Complex transcriptional and translational regulation of iPLA resulting in multiple gene products containing dual competing sites for mitochondrial or peroxisomal localization

David J. Mancuso, Christopher M. Jenkins, Harold F. Sims, Joshua M. Cohen, Jingyue Yang, Richard W. Gross

Research output: Contribution to journalArticlepeer-review

58 Scopus citations

Abstract

Membrane-associated calcium-independent phospholipase Aγ7 (iPLA) contains four potential in-frame methionine start sites (Mancuso, D.J. Jenkins, C.M. & Gross, R.W. (2000) J. Biol. Chem. 275, 9937-9945), but the mechanisms regulating the types, amount and subcellular localization of iPLA in cells are incompletely understood. We now: (a) demonstrate the dramatic transcriptional repression of mRNA synthesis encoding iPLA by a nucleotide sequence nested in the coding sequence itself; (b) localize the site of transcriptional repression to the most 5′ sequence encoding the iPLA holoprotein; (c) identify the presence of nuclear protein constituents which bind to the repressor region by gel shift analysis; (d) demonstrate the translational regulation of distinct iPLA isoforms; (e) identify multiple novel exons, promoters, and alternative splice variants of human iPLA ; (f) document the presence of dual-competing subcellular localization signals in discrete isoforms of iPLA; and (g) demonstrate the functional integrity of an N-terminal mitochondrial localization signal by fluorescence imaging and the presence of iPLA in the mitochondrial compartment of rat myocardium. The intricacy of the regulatory mechanisms of iPLA biosynthesis in rat myocardium is underscored by the identification of seven distinct protein products that utilize multiple mechanisms (transcription, translation and proteolysis) to produce discrete iPLA polypeptides containing either single or dual subcellular localization signals. This unanticipated complex interplay between peroxisomes and mitochondria mediated by competition for uptake of the nascent iPLA polypeptide identifies a new level of phospholipase-mediated metabolic regulation. Because uncoupling protein function is regulated by free fatty acids in mitochondria, these results suggest that iPLA processing contributes to integrating respiration and thermogenesis in mitochondria.

Original languageEnglish
Pages (from-to)4709-4724
Number of pages16
JournalEuropean Journal of Biochemistry
Volume271
Issue number23-24
DOIs
StatePublished - Dec 2004

Keywords

  • Mitochondria
  • Peroxisomes
  • Phospholipase
  • Transcription
  • Translation

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