Inositol trisphosphate

L’inositol trisphosphate, souvent appelé trisphosphoinositol et abrégé , est, avec les diacylglycérols (DAG), un messager secondaire de la transduction de signal et de la signalisation lipidique des cellules vivantes. Alors que le DAG, de nature aliphatique, demeure inclus dans la membrane cellulaire, est soluble et peut diffuser dans les cellules. résulte de l'hydrolyse du phosphatidylinositol-4,5-bisphosphate , un phospholipide de la membrane plasmique, par la phospholipase C (PLC). Il est dissous dans le cytosol et diffuse jusqu'à atteindre des récepteurs de l', sur lesquels il agit pour accroître la concentration intracellulaire en cations Ca2+. Notes et références Catégorie:Inositol Catégorie:Phospholipide Catégorie:Transduction de signaux

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The role of endoplasmic reticulum calcium pumps during cytosolic calcium spiking in pancreatic acinar cells

Carl Petersen

Many cell types show repetitive short lasting cytosolic calcium spikes with long interspike periods when stimulated with submaximal concentrations of agonists linked to the phosphoinositide signaling pathway. In pancreatic acinar cells these spikes have been shown to be evoked by constant levels of inositol trisphosphate through a mechanism of calcium-induced calcium release and do not depend acutely on the presence of external calcium. However, the processes involved in the interspike period have remained unclear. Here we report that the endoplasmic reticulum Ca(2+)-ATPase play a significant role, not only in resequestering calcium after a spike, but also in regulating the long interspike period. Decreasing the activity of the endoplasmic reticulum calcium pumps leads to shorter interspike intervals and thus higher spiking frequencies, while the duration of each spike increases. The endoplasmic reticulum Ca(2+)-ATPases are able to entirely suppress a response that can subsequently be evoked by partial inhibition of the pumps. This suggests that during the interspike period there is a considerable amount of calcium released from intracellular stores, which is rapidly buffered by the endoplasmic reticulum calcium pumps and the cytosolic calcium-binding proteins. A calcium spike will be initiated by calcium-induced calcium release only when the buffering is saturated.

1993

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Receptor-activated cytoplasmic Ca2+ oscillations in pancreatic acinar cells: generation and spreading of Ca2+ signals

Carl Petersen

Receptor-activated cytoplasmic Ca2+ oscillations have been investigated using both single cell microfluorometry and voltage-clamp recording of Ca(2+)-dependent Cl- current in single internally perfused acinar cells. In these cells there is direct experimental evidence showing that the ACh-evoked [Ca2+]i fluctuations are due to an inositol trisphosphate-induced small steady Ca2+ release which in turn evokes repetitive Ca2+ spikes via a caffeine-sensitive Ca(2+)-induced Ca2+ release process. There is indirect evidence suggesting that receptor-activation in addition to generating the Ca2+ releasing messenger, inositol trisphosphate, also produces another regulator involved in the control of Ca2+ signal spreading. Intracellular inositol trisphosphate or Ca2+ infusion produce short duration repetitive spikes confined to the cytoplasmic area close to the plasma membrane, but these signals can be made to progress throughout the cell by addition of caffeine or by receptor activation.

1991

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Local and Global Cytosolic Ca-2+ Oscillations Evoked by Agonists and Inositol Trisphosphate

Carl Petersen

The agonists acetylcholine (ACh) and cholecystokinin (CCK) evoke oscillating cytosolic Ca2+ signals in pancreatic acinar cells. Low agonist concentrations evoke local cytosolic Ca2+ spikes confined to the secretory pole region and intracellular inositol trisphosphate application can mimick this action. These spikes can occur alone, repetitively or precede longer lasting Ca2+ transients that spread throughout the cell. ACh and CCK evoke different Ca2+ signal patterns also influenced by the resting cytosolic Ca2+ concentration ([Ca2+]i). Ca2+ pump-mediated Ca2+ extrusion occurs in a pulsatile manner and is synchronous with the transient elevations of [Ca2+]i.

1993

Chargement

BIO-478: Pharmacology and pharmacokinetics

This course introduces the student to the fudamentals of pharmacology, pharmacokinetics and drug-receptor interactions. It discusses also pharmacogenetics and chronopharmacology, to exemplify the challenges of personalized medicine.

BIO-471: Cancer biology I

The course covers in detail molecular mechanisms of cancer development with emphasis on cell cycle control, genome stability, oncogenes and tumor suppressor genes.

Transduction de signal

La transduction de signal désigne le mécanisme par lequel une cellule répond à l'information qu'elle reçoit, par des agents chimiques ou autres signaux (tension,...). Elle commande une cascade de si

Phospholipase C

vignette|upright=2|Action des différentes classes de phospholipases sur les phospholipides. Les phospholipases sont des enzymes hydrolysant les liaisons esters des phospholipides. Il existe quatre lia

Insuline

vignette|Les deux chaines de l'insuline bovine. En rouge les ponts disulfures. vignette|droite|Modélisation 3D d'une molécule d'insuline. L'insuline (du insula « île ») est une hormone protéique séc