Class IV Lasso Peptides Synergistically Induce Proliferation of Cancer Cells and Sensitize Them to Doxorubicin.

Heterologous expression of a biosynthesis gene cluster from Amycolatopsis sp. resulted in the discovery of two unique class IV lasso peptides, felipeptins A1 and A2. A mixture of felipeptins stimulated proliferation of cancer cells, while having no such effect on the normal cells. Detailed investigation revealed, that pre-treatment of cancer cells with a mixture of felipeptins resulted in downregulation of the tumor suppressor Rb, making the cancer cells to proliferate faster. Pre-treatment with felipeptins made cancer cells considerably more sensitive to the anticancer agent doxorubicin and re-sensitized doxorubicin-resistant cells to this drug. Structural characterization and binding experiments showed an interaction between felipeptins resulting in complex formation, which explains their synergistic effect. This discovery may open an alternative avenue in cancer treatment, helping to eliminate quiescent cells that often lead to cancer relapse.

Streptomyces spp. From the Marine Sponge Antho dichotoma: Analyses of Secondary Metabolite Biosynthesis Gene Clusters and Some of Their Products.

Actinomycete bacteria from marine environments represent a potential source for new antibiotics and anti-tumor drugs. Ten strains belonging to the genus Streptomyces isolated from the marine sponge Antho dichotoma collected at the bottom of the Trondheim fjord (Norway) were screened for antibiotic activity. Since only few isolates proved to be bioactive in the conditions tested, we decided to gain an insight into their biosynthetic potential using genome sequencing and analysis. Draft genomes were analyzed for the presence of secondary metabolite biosynthesis gene clusters (BGCs) using antiSMASH software. BGCs specifying both known and potentially novel secondary metabolites were identified, suggesting that these isolates might be sources for new bioactive compounds. The results of this analysis also implied horizontal transfer of several gene clusters between the studied isolates, which was especially evident for the lantibiotic- and thiopeptide-encoding BGCs. The latter implies the significance of particular secondary metabolites for the adaptation of Streptomyces to the spatially enclosed marine environments such as marine sponges. Two bioactive isolates, one showing activity against both yeast and Bacillus subtilis, and one only against yeast were analyzed in details, leading to the identification of cycloheximide, linearmycins, and echinomycins that are presumably responsible for the observed bioactivities.

Cloning and sequencing of three-finger toxins from the venom glands of four Micrurus species from Mexico and heterologous expression of an alpha-neurotoxin from Micrurus diastema.

The three-finger toxins (3FTxs) represent an extremely diverse protein family in elapid venoms, where the short chain α-neurotoxins are the most relevant toxin group from the clinical point of view. Essentially, the 3FTxs variability and the low proportions of α-neurotoxins in the venoms of North American coral snakes make it difficult to obtain effective elapid antivenoms against the envenomation symptoms caused mainly by these α-neurotoxins. In this work, thirty 3FTx transcript sequences were obtained from the venom glands of four coral snake species from Mexico (M. diastema, M. laticollaris, M. browni and M. tener). The transcripts were mined using a forward oligonucleotide based on the highly conserved signal peptide from the 3FTxs, and four of these transcripts, named MlatA1, B.D, B.E and D.H, encoded for short-chain α-neurotoxins. Additionally, one isoform of the D.H α-neurotoxin transcript was identified in the venom of M. diastema. The mature α-neurotoxin coded in the D.H transcript was heterologously expressed, and it was found soluble (4.2 mg/l) in the cytoplasm of a bacterial system. The recombinant D.H (rD.H) had an IC50 value of 31.5 ±â€¯4.4 nM on nicotinic acetylcholine receptors of the muscular type expressed in rhabdomyosarcoma cells (TE671). The rDH also had an LD50 of 0.15 mg/kg mice, and it was evaluated as a potential immunogen in New Zealand rabbits. The protective capacity of rabbit sera was tested against two native coral snake α-neurotoxins, and against rD.H. One of the anti-rD.H rabbit sera was able to neutralize the lethality of all three neurotoxins when tested in groups of CD1 mice. This work contributes to the increasing understanding of the high diversity of 3FTxs, and shows that recombinant coral snake α-neurotoxins are promising supplements for hyperimmunization protocols for coral snake antivenom production.