Richard J. H. Wojcikiewicz

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The type I inositol 1,4,5-trisphosphate (InsP3) receptor can be rapidly depleted from cells during stimulation of phosphoinositide hydrolysis because its degradation is accelerated (Wojcikiewicz, R. J. H., Furuichi, T., Nakade, S., Mikoshiba, K., and Nahorski, S. R. (1994) J. Biol. Chem. 269, 7963-7969). The present study examines the regulatory properties(More)
Rat basophilic leukemia (RBL-2H3) cells predominantly express the type II receptor for inositol 1,4,5-trisphosphate (InsP3), which operates as an InsP3-gated calcium channel. In these cells, cross-linking the high-affinity immunoglobulin E receptor (FcepsilonR1) leads to activation of phospholipase C gamma isoforms via tyrosine kinase- and(More)
The endoplasmic reticulum (ER)-resident enzyme 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase catalyzes the rate-limiting step in sterol production and is the therapeutic target of statins. Understanding HMG-CoA reductase regulation has tremendous implications for atherosclerosis. HMG-CoA reductase levels are regulated in response to sterols both(More)
While cell signaling devotees tend to think of the endoplasmic reticulum (ER) as a Ca(2+) store, those who study protein synthesis tend to see it more as site for protein maturation, or even degradation when proteins do not fold properly. These two worldviews collide when inositol 1,4,5-trisphosphate (IP(3)) receptors are activated, since in addition to(More)
The ability of cAMP-dependent protein kinase (PKA) to phosphorylate type I, II, and III inositol 1,4,5-trisphosphate (InsP3) receptors was examined. The receptors either were immunopurified from cell lines and then phosphorylated with purified PKA or were phosphorylated in intact cells after activating intracellular cAMP formation. The former studies showed(More)
Stimulation of muscarinic receptors expressed in SH-SY5Y human neuroblastoma cells resulted in a complex profile of inositol 1,4,5-trisphosphate (InsP3) accumulation, with a dramatic increase (six- to eightfold) over the first 10 s (the "peak" phase) and subsequently from approximately 60 s onward, maintained at a lower but sustained level (the "plateau"(More)
We describe a finite-element model of mast cell calcium dynamics that incorporates the endoplasmic reticulum's complex geometry. The model is built upon a three-dimensional reconstruction of the endoplasmic reticulum (ER) from an electron tomographic tilt series. Tetrahedral meshes provide volumetric representations of the ER lumen, ER membrane, cytoplasm,(More)
The recently described co-expression of type I, II and III inositol 1,4,5-trisphosphate (InsP3) receptors in the same cell type has raised the issue of whether these proteins exist as homotetramers or heterotetramers. To address this question, InsP3 receptors were immunoprecipitated with specific antibodies and then probed for co-immunoprecipitating(More)
myo-[3H]Inositol-labelled SH-SY5Y cells were permeabilized with electrical discharges. 3H-Inositol phosphate formation in cells shown to be fully permeable was stimulated by the muscarinic agonist carbachol, by guanosine 5'-(gamma-thio)triphosphate [GTP(S)], and by guanosine 5'-(beta gamma-imido)diphosphate (GppNHp). Synergism was observed on coincubation(More)
Previous studies have shown that as rat cerebellar granule cell cultures differentiate in the presence of 25 mM KCl, they "up-regulate" their ability to form inositol phosphates and release Ca2+ from internal stores in response to the activation of phosphoinositidase C-linked muscarinic and metabotropic receptors. Here we show that they simultaneously(More)