GANGLIOSIDE GT1B AND GQ1B AS THE MARKER OF SYNAPSE FORMATION IN P19EC CELLS

研究了小鼠胚胎癌细胞P19神经分化过程中神经节苷脂的变化及其酶基础。该细胞系经维甲酸（RA）处理后可分化为神经元和星形胶质细胞，经二甲基亚砜（DMSO）处理后可分化为肌肉细胞。用单克隆抗体（MAb） R24薄层色谱（TLC）免疫染色检测，在RA处理的聚集体中明显存在GD3。神经元中GM3合成酶（alpha2,3-sia1yltransferase, SAT-I）活性最高。通过Northern blotting分析，GD3合成酶（alpha2,8-唾液基转移酶，SAT-II）和GD3合成酶mRNA在RA诱导的聚集体和神经元中也显著存在。然而，在诱导肌肉细胞的DMSO处理下，GD3合成酶活性水平没有变化，并且在肌肉分化过程中几乎没有检测到其转录物。GTlb合成酶（alpha2,3-唾液基转移酶，SAT-IV）在未分化细胞和RA处理的聚集体中以相似的水平存在，但在神经元中观察到更高的水平。另一方面，ra诱导的聚集体中GQlb合成酶（alpha2,8-唾液基转移酶，SAT-V）的水平显著高于神经元。上述结果表明，RA可诱导胚胎癌P19细胞神经分化过程中神经节苷脂生物合成途径中GM3、GD3、GTlb和GQlb合成酶的表达，特别是GD3合成酶mRNA的表达。

We have studied ganglioside alterations and their enzymatic basis during the course of neural differentiation of mouse embryonic carcinoma cell line P19. This cell line can differentiate into neurons and astrocytes on cell aggregation after treatment with retinoic acid (RA) or into muscle cells on dimethyl sulfoxide (DMSO) treatment. GD3, detected on immunostaining after thin-layer chromatography (TLC) with monoclonal antibody (MAb) R24, was markedly present in aggregates treated with RA.GM3 synthase (alpha2,3-sia1yltransferase, SAT-I) in neurons was found to exhibit the highest activity. GD3 synthase (alpha2,8-sialyltransferase, SAT-II) and GD3 synthase mRNA, as analyzed by Northern blotting, were also markedly present in aggregates and neurons induced by RA.However, on treatment with DMSO, which induces muscle cells, there was no change in the level of GD3 synthase activity, and its transcript was hardly detected during the course of muscle differentiation. GTlb synthase (alpha2,3-sialyltransferase, SAT-IV) was present at similar levels in undifferentiated cells and aggregates treated with RA, but a higher level was observed in neurons. On the other hand, the level of GQlb synthase (alpha2,8-sialyltransferase, SAT-V) in RA-induced aggregates was significantly higher than that in neurons. These results show that RA but not DMS0 induces the expression of GM3, GD3, GTlb and GQlb synthases, and particularly GD3 synthase mRNA, in the ganglioside biosynthetic pathway during the neural differentiation of embryonic carcinoma P19 cells.