The last two transmembrane helices in the APC-type FurE transporter act as an intramolecular chaperone essential for concentrative ER-exit.

FurE is a H+ symporter specific for the cellular uptake of uric acid, allantoin, uracil, and toxic nucleobase analogues in the fungus Aspergillus nidulans. Being member of the NCS1 protein family, FurE is structurally related to the APC-superfamily of transporters. APC-type transporters are characterised by a 5+5 inverted repeat fold made of ten transmembrane segments (TMS1-10) and function through the rocking-bundle mechanism. Most APC-type transporters possess two extra C-terminal TMS segments (TMS11-12), the function of which remains elusive. Here we present a systematic mutational analysis of TMS11-12 of FurE and show that two specific aromatic residues in TMS12, Trp473 and Tyr484, are essential for ER-exit and trafficking to the plasma membrane (PM). Molecular modeling shows that Trp473 and Tyr484 might be essential through dynamic interactions with residues in TMS2 (Leu91), TMS3 (Phe111), TMS10 (Val404, Asp406) and other aromatic residues in TMS12. Genetic analysis confirms the essential role of Phe111, Asp406 and TMS12 aromatic residues in FurE ER-exit. We further show that co-expression of FurE-Y484F or FurE-W473A with wild-type FurE leads to a dominant negative phenotype, compatible with the concept that FurE molecules oligomerize or partition in specific microdomains to achieve concentrative ER-exit and traffic to the PM. Importantly, truncated FurE versions lacking TMS11-12 are unable to reproduce a negative effect on the trafficking of co-expressed wild-type FurE. Overall, we show that TMS11-12 acts as an intramolecular chaperone for proper FurE folding, which seems to provide a structural code for FurE partitioning in ER-exit sites.

The interactome of the UapA transporter reveals putative new players in anterograde membrane cargo trafficking.

Neosynthesized plasma membrane (PM) proteins co-translationally translocate to the ER, concentrate at regions called ER-exit sites (ERes) and pack into COPII secretory vesicles which are sorted to the early-Golgi through membrane fusion. Following Golgi maturation, membrane cargoes reach the late-Golgi, from where they exit in clathrin-coated vesicles destined to the PM, directly or through endosomes. Post-Golgi membrane cargo trafficking also involves the cytoskeleton and the exocyst. The Golgi-dependent secretory pathway is thought to be responsible for the trafficking of all major membrane proteins. However, our recent findings in Aspergillus nidulans showed that several plasma membrane cargoes, such as transporters and receptors, follow a sorting route that seems to bypass Golgi functioning. To gain insight on membrane trafficking and specifically Golgi-bypass, here we used proximity dependent biotinylation (PDB) coupled with data-independent acquisition mass spectrometry (DIA-MS) for identifying transient interactors of the UapA transporter. Our assays, which included proteomes of wild-type and mutant strains affecting ER-exit or endocytosis, identified both expected and novel interactions that might be physiologically relevant to UapA trafficking. Among those, we validated, using reverse genetics and fluorescence microscopy, that COPI coatomer is essential for ER-exit and anterograde trafficking of UapA and other membrane cargoes. We also showed that ArfAArf1 GTPase activating protein (GAP) Glo3 contributes to UapA trafficking at increased temperature. This is the first report addressing the identification of transient interactions during membrane cargo biogenesis using PDB and proteomics coupled with fungal genetics. Our work provides a basis for dissecting dynamic membrane cargo trafficking via PDB assays.

Uracil/H+ Symport by FurE Refines Aspects of the Rocking-bundle Mechanism of APC-type Transporters.

