Pathway for Ca2+ influx into cells by trichosporin-B-VIa, an α-aminoisobutyric acid-containing peptide, from the fungus Trichoderma polysporum

Abstract

Trichosporin (TS) -B-VIa, a fungal alpha-aminoisobutyric acid (Aib) -containing peptide consisting of 19 amino acid residues and a phenylalaninol, produced both 45Ca2+ influx into bovine adrenal chromaffin cells and catecholamine secretion from the cells. The secretion induced by TS-B-VIa at lower concentrations (2-5 microM) was completely dependent on the external Ca2+, while that induced by TS-B-VIa at higher concentrations (10-30 microM) was partly independent of the Ca2+. The concentration-response curves (2-5 microM) for the TS-B-VIa-induced Ca2+ influx and secretion correlated well. The TS-B-VIa (at 5 microM) -induced secretion was not antagonized by diltiazem, a blocker of L-type voltage-sensitive Ca2+ channels. The treatment of fura-2-loaded C6 glioma cells with TS-B-VIa (2-5 microM) led to an increase in the intracellular free Ca2+ concentration ([Ca2+]i) in a concentration-dependent manner but the stimulatory effects of TS-B-VIa on [Ca2+]i were only slightly observed in Ca(2+)-free medium, indicating that TS-B-VIa causes Ca2+ influx from the external medium into the C6 cells. The TS-B-VIa-induced increase in [Ca2+]i in the C6 cells was not antagonized by diltiazem and by SK&F 96365, a novel blocker of receptor-mediated Ca2+ entry. High K+ increased neither [Ca2+]1 in the C6 cells nor Mn2+ influx into the cells, while TS-B-VIa increased Mn2+ influx. Also in other non-excitable cells, bovine platelets, similar results were obtained. These results strongly suggest that the mechanism of Ca2+ influx by TS-B-VIa at the lower concentrations is distinct from the event of Ca2+ influx through receptor-operated or L-type voltage-sensitive Ca2+ channels in both excitable cells (the chrornaffin cells) and non-excitable cells (the C6 cells and the platelets) and that TS-B-VIa per se may form Ca(2+)-permeable ion channels in biological membranes. On the other hand, the peptide at the higher concentrations seems to damage cell membranes.

Hypopulvins, novel peptaibiotics from the polyporicolous fungus Hypocrea pulvinata, are produced during infection of its natural hosts

“…The structurally similar trichosporins B (Fig 1, Tables 2a and b) were isolated from the culture filtrate of Trichoderma polysporum TMI 60146, a destructive mycoparasite of Lentinus edodes (Fujita et al 1988; Iida et al 1993). To date, a multitude of biological activities has been reported for trichosporins B, including uncoupling of the respiratory activity of rat liver mitochondria (Fujita et al 1988; Okuda et al 1994), Ca 2+ -dependent catecholamine secretion from bovine adrenal medullary chromaffin cells (Tachikawa et al 1991, 1995, 1996), formation of voltage-gated ion channels (Nagaoka et al 1995), and antitrypanosomal activity (Iwatsuki et al 2010).…”

Model for a Helical Bundle Channel Based on the High-Resolution Crystal Structure of Trichotoxin_A50E

“…SF1, the largest SF, has the most widely studied range of functions in ViVo, including such activities as alamethicin causing the release of catecholamines in bovine chromaffin cells (59), and chrysospermin_C having some anti-cancer and anti-viral effects (60). Other SF1 peptaibols that have not yet been structurally characterized, such as the trichosporins, have been described to cause the influx of Ca 2+ ions into cells (61). The trichotoxins are able to form channels and exhibit antibiotic and insecticidal properties (48,49).…”

Novel Mycotoxin from Acremonium exuviarum Is a Powerful Inhibitor of the Mitochondrial Respiratory Chain Complex III

“…The biological effects of peptaibols are believed to be determined by their ability to incorporate into planar lipid bilayer membranes . Upon the association into oligomeric assemblies, the peptaibols may form ion channels as exemplified by trichosporin-Bs , trichocellins , hypelcins , antiamoebin , , and zervamicins or pores for low molecular weight solutes, for example, alamethicin ,, , trichovirin , chrysospermin , and hypelcin A , . This leads to an increase in the conductivity of membranes toward ions and solutes, a disturbance of ionic homeostasis, a loss of the osmotic balance, and cell death.…”