Effects of aged garlic extract and FruArg on gene expression and signaling pathways in lipopolysaccharide-activated microglial cells.

Aged garlic extract (AGE) is widely used as a dietary supplement on account of its protective effects against oxidative stress and inflammation. But less is known about specific molecular targets of AGE and its bioactive components, including N-α-(1-deoxy-D-fructos-1-yl)-L-arginine (FruArg). Our recent study showed that both AGE and FruArg significantly attenuate lipopolysaccharide (LPS)-induced neuroinflammatory responses in BV-2 microglial cells.

Evolutionary conservation supports ancient origin for Nudt16, a nuclear-localized, RNA-binding, RNA-decapping enzyme.

Nudt16p is a nuclear RNA decapping protein initially identified in Xenopus (X29) and known to exist in mammals. Here, we identified putative orthologs in 57 different organisms ranging from humans to Cnidaria (anemone/coral). In vitro analysis demonstrated the insect ortholog can bind RNA and hydrolyze the m(7)G cap from the 5'-end of RNAs indicating the Nudt16 gene product is functionally conserved across metazoans.

Association of guanine nucleotide-exchange protein BIG1 in HepG2 cell nuclei with nucleolin, U3 snoRNA, and fibrillarin.

BIG1, a brefeldin A-inhibited guanine nucleotide-exchange protein, activates class I ADP-ribosylation factors (ARF1-3) by catalyzing the replacement of bound GDP by GTP, an action critical for the regulation of protein transport in eukaryotic cells. Our earlier report [Padilla PI, Pancheco-Rodriguez G, Moss J, Vaughan M (2004) Proc Natl Acad Sci USA 101:2752-2757] that BIG1 concentrated in nucleoli of serum-starved HepG2 cells prompted us to identify molecules associated with BIG1 in dynamic nucleolar structures. Antibodies against BIG1 or nucleolin coprecipitated both proteins from nuclei, which was abolished by the incubation of nuclei with RNase A or DNase, indicating that the interaction depended on nucleic acids.

Metal determines efficiency and substrate specificity of the nuclear NUDIX decapping proteins X29 and H29K (Nudt16).

The Xenopus X29 protein was identified by its high affinity binding to U8 small nucleolar RNA, a small nucleolar RNA required for ribosome biogenesis. X29 and its human homologue H29K (Nudt16) are nuclear nucleoside diphosphatase proteins localized within foci in the nucleolus and nucleoplasm. These proteins can remove m(7)G and m(227)G caps from RNAs, rendering them substrates for 5'-3' exonucleases for degradation in vivo.

Crystal structures of U8 snoRNA decapping nudix hydrolase, X29, and its metal and cap complexes.

X29, a 25 kDa Nudix hydrolase from Xenopus laevis that cleaves 5' caps from U8 snoRNA, crystallizes as a homodimeric apoenzyme. Manganese binds crystals of apo-X29 to form holo-X29 only in the presence of nucleot(s)ide. Structural changes in X29 on nucleo-t(s)ide-assisted Mn(+2) uptake account for the observed cooperativity of metal binding.