Riboni L, Bassi R, Prinetti A, Tettamanti G
Department of Medical Chemistry and Biochemistry, Medical School, University of Milan, Italy.
FEBS Lett. 1996 Aug 12;391(3):336-40. doi: 10.1016/0014-5793(96)00772-7.
Cerebellar granule cells in culture were subjected to a pulse (0.5-4 h)-chase (0-4 h) of 10(-6) M [3H]ganglioside GM1 carrying the radioactive label at the level of NeuAc ([3H-NeuAc]GM1), Sph ([3H-Sph]GM1) or Gal ([3H-Gal]GM1) and the formed [3H]metabolites were determined. With all forms of [3H]GM1, there was formation of [3H]catabolites, including [3H]H2O and [3H]biosynthetic products obtained by recycling of [3H]NeuAc, [3H]Sph and [3H]Gal released during intralysosomal ganglioside degradation (salvage processes). Much higher amounts of [3H]H2O were produced from [3H-Gal]GM1 than [3H-Sph]GM1 and [3H-NeuAc]GM1; conversely, more products from salvage processes (polysialogangliosides GD1a, GD1b, GT1b, O-acetylated GT1b, protein-bound radioactivity) were obtained with [3H-NeuAc]GM1 than the two other forms of [3H]GM1. Liberated [3H]NeuAc produced 10-fold less tritiated water and 10-fold higher salvage products than [3H]Gal. Using [3H-NeuAc]GM1, granule cells appeared to metabolize 7.7% of membrane-incorporated exogenous GM1 per hour with a high degree of NeuAc recycling and the calculated metabolic half-life was 6.5 h.
将培养的小脑颗粒细胞用10⁻⁶ M携带放射性标记于NeuAc（[³H-NeuAc]GM1）、Sph（[³H-Sph]GM1）或Gal（[³H-Gal]GM1）水平的[³H]神经节苷脂GM1进行脉冲（0.5 - 4小时）-追踪（0 - 4小时）处理，并测定形成的[³H]代谢产物。对于所有形式的[³H]GM1，均有[³H]分解代谢产物的形成，包括[³H]H₂O以及通过溶酶体内神经节苷脂降解过程中释放的[³H]NeuAc、[³H]Sph和[³H]Gal的再循环获得的[³H]生物合成产物（挽救过程）。从[³H-Gal]GM1产生的[³H]H₂O量远高于[³H-Sph]GM1和[³H-NeuAc]GM1；相反，与其他两种形式的[³H]GM1相比，用[³H-NeuAc]GM1获得的挽救过程产物（多唾液酸神经节苷脂GD1a、GD1b、GT1b、O-乙酰化GT1b、蛋白质结合放射性）更多。释放的[³H]NeuAc产生的氚化水比[³H]Gal少10倍，挽救产物比[³H]Gal高10倍。使用[³H-NeuAc]GM1时，颗粒细胞似乎每小时代谢7.7%的膜结合外源性GM1，具有高度的NeuAc再循环，计算得出的代谢半衰期为6.5小时。
