Peñalver Ana, Campos-Sandoval José A, Blanco Eduardo, Cardona Carolina, Castilla Laura, Martín-Rufián Mercedes, Estivill-Torrús Guillermo, Sánchez-Varo Raquel, Alonso Francisco J, Pérez-Hernández Mercedes, Colado María I, Gutiérrez Antonia, de Fonseca Fernando Rodríguez, Márquez Javier
Canceromics Laboratory, Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Universidad de Málaga, Campus de TeatinosMálaga, Spain.
Unidad de Gestión Clínica de Salud Mental, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de MálagaMálaga, Spain.
Front Mol Neurosci. 2017 Sep 5;10:278. doi: 10.3389/fnmol.2017.00278. eCollection 2017.
Lysophosphatidic acid (LPA) is an extracellular lipid mediator that regulates nervous system development and functions acting through G protein-coupled receptors (GPCRs). Here we explore the crosstalk between LPA receptor and glutamatergic transmission by examining expression of glutaminase (GA) isoforms in different brain areas isolated from wild-type (WT) and KOLPA mice. Silencing of LPA receptor induced a severe down-regulation of Gls-encoded long glutaminase protein variant (KGA) (glutaminase gene encoding the kidney-type isoforms, GLS) protein expression in several brain regions, particularly in brain cortex and hippocampus. Immunohistochemical assessment of protein levels for the second type of glutaminase (GA) isoform, glutaminase gene encoding the liver-type isoforms (GLS2), did not detect substantial differences with regard to WT animals. The regional mRNA levels of GLS were determined by real time RT-PCR and did not show significant variations, except for prefrontal and motor cortex values which clearly diminished in KO mice. Total GA activity was also significantly reduced in prefrontal and motor cortex, but remained essentially unchanged in the hippocampus and rest of brain regions examined, suggesting activation of genetic compensatory mechanisms and/or post-translational modifications to compensate for KGA protein deficit. Remarkably, Golgi staining of hippocampal regions showed an altered morphology of glutamatergic pyramidal cells dendritic spines towards a less mature filopodia-like phenotype, as compared with WT littermates. This structural change correlated with a strong decrease of active matrix-metalloproteinase (MMP) 9 in cerebral cortex and hippocampus of KOLPA mice. Taken together, these results demonstrate that LPA signaling through LPA influence expression of the main isoenzyme of glutamate biosynthesis with strong repercussions on dendritic spines maturation, which may partially explain the cognitive and learning defects previously reported for this colony of KOLPA mice.
溶血磷脂酸（LPA）是一种细胞外脂质介质，通过G蛋白偶联受体（GPCR）调节神经系统的发育和功能。在此，我们通过检测从野生型（WT）和KOLPA小鼠分离的不同脑区中谷氨酰胺酶（GA）同工型的表达，来探索LPA受体与谷氨酸能传递之间的相互作用。LPA受体的沉默导致几种脑区中由Gls编码的长谷氨酰胺酶蛋白变体（KGA）（编码肾型同工型的谷氨酰胺酶基因，GLS）蛋白表达严重下调，尤其是在大脑皮层和海马体中。对第二种谷氨酰胺酶（GA）同工型（编码肝型同工型的谷氨酰胺酶基因，GLS2）的蛋白水平进行免疫组织化学评估，未发现与WT动物有实质性差异。通过实时RT-PCR测定GLS的区域mRNA水平，除了KO小鼠前额叶和运动皮层的值明显降低外，未显示出显著变化。前额叶和运动皮层中的总GA活性也显著降低，但在海马体和其他检测的脑区中基本保持不变，这表明激活了基因补偿机制和/或翻译后修饰以补偿KGA蛋白的缺乏。值得注意的是，与WT同窝小鼠相比，海马区的高尔基染色显示谷氨酸能锥体细胞树突棘的形态发生改变，向不太成熟的丝状伪足样表型转变。这种结构变化与KOLPA小鼠大脑皮层和海马体中活性基质金属蛋白酶（MMP）9的强烈减少相关。综上所述，这些结果表明，通过LPA的LPA信号传导影响谷氨酸生物合成主要同工酶的表达，对树突棘成熟有强烈影响，这可能部分解释了先前报道的该KOLPA小鼠群体的认知和学习缺陷。
