Deferasirox-TAT(47-57) peptide conjugate as a water soluble, bifunctional iron chelator with potential use in neuromedicine

Deferasirox (DFX), an orally active and clinically approved iron chelator, is being used extensively for the treatment of iron overload. However, its water insolubility makes it cumbersome for practical use. In addition to this, the low efficacy of DFX to remove brain iron prompted us to synthesize and evaluate a DFX-TAT(47-57) peptide conjugate for its iron chelation properties and permeability across RBE4 cell line, an in vitro model of the blood-brain barrier. The water-soluble conjugate was able to remove labile iron from buffered solution as well as from iron overloaded sera, and the permeability of DFX-TAT(47-57) conjugate into RBE4 cells was not affected compared to parent deferasirox. The iron bound conjugate was also able to translocate through the cell membrane.

Synthesis and evaluation of a novel liposome containing BPA-peptide conjugate for BNCT

We aimed at securing sufficient concentrations of (10)B in boron neutron capture therapy (BNCT) by developing a new drug delivery system. We have designed and developed a novel lipid analog and succeeded in using it to develop the new boron component liposome. It consisted of three different kinds of amino acid derivatives and two fatty acids, and could react directly with the peptide synthesized first on resin by Fmoc solid-phase synthesis. In this study, lipid analog conjugated with HIV-TAT peptide (domain of human immunodeficiency virus TAT protein) and boronophenylalanine (BPA) was synthesized and successfully incorporated into liposomes.

Effect of transcription peptide inhibitors on HIV-1 replication

HIV-1 manipulates cellular machineries such as cyclin dependent kinases (cdks) and their cyclin elements, to stimulate virus production and maintain latent infection. Specifically, the HIV-1 viral protein Tat increases viral transcription by binding to the TAR promoter element. This binding event is mediated by the phosphorylation of Pol II by complexes such as cdk9/Cyclin T and cdk2/Cyclin E. Recent studies have shown that a Tat 41/44 peptide derivative prevents the loading of cdk2 onto the HIV-1 promoter, inhibiting gene expression and replication. Here we show that Tat peptide analogs computationally designed to dock at the cyclin binding site of cdk2 have the ability to bind to cdk2 and inhibit the association of cdk2 with the HIV promoter. Specifically, the peptide LAALS dissociated the complex and decreased kinase activity in vitro. We also describe our novel small animal model which utilizes humanized Rag2(-/-)gamma(c)(-/-) mice. This small peptide inhibitor induces a decrease in HIV-1 viral transcription in vitro and minimizes viral loads in vivo.

Effective antibacterial action of tat (47-58) by increased uptake into bacterial cells in the presence of trypsin

In a previous study, we found an antifungal effect on human pathogenic fungi by the cell-penetrating peptide Tat (47-58) derived from HIV-1. Tat (47-58) immediately entered into the fungal nucleus and affected some physiological changes on the intracellular condition. In this study, Tat (47-58) showed a broad spectrum of antibacterial activity against pathogenic bacteria including bacterial clinical isolates. To improve resistance against proteases for use in vivo, we synthesized an analog of Tat (47-58) by substituting the L-amino acid for the D-amino acid. The D-enantiomer of Tat (47-58) also exhibited a broad spectrum of antibacterial activity at almost the same level of L-Tat (47-58) concentration. Unlike L-Tat (47-58), D-Tat (47-58) showed a significant proteolytic resistance against all proteases tested and antimicrobial activities in the presence of trypsin. Moreover, D-Tat (47-58) inhibited MRSA infection in human HeLa cells whereas L-Tat (47-58) partially allowed MRSA infection, and the results were due to the proteolytic resistance of D-Tat (47-58).