OGT: a short overview of an enzyme standing out from usual glycosyltransferases.

-GlcNAcylation is a highly dynamic post-translational modification whose level depends on nutrient status. Only two enzymes regulate -GlcNAcylation cycling, the glycosyltransferase OGT (-GlcNAc transferase) and the glycoside hydrolase OGA (-GlcNAcase), that add and remove the GlcNAc moiety to and from acceptor proteins, respectively. During the last 30 years, OGT has emerged as a master regulator of cell life with -GlcNAcylation being found in viruses, bacteria, insects, protists and metazoans.

Modification by SUMOylation Controls Both the Transcriptional Activity and the Stability of Delta-Lactoferrin.

Delta-lactoferrin is a transcription factor, the expression of which is downregulated or silenced in case of breast cancer. It possesses antitumoral activities and when it is re-introduced in mammary epithelial cancer cell lines, provokes antiproliferative effects. It is posttranslationally modified and our earlier investigations showed that the O-GlcNAcylation/phosphorylation interplay plays a major role in the regulation of both its stability and transcriptional activity.

Detection and identification of O-GlcNAcylated proteins by proteomic approaches.

O-GlcNAcylation (O-linked beta-N-acetylglucosaminylation) is a widespread