Neuritin Up-regulates Kv4.2 α-Subunit of Potassium Channel Expression and Affects Neuronal Excitability by Regulating the Calcium-Calcineurin-NFATc4 Signaling Pathway

Abstract

Neuritin is an important neurotrophin that regulates neural development, synaptic plasticity, and neuronal survival. Elucidating the downstream molecular signaling is important for potential therapeutic applications of neuritin in neuronal dysfunctions. We previously showed that neuritin up-regulates transient potassium outward current (IA) subunit Kv4.2 expression and increases IA densities, in part by activating the insulin receptor signaling pathway. Molecular mechanisms of neuritin-induced Kv4.2 expression remain elusive. Here, we report that the Ca2+/calcineurin (CaN)/nuclear factor of activated T-cells (NFAT) c4 axis is required for neuritin-induced Kv4.2 transcriptional expression and potentiation of IA densities in cerebellum granule neurons. We found that neuritin elevates intracellular Ca2+ and increases Kv4.2 expression and IA densities; this effect was sensitive to CaN inhibition and was eliminated in Nfatc4−/− mice but not in Nfatc2−/− mice. Stimulation with neuritin significantly increased nuclear accumulation of NFATc4 in cerebellum granule cells and HeLa cells, which expressed IR. Furthermore, NFATc4 was recruited to the Kv4.2 gene promoter loci detected by luciferase reporter and chromatin immunoprecipitation assays. More importantly, data obtained from cortical neurons following adeno-associated virus-mediated overexpression of neuritin indicated that reduced neuronal excitability and increased formation of dendritic spines were abrogated in the Nfatc4−/− mice. Together, these data demonstrate an indispensable role for the CaN/NFATc4 signaling pathway in neuritin-regulated neuronal functions.

Neuritin promotes neurite and spine growth in rat cerebellar granule cells via L‐type calcium channel‐mediated calcium influx

“…Treatment with 100 μM HNMPA (Yao et al . ), neuritin did not significantly increase neurite length (1.0 ± 5.7%, n = 41 and 43) or spine density (2.4 ± 4.6%, n = 31 and 26) relative to the control ( p > 0.05) (Fig. a and b).…”

“…Application of 10 μM nifedipine, 2 μM CMZ, or 5 μM CsA (Yao et al . ) could eliminate the neuritin‐induced increases in neurite length and spine density (Fig. a and b).…”

“…; Yao et al . ). Here we found that incubation of CGNs with 150 ng/mL neuritin for 12 and 24 h increased spine density by 58.0 ± 7.0% ( n = 32 and 33, p < 0.001) and 64.9 ± 7.3% ( n = 28 and 35, p < 0.001), respectively (Fig.…”

“…), rabbit polyclonal anti‐NFATc4 (RRID:AB_650208) (1 : 1000; Santa Cruz Biotechnology) (Yao et al . ), rabbit polyclonal anti‐Na‐K ATPase (1 : 1000; cat. no.…”

“…), and that activation of the Ca 2+ /CaN/nuclear factor of activated T cells (NFAT)c4 axis was required for this effect (Yao et al . ). We also showed that activation of IR and MEK/ERK signaling by neuritin enhanced synaptic transmission in the medial prefrontal cortex (Lu et al .…”