ABSTRACT
Mellpaladines A-C (1-3) and dopargimine (4) are dopamine-derived guanidine alkaloids isolated from a specimen of Palauan Didemnidae tunicate as possible modulators of neuronal receptors. In this study, we isolated the dopargimine derivative 1-carboxydopargimine (5), three additional mellpaladines D-F (6-8), and serotodopalgimine (9), along with a dimer of serotonin, 5,5'-dihydroxy-4,4'-bistryptamine (10). The structures of these compounds were determined based on spectrometric and spectroscopic analyses. Compound 4 and its congeners dopargine (11), nordopargimine (15), and 2-(6,7-dimethoxy-3,4-dihydroisoquinolin-1-yl)ethan-1-amine (16) were synthetically prepared for biological evaluations. The biological activities of all isolated compounds were evaluated in comparison with those of 1-4 using a mouse behavioral assay upon intracerebroventricular injection, revealing key functional groups in the dopargimines and mellpaladines for in vivo behavioral toxicity. Interestingly, these alkaloids also emerged during a screen of our marine natural product library aimed at identifying antiviral activities against dengue virus, SARS-CoV-2, and vesicular stomatitis Indiana virus (VSV) pseudotyped with Ebola virus glycoprotein (VSV-ZGP).
Subject(s)
Alkaloids , Dopamine , Urochordata , Animals , Alkaloids/chemistry , Alkaloids/pharmacology , Alkaloids/isolation & purification , Alkaloids/chemical synthesis , Urochordata/chemistry , Mice , Dopamine/chemistry , Dopamine/pharmacology , Molecular Structure , Guanidine/chemistry , Guanidine/pharmacology , Antiviral Agents/pharmacology , Antiviral Agents/chemistry , Antiviral Agents/isolation & purification , Antiviral Agents/chemical synthesis , Guanidines/chemistry , Guanidines/pharmacology , Guanidines/isolation & purification , SARS-CoV-2/drug effects , HumansABSTRACT
N-glycan-mediated activation of the thrombopoietin receptor (MPL) under pathological conditions has been implicated in myeloproliferative neoplasms induced by mutant calreticulin, which forms an endogenous receptor-agonist complex that traffics to the cell surface and constitutively activates the receptor. However, the molecular basis for this mechanism is elusive because oncogenic activation occurs only in the cell-intrinsic complex and is thus cannot be replicated with external agonists. Here, we describe the structure and function of a marine sponge-derived MPL agonist, thrombocorticin (ThC), a homodimerized lectin with calcium-dependent fucose-binding properties. In-depth characterization of lectin-induced activation showed that, similar to oncogenic activation, sugar chain-mediated activation persists due to limited receptor internalization. The strong synergy between ThC and thrombopoietin suggests that ThC catalyzes the formation of receptor dimers on the cell surface. Overall, the existence of sugar-mediated MPL activation, in which the mode of activation is different from the original ligand, suggests that receptor activation is unpredictably diverse in living organisms.
Subject(s)
Porifera , Receptors, Thrombopoietin , Animals , Lectins , Porifera/metabolism , Receptors, Thrombopoietin/metabolism , Sugars , ThrombopoietinABSTRACT
We screened 868 marine extracts in search of hematopoietic molecules resulted in findings of several extracts that proliferated Ba/F3-HuMpl cells but not the cells expressed with other hematopoietic cytokine receptors, EPO and G-CSF. Separation of the most potent extract of a Micronesian sponge Corticium sp., guided by the cell proliferation assay using Ba/F3-HuMpl cells resulted in an isolation of thrombocorticin (ThC), a novel 14â¯kDa protein as an active principal. ThC displayed concentration-dependent proliferation of Ba/F3-HuMpl cells, and had a stronger activity than that of eltrombopag, a small molecule drug used to treat thrombocytopenia. ThC induced phosphorylation of STAT5, suggesting that it activates Jak/STAT pathway as in the case of TPO. These results together indicated that ThC is a specific agonist for c-Mpl, although the size and shape differs largely from TPO. Here we present isolation, characterization and biological activity of ThC.
Subject(s)
Porifera/chemistry , Proteins/pharmacology , Receptors, Thrombopoietin/agonists , Animals , Cell Line , Mice , Proteins/chemistry , Signal Transduction/drug effectsABSTRACT
Among numerous DNA damaging factors, ionizing radiation produces the damage showing very unique structure. Since ionizing radiation passes through a target DNA as a beam, the respective induced lesions locate close together around the track. Such damage aggregation on target DNA called "clustered DNA damage" is thought to be a major cause of the specific and serious effect of ionizing radiation. However, we have less knowledge about the structure of clustered DNA damage, which seems very important in its biological impact. Therefore, we evaluated procedure to analyze the structure of clustered DNA damage induced by ionizing radiation. In the present study, we used polyacrylamide gel electrophoresis to separate oligodeoxyribonucleotide (ODN) substrates containing clustered DNA damage with post-modification with aldehyde reactive probe. The designed procedure well counted the number of abasic site in the model substrate of clustered DNA damage.
