In vitro antiviral effect of meroditerpenes isolated from the Brazilian seaweed Stypopodium zonale (Dictyotales).

The meroditerpenoids atomaric acid (1), epitaondiol (2) and the peroxylactone of 5'a-desmethyl-5'-acetylatomaric acid (3) were isolated from the Brazilian brown alga Stypopodium zonale collected in two localities (Búzios and Marataízes, RJ and ES States). These compounds showed strong anti-HSV-1 activity in vitro but neither of them inhibited the transcriptase reverse enzyme of HIV-1.

The alkaloid 4-methylaaptamine isolated from the sponge Aaptos aaptos impairs Herpes simplex virus type 1 penetration and immediate-early protein synthesis.

We describe in this paper that the alkaloid 4-methylaaptamine, isolated from the marine sponge Aaptos aaptos, inhibited HSV-1 infection. We initially observed that 4-methylaaptamine inhibited HSV-1 replication in Vero cells in a dose-dependent manner with an EC50 value of 2.4 microM. Moreover, the concentration required to inhibit HSV-1 replication was not cytotoxic, since the CC50 value of 4-methylaaptamine was equal to 72 microM. Next, we found that 4-methylaaptamine sustained antiherpetic activity even when added to HSV-1-infected Vero cells at 4 h after infection, suggesting that this compound inhibits initial events during HSV-1 replication. We observed that 4-methylaaptamine impaired HSV-1 penetration without affecting viral adsorption. In addition, the tested compound could inhibit, in an MOI-dependent manner, the expression of an HSV-1 immediate-early protein, ICP27, thus preventing the inhibition of macromolecular synthesis induced by this virus. Our results warrant further investigation on the pharmacokinetics of 4-methylaaptamine and propose that this alkaloid could be considered as a potential compound for HSV-1 therapy.

Characterization of RAB-like4, the first identified RAB-like protein from Trypanosoma cruzi with GTPase activity.

RAB proteins, which belong to the RAS superfamily, regulate exocytic and endocytic pathways of eukaryotic cells, controlling vesicle docking and fusion. Few RAB proteins have been identified in parasites. Molecular markers for cellular compartments are important to studies concerning about the protein traffic in Trypanosoma cruzi, the causal agent of Chagas disease. In this work, we describe the characterization of TcRABL4, the first RAB-like gene identified in T. cruzi (GenBank Accession No.: ), present as a single-copy gene. TcRABL4 contains all five consensus RAB motifs but lacks cysteine residues at the C terminus, which are essential to isoprenylation, an absolute prerequisite for membrane association of these proteins. TcRABL4 is a functional GTPase that is able to bind and hydrolyze GTP, and its gene is transcribed as a single 1.2 kb mRNA in epimastigotes. TcRABL4 appears to be differentially regulated in the three cell forms of the parasite, and the protein is not associated to membranes, unlike other RAB proteins. It is possible that TcRABL4 may be a member of a novel family of small GTPases.

Characterization of a RAB5 homologue in Trypanosoma cruzi.

RAB proteins are small GTPases involved in exocytic and endocytic pathways of eukaryotic cells, controlling vesicle docking and fusion. RABs show a remarkable specificity in subcellular localization, so they can be used as molecular markers for studying protein trafficking in Trypanosoma cruzi, the causal agent of Chagas' disease. RAB5 is a component of early endosomes. It has been identified in kinetoplastids such as Trypanosoma brucei and Leishmania donovani. In this work, we describe the characterization of the complete coding sequence of a RAB5 gene homologue in T. cruzi (TcRAB5, GenBank Accession No. AY730667). It is present as a single copy gene, located at chromosomal bands XIII and XIV. TcRAB5 shares the highest degrees of similarity (71%) and identity (63%) with Trypanosoma brucei rhodesiense RAB5a and contains all five characteristic RAB motifs. TcRAB5 is transcribed as a single 1.5kb mRNA in epimastigotes. Its transcript was also detected in the other two forms of the parasite, metacyclic trypomastigotes and spheromastigotes. The recombinant TcRAB5 protein was able to bind and hydrolyze GTP. The identification of proteins involved in T. cruzi endo- and exocytic pathways may generate cellular compartment markers, an invaluable tool to better understand the vesicular transport in this parasite.