Transporters mediate the uptake of solutes, metabolites and drugs across the cell membrane. The eukaryotic FurE nucleobase/H+ symporter of Aspergillus nidulans has been used as a model protein to address structure-function relationships in the APC transporter superfamily, members of which are characterized by the LeuT-fold and seem to operate by the so-called 'rocking-bundle' mechanism. In this study, we reveal the binding mode, translocation and release pathway of uracil/H+ by FurE using path collective variable, funnel metadynamics and rational mutational analysis. Our study reveals a stepwise, induced-fit, mechanism of ordered sequential transport of proton and uracil, which in turn suggests that FurE, functions as a multi-step gated pore, rather than employing 'rocking' of compact domains, as often proposed for APC transporters. Finally, our work supports that specific residues of the cytoplasmic N-tail are involved in substrate translocation, in line with their essentiality for FurE function.

Phytochemical investigation of Pistacia lentiscus L. var. Chia leaves: A byproduct with antimicrobial potential.

Pistacia lentiscus L. var. Chia belongs to the Anacardiaceae family, and it is cultivated only in the south part of Chios island, in Greece. Even though it is renowned for its unique resin, Chios mastic gum (CMG), the tree leaves have also been used in traditional medicine, while the annual pruning generates a large biomass of unused by-products. Thus, the aim of the present study was the detailed phytochemical investigation of P. lentiscus var. Chia leaves towards the search of antimicrobial agents. UPLC-HRMS & HRMS/MS based dereplication methods led to the detailed characterization of the aqueous leaf extract. In addition, twelve compounds were isolated and purified from the methanol extract and were identified using spectroscopic and spectrometric methods (NMR, HRMS) belonging to phenolic acids, tannins, flavonoids and terpenes, with the most interesting being 2-hydroxy-1,8-cineole ß-D-glucopyranoside which was isolated for the first time in the Anacardiaceae family. Remarkably, based on NMR data, methanol and aqueous extracts were found to be particularly rich in shikimic acid, a valuable building block for the pharmaceutical industry, for instance in the synthesis of the active ingredient of Tamiflu®, oseltamivir. Finally, extracts (EtOAc, MeOH, H2O) and major compounds i.e., shikimic acid, 2-hydroxy-1,8-cineole ß-D-glucopyranoside and myricitrin were evaluated for their antimicrobial properties. MeOH and H2O mastic leaf extracts as well as myricitrin and, particularly, 2-hydroxy-1,8-cineole ß-D-glucopyranoside showed significant selective activity against pathogenic Mucorales, but not against Aspergilli (Aspergillus nidulans, Aspergillus fumigatus), Candida albicans or bacteria (Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis).

Genetic and cellular characterization of MscS-like putative channels in the filamentous fungus Aspergillus nidulans.

Mechanosensitive ion channels are integral membrane proteins ubiquitously present in bacteria, archaea, and eukarya. They act as molecular sensors of mechanical stress to serve vital functions such as touch, hearing, osmotic pressure, proprioception and balance, while their malfunction is often associated with pathologies. Amongst them, the structurally distinct MscL and MscS channels from bacteria are the most extensively studied. MscS-like channels have been found in plants and Schizosaccharomyces pombe, where they regulate intracellular Ca2+ and cell volume under hypo-osmotic conditions. Here we characterize two MscS-like putative channels, named MscA and MscB, from the model filamentous fungus Aspergillus nidulans. Orthologues of MscA and MscB are present in most fungi, including relative plant and animal pathogens. MscA/MscB and other fungal MscS-like proteins share the three transmembrane helices and the extended C-terminal cytosolic domain that form the structural fingerprint of MscS-like channels with at least three additional transmembrane segments than Escherichia coli MscS. We show that MscA and MscB localize in Endoplasmic Reticulum and the Plasma Membrane, respectively, whereas their overexpression leads to increased CaCl2 toxicity or/and reduction of asexual spore formation. Our findings contribute to understanding the role of MscS-like channels in filamentous fungi and relative pathogens.

Nucleoside Transport and Nucleobase Uptake Null Mutants in Leishmania mexicana for the Routine Expression and Characterization of Purine and Pyrimidine Transporters.

