Saposin B binds and transfers phospholipids

被引:30
作者
Ciaffoni, Fiorella
Tatti, Massimo
Boe, Alessandra
Salvioli, Rosa
Fluharty, Arvan
Sonnino, Sandro
Vaccaro, Anna Maria
机构
[1] Ist Super Sanita, Dept Hematol Oncol & Mol Med, I-00161 Rome, Italy
[2] Univ Calif Los Angeles, Mental Retardat Res Ctr, Los Angeles, CA 90024 USA
[3] Univ Calif Los Angeles, Jane & Terry Semel Inst Neurosci & Human Behav, Los Angeles, CA 90024 USA
[4] Univ Milan, Ctr Excellence Neurodegenerat Dis, I-20090 Segrate, Italy
[5] Univ Milan, Dept Med Chem Biochem & Biotechnol, I-20090 Segrate, Italy
关键词
phospholipid binding; phospholipid transfer; Saposin-membrane interaction;
D O I
10.1194/jlr.M500547-JLR200
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Saposin B (Sap B) is a member of a family of four small glycoproteins, Sap A, B, C, and D. Like the other three saposins, Sap B plays a physiological role in the lysosomal degradation of sphingolipids (SLs). Although the interaction of Sap B with SLs has been investigated extensively, that with the main membrane lipid components, namely phospholipids and cholesterol (Chol), is scarcely known. Using large unilamellar vesicles (LUVs) as membrane models, we have now found that Sap B simultaneously extracts from the lipid surface neutral [phosphatidylcholine (PC)] and anionic [phosphatidylinositol (PI)] phospholipids, fewer SLs [ganglioside GM1 (GM1) or cerebroside sulfate (CS)], and no Chol. More PI than SL (GM1 or CS) was solubilized from LUVs containing equal amounts of PI and SLs. An increase in PI level had a poor effect on the Sap B-induced solubilization of GM1 or CS but strongly inhibited that of PC. Sap B was able not only to bind, but also to transfer phospholipids between lipid surfaces. Both the phospholipid binding and transfer activities were optimal at low pH values. These results represent the first biochemical analysis of the Sap B interaction with phospholipids. The capacity of Sap B to bind and transfer phospholipids occurs under conditions mimicking the interior of the late endosomal/lysosomal compartment and thus might have physiological relevance.
引用
收藏
页码:1045 / 1053
页数:9
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