Hashimoto Takeshi, Hussien Rajaa, Cho Hyung-Sook, Kaufer Daniela, Brooks George A
Department of Integrative Biology, University of California, Berkeley, California, United States of America.
PLoS One. 2008 Aug 13;3(8):e2915. doi: 10.1371/journal.pone.0002915.
To evaluate the presence of components of a putative Intracellular Lactate Shuttle (ILS) in neurons, we attempted to determine if monocarboxylate (e.g. lactate) transporter isoforms (MCT1 and -2) and lactate dehydrogenase (LDH) are coexpressed in neuronal mitochondria of rat brains. Immunohistochemical analyses of rat brain cross-sections showed MCT1, MCT2, and LDH to colocalize with the mitochondrial inner membrane marker cytochrome oxidase (COX) in cortical, hippocampal, and thalamic neurons. Immunoblotting after immunoprecipitation (IP) of mitochondria from brain homogenates supported the histochemical observations by demonstrating that COX coprecipitated MCT1, MCT2, and LDH. Additionally, using primary cultures from rat cortex and hippocampus as well as immunohistochemistry and immunocoprecipitation techniques, we demonstrated that MCT2 and LDH are coexpressed in mitochondria of cultured neurons. These findings can be interpreted to mean that, as in skeletal muscle, neurons contain a mitochondrial lactate oxidation complex (mLOC) that has the potential to facilitate both intracellular and cell-cell lactate shuttles in brain.
为了评估假定的细胞内乳酸穿梭（ILS）的成分在神经元中的存在情况，我们试图确定单羧酸（如乳酸）转运体亚型（MCT1和-2）和乳酸脱氢酶（LDH）是否在大鼠脑神经元线粒体中共表达。大鼠脑横截面的免疫组织化学分析显示，在皮质、海马和丘脑神经元中，MCT1、MCT2和LDH与线粒体内膜标记物细胞色素氧化酶（COX）共定位。对脑匀浆线粒体进行免疫沉淀（IP）后的免疫印迹分析通过证明COX与MCT1、MCT2和LDH共沉淀，支持了组织化学观察结果。此外，利用大鼠皮质和海马的原代培养物以及免疫组织化学和免疫共沉淀技术，我们证明了MCT2和LDH在培养神经元的线粒体中共表达。这些发现可以解释为，与骨骼肌一样，神经元含有线粒体乳酸氧化复合体（mLOC），其有可能促进脑内的细胞内和细胞间乳酸穿梭。
