Multifunctional Transporter Research Articles

SLC26 family: a new insight for kidney stone disease.

The solute-linked carrier 26 (SLC26) protein family is comprised of multifunctional transporters of substrates that include oxalate, sulphate, and chloride. Disorders of oxalate homeostasis cause hyperoxalemia and hyperoxaluria, leading to urinary calcium oxalate precipitation and urolithogenesis. SLC26 proteins are aberrantly expressed during kidney stone formation, and consequently may present therapeutic targets. SLC26 protein inhibitors are in preclinical development. In this review, we integrate the findings of recent reports with clinical data to highlight the role of SLC26 proteins in oxalate metabolism during urolithogenesis, and discuss limitations of current studies and potential directions for future research.

Reshaping the Binding Pocket of the Neurotransmitter:Solute Symporter (NSS) Family Transporter SLC6A14 (ATB0,+) Selectively Reduces Access for Cationic Amino Acids and Derivatives.

SLC6A14 (ATB0,+) is unique among SLC proteins in its ability to transport 18 of the 20 proteinogenic (dipolar and cationic) amino acids and naturally occurring and synthetic analogues (including anti-viral prodrugs and nitric oxide synthase (NOS) inhibitors). SLC6A14 mediates amino acid uptake in multiple cell types where increased expression is associated with pathophysiological conditions including some cancers. Here, we investigated how a key position within the core LeuT-fold structure of SLC6A14 influences substrate specificity. Homology modelling and sequence analysis identified the transmembrane domain 3 residue V128 as equivalent to a position known to influence substrate specificity in distantly related SLC36 and SLC38 amino acid transporters. SLC6A14, with and without V128 mutations, was heterologously expressed and function determined by radiotracer solute uptake and electrophysiological measurement of transporter-associated current. Substituting the amino acid residue occupying the SLC6A14 128 position modified the binding pocket environment and selectively disrupted transport of cationic (but not dipolar) amino acids and related NOS inhibitors. By understanding the molecular basis of amino acid transporter substrate specificity we can improve knowledge of how this multi-functional transporter can be targeted and how the LeuT-fold facilitates such diversity in function among the SLC6 family and other SLC amino acid transporters.

Overexpression of ATP-binding cassette transporters ABCG10, ABCH3 and ABCH4 in Aphis craccivora (Koch) facilitates its tolerance to imidacloprid

Aphis craccivora (Koch), a globally pest that causes significant threat to the legumes, has developed different degrees of resistance to a variety of insecticides. The ATP-binding cassette (ABC) transporters comprise a multifunctional transporter protein superfamily which play important roles in the transport and detoxification of xenobiotic compounds in insects. However, whether ABC transporters take part in the tolerance of imidacloprid in A. craccivora is still unknown. In order to investigate the functions of ABC transporters in the imidacloprid tolerance, fifty- eight ABC transporters were identified in the transcriptome and genome of A. craccivora and the toxicity of imidacloprid against A. craccivora was significantly increased after application the inhibitors of verapamil and Ko143. The relative expression levels of ABCG5, ABCG6, ABCG10, ABCH3, ABCH4, ABCH8 and ABCH10 were significantly up-regulated in response to imidacloprid treatment with LC15, LC50 and LC85 concentrations, and the expression patterns of these seven ABC transporters were further analyzed at different developmental stages and in different tissues of A. craccivora by quantitative real-time PCR (RT-qPCR). Furthermore, knockdown of ABCG10, ABCH3 and ABCH4 significantly increased the mortality of A. craccivora to imidacloprid. Our results reveal the key functions of ABC transporters in the tolerance of imidacloprid and provide valuable information regarding the development of improved management strategies in A. craccivora.

Rv3737 is required for Mycobacterium tuberculosis growth in vitro and in vivo and correlates with bacterial load and disease severity in human tuberculosis

