Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Calcium signaling was observed in murine T cells over time, starting at a precise moment of contact with a layer of fibroblasts expressing a stimulatory major histocompatibility class II-peptide complex. The contact was controlled by a film-thinning apparatus. Intracellular calcium levels were followed with the ratiometric dye, Fura-2. The calcium response was highly synchronized and well fitted by a mathematical model. The model includes three components: a sequence of reactions occurring after T cell receptor (TCR) triggering; InsP3-mediated calcium release from intracellular stores (Meyer and Stryer, Proc. Natl. Acad. Sci. USA 85: 5051-5055, 1988); and slow changes in levels phospholipase C-gammal (PLCgammal) reflecting a decrease in receptor triggering rate. Each component in the model controls a different part of the response-the initial delay, the sharp rise, and the slow decay, respectively. Kinetic parameters determined from curve fitting were the initial delay in calcium signaling defined as the time when [PLCgammal] reached its half of its maximum (76 s), the coefficient characterizing calcium efflux from endoplasmic reticulum (ER) (2.86 microM s(-1), expressed per liter of cell volume), and a rate constant characterizing the diminishing yield of production of PLCgammal (0.00046 s(-1)) by active TCR. Only the parameter representing PLCgammal production varied much from cell to cell.
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PMID:Modeling of early events in T cell signal transduction after controlled T cell activation by peptide major histocompatibility complex. 1140 Jul 19

Understanding the origins of lipid membrane bilayer rearrangement in response to external stimuli is an essential component of cell biology and the bottom-up design of liposomes for biomedical applications. The enzymes phospholipase C and D (PLC and PLD) both cleave the phosphorus-oxygen bonds of phosphate esters in phosphatidylcholine (PC) lipids. The atomic position of this hydrolysis reaction has huge implications for the stability of PC-containing self-assembled structures, such as the cell wall and lipid-based vesicle drug delivery vectors. While PLC converts PC to diacylglycerol (DAG), the interaction of PC with PLD produces phosphatidic acid (PA). Here we present a combination of small-angle scattering data and all-atom molecular dynamics simulations, providing insights into the effects of atomic-scale reorganization on the supramolecular assembly of PC membrane bilayers upon enzyme-mediated incorporation of DAG or PA. We observed that PC liposomes completely disintegrate in the presence of PLC, as conversion of PC to DAG progresses. At lower concentrations, DAG molecules within fluid PC bilayers form hydrogen bonds with backbone carbonyl oxygens in neighboring PC molecules and burrow into the hydrophobic region. This leads initially to membrane thinning followed by a swelling of the lamellar phase with increased DAG. At higher DAG concentrations, localized membrane tension causes a change in lipid phase from lamellar to the hexagonal and micellar cubic phases. Molecular dynamics simulations show that this destabilization is also caused in part by the decreased ability of DAG-containing PC membranes to coordinate sodium ions. Conversely, PLD-treated PC liposomes remain stable up to extremely high conversions to PA. Here, the negatively charged PA headgroup attracts significant amounts of sodium ions from the bulk solution to the membrane surface, leading to a swelling of the coordinated water layer. These findings are a vital step toward a fundamental understanding of the degradation behavior of PC lipid membranes in the presence of these clinically relevant enzymes, and toward the rational design of diagnostic and drug delivery technologies for phospholipase-dysregulation-based diseases.
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PMID:Fate of Liposomes in the Presence of Phospholipase C and D: From Atomic to Supramolecular Lipid Arrangement. 3015 99