Megias L, Guerri C, Fornas E, Azorin I, Bendala E, Sancho-Tello M, Durán J M, Tomás M, Gomez-Lechon M J, Renau-Piqueras J
Departamento de Ciencias Morfológicas, Universidad de Granada, Spain.
Int J Dev Biol. 2000 Feb;44(2):209-21.
Endocytosis constitutes an essential process in the regulation of the expression of cell surface molecules and receptors and, therefore, could participate in the neural-glial interactions occurring during brain development. However, the relationship between endocytic pathways in astroglial cells under physiological and pathological conditions remains poorly understood. We analyzed the endocytosis and transcytosis processes in growing astrocytes and the possible effect of ethanol on these processes. Evidence demonstrates that ethanol affects endocytosis in the liver and we showed that ethanol exposure during brain development alters astroglial development changing plasma membrane receptors and surface glycoprotein composition. To study these processes we use several markers for receptor-mediated endocytosis, fluid phase endocytosis and non-specific endocytosis. These markers were labeled for fluorescence microscopy and electron microscopy. 125I-BSA was used to study the effect of ethanol on the internalization and recycling of this macromolecule. The distribution of several proteins involved in endocytosis (caveolin, clathrin, rab5 and beta-COP) was analyzed using immunofluorescence, immunoelectron microscopy and immunoblotting. Our results indicate that growing astrocytes have a developed endocytic system mainly composed of caveolae, clathrin coated pits and vesicles, tubulo-vesicular and spheric endosomes, multivesicular bodies and lysosomes. Ethanol exposure induces a fragmentation of tubular endosomes, decreases the internalization of 125I-BSA, alters the processing of internalized BSA, and decreases the levels of caveolin, clathrin, rab5 and beta-COP. These results indicate that ethanol alters the endocytosis and transcytosis processes and impairs protein trafficking in astrocytes, which could perturb astrocyte surface expression of molecules involved in neuronal migration and maturation during brain development.
内吞作用是调节细胞表面分子和受体表达的一个重要过程，因此可能参与大脑发育过程中发生的神经胶质细胞间相互作用。然而，在生理和病理条件下，星形胶质细胞内吞途径之间的关系仍知之甚少。我们分析了生长中的星形胶质细胞的内吞作用和转胞吞作用过程，以及乙醇对这些过程可能产生的影响。有证据表明乙醇会影响肝脏中的内吞作用，并且我们发现大脑发育过程中暴露于乙醇会改变星形胶质细胞的发育，改变质膜受体和表面糖蛋白的组成。为了研究这些过程，我们使用了几种用于受体介导的内吞作用、液相内吞作用和非特异性内吞作用的标志物。这些标志物用荧光显微镜和电子显微镜进行标记。使用¹²⁵I-牛血清白蛋白（¹²⁵I-BSA）来研究乙醇对这种大分子内化和再循环的影响。使用免疫荧光、免疫电子显微镜和免疫印迹分析了几种参与内吞作用的蛋白质（小窝蛋白、网格蛋白、rab5和β-COP）的分布。我们的结果表明，生长中的星形胶质细胞具有发达的内吞系统，主要由小窝、网格蛋白包被小窝和小泡、管状-小泡状和球形内体、多囊泡体和溶酶体组成。乙醇暴露会诱导管状内体碎片化，降低¹²⁵I-BSA的内化，改变内化BSA的加工过程，并降低小窝蛋白、网格蛋白、rab5和β-COP的水平。这些结果表明，乙醇改变了内吞作用和转胞吞作用过程，并损害了星形胶质细胞中的蛋白质运输，这可能会扰乱大脑发育过程中参与神经元迁移和成熟的分子在星形胶质细胞表面的表达。