BackgroundRv3737 is the sole homologue of multifunctional transporter ThrE in Mycobacterium tuberculosis (Mtb). In this study, we aimed to investigate whether this transporter participates in vitro and in vivo survival of Mtb.MethodsTo characterize the role of Rv3737, we constructed and characterized a Mtb H37RvΔRv3737. This strain was evaluated for altered growth rate and macrophage survival using a cell model of infection. In addition, the comparative analysis was conducted to determine the association between Rv3737 mRNA expression and disease severity in active pulmonary TB patients.ResultsThe H37RvΔRv3737 strain exhibited significantly slow growth rate compared to H37Rv-WT strain in standard culture medium. Additionally, the survival rate of H37Rv-WT strain in macrophages was 2 folds higher than that of H37RvΔRv3737 at 72 h. A significantly higher level of TNF-α and IL-6 mRNA expression was observed in macrophages infected with H37RvΔRv3737 as compared to H37Rv-WT. Of note, Rv3737 expression was significantly increased in clinical Mtb isolates than H37Rv-WT. The relative expression level of Rv3737 was positively correlated with lung cavity number of TB patients. Similarly, the higher Rv3737 mRNA level resulted in lower C(t) value by Xpert MTB/RIF assay, demonstrating that a positive correlation between Rv3737 expression and bacterial load in TB patients.ConclusionsOur data takes the lead in demonstrate that the threonine transporter Rv3737 is required for in vitro growth and survival of bacteria inside macrophages. In addition, the expression level of Rv3737 may be associated with bacterial load and disease severity in pulmonary tuberculosis patients.

Comprehensive Genome Analysis of Halolamina pelagica CDK2: Insights into Abiotic Stress Tolerance Genes

Halophilic archaeon Halolamina pelagica CDK2, showcasing plant growth-promoting properties and endurance towards harsh environmental conditions (high salinity, heavy metals, high temperature and UV radiation) was sequenced earlier. Pan-genome of Halolamina genus was created and investigated for strain-specific genes of CDK2, which might confer it with features helping it to withstand high abiotic stress. Pathways and subsystems in CDK2 were compared with other Halolamina strain CGHMS and analysed using KEGG and RAST. A genome-scale metabolic model was reconstructed from the genome of H. pelagica CDK2. Results implicated strain-specific genes like thermostable carboxypeptidase and DNA repair protein MutS which might protect the proteins and DNA from high temperature and UV denaturation respectively. A bifunctional trehalose synthase gene responsible for trehalose biosynthesis was also annotated specifying the need for low salt compatible solute strategy, the probable reason behind the ability of this haloarchaea to survive in a wide range of salt concentrations. A modified shikimate and mevalonate pathways were also identified in CDK2, along with many ABC transporters for metal uptakes like zinc and cobalt through pathway analysis. Probable employment of one multifunctional ABC transporter in place of two for similar metals (Nickel/cobalt and molybdenum/tungsten) might be employed as a strategy for energy conservation. The findings of the present study could be utilized for future research relating metabolic model for flux balance analysis and the genetic repertoire imparting resistance to harsh conditions can be transferred to crops for improving their tolerance to abiotic stresses.

Abstract PS19-27: Upregulation of SLC26A9 resulted in the development and progression of HER2 positive breast cancer via activating TGFβ signaling pathway

Abstract Background: Slc26a9 (Solute carrier family 26 member 9) is a member of Slc26a family of multifunctional anion transporters, which functions as Cl- channel (Liu et al., Front Physiol 2018). Our previous study showed that SLC26A9 deficiency results in the development and progression of gastric cancer, which demonstrated that the key role of SLC26A9 in the tumorigenesis first time (Liu et al., Gastroenterology 2018). However, what’s the role of SLC26A9 in the breast cancer (BC) onset is not clear. We therefore wondered whether Slc26a9 gene is involved in promoting breast carcinogenesis and its mechanisms. Methods: The tissue microarrays and IHC assay were used to detect the expression and clinic relevance of SLC26A9 in the human BC. Different BC cell lines were used to investigate the expression and function of SLC26A9 in the BC. SLC26A9 gene transfect and knockout experiment were performed to detect the regulator role of SLC26A9 in BC cell behaviors. Results: Compared with adjacent normal tissues, SLC26A9 expression was significantly increased in the BC tissue, SLC26A9 expression level in BC correlated with the differentiated state of BC and patient’s clinical outcome, indicating that SLC26A9 may be involved in BC pathogenesis and progression in humans and it might be a novel poor prognosis marker for BC. Moreover, HER2 positive BC tissues exhibited high SLC26A9 expression than HER2 negative BC tissues. Compared with normal mammary cell line, SLC26A9 was significantly upregulated in the all BC cell lines, with highest expression in HER2 enriched cell line SKBR3. Deletion of SLC26A9 in SKBR3 resulted in inhibition of BC cell proliferation, migration and invasion, but promotion of cell apoptosis, which were investigated by different cell function assays, including cell counting Kit-8, cell proliferation curve, Annexin VFITC/PI double staining, Wound-healing and transwell assays respectively. Moreover, SLC26A9 deficiency in SKBR3 caused alteration of epithelial mesenchymal transition (EMT) markers, including downregulation of N-cadherin, Snail1, Fibronectin and Vimentin, but increasement of E-cadherin and ZO-1, accompany with disrupting TGFβ signaling pathways, including downregulation of TGF-β1, p-Smad2 and p-Smad3. However, overexpression of SLC26A9 in SKBR3 resulted in inhibition of cell proliferation, migration and invasion, but promotion of cell apoptosis. Accompanying with activation of TGFβ pathway mediate EMT. Conclusions: Upregulation of SLC26A9 resulted in the development and progression of HER2 positive BC via activation of TGFβ signaling pathways. SLC26A9 might be a novel prognosis marker and therapeutic target for BC. Citation Format: Zhiyuan Ma, Xuemei Liu, Chengli Lu, Jiaxing Zhu, Xiaoming Cheng, Biguang Tuo, Taolang Li. Upregulation of SLC26A9 resulted in the development and progression of HER2 positive breast cancer via activating TGFβ signaling pathway [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS19-27.