The study of transporters is highly challenging, as they cannot be isolated or studied in suspension, requiring a cellular or vesicular system, and, when mediated by more than one carrier, difficult to interpret. Nucleoside analogues are important drug candidates, and all protozoan pathogens express multiple equilibrative nucleoside transporter (ENT) genes. We have therefore developed a system for the routine expression of nucleoside transporters, using CRISPR/cas9 to delete both copies of all three nucleoside transporters from Leishmania mexicana (ΔNT1.1/1.2/2 (SUPKO)). SUPKO grew at the same rate as the parental strain and displayed no apparent deficiencies, owing to the cells' ability to synthesize pyrimidines, and the expression of the LmexNT3 purine nucleobase transporter. Nucleoside transport was barely measurable in SUPKO, but reintroduction of L. mexicana NT1.1, NT1.2, and NT2 restored uptake. Thus, SUPKO provides an ideal null background for the expression and characterization of single ENT transporter genes in isolation. Similarly, an LmexNT3-KO strain provides a null background for transport of purine nucleobases and was used for the functional characterization of T. cruzi NB2, which was determined to be adenine-specific. A 5-fluorouracil-resistant strain (Lmex5FURes) displayed null transport for uracil and 5FU, and was used to express the Aspergillus nidulans uracil transporter FurD.

Transmembrane helices 5 and 12 control transport dynamics, substrate affinity, and specificity in the elevator-type UapA transporter.

An increasing number of solute transporters have been shown to function with the so-called sliding-elevator mechanism. Despite structural and functional differences, all elevator-type transporters use a common mechanism of substrate translocation via reversible movements of a mobile core domain (the elevator) hosting the substrate binding site along a rigid scaffold domain stably anchored in the plasma membrane via homodimerization. One of the best-studied elevator transporters is the UapA uric acid-xanthine/H+ symporter of the filamentous fungus Aspergillus nidulans. Here, we present a genetic analysis for deciphering the role of transmembrane segments (TMS) 5 and 12 in UapA transport function. We show that specific residues in both TMS5 and TMS12 control, negatively or positively, the dynamics of transport, but also substrate binding affinity and specificity. More specifically, mutations in TMS5 can lead not only to increased rate of transport but also to an inactive transporter due to high-affinity substrate-trapping, whereas mutations in TMS12 lead to apparently uncontrolled sliding and broadened specificity, leading in specific cases to UapA-mediated purine toxicity. Our findings shed new light on how elevator transporters function and how this knowledge can be applied to genetically modify their transport characteristics.

Golgi-Bypass Is a Major Unconventional Route for Translocation to the Plasma Membrane of Non-Apical Membrane Cargoes in Aspergillus nidulans.

Nutrient transporters have been shown to translocate to the plasma membrane (PM) of the filamentous fungus Aspergillus nidulans via an unconventional trafficking route that bypasses the Golgi. This finding strongly suggests the existence of distinct COPII vesicle subpopulations, one following Golgi-dependent conventional secretion and the other directed towards the PM. Here, we address whether Golgi-bypass concerns cargoes other than nutrient transporters and whether Golgi-bypass is related to cargo structure, size, abundance, physiological function, or polar vs. non-polar distribution in the PM. To address these questions, we followed the dynamic subcellular localization of two selected membrane cargoes differing in several of the aforementioned aspects. These are the proton-pump ATPase PmaA and the PalI pH signaling component. Our results show that neosynthesized PmaA and PalI are translocated to the PM via Golgi-bypass, similar to nutrient transporters. In addition, we showed that the COPII-dependent exit of PmaA from the ER requires the alternative COPII coat subunit LstA, rather than Sec24, whereas PalI requires the ER cargo adaptor Erv14. These findings strengthen the evidence of distinct cargo-specific COPII subpopulations and extend the concept of Golgi-independent biogenesis to essential transmembrane proteins, other than nutrient transporters. Overall, our findings point to the idea that Golgi-bypass might not constitute a fungal-specific peculiarity, but rather a novel major and cargo-specific sorting route in eukaryotic cells that has been largely ignored.

