Regulation of Kv2 potassium channel diversity and function in brain by electrically silent subunits

Kv2家族的电压门控K+通道（Kv2.1和kv2.2）在脑中高度表达，具有重要的神经功能

Voltage-gated K+ channels of the Kv2 family (Kv2.1 and 2.2) are highly expressed in brain and have important and diverse functions in mammalian neurons. First, Kv2 channels play important canonical roles as voltage-activated channels that regulate neuronal action potentials and membrane excitability, and genetic mutations or targeted deletions of these channels cause hyperactivity and seizures. Second, Kv2 channels are highly clustered on neuronal cell bodies and proximal dendrites and have a separate structural role in organizing specialized microdomains called endoplasmic reticulum - plasma membrane (ER-PM) junctions, which serve as important hubs for Ca and lipid signaling in brain neurons. Kv2 channels organize these sites by interacting with ER VAP proteins via a highly conserved PRC domain in the Kv2 C-terminal tail. Kv2 channels are thought to be largely composed of Kv2.1 and Kv2.2 subunits, which can co-assemble to form homo- or hetero-tetrameric channels. Another potential - but largely unexplored - source of Kv2 channel diversity comes from electrically silent or accessory K+ channel (KvS) subunit genes. This extensive and highly conserved family was termed “electrically silent” because they require co-assembly together with Kv2.1 or Kv2.2 in order to form functional ion-conducting channels when expressed in heterologous cells. Gene expression analyses demonstrate that KvS subunit family members are differentially expressed in distinct brain regions and neuron subtypes, however there is currently no information available on native KvS-Kv2 channels in brain at the protein level. In preliminary mass spectrometry-based proteomics experiments, we identified several KvS subunits that interact with Kv2.1 in brain and generated specific antibodies to these subunits. Using these antibodies, we have made the major discovery that one KvS subunit is a remarkably common constituent of Kv2 channels and that it colocalizes with Kv2 at ER-PM junctions in subsets of cortical neurons. The objective of this exploratory study, therefore, is to characterize the neuronal expression and subcellular localization of these KvS family members, and to define their contribution to Kv2 channel diversity in mammalian brain neurons. This exploratory work will provide important new insight into how selective expression of KvS subunits impacts Kv2 channel diversity in brain and how it modulates Kv2 channel function and localization in different neuronal populations.