No abstract

Excitatory NMDA receptors are an important target of ethanol. Chronic ethanol exposure, in vivo and in vitro, increases polypeptide levels of NR1 subunit, the key subunit of functional NMDA receptors. In vitro, chronic ethanol treatment increases the half-life of NR1 mRNA and this observation is dependent on new protein synthesis. The present study was undertaken to locate cis-acting region(s) within the NR1 3'-untranslated region (UTR) and identify NR1 3'-UTR binding trans-acting proteins expressed in mouse fetal cortical neurons. Utilizing RNA gel shift assays we identified a 156-nt cis-acting region that binds to polysomal trans-acting proteins. This binding was highly specific as inclusion of cyclophilin RNA or tRNA did not interfere with cis-trans interactions. Importantly, the 3'-UTR binding activity was significantly up-regulated in the presence of ethanol. UV cross-link analysis detected three NR1 3'-UTR binding proteins and their molecular mass calculated by Northwestern analysis was approximately 88, 60 and 47 kDa, respectively. Northwestern analysis showed a significant up-regulation of the 88-kDa protein after chronic ethanol treatment. The 88-kDa protein was purified and identified by tandem mass spectrometry as the beta subunit of alpha glucosidase II (GIIbeta). That GIIbeta is indeed a trans-acting protein and binds specifically to 3'-UTR of NR1 mRNA was confirmed by RNA gel mobility supershift assays and immuno RT-PCR. Western blotting data established a significant increase of GIIbeta polypeptide in chronic ethanol-exposed fetal cortical neurons. We hypothesize that the identified cis-acting region and the associated RNA-binding proteins are important regulators of NR1 subunit gene expression.

No abstract

con®rmed that PKC was involved in the regulation of 5-HT 2A receptor mRNA by agonist and implicate the conventional subgroup of PKC isoforms. Western blot analysis, using isoform-speci®c anti-PKC antibodies showed that under our culture conditions C6 glioma cells express the conventional isoforms PKC a, PKC g, as well as the novel isoforms PKC d, PKC 1, and the atypical isoforms PKC l and PKC i. Upon treatment with 5-HT for 10 min levels of the conventional isoforms PKC a and PKC g increased in the nuclear fraction. Taken together, our results implicate PKC a and/or PKC g in the regulation of 5-HT 2A mRNA receptor and binding sites in response to agonist treatment.

A cis-acting region, Δ4, located in the 3′-untranslated region of N-methyl-D-aspartate R (NR) mRNA interacts with several trans-acting proteins present in polysomes purified from fetal cortical neurons. Chronic ethanol exposure of fetal cortical neurons increases Δ4 RNA–protein interactions. This increased interaction is due to an increase in one of the Δ4-binding trans-acting proteins identified as beta subunit of alpha glucosidase II (GIIβ). In this study, we examined whether ethanol-mediated regulation of NR1 mRNA in vivo is similar to that in vitro and whether Δ4–trans interactions are important for ethanol-mediated NR1 mRNA stability. Our data show that polysomal proteins from adult mouse cerebral cortex (CC) formed a complex with Δ4 RNA, suggesting the presence of NR1 mRNA-binding trans-acting proteins in CC polysomes. The intensity of the Δ4 RNA–protein complex was increased with polysomes from chronic ethanol-exposed CC. The Δ4 RNA–protein complex harbored GIIβ and a second trans-acting protein identified as annexin A2 (AnxA2). Ethanol-sensitive GIIβ was upregulated by 70% in ethanol-exposed CC. Heparin, a known binding partner of AnxA2, inhibited Δ4 RNA–protein complex formation. Transient transfection studies using chimeric constructs with and without the Δ4 region revealed that cis–trans interactions are important for ethanol-mediated stability of NR1 mRNA. Furthermore, our data highlight, for the first time, the presence of a binding site on the 3′-untranslated region of NR1 mRNA for AnxA2 and demonstrate the regulation of NR1 mRNA by AnxA2, GIIβ and a third NR1 mRNA-binding protein, which is yet to be identified.