Interactions of cytosolic tails in the Jen1 carboxylate transporter are critical for trafficking and transport activity.

Plasma membrane (PM) transporters of the major facilitator superfamily (MFS) are essential for cell metabolism, growth and response to stress or drugs. In Saccharomyces cerevisiae, Jen1 is a monocarboxylate/H+ symporter that provides a model to dissect the molecular details underlying cellular expression, transport mechanism and turnover of MFS transporters. Here, we present evidence revealing novel roles of the cytosolic N- and C-termini of Jen1 in its biogenesis, PM stability and transport activity, using functional analyses of Jen1 truncations and chimeric constructs with UapA, an endocytosis-insensitive transporter of Aspergillus nidulans. Our results show that both N- and C-termini are critical for Jen1 trafficking to the PM, transport activity and endocytosis. Importantly, we provide evidence that Jen1 N- and C-termini undergo transport-dependent dynamic intramolecular interactions, which affect the transport activity and turnover of Jen1. Our results support an emerging concept where the cytoplasmic termini of PM transporters control transporter cell surface stability and function through flexible intramolecular interactions with each other. These findings might be extended to other MFS members to understand conserved and evolving mechanisms underlying transporter structure-function relationships. This article has an associated First Person interview with the first authors of the paper.

On the Evidence Supporting That AN11127 Encodes an Aspergillus Nidulans Sec12 Orthologous Protein. Reply to Bravo-Plaza et al. Comment on "Dimou et al. Profile of Membrane Cargo Trafficking Proteins and Transporters Expressed under N Source Derepressing Conditions in Aspergillus nidulans. J. Fungi 2021, 7, 560".

Prof. Peñalva and co-workers provided evidence that AN11127 is related by sequence and function to Sec12 [...].

Profile of Membrane Cargo Trafficking Proteins and Transporters Expressed under N Source Derepressing Conditions in Aspergillus nidulans.

Solute and ion transporters are proteins essential for cell nutrition, detoxification, signaling, homeostasis and drug resistance. Being polytopic transmembrane proteins, they are co-translationally inserted and folded into the endoplasmic reticulum (ER) of eukaryotic cells and subsequently sorted to their final membrane destination via vesicular secretion. During their trafficking and in response to physiological/stress signals or prolonged activity, transporters undergo multiple quality control processes and regulated turnover. Consequently, transporters interact dynamically and transiently with multiple proteins. To further dissect the trafficking and turnover mechanisms underlying transporter subcellular biology, we herein describe a novel mass spectrometry-based proteomic protocol adapted to conditions allowing for maximal identification of proteins related to N source uptake in A. nidulans. Our analysis led to identification of 5690 proteins, which to our knowledge constitutes the largest protein dataset identified by omics-based approaches in Aspergilli. Importantly, we detected possibly all major proteins involved in basic cellular functions, giving particular emphasis to factors essential for membrane cargo trafficking and turnover. Our protocol is easily reproducible and highly efficient for unearthing the full A. nidulans proteome. The protein list delivered herein will form the basis for downstream systematic approaches and identification of protein-protein interactions in living fungal cells.

Direct Antibiotic Activity of Bacillibactin Broadens the Biocontrol Range of Bacillus amyloliquefaciens MBI600.

