Regulation of cell migration and glucose metabolism by ceramide 1-phosphate

Resumo

The main objective of this thesis is to determine ceramide 1-phosphate (C1P) actions that are receptor-mediated and to evaluate their impact in cell signalling and metabolism.Previously, our group demonstrated that C1P promotes macrophage migration. In this thesis we have observed that stimulation of cell migration by C1P requires the interaction of C1P with a putative plasma membrane receptor. However, little is known about the regulation of cell migration by this receptor. We have found that phosphatidic acid (PA) negatively regulates C1P-stimulated cell migration through a mechanism involving the interaction of PA with the C1P receptor, resulting in inhibition of the signalling pathways involved in this action.Cell migration requires high energy levels to be accomplished. A major source of metabolic energy is glucose. In this thesis we demonstrate that C1P potently stimulates glucose uptake and its metabolism to produce ATP.Concerning C1P biosynthesis, the only enzyme so far identified to achieve this task in mammalian cells is ceramide kinase (CERK). This enzyme is highly dependent on Ca2+ ions for activity, but little else is known about the mechanisms involved in its regulation.From the results obtained in this Thesis, the following conclusions can be drawn:1. Phosphatidic acid interacts with C1P and LPA receptors to: a) inhibit macrophage migration through blockade of C1P-stimulated ERK1/2 phosphorylation, b) stimulate myoblast proliferation through activation of the PI3K/Akt and ERK1/2 pathways, respectively.2. C1P stimulates glucose uptake and ATP production in macrophages through a receptor-mediated mechanism involving the GLUT 3 glucose transporter, and stimulation of the PI3K/Akt pathway.3. CERK is activated by ATP and inhibited by the sphingoid bases 1-deoxymethyl-dihydroceramide and 1-deoxy-dihydroceramide thereby controlling the levels of intracellular C1P in macrophages.