Children's Hospital Oakland Research Institute

About: Children's Hospital Oakland Research Institute is a based out in . It is known for research contribution in the topics: Population & Human leukocyte antigen. The organization has 1568 authors who have published 2480 publications receiving 203418 citations.

Moving Fe2+ from ferritin ion channels to catalytic OH centers depends on conserved protein cage carboxylates

Abstract: Ferritin biominerals are protein-caged metabolic iron concentrates used for iron-protein cofactors and oxidant protection (Fe(2+) and O2 sequestration). Fe(2+) passage through ion channels in the protein cages, like membrane ion channels, required for ferritin biomineral synthesis, is followed by Fe(2+) substrate movement to ferritin enzyme (Fox) sites. Fe(2+) and O2 substrates are coupled via a diferric peroxo (DFP) intermediate, λmax 650 nm, which decays to [Fe(3+)-O-Fe(3+)] precursors of caged ferritin biominerals. Structural studies show multiple conformations for conserved, carboxylate residues E136 and E57, which are between ferritin ion channel exits and enzymatic sites, suggesting functional connections. Here we show that E136 and E57 are required for ferritin enzyme activity and thus are functional links between ferritin ion channels and enzymatic sites. DFP formation (Kcat and kcat/Km), DFP decay, and protein-caged hydrated ferric oxide accumulation decreased in ferritin E57A and E136A; saturation required higher Fe(2+) concentrations. Divalent cations (both ion channel and intracage binding) selectively inhibit ferritin enzyme activity (block Fe(2+) access), Mn(2+) << Co(2+) < Cu(2+) < Zn(2+), reflecting metal ion-protein binding stabilities. Fe(2+)-Cys126 binding in ferritin ion channels, observed as Cu(2+)-S-Cys126 charge-transfer bands in ferritin E130D UV-vis spectra and resistance to Cu(2+) inhibition in ferritin C126S, was unpredicted. Identifying E57 and E136 links in Fe(2+) movement from ferritin ion channels to ferritin enzyme sites completes a bucket brigade that moves external Fe(2+) into ferritin enzymatic sites. The results clarify Fe(2+) transport within ferritin and model molecular links between membrane ion channels and cytoplasmic destinations.

Coordinately regulated alternative splicing of genes involved in cholesterol biosynthesis and uptake

Abstract: Genes involved in cholesterol biosynthesis and uptake are transcriptionally regulated in response to cellular sterol content in a coordinated manner. A number of these genes, including 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and LDL receptor (LDLR), undergo alternative splicing, resulting in reductions of enzyme or protein activity. Here we demonstrate that cellular sterol depletion suppresses, and sterol loading induces, alternative splicing of multiple genes involved in the maintenance of cholesterol homeostasis including HMGCR and LDLR, the key regulators of cellular cholesterol biosynthesis and uptake, respectively. These changes were observed in both in vitro studies of the HepG2 human hepatoma derived cell line, as well as in vivo studies of St. Kitts vervets, also known as African green monkeys, a commonly used primate model for investigating cholesterol metabolism. These effects are mediated in part by sterol regulation of polypyrimidine tract binding protein 1 (PTBP1), since knock-down of PTBP1 eliminates sterol induced changes in alternative splicing of several of these genes. Single nucleotide polymorphisms (SNPs) that influence HMGCR and LDLR alternative splicing (rs3846662 and rs688, respectively), have been associated with variation in plasma LDL-cholesterol levels. Sterol-induced changes in alternative splicing are blunted in carriers of the minor alleles for each of these SNPs, indicating an interaction between genetic and non-genetic regulation of this process. Our results implicate alternative splicing as a novel mechanism of enhancing the robust transcriptional response to conditions of cellular cholesterol depletion or accumulation. Thus coordinated regulation of alternative splicing may contribute to cellular cholesterol homeostasis as well as plasma LDL levels.

Solving Biology’s Iron Chemistry Problem with Ferritin Protein Nanocages

Abstract: ConspectusFerritins reversibly synthesize iron-oxy(ferrihydrite) biominerals inside large, hollow protein nanocages (10–12 nm, ∼480 000 g/mol); the iron biominerals are metabolic iron concentrates for iron protein biosyntheses. Protein cages of 12- or 24-folded ferritin subunits (4-α-helix polypeptide bundles) self-assemble, experimentally. Ferritin biomineral structures differ among animals and plants or bacteria. The basic ferritin mineral structure is ferrihydrite (Fe2O3·H2O) with either low phosphate in the highly ordered animal ferritin biominerals, Fe/PO4 ∼ 8:1, or Fe/PO4 ∼ 1:1 in the more amorphous ferritin biominerals of plants and bacteria. While different ferritin environments, plant bacterial-like plastid organelles and animal cytoplasm, might explain ferritin biomineral differences, investigation is required. Currently, the physiological significance of plant-specific and animal-specific ferritin iron minerals is unknown.The iron content of ferritin in living tissues ranges from zero in “apofe...

Shedding of adhesion receptors from the surface of activated platelets

Abstract: When platelets are activated, several receptors are removed from the platelet surface. Cytoskeletal reorganizations can cause receptors to redistribute to intracellular membranes. In addition, receptors can be removed from the platelet surface by shedding of the receptor from the cell. Shedding can occur by at least two mechanisms. First, glycoprotein (GP)Ib alpha and GP V are shed from the membrane as a result of the proteolytic cleavage of the extracellular domain of these receptors from the platelet. The protease responsible for this cleavage appears to be a membrane-bound divalent cation-dependent protease other than calpain. Proteolytic cleavage does not occur until secretion is well under way and occurs whether platelets aggregate or not. Soluble forms of both GP Ib alpha and GP V are present in the plasma, where they may serve as feedback inhibitors limiting the development of thrombi. Future studies will be needed to identify the protease(s) responsible for removing the membrane receptors and to determine whether cleavage of the receptors from activated platelets results from activation of the protease(s), exposure of the protease(s), or an altered exposure of the protease-sensitive sites on the receptors. It will be of particular interest to determine whether the protease(s) that cleaves GP Ib alpha and GP V in platelets is the same as the protease(s) that cleaves receptors from the surface of other activated cells. Receptors also are shed from the surface of activated platelets by the generation of microvesicles from the plasma membrane. These microvesicles appear to contain all of the major membrane glycoproteins but are depleted in those that have been removed from the platelet membrane by proteolytic cleavage. The primary mechanism responsible for the shedding of microvesicles from the surface of platelets stirred with physiological agonists involves activation of calpain, which cleaves components of the membrane skeleton and dissociates it from the plasma membrane GP Ib-IX complex. Microvesicles are present in the circulation and increase under conditions in which platelet activation is known to have occurred. Because they contain functional adhesive receptors and procoagulant activity on their surface, they may function to disseminate procoagulant activity and stabilize the formation of platelet clots.