title: A modified Tat peptide for selective intracellular delivery of macromolecules.
abstract: OBJECTIVE
  The Tat peptide has been widely used for the intracellular delivery of macromolecules. The aim of this study was to modify the peptide to enable regulation of cellular uptake through a dependency on activation by proteases present in the local environment.
  
  
  METHODS
  The native Tat peptide sequence was altered to inhibit the initial interaction of the peptide with the cell membrane through the addition of the consensus sequence for urokinase plasminogen activator (uPA). uPA expression was characterised and semi-quantitatively rated in three cell lines (U251mg, MDA-MB-231 and HeLa). The modified peptide was incubated with both recombinant enzyme and with cells varying in uPA activity. Cellular uptake of the modified Tat peptide line was compared with that of the native peptide and rated according to uPA activity measured in each cell line.
  
  
  RESULTS
  uPA activity was observed to be high in U251mg and MDA-MB-231 and low in HeLa. In MDA-MB-231 and HeLa, uptake of the modified peptide correlated with the level of uPA expression detected (93 and 52%, respectively). In U251mg, however, the uptake of the modified peptide was much less (19% observed reduction) than the native peptide despite a high level of uPA activity detected.
  
  
  CONCLUSIONS
  Proteolytic activation represents an interesting strategy for the targeted delivery of macromolecules using peptide-based carriers and holds significant potential for further exploitation.
authors.affiliation: School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast, UK.
authors.forename: Diarmaid J
authors.initials: DJ
authors.lastname: Murphy
authors.forename: Brian
authors.initials: B
authors.lastname: Walker
authors.forename: Brett
authors.initials: B
authors.lastname: Greer
authors.forename: Patrick
authors.initials: P
authors.lastname: Harriott
authors.forename: S Lorraine
authors.initials: SL
authors.lastname: Martin
mesh_terms: D000595:Amino Acid Sequence; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D016384:Consensus Sequence; D004337:Drug Carriers / Q000138:chemical synthesis*; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D010446:Peptide Fragments / Q000138:chemical synthesis*; D011355:Prodrugs / Q000138:chemical synthesis*; D011994:Recombinant Proteins; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000138:chemical synthesis*
chemical_list: D004337:Drug Carriers; D010446:Peptide Fragments; D011355:Prodrugs; D011994:Recombinant Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D014568:Urokinase-Type Plasminogen Activator