Proper localization of the SCA13-linked K⁺ channel in Purkinje neurons requires a microtubule-stabilizing protein

Kv3.3 voltage-gated K⁺ (Kv) channels are highly expressed in cerebellar Purkinje neurons and some hippocampal neurons, aligning with the motor and cognitive impairments observed in spinocerebellar ataxia 13 (SCA13) caused by Kv3.3 mutations. Despite their functional significance, the mechanisms governing Kv3.3 subcellular localization remain poorly understood. Here we report microtubule-associated protein 6 (MAP6) regulates Kv3.3 axon-dendrite targeting. MAP6 deletion reduces Kv3.3 levels in the processes of Purkinje neurons. Mechanistically, MAP6's 1st and 2nd Mn modules directly bind the external surface of the Kv3.3 N-terminal T1 tetramer, while its 3rd Mn module indirectly associates with Cav2 Ca²⁺ channels. In Purkinje neurons, shRNA-mediated MAP6 knockdown decreases somatodendritic levels of both Kv3.3 and Cav2.1 (associated with SCA6). Notably, expression of Mn1/2-GFP selectively reduces Kv3.3, but not Cav2.1, levels. Purkinje neuron burst firing is reduced in both conditions. These findings uncover a MAP6-dependent mechanism for targeting two key ion channels linked to SCAs.