title: Phospholipase D regulation and localisation is dependent upon a phosphatidylinositol 4,5-biphosphate-specific PH domain.
abstract: The signalling pathway leading, for example, to actin cytoskeletal reorganisation, secretion or superoxide generation involves phospholipase D (PLD)-catalysed hydrolysis of phosphatidylcholine to generate phosphatidic acid, which appears to mediate the messenger functions of this pathway. Two PLD genes (PLD1 and PLD2) with similar domain structures have been doned and progress has been made in identifying the protein regulators of PLD1 activation, for example Arf and Rho family members. The activities of both PLD isoforms are dependent on phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and our sequence analysis suggested the presence of a pleckstrin homology (PH) domain in PLD1, although its absence has also been daimed. Investigation of the inositide dependence showed that a bis-phosphorylated lipid with a vicinal pair of phosphates was required for PLD1 activity. Furthermore, PLD1 bound specifically and with high affinity to lipid surfaces containing PI(4,5)P2 independently of the substrate phosphatidylcholine, suggesting a key role for the PH domain in PLD function. Importantly, a glutathione-S-transferase (GST) fusion protein comprising GST and the PH domain of PLD1 (GST-PLD1-PH) also bound specifically to supported lipid monolayers containing PI(4,5)P2. Point mutations within the PLD1 PH domain inhibited enzyme activity, whereas deletion of the domain both inhibited enzyme activity and disrupted normal PLD1 localisation. Thus, the functional PH domain regulates PLD by mediating its interaction with polyphosphoinositide-containing membranes; this might also induce a conformational change, thereby regulating catalytic activity.
authors.affiliation: Institute for Cancer Studies, University of Birmingham, UK. m.hodgkin@bham.ac.uk
authors.forename: M N
authors.initials: MN
authors.lastname: Hodgkin
authors.forename: M R
authors.initials: MR
authors.lastname: Masson
authors.forename: D
authors.initials: D
authors.lastname: Powner
authors.forename: K M
authors.initials: KM
authors.lastname: Saqib
authors.forename: C P
authors.initials: CP
authors.lastname: Ponting
authors.forename: M J
authors.initials: MJ
authors.lastname: Wakelam
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002384:Catalysis; D002460:Cell Line; D002522:Chlorocebus aethiops; D016384:Consensus Sequence; D005347:Fibroblasts; D006801:Humans; D006868:Hydrolysis; D008563:Membrane Lipids / Q000378:metabolism; D008969:Molecular Sequence Data; D010713:Phosphatidylcholines / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D010718:Phosphatidylserines / Q000378:metabolism; D010739:Phospholipase D / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000502:physiology*; D020349:Surface Plasmon Resonance
chemical_list: D008563:Membrane Lipids; D010713:Phosphatidylcholines; D019269:Phosphatidylinositol 4,5-Diphosphate; D010718:Phosphatidylserines; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; C105606:phospholipase D2; D010739:Phospholipase D; C106801:phospholipase D1