Retromer associates with the cytoplasmic amino-terminus of polycystin-2.

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic human disease, with around 12.5 million people affected worldwide. ADPKD results from mutations in either PKD1 or PKD2, which encode the atypical G-protein coupled receptor polycystin-1 (PC1) and the transient receptor potential channel polycystin-2 (PC2), respectively. Although altered intracellular trafficking of PC1 and PC2 is an underlying feature of ADPKD, the mechanisms which govern vesicular transport of the polycystins through the biosynthetic and endosomal membrane networks remain to be fully elucidated. Here, we describe an interaction between PC2 and retromer, a master controller for the sorting of integral membrane proteins through the endo-lysosomal network. We show that association of PC2 with retromer occurs via a region in the PC2 cytoplasmic amino-terminal domain, independently of the retromer-binding Wiskott-Aldrich syndrome and scar homologue (WASH) complex. Based on observations that retromer preferentially interacts with a trafficking population of PC2, and that ciliary levels of PC1 are reduced upon mutation of key residues required for retromer association in PC2, our data are consistent with the identification of PC2 as a retromer cargo protein.This article has an associated First Person interview with the first author of the paper.

Phytochemicals to optimize cognitive function for military mission-readiness: a systematic review and recommendations for the field.

Context: Optimizing cognitive performance and preventing cognitive impairments that result from exposure to high-stress situations are important to ensure mission-readiness for military personnel. Objective: This systematic review assesses the quality of the evidence for plant-based foods and beverages, or their phytochemical constituents, across various outcomes related to cognitive function in healthy adult populations to develop research recommendations for the military. Data Sources: PubMed, CINAHL, Embase, PsycInfo, and the Cochrane Library were searched. Study Selection: Peer-reviewed randomized controlled trials published in the English language were eligible. Data Extraction: Twenty-five trials were included and assessed for methodological quality, and descriptive data were extracted. Data Synthesis: The acceptable (n = 16) to high-quality (n = 4) studies produced either no statistically significant effect or mixed results for enhancing cognitive function. Conclusions: The evidence suggested that healthy populations do not experience significant changes in cognitive performance when consuming soy- and non-soy-sourced isoflavones or cocoa. Heterogeneity among other interventions precluded reaching formal conclusions surrounding the evidence. Research recommendations are offered, including conducting more studies on the effect of plant-based interventions on populations reflective of military populations when exposed to military-like situations.

Caffeine to optimize cognitive function for military mission-readiness: a systematic review and recommendations for the field.

Context: In 2001 the Institute of Medicine (IOM) released a report on the use of caffeine during sustained military operations in which recommendations for research and practice were made. Objective: This systematic review serves as an update on the current quality of the evidence and addresses gaps in the current literature surrounding the effects of caffeinated foods and beverages on cognitive functioning in healthy adult populations exposed to military-like moderators. Data Sources: PubMed, CINAHL, Embase, PsycInfo, and the Cochrane Library were searched. Study Selection: Peer-reviewed randomized controlled trials published in the English language since 1998 were eligible. Data Extraction: Twenty-five trials were included and assessed for methodological quality, and descriptive data were extracted according to each military-like moderator identified. Data Synthesis: Moderators included sleep deprivation (n = 17), physical or mental exertion (n = 4), sleep deprivation combined with a sustained military operation (n = 3), and physical exertion combined with low ambient temperature (n = 1). Conclusions: The effects of caffeine supplementation on cognitive functioning in sleep-deprived subjects included improvements in attention and vigilance, complex reaction time, and problem solving and reasoning in the trials reviewed. These findings are consistent with the conclusions reached in the 2001 IOM report. This review contributes to the field by addressing gaps outlined in the IOM report.

Omega-3 polyunsaturated fatty acids to optimize cognitive function for military mission-readiness: a systematic review and recommendations for the field.

Context: There has been interest in identifying whether nutrients might help optimize cognitive performance, especially for the military tasked with ensuring mission-readiness. Objective: This systematic review assesses the quality of the evidence for n-3 polyunsaturated fatty acids (PUFAs) across various outcomes related to cognitive function in healthy adult populations in order to develop research recommendations concerning n-3 PUFAs for mission-readiness. Data Sources: PubMed, CINAHL, Embase, PsycInfo, and the Cochrane Library were searched. Study Selection: Peer-reviewed randomized controlled trials published in the English language were eligible. Data Extraction: Thirteen included trials were assessed for methodological quality, and descriptive data were extracted. Data Synthesis: Of the acceptable-quality (n = 8) and high-quality (n = 1) studies, 2 produced no statistically significant results, 5 produced mixed results, and 2 did not report between-group results. Conclusions: Results indicate that ingestion of n-3 PUFAs does not significantly alter cognitive performance in cognitively healthy persons. Studies exposing subjects to adverse circumstances that would be most relevant for drawing conclusions specifically for the military population are lacking. Several research recommendations are offered to enhance understanding of the role of fatty acids on cognitive functioning.

Whole dietary patterns to optimize cognitive function for military mission-readiness: a systematic review and recommendations for the field.

Context: Optimizing cognitive performance, particularly during times of high stress, is a prerequisite to mission-readiness among military personnel. It has been of interest to determine whether such performance could be enhanced through diet. Objective: This systematic review assesses the quality of the evidence for whole dietary patterns across various outcomes related to cognitive function in healthy adult populations to develop research recommendations for the military. Data Sources: PubMed, CINAHL, Embase, PsycInfo, and the Cochrane Library were searched. Study Selection: Peer-reviewed randomized controlled trials published in the English language were eligible. Data Extraction: Fifteen included trials were assessed for methodological quality, and descriptive data were extracted. Data Synthesis: Of the 6 acceptable-quality studies, 1 demonstrated statistically nonsignificant results, whereas the other 5 showed conflicting results across the cognitive outcomes assessed. Conclusions: Due to the heterogeneity across the included studies, no recommendations could be reached concerning whether certain whole dietary patterns have an effect on cognitive outcomes in healthy populations. Specific recommendations for future research are offered.

Retriever is a multiprotein complex for retromer-independent endosomal cargo recycling.

Following endocytosis into the endosomal network, integral membrane proteins undergo sorting for lysosomal degradation or are retrieved and recycled back to the cell surface. Here we describe the discovery of an ancient and conserved multiprotein complex that orchestrates cargo retrieval and recycling and, importantly, is biochemically and functionally distinct from the established retromer pathway. We have called this complex 'retriever'; it is a heterotrimer composed of DSCR3, C16orf62 and VPS29, and bears striking similarity to retromer. We establish that retriever associates with the cargo adaptor sorting nexin 17 (SNX17) and couples to CCC (CCDC93, CCDC22, COMMD) and WASH complexes to prevent lysosomal degradation and promote cell surface recycling of α5ß1 integrin. Through quantitative proteomic analysis, we identify over 120 cell surface proteins, including numerous integrins, signalling receptors and solute transporters, that require SNX17-retriever to maintain their surface levels. Our identification of retriever establishes a major endosomal retrieval and recycling pathway.

Atypical parkinsonism-associated retromer mutant alters endosomal sorting of specific cargo proteins.

The retromer complex acts as a scaffold for endosomal protein complexes that sort integral membrane proteins to various cellular destinations. The retromer complex is a heterotrimer of VPS29, VPS35, and VPS26. Two of these paralogues, VPS26A and VPS26B, are expressed in humans. Retromer dysfunction is associated with neurodegenerative disease, and recently, three VPS26A mutations (p.K93E, p.M112V, and p.K297X) were discovered to be associated with atypical parkinsonism. Here, we apply quantitative proteomics to provide a detailed description of the retromer interactome. By establishing a comparative proteomic methodology, we identify how this interactome is perturbed in atypical parkinsonism-associated VPS26A mutants. In particular, we describe a selective defect in the association of VPS26A (p.K297X) with the SNX27 cargo adaptor. By showing how a retromer mutant leads to altered endosomal sorting of specific PDZ ligand-containing cargo proteins, we reveal a new mechanism for perturbed endosomal cargo sorting in atypical parkinsonism.

A defect in the retromer accessory protein, SNX27, manifests by infantile myoclonic epilepsy and neurodegeneration.

The composition of the neuronal cell surface dictates synaptic plasticity and thereby cognitive development. This remodeling of the synapses is governed by the endocytic network which internalize transmembrane proteins, then sort them back to the cell surface or carry them to the lysosome for degradation. The multi-protein retromer complex is central to this selection, capturing specific transmembrane proteins and remodeling the cell membrane to form isolated cargo-enriched transport carriers. We investigated a consanguineous family with four patients who presented in infancy with intractable myoclonic epilepsy and lack of psychomotor development. Using exome analysis, we identified a homozygous deleterious mutation in SNX27, which encodes sorting nexin 27, a retromer cargo adaptor. In western analysis of patient fibroblasts, the encoded mutant protein was expressed at an undetectable level when compared with a control sample. The patients' presentation and clinical course recapitulate that reported for the SNX27 knock-out mouse. Since the cargo proteins for SNX27-mediated sorting include subunits of ionotropic glutamate receptors and endosome-to-cell surface synaptic insertion of AMPA receptors is severely perturbed in SNX27(-/-) neurons, it is proposed that at least part of the neurological aberrations observed in the patients is attributed to defective sorting of ionotropic glutamate receptors. SNX27 deficiency is now added to the growing list of neurodegenerative disorders associated with retromer dysfunction.

Retromer and sorting nexins in endosomal sorting.

