EXTRACELLULAR-MATRIX UP-REGULATES SYNTHESIS OF GLUCOSYLCERAMIDE-BASEDGLYCOSPHINGOLIPIDS IN PRIMARY SCHWANN-CELLS

The formation of basement membrane around Schwann cells that are in co ntact with axons is necessary for Schwann cell differentiation and mye lin formation in the peripheral nervous system, However, primary Schwa nn cells grown on basement membrane in the absence of neuronal influen ce show increased proliferation rather than differentiation, which imp lies that the signals generated by Schwann cell-basement membrane inte ractions are multipotential, We examined the effect of matrigel, an ex ogenous basement membrane preparation, and other extracellular matrix growth surfaces on primary Schwann cells to determine if the resulting interactions play a role in the control of glycosphingolipid synthesi s, Isolated primary Schwann cells grown on a thin layer of matrigel ra pidly adhered to the surface and exhibited a greater degree of cell sp reading when compared to cells grown on the nonspecific substrate poly lysine. Labeling of the cells with [H-3]galactose between 24 and 48 hr after plating revealed that the incorporation of [H-3]galactose into glucosylceramide-based glycosphingolipids increased from 1.5-3-fold on matrigel in comparison to cells grown on polylysine. The major labele d glycolipids under both conditions were GM3 ganglioside and two neutr al glycolipids that comigrated with GbOse(4)Cer (GalNAc beta 1-3Gal al pha 1-4Gal beta 1-1Cer) and GbOse(5)Cer (GalNAc alpha 1-3Gal-NAc beta 1-3Gal alpha 1 -4Gal beta 1-4Glc beta 1-1Cer) standards. There was lit tle or no increase in the incorporation of [H-3]leucine, [H-3]galactos e, or [H-3]glucosamine into proteins or [H-3]palmitic acid into phosph olipids, free ceramides, or sphingomyelin, suggesting that the matrige l-induced increase in the synthesis of the glycolipids was selective, In the absence of serum, there was little or no difference in the leve ls of glycolipid labeling between cells grown on the two substrata, de monstrating that serum factors were required for matrigel to have this effect, When cells were grown on surfaces coated with individual extr acellular matrix components, those cells grown on laminin and collagen IV showed an increase in glycolipid labeling similar to that produced by matrigel, while labeling increased to a lesser degree for the othe r components tested, Thus, the signals generated by interactions betwe en Schwann cells and basement membrane, particularly the laminin and c ollagen IV constituents, contribute to the regulation of glycolipid sy nthesis which in turn may affect cell morphology and proliferation. (C ) 1996 Wiley-Liss, Inc.