SummaryWnt proteins are secreted post-translationally modified proteins that signal locally to regulate development and proliferation. The production of bioactive Wnts requires a number of dedicated factors in the secreting cell whose coordinated functions are not fully understood. A screen for small molecules identified inhibitors of vacuolar acidification as potent inhibitors of Wnt secretion. Inhibition of the V-ATPase or disruption of vacuolar pH gradients by diverse drugs potently inhibited Wnt/-catenin signaling both in cultured human cells and in vivo, and impaired Wnt-regulated convergent extension movements in Xenopus embryos. WNT secretion requires its binding to the carrier protein wntless (WLS); we find that WLS is ER-resident in human cells and WNT3A binding to WLS requires PORCN-dependent lipid modification of WNT3A at serine 209. Inhibition of vacuolar acidification results in accumulation of the WNT3A-WLS complex both in cells and at the plasma membrane. Modeling predictions suggest that WLS has a lipid-binding -barrel that is similar to the lipocalin-family fold. We propose that WLS binds Wnts in part through a lipid-binding domain, and that vacuolar acidification is required to release palmitoylated WNT3A from WLS in secretory vesicles, possibly to facilitate transfer of WNT3A to a soluble carrier protein.

The fungus Curvularia lunata, isolated from the marine sponge Niphates olemda, yielded the new 1,3,8-trihydroxy-6-methoxyanthraquinone, which we named lunatin (1), the known modified bisanthraquinone cytoskyrin A (2), and the known plant hormone (+)-abscisic acid (3). Both anthraquinones were found to be active against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. Two strains of the fungus Cladosporium herbarum, isolated from the sponges Aplysina aerophoba and Callyspongia aerizusa, respectively, yielded two new alpha-pyrones, herbarin A (4) and herbarin B (5), the known compound citreoviridin A (6), and the new phthalide herbaric acid (7). All structures were unambiguously established by 1D and 2D NMR and MS data.

Bioassay-guided fractionation of organic extracts of Cladosporium herbarum, isolated from the marine sponge Callyspongia aerizusa, yielded two new macrolide metabolites: pandangolide 3 and 4 (1 and 2) and the known fungal metabolites pandangolide 2 (3), cladospolide B (4), and iso-cladospolide B (5). Also isolated were the antimicrobially active (against Bacillus subtilis and Staphylococcus aureus) furan carboxylic acids: Sumiki's acid (6) and its new derivative, acetyl Sumiki's acid (7). All structures were elucidated by spectroscopic methods.

The ethyl acetate extract of Penicillium sp., derived from the Mediterranean sponge Axinella verrucosa, yielded the known compound communesin B (1) and its new congeners communesins C (2) and D (3), as well as the known compounds griseofulvin, dechlorogriseofulvin, and oxaline. All structures were unambiguously established by 1D and 2D NMR and MS data. In several bioassays performed on different leukemia cell lines, the communesins exhibited moderate antiproliferative activity.