1.A.1.2.10
Voltage-gated K⁺ channel, chain A, Shaker-related, K_v1.2 or KCNA2 (Crystal structure known, Long et al., 2007; Chen et al. 2010). It functions with the auxiliary subunit, Ivβ1.2; 8.A.5.1.1) (Peters et al. 2009).  Delemotte et al. (2010) described the effects of sensor domain mutations on molecular dynamics of K_v1.2.  The Sigma 1 receptor (Q99720; Sigma non-opioid intracellular receptor 1) interacts with K_v1.2 to shape neuronal and behavioral responses to cocaine (Kourrich et al. 2013).  Amino acid substitutions cause Shaker to become heat-sensing (opens with increasing temperature as for TrpV1) or cold-sensing (opens with decreasing temperature as for TrpM8) (Chowdhury et al. 2014).  The Shaker Kv channel was truncated after the 4th transmembrane helix S4 (Shaker-iVSD) which showed altered gating kinetics and formed a cation-selective ion channel with a strong preference for protons (Zhao and Blunck 2016).  Direct axon-to-myelin linkage by abundant K_V1/Cx29 (TC# 1.A.24.1.12) channel interactions in rodent axons supports the idea of an electrically active role for myelin in increasing both the saltatory conduction velocity and the maximal propagation frequency in mammalian myelinated axons (Rash et al. 2016). A cryoEM structure (3 - 4 Å resolution; paddle chimeric channel; closed form) in nanodiscs has been determined (Matthies et al. 2018). Possible gating mechanisms have been discussed (Kariev and Green 2018; Infield et al. 2018). Pathogenic variants in KCNA2, encoding the voltage-gated potassium channel Kv1.2, have been identified as the cause for an evolving spectrum of neurological disorders. Affected individuals show early-onset developmental and epileptic encephalopathy, intellectual disability, and movement disorders resulting from cerebellar dysfunction (Döring et al. 2021). In addition, individuals with a milder course of epilepsy, complicated hereditary spastic paraplegia, and episodic ataxia have been reported. Biophysical properties of a delayed rectifier K⁺ current can contribute to its role ingenerating spontaneous myogenic activity (Hu et al. 2021).