Sphingomyelins and ceramides with very-long-chain PUFA in membrane fractions and domains from rat spermatogenic cells

SANTIAGO VALTIERRA, F.X.; ORESTI, G.M.; MATEOS, M.V.; AVELDAÑO, M.I.

Iguazú

Conferencia; 56th Meeting of the International Conference on the Bioscience of Lipids (ICBL).; 2015

Sphingomyelins (SM) and ceramides (Cer) with nonhydroxy and 2-hydroxy very-long-chainPUFA (n-V and h-V) are specific components of rat spermatogenic cells,including pachytene spermatocytes and round spermatids. Here we evaluated howthese lipids distribute among membrane fractions prepared from these germ cellsin comparison with glycerophospholipids (GPL) and cholesterol. A small light(L) and a large heavy (H) membrane fractions, both derived from the cell plasmamembrane, were isolated a detergent-free procedure, as well as a fractioncontaining intracellular membranes, used for comparison. Flotillin-1, a proteintypical of raft membrane domains, was highly concentrated in the L fraction. Additionally,by using Triton X-100, detergent-resistant and detergent-soluble membrane (DRMand DSM, respectively) fractions were obtained in order to compare results. Thesmall L and DRM fractions were similar in that both displayed a higherpercentage of SM and cholesterol than the corresponding H and DSM fractions.The SM from the L and DRM fractions was rich in saturated fatty acids (SFA), whereasthat of H and DSM fractions contained most of the n-V and h-V. The GPL followedthe same trend, as the L and DRM fractions contained mostly SFA and mostlyPUFA, respectively.  Interestingly, DRM,but not L, contained Cer with high proportion of n-V and h-V, suggestingdetergent-resistant properties of these unusual lipids. Thus, the L and DRMfractions from germ cells exhibit biochemical similarities in that they excludeSM with n-V and h-V, indicating that these species are not components of raft membranedomains. The intracellular membrane fraction in the detergent-free method containedmost of the n-V and h-V Cer species of the cells, likely precursors of the SM thatin due course will be biosynthesized and transferred to the H fraction of theplasma membrane.