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GALIG gene expression induces apoptosis in cultured cells through a pathway still under investigation. It is highly expressed in leukocytes but weakly detectable in bone marrow, suggesting a role in the myeloid lineage homeostasis. We show here that GALIG-induced cell death is counteracted by the overexpression of MCL-1, a pro-survival member of the Bcl2 family. Moreover, during spontaneous neutrophil apoptosis, a substantial increase in GALIG gene expression is observed : GALIG still opposes MCL-1. Finally, in bone marrow and peripheral blood cells from patients with Acute Myeloid Leukemia type 2, the level of GALIG transcripts is massively down-regulated when compared to their normal counterparts, while MCL-1 is expressed to the same extent. These data suggest that GALIG could be a key player in the cell death pathway involved in leukocytes homeostasis and myeloid malignancies.
Mitogaligin is a mitochondrion-targeting protein involved in cell death. The sequence of the protein is unrelated to that of any known pro- or antiapoptotic protein. Mitochondrial targeting is controlled by an internal sequence from residues 31 to 53, and although this sequence is essential and sufficient to provoke cell death, the precise mechanism of action at the mitochondrial membrane remains to be elucidated. Here, by focusing on the [31–53] fragment, we first assessed and confirmed its cell cytotoxicity by microinjection. Subsequently, with the aid of membrane models, we evaluated the impact of the membrane environment on the 3D structure of the peptide and on how the peptide is embedded and oriented within membranes. The fragment is well organized, even though it does not contain a canonical secondary structure, and adopts an interfacial location. Structural comparison with other membrane-interacting Trp-rich peptides demonstrated similarities with the antimicrobial peptide tritrpcidin.
Galig, a gene embedded within the galectin-3 gene, induces cell death when transfected in human cells. This death is associated with cell shrinkage, nuclei condensation, and aggregation of mitochondria. Galig contains two different overlapping open reading frames encoding two unrelated proteins. Previous observations have shown that one of these proteins, named mitogaligin, binds to mitochondria and promotes the release of cytochrome c. However, the mechanism of action of this cytotoxic protein remains still obscure.
Galectin-3 internal gene (Galig) was recently identified as an internal gene transcribed from the second intron of the human galectin-3 gene that is implicated in cell growth, cell differentiation, and cancer development. In this study, we show that galig expression causes morphological alterations in human cells, such as cell shrinkage, cytoplasm vacuolization, nuclei condensation, and ultimately cell death. These alterations were associated with extramitochondrial release of cytochrome c, a known cell death effector.
We previously reported that alternative transcripts were initiated within the second intron of the human Galectin-3 gene (LGALS3), We now demonstrate that these transcripts arise from an internal gene embedded within LGALS3 and named galig (Galectin-3 internal gene). Tissue-specific expression of galig was assayed by screening of several human tissues. Contrary to LGALS3, galig appears to be tightly regulated and principally activated in leukocytes from peripheral blood. Cloning and characterization of galig transcripts revealed that they contain two out-of-frame overlapping open-reading frames (ORFs). Transfection of expression vectors encoding enhanced green fluorescent protein (EGFP) chimeras indicated that both ORFs could be translated in proteins unrelated to Galectin-3. The ORF1 polypeptide targets EGFP to cytosol and nucleus whereas ORF2 targets EGFP to mitochondria. These results revealed the exceptional genetic organization of the LGALS3 locus.
MR60 is an intracellular membrane protein which has been shown to act as a mannoside specific lectin and to be identical to ERGIC-53, a protein characteristic of the endoplasmic reticulum-Golgi apparatus-intermediate compartment, acting as a shuttle. According to its primary sequence, this MR60/ERGIC-53 protein contains a luminal domain including the carbohydrate recognition domain, a stem, a transmembrane segment and a cytosolic domain. The endogenous MR60/ERGIC-53 protein is spontaneously oligomeric, (dimers and hexamers), In this paper, we study the relationship between the oligomerization state and the sugar binding capacity by using recombinant proteins.
Animal lectins play important roles in a variety of biological processes via their recognition of glycoconjugates. Galectin-3 is a ß-galactoside-binding lectin whose expression is associated with various pathological processes including human T lymphotropic virus (HTLV)-I-infection of human T cell lines and human immunodeficiency virus (HIV) infection of T-lymphoblastic Molt-3 cell line. In the case of HIV-infected cells, it has been suggested that the increase in galectin-3 expression could be related to the expression of the viral regulatory gene tat. These results prompt us to perform more extensive analyses of the relationship between galectin-3 and HIV-1 Tat expressions. In this study, we found that Tat protein expression induces an upregulation of galectin-3 in several human cell lines. In cotransfection experiments, the 5’-regulatory sequences of the galectin-3 gene were significantly upregulated by expression vectors encoding the Tat protein. Analysis performed with 5’-regulatory deleted sequences suggested that galectin-3 induction by Tat is dependent on activation of the Sp-1 binding transcription factor.
