  Insight into the cellular uptake mechanism of a secondary amphipathic cell penetrating peptide for siRNA delivery.; ; et al in Biochemistry (2010) Delivery of siRNA remains a major limitation to their clinical application and several technologies have been proposed to improve their cellular uptake. We recently described a peptide-based nanoparticle ... [more ▼] Delivery of siRNA remains a major limitation to their clinical application and several technologies have been proposed to improve their cellular uptake. We recently described a peptide-based nanoparticle system for efficient delivery of siRNA into primary cell lines: CADY. CADY is a secondary amphipathic peptide that forms stable complexes with siRNA and improves their cellular uptake independently of the endosomal pathway. In the present work, we have combined molecular modelling, spectroscopy and membrane interaction approaches, in order to gain further insight into CADY/siRNA particle mechanism of interaction with biological membrane. We demonstrate that CADY forms stable complexes with siRNA and binds phospholipids tightly, mainly through electrostatic interactions. Binding to siRNA or phospholipids triggers a conformational transition of CADY from an unfolded state to an -helical structure, thereby stabilizing CADY/siRNA complexes and improving their interactions with cell membranes. Therefore, we propose that CADY cellular membrane interaction is driven by its structural polymorphism which enables stabilization of both electrostatic and hydrophobic contacts with surface membrane proteoglycan and phospholipids. [less ▲] Detailed reference viewed: 25 (0 ULg)Membrane topology of the Escherichia coli AmpG permease required for recycling of cell wall anhydromuropeptides and AmpC beta-lactamase induction; ; Brasseur, Robert  et alin Antimicrobial Agents and Chemotherapy (2005), 49(3), 1145-1149 Escherichia coli, and presumably most other gram-negative bacteria, possesses an efficient protein machinery for recycling its peptidoglycan during cell growth. The major recycled peptidoglycan product is ... [more ▼] Escherichia coli, and presumably most other gram-negative bacteria, possesses an efficient protein machinery for recycling its peptidoglycan during cell growth. The major recycled peptidoglycan product is N-acetylglucosamine-1,6-anhydro-N-acetylmuramic acid-tetrapeptide. Its uptake from the periplasm into the cytoplasm is carried out via the AmpG protein, an intrinsic membrane protein. In gram-negative bacteria carrying an ampC beta-lactamase-inducible gene on their chromosomes, the induction mechanism is directly linked to peptidoglycan recycling. After identification of the different putative hydrophobic segments by computing, the AmpG topology was experimentally determined by using beta-lactamase fusion. In the proposed model, AmpG contains 10 transmembrane segments and two large cytoplasmic loops. [less ▲] Detailed reference viewed: 12 (1 ULg) |
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