C6 glioma cells differentiated by retinoic acid overexpress the glutamate transporter excitatory amino acid carrier 1 (EAAC1)

• Published in: Neuroscience Vol. 151; no. 4; pp. 1042 - 1052
• Main Authors: Bianchi, M.G, Gazzola, G.C, Tognazzi, L, Bussolati, O
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 19.02.2008; Elsevier
• Subjects: Animals; Antineoplastic Agents - pharmacology; Aspartic Acid - metabolism; Aspartic Acid - pharmacology; Biological and medical sciences; Cell Differentiation - drug effects; Cell Line, Tumor; differentiation; Dose-Response Relationship, Drug; EAAT3; Excitatory Amino Acid Transporter 3 - antagonists & inhibitors; Excitatory Amino Acid Transporter 3 - metabolism; excitatory amino acids; Excitatory Amino Acids - pharmacology; excitotoxicity; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Neoplastic - drug effects; Glioma - pathology; Nerve Tissue Proteins - metabolism; neural stem cells; Neurology; oligodendrocytes; Rats; Tretinoin - pharmacology; Vertebrates: nervous system and sense organs; l-cysteinsulphinate; phorbol 12,13-dibutyrate; PDBu; differentiation; l-CSS; DHK; Gfap; class III β-tubulin; Plp; Earle’s balanced salt solution; FBS; dl- threo-b-benzyloxyaspartic acid; EAAC1; excitatory amino acid carrier 1; l-aspartate; excitotoxicity; EBSS; dihydrokainate; proteolipid protein; EAA; Tubb3; neural stem cells; excitatory amino acids; oligodendrocytes; EAAT3; EAAT; fetal bovine serum; excitatory amino acid transporter; excitatory amino acid; all- trans-retinoic acid; l-Asp; ATRA; glial fibrillary acidic protein; dl-TBOA; Rat; Toxicity; Neuroglia; Stem cell; Retinoid; Oligodendrocyte; Carrier protein; Glial cell; Rodentia; EAAT3 glutamate transporter; Glutamate; In vitro; Vertebrata; Mammalia; Cell line; Animal; Excitotoxicity; Neurotransmitter; Excitatory aminoacid; Differentiation; Retinoic acid
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2007.11.055

Abstract The transport of excitatory amino acids (EAA) in CNS is performed by a family of high affinity, sodium dependent carriers. One of these transporters, excitatory amino acid carrier 1 (EAAC1), is known to be regulated by several mechanisms that modify carrier abundance on the plasma membrane. Much less is known on EAAC1 regulation at the level of gene expression. Here we report that, in C6 rat glioma cells, a line recently described to contain neural stem-like cells, EAAC1 is markedly induced by all trans -retinoic acid (ATRA), a well known differentiating agent. Consistently, ATRA stimulates EAA transport, with the maximal effect observed at concentrations ≥1 μM. After 4 days of treatment with 10 μM ATRA, the transport Vmax is fivefold enhanced, Slc1a1 mRNA is increased by 400% compared with control, EAAC1 carrier is sixfold overexpressed and the C6 culture is greatly enriched of cells with bipolar morphology strongly positive for EAAC1 immunoreactivity. Compared with untreated cells, ATRA-treated C6 cells express less Slc1a3 mRNA, for the transporter GLAST, but significantly higher levels of Slc1a2 mRNA, for the transporter GLT-1, although no expression of either protein is detected with Western blot in both untreated and ATRA-treated cells. Consistently, the inhibition pattern of aspartate transport and its stimulation by phorbol esters are indicative of a transport process due to EAAC1 operation. Under the conditions adopted, ATRA treatment causes the induction of proteolipid protein, an oligodendrocytic marker. These results indicate that, in C6 cells, ATRA stimulates the expression of EAAC1, possibly as a step toward oligodendrocytic differentiation, and constitute the first demonstration of the induction of this transporter by a differentiating agent.