Bacillus amyloliquefaciens is considered the most successful biological control agent due to its ability to colonize the plant rhizosphere and phyllosphere where it outgrows plant pathogens by competition, antibiosis, and inducing plant defense. Its antimicrobial function is thought to depend on a diverse spectrum of secondary metabolites, including peptides, cyclic lipopeptides, and polyketides, which have been shown to target mostly fungal pathogens. In this study, we isolated and characterized the catecholate siderophore bacillibactin by B. amyloliquefaciens MBI600 under iron-limiting conditions and we further identified its potential antibiotic activity against plant pathogens. Our data show that bacillibactin production restrained in vitro and in planta growth of the nonsusceptible (to MBI600) pathogen Pseudomonas syringae pv. tomato. Notably, it was also related to increased antifungal activity of MBI600. In addition to bacillibactin biosynthesis, iron starvation led to upregulation of specific genes involved in microbial fitness and competition. IMPORTANCE Siderophores have mostly been studied concerning their contribution to the fitness and virulence of bacterial pathogens. In the present work, we isolated and characterized for the first time the siderophore bacillibactin from a commercial bacterial biocontrol agent. We proved that its presence in the culture broth has significant biocontrol activity against nonsusceptible bacterial and fungal phytopathogens. In addition, we suggest that its activity is due to a new mechanism of action, that of direct antibiosis, rather than by competition through iron scavenging. Furthermore, we showed that bacillibactin biosynthesis is coregulated with the transcription of antimicrobial metabolite synthases and fitness regulatory genes that maximize competition capability. Finally, this work highlights that the efficiency and range of existing bacterial biocontrol agents can be improved and broadened via the rational modification of the growth conditions of biocontrol organisms.

Impact of Membrane Lipids on UapA and AzgA Transporter Subcellular Localization and Activity in Aspergillus nidulans.

Recent biochemical and biophysical evidence have established that membrane lipids, namely phospholipids, sphingolipids and sterols, are critical for the function of eukaryotic plasma membrane transporters. Here, we study the effect of selected membrane lipid biosynthesis mutations and of the ergosterol-related antifungal itraconazole on the subcellular localization, stability and transport kinetics of two well-studied purine transporters, UapA and AzgA, in Aspergillus nidulans. We show that genetic reduction in biosynthesis of ergosterol, sphingolipids or phosphoinositides arrest A. nidulans growth after germling formation, but solely blocks in early steps of ergosterol (Erg11) or sphingolipid (BasA) synthesis have a negative effect on plasma membrane (PM) localization and stability of transporters before growth arrest. Surprisingly, the fraction of UapA or AzgA that reaches the PM in lipid biosynthesis mutants is shown to conserve normal apparent transport kinetics. We further show that turnover of UapA, which is the transporter mostly sensitive to membrane lipid content modification, occurs during its trafficking and by enhanced endocytosis, and is partly dependent on autophagy and Hect-type HulARsp5 ubiquitination. Our results point out that the role of specific membrane lipids on transporter biogenesis and function in vivo is complex, combinatorial and transporter-dependent.

Transporter Specificity: A Tale of Loosened Elevator-Sliding.

Elevator-type transporters are a group of proteins translocating nutrients and metabolites across cell membranes. Despite structural and functional differences, elevator-type transporters use a common mechanism of substrate translocation via reversible movements of a mobile core domain (the elevator), which includes the substrate binding site, along a rigid scaffold domain, stably anchored in the plasma membrane. How substrate specificity is determined in elevator transporters remains elusive. Here, I discuss how a recent report on the sliding elevator mechanism, seen under the context of genetic analysis of a prototype fungal transporter, sheds light on how specificity might be genetically modified. I propose that flexible specificity alterations might occur by 'loosening' of the sliding mechanism from tight coupling to substrate binding.

Context-dependent Cryptic Roles of Specific Residues in Substrate Selectivity of the UapA Purine Transporter.

Members of the ubiquitous Nucleobase Ascorbate Transporter (NAT) family are H+ or Na+ symporters specific for the cellular uptake of either purines and pyrimidines or L-ascorbic acid. Despite the fact that several bacterial and fungal members have been extensively characterised at a genetic, biochemical or cellular level, and crystal structures of NAT members from Escherichia coli and Aspergillus nidulans have been determined pointing to a mechanism of transport, we have little insight on how substrate selectivity is determined. Here, we present systematic mutational analyses, rational combination of mutations, and novel genetic screens that reveal cryptic context-dependent roles of partially conserved residues in the so-called NAT signature motif in determining the specificity of the UapA transporter of A. nidulans. We show that specific NAT signature motif substitutions, alone and in combinations with each other or with distant mutations in residues known to affect substrate selectivity, lead to novel UapA versions possessing variable transport capacities and specificities for nucleobases. In particular, we show that a UapA version including the quadruple mutation T405S/F406Y/A407S/Q408E in the NAT signature motif (UapA-SYSE) becomes incapable of purine transport, but gains a novel pyrimidine-related profile, which can be further altered to a more promiscuous purine/pyrimidine profile when combined with replacements at distantly located residues, especially at F528. Our results reveal that UapA specificity is genetically highly modifiable and allow us to speculate on how the elevator-type mechanism of transport might account for this flexibility.

