Enhances para sodium channel function. Required during pupal development to rescue adult paralysis and also protects adult flies against heat-induced lethality.

(UniProt, P48613)

Mutant becomes paralyzed rapidly at 38; recovers within seconds when temperature is lowered. No apparent increase in recovery times with longer exposure to high temperature (Jackson et al., 1986). When in a double mutant combination with parats1, tipE results in action potential failures in recordings from larval motor neurons at 33, a temperature at which either parats1 or tipE alone seems to have normal nerve conduction (Ganetzky, 1986). Adult action potential failures in napts;tipE double mutants occur at a lower temperature (31) than in wild type (Ganetzky, 1986); flies of this double-mutant genotype exhibit poorer viability and become paralyzed at lower temperatures than either mutant alone. The parats1; tipE double mutants also survive poorly, showing unconditional lethality in combinations with certain para alleles; In para/+; tipE/tipE mutants, para alleles become semi-dominant for heat-induced paralysis (Ganetzky, 1986). Biochemically, tipE leads to reduced levels of saxitonin binding activity (not temperature-dependent) in adult head extracts, but the dissociation constants for such binding is normal (Jackson et al., 1986). The mutant is slightly resistant to veratrine and shows enhanced tetrodotoxin sensitivity (Jackson et al., 1986). Sodium current density in cultured embryonic neurons is about half that recorded using "tight-seal" techniques from wild-type cells (O'Dowd and Aldrich, 1988, J. Neurosci. 8: 3633-43). When rather lengthy heat treatments are given to seits, the fairly long recovery times are partially suppressed by tipE. Partial suppression of Sh-induced leg shaking is also effected by tipE (Jackson et al., 1986).