Sphingomyelins with very long chain pufa are excluded from raft membrane domains in male germ cells

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

ROSARIO

Congreso; L Reunión Nacional de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2014

The synthesis of sphingomyelins (SM) and ceramides (Cer) with nonhydroxy and 2-hydroxy very long chain PUFA (n-V and h-V) is a trait of differentiation in male rat germ cells. Here we evaluated how these lipids distribute among cell membranes as differentiation proceeds from pachytene spermatocytes to round and late spermatids, in relation to glycerophospholipids (GPL) and cholesterol. A small light (L) and a larger heavy (H) fraction, both derived from the plasma membrane, and a bulky fraction containing intracellular membranes were obtained. In the three cell stages, the L fraction concentrated Flotillin-1, indicating the existence of rafts membrane domains. This fraction had relatively more SM and more cholesterol than the H fraction in spermatocytes, and also more SM, but less cholesterol, in the two spermatids. In the three cases, the SM of L was rich in saturated fatty acids (SFA), whereas that of H contained virtually all the n-V and h-V of the plasma membrane. The GPL of L and H contained SFA and PUFA, respectively. The intracellular membrane fraction of the three cells contained most of the n-V and h-V Cer species of the cells, likely precursors of the SMs that in due course are incorporated in their plasma membranes. Thus, the global lipid composition and the distribution of lipids among cell membranes are significantly transformed during male germ cell differentiation.