Key result
Both conventional and novel PKC isozymes regulate the Kv3.1b channel, with novel PKC-delta specifically contributing to the maintenance of basal phosphorylation in auditory neurons.
Kv3.1b channel phosphorylation in auditory neurons is differentially regulated by conventional and novel PKC isozymes, with PKC-delta specifically maintaining basal phosphorylation.
Hypothesis-generating for PKC isozyme targeting in auditory neurons; does not support clinical translation without in vivo human validation.
In fast-spiking neurons such as those in the medial nucleus of the trapezoid body (MNTB) in the auditory brainstem, Kv3.1 potassium channels are required for high frequency firing. The Kv3.1b splice variant of this channel predominates in the mature nervous system and is a substrate for phosphorylation by protein kinase C (PKC) at Ser-503. In resting neurons, basal phosphorylation at this site decreases Kv3.1 current, reducing neuronal ability to follow high frequency stimulation. We used a phospho-specific antibody to determine which PKC isozymes control serine 503 phosphorylation in Kv3.1b-tranfected cells and in auditory neurons in brainstem slices. By using isozyme-specific inhibitors, we found that the novel PKC-delta isozyme, together with the novel PKC-epsilon and conventional PKCs, contributed to the basal phosphorylation of Kv3.1b in MNTB neurons. In contrast, only PKC-epsilon and conventional PKCs mediate increases in phosphorylation produced by pharmacological activation of PKC in MNTB neurons or by metabotropic glutamate receptor activation in Kv3.1/mGluR1-cotransfected cells. We also measured the time course of dephosphorylation and recovery of basal phosphorylation of Kv3.1b following brief high frequency electrical stimulation of the trapezoid body, and we determined that the recovery process is mediated by both novel PKC-delta and PKC-epsilon isozymes and by conventional PKCs. The association between Kv3.1b and PKC isozymes was confirmed by reciprocal coimmunoprecipitation of Kv3.1b with multiple PKC isozymes. Our results suggest that the Kv3.1b channel is regulated by both conventional and novel PKC isozymes and that novel PKC-delta contributes specifically to the maintenance of basal phosphorylation in auditory neurons.
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Song et al. (2006) studied this question. Isozyme-specific inhibitors and pharmacological activation of PKC was evaluated on Phosphorylation of Kv3.1b at Ser-503. Both conventional and novel PKC isozymes regulate the Kv3.1b channel, with novel PKC-delta specifically contributing to the maintenance of basal phosphorylation in auditory neurons.
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