Lysenin-sphingomyelin binding at the surface of oligodendrocyte lineage cells increases during differentiation in vitro

We have investigated the relationship between the developmental expression of sphingomyelin, a major component of myelin, and oligodendrocyte lineage. Using lysenin as a cytochemical probe for membrane sphingomyelin, we have now determined the distribution pattern of sphingomyelin on the plasma memb rane of rat cultured oligodendrocytes, Although lysenin does not bind to A2 B5(+)/NG2(+) bipolar oligodendrocyte progenitors, lysenin recognizes sphing omyelin on the cell bodies of multipolar A2B5(+) cells, but not on their pr ocesses. 04(+) and 01(+) immature and MBP+ mature oligodendrocytes are stro ngly labeled by lysenin from cell bodies to the tips of processes. The cont ent of sphingomyelin in immature and mature oligodendrocytes is approximate ly 2-fold higher than that in oligodendrocyte progenitors. These findings s how that sphingomyelin increases during differentiation of cells in the oli godendrocyte lineage. In multipolar oligodendrocyte progenitors exposed to Triton X-100 at 4 degreesC, lysenin labels cell processes in addition to ce ll bodies. In contrast, Triton X-100 extraction does not alter the distribu tion of lysenin binding on 04(+), 01(+) and MBP+ cells, although the immuno cytochemical intensities of the lysenin bindings increase. Our data suggest that the alteration in sphingomyelin content and distribution in the oligo dendrocyte lineage cells could have important consequences for cell recogni tion and downstream signaling events through sphingomyelin-rich domains. (C ) 2000 Wiley-Liss, Inc.