Platelet Activating Factor Receptors
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Platelet activating factor (PAF) is a potent pro-inflammatory lipid mediator. Its effects are mediated through cell surface G protein-coupled receptors (GPCRs) that are distributed on numerous cells notably on endothelium . An intracrine mode of action for PAF is proposed based on evidence for intracellular PAF binding sites  and retention of newly generated PAF within its producing cells . Separate functions for the intracellular and cell surface receptors are suggested using agents which putatively distinguish them [4, 5]; immediate effects are mediated by cell surface receptors whereas regulation of gene expression are dependent upon intracellular receptors consistent with presence of signaling effectors in nuclei including G proteins, Ca++, kinases and NF-κB [6,6,8]; but intracellular PAF receptors; especially on nuclei, which may explain their presumed involvement in gene regulation  has never been explicitly demonstrated. We speculated that PAF receptors exist at the cell nucleus where they induce major pro-inflammatory gene cyclooxygenase-2 (COX-2) expression.
KeywordsPlatelet Activate Factor Brain Endothelial Cell Mitogen Activate Protein Kinase Cascade Platelet Activate Factor Receptor Activate Protein Kinase Cascade
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