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Characterization of leishmania (viannia) braziliensis membrane microdomains,and their role in macrophage infectivity.


Detergent-resistant membranes (DRMs) from Leishmania (Viannia) braziliensis promastigotes, insoluble with 1% Triton X-100 at 4C, were fractionated by ultracentrifugation on sucrose gradient. They were composed of glycoinositolphospholipids (GIPLs), inositol phosphorylceramide (IPC), phosphatidylinositol (PI), phosphatidylethanolamine (PE), and sterols. In contrast, 1% Triton X-100 soluble fraction was composed of PE, phosphatidylcholine (PC), phosphatidylserine (PS), PI, IPC, sterol, and lyso-PI. HPTLC immunostaining using monoclonal antibody SST-1 showed that 85% of GIPLs are present in DRMs, and immunoelectron microscopic analysis showed that SST-1-reactive components are located in patches along the parasite surface. No difference in GIPL pattern was observed by HPTLC between Triton X-100-soluble vs. insoluble fractions at 4 ˚C. Analysis of fatty acid composition by GC/MS showed in DRMs the presence of GIPLs containing an alkylacylglycerol, presenting mainly saturated acyl and alkyl chains. DRMs also contained sterol, IPC with saturated fatty acids, PI with at least one saturated acyl chain, and PE with predominantly oleic acid. Promastigotes treated with lipid microdomain-disrupting agent showed a significant inhibition of macrophage infectivity, suggesting a direct relation between lipid microdomains and parasite infectivity. (AU)

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