Abstract B13: Utilizing metabolic reprogramming to regulate fibroblast phenotype and reduce radiation fibrosis

Abstract Introduction: Radiation fibrosis affects up to half of all patients undergoing radiotherapy for head and neck cancer treatment. It is characterized by excess extracellular matrix deposition, leading to tissue dysfunction, distortion, hardening, and pain. There are currently no effective treatments for radiation fibrosis. A fundamental challenge has been to understand and modulate the function of fibroblasts, a key mediator in extracellular matrix production and degradation. Recent evidence has demonstrated that metabolic regulation plays an important role in altering cell behavior in cancer biology and immunology. However, little is known about how metabolic changes affect fibroblast phenotype. Hypothesis: We propose that metabolic reprogramming may be an effective strategy to modulate fibroblast function and reduce radiation fibrosis. Results: An interplay between fatty acid oxidation and glycolysis was found to be a convergence point directly governing fibroblast behavior. It was demonstrated that manipulating the balance between FAO and glycolysis in fibroblasts induced either an extracellular matrix anabolic or catabolic phenotype. Specifically, anabolic fibroblasts relied on a fatty acid oxidation to glycolysis shift to produce extracellular matrix components. Reversal of this metabolic shift generated a catabolic fibroblast, which downregulated extracellular matrix synthesis and upregulated extracellular matrix lysosomal degradation. We further uncovered that CD36, a multifunctional fatty acid transporter, was a crucial link connecting fibroblast metabolism with extracellular matrix regulation, as its depletion completely inhibited collagen-1 internalization and degradation. Finally, through metabolic reprogramming using fibroblasts expressing high levels of CD36, but not CD36 knockout fibroblasts, metabolic balance could be restored, and in turn extracellular matrix accumulation was reduced in murine radiation fibrosis. Conclusions: We have uncovered that a fibroblast’s phenotype can be differentiated and regulated based on its metabolic signature. These findings have significant implications for drug development and for future cellular therapies to reduce radiation fibrosis. Citation Format: Xiao Zhao, Pamela Psarianos, David Goldstein, Ralph Gilbert, Ian Witterick, Laurie Ailles, Benjamin Haibe-Kains, Fei-Fei Liu. Utilizing metabolic reprogramming to regulate fibroblast phenotype and reduce radiation fibrosis [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr B13.

Controlled dehydration, structural flexibility and gadolinium MRI contrast compound binding in the human plasma glycoprotein afamin.

Afamin, which is a human blood plasma glycoprotein, a putative multifunctional transporter of hydrophobic molecules and a marker for metabolic syndrome, poses multiple challenges for crystallographic structure determination, both practically and in analysis of the models. Several hundred crystals were analysed, and an unusual variability in cell volume and difficulty in solving the structure despite an ∼34% sequence identity with nonglycosylated human serum albumin indicated that the molecule exhibits variable and context-sensitive packing, despite the simplified glycosylation in insect cell-expressed recombinant afamin. Controlled dehydration of the crystals was able to stabilize the orthorhombic crystal form, reducing the number of molecules in the asymmetric unit from the monoclinic form and changing the conformational state of the protein. An iterative strategy using fully automatic experiments available on MASSIF-1 was used to quickly determine the optimal protocol to achieve the phase transition, which should be readily applicable to many types of sample. The study also highlights the drawback of using a single crystallographic structure model for computational modelling purposes given that the conformational state of the binding sites and the electron density in the binding site, which is likely to result from PEGs, greatly varies between models. This also holds for the analysis of nonspecific low-affinity ligands, where often a variety of fragments with similar uncertainty can be modelled, inviting interpretative bias. As a promiscuous transporter, afamin also seems to bind gadoteridol, a magnetic resonance imaging contrast compound, in at least two sites. One pair of gadoteridol molecules is located near the human albumin Sudlow site, and a second gadoteridol molecule is located at an intermolecular site in proximity to domain IA. The data from the co-crystals support modern metrics of data quality in the context of the information that can be gleaned from data sets that would be abandoned on classical measures.

