SPHINGOMYELINS AND CERAMIDES WITH VERY-LONG-CHAIN PUFAIN MEMBRANE FRACTIONS AND DOMAINS FROM RAT SPERMATOGENIC CELLS.

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

Puerto Iguazú

Congreso; 56th International Conference on the Bioscience of Lipids (ICBL); 2015

Sphingomyelins (SM) and ceramides (Cer) with nonhydroxy and 2-hydroxy very-long-chain PUFA (n-V and h-V) arespecific components ofrat spermatogenic cells, including pachytene spermatocytes and round spermatids. Here we evaluated how these lipids distribute among membrane fractions prepared from these germ cells in comparison with glycerophospholipids (GPL) and cholesterol. A small light (L) and a large heavy (H) membrane fractions, both derived from the cell plasma membrane, were isolated a detergent-free procedure, as well as a fraction containing intracellular membranes,used for comparison. Flotillin-1, a protein typical of raft membrane domains, was highly concentrated in the L fraction. Additionally, by using Triton X-100, detergent-resistant and detergent-soluble membrane (DRM and DSM, respectively) fractions were obtainedin order to compare results. The small L and DRM fractions were similar in that both displayeda higher percentage of SM and cholesterol than the corresponding H and DSMfractions. The SM fromthe L and DRM fractionswas rich in saturated fatty acids (SFA), whereas that of H and DSM fractions contained most of the n-V and h-V. The GPL followed the same trend, as the L and DRM fractions contained mostly SFA and mostly PUFA, respectively.Interestingly, DRM, but not L, containedCer with high proportion ofn-V and h-V,suggesting detergent-resistant propertiesof these unusual lipids.Thus, the L and DRM fractions from germ cells exhibit biochemical similarities in that they exclude SM with n-V and h-V, indicating that these species are not components of raftmembrane domains. The intracellular membrane fractionin the detergent-free methodcontained most of the n-V and h-V Cer species of the cells, likely precursors of the SM that in due course will bebiosynthesized and transferred to the H fraction of the plasma membrane.