Actin depolymerizing effect of trisoxazole-containing macrolides

Synthesis and characterization of semisynthetic analogs of the antifungal occidiofungin

Occidiofungin is a broad-spectrum antifungal compound produced by Burkholderia contaminans MS14. It is a cyclic glycol-lipopeptide with a novel beta-amino acid (NAA2) containing a hydroxylated C18 fatty acid chain with a xylose sugar. This study reports a strategy to produce semisynthetic analogs of occidiofungin to further explore the structure activity relationships of this class of compounds. Oxidative cleavage of the diol present on carbons five C(5) and six C(6) removes the xylose and twelve carbons of the fatty acid chain. The resulting cyclic peptide product, occidiofungin aldehyde, is devoid of antifungal activity. However, the free aldehyde group on this product can be subjected to reductive amination reactions to provide interesting semisynthetic analogs. This chemistry allows the quick generation of analogs to study the structure activity relationships of this class of compounds. Despite restoring the length of the aliphatic side chain by reductive amination addition with undecylamine or dodecylamine to the free aldehyde group, the obtained analogs did not demonstrate any antifungal activity. The antifungal activity was partially restored by the addition of a DL-dihydrosphingosine. The dodecylamine analog was demonstrated to still bind to the cellular target actin, suggesting that the diol on the side chain of native occidiofungin is important for entry into the cell enabling access to cellular target F-actin. These results show that the alkyl side chain on NAA2 along with the diol present on this side chain is important for occidiofungin's antifungal activity.

Metabolites from Marine Sponges and Their Potential to Treat Malarial Protozoan Parasites Infection: A Systematic Review

Malaria is an infectious disease caused by protozoan parasites of the Plasmodium genus through the bite of female Anopheles mosquitoes, affecting 228 million people and causing 415 thousand deaths in 2018. Artemisinin-based combination therapies (ACTs) are the most recommended treatment for malaria; however, the emergence of multidrug resistance has unfortunately limited their effects and challenged the field. In this context, the ocean and its rich biodiversity have emerged as a very promising resource of bioactive compounds and secondary metabolites from different marine organisms. This systematic review of the literature focuses on the advances achieved in the search for new antimalarials from marine sponges, which are ancient organisms that developed defense mechanisms in a hostile environment. The principal inclusion criterion for analysis was articles with compounds with IC50 below 10 µM or 10 µg/mL against P. falciparum culture. The secondary metabolites identified include alkaloids, terpenoids, polyketides endoperoxides and glycosphingolipids. The structural features of active compounds selected in this review may be an interesting scaffold to inspire synthetic development of new antimalarials for selectively targeting parasite cell metabolism.

Marine compounds targeting the PI3K/Akt signaling pathway in cancer therapy

Cancer is a disease characterized by overproliferation, including that due to transformation, apoptosis disorders, proliferation, invasion, angiogenesis and metastasis, and is one of the deadliest diseases. Currently, conservative chemotherapy is used for cancer treatment due to a lack of effective drugs. The PI3K/Akt signaling pathway plays a very essential role in the pathogenesis of many cancers, and abnormal activation of this pathway leads to abnormal expression of a series of downstream proteins, which ultimately results in the excessive proliferation of cancer cells. Therefore, the PI3K/Akt signaling pathway is a critical target in cancer treatment. Marine drugs have attracted much attention in recent years, and studies have found that many extracts from oceanic animals, plants and microorganisms or their metabolites exert antitumor effects, including antiproliferative effects or the induction of cell cycle arrest, apoptosis or autophagy. However, most anticancer targets and the mechanisms of marine compounds remain unclear. The great potential of the development of marine drugs provides a new direction for cancer treatment. This review focuses on marine compounds that target the PI3K/Akt signaling pathway for the prevention and treatment of cancer and provides comprehensive information for those interested in research on marine drugs.