Glycofection (transfection by using sugar-substituted polylysine) was assessed in order to provide an alternative to viral vectors for the transfer of genes into vascular smooth muscle cells, A rabbit vascular smooth muscle cell line (Rb-l cells) was selectively transfected by using glycoplexes (glycosylated polylysine/pSV2LUC complexes) in the presence of 10 mu M of the fusogenic peptide GALA, A sugar-specific transfection was obtained when the glycofection was conducted for 1 h with glycoplexes containing either a-Gal, a-Glc, a-GalNAc, ß-GlcNAc, or ß-GalNAc residues.
The galectin-3 gene (LGALS3) encodes a ß-galactose binding lectin. LGALS3 expression is associated with neoplastic transformation and,vith differentiation of monocytes to macrophages. Factors involved in migration, proliferation, adhesion and differentiation of vascular smooth muscle cells (SMC) play a major role during atherosclerosis development, Expression of the galectin-3 gene was not detected in quiescent SMC but was activated in aortas of hypercholesterolemic rabbits, in aortas of rats after balloon injury and in cultured SMC. These results suggest that galectin-3 production is involved in the developmental process of atherogenesis. (C) 1998 Federation of European Biochemical Societies.
Analysis of cellular DNA insert isolated from a free replicative plasmid rescued from human cells transformed with an SV40 vector plasmid revealed the presence of two arrays of repetitive DNA arranged in tandem. One sequence was homologous to the consensus sequence of the human a satellite DNA and the adjoining sequence was a satellite DNA sequence which consisted of repetitive units of 42 base pairs (bp) and was designated HR42. The degree of homology between repetitive units was about 92%. By Southern analysis the HR42 sequence was detected in HHW416, a somatic cell hybrid containing human chromosome 4, but not in HDm-5, the somatic cell hybrid which has human chromosome 14. By fluorescence in situ hybridization this repetitive DNA was assigned uniquely to the centromeric region of human chromosome 4. These results show that HR42 belongs to a subfamily of satellite I DNA specific for human chromosome 4.
Galectin-3 is a galactose-binding lectin that has been found in several mammalian tissues, Galectin-3 gene is expressed in a wide range of normal and tumoral cells, In the case of myeloid cells, its expression correlates with the differentiation of monocytes to macrophages. In the case of cancer cell lines, its expression correlates with tumorigenicity and metastatic potential, The regulation of the expression of this gene is still largely unknown, The rabbit galectin-3 gene has been isolated and characterized, Its structure revealed an organization similar to that of the murine galectin-3 gene.
The association of human cytomegalovirus with atherosclerosis and the monoclonal hypothesis of atherogenesis suggested that transformation of vascular smooth muscle cells may be an outcome of the virus-host cell interaction, To test this hypothesis, rabbit aorta smooth muscle cells were transfected with the morphological transforming region I (mtrI) of human. cytomegalovirus (HCMV) linked to the neomycin resistance gene. Foci of neomycin-resistant and morphologically transformed cells were isolated and expanded into fourteen RCMV strains, Eight of these strains acquired immortalization, but only one strain (RCMV-21) retained recombined viral sequences integrated in the cellular DNA. RCMV strains were heterogeneous in their morphology, expression of smooth muscle cy-actin, growth, and mitogenic response to serum and fibroblast growth factor (FGF)-2 and -4.
Astrocytes are the principal sites of glycogen synthesis in the nervous tissue. Growing evidence shows that there are many types of astrocytes. The aim of the present investigation was to isolate different types of astrocytes that display different carbohydrate anabolism. Astrocytes from newborn rat brain were directly cloned from primary cultures without a previous transformation. Many clones were obtained, and they were termed CP clones. Another series of clones, termed SV clones, were obtained after the transfection of the primary cultures by the SV40 T antigen.
A mannose specific membrane lectin (MR60) isolated from human myelomonocytic HL60 cells by affinity chromatography is expressed in intracellular organelles of immature monocytes (Pimpaneau, V., Midoux, P., Monsigny, M., and Roche, A. C. (1991) Carbohydr. Res. 213, 95-108). It is not present at the cell surface and is immunochemically and structurally distinct from the M(r) 175,000 mannose receptor of mature macrophages. MR60 cDNA was isolated and characterized ; on the basis of its sequence, MR60 is not related to any known mammalian lectins.
