The Shab family potassium channels are highly enriched at the presynaptic terminals of human neurons.

Abstract

The Shab family voltage-gated K⁺ channels (i.e., Kv2.1, Kv2.2) are widely expressed in mammalian brain, and regulate neuronal action-potential firing. In addition to their canonical functions, the Kv2 proteins help establish direct attachments between plasma membrane (PM) and endoplasmic reticulum (ER), also known as ER-PM junctions. However, the biochemical properties and molecular organization of these ion-channels have not yet been described in human neurons. Here, we have performed a systematic analysis of endogenous expression, post-translational modification (PTM), and subcellular distribution of the major components of Kv2 complex in neurons derived from human stem cells. We found that both Kv2.1, Kv2.2, and their auxiliary subunit AMIGO1, are significantly upregulated during early neurogenesis, localize at cell surface, and already begin to assemble with each other. Human Kv2.1 and AMIGO1, but not Kv2.2 undergo substantial PTM including phosphorylation and/or N-linked glycosylation. Acute pharmacological inhibition with Kv2 blockers also revealed their functional activation in human neurons. These proteins formed prominent clusters at cell bodies, dendritic branches, and axon initial segments. Interestingly, a large fraction of them also exhibited considerable accumulation at human presynaptic terminals, where they aggregated with local ER network. This synaptic localization of Kv2 subunits was primarily restricted to presynaptic region, as they demonstrated limited enrichment at postsynaptic density. These results were highly reproducible in multiple stem cell lines used and alternative differentiation protocols tested, confirming that human presynaptic compartments can actively recruit the Shab family K⁺ ion-channels.