Life and Death of Fungal Transporters under the Challenge of Polarity.

Eukaryotic plasma membrane (PM) transporters face critical challenges that are not widely present in prokaryotes. The two most important issues are proper subcellular traffic and targeting to the PM, and regulated endocytosis in response to physiological, developmental, or stress signals. Sorting of transporters from their site of synthesis, the endoplasmic reticulum (ER), to the PM has been long thought, but not formally shown, to occur via the conventional Golgi-dependent vesicular secretory pathway. Endocytosis of specific eukaryotic transporters has been studied more systematically and shown to involve ubiquitination, internalization, and sorting to early endosomes, followed by turnover in the multivesicular bodies (MVB)/lysosomes/vacuole system. In specific cases, internalized transporters have been shown to recycle back to the PM. However, the mechanisms of transporter forward trafficking and turnover have been overturned recently through systematic work in the model fungus Aspergillus nidulans. In this review, we present evidence that shows that transporter traffic to the PM takes place through Golgi bypass and transporter endocytosis operates via a mechanism that is distinct from that of recycling membrane cargoes essential for fungal growth. We discuss these findings in relation to adaptation to challenges imposed by cell polarity in fungi as well as in other eukaryotes and provide a rationale of why transporters and possibly other housekeeping membrane proteins 'avoid' routes of polar trafficking.

Untargeted metabolomics as a hypothesis-generation tool in plant protection product discovery: Highlighting the potential of trehalose and glycerol metabolism of fungal conidiospores as novel targets.

INTRODUCTION: The production of high quality and safe food represents a main priority for the agri-food sector in the effort to sustain the exponentially growing human population. Nonetheless, there are major challenges that require the discovery of new, alternative, and improved plant protection products (PPPs). Focusing on fungal plant pathogens, the dissection of mechanisms that are essential for their survival provides insights that could be exploited towards the achievement of the aforementioned aim. In this context, the germination of fungal spores, which are essential structures for their dispersal, survival, and pathogenesis, represents a target of high potential for PPPs. To the best of our knowledge, no PPPs that target the germination of fungal spores currently exist. OBJECTIVES: Within this context, we have mined for changes in the metabolite profiles of the model fungus Aspergillus nidulans FGSC A4 conidiospores during germination, in an effort to discover key metabolites and reactions that could potentially become targets of PPPs. METHODS: Untargeted GC/EI-TOF/MS metabolomics and multivariate analyses were employed to monitor time-resolved changes in the metabolomes of germinating A. nidulans conidiospores. RESULTS: Analyses revealed that trehalose hydrolysis plays a pivotal role in conidiospore germination and highlighted the osmoregulating role of the sugar alcohols, glycerol, and mannitol. CONCLUSION: The ineffectiveness to introduce active ingredients that exhibit new mode(s)-of-action as fungicides, dictates the urge for the discovery of PPPs, which could be exploited to combat major plant protection issues. Based on the crucial role of trehalose hydrolysis in conidiospore dormancy breakage, and the subsequent involvement of glycerol in their germination, it is plausible to suggest their biosynthesis pathways as potential novel targets for the next-generation antifungal PPPs. Our study confirmed the applicability of untargeted metabolomics as a hypothesis-generation tool in PPPs' research and discovery.

Translocation of nutrient transporters to cell membrane via Golgi bypass in Aspergillus nidulans.