Mannose receptor is a differentiation marker of macrophages. Circulating monocytes isolated from plasma are devoid of this receptor ; upon culture this receptor is rapidly expressed. Its expression is modulated by a variety of inflammatory and antiinflammatory agents. In the present study, we investigated its transcription level during the differentiation process. Mannose receptor mRNA was monitored by quantitative RT-PCR on freshly harvested monocytes and on monocytes cultivated up to four days. No transcription was detected in freshly harvested cells, the transcription increased during the first 24 h upon adhesion and then decreased. (C) 1995 Academic Press, Inc.
Galectin-3 is a galactose-specific lectin which has been shown to be involved in several biological functions such as cell growth regulation, cell aggregation and cell differentiation. The partial cloning of the human genomic sequences reveals the presence of a 651 bp intron, 18 bp downstream of the translation initiation site, This intron contains several regulatory elements found in many eukaryotic genes, This sequence, when inserted upstream of a promoter-free luciferase gene, induces the expression of luciferase, demonstrating the promoter activity of the intron upon transfection in human or murine cells, This promoter activity is down-modulated by wild-type p53 but not by a mutated form of p53.
The complete coding sequence of the rabbit galactin-3-encoding cDNA (LGALS3) has been cloned in a single step by using RT-PCR and specific human LGALS3 cDNA primers. The putative protein contains three domains with different degrees of homology to other known LGALS3. The homology is high in the C-terminal moiety corresponding to the carbohydrate-binding domain and is relatively low in the N-terminal moiety.
We have cloned the putative promoter of the human mannose receptor gene using the ligation-mediated polymerase chain reaction. This modified polymerase chain reaction method depends upon the ligation of restricted genomic DNA fragments to a sequence of DNA containing a generic primer site. Approximately 400 bp of genomic DNA sequence immediately upstream from the 5’ end of the lectin gene was amplified with this strategy. Primer-extended reverse transcription identified several 5’ ends of the mannose receptor mRNA corresponding to differential use of initiation transcription sites.
Endothelial cells from mouse peripheral lymph nodes were immortalized by cationic liposome-mediated transfection using a plasmid construct containing both the gene coding for the large T antigen of simian virus 40 and a geneticin resistance gene suitable for selection. A cell line (HECa10) was isolated on the basis of its capacity to specifically bind fucoside carrying glycoconjugates ; these cells present the main characteristics of endothelial cells : production of angiotensin converting enzyme and of factor VIII-related antigen.
We have developed a vector that allows high and transactivable expression of inserted genes. The vector contains a transcription unit in which the LTR from HN flanks a multicloning site. The plasmid is based on the EBV p205 plasmid, which allows stable replication in human cells. The ability of the vector to express an exogenous DNA in human cells has been tested using the firefly luciferase gene. (C) 1994 Academic Press. Inc.
Plasmid DNA/glycosylated polylysine complexes were used to transfer in vitro a luciferase reporter gene into human hepatoma cells by a receptor-mediated endocytosis process. HepG2 cells which express a galactose specific membrane lectin were efficiently and selectively transfected with pSV2Luc/lactosylated polylysine complexes in a sugar dependent manner : i) HepG2 cells which do not express membrane lectin specific for mannose were quite poorly transfected with pSV2Luc/mannosylated polylysine complexes, ii) HeLa cells which do not express membrane lectin specific for galactose were not transfected with pSV2Luc/lactosylated polylysine complexes.
The plasmid pSV3-neo that carries the SV40 early genetic region and the neo(r) resistance gene underwent homologous recombination between SV40-duplicated sequences of the small t antigen intron and the polyadenylation site after transfection into rabbit vascular smooth muscle cells. This recombination yielded two free plasmids of 1.7 and 3.0 kb that replicated in transfected rabbit cells, while the vector plasmid did not. Replication of the two recombinant plasmids continued for several months in rabbit cells transformed by pSV3-neo, and their structure remained unchanged. Between 15 and 2,510 copies per cell of the 3.0-kb plasmid and between 370 and 1,565 copies per cell of the 1.7-kb plasmid were found in different pSV3-neo-transformed rabbit clones.
Human arterial smooth muscle cells transfected with the plasmid pSV3-neo, which contains the SV40 virus early region and the neo(r) gene, developed colonies of morphologically transformed cells. Five cell strains were initiated from these colonies and could be subcultivated for up to 9 months before entering a stage of crisis that ended their life span. Deoxyribonucleic acid (DNA) molecules containing viral sequences were found free and integrated in the transformed cells. The intranuclear SV40 large T antigen and the p53 cellular protein were expressed in the transformed cells.
Professeur , Responsable de groupe thématique , Mort cellulaire programmée