Regulation of K_v4.3 currents by Ca²⁺/calmodulin-dependent protein kinase II

Abstract

The voltage-dependent K ϩ channel 4.3 (Kv4.3) is one of the major molecular correlates encoding a class of rapidly inactivating K ϩ currents, including the transient outward current in the heart (I to) and A currents (IA) in neuronal and smooth muscle preparations. Recent studies have shown that I to in human atrial myocytes and IA in murine colonic myocytes are modulated by Ca 2ϩ /calmodulin-dependent protein kinase II (CaMKII); however, the molecular target of CaMKII in these studies has not been elucidated. We performed experiments to investigate whether CaMKII could regulate K v4.3 currents directly. Inclusion of the autothiophosphorylated form of CaMKII in the patch pipette (10 nM) prolonged K v4.3 currents such that the time required to reach 50% inactivation from peak more than doubled, with positive shifts in voltage dependence of both activation and inactivation. In contrast, the rate of recovery from inactivation was accelerated under these conditions. CaMKII-inhibitory peptide or KN-93 produced effects opposite to that above; thus the rate of inactivation was increased, and recovery from inactivation decreased. A number of mutagenesis experiments were conducted on the three candidate CaMKII consensus sequence sites on the channel. Mutations at S550A, located at the COOH-terminal region of the channel, resulted in currents that inactivated more rapidly but recovered from inactivation at a slower rate than that of wild-type controls. In addition, these currents were unaffected by dialysis with either autothiophosphorylated CaMKII or the specific inhibitory peptide of CaMKII, suggesting that CaMKII slows the inactivation and accelerates the rate of recovery from inactivation of Kv4.3 currents by a direct effect at S550A, located at the COOH-terminal region of the channel. transient outward current; potassium channel; inactivation; phosphorylation

Ca2+/cAMP-Sensitive Covariation ofIAandIHVoltage Dependences Tunes Rebound Firing in Dopaminergic Neurons

“…6). The effects of BAPTA on I A and 8-Br-cAMP on I H are consistent with the well documented sensitivity of these currents to calcium and cAMP, respectively (Birnbaum et al, 2004;Sergeant et al, 2005;Zolles et al, 2006;Biel et al, 2009;Anderson et al, 2010). In addition, our data demonstrated a milder converse sensitivity of I H and I A to calcium and cAMP manipulation, respectively (Fig.…”

Reduced Expression of A-Type Potassium Channels in Primary Sensory Neurons Induces Mechanical Hypersensitivity

“…This would convert a normally innocuous tactile stimulus turns into a noxious stimulus. In addition to reduced expression, I A s can also be suppressed if the channel becomes phosphorylated (Beck et al, 1998;Birnbaum et al, 2004;Sergeant et al, 2005). Phosphorylation of Kv4.2 in dorsal horn neurons has been proposed to underlie the induction of central sensitization, a cellular mechanism of neuropathic pain (Ji et al, 2003).…”

W-7 modulates Kv4.3: pore block and Ca2+-calmodulin inhibition

“…Synthetic mRNA was prepared using an mMESSAGE mMACHINE T7 kit (Ambion, Austin, TX). A Kv4.3 channel with mutated Ca 2ϩ /CaMKII consensus phosphorylation sites (S516A and S550A) in the COOH terminus (Kv4.3[S516A, S550A]) was prepared by PCR-based site-directed mutagenesis, as previously described (63).…”