n gene-related peptide. Ht31-proline (20 muM), which does not inhibit PKA b
inding to AKAP, did not block K-ATP current activation.
3. Ht31 reduced K-ATP current activated by pinacidil and also prevented its
inhibition by Rp-cAMPS, effects consistent with Ht31 blocking steady-state
K-ATP channel activation by PKA. However, Ht31 did not prevent K-ATP curre
nt activation by the catalytic subunit of PKA.
4. An antibody to the RII subunit of PKA showed localization of PKA near to
the cell membrane. Our results provide evidence that both steady-state and
receptor-driven activation of K-ATP channels by PKA involve the localizati
on of PKA by an AKAP.