UDP-glucose:glycoprotein Glucosyltransferase Research Articles

Rescue of secretion of rare-disease-associated misfolded mutant glycoproteins in UGGT1 knock-out mammalian cells.

Endoplasmic reticulum (ER) retention of misfolded glycoproteins is mediated by the ER-localized eukaryotic glycoprotein secretion checkpoint, UDP-glucose glycoprotein glucosyl-transferase (UGGT). The enzyme recognizes a misfolded glycoprotein and flags it for ER retention by re-glucosylating one of its N-linked glycans. In the background of a congenital mutation in a secreted glycoprotein gene, UGGT-mediated ER retention can cause rare disease, even if the mutant glycoprotein retains activity ("responsive mutant"). Using confocal laser scanning microscopy, we investigated here the subcellular localization of the human Trop-2-Q118E, E227K and L186P mutants, which cause gelatinous drop-like corneal dystrophy (GDLD). Compared with the wild-type Trop-2, which is correctly localized at the plasma membrane, these Trop-2 mutants are retained in the ER. We studied fluorescent chimeras of the Trop-2 Q118E, E227K and L186P mutants in mammalian cells harboring CRISPR/Cas9-mediated inhibition of the UGGT1 and/or UGGT2 genes. The membrane localization of the Trop-2 Q118E, E227K and L186P mutants was successfully rescued in UGGT1-/- cells. UGGT1 also efficiently reglucosylated Trop-2-Q118E-EYFP in cellula. The study supports the hypothesis that UGGT1 modulation would constitute a novel therapeutic strategy for the treatment of pathological conditions associated to misfolded membrane glycoproteins (whenever the mutation impairs but does not abrogate function), and it encourages the testing of modulators of ER glycoprotein folding quality control as broad-spectrum rescue-of-secretion drugs in rare diseases caused by responsive secreted glycoprotein mutants.

The TaSep15–like-B-TaUGGT-B2–TaVSR-B pathway positively regulates nickel stress in wheat

The function and mechanism of proteins involved in the endoplasmic reticulum (ER) quality control system in plants in the response to heavy metals remain largely unknown. In this study, 15-kDa selenoprotein (Sep15) homolog gene (Sep15-like) was characterized in wheat. Its transcript, induced by nickel treatment, was abundant in the roots and leaves, and its protein localized to the ER. Constitutive TaSep15-like-B expression enhanced tolerance to nickel stress in wheat and Arabidopsis, likely via the regulation of ER stress homeostasis and ROS balance. Wheat UDP-glucose:glycoprotein glucosyltransferase (UGGT)-B2, a key enzyme in ER quality control with the reglucosylation of the glycoprotein, was identified as a partner of TaSep15-like-B. Further studies revealed that TaUGGT-B2 interacted with a wheat vacuolar sorting receptor B, TaVSR-B, which mediates the sorting of soluble proteins to vacuoles in the secretory pathway. Our findings revealed a mechanistic framework underlying the TaSep15-like-B-TaUGGT-B2-TaVSR-B module-mediated regulation of nickel response.

A quinolin-8-ol sub-millimolar inhibitor of UGGT, the ER glycoprotein folding quality control checkpoint

Misfolded glycoprotein recognition and endoplasmic reticulum (ER) retention are mediated by the ER glycoprotein folding quality control (ERQC) checkpoint enzyme, UDP-glucose glycoprotein glucosyltransferase (UGGT). UGGT modulation is a promising strategy for broad-spectrum antivirals, rescue-of-secretion therapy in rare disease caused by responsive mutations in glycoprotein genes, and many cancers, but to date no selective UGGT inhibitors are known. The small molecule 5-[(morpholin-4-yl)methyl]quinolin-8-ol (5M-8OH-Q) binds a CtUGGTGT24 "WY" conserved surface motif conserved across UGGTs but not present in other GT24 family glycosyltransferases. 5M-8OH-Q has a 47μM binding affinity for CtUGGTGT24invitro as measured by ligand-enhanced fluorescence. In cellula, 5M-8OH-Q inhibits both human UGGT isoforms at concentrations higher than 750μM. 5M-8OH-Q binding to CtUGGTGT24 appears to be mutually exclusive to M5-9 glycan binding in an invitro competition experiment. A medicinal program based on 5M-8OH-Q will yield the next generation of UGGT inhibitors.

Crystal polymorphism in fragment-based lead discovery of ligands of the catalytic domain of UGGT, the glycoprotein folding quality control checkpoint.

None of the current data processing pipelines for X-ray crystallography fragment-based lead discovery (FBLD) consults all the information available when deciding on the lattice and symmetry (i.e., the polymorph) of each soaked crystal. Often, X-ray crystallography FBLD pipelines either choose the polymorph based on cell volume and point-group symmetry of the X-ray diffraction data or leave polymorph attribution to manual intervention on the part of the user. Thus, when the FBLD crystals belong to more than one crystal polymorph, the discovery pipeline can be plagued by space group ambiguity, especially if the polymorphs at hand are variations of the same lattice and, therefore, difficult to tell apart from their morphology and/or their apparent crystal lattices and point groups. In the course of a fragment-based lead discovery effort aimed at finding ligands of the catalytic domain of UDP-glucose glycoprotein glucosyltransferase (UGGT), we encountered a mixture of trigonal crystals and pseudotrigonal triclinic crystals-with the two lattices closely related. In order to resolve that polymorphism ambiguity, we have written and described here a series of Unix shell scripts called CoALLA (crystal polymorph and ligand likelihood-based assignment). The CoALLA scripts are written in Unix shell and use autoPROC for data processing, CCP4-Dimple/REFMAC5 and BUSTER for refinement, and RHOFIT for ligand docking. The choice of the polymorph is effected by carrying out (in each of the known polymorphs) the tasks of diffraction data indexing, integration, scaling, and structural refinement. The most likely polymorph is then chosen as the one with the best structure refinement Rfree statistic. The CoALLA scripts further implement a likelihood-based ligand assignment strategy, starting with macromolecular refinement and automated water addition, followed by removal of the water molecules that appear to be fitting ligand density, and a final round of refinement after random perturbation of the refined macromolecular model, in order to obtain unbiased difference density maps for automated ligand placement. We illustrate the use of CoALLA to discriminate between H3 and P1 crystals used for an FBLD effort to find fragments binding to the catalytic domain of Chaetomium thermophilum UGGT.

Front Cover: Analysis of Selenoprotein F Binding to UDP‐Glucose:Glycoprotein Glucosyltransferase (UGGT) by a Photoreactive Crosslinker (ChemBioChem 5/2023)

Front Cover: Analysis of Selenoprotein F Binding to UDP‐Glucose:Glycoprotein Glucosyltransferase (UGGT) by a Photoreactive Crosslinker (ChemBioChem 5/2023)

Analysis of Selenoprotein F Binding to UDP-Glucose:Glycoprotein Glucosyltransferase (UGGT) by a Photoreactive Crosslinker.

In the endoplasmic reticulum glycoprotein quality control system, UDP-glucose : glycoprotein glucosyltransferase (UGGT) functions as a folding sensor. Although it is known to form a heterodimer with selenoprotein F (SelenoF), the details of the complex formation remain obscure. A pulldown assay using co-transfected SelenoF and truncated mutants of human UGGT1 (HUGT1) revealed that SelenoF binds to the TRXL2 domain of HUGT1. Additionally, a newly developed photoaffinity crosslinker was selectively introduced into cysteine residues of recombinant SelenoF to determine the spatial orientation of SelenoF to HUGT1. The crosslinking experiments showed that SelenoF formed a covalent bond with amino acids in the TRXL3 region and the interdomain between βS2 and GT24 of HUGT1 via the synthetic crosslinker. SelenoF might play a role in assessing and refining the disulfide bonds of misfolded glycoproteins in the hydrophobic cavity of HUGT1 as it binds to the highly flexible region of HUGT1 to reach its long hydrophobic cavity. Clarification of the SelenoF-binding domain of UGGT and its relative position will help predict and reveal the function of SelenoF from a structural perspective.

UDP-glucose, cereblon-dependent proinsulin degrader

Insulin secretion is regulated in multiple steps, and one of the main steps is in the endoplasmic reticulum (ER). Here, we show that UDP-glucose induces proinsulin ubiquitination by cereblon, and uridine binds and competes for proinsulin degradation and behaves as sustainable insulin secretagogue. Using insulin mutagenesis of neonatal diabetes variant-C43G and maturity-onset diabetes of the young 10 (MODY10) variant-R46Q, UDP-glucose:glycoprotein glucosyltransferase 1 (UGGT1) protects cereblon-dependent proinsulin ubiquitination in the ER. Cereblon is a ligand-inducible E3 ubiquitin ligase, and we found that UDP-glucose is the first identified endogenous proinsulin protein degrader. Uridine-containing compounds, such as uridine, UMP, UTP, and UDP-galactose, inhibit cereblon-dependent proinsulin degradation and stimulate insulin secretion from 3 to 24 h after administration in β-cell lines as well as mice. This late and long-term insulin secretion stimulation is designated a day sustainable insulin secretion stimulation. Uridine-containing compounds are designated as proinsulin degradation regulators.

Tandem mass tag-based proteomic analysis of endoplasmic reticulum proteins in mulberry leaves under ultraviolet-B and dark stress.

Mulberry leaves have been used in traditional Chinese medicine due to their antioxidant, antidiabetic, and antihyperlipidemic properties. A previous study showed that ultraviolet-B radiation followed by dark incubation could improve the contents of active ingredients in mulberry leaves, such as moracin N and chalcomoracin. The endoplasmic reticulum (ER) serves as a protein quality control center and the location for protein synthesis, which is involved in the response to the environmental stress in plants. To investigate the mechanisms in response to ultraviolet-B radiation followed by dark incubation (UV + D), ER proteomics was performed on mulberry leaves. The ER protein markers, glucose-regulated protein (GRP78), and calnexin (CNX), were significantly higher in the ER fraction than in the total protein fraction, indicating that the ER was purified. Compared to the control, the abundance of protein disulfide isomerase, UDP-glucose glycoprotein glucosyltransferase, CNX, and calreticulin proteins decreased, while of the abundance of heat shock-related proteins increased under stress. P450 enzyme system-related proteins and ribosomal proteins showed significant increases. These results suggest that under UV + D stress, mulberry leaves activated the cell redox and ER quality control systems, enhancing protein synthesis and weakening N-glycan biosynthesis in the ER to resist the damage.

Structural insights into how GlcNAc-1-phosphotransferase directs lysosomal protein transport

GlcNAc-1-phosphotransferase catalyzes the initial step in the formation of the mannose-6-phosphate tag that labels ∼60 lysosomal proteins for transport. Mutations in GlcNAc-1-phosphotransferase are known to cause lysosomal storage disorders such as mucolipidoses. However, the molecular mechanism of GlcNAc-1-phosphotransferase activity remains unclear. Mammalian GlcNAc-1-phosphotransferases are α2β2γ2 hexamers in which the core catalytic α- and β-subunits are derived from the GNPTAB (N-acetylglucosamine-1-phosphate transferase subunits alpha and beta) gene. Here, we present the cryo-electron microscopy structure of the Drosophila melanogaster GNPTAB homolog, DmGNPTAB. We identified four conserved regions located far apart in the sequence that fold into the catalytic domain, which exhibits structural similarity to that of the UDP–glucose glycoprotein glucosyltransferase. Comparison with UDP–glucose glycoprotein glucosyltransferase also revealed a putative donor substrate-binding site, and the functional requirements of critical residues in human GNPTAB were validated using GNPTAB-knockout cells. Finally, we show that DmGNPTAB forms a homodimer that is evolutionarily conserved and that perturbing the dimer interface undermines the maturation and activity of human GNPTAB. These results provide important insights into GlcNAc-1-phosphotransferase function and related diseases.