Slc26 Family of Anion Transporters in the Gastrointestinal Tract: Expression, Function, Regulation, and Role in Disease.

SLC26 family members are multifunctional transporters of small anions, including Cl- , HCO3 - , sulfate, oxalate, and formate. Most SLC26 isoforms act as secondary (coupled) anion transporters, while others mediate uncoupled electrogenic transport resembling Cl- channels. Of the 11 described SLC26 isoforms, the SLC26A1,2,3,6,7,9,11 are expressed in the gastrointestinal tract, where they participate in salt and water transport, surface pH-microclimate regulation, affect the microbiome composition, the absorption, and secretion of oxalate and sulfate, and other functions that require further study. Several intestinal or extra-intestinal diseases are related to SLC26A mutations. Patients with congenital chloride diarrhea (CLD) suffer from Cl- -rich acidic diarrhea and systemic alkalosis due to SLC26A3 mutations. Patients with osteochondrodysplastic syndromes experience skeletal defects due to SLC26A2 mutations, resulting in defective sulfate absorption in enterocytes and sulfate uptake in chondrocytes. Because of functional interactions between SLC26 and other proteins, such as the Cl- channel CFTR, some of the intestinal cystic fibrosis manifestations may be attributed to impaired SLC26 isoform localization and function. The altered expression of SLC26 members due to inflammation or operative procedures have important consequences on intestinal transport and barrier function in common diseases as inflammatory bowel disease or bariatric surgery. The present review gives an overview on the current state of knowledge of the intestinally expressed SLC26A isoforms (SLC26A1,2,3,6,7,9,11) from the history of their functional identification, cloning and expression, the insights into their function, interaction partners and regulation gained in heterologous expression systems and Slc26a-deficient mice, to information about their transcriptional regulation and roles in gastrointestinal disease manifestations. © 2019 American Physiological Society. Compr Physiol 9:839-872, 2019.

Dimerization of GTR1 regulates their plasma membrane localization

ABSTRACTMembers of the nitrate transporter 1/peptide transporter family (NPF) are multifunctional transporters of various compounds including plant hormones and play important roles in plant growth and responses to environmental stress. Recently, we found that Arabidopsis GTR1 (also known as NPF2.10) takes up gibberellic acid and jasmonoyl-L-isoleucine in addition to glucosinolates. For normal plant growth, GTR1 is regulated at the gene expression level; however, it is unclear whether post-translational regulation also occurs. Here, we found that dimerization of GTR1, possibly induced by dephosphorylation of the Thr residue located between the possible transmembrane regions, regulates its plasma membrane localization, leading to transport of glucosinolates and gibberellic acid in Xenopus oocytes. These findings suggest that dimerization of multifunctional transporters contributes to their activities at the plasma membrane.

Applications of Functionalized Carbon Nanotubes for the Therapy and Diagnosis of Cancer.

Carbon nanotubes (CNTs) are attractive nanostructures that serve as multifunctional transporters in biomedical applications, especially in the field of cancer therapy and diagnosis. Owing to their easily tunable nature and remarkable properties, numerous functionalizations and treatments of CNTs have been attempted for their utilization as hybrid nano-carriers in the delivery of various anticancer drugs, genes, proteins, and immunotherapeutic molecules. In this review, we discuss the current advances in the applications of CNT-based novel delivery systems with an emphasis on the various functionalizations of CNTs. We also highlight recent findings that demonstrate their important roles in cancer imaging applications, demonstrating their potential as unique agents with high-level ultrasonic emission, strong Raman scattering resonance, and magnetic properties.

Correction: Efficient gene transfection to liver cells via the cellular regulation of a multifunctional polylactitol-based gene transporter.

Correction for 'Efficient gene transfection to liver cells via the cellular regulation of a multifunctional polylactitol-based gene transporter' by Young-Dong Kim et al., J. Mater. Chem. B, 2016, 4, 2208-2218.

