title: First step of the cell-penetrating peptide mechanism involves Rac1 GTPase-dependent actin-network remodelling.
abstract: BACKGROUND
  Application of CPPs (cell-penetrating peptides) constitutes a promising strategy for the intracellular delivery of therapeutic molecules. The non-covalent approach based on the amphipathic peptide MPG has been successfully used to improve the delivery of biologically active macromolecules, both in cellulo and in vivo, through a mechanism independent of the endosomal pathway and mediated by the membrane potential.
  
  
  RESULTS
  In the present study, we have investigated the first step of the cellular uptake mechanism of MPG and shown that both MPG and MPG-cargo complexes interact with the extracellular matrix through the negatively charged heparan sulfate proteoglycans. We demonstrated that initiation of cellular uptake constitutes a highly dynamic mechanism where the binding of MPG or the MPG-cargo to the extracellular matrix is rapidly followed by a remodelling of the actin network associated with the activation of the GTPase Rac1. We suggest that MPG-induced clustering of the glycosaminoglycan platform constitutes the 'onset' of the cellular uptake mechanism, thereby increasing membrane dynamics and membrane fusion processes. This process favours cell entry of MPG or MPG-DNA complexes, which is further controlled by the ability of MPG to induce a local membrane destabilization.
  
  
  CONCLUSIONS
  Although CPPs are taken up through different pathways and mechanisms, the initial step involves electrostatic interactions with the glycosaminoglycan platform, and the dynamics of associated membrane microdomains can be generalized to most non-viral delivery systems.
authors.affiliation: Centre de Recherches de Biochimie Macromoléculaire, Molecular Biophysics and Therapeutics, FRE-2593 CNRS, 1919 Route de Mende, 34293 Montpellier, France.
authors.forename: Sabine
authors.initials: S
authors.lastname: Gerbal-Chaloin
authors.forename: Claire
authors.initials: C
authors.lastname: Gondeau
authors.forename: Gudrun
authors.initials: G
authors.lastname: Aldrian-Herrada
authors.forename: Frédéric
authors.initials: F
authors.lastname: Heitz
authors.forename: Cécile
authors.initials: C
authors.lastname: Gauthier-Rouvière
authors.forename: Gilles
authors.initials: G
authors.lastname: Divita
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D018929:Cell Culture Techniques; D002460:Cell Line; D002999:Clone Cells; D006224:Cricetinae; D003412:Cricetulus; D016895:Culture Media, Serum-Free; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D005109:Extracellular Matrix / Q000378:metabolism; D006025:Glycosaminoglycans / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009479:Neuropeptides / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D010590:Phalloidine; D011554:Pseudopodia / Q000187:drug effects / Q000502:physiology; D012235:Rhodamines; D055672:Static Electricity; D013997:Time Factors; D014162:Transfection; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000199:Actins; D016895:Culture Media, Serum-Free; D004268:DNA-Binding Proteins; D006025:Glycosaminoglycans; C475074:MPG peptide; D009479:Neuropeptides; D010455:Peptides; C107953:RAC1 protein, human; C484602:Rac1 protein, mouse; D012235:Rhodamines; D010590:Phalloidine; D006820:Hyaluronic Acid; D004247:DNA; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein