CHARACTERIZATION OF MAS-7-INDUCED PORE FORMATION IN SK-N-BE(2)C HUMANNEUROBLASTOMA-CELLS

Mastoparan, a peptide toxin from wasp venome, mimics receptors by stim ulating the GTPase activity of guanine nucleotide binding proteins and the G-protein-coupled phospholipase C (PLC), By using Mas-7, the acti ve analog of mastoparan, we showed that it makes pores in the plasma m embrane. Treatment with Mas-7 but not Mas-17, the inactive analog, pro duced a concentration-dependent rise in intracellular Ca2+ concentrati on ([Ca2+](i)) and facilitated the uptake of ethidium bromide (EtBr) ( 314 Da) to a sustained level during the stimulation. In addition, Mas- 7 triggered the influx of lucifer yellow (457 Da), while it did not in duce the influx of fura-2 (831 Da) and Evans blue (961 Da). However, t he Mas-7-induced permeability was selectively prevented by the additio n of La3+, Ni2+, and Co2+, but not Cd2+. This blocking activity was co ncentration-dependent. While the stimulatory effect of Mas-7 on PLC ac tivity was dependent on extracellular Ca2+, the pore forming activity of Mas-7 was not effected by removal of extracellular Ca2+ These resul ts, therefore, suggest that the mastoparan's action in pore formation is independent from its action in PLC stimulation and is negatively ef fected by inorganic cations.