The Modulation Of Voltage-gated Sodium Channel Nav1.7 By Fyn Tyrosine Kinase

?Background?Voltage-gated sodium channels?VGSC?are essential for the initiation and propagation of action potentials.Fyn kinase,a member of the Src family of nonreceptor tyrosine kinase,is involved in many neuronal functions,including myelination,neurite outgrowth,synaptic transmission.Previous studies have demonstrated that Fyn kinase could act on Nav1.2 and Nav1.5,modulating channel fast inactivation.However,whether Fyn kinase could modulate Nav1.7 channels is unknown.?Objective?The goal of this study is to determine?whether Fyn kinase has modulatory effect on Nav1.7 channels;and?the underlying mechanisms of Fyn-mediated modulation.?Methods?We examined the protein expression,mRNA transcription,protein interaction,tyrosine phosphorylation,and channel biophysical properties of Nav1.7 using multiple techniques,including Western blot,real-time PCR,?co-?immunoprecipitation,mutagenesis,and electrophysiological recordings.?Results?1.Fyn^CA elevated Nav1.7 protein expression by enhancing the transcription and inhibiting the ubiquitin-proteasome mediated degradation of Nav1.7.2.Fyn^CA directly acted on Nav1.7 and phosphorylated Y1470 and Y1471 located within the Loop3 of Nav1.7.Mutating both tyrosine residues dramatically reduced the current densities of mutant channels expressed in both HEK 293 cells and ND7/23 cells,but their actitivation and inactitivation were not influenced by Fyn^CA in ND7/23 cells.3.Fyn^CAA elevated the number of Nav1.7 on the cell surface and increased the current density of Nav1.7;also Fyn^CA modulated Nav1.7 gating properties in cell-specific manner,causing hyperpolarizing shifts in activation,fast inactivation and slow inactivation curves of Nav1.7 expressed in ND7/23 cells,with little effect on channel gating of Nav1.7 expressed in HEK 293 cells.4.Fyn^CA increased protein expression of Nav1.6 and Nav1.8,but exhibiting different effects on current density and gating properties in ND7/23 cells.?Conclusion?Fyn kinase modulates protein expression and gating properties of Nav1.7 through direct and indirect actions on Nav1.7.Fyn modulates Nav1.7 properties in cell type-specific manner,with additional signal pathway/molecules being involved in ND7/23cells.The different effect on Nav1.6,Nav1.7 and Nav1.8 by Fyn^CA suggest an isoform-specific modulation.The physiological and pathological functions of Fyn-mediated modulation of Nav1.7 channels require future study.