Inhibition of Non Canonical HIV-1 Tat Secretion Through the Cellular Na,K-ATPase Blocks HIV-1 Infection.

Besides its essential role in the activation of HIV-1 gene expression, the viral Tat protein has the unusual property of trafficking in and out of cells. In contrast to Tat internalization, the mechanism involved in extracellular Tat release has so far remained elusive. Here we show that Tat secretion occurs through a Golgi-independent pathway requiring binding of Tat with three short, non-consecutive intracytoplasmic loops at the C-terminus of the cellular Na,K-ATPase pump alpha subunit.

Enhanced caveolae-mediated endocytosis by diagnostic ultrasound in vitro.

The modulation of cellular endothelial permeability is a desirable goal for targeted delivery of labels and therapeutic macromolecules; the underlying mechanisms, however, remains poorly understood. Here, we hypothesize that a higher endothelial permeability may result as an outcome of selective enhancement of caveolar endocytosis by ultrasound (US), in the frequency and intensity range of current clinical diagnostic use. To assess the role of free radicals in this phenomenon, we exposed confluent human endothelial cells to pulsed diagnostic US for 30 min, with a mechanical index (MI) of 0.

Acetylation of HIV-1 integrase by p300 regulates viral integration.

Integration of HIV-1 into the human genome, which is catalyzed by the viral protein integrase (IN), preferentially occurs near transcriptionally active genes. Here we show that p300, a cellular acetyltransferase that regulates chromatin conformation through the acetylation of histones, also acetylates IN and controls its activity. We have found that p300 directly binds IN both in vitro and in the cells, as also specifically demonstrated by fluorescence resonance energy transfer technique analysis.

Novel human-derived cell-penetrating peptides for specific subcellular delivery of therapeutic biomolecules.

Short peptide sequences that are able to transport molecules across the cell membrane have been developed as tools for intracellular delivery of therapeutic molecules. This work describes a novel family of cell-penetrating peptides named Vectocell peptides [also termed DPVs (Diatos peptide vectors)]. These peptides, originating from human heparin binding proteins and/or anti-DNA antibodies, once conjugated to a therapeutic molecule, can deliver the molecule to either the cytoplasm or the nucleus of mammalian cells.

Transcellular protein transduction using the Tat protein of HIV-1.

The Tat protein of HIV-1 is a powerful transactivator of gene expression. By interacting with a structured RNA sequence at the 5' end of the viral mRNA, it promotes the remodeling of chromatin and the recruitment of processive RNA polymerase complexes at the viral promoter. In addition to these transcriptional functions, a short amino acid motif, highly enriched in basic amino acids, promotes the export of the protein from the expressing cells.

Caveolae-mediated internalization of extracellular HIV-1 tat fusion proteins visualized in real time.

The Tat protein from HIV-1, when fused with heterologous proteins or peptides, can traverse cell membranes. This ability has generated great interest due to potential therapeutic applications. However, the relevant cellular pathway and its dynamics have not been elucidated yet.

Cell membrane lipid rafts mediate caveolar endocytosis of HIV-1 Tat fusion proteins.

The transactivator protein of human immunodeficiency virus type 1 Tat has the unique property of mediating the delivery of large protein cargoes into the cells when present in the extracellular milieu. Here we show that Tat fusion proteins are internalized by the cells through a temperature-dependent endocytic pathway that originates from cell membrane lipid rafts and follows caveolar endocytosis. These conclusions are supported by the study of the slow kinetics of the internalization of Tat endosomes, by their resistance to nonionic detergents, the colocalization of internalized Tat with markers of caveolar endocytosis, and the impairment of the internalization process by drugs that disrupt lipid rafts or disturb caveolar trafficking.