title: The membrane repair response masks membrane disturbances caused by cell-penetrating peptide uptake.
abstract: Although cell-penetrating peptides are able to deliver cargo into cells, their uptake mechanism is still not fully understood and needs to be elucidated to improve their delivery efficiency. Herein, we present evidence of a new mechanism involved in uptake, the membrane repair response. Recent studies have suggested that there might be a direct penetration of peptides in parallel with different forms of endocytosis. The direct penetration of hydrophilic peptides through the hydrophobic plasma membrane, however, is highly controversial. Three proteins involved in target cell apoptosis--perforin, granulysin, and granzymes--share many features common in uptake of cell-penetrating peptides (e.g., they bind proteoglycans). During perforin uptake, the protein activates the membrane repair response, a resealing mechanism triggered in cells with injured plasma membrane, because of extracellular calcium influx. On activation of the membrane repair response, internal vesicles are mobilized to the site of the disrupted plasma membrane, resealing it within seconds. In this study, we have used flow cytometry, fluorescence, and electron microscopy, together with high-performance liquid chromatography and mass spectrometry, to present evidence that the membrane repair response is able to mask damages caused during cell-penetrating peptide uptake, thus preventing leakage of endogenous molecules out of the cell.
authors.affiliation: Department of Neurochemistry, Stockholm University, S-106 91 Stockholm, Sweden.
authors.forename: Caroline
authors.initials: C
authors.lastname: Palm-Apergi
authors.forename: Annely
authors.initials: A
authors.lastname: Lorents
authors.forename: Kärt
authors.initials: K
authors.lastname: Padari
authors.forename: Margus
authors.initials: M
authors.lastname: Pooga
authors.forename: Mattias
authors.initials: M
authors.lastname: Hällbrink
mesh_terms: D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism; D023181:Antimicrobial Cationic Peptides / Q000378:metabolism; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D057846:Cell-Penetrating Peptides; D006224:Cricetinae; D003412:Cricetulus; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D053804:Granzymes / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D010455:Peptides / Q000378:metabolism*; D054353:Perforin / Q000378:metabolism
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D023181:Antimicrobial Cationic Peptides; D002352:Carrier Proteins; D057846:Cell-Penetrating Peptides; D003470:Culture Media; D010455:Peptides; D054353:Perforin; C414409:penetratin; D053804:Granzymes; D002118:Calcium