Efficient gene transfection to hepatocytes by a multifunctional polylactitol-based gene transporter via cellular regulation

Efficient gene transfection to hepatocytes by a multifunctional polylactitol-based gene transporter via cellular regulation

The jasmonate-responsive GTR1 transporter is required for gibberellin-mediated stamen development in Arabidopsis.

Plant hormones are transported across cell membranes during various physiological events. Recent identification of abscisic acid and strigolactone transporters suggests that transport of various plant hormones across membranes does not occur by simple diffusion but requires transporter proteins that are strictly regulated during development. Here, we report that a major glucosinolate transporter, GTR1/NPF2.10, is multifunctional and may be involved in hormone transport in Arabidopsis thaliana. When heterologously expressed in oocytes, GTR1 transports jasmonoyl-isoleucine and gibberellin in addition to glucosinolates. gtr1 mutants are severely impaired in filament elongation and anther dehiscence resulting in reduced fertility, but these phenotypes can be rescued by gibberellin treatment. These results suggest that GTR1 may be a multifunctional transporter for the structurally distinct compounds glucosinolates, jasmonoyl-isoleucine and gibberellin, and may positively regulate stamen development by mediating gibberellin supply.

Making an Aquaporin Water-Tight: Structural Basis of Selectivity in Plant Nodulin 26 Intrinsic Proteins

The evolution of land plants led toan amplification and diversification of the aquaporin superfamily of membrane channels. Among the subfamilies of plant specific aquaporin-like changes are the nodulin-26 intrinsic proteins (NIPs) which are multifunctional transporters of water, ammonia, glycerol and metalloid nutrients that participate in a number of osmoregulatory and metabolic functions. NIPs share the canonical hourglass fold of the aquaporin family, but possess substitutions within the aromatic arginine (ar/R) selectivity filter. The nine proteins of the NIP subfamily in the model plant Arabidopsis thaliana can be subdivided into two ar/R pore subgroups: the NIP subgroup I, which form aquaglyceroporins that are permeated by glycerol, water and ammonia, and the NIP subgroup II, which form metalloid transporters which are lack aquaporin activity and are essentially “water tight”. These two NIP pore families differ principally by the substitution of a conserved alanine (NIP subgroup II) for a conserved tryptophan (NIP subgroup I) in the helix 2 position (H2) of the ar/R filter. Based on transport analyses and molecular dynamics simulation, a model is proposed through which the alanine substitution results in both the selectivity for critical metalloid nutrients such as boric acid while simultaneously restricting water flow through the ar/R selectivity filter. A mechanism involving two different rotameric states of the conserved arginine residue in this selectivity region is proposed to be responsible for the water-tight character of the pore. (Supported in part by NSF grant 1121465).

Transport in technicolor: mapping ATP-binding cassette transporters in sea urchin embryos.

One quarter of eukaryotic genes encode membrane proteins. These include nearly 1,000 transporters that translocate nutrients, signaling molecules, and xenobiotics across membranes. While it is well appreciated that membrane transport is critical for development, the specific roles of many transporters have remained cryptic, in part because of their abundance and the diversity of their substrates. Multidrug resistance ATP-binding cassette (ABC) efflux transporters are one example of cryptic membrane proteins. Although most organisms utilize these ABC transporters during embryonic development, many of these transporters have broad substrate specificity, and their developmental functions remain incompletely understood. Here, we review advances in our understanding of ABC transporters in sea urchin embryos, and methods developed to spatially and temporally map these proteins. These studies reveal that multifunctional transporters are required for signaling, homeostasis, and protection of the embryo, and shed light on how they are integrated into ancestral developmental pathways recapitulated in disease.

Apoferritin applications in nanomedicine.

Nanomedicine as a continuously evolving discipline is still looking for a structure with perfect properties that is usable as a multifunctional transporter. Great potential is attributed to synthetic materials such as fullerenes, porous hollow silica nanoparticles and single-wall nanotubes, among others. However, materials that are natural to the human body are more acceptable by the organism, and thus become an attractive approach in this field of research. Ferritins are proteins that naturally occur in most living organisms throughout evolution and may be a possible transporter choice. Numerous applications have demonstrated the possibilities of iron-free ferritins, called apoferritins, serving as platforms for various nanomedical purposes This article summarizes the advantages and disadvantages of these proteins and discusses their practical applications and future perspectives.

