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SUMMARY Drosophila phototransduction is a G protein-coupled, calcium-regulated signaling cascade that serves as a model system for the dissection of phospholipase C (PLC) signaling in vivo. The Drosophila light-activated conductance is constituted in part by the transient receptor potential (trp) ion channel, yet trp mutants still display a robust response(More)
Addition of the bioactive phospholipid lysophosphatidic acid (LPA) or a thrombin receptor-activating peptide (TRP) to serum-starved N1E-115 or NG108-15 neuronal cells causes rapid growth cone collapse, neurite retraction, and transient rounding of the cell body. These shape changes appear to be driven by receptor-mediated contraction of the cortical(More)
Heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors are phosphorylated by kinases that mediate agonist-dependent receptor deactivation. Although many receptor kinases have been isolated, the corresponding phosphatases, necessary for restoring the ground state of the receptor, have not been identified. Drosophila RDGC (retinal(More)
Epac1 is a guanine nucleotide exchange factor for Rap1 that is activated by direct binding of cAMP. In vitro studies suggest that cAMP relieves the interaction between the regulatory and catalytic domains of Epac. Here, we monitor Epac1 activation in vivo by using a CFP-Epac-YFP fusion construct. When expressed in mammalian cells, CFP-Epac-YFP shows(More)
Sphingosine-1-phosphate (S1P) is a bioactive lysosphingolipid implicated in mitogenesis and cytoskeletal remodelling, but its mechanism of action is poorly understood. We report here that in N1E-115 neuronal cells, S1P mimics the G protein-coupled receptor agonist lysophosphatidic acid (LPA) in rapidly inducing neurite retraction and soma rounding, a(More)
Lysophosphatidic acid (LPA) is a mitogenic phospholipid produced by certain activated cells and present in serum. LPA stimulates phospholipase C and inhibits adenylate cyclase in its target cells, apparently by activating a specific G-protein-coupled receptor. Here, we demonstrate that LPA causes transient rounding of N1E-115 and NG108-15 neuronal cells(More)
Using a novel approach that detects changes in the conformation of ERalpha, we studied the efficacy of anti-estrogens to inactivate ERalpha under different experimental conditions. We show that phosphorylation of serine-305 in the hinge region of ERalpha by protein kinase A (PKA) induced resistance to tamoxifen. Tamoxifen bound but then failed to induce the(More)
Imaging of fluorescence resonance energy transfer (FRET) between suitable fluorophores is increasingly being used to study cellular processes with high spatiotemporal resolution. The genetically encoded Cyan (CFP) and Yellow (YFP) variants of Green Fluorescent Protein have become the most popular donor and acceptor pair in cell biology. FRET between these(More)
Rac is activated in response to various stimuli including growth factors and by adhesion to the extracellular matrix. However, how these stimuli ultimately result in Rac activation is poorly understood. The increase in intracellular calcium [Ca2+]i represents a ubiquitous second messenger system in cells, linking receptor activation to downstream signaling(More)
Lysophosphatidic acid (LPA) is a water-soluble phospholipid with hormone-like and growth-factor-like activities. LPA activates a putative G-protein-coupled receptor in responsive cells, but the natural source of exogenous LPA is unknown. Here we show that LPA is present in mammalian serum in an active form (bound to albumin) at concentrations of 1-5 microM,(More)