Nutrient transporters, being polytopic membrane proteins, are believed, but not formally shown, to traffic from their site of synthesis, the ER, to the plasma membrane through Golgi-dependent vesicular trafficking. Here, we develop a novel genetic system to investigate the trafficking of a neosynthesized model transporter, the well-studied UapA purine transporter of Aspergillus nidulans. We show that sorting of neosynthesized UapA to the plasma membrane (PM) bypasses the Golgi and does not necessitate key Rab GTPases, AP adaptors, microtubules or endosomes. UapA PM localization is found to be dependent on functional COPII vesicles, actin polymerization, clathrin heavy chain and the PM t-SNARE SsoA. Actin polymerization proved to primarily affect COPII vesicle formation, whereas the essential role of ClaH seems indirect and less clear. We provide evidence that other evolutionary and functionally distinct transporters of A. nidulans also follow the herein identified Golgi-independent trafficking route of UapA. Importantly, our findings suggest that specific membrane cargoes drive the formation of distinct COPII subpopulations that bypass the Golgi to be sorted non-polarly to the PM, and thus serving house-keeping cell functions.

mRNA decapping is an evolutionarily conserved modulator of neuroendocrine signaling that controls development and ageing.

Eukaryotic 5'-3' mRNA decay plays important roles during development and in response to stress, regulating gene expression post-transcriptionally. In Caenorhabditis elegans, deficiency of DCAP-1/DCP1, the essential co-factor of the major cytoplasmic mRNA decapping enzyme, impacts normal development, stress survival and ageing. Here, we show that overexpression of dcap-1 in neurons of worms is sufficient to increase lifespan through the function of the insulin/IGF-like signaling and its effector DAF-16/FOXO transcription factor. Neuronal DCAP-1 affects basal levels of INS-7, an ageing-related insulin-like peptide, which acts in the intestine to determine lifespan. Short-lived dcap-1 mutants exhibit a neurosecretion-dependent upregulation of intestinal ins-7 transcription, and diminished nuclear localization of DAF-16/FOXO. Moreover, neuronal overexpression of DCP1 in Drosophila melanogaster confers longevity in adults, while neuronal DCP1 deficiency shortens lifespan and affects wing morphogenesis, cell non-autonomously. Our genetic analysis in two model-organisms suggests a critical and conserved function of DCAP-1/DCP1 in developmental events and lifespan modulation.

Transporter membrane traffic and function: lessons from a mould.

Transporters are essential transmembrane proteins that mediate the selective translocation of solutes, ions or drugs across biological membranes. Their function is related to cell nutrition, communication, stress resistance and homeostasis. Consequently, their malfunction is associated with genetic or metabolic diseases and drug sensitivity or resistance. A distinctive characteristic of transporters is their cotranslational translocation and folding in a membrane bilayer, this being the endoplasmic reticulum (ER) in eukaryotes or the cell membrane in prokaryotes. In the former case, transporters exit the ER packed in secretory vesicles and traffic via seemingly unconventional, rather than Golgi-dependent, sorting routes to their final destination, the plasma membrane (PM). Proper folding is a prerequisite for ER exit and further trafficking. Misfolded transporters, either due to mutations, high temperature of chemical agents (e.g. DMSO, DTT) are blocked in the ER. The accumulation of ER-retained transporters, in most cases, elicits endoplasmic reticulum-associated degradation, but also ubiquitination-dependent, chaperone-mediated, selective autophagy. The function of PM transporters is finely regulated at the cellular level, in response to physiological or stress signals that promote, via α-arrestin-assisted ubiquitination, their endocytosis and vacuolar/lysosomal degradation, and in some cases recycling to the PM. Importantly, transporter oligomerization and specific interactions with membrane lipids are emerging as important players in transporter expression, function and turnover. This review discusses how paradigmatic work on transporters of a model mould, Aspergillus nidulans, has contributed to novel findings related to transporter functioning in eukaryotes.