Arabidopsis thalianaNIP7;1: An Anther-Specific Boric Acid Transporter of the Aquaporin Superfamily Regulated by an Unusual Tyrosine in Helix 2 of the Transport Pore

Plant nodulin-26 intrinsic proteins (NIPs) are members of the aquaporin superfamily that serve as multifunctional transporters of uncharged metabolites. In Arabidopsis thaliana, a specific NIP pore subclass, known as the NIP II proteins, is represented by AtNIP5;1 and AtNIP6;1, which encode channel proteins expressed in roots and leaf nodes, respectively, that participate in the transport of the critical cell wall nutrient boric acid. Modeling of the protein encoded by the AtNIP7;1 gene shows that it is a third member of the NIP II pore subclass in Arabidopsis. However, unlike AtNIP5;1 and AtNIP6;1 proteins, which form constitutive boric acid channels, AtNIP7;1 forms a channel with an extremely low intrinsic boric acid transport activity. Molecular modeling and molecular dynamics simulations of AtNIP7;1 suggest that a conserved tyrosine residue (Tyr81) located in transmembrane helix 2 adjacent to the aromatic arginine (ar/R) pore selectivity region stabilizes a closed pore conformation through interaction with the canonical Arg220 in ar/R region. Substitution of Tyr81 with a Cys residue, characteristic of established NIP boric acid channels, results in opening of the AtNIP7;1 pore that acquires a robust, transport activity for boric acid as well as other NIP II test solutes (glycerol and urea). Substitution of a Phe for Tyr81 also opens the channel, supporting the prediction from MD simulations that hydrogen bond interaction between the Tyr81 phenol group and the ar/R Arg may contribute to the stabilization of a closed pore state. Expression analyses show that AtNIP7;1 is selectively expressed in developing anther tissues of young floral buds of A. thaliana, principally in developing pollen grains of stage 9-11 anthers. Because boric acid is both an essential nutrient as well as a toxic compound at high concentrations, it is proposed that Tyr81 modulates transport and may provide an additional level of regulation for this transporter in male gametophyte development.

X-linked cholestasis in mouse due to mutations of the P4-ATPase ATP11C

Transporters at the hepatic canalicular membrane are essential for the formation of bile and the prevention of cholestatic liver disease. One such example is ATP8B1, a P4-type ATPase disrupted in three inherited forms of intrahepatic cholestasis. Mutation of the X-linked mouse gene Atp11c, which encodes a paralogous P4-type ATPase, precludes B-cell development in the adult bone marrow, but also causes hyperbilirubinemia. Here we explore this hyperbilirubinemia in two independent Atp11c mutant mouse lines, and find that it originates from an effect on nonhematopoietic cells. Liver function tests and histology revealed only minor pathology, although cholic acid was elevated in the serum of mutant mice, and became toxic to mutant mice when given as a dietary supplement. The majority of homozygous mutant females also died of dystocia in a maternal genotype-specific manner. ATP11C therefore represents a multifunctional transporter, essential for adult B-cell development, the prevention of intrahepatic cholestasis, and parturition, and is a new candidate for genetically undiagnosed cases of cholestasis and dystocia in humans.

Ral-Binding Protein is Required for the Maturation and Function of Dendritic Cells

Problem statement: Dendritic Cells (DCs) integrate responses of innate and adaptive immune system via transmitting pro-inflammatory and regulatory signals to naïve cells within draining lymph nodes. DCs have high capacity for endocytosis, both Clathrin-Dependent (CDE) and Caveolin-Dependent (CvDE). Approach: We have recently shown that ATP-hydrolysis by the multifunctional transporter protein RLIP76 is the primary determinant of the rate of CDE. Activation of CDE is necessary for DCs to internalize and process exogenous antigens. Thus, in present studies we investigated the role of RLIP76 in antigen uptake, maturation and T cell priming capacity of monocyte-derived DCs. Results: Using flow cytometry, we demonstrate variable surface expression of RLIP76 on immature DCs generated from peripheral blood mononuclear cells from healthy individuals. Studies on the effect of anti-RLIP76 antibodies on endocytosis of DC-specific C-type Lectin Receptors (CLRs) (DC-SIGN and DEC-205) and on co-localization of these receptors with MHC-class II were conducted using confocal microscopy. RLIP76-specific antibodies suppressed the maturation of DCs and the expression of typical activation markers and co-stimulatory and adhesion molecules including CD83, HLA-DR, HLA-ABC, CD40, CD80 and CD38. They also inhibited the stimulating potency of DCs in allogeneic Mixed Leukocyte Reaction (allo-MLR). Conclusions: We conclude that RLIP76 is necessary for activation, membrane trafficking and functional maturation of DCs. Further exploration of the role of RLIP76 in DC biology is warranted and may provide promising means in DC-based immunotherapies.