MagRET Nanoparticles: An Iron Oxide Nanocomposite Platform for Gene Silencing from MicroRNAs to Long Noncoding RNAs

Silencing of RNA to knock down genes is currently one of the top priorities in gene therapies for cancer. However, to become practical the obstacle of RNA delivery needs to be solved. In this study, we used innovative maghemite (γ-Fe2O3) nanoparticles, termed magnetic reagent for efficient transfection (MagRET), which are composed of a maghemite core that is surface-doped by lanthanide Ce(3/4+) cations using sonochemistry. Thereafter, a polycationic polyethylenimine (PEI) polymer phase is bound to the maghemite core via coordinative chemistry enabled by the [CeL(n)](3/4+)cations/complex. PEI oxidation was used to mitigate the in vivo toxicity. Using this approach, silencing of 80-100% was observed for mRNAs, microRNAs, and lncRNA in a variety of cancer cells. MagRET NPs are advantageous in hard to transfect leukemias. This versatile nanoscale carrier can silence all known types of RNAs and these MagRET NPs with oxidized PEI are not lethal upon injection, thus holding promise for therapeutic applications, as a theranostic tool.

Dephosphorylation of cAMP-dependent protein kinase regulatory subunit in stimulated parietal cells

The phosphorylation of endogenous proteins was investigated in subcellular fractions prepared from isolated rabbit parietal cells incubated with either cimetidine (unstimulated) or a combination of histamine and forskolin (maximally stimulated). Phosphorylation of endogenous proteins in subfractions was then assessed in a post hoc assay using [gamma-32P]ATP as a phosphate donor in vitro. The Mg(2+)-dependent incorporation of [32P]phosphate into a 52-kDa protein (pp52M) was observed in the 4,000 g membrane fraction from stimulated but not unstimulated cells. The pp52M protein was identified as the type II regulatory subunit of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase (RII) by isoelectric focusing, comigration with cAMP-binding proteins, and immunoprecipitation. Incorporation of [32P]phosphate into RII in the in vitro assay in the presence of Zn2+ was apparent in the 4,000 g membrane from stimulated but not unstimulated cells. The results thus suggested that, on stimulation, RII in membrane was dephosphorylated. Incorporation of [32P]phosphate into membrane-associated RII was completely abolished in the presence of 10 microM cAMP. The decrease in RII phosphorylation in membrane from stimulated cells assayed in the presence of cAMP was due to a phosphoprotein phosphatase activity that was completely inhibited by okadaic acid (1 microM). The results indicate that stimulation of parietal cells with histamine and forskolin results in the dephosphorylation of membrane bound RII by a protein phosphatase that is also membrane associated. Furthermore, okadaic acid inhibited histamine-stimulated accumulation of [14C]aminopyrine into isolated parietal cells without altering stimulated increases in cAMP. Thus protein phosphatase may be a significant regulator of parietal cell function.

Effects of epidermal growth factor on signal transduction in rabbit parietal cells

The aim of this study was to elucidate the cellular mechanisms of action of epidermal growth factor (EGF) inhibition of parietal cell secretion. EGF effects on histamine- and carbachol-stimulated [14C]aminopyrine (AP) uptake and intrinsic factor (IF) secretion were evaluated in isolated rabbit parietal cells. EGF inhibited histamine-stimulated [14C]AP uptake and IF secretion through a reduction in stimulated adenosine 3',5'-cyclic monophosphate (cAMP) levels. EGF decreased the phosphorylation of a cytosolic 30-kDa, histamine-stimulated, cAMP-dependent protein kinase substrate. These effects on histamine-stimulated activation were reversed by pertussis toxin preincubation. EGF inhibited carbachol-stimulated [14C]AP uptake and IF secretion, but did not alter the carbachol-stimulated Ca2+ transient. These results indicate that EGF inhibits histamine-stimulated secretion through the inhibitory Gi guanosine 5'-triphosphate-binding protein and carbachol-stimulated secretion through a mechanism independent of the activation of an increase in intracellular Ca2+.

Pancreastatin: a novel peptide inhibitor of parietal cell signal transduction

The direct inhibition of secretion by pancreastatin was investigated in rabbit isolated parietal cells. Pancreastatin exerted no influence on basal aminopyrine uptake. Pancreastatin inhibited histamine stimulated aminopyrine uptake through a decrease in intracellular cAMP. Pancreastatin inhibition of histamine stimulated uptake was blocked in the presence of pertussis toxin. Pancreastatin also inhibited the carbachol stimulated increase in aminopyrine accumulation. However, the effects of pancreastatin on carbachol stimulation were not reversed by pertussis toxin. Pancreastatin did not alter the carbachol induced increase in cytosolic free calcium. Thus, pancreastatin appears to inhibit parietal cell signal transduction at multiple points along the second messenger pathways.