Detection of novel intracellular agonist responsive pools of phosphatidylinositol 3,4-bisphosphate using the TAPP1 pleckstrin homology domain in immunoelectron microscopy

Stephen A Watt, Wendy A Kimber, Ian Neil Fleming, Nick R Leslie, C Peter Downes, John M Lucocq

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PtdIns(3,4) P (2), a breakdown product of the lipid second messenger PtdIns(3,4,5) P (3), is a key signalling molecule in pathways controlling various cellular events. Cellular levels of PtdIns(3,4) P (2) are elevated upon agonist stimulation, mediating downstream signalling pathways by recruiting proteins containing specialized lipid-binding modules, such as the pleckstrin homology (PH) domain. A recently identified protein, TAPP1 (tandem-PH-domain-containing protein 1), has been shown to interact in vitro with high affinity and specificity with PtdIns(3,4) P (2) through its C-terminal PH domain. In the present study, we have utilized this PH domain tagged with glutathione S-transferase (GST-TAPP1-PH) as a probe in an on-section immunoelectron microscopy labelling procedure, mapping the subcellular distribution of PtdIns(3,4) P (2). As expected, we found accumulation of PtdIns(3,4) P (2) at the plasma membrane in response to the agonists platelet-derived growth factor and hydrogen peroxide. Importantly, however, we also found agonist stimulated PtdIns(3,4) P (2) labelling of intracellular organelles, including the endoplasmic reticulum and multivesicular endosomes. Expression of the 3-phosphatase PTEN (phosphatase and tensin homologue deleted on chromosome 10) in PTEN-null U87MG cells revealed differential sensitivity of these lipid pools to the enzyme. These data suggest a role for PtdIns(3,4) P (2) in endomembrane function.
Original languageEnglish
Pages (from-to)653-663
Number of pages11
JournalBiochemical Journal
Issue number3
Publication statusPublished - 1 Feb 2004



  • animals
  • blood proteins
  • carrier proteins
  • cell line
  • tumor cell line
  • DNA probes
  • down-regulation
  • endoplasmic reticulum
  • humans
  • hydrogen peroxide
  • intracellular membranes
  • intracellular signaling peptides and proteins
  • intracellular space
  • membrane proteins
  • mice
  • immunoelectron microscopy
  • PTEN phosphohydrolase
  • peptides
  • phosphatidylinositol phosphates
  • phosphoproteins
  • phosphoric monoester hydrolases
  • platelet-derived growth factor
  • tertiary protein structure
  • sequence homology, amino acid
  • staining and labeling
  • swiss 3T3 cells
  • tumor suppressor proteins

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