Biology subjects

Amillis, S.

Publications and source records attributed to Amillis, S..

6 recordsLinked to original sources

bioRxiv2025

VapA/Scs2 sustains polarized growth in Aspergillus nidulans by maintaining AP-2-mediated apical endocytosis

Growth of filamentous fungi is highly polarized requiring the coordinated apical delivery of cell wall components and plasma membrane (PM) material, primarily lipids and proteins, to hyphal tips via conventional vesicular secretion. Fungal growth also requires the tight coordination of exocytosis (secretion) with endocytosis and recycling of proteins and lipids, which occurs in a defined region behind the growing tip known as the endocytic collar. Here, we genetically characterized proteins tentatively implicated in the formation of endoplasmic reticulum-plasma membrane (ER-PM) contact sites, including Scs2/VAP, tricalbins and Ist2 homologues, in Aspergillus nidulans. We showed that among these proteins, only the single Scs2/VapA homologue is essential for normal fungal growth, and this requirement is due to the critical role of VapA in maintaining the polarized localization of apical cargoes, such as the lipid flippases DnfA and DnfB or the SNARE protein SynA. In {Delta}vapA mutants, these cargoes lose their polarized localization, a phenotype that correlates with the mislocalization of the AP-2 cargo adaptor complex, which is essential for the endocytosis and recycling of apical membrane components. Further analysis provides evidence linking the defect in apical cargo endocytosis observed in {Delta}vapA mutants to altered membrane lipid partitioning, suggesting that VapA contributes to lipid domain organization critical for cargo recycling. Strikingly, deletion of VapA does not impair the localization or endocytosis of non-polarized (subapical) plasma membrane transporters, indicating that the trafficking and biogenesis of polarized (apical) versus non-polarized (subapical) cargoes are differentially dependent on membrane lipid composition and domain-specific organization.

cell biology↗

bioRxiv2022

The interplay between sulfur assimilation and biodesulfurization phenotype in Rhodococcus qingshengii IGTS8: Insights into a regulatory role of the reverse transsulfuration pathway

Biodesulfurization (BDS) is a process that selectively removes sulfur from dibenzothiophene and its derivatives. Several mesophilic natural biocatalysts have been isolated, harboring the highly conserved desulfurization operon dszABC. Even though the desulfurization phenotype is known to be significantly repressed by methionine, cysteine, and inorganic sulfate, the available information on the metabolic regulation of gene expression is still limited. In this study, scarless knockouts of the sulfur metabolism-related cbs and metB genes are constructed in the desulfurizing strain Rhodococcus sp. IGTS8. We provide sequence analyses for both enzymes of the reverse transsulfuration pathway and report their involvement in the sulfate- and methionine-dependent repression of the biodesulfurization phenotype, based on desulfurization assays in the presence of different sulfur sources. Additionally, the positive effect of cbs and metB gene deletions on dsz gene expression in the presence of both sulfate and methionine, but not cysteine, is uncovered and highlighted.

microbiology↗

bioRxiv2022

The interplay between sulfur metabolism and desulfurization profile in Rhodococcus: Unraveling the role of the transsulfuration pathway

Biodesulfurization (BDS) is a process that selectively removes sulfur from dibenzothiophene and its derivatives. Several natural biocatalysts have been isolated, all harboring the highly conserved desulfurization operon dszABC. Even though the desulfurization phenotype is known to be significantly repressed by methionine, cysteine, and inorganic sulfate, the available information on the metabolic regulation of gene expression is still limited. In this study, scarless knockouts of the sulfur metabolism-related cbs and metB genes are constructed in the desulfurizing strain Rhodococcus sp. IGTS8. We provide sequence analyses for both enzymes of the reverse transsulfuration pathway and report their involvement in the sulfate- and methionine-dependent repression of the biodesulfurization phenotype, based on desulfurization assays in the presence of different sulfur sources. Additionally, the positive effect of cbs and metB gene deletions on dsz gene expression in the presence of both sulfate and methionine, but not cysteine, is uncovered and highlighted.

microbiology↗

bioRxiv2019

Nutrient transporter translocation to the plasma membrane via a Golgi-independent unconventional route

Nutrient transporters are believed to traffic from their site of synthesis, the ER, to the plasma membrane, through the Golgi, using the conventional vesicular trafficking pathway. However, here we report that the UapA purine transporter in Aspergillus nidulans, follows a Golgi-independent, unconventional new route, which does not involve key Rab GTPases, AP adaptors, microtubules or endosomes, but is dependent on functional COPII, clathrin heavy chain (ClaH) and actin. The role of ClaH in transporter secretion is shown to be unrelated to that performing, together with Rab11/AP-1, at the Golgi, and is seemingly due to an effect in actin network functioning. Our findings are discussed within the frame of a model that rationalizes why the trafficking mechanism uncovered herein might hold true for transporters in higher organisms. One Sentence SummaryFungal transporters use a non-polar, COPII- and actin-dependent, route for subcellular traffic to the cell membrane.

cell biology↗

bioRxiv2018

The AP-1 complex is essential for fungal growth via its role in secretory vesicle polar sorting, endosomal recycling and cytoskeleton organization

The AP-1 complex is essential for membrane protein traffic via its role in the pinching-off and sorting of secretory vesicles from the trans-Golgi and/or endosomes. While its essentiality is undisputed in metazoa, its role in model simpler eukaryotes seems less clear. Here we dissect the role of AP-1 in the filamentous fungus Aspergillus nidulans and show that it is absolutely essential for growth due to its role in clathrin-dependent maintenance of polar traffic of specific membrane cargoes towards the apex of growing hyphae. We provide evidence that AP-1 is involved in both anterograde sorting of RabERab11-labeled secretory vesicles and RabA/BRab5- dependent endosome recycling. Additionally, AP-1 is shown to be critical for microtubule and septin organization, further rationalizing its essentiality in cells that face the challenge of cytoskeleton-dependent polarized cargo traffic. This work also opens a novel issue on how non-polar cargoes, such as transporters, are sorted to the eukaryotic plasma membrane.

cell biology↗

bioRxiv2017

Structural lipids enable the formation of functional oligomers of the eukaryotic purine symporter UapA

The role of membrane lipids in modulating eukaryotic transporter structure and function remains poorly understood. We used native mass spectrometry in combination with molecular dynamics simulations and in vivo analyses to investigate the roles of membrane lipids in the structure and transport activity of the purine transporter, UapA, from Aspergillus nidulans. We revealed that UapA exists mainly as a dimer and that two lipid molecules bind per UapA dimer. We identified three classes of phospholipids: phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) which co-purified with UapA. Delipidation of UapA caused dissociation of the dimer into individual protomers. Subsequent addition of PI or PE rescued the UapA dimer and allowed recovery of bound lipids, suggesting a central role of these lipids in stabilising the dimer. We predicted a putative lipid-binding site near the UapA dimer interface. Mutational analyses established that lipid binding at this site is essential for formation of functional UapA dimers. Our findings reveal unprecedented level of detail into the nature of UapA-lipid interactions and provide a framework for studying similar eukaryotic systems.

biophysics↗