Sequence and expression of the monkey homologue of the ER-golgi intermediate compartment lectin, ERGIC-53

Identification and characterization of an L-type lectin from obscure puffer Takifugu obscurus in response to bacterial infection

L-type lectins (LTLs) contain a carbohydrate recognition domain homologous to leguminous lectins, and have functions in selective protein trafficking, sorting and targeting in the secretory pathway of animals. In this study, a novel LTL, designated as ToERGIC-53, was cloned and identified from obscure puffer Takifugu obscurus. The open reading frame of ToERGIC-53 contained 1554 nucleotides encoding 517 amino acid residues. The deduced ToERGIC-53 protein consisted of a signal peptide, a leguminous lectin domain (LTLD), a coiled-coil region, and a transmembrane region. Quantitative real-time PCR showed that ToERGIC-53 was expressed in all examined tissues, with the highest expression level in the liver. The expression of ToERGIC-53 was significantly upregulated after infection with Vibrio harveyi and Staphylococcus aureus. Recombinant ToERGIC-53-LTLD (rToERGIC-53-LTLD) protein could not only agglutinate and bind to one Gram-positive bacterium (S. aureus) and three Gram-negative bacteria (V. harveyi, V. parahaemolyticus and Aeromonas hydrophila), but also bind to glycoconjugates on the surface of bacteria such as lipopolysaccharide, peptidoglycan, mannose and galactose. In addition, rToERGIC-53-LTLD inhibited the growth of bacteria in vitro. All these results suggested that ToERGIC-53 might be a pattern recognition receptor involved in antibacterial immune response of T. obscurus.

Characterisation and functional analysis of an L-type lectin from the swimming crab Portunus trituberculatus

L-type lectins are involved in glycoprotein secretion and are associated with immune responses. Herein, an L-type lectin was identified in swimming crab (Portunus trituberculatus). The 1347 bp PtLTL cDNA includes a 26 bp 5'-untranslated region (UTR), a 547 bp 3'-UTR with a poly(A) tail, and a 774 bp open reading frame encoding a 257 amino acid protein with a putative 21 residue signalling peptide. The protein includes an L-type lectin carbohydrate recognition domain containing four conserved cysteines. The 714 bp cDNA fragment encoding the mature peptide of PtLTL1 was recombined into pET-21a (+) with a C-terminally hexa-histidine tag fused in-frame and expressed in Escherichia coli Origami (DE3). Recombinant PtLTL1 caused agglutination of all three Gram-positive and Gram-negative bacterial strains tested. In addition, erythrocyte agglutination and LPS-binding activity were observed. PtLTL1 mRNA transcripts were most abundant in P. trituberculatus hepatopancreas and hemocytes, and expression was up-regulated in hemocytes challenged with Vibrio alginolyticus, suggesting PtLTL functions in the immune response against bacterial pathogens.

Cloning and characterization of two different L-type lectin genes from the Chinese mitten crab Eriocheir sinensis

L-type lectins contain a leguminous lectin domain and bind to high-mannose type oligosaccharides. In the secretory pathway, L-type lectins play crucial functions in the trafficking, sorting, and targeting of maturing glycoproteins. This study identified two novel L-type lectins, designated as EsERGIC-53 and EsVIP36, from the Chinese mitten crab Eriocheir sinensis. The complete nucleotide sequence of ERGIC-53 cDNA was 1955 bp, containing a 1506 bp open reading frame (ORF) encoding a putative protein of 501 deduced amino acids. The full-length cDNA of VIP36 was 3474 bp with a 984 bp ORF encoding a 327-amino acid peptide. The deduced ERGIC-53 and VIP36 proteins contained a putative signal peptide and an L-type lectin-like domain. Phylogenetic analysis showed that ERGIC-53 and VIP36 belonged to different clades of L-type lectin family. Reverse transcription PCR showed that ERGIC-53 and VIP36 were expressed in all tested tissues. Quantitative real-time RT-PCR analysis revealed that ERGIC-53 and VIP36 transcripts in hepatopancreas were significantly induced at various time points after infection with lipopolysaccharide (LPS), peptidoglycan (PGN), Staphylococcus aureus, Vibrio parahaemolyticus, and Aeromonas hydrophila. A bacterium-binding experiment showed that both ERGIC-53 and VIP36 could bind to different microbes. Sugar binding assay revealed that these lectins could also bind to the glycoconjugates of bacteria surface, such as LPS, PGN, d-Mannose, and N-Acetyl-d-mannosamine. Moreover, these two L-type lectins agglutinated bacteria in a calcium-dependent manner, and both exerted the ability of facilitating the clearance of injected bacteria V. parahaemolyticus in the crab. Our results suggested that ERGIC-53 and VIP36 functioned as pattern recognition receptors in the immune system of E. sinensis.

Molecular characterization of three L-type lectin genes from channel catfish, Ictalurus punctatus and their responses to Edwardsiella ictaluri challenge

L-type lectins have a leguminous lectin domain and can bind to high-mannose type oligosaccharides. In the secretory pathway, L-type lectins play crucial roles in selective protein trafficking, sorting and targeting. Three L-type lectins were cloned in the channel catfish, Ictalurus punctatus, the 53 kDa endoplasmic reticulum ER-Golgi intermediate compartment protein (ERGIC-53), the vesicular integral protein of 36 kDa (VIP36) and VIP36-like. Phylogenetic analysis indicated that the catfish genes are orthologous to their counterparts in other species. Southern blot analysis demonstrated that all three L-type lectin genes are likely single-copy genes in the catfish genome. Analysis of expression in healthy tissues using quantitative real time RT-PCR indicated that all three genes are expressed widely in all tested tissues, but with strong tissue preference of expression: ERGIC-53 was found to be abundantly expressed in the liver, VIP36 was found to be abundantly expressed in the head-kidney, whereas VIP36-like was found to be abundantly expressed in the brain. Upon infection with Edwardsiella ictaluri, expressions of the three genes all had significant up-regulation in the head-kidney, but had distinct expression patterns: ERGIC-53 was gradually induced with the highest expression 7 days after challenge in the head-kidney, but was down-regulated in the liver, spleen, and brain. VIP36 was highly induced in the head-kidney, and 3 days after challenge in the brain, but was not up-regulated in any other tissues or timepoints after challenge. Expression levels of the catfish VIP36-like gene appeared to also respond to infection, albeit with differing patterns among the tested tissues. Taken together, our results indicate that all three L-type lectin genes may be involved in the immune responses of catfish after infection with E. ictaluri.

Heat Shock Induces Preferential Translation of ERGIC-53 and Affects Its Recycling Pathway

ERGIC-53 is a lectin-like transport receptor protein, which recirculates between the ER and the Golgi complex and is required for the intracellular transport of a restricted number of glycoproteins. We show in this article that ERGIC-53 accumulates during the heat shock response. However, at variance with the unfolded protein response, which results in enhanced transcription of ERGIC-53 mRNA, heat shock leads only to enhanced translation of ERGIC-53 mRNA. In addition, the half-life of the protein does not change during heat shock. Therefore, distinct signal pathways of the cell stress response modulate the ERGIC-53 protein level. Heat shock also affects the recycling pathway of ERGIC-53. The protein rapidly redistributes in a more peripheral area of the cell, in a vesicular compartment that has a lighter sedimentation density on sucrose gradient in comparison to the compartment that contains the majority of ERGIC-53 at 37 degrees C. This effect is specific, as no apparent reorganization of the endoplasmic reticulum, intermediate compartment and Golgi complex is morphologically detectable in the cells exposed to heat shock. Moreover, the anterograde transport of two unrelated reporter proteins is not affected. Interestingly, MCFD2, which interacts with ERGIC-53 to form a complex required for the ER-to-Golgi transport of specific proteins, is regulated similarly to ERGIC-53 in response to cell stress. These results support the view that ERGIC-53 alone, or in association with MCFD2, plays important functions during cellular response to stress conditions.