title: Antimicrobial and immunostimulatory peptide, KLK, induces an increase in cytosolic Ca²(+) concentration by mobilizing Ca²(+) from intracellular stores.
abstract: The cationic antimicrobial immunomodulatory peptide, KLK (KLKL₅KLK), exerts profound membrane interacting properties, impacting on ultrastructure and fluidity. KLK-membrane interactions that lead to these alterations require the ability of the peptide to move into an α-helical conformation. We show that KLK induces an increase of the intracellular Ca²(+) concentration in human T24 cells. The effect of KLK is buffer-sensitive, as it is detected when HBSS buffer is used, but not with PBS. This, together with the lack of effect of the middle leucine-to-proline-substituted peptide derivative [KPK (KLKLLPLLKLK)], indicates that it is the conformational propensity rather than the net positive charge that contributes to the effect of KLK on intracellular Ca²(+) level of T24 cells. We show that, although KLK slightly stimulates Ca²(+) influx into the cell, the bulk increase of Ca²(+) levels is due to KLK-induced depletion of intracellular Ca²(+) stores. Finally, we demonstrate a KLK-induced switch of PS (phosphatidylserine) from the inner to the outer plasma membrane leaflet that contributes to the onset of early apoptotic changes in these cells.
authors.affiliation: Biophysics Institute, Johannes Kepler University Linz, Austria. julian.weghuber@jku.at
authors.forename: Julian
authors.initials: J
authors.lastname: Weghuber
authors.forename: Anna M
authors.initials: AM
authors.lastname: Lipp
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Stadlbauer
authors.forename: Michael C
authors.initials: MC
authors.lastname: Aichinger
authors.forename: Verena
authors.initials: V
authors.lastname: Ruprecht
authors.forename: Alois
authors.initials: A
authors.lastname: Sonnleitner
authors.forename: Gerhard J
authors.initials: GJ
authors.lastname: Schütz
authors.forename: Tamás
authors.initials: T
authors.lastname: Henics
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism*; D006801:Humans; D018613:Microscopy, Confocal; D009842:Oligopeptides / Q000494:pharmacology*; D010718:Phosphatidylserines / Q000378:metabolism
chemical_list: D000276:Adjuvants, Immunologic; D023181:Antimicrobial Cationic Peptides; D009842:Oligopeptides; D010718:Phosphatidylserines; C531381:lysyl-leucyl-lysyl-leucyl-leucyl-leucyl-leucyl-leucyl-lysyl-leucyl-lysine; D002118:Calcium