Marine Macrolides with Antibacterial and/or Antifungal Activity

Currently, the increasing resistance of microorganisms to antibiotics is a serious problem. Marine organisms are the source of thousands of substances, which also have antibacterial and antifungal effects. Among them, marine macrolides are significant. In this review, the antibacterial and/or antifungal activities of 34 groups of marine macrolides are presented. Exemplary groups are chalcomycins, curvulides, halichondramides, lobophorins, macrolactins, modiolides, scytophycins, spongistatins, or zearalanones. In the paper, 74 antibiotics or their analog sets, among which 29 with antifungal activity, 25 that are antibacterial, and 20 that are both antifungal and antibacterial are summarized. Also, 36 macrolides or their sets are produced by bacteria, 18 by fungi, ten by sponges, seven by algae, two by porifera, and one by nudibranch. Moreover, the chemical structures of representatives from each of the 34 groups of these antibiotics are presented. To summarize, marine organisms are rich in natural macrolides. Some of these may be used in the future in the treatment of bacterial and fungal infections. Marine macrolides can also be potential drugs applicable against pathogens resistant to currently known antibiotics.

A Novel Actin Binding Drug with In Vivo Efficacy

Occidiofungin is produced by the soil bacterium Burkolderia contaminans MS14 and is structurally similar or identical to the burkholdines, xylocandins, and cepacidines. This study identified the primary cellular target of occidiofungin, which was determined to be actin.

Occidiofungin is produced by the soil bacterium Burkolderia contaminans MS14 and is structurally similar or identical to the burkholdines, xylocandins, and cepacidines. This study identified the primary cellular target of occidiofungin, which was determined to be actin. The modification of occidiofungin with a functional alkyne group enabled affinity purification assays and localization studies in yeast. Occidiofungin has a subtle effect on actin dynamics that triggers apoptotic cell death. We demonstrate the highly specific localization of occidiofungin to cellular regions rich in actin in yeast and the binding of occidiofungin to purified actin in vitro. Furthermore, a disruption of actin-mediated cellular processes, such as endocytosis, nuclear segregation, and hyphal formation, was observed. All of these processes require the formation of stable actin cables, which are disrupted following the addition of a subinhibitory concentration of occidiofungin. We were also able to demonstrate the effectiveness of occidiofungin in treating a vulvovaginal yeast infection in a murine model. The results of this study are important for the development of an efficacious novel class of actin binding drugs that may fill the existing gap in treatment options for fungal infections or different types of cancer.

Phospholipase Cη2 Activation Redirects Vesicle Trafficking by Regulating F-actin

PI(4,5)P2 localizes to sites of dense core vesicle exocytosis in neuroendocrine cells and is required for Ca(2+)-triggered vesicle exocytosis, but the impact of local PI(4,5)P2 hydrolysis on exocytosis is poorly understood. Previously, we reported that Ca(2+)-dependent activation of phospholipase Cη2 (PLCη2) catalyzes PI(4,5)P2 hydrolysis, which affected vesicle exocytosis by regulating the activities of the lipid-dependent priming factors CAPS (also known as CADPS) and ubiquitous Munc13-2 in PC12 cells. Here we describe an additional role for PLCη2 in vesicle exocytosis as a Ca(2+)-dependent regulator of the actin cytoskeleton. Depolarization of neuroendocrine PC12 cells with 56 or 95 mm KCl buffers increased peak Ca(2+) levels to ~400 or ~800 nm, respectively, but elicited similar numbers of vesicle exocytic events. However, 56 mm K(+) preferentially elicited the exocytosis of plasma membrane-resident vesicles, whereas 95 mm K(+) preferentially elicited the exocytosis of cytoplasmic vesicles arriving during stimulation. Depolarization with 95 mm K(+) but not with 56 mm K(+) activated PLCη2 to catalyze PI(4,5)P2 hydrolysis. The decrease in PI(4,5)P2 promoted F-actin disassembly, which increased exocytosis of newly arriving vesicles. Consistent with its role as a Ca(2+)-dependent regulator of the cortical actin cytoskeleton, PLCη2 localized with F-actin filaments. The results highlight the importance of PI(4,5)P2 for coordinating cytoskeletal dynamics with vesicle exocytosis and reveal a new role for PLCη2 as a Ca(2+)-dependent regulator of F-actin dynamics and vesicle trafficking.