The evolutionarily conserved endosomal retromer complex rescues transmembrane proteins from the lysosomal degradative pathway and facilitates their recycling to other cellular compartments. Retromer functions in conjunction with numerous associated proteins, including select members of the sorting nexin (SNX) family. In the present article, we review the molecular architecture and cellular roles of retromer and its various functional partners. The endosomal network is a crucial hub in the trafficking of proteins through the cellular endomembrane system. Transmembrane proteins, here termed cargos, enter endosomes by endocytosis from the plasma membrane or by trafficking from the trans-Golgi network (TGN). Endosomal cargo proteins face one of the two fates: retention in the endosome, leading ultimately to lysosomal degradation or export from the endosome for reuse ('recycling'). The balance of protein degradation and recycling is crucial to cellular homoeostasis; inappropriate sorting of proteins to either fate leads to cellular dysfunction. Retromer is an endosome-membrane-associated protein complex central to the recycling of many cargo proteins from endosomes, both to the TGN and the plasma membrane (and other specialized compartments, e.g. lysosome-related organelles). Retromer function is reliant on a number of proteins from the SNX family. In the present article, we discuss this inter-relationship and how defects in retromer function are increasingly being linked with human disease.

Identification of molecular heterogeneity in SNX27-retromer-mediated endosome-to-plasma-membrane recycling.

Retromer is a protein assembly that orchestrates the sorting of transmembrane cargo proteins into endosome-to-Golgi and endosome-to-plasma-membrane transport pathways. Here, we have employed quantitative proteomics to define the interactome of human VPS35, the core retromer component. This has identified a number of new interacting proteins, including ankyrin-repeat domain 50 (ANKRD50), seriologically defined colon cancer antigen 3 (SDCCAG3) and VPS9-ankyrin-repeat protein (VARP, also known as ANKRD27). Depletion of these proteins resulted in trafficking defects of retromer-dependent cargo, but differential and cargo-specific effects suggested a surprising degree of functional heterogeneity in retromer-mediated endosome-to-plasma-membrane sorting. Extending this, suppression of the retromer-associated WASH complex did not uniformly affect retromer cargo, thereby confirming cargo-specific functions for retromer-interacting proteins. Further analysis of the retromer-VARP interaction identified a role for retromer in endosome-to-melanosome transport. Suppression of VPS35 led to mistrafficking of the melanogenic enzymes, tyrosinase and tryrosine-related protein 1 (Tyrp1), establishing that retromer acts in concert with VARP in this trafficking pathway. Overall, these data reveal hidden complexities in retromer-mediated sorting and open up new directions in our molecular understanding of this essential sorting complex.

A unique PDZ domain and arrestin-like fold interaction reveals mechanistic details of endocytic recycling by SNX27-retromer.

The sorting nexin 27 (SNX27)-retromer complex is a major regulator of endosome-to-plasma membrane recycling of transmembrane cargos that contain a PSD95, Dlg1, zo-1 (PDZ)-binding motif. Here we describe the core interaction in SNX27-retromer assembly and its functional relevance for cargo sorting. Crystal structures and NMR experiments reveal that an exposed ß-hairpin in the SNX27 PDZ domain engages a groove in the arrestin-like structure of the vacuolar protein sorting 26A (VPS26A) retromer subunit. The structure establishes how the SNX27 PDZ domain simultaneously binds PDZ-binding motifs and retromer-associated VPS26. Importantly, VPS26A binding increases the affinity of the SNX27 PDZ domain for PDZ- binding motifs by an order of magnitude, revealing cooperativity in cargo selection. With disruption of SNX27 and retromer function linked to synaptic dysfunction and neurodegenerative disease, our work provides the first step, to our knowledge, in the molecular description of this important sorting complex, and more broadly describes a unique interaction between a PDZ domain and an arrestin-like fold.

A global analysis of SNX27-retromer assembly and cargo specificity reveals a function in glucose and metal ion transport.

The PDZ-domain-containing sorting nexin 27 (SNX27) promotes recycling of internalized transmembrane proteins from endosomes to the plasma membrane by linking PDZ-dependent cargo recognition to retromer-mediated transport. Here, we employed quantitative proteomics of the SNX27 interactome and quantification of the surface proteome of SNX27- and retromer-suppressed cells to dissect the assembly of the SNX27 complex and provide an unbiased global view of SNX27-mediated sorting. Over 100 cell surface proteins, many of which interact with SNX27, including the glucose transporter GLUT1, the Menkes disease copper transporter ATP7A, various zinc and amino acid transporters, and numerous signalling receptors, require SNX27-retromer to prevent lysosomal degradation and maintain surface levels. Furthermore, we establish that direct interaction of the SNX27 PDZ domain with the retromer subunit VPS26 is necessary and sufficient to prevent lysosomal entry of SNX27 cargo. Our data identify the SNX27-retromer as a major endosomal recycling hub required to maintain cellular nutrient homeostasis.