Interaction of sialosyl cholesterol with the cell surface of rat astrocytes and its biological activities.
The interaction between sialosyl cholesterol (alpha- or beta-D-N-acetyl neuraminyl cholesterol, alpha- or beta-SC) and the plasma membrane of astrocytes was investigated by the use of 14C-labeled alpha- or beta-SC. Both alpha- and beta-SC were dose-dependently and time-dependently bound to rat astrocytes. The Scatchard plot analyses showed that rat astrocytes bound apparently 9.69 x 10(9) molecules of both alpha-SC/cell (apparent Kd = 2.29 x 10(-5) M) and beta-SC/cell (apparent Kd = 5.39 x 10(-5) M) at 37 degrees C. Both the binding of alpha-SC to astrocytes and the subsequent inhibition of DNA synthesis were decreased at the low temperature (4 degrees C), and also suppressed by serum proteins including albumin. One molecule of bovine serum albumin (BSA) bound 2.3 molecules of alpha-SC with the slightly lower Kd-value (8.03 x 10(-6) M) than that for the binding site on astrocytes. BSA not only suppressed the alpha-SC-binding to astrocytes but also increased its release from the cells to the culture media. Gangliosides such as GM1 and GM3 unaffected the alpha-SC-binding, promoted the small release of alpha-SC from the cell surface, and inhibited the morphological changes of astrocytes induced by alpha-SC. The mechanism of alpha-SC-binding to cultured astrocytes with reference to the effects of serum or gangliosides is discussed.
Ito
J
J
Department of Biochemistry, Nagoya City University Medical School, Japan.
Kato
T
T
Tanaka
R
R
D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000031:analogs & derivatives / Q000378:metabolism*; D005677:G(M1) Ganglioside / Q000494:pharmacology; D005679:G(M3) Ganglioside / Q000494:pharmacology; D051381:Rats; D012710:Serum Albumin, Bovine / Q000494:pharmacology
D005679:G(M3) Ganglioside; D012710:Serum Albumin, Bovine; D005677:G(M1) Ganglioside; D002784:Cholesterol