Structural Insights into GlcNAc-1-Phosphotransferase that Directs Lysosomal Protein Transport

GlcNAc-1-phosphotransferase catalyzes the initial step in the formation of the mannose-6-phosphate tag that labels ~60 lysosomal proteins for transport. Mutations in GlcNAc-1-phosphotransferase cause lysosomal storage disorders such as mucolipidoses. However, the molecular mechanism of GlcNAc-1-phosphotransferase remains unclear. Mammalian GlcNAc-1-phosphotransferases are α2β2γ2 hexamers in which the core catalytic α- and β-subunits are derived from GNPTAB. Here, we present the cryo-electron microscopy structure of the Drosophila melanogaster GNPTAB homolog (DmGNPTAB). Four conserved regions located far apart in the sequence fold into the catalytic domain, which exhibits structural similarity to that of the UDP-glucose glycoprotein glucosyltransferase (UGGT). Comparison with UGGT revealed a putative donor substrate-binding site, and the functional requirements of critical residues in human GNPTAB were validated using GNPTAB-knockout cells. DmGNPTAB forms an evolutionarily conserved homodimer, and perturbing the dimer interface undermines the maturation and activity of human GNPTAB. These results provide important insights into GlcNAc-1-phosphotransferase function and related diseases.

Glycosylation limits forward trafficking of the tetraspan membrane protein PMP22

Peripheral myelin protein 22 (PMP22) folds and trafficks inefficiently, with only 20% of newly expressed protein trafficking to the cell surface. This behavior is exacerbated in many of the mutants associated with Charcot–Marie–Tooth disease, motivating further study. Here we characterized the role of N-glycosylation in limiting PMP22 trafficking. We first eliminated N-glycosylation using an N41Q mutation, which resulted in an almost 3-fold increase in trafficking efficiency of wildtype (WT) PMP22 and a 10-fold increase for the severely unstable L16P disease mutant in HEK293 cells, with similar results in Schwann cells. Total cellular levels were also much higher for the WT/N41Q mutant, although not for the L16P/N41Q form. Depletion of oligosaccharyltransferase OST-A and OST-B subunits revealed that WT PMP22 is N-glycosylated posttranslationally by OST-B, whereas L16P is cotranslationally glycosylated by OST-A. Quantitative proteomic screens revealed similarities and differences in the interactome for WT, glycosylation-deficient, and unstable mutant forms of PMP22 and also suggested that L16P is sequestered at earlier stages of endoplasmic reticulum quality control. CRISPR knockout studies revealed a role for retention in endoplasmic reticulum sorting receptor 1 (RER1) in limiting the trafficking of all three forms, for UDP-glucose glycoprotein glucosyltransferase 1 (UGGT1) in limiting the trafficking of WT and L16P but not N41Q, and calnexin (CNX) in limiting the trafficking of WT and N41Q but not L16P. This work shows that N-glycosylation is a limiting factor to forward trafficking PMP22 and sheds light on the proteins involved in its quality control.

Quantitative glycoproteomics reveals cellular substrate selectivity of the ER protein quality control sensors UGGT1 and UGGT2.

UDP-glucose:glycoprotein glucosyltransferase (UGGT) 1 and 2 are central hubs in the chaperone network of the endoplasmic reticulum (ER), acting as gatekeepers to the early secretory pathway, yet little is known about their cellular clients. These two quality control sensors control lectin chaperone binding and glycoprotein egress from the ER. A quantitative glycoproteomics strategy was deployed to identify cellular substrates of the UGGTs at endogenous levels in CRISPR-edited HEK293 cells. The 71 UGGT substrates identified were mainly large multidomain and heavily glycosylated proteins when compared to the general N-glycoproteome. UGGT1 was the dominant glucosyltransferase with a preference toward large plasma membrane proteins whereas UGGT2 favored the modification of smaller, soluble lysosomal proteins. This study sheds light on differential specificities and roles of UGGT1 and UGGT2 and provides insight into the cellular reliance on the carbohydrate-dependent chaperone system to facilitate proper folding and maturation of the cellular N-glycoproteome.

Glycan dependent refolding activity of ER glucosyltransferase (UGGT)

BackgroundIn the endoplasmic reticulum (ER), folding of glycoproteins is assisted by a combined action of enzymes and chaperones that leads them to biologically functional structures. In this system, UDP-glucose:glycoprotein glucosyltransferase 1 (UGGT1) plays an essential role as the “folding sensor” by virtue of its ability to discriminate folding states of client glycoproteins. However, besides its transferase activity, whether UGGT1 possesses any chaperone activity that facilitates protein folding is yet to be addressed. MethodsWe prepared oligomannose-type glycan modified RNase (M9GN2-RNase) by chemoenzymatic means using M9GN-oxazoline and glycan truncated RNase B and analyzed the effect of human UGGT1 (HUGT1) for refolding of the denatured M9GN2-RNase. Refolding was evaluated based on the RNase activity which was measured by the cleavage of the RNA substrate. ResultsHUGT1 slightly accelerated the folding of M9GN2-RNase and non-glycosylated RNase A as the same extent. However, HUGT1 remarkably accelerated the folding of M9GN2-RNase in the presence of UDP-Glc. In contrast, neither UDP nor UDP-Gal was effective in enhancing the folding. Additionally, an HUGT1 mutant which lacks the glucosyltransferase activity did not accelerate the protein folding of M9GN2-RNase. ConclusionsHUGT1has the ability to promote the refolding of denatured protein and the effect would be enhanced when HUGT1 tightly interacts with the client protein via glycan recognition. General significanceOur study provides a possibility that HUGT1 play a role not only in sensing the misfolded glycoprotein but also in promoting folding of glycoproteins in the endoplasmic reticulum glycoprotein quality control.

UGGT1 retains proinsulin in the endoplasmic reticulum in an arginine dependent manner

We sought to clarify a pathway by which L- and dD-arginine simulate insulin secretion in mice and cell lines and obtained the following novel two findings. (1) Using affinity magnetic nanobeads technology, we identified that proinsulin is retained in the endoplasmic reticulum (ER) through UDP-glucose:glycoprotein glucosyltransferase 1 (UGGT1) when arginine availability is limited. (2) L- and d-arginine release proinsulin from UGGT1 through competition with proinsulin and promote exit of proinsulin from the ER to Golgi apparatus. The ability of arginine to release proinsulin from UGGT1 closely correlates with arginine-induced insulin secretion in several models of β cells indicating that UGGT1-proinsulin interaction regulates arginine-induced insulin secretion.

Calnexin cycle - structural features of the ER chaperone system.

The endoplasmic reticulum (ER) is the major folding compartment for secreted and membrane proteins and is the site of a specific chaperone system, the calnexin cycle, for folding N‐glycosylated proteins. Recent structures of components of the calnexin cycle have deepened our understanding of quality control mechanisms and protein folding pathways in the ER. In the calnexin cycle, proteins carrying monoglucosylated glycans bind to the lectin chaperones calnexin and calreticulin, which recruit a variety of function‐specific chaperones to mediate protein disulfide formation, proline isomerization, and general protein folding. Upon trimming by glucosidase II, the glycan without an inner glucose residue is no longer able to bind to the lectin chaperones. For proteins that have not yet folded properly, the enzyme UDP‐glucose:glycoprotein glucosyltransferase (UGGT) acts as a checkpoint by adding a glucose back to the N‐glycan. This allows the misfolded proteins to re‐associate with calnexin and calreticulin for additional rounds of chaperone‐mediated refolding and prevents them from exiting the ERs. Here, we review progress in structural studies of the calnexin cycle, which reveal common features of how lectin chaperones recruit function‐specific chaperones and how UGGT recognizes misfolded proteins.

Clamping, Bending, and Twisting Inter-Domain Motions in the Misfold-Recognising Portion of UDP-Glucose: Glycoprotein Glucosyl-Transferase

UDP-glucose: glycoprotein glucosyltransferase (UGGT) is the glycoprotein folding checkpoint in the eukaryotic glycoprotein secretory pathway. The enzyme detects misfolded glycoproteins in the Endoplasmic Reticulum, and flags them for retention by re-glucosylating them on an N-linked glycan. The fit of a UGGT crystal structure to a negative stain electron microscopy reconstruction of UGGT in complex with an antibody suggests that the misfold-sensing N-terminal portion of UGGT and its C-terminal catalytic domain are tightly associated. Molecular Dynamics (MD) simulations capture UGGT in so far unobserved conformational states, and principal component analysis of the MD trajectories affords a description of UGGT's overall inter-domain motions, highlighting three types of inter-domain movements: bending, twisting and clamping. These inter-domain motions modify the accessible surface area of the enzyme's central saddle. We propose to name the maximum distance between a site of misfolding on a UGGT glycoprotein substrate and an N-linked glycan that monomeric UGGT can re-glucosylate on the same glycoprotein. MD simulations estimate the Parodi limit to be around 60-70 A. Re-glucosylation assays using UGGT deletion mutants suggest that the TRXL2 domain is necessary for activity against urea-misfolded bovine thyroglobulin. Our findings support a one-size-fits-all adjustable spanner substrate recognition model, with a crucial role for the TRXL2 domain in the recruitment of misfolded substrates.

Lack of endoplasmic reticulum quality control (ERQC) promotes tonoplast (TP) targeting of KORRIGAN 1 (KOR1)

ABSTRACTCellular dynamics of KORRIGAN 1 (KOR1) is closely linked with cellulose biosynthesis and plant osmotic stress tolerance. Cycling of KOR1 between the plasma membrane (PM) and trans-Golgi Network (TGN) is maintained by sequence motifs and protein structures that are recognized by cellular transport and quality control mechanisms. Several mutations in KOR1, as well as in the host genetic background, promote the mistargeting of KOR1 and induce KOR1 accumulation in the tonoplast (TP). Yet, little is known about how retention and sorting of KOR1 are regulated in the PM-TGN cycle. Forward genetic screening for GFP-KOR1 mislocalizing phenotype resulted in several mutant lines with different localization patterns or signal intensity of GFP-KOR1. One of the identified mutants were disrupted at UDP-glucose:glycoprotein glucosyltransferase (UGGT) locus, which is essential for the protein quality control in the ER. Our finding suggests the mis/unfolded structure of KOR1 triggers the TP targeting.

Origin and Evolution of Two Independently Duplicated Genes Encoding UDP- Glucose: Glycoprotein Glucosyltransferases in Caenorhabditis and Vertebrates.

UDP- glucose: glycoprotein glucosyltransferase (UGGT) is a protein that operates as the gatekeeper for the endoplasmic reticulum (ER) quality control mechanism of glycoprotein folding. It is known that vertebrates and Caenorhabditis genomes harbor two uggt gene copies that exhibit differences in their properties.Bayesian phylogenetic inference based on 195 UGGT and UGGT-like protein sequences of an ample spectrum of eukaryotic species showed that uggt genes went through independent duplications in Caenorhabditis and vertebrates. In both lineages, the catalytic domain of the duplicated genes was subjected to a strong purifying selective pressure, while the recognition domain was subjected to episodic positive diversifying selection. Selective relaxation in the recognition domain was more pronounced in Caenorhabditis uggt-b than in vertebrates uggt-2. Structural bioinformatics analysis revealed that Caenorhabditis UGGT-b protein lacks essential sequences proposed to be involved in the recognition of unfolded proteins. When we assayed glucosyltrasferase activity of a chimeric protein composed by Caenorhabditis uggt-b recognition domain fused to S. pombe catalytic domain expressed in yeast, no activity was detected.The present results support the conservation of the UGGT activity in the catalytic domain and a putative divergent function of the recognition domain for the UGGT2 protein in vertebrates, which would have gone through a specialization process. In Caenorhabditis, uggt-b evolved under different constraints compared to uggt-a which, by means of a putative neofunctionalization process, resulted in a non-redundant paralog. The non-canonical function of uggt-b in the worm lineage highlights the need to take precautions before generalizing gene functions in model organisms.

Evaluation by re-derivation of a paternal line after 18 generations on seminal traits, proteome and fertility

Males from a paternal line selected for growth traits were used to produce semen doses at insemination centres and farms in a breeding scheme for rabbit meat production. The aim of this study was to assess whether a program of selection by daily gain in fattening period changed the seminal traits, plasma and sperm proteome and the fertility of semen when used in artificial insemination. Thirty-nine males from a paternal line were obtained by re-derivation from vitrified embryos with a difference of 18 generations (G21V and G39V). Sperm production parameters, morphological traits, sperm motility parameters and viability were evaluated from ejaculates. Seminal plasma and sperm proteome of three pool ejaculates from 10 mature males of each group were analysed and semen doses were used to inseminate 311 females. Only the percentage of abnormal sperm showed significant differences, with G21V presenting fewer abnormal sperm than G39V (10.5 ± 2.63 vs 23.8 ± 1.98). The discriminant analysis (DA-PLS) showed a clear effect of the generation for plasma and sperm proteome. In seminal plasma, 643 proteins were reported and 64 proteins were differentially expressed, of which 56 were overexpressed in G39V (87.5%). Sperm proteome reported 1360 proteins with 132 differentially abundant proteins. Of the total, 89 proteins were overexpressed in G39V (67.4%). From the 64 and 132 differentially abundant proteins of plasma and sperm, 19 and 26 had a FC>1.5, 12 and 13 of them belonging to the Oryctolagus cuniculus taxonomy, respectively. Despite observing differences in important proteins related to capacitation, sperm motility or immunoprotection and consequently to the fertilization process (TMPRSS2, Serpin family, Fam71f1, ATPase H+ transporting accessory protein 2, carbonic anhydrase 2, UDP-glucose glycoprotein glucosyltransferase 2), no differences in fertility and prolificacy were detected when commercial seminal doses were used for insemination from both male groups. However, overabundance of KIAA1324 protein can be related to the increase in abnormal sperm after selection by growth rate.

SR-BI Interactome Analysis Reveals a Proviral Role for UGGT1 in Hepatitis C Virus Entry.

Hepatitis C virus (HCV) entry is mediated by multiple co-receptors including scavenger receptor class B, type I (SR-BI). To elucidate the interactome of human SR-BI, we performed immunoprecipitation (IP) experiment coupled with mass spectrometry (MS) analysis. UDP-glucose:glycoprotein glucosyltransferase 1 (UGGT1), a key component of calnexin cycle involved in protein glycosylation, was identified as a SR-BI-interacting protein. Silencing UGGT1 or N-glycosylation inhibitor treatment reduced SR-BI protein level. Further study demonstrated that human SR-BI was N-glycosylated at nine asparagines. Moreover, HCV entry and infection were reduced by the absence of UGGT1. Interestingly, silencing SR-BI reduced protein stability of UGGT1 and protein quality control function mediated by UGGT1. Our finding not only identified UGGT1 as a HCV host factor, but also identified a UGGT1-mediated protein folding function for SR-BI.