Arthropod voltage-gated sodium channel (Nav) (Nav)

Arthropod voltage-gated sodium channels are essential transmembrane proteins that mediate the rapid influx of sodium ions required for the generation and propagation of action potentials in the nervous system (Dong et al., 2014). These channels consist of a large pore-forming alpha subunit, often referred to as the "Para" protein in insects, which contains four homologous domains each with six transmembrane segments (Silver et al., 2014). They serve as the primary molecular target for several major classes of insecticides, including pyrethroids, organochlorines like DDT, and sodium channel blocker insecticides (SCBIs) such as indoxacarb (Soderlund, 2012). Pyrethroids and DDT interact with the channel to delay its inactivation and closing, resulting in prolonged sodium currents that cause repetitive nerve firing, muscle spasms, and eventual "knockdown" or death (Zlotkin, 1999). Conversely, SCBIs bind to the channel in its inactivated state and block the pore, preventing sodium flow and leading to flaccid paralysis (Silver et al., 2014). The high selectivity of many modern insecticides for arthropod channels over mammalian counterparts is due to structural differences in the binding sites, making them effective tools for public health and agriculture (Dong et al., 2014). However, the widespread use of these chemicals has led to the emergence of knockdown resistance (kdr), characterized by specific point mutations in the channel gene that reduce insecticide binding affinity (Soderlund, 2012). Monitoring these mutations is a critical component of integrated pest management and the control of vector-borne diseases like malaria and Zika virus (IRAC, 2023).

Other names

Insect voltage-gated sodium channelPara-type sodium channelVoltage-gated sodium channelNav channelSodium channel protein para

Insecticides targeting these channels act through two primary mechanisms: Type I and Type II pyrethroids, along with DDT, bind to the channel and slow the closing (inactivation) and deactivation gates, leading to prolonged tail currents and hyperexcitability (Soderlund, 2012; Dong et al., 2014). In contrast, sodium channel blocker insecticides (SCBIs) like indoxacarb and metaflumizone act as state-dependent blockers that bind preferentially to the slow-inactivated state of the channel, effectively plugging the pore and causing paralysis (Silver et al., 2014).