RESUMO
Voltage-gated sodium channels (VGSCs) are widely distributed in most cells and tissues, performing many physiological functions. As one kind of membrane proteins in the lipid bilayer, whether lipid composition plays a role in the gating and pharmacological sensitivity of VGSCs still remains unknown. Through the application of sphingomyelinase D (SMaseD), the gating and pharmacological sensitivity of the endogenous VGSCs in neuroblastoma ND7-23 cell line to BmK I and BmK AS, two sodium channel-specific modulators from the venom of Buthus martensi Karsch (BmK), were assessed before and after lipid modification. The results showed that, in ND7-23 cells, SMaseD did not change the gating properties of VGSCs. However, SMaseD application altered the slope factor of activation with the treatment of 30 nmol/L BmK I, but caused no significant effects at 100 and 500 nmol/L BmK I. With low concentration of BmK I (30 and 100 nmol/L) treatment, the application of SMaseD exerted hyperpolarizing effects on both slow-inactivation and steady-state inactivation, and increased the recovery time constant, whereas total inactivation and recovery remained unaltered at 500 nmol/L BmK I. Meanwhile, SMaseD modulation hyperpolarized the voltage dependence of slow-inactivation at 0.1 nmol/L BmK AS and altered the slope factor of slow-inactivation at 10 nmol/L BmK AS, whereas other parameters remained unchanged. These results indicated a possibility that the lipid bilayer would disturb the pharmacological sensitivity of VGSCs for the first time, which might open a new way of developing new drugs for treating sodium channelopathies.