Abstract #T92

# T92
Localization of milk gangliosides in emulsion monolayers that resemble the milk fat globule membrane outer leaflet.
Luis M. Real Hernandez*1, Rafael Jimenez Flores1, 1The Ohio State University, Columbus, OH.

Currently, the localization of sialic acid containing glycolipids in the outer leaflet of the milk fat globule membrane (MFGM) is stated to be in regions of the MFGM not occupied by microdomains, highly ordered lipid structures formed from the interactions of sphingomyelin (SM) and cholesterol (CH) compounds. This contrasts with many reports in the literature describing the presence of gangliosides in microdomains in the outer leaflet of living cell membranes. Gangliosides are bioactive sialic acid containing glycolipids found in many dairy products. The outer leaflet of the MFGM is derived from the outer leaflet of the membrane of mammary cells, so one would hypothesize that MFGM microdomains could contain gangliosides. The uncertainty behind the mechanisms behind the mismatch in current data between ganglioside localization in MFGMs and living cells creates some skepticism of the currently reported data on this topic. In this work, oil-in-water emulsions were created where the predominant lipids present in the outer leaflet of the MFGM (phosphatidylcholine [PC], SM, and CH) were used as emulsifiers, and varying amounts of the predominant gangliosides (GM3 and GD3) in milk were added to observe their location within the MFGM-like emulsification monolayer. Localization was determined using a FV3000 fluorescent confocal microscope. Localization of non-microdomain forming lipids was done with the use of various fatty acid tail labeled PC probes added to the initial emulsifier mixtures before the creation of the emulsion. The commonly used rhodamine-phosphatidylethanolamine (Rho-PE) probe was not used in this work since PE is not significant present in the outer leaflet of the MFGM. Ganglioside localization was observed with the use of a wheat germ agglutinin probe coupled to an Alexa Fluor dye. Current preliminary data suggests that ganglioside localization is dependent on the emulsifier composition, which suggests that ganglioside localization might not be universal to all MFGMs.

Key Words: gangliosides, milk fat globule membrane (MFGM), confocal microscopy