Effects of Filipin on the Structure and Biological Activity of Enveloped Viruses

Abstract

The interaction of the polyene antibiotic filipin with membrane-bound cholesterol in vesicular stomatitis (VS), influenza, and Rauscher leukemia virions was studied. Exposure of virions to filipin resulted in a series of depressions and ridges in the envelope of VS virions, with a periodicity of 15 to 20 nm perpendicular to the long axis of the particle; similar morphological alterations were observed in negatively stained preparations, in thin-sectioned virions, and in protease-treated virions that lack surface glycoproteins. This morphological effect was specific for filipin, since the envelopes of VS virions that had been treated with another polyene antibiotic, amphotericin B, exhibited markedly different morphology. Morphological alterations induced by filipin in influenza and Rauscher leukemia virions differed from those seen in VS virions. The infectivity of filipin-treated VS virions was reduced up to 500-fold, whereas influenza virions were resistant to filipin treatment. Incorporation of filipin into the virions was demonstrated, and no release of either lipids or proteins from virions was detected after filipin treatment. A stoichiometry of approximately 1 mol of bound filipin per mol of cholesterol was found in both intact and protease-treated VS virions. The equilibrium dissociation constant for filipin-cholesterol interaction was approximately 74-fold larger in intact than in protease-treated VS virions. The initial rate of association of filipin with cholesterol in intact virions was slower than that in protease-treated particles. The fluidity of lipids in VS viral membranes, as probed by a stearic acid derivative spin label, was markedly reduced when either intact or protease-treated virions were treated with filipin.

Cholesterol, regulated exocytosis and the physiological fusion machine

“…Cholesterol was required in the target membrane for the entry of a number of encapsulated viruses, such as SFV (Semliki Forest virus) [158][159][160][161], as were sphingolipids; however, virus entry did not depend on intact cholesterol-and sphingomyelinenriched microdomains, suggesting a direct role of cholesterol and sphingolipids in the fusion process [162,163]. The influenza virus does not require cholesterol in the target membrane [164]; however, depletion of envelope-associated cholesterol with mβcd (methyl-β-cyclodextrin) [165], but not filipin [166], was observed to inhibit viral infectivity. In studies of haemagglutininmediated cell fusion, both haemagglutinin-associated [163] and target membrane cholesterol [167] were found to promote fusion, with specific effects on pore formation.…”

Inhibiting Effect of Macrolide Polyene Antibiotics on Reproduction of Viruses

“…Ïîêàçàíî, ÷òî íàòèâíûå è õèìè÷åñêè ìîäèôè-ОБЗОРЫ öèðîâàííûå ÏÀ ïðåïÿòñòâóþò ðîñòó çëîêà÷åñòâåííûõ îáðàçîâàíèé [9]. Íåêîòîðûå èç ÏÀ îáëàäàþò ïðîòèâîâèðóñíûì ýôôåêòîì è ìîãóò áëîêèðîâàòü ïðîöåññ ðåïðîäóêöèè âèðóñà [10][11][12][13].  äàííîé ñòàòüå ïðåäñòàâëåíû äàííûå î ìåõàíèçìå ðåïðîäóêöèè âèðóñà â êëåòêå è ðåçóëüòàòû èíãèáèðóþùåãî ýôôåêòà ðåïðîäóêöèè âèðóñà ñ ïîìîùüþ ìàêðîëèäíûõ ïîëèåíîâûõ ñîåäèíåíèé.…”

Sterol‐polyene antibiotic complexation: Probe of membrane structure

“…The biological activity of these antibiotics includes the capacity to control serum choles-terol levels (18,19) and prostate malfunction (20) in dogs and to exert larvicidal and chemosterilant activity in some insects (21,22). In addition to their ability to inhibit the sporulation and growth of yeast and other fungi (23), some polyene antibiotics possess antiprotozoal (24) and antiviral (25)(26)(27) activities and, despite their ability to bind vertebrate cell sterols, they have clinical applicability. In fact, amphotericin B is currently the most effective agent in antifungal chemotherapy.…”

“…The requirements for strong filipin-sterol binding are the same as those for sterols to exert a regulatory effect in artificial membranes and Acholeplasma membranes, i.e., a planar steroid nucleus, an unesterified 3/3-hydroxyl group, and an apolar side chain at C-17; thus, the optical properties of filipin provide a convenient means by which phospholipid-sterol interactions may be examined (48,50,57)~ Filipin is not a typical probe in that it causes membrane perturbation, the extent of which depends on the conditions (antibiotic to sterol molar ratio, period of exposure of the membrane to the antibiotic, temperature) (50). Some of these perturbations are particularly striking and involve lateral redistributions of membrane components, as in the filipin-induced morphological alterations in the envelope of vesicular stomatitis (VS) virions (26). Along the periphery of the filipin-treated particles, a series of depressions and ridges occurred, with a periodicity of 15 to 20 nm; glycoprotein spikes were attached only to the ridges.…”

“…These alterations, which result from the binding of ca. 1 mole of filipin per mole of cholesterol, occur without detectable dissociation of lipids or proteins from the viral membrane (26).…”