Ca2+ influx through CRAC channels activates cytosolic phospholipase A2, leukotriene C4 secretion, and expression of c-fos through ERK-dependent and -independent pathways in mast cells.
Cytosolic phospholipase A2 (cPLA2) is a Ca2+-dependent enzyme that mediates agonist-dependent arachidonic acid release in most cell types. Arachidonic acid can then be metabolized by the 5-lipoxygenase enzyme to generate the proinflammatory signal leukotriene C4 (LTC4). Here we report that Ca2+ entry through store-operated CRAC (Ca2+ release-activated Ca2+) channels activates the extracellular signal-regulated kinases (ERKs), members of the mitogen-activated protein kinase family, within minutes and this is necessary for stimulation of cPLA2. Ca2+ entry activates ERK indirectly, via recruitment of Ca2+-dependent protein kinase C alpha and betaI. Ca2+ influx also promotes translocation of cytosolic 5-lipoxygenase to the nuclear membrane, a key step in the activation of this enzyme. Translocation is dependent on ERK activation. A role for gene activation is shown by the finding that CRAC channel opening results in increased transcription and translation of c-fos. Inhibition of ERK activation failed to prevent c-fos expression. Our results show that CRAC channel activation elicits short-term effects through the co-coordinated regulation of two metabolic pathways (cPLA2 and 5-lipoxygenase), which results in the generation of both intra- and intercellular messengers within minutes, as well as longer term changes involving gene activation. These short-term effects are mediated via ERK, whereas, paradoxically, c-fos expression is not. Ca2+ influx through CRAC channels can therefore activate different signaling pathways at the same time, culminating in a range of temporally diverse responses.
Chang
Wei-Chiao
WC
Department of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
Nelson
Charmaine
C
Parekh
Anant B
AB
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D045744:Cell Line, Tumor; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D016762:Genes, fos; D017997:Leukotriene C4 / Q000378:metabolism*; D008407:Mast Cells / Q000201:enzymology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D051381:Rats
D015220:Calcium Channels; D017997:Leukotriene C4; D048049:Extracellular Signal-Regulated MAP Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium