[A simple method for the study of cytosolic content of oligonucleotides in cells]

Cationic lipid-mediated intracellular delivery of antibodies into live cells

The ability to introduce antibodies to live cells opens new insights to a wide range of applications, such as protein intracellular trafficking studies, protein interference studies with blocking antibodies, and live immunolabeling or protein phosphorylation states studies. Apart from single-chain format variable (scFv) antibodies, DNA transfection of eukaryotic cells is rarely used to produce antibodies in situ, mainly due to inappropriate folding of the antibody in the cytoplasm. Thus, the development of dedicated carriers is needed since antibodies, which are large, are unable to cross the plasma membrane by passive transport. As a result, intracellular delivery of antibodies represents a novel approach for cell biologists. For efficient antibody delivery, major hurdles such as crossing the plasma membrane and effective release of the antibody in the cytoplasm need to be overcome. We studied these two crucial steps using a dedicated delivery reagent in live cells and compared the results with immunocytochemistry experiments in fixed cells.

Pores formation on cell membranes by hederacolchiside A1 leads to a rapid release of proteins for cytosolic subproteome analysis

Hederacolchiside A1 was used to progressively permeabilize the membrane of human melanoma MEL-5 cells. Holes formation was followed by Scanning Electron Microscopy and interaction of the saponin with cholesterol and phospholipids by TOF-SIMS. 2D-LC-MS/MS and 2D-SDS-PAGE show that the release of soluble proteins into serum-free culture media increases with time. This can lead to a new rapid and efficient strategy to analyze the cytosolic subproteome and it opens the door to get information from the cytosolic compartment for clinical proteomic studies.

Identification, purification and partial characterization of tissue inhibitor of matrix metalloproteinase-2 in bovine pulmonary artery smooth muscle

Bovine pulmonary artery smooth muscle possesses the tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) as revealed by Western immunoblot study of its cytosol fraction with bovine polyclonal TIMP-2 antibody. This potent polypeptide inhibitor of matrix metalloproteinases (MMPs) was purified to homogeneity from cytosol fraction of bovine pulmonary artery smooth muscle. This inhibitor was purified by ammonium sulfate precipitation followed by gelatin sepharose and lentil lectin sepharose affinity chromatography and continuous elution electrophoresis by Prep Cell Model 491 (Bio-Rad, USA). SDS-PAGE revealed that the inhibitor has an apparent molecular mass of 21 kDa and was confirmed as TIMP-2 by (i) Western immunoblot assay using bovine polyclonal TIMP-2 antibody; and also by (ii) amino terminal amino acid sequence analysis of the purified inhibitor is found to be identical with TIMP-2 obtained from other sources. The purified 21 kDa inhibitor was found to be active against matrix metalloproteinase-2 (MMP-2, 72 kDa gelatinase) and matrix metalloproteinase-9 (MMP-9, 92 kDa gelatinase), the ambient MMPs in the pulmonary artery smooth muscle. The inhibitor was also found to be sensitive to the activated 72 kDa gelatinase-TIMP-2 complex and also active human interstitial collagenase. By contrast, it was found to be insensitive to the serine proteases: trypsin and plasmin. The inhibitor was heat and acid resistant and it had the sensitivity to trypsin degradation and reduction-alkylation. Treatment of the inhibitor with hydrogen peroxide, superoxide generating system (hypoxanthine plus xanthine oxidase) and peroxynitrite inactivated the inhibitor.

Cell binding, uptake and cytosolic partition of HIV anti-gag phosphodiester oligonucleotides 3'-linked to cholesterol derivatives in macrophages

The purpose of this study is to evaluate the cell interactions of a new class of compounds composed of phosphodiester oligonucleotides linked to the cholesterol group at position 3, 7, or 22 of the steroid structure. The resulting conjugates were assessed for their capacity to bind, penetrate and partition in the cytoplasmic compartment of murine macrophages. The results showed that lipophilic conjugates bind to cells much faster (t(1/2) < or = 10 min) than do underivatized oligomers. Oligomers tethered to the cholesterol at positions 3 and 7 (PO-GEM-3-Chol and PO-GEM-7-Chol) interacted more efficiently with cell membranes and were better internalized than oligomers attached to the cholesterol moiety at position 22 (PO-GEM-22-Chol). The cytosolic fraction of internalized oligomers was studied by a digitonin-based membrane permeabilization method. The recovered fraction of oligomers that can freely diffuse from the cytosol was comparable for GEM-91, a phosphorothioate congener, and for PO-GEM-7-Chol (50-60% of the internalized oligomers), while that of PO-GEM-3-Chol was less (30% of the internalized oligomers) indicating a higher membrane affinity of the latter derivative as compared to the other investigated compounds. Membrane binding and cell internalization correlated well with the hydrophobicity of the conjugates as characterized by their partition coefficients in a water-octanol system. Due to their capacity of rapid binding and cytosolic partition in cells, cholesterol-derivatized oligonucleotides at position 3 or 7 of the steroid molecule appeared as good candidates for systemic delivery of anti-HIV antisense compounds.