Molecular determinants for the endocytosis of the voltage-gated K ⁺ channel Kv1.3

The voltage-gated potassium channel Kv1.3 contributes to action potential conduction in sensory neurons and to sustained increases in cytoplasmic Ca²⁺ that activate immune cells. Here, we found that two distinct endocytosis-inducing stimuli acted through the same residues in Kv1.3 to control surface abundance and activity of the channel. Upon stimulation of the growth factor receptor EGFR, which stimulates Tyr-directed kinases and is important in neuronal differentiation, or of the Ser/Thr kinase PKC, which participates in the down-regulation of inflammatory responses, Kv1.3 underwent ubiquitination-dependent endocytosis that routed channel proteins to lysosomes for degradation. We mapped two lysine clusters in the N and C termini of Kv1.3, both of which became ubiquitinated upon activation of either Tyr or Ser/Thr kinases and whose combined mutation had an additive effect in reducing ubiquitination and endocytosis. Manipulations that prevented the ubiquitination or decreased the endocytosis of Kv1.3 resulted in increased Kv1.3 abundance at the immunological synapse and activity in primary human T cells. Prolonged channel accumulation at this location would be expected to increase Kv1.3-dependent leukocyte activation and lead to chronic inflammatory pathologies. Thus, ubiquitination fine-tunes cell biology by inducing the endocytosis and turnover of Kv1.3 in response to biological stimuli and insults.