Daniotti J L, Rosales Fritz V, Kunda P, Nishi T, Maccioni H J
Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC (UNC-CONICET), Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina.
Int J Dev Neurosci. 1997 Oct;15(6):767-76. doi: 10.1016/s0736-5748(97)00027-0.
GD3 and GM2 synthases act on ganglioside GM3 at the branching point of the pathway of synthesis of gangliosides in which the "a", "b" and "c" families are produced. The relative activities of these enzymes are important for regulating the ganglioside composition of a given tissue. In the present work, we report the cloning and characterization of a chick GD3 synthase cDNA. The cloned cDNA directed the synthesis of a functionally active enzyme in transiently transfected CHO-K1 cells and was highly homologous to mammalian GD3 synthases. In Northern blot experiments the cDNA detected a single specific GD3 synthase mRNA of about 9.0 kb both in the chicken brain and retina. The abundance of the specific mRNA transcript declined steadily from E7-E9 to very low values around PN2. The levels of enzyme activities measured at the same developmental stages roughly followed the changes of specific mRNA levels in both tissues. In situ hybridization of embryonic neural retina cells in culture showed that both glial- and neuron-like cells expressed the specific GD3 synthase mRNA, although with different intensities. Results indicate that transcription and/or stability of the specific GD3 synthase mRNA constitute a level of control of the expression of GD3 synthase and indirectly of the ganglioside composition in the developing chicken central nervous system (CNS).
GD3合酶和GM2合酶作用于神经节苷脂GM3，该神经节苷脂位于神经节苷脂合成途径的分支点，在此途径中产生了“a”、“b”和“c”家族。这些酶的相对活性对于调节特定组织的神经节苷脂组成很重要。在本研究中，我们报道了鸡GD3合酶cDNA的克隆和特性分析。克隆的cDNA在瞬时转染的CHO-K1细胞中指导合成一种功能活性酶，并且与哺乳动物GD3合酶高度同源。在Northern印迹实验中，该cDNA在鸡脑和视网膜中均检测到一条约9.0 kb的单一特异性GD3合酶mRNA。从胚胎第7天到第9天，该特异性mRNA转录本的丰度稳步下降，在出生后第2天左右降至非常低的值。在相同发育阶段测得的酶活性水平在两个组织中大致遵循特异性mRNA水平的变化。对培养的胚胎神经视网膜细胞进行原位杂交显示，神经胶质样细胞和神经元样细胞均表达特异性GD3合酶mRNA，尽管表达强度不同。结果表明，特异性GD3合酶mRNA的转录和/或稳定性构成了发育中的鸡中枢神经系统（CNS）中GD3合酶表达以及间接神经节苷脂组成的一种调控水平。
