Glutamate clearance by astrocytes is critical for controlling excitatory neurotransmission and ATP is an important mediator for neuron‐astrocyte interaction. However, the effect of ATP on glutamate clearance has never been examined. Here we report that treatment of RBA‐2 cells, a type‐2‐like astrocyte cell line, with ATP and the P2X7 receptor selective agonist 3′‐O‐(4‐benzoylbenzoyl) adenosine 5′‐triphosphate (BzATP) decreased the Na+‐dependent [3H]glutamate uptake within minutes. Mechanistic studies revealed that the decreases were augmented by removal of extracellular Mg2+ or Ca2+, and was restored by P2X7 selective antagonist , periodate‐oxidized 2′,3′‐dialdehyde ATP (oATP), indicating that the decreases were mediated through P2X7 receptors. Furthermore, stimulation of P2X7 receptors for 2 h inhibited both activity and protein expression of glutamine synthetase (GS), and oATP abolished the inhibition. In addition, removal of extracellular Ca2+ and inhibition of protein kinase C (PKC) restored the ATP‐decreased GS expression but failed to restore the P2X7‐decreased [3H]glutamate uptake. Therefore, P2X7‐mediated intracellular signals play a role in the down‐regulation of GS activity/expression. Activation of P2X7 receptors stimulated increases in intracellular Na+ concentration ([Na+]i) suggesting that the P2X7‐induced increases in [Na+]i may affect the local Na+ gradient and decrease the Na+‐dependent [3H]glutamate uptake. These findings demonstrate that the P2X7‐mediated decreases in glutamate uptake and glutamine synthesis were mediated through distinct mechanisms in these cells.

Pseudouridine () synthases function in the formation of , the most abundant of the modified RNA residues. All  synthases in E. coli are classified into one of five families according to their sequences. Among them, members of the RluA  synthase family catalyze certain  formations in ribosomal RNA. RluA family members are required for ribosomal assembly and bacterial growth. None of the RluA in multicellular organisms has been studied. In the Drosophila peripheral nervous system, multiple dendritic (MD) neurons are recognized by their dendritic arbors. MD neurons can also be identified by using the enhancer trap line E7-2-36, which expresses the lacZ gene in MD neurons. Here, we show that the P-element of E7-2-36 inserts into the Drosophila RluA-1 gene. RluA-1 is homologous to E. coli RluA family members and is evolutionarily conserved in multicellular organisms. In situ hybridization and immunocytochemistry revealed that RluA-1 is expressed in MD neurons. We investigated the RluA-1 enhancer responsible for MD expression and found that the membrane-tethered green fluorescent protein driven by RluA-1-GAL4 was expressed in the dendritic arbors of MD neurons, confirming that RluA-1 is indeed expressed in MD neurons. Thus, the expression of RluA-1 is spatially controlled during development. KEY WORDS: pseudouridine synthase, multiple dendritic neuronPseudouridine () is the most common modified nucleotide in cellular RNAs (Rozenski et al., 1999).  is synthesized from uridine by  synthases. According to the amino acid sequence,  synthases have been classified into five families: TruD, TruA, TruB, RsuA, and RluA (Kaya and Ofengand, 2003, Koonin, 1996). All  synthases share a conserved active site cleft containing catalytic aspartate (Hamma and Ferre-D'Amare, 2006). In E. coli and yeasts, it is known that each  synthase functions in the synthesis of specific  residues in tRNA or rRNA. For example, the RluA family member RluD in E. coli is responsible for the formation of  residues in rRNA. Lack of RluD causes defects in ribosomal assembly and bacterial growth (Gutgsell et al., 2005). In addition,  synthases may have functions other than  synthesis, such as being an RNA chaperone (Grosshans et al., 2001). In humans, the TruB  synthase dyskerin is involved in an RNP complex, which is required for rRNA processing and telomerase activity as well as  synthesis (Hamma and Ferre-D'Amare, 2006). Mutation in dyskerin causes the human bone marrow failure syndrome dyskeratosis congenita (Heiss et al., 1998). No RluA family  synthases in multicellular organisms have been Int. J. Dev. Biol. 55: 223-227 (2011) doi: 10.1387/ijdb.103112cw Abbreviations used in this paper: PNS, peripheral nervous system; MD, multiple dendritic; , pseudouridine. investigated.The Drosophila embryonic peripheral nervous system (PNS) consists of type I and type II neurons Jan, 1993, Jan andJan, 1994). Type I neurons locate within external sensory (ES) and chordotonal (CH) organs. Each of the type I neurons has one dendrite, whe...

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Cisplatin is a platinum based chemotherapy drug used to treat various types of cancers, including sarcomas, some carcinomas, lymphomas and germ cell tumors. In this study human ovarian cancer cell lines, OVCA429 and ALST, were challenged with different concentrations of cisplatin (1E‐6M, 1E‐5M, 5E‐5M and 1E‐4M) and the effects on cancer cell morphology and micromotion were monitored and analyzed by electric cell‐substrate impedance sensing (ECIS) and microscopy. Moreover, the transendothelial invasion of the ovarian cancer cells to human umbilical vein endothelial cells (HUVECs) was examined. Our measurements showed that 1E‐4M of cisplatin caused a decrease of junctional resistance between cells and the reduction in micromotion. In addition, 1E‐6M and 1E‐5M of cisplatin were not toxic to the integrity of HUVEC layers but effectively inhibited transendothelial invasion of ovarian cancer cells. Thus, we report a strategic approach for using ECIS to analyze potential drugs for their abilities to suppress metastasis, particularly at the level of transendothelial invasion. Grant Funding Source: Supported by the National Science Council in Taiwan

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