{"type": "root", "children": [{"type": "t", "text": "<div>\n "}, {"type": "p", "children": [{"type": "t", "text": "\n The KCND2 gene encodes the pore‐forming α subunit of Kv4.2 channels that mediate rapidly inactivating, A‐type potassium currents in neurons. These currents are critical for setting subthreshold membrane potentials, regulating dendritic excitability, and shaping action potential back‐propagation, factors that underlie synaptic integration and plasticity. Kv4.2 function is tightly regulated at multiple levels. For example, its activity in dorsal horn and hippocampal neurons is modulated by kinase pathways such as ERK and by signaling proteins like Rap1 that couple second messenger systems to changes in channel phosphorylation and function."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": " Transcriptional regulation also plays an important role; TopIIβ binds near the KCND2 promoter to modulate its expression during later stages of neuronal differentiation"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "3"}]}, {"type": "t", "text": ", while local translation in dendrites is controlled by FMRP, linking KCND2 expression to activity‐dependent synaptic modulation."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": " In addition, targeted trafficking mechanisms are involved in proper dendritic localization of Kv4.2, with the kinesin Kif17 mediating its transport"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": "and scaffolding proteins such as PSD-95 and Navβ1 contributing to its stabilization and compartmentalization."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": " Dysregulation of KCND2/Kv4.2 channels has been implicated in human neurological disorders. A truncation mutation in KCND2 that alters Kv4.2 channel structure results in decreased A-type current density and is associated with temporal lobe epilepsy."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "8"}]}, {"type": "t", "text": " Depletion of Kv4.2 is also linked to dendritic hyperexcitability in Alzheimer’s disease"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "9"}]}, {"type": "t", "text": "and reduced surface expression of the channel is observed in fragile X syndrome, contributing to neuronal hyperexcitability."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "10"}]}, {"type": "t", "text": " Collectively, these studies underscore a central role for KCND2-encoded Kv4.2 channels in the fine-tuning of neuronal excitability and plasticity, wherein precise regulation of their expression, localization, and biophysical properties is critical for normal brain function and whose disruption contributes to disease.\n "}]}, {"type": "t", "text": "\n</div>"}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Hui-Juan Hu, Yarimar Carrasquillo, Farzana Karim, et al. 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