Biology subjects

Politi, S.

Publications and source records attributed to Politi, S..

2 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↗

bioRxiv2023

Living Photovoltaics based on Recombinant Expression of MtrA Decaheme in Photosynthetic Bacteria

At the center of microbial bioelectricity applications lies the critical need to express foreign heme proteins that are capable of redirecting the electron flux of the cells metabolism. This study presents bioengineered Synechocystis sp. PCC 6803 cells capable of increased electrogenicity through the introduction of a genetic construct for cytochrome expression. We could demonstrate the functional expression of the periplasmic MtrA decaheme c-type cytochrome from Shewanella oneidensis, a dissimilatory metal-reducing exoelectrogen, inside Synechocystis. Protein expression was verified through western-blotting and immunostaining, and oxygen evolution, optical density, and absorption measurements confirm sustained cell activity and viability under the tested expression conditions. Furthermore, the bioengineered cells show enhanced mediated exoelectrogenicity, as confirmed through a colorimetric iron assay and electrochemical measurements. Compared to wildtype cells on graphite electrodes, the bioengineered cells show a 2-fold increase in light-dependent, extracellular electron transfer, achieving photocurrent densities of 4 A/cm2 under white light illumination of [~]500 mol m-2s-1. The increased capacitance obtained under illumination and suppressed photocurrents in the presence of the photosynthetic inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) suggest increased extraction of photosynthetically derived electrons from the recombinant cells. The improved bioelectricity transport across the outer membranes, as achieved through the heterologous heme expression inside cyanobacteria, presents new opportunities for re-wiring the metabolisms of light-harvesting microbes.

bioengineering↗