Antillatoxin is a sodium channel activator that displays unique efficacy in heterologously expressed rNav1.2, rNav1.4 and rNav1.5 alpha subunits

<p>Abstract</p> <p>Background</p> <p>Antillatoxin (ATX) is a structurally unique lipopeptide produced by the marine cyanobacterium <it>Lyngbya majuscula</it>. ATX activates voltage-gated sodium channel α-subunits at an undefined recognition site and stimulates sodium influx in neurons. However, the pharmacological properties and selectivity of ATX on the sodium channel α-subunits were not fully characterized.</p> <p>Results</p> <p>In this study, we characterized the pharmacological properties and selectivity of ATX in cells heterologously expressing rNa_v1.2, rNa_v1.4 or rNa_v1.5 α-subunits by using the Na⁺selective fluorescent dye, sodium-binding benzofuran isophthalate. ATX produced sodium influx in cells expressing each sodium channel α-subunit, whereas two other sodium channel activators, veratridine and brevetoxin-2, were without effect. The ATX potency at rNa_v1.2, rNa_v1.4 and rNa_v1.5 did not differ significantly. Similarly, there were no significant differences in the efficacy for ATX-induced sodium influx between rNa_v1.2, rNa_v1.4 and rNa_v1.5 α-subunits. ATX also produced robust Ca²⁺influx relative to other sodium channel activators in the calcium-permeable DEAA mutant of rNa_v1.4 α-subunit. Finally, we demonstrated that the 8-demethyl-8,9-dihydro-antillatoxin analog was less efficacious and less potent in stimulating sodium influx.</p> <p>Conclusions</p> <p>ATX displayed a unique efficacy with respect to stimulation of sodium influx in cells expressing rNa_v1.2, rNa_v1.4 and rNa_v1.5 α-subunits. The efficacy of ATX was distinctive inasmuch as it was not shared by activators of neurotoxin sites 2 and 5 on VGSC α-subunits. Given the unique pharmacological properties of ATX interaction with sodium channel α-subunits, decoding the molecular determinants and mechanism of action of antillatoxin may provide further insight into sodium channel gating mechanisms.</p

Structure and activity of DmmA, a marine haloalkane dehalogenase

DmmA is a haloalkane dehalogenase (HLD) identified and characterized from the metagenomic DNA of a marine microbial consortium. Dehalogenase activity was detected with 1,3‐dibromopropane as substrate, with steady‐state kinetic parameters typical of HLDs ( K m = 0.24 ± 0.05 mM, k cat = 2.4 ± 0.1 s −1 ). The 2.2‐Å crystal structure of DmmA revealed a fold and active site similar to other HLDs, but with a substantially larger active site binding pocket, suggestive of an ability to act on bulky substrates. This enhanced cavity was shown to accept a range of linear and cyclic substrates, suggesting that DmmA will contribute to the expanding industrial applications of HLDs. PDB Code(s): 3U1TPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90241/1/PRO_2009_sm_suppinfo.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/90241/2/2009_ftp.pd

Laucysteinamide A, a Hybrid PKS/NRPS Metabolite from a Saipan Cyanobacterium, cf. Caldora penicillata

A bioactivity guided study of a cf. Caldora penicillata species, collected during a 2013 expedition to the Pacific island of Saipan, Northern Mariana Islands (a commonwealth of the USA), led to the isolation of a new thiazoline-containing alkaloid, laucysteinamide A (1). Laucysteinamide A is a new monomeric analogue of the marine cyanobacterial metabolite, somocystinamide A (2), a disulfide-bonded dimeric compound that was isolated previously from a Fijian marine cyanobacterium. The structure and absolute configuration of laucysteinamide A (1) was determined by a detailed analysis of its NMR, MS, and CD spectra. In addition, the highly bioactive lipid, curacin D (3), was also found to be present in this cyanobacterial extract. The latter compound was responsible for the potent cytotoxicity of this extract to H-460 human non-small cell lung cancer cells in vitro

A novel uncultured heterotrophic bacterial associate of the cyanobacterium Moorea producens JHB

Background Filamentous tropical marine cyanobacteria such as Moorea producens strain JHB possess a rich community of heterotrophic bacteria on their polysaccharide sheaths; however, these bacterial communities have not yet been adequately studied or characterized. Results and discussion Through efforts to sequence the genome of this cyanobacterial strain, the 5.99 MB genome of an unknown bacterium emerged from the metagenomic information, named here as Mor1. Analysis of its genome revealed that the bacterium is heterotrophic and belongs to the phylum Acidobacteria, subgroup 22; however, it is only 85 % identical to the nearest cultured representative. Comparative genomics further revealed that Mor1 has a large number of genes involved in transcriptional regulation, is completely devoid of transposases, is not able to synthesize the full complement of proteogenic amino acids and appears to lack genes for nitrate uptake. Mor1 was found to be present in lab cultures of M. producens collected from various locations, but not other cyanobacterial species. Diverse efforts failed to culture the bacterium separately from filaments of M. producens JHB. Additionally, a co-culturing experiment between M. producens JHB possessing Mor1 and cultures of other genera of cyanobacteria indicated that the bacterium was not transferable. Conclusion The data presented support a specific relationship between this novel uncultured bacterium and M. producens, however, verification of this proposed relationship cannot be done until the ?uncultured? bacterium can be cultured

Bastimolide B, an Antimalarial 24-Membered Marine Macrolide Possessing a tert-Butyl Group

We reported previously the discovery of the potent antimalarial 40-membered macrolide bastimolide A (1) from the tropical marine cyanobacterium Okeania hirsute. Continued investigation has led to the discovery of a new analogue, bastimolide B (2), a 24-membered polyhydroxy macrolide with a long aliphatic chain and unique terminal tertbutyl group. Its complete structure was determined by a combination of extensive spectroscopic methods and comparative analysis of its methanolysis products with those of bastimolide A. A methanolysis mechanism for bastimolide A is proposed, and one unexpected isomerization product of the C2−C3 double bond, 2-(E)-bastimolide A (3), was obtained. Bastimolide B (2) showed strong antimalarial activity against chloroquine-sensitive Plasmodium falciparum strain HB3. A preliminary investigation of the structure−activity relationship based on six analogues revealed the importance of the double bond as well as the 1,3-diol and 1,3,5-triol functionalities.We reported previously the discovery of the potent antimalarial 40-membered macrolide bastimolide A (1) from the tropical marine cyanobacterium Okeania hirsute. Continued investigation has led to the discovery of a new analogue, bastimolide B (2), a 24-membered polyhydroxy macrolide with a long aliphatic chain and unique terminal tertbutyl group. Its complete structure was determined by a combination of extensive spectroscopic methods and comparative analysis of its methanolysis products with those of bastimolide A. A methanolysis mechanism for bastimolide A is proposed, and one unexpected isomerization product of the C2−C3 double bond, 2-(E)-bastimolide A (3), was obtained. Bastimolide B (2) showed strong antimalarial activity against chloroquine-sensitive Plasmodium falciparum strain HB3. A preliminary investigation of the structure−activity relationship based on six analogues revealed the importance of the double bond as well as the 1,3-diol and 1,3,5-triol functionalities

Alkaloids from the Sponge Stylissa carteri Present Prospective Scaffolds for the Inhibition of Human Immunodeficiency Virus 1 (HIV-1).

The sponge Stylissa carteri is known to produce a number of secondary metabolites displaying anti-fouling, anti-inflammatory, and anti-cancer activity. However, the anti-viral potential of metabolites produced by S. carteri has not been extensively explored. In this study, an S. carteri extract was HPLC fractionated and a cell based assay was used to evaluate the effects of HPLC fractions on parameters of Human Immunodeficiency Virus (HIV-1) infection and cell viability. Candidate HIV-1 inhibitory fractions were then analyzed for the presence of potential HIV-1 inhibitory compounds by mass spectrometry, leading to the identification of three previously characterized compounds, i.e., debromohymenialdisine (DBH), hymenialdisine (HD), and oroidin. Commercially available purified versions of these molecules were re-tested to assess their antiviral potential in greater detail. Specifically, DBH and HD exhibit a 30%-40% inhibition of HIV-1 at 3.1 μM and 13 μM, respectively; however, both exhibited cytotoxicity. Conversely, oroidin displayed a 50% inhibition of viral replication at 50 μM with no associated toxicity. Additional experimentation using a biochemical assay revealed that oroidin inhibited the activity of the HIV-1 Reverse Transcriptase up to 90% at 25 μM. Taken together, the chemical search space was narrowed and previously isolated compounds with an unexplored anti-viral potential were found. Our results support exploration of marine natural products for anti-viral drug discovery

Digitizing mass spectrometry data to explore the chemical diversity and distribution of marine cyanobacteria and algae.

Natural product screening programs have uncovered molecules from diverse natural sources with various biological activities and unique structures. However, much is yet underexplored and additional information is hidden in these exceptional collections. We applied untargeted mass spectrometry approaches to capture the chemical space and dispersal patterns of metabolites from an in-house library of marine cyanobacterial and algal collections. Remarkably, 86% of the metabolomics signals detected were not found in other available datasets of similar nature, supporting the hypothesis that marine cyanobacteria and algae possess distinctive metabolomes. The data were plotted onto a world map representing eight major sampling sites, and revealed potential geographic locations with high chemical diversity. We demonstrate the use of these inventories as a tool to explore the diversity and distribution of natural products. Finally, we utilized this tool to guide the isolation of a new cyclic lipopeptide, yuvalamide A, from a marine cyanobacterium