Browsing by Author "Gatica, Arnaldo"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Fatty acid composition of Drosophila photoreceptor light-sensitive microvilli
    (2013) Munoz, Yorka; Fuenzalida, Karen; Bronfman, Miguel; Gatica, Arnaldo; Sepulveda, Marcelo; Bacigalupo, Juan; Roth, Alejandro D.; Delgado, Ricardo
    Phototransduction, the mechanism underlying the electrical response to light in photoreceptor cells, has been thoroughly investigated in Drosophila melanogaster, an essential model in signal transduction research. These cells present a highly specialized photosensitive membrane consisting of thousands of microvilli forming a prominent structure termed a rhabdomere. These microvilli encompass the phototransduction proteins, most of which are transmembrane and exclusively rhabdomeric. Rhabdomere membrane lipids play a crucial role in the activation of the transient receptor potential ionic channels (TRP and TRPL) responsible for initiating the photoresponse. Despite its importance, rhabdomere lipid composition has not been established. We developed a novel preparation enriched in rhabdomere membranes to perform a thorough characterization of the lipidomics of Drosophila rhabdomeres. Isolated eyes (500) were homogenized and subjected to a differential centrifugation protocol that generates a fraction enriched in rhabdomere membrane. Lipids extracted from this preparation were identified and quantified by gas chromatography coupled to mass spectrometry. We found an abundance of low sterol esters (C16:0, C18:0), highly abundant and diverse triglycerides, free fatty acids, a moderate variety of mono and diacyglycerols (C:16:0, 18:0, C18:1) and abundant phospholipids (principally C18:2). This preparation opens a new avenue for investigating essential aspects of phototransduction.
  • Thumbnail Image
    Item
    P450 CYP2C epoxygenase and CYP4A ω-hydroxylase mediate ciprofibrate-induced PPARα-dependent peroxisomal proliferation
    (2007) Gatica, Arnaldo; Zanlungo Matsuhiro, Silvana; Bronfman A., Miguel L.
  • Thumbnail Image
    Item
    P450CYP2C epoxygenase and CYP4A omega-hydroxylase mediate ciprofibrate-induced PPAR alpha-dependent peroxisomal proliferation
    (AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2007) Gatica, Arnaldo; Aguilera, Mauricio C.; Contador, David; Loyola, Gloria; Pinto, Claudio O.; Amigo, Ludwig; Tichauer, Juan E.; Zanlungo, Silvana; Bronfman, Miguel
    Peroxisomal proliferators, such as ciprofibrate, are used extensively as effective hypolipidemic drugs. The effects of these compounds on lipid metabolism require ligand binding activation of the peroxisome proliferator-activated receptor (PPAR) alpha subtype of nuclear receptors and involve transcriptional activation of the metabolic pathways involved in lipid oxidative metabolism, transport, and disposition. omega-Hydroxylated-eicosatrienoic acids (HEETs), products of the sequential metabolism of arachidonic acid (AA) by the cytochrome P450 CYP2C epoxygenase and CYP4A omega-hydroxylase gene subfamilies, have been identified as potent and high-affinity ligands of PPAR alpha in vitro and as PPAR alpha activators in transient transfection assays. Using isolated rat hepatocytes in culture, we demonstrate that specific inhibition of either the CYP2C epoxygenase or the CYP4A omega-hydroxylase abrogates ciprofibrate-induced peroxisomal proliferation, whereas inhibition of other eicosanoid-synthesizing pathways had no effect. Conversely, overexpression of the rat liver CYP2C11 epoxygenase leads to spontaneous peroxisomal proliferation, an effect that is reversed by a CYP inhibitor. Based on these results, we propose that HEETs may serve as endogenous PPAR alpha ligands and that the P450 AA monooxygenases participate in ciprofibrate-induced peroxisomal proliferation and the activation of PPAR alpha downstream targets.