Surface expression of Kv3.3 potassium channels: Effects of SCA13 mutations and motifs
Voltage-gated potassium (Kv) channels play a pivotal role in setting the resting membrane potential and firing pattern of action potentials. Kv3.3, a member of Kv3 subfamily, has some distinct functional properties that enable neurons to fire at high frequencies. A proper surface expression of Kv3.3 is fundamental to neuronal excitability and survival. Kv3.3 is the causative gene of spinocerebellar ataxia type 13 (SCA13), an autosomal dominant neurological disorder. In the present study, we report that SCA13 mutations affect functional as well as the amounts of Kv3.3 proteins. The reduced protein level of SCA13 mutants is caused by a shorter protein half-life, and blocking the ubiquitin-proteasome pathway increases the total protein of SCA13 mutants more than wild-type Kv3.3. SCA13-mutated amino acids are highly conserved and the side chains of these residues play a critical role in the stable expression of Kv3.3 proteins. In addition, I also show that Kv3.3 protein expression levels could be partially rescued by treatment of chemical chaperone TMAO or co-expression of Kv3.1b. Thus, my results suggest that amino acid side chains of SCA13 positions affect the protein half-life and/or function of Kv3.3 and the adverse effect on protein expression levels cannot be fully rescued. The N-glycosylation studies demonstrate that all the three N-glycosylation sites of Kv3.3 are used for glycosylation, and that removing all the three sites affects both functional and protein expression levels of Kv3.3 channels. Thus, it increases our understanding of the role of N-glycans in protein and functional expression of ion channels. These data shed some light on the mechanism underlying the SCA13 disease, and provide strong evidence for the fundamental role of a proper surface expression of Kv3.3 channels in neuronal function and survival.
Zhao, Jian, "Surface expression of Kv3.3 potassium channels: Effects of SCA13 mutations and motifs" (2013). ETD Collection for Fordham University. AAI3563439.