Sialosyl cholesterol induces morphological and biochemical differentiations of glioblasts without intracellular cyclic AMP level rise.

Synthesized sialosyl cholesterols, alpha- and beta-D-N-acetylneuraminyl cholesterols (alpha-SC and beta-SC), induced the morphological conversion of normal rat glioblasts from a flat epithelioid morphology to an astrocytic process-bearing (stellate) morphology resembling the conversion by glia maturation factor (GMF). The stellogenic effects were rapid and detectable within 1 h after drug stimulation, and irrelevant to the intracellular cyclic adenosine monophosphate (cAMP) levels. The morphological alteration was ascertained by the fluorescence-visualization of cytoskeletons: alpha-SC elicited the reorganization of GFA protein network to the formation of bundles, the destruction of stress fiber, and the redistribution as plasmalemmal constituents. alpha-SC also evoked biological differentiations represented by an elevation of glial marker proteins, S-100 protein and GFA protein. The results provide a possibility that SC incorporated into plasma membrane may cause morphologically and biochemically astrocyte-like differentiations of glioblast through the alteration of membrane characteristics, the cytoskeletal anchorages to the membrane, the affinity of receptors, and/or the postreceptor responses distinct from cAMP-production system.