Shedding and enrichment of the glycolipid-anchored complement lysis inhibitor protectin ( XXXX ) into milk fat globules.

@entity1 @entity0 @entity1009 @entity840 @entity7965 @entity2975 @entity291 @entity214
Protectin ( @entity1009 ) is a glycolipid-anchored inhibitor of the membrane attack complex (MAC) of @entity1 complement (C) that protects blood cells, endothelial cells and various epithelial cells from C-mediated lysis. Because of its activities protectin is a candidate molecule for use in the treatment of @entity7965 or conditions where MAC causes tissue damage. Soluble, phospholipid-free forms of protectin have been isolated from @entity1 urine and produced in recombinant form, but they have only a relatively weak C lysis-inhibiting activity. In the present study we have looked for functionally active protectin in @entity1 breast milk. Milk is rich in fat droplets, milk fat globules (MFG), that are enveloped in a plasma membrane derived from secretory cells of the mammary gland. The membranes of MFG contain a variety of glycoproteins expressed by the mammary epithelial cells. Both immunofluorescence and immunoblotting analysis demonstrated that protectin was strongly expressed on @entity1 MFG. In @entity214 - @entity2975 gel electrophoresis ( @entity214 -PAGE) analysis, MFG protectin (CD59M) appeared as distinct bands with apparent molecular weights of 19,000-23,000 MW, similar to protectin extracted from MCF7 @entity0 cells. CD59M in breast milk was functionally active and had a glycophospholipid anchor, as judged by its ability to incorporate into @entity840 erythrocytes and inhibit their lysis by @entity1 complement. These results indicate that functionally active protectin becomes enriched in MFG and imply that secretion of glycophospholipid-anchored molecules, e.g. into @entity291 milk and colostrum, could be exploited as a means of producing bioactive molecules that need to be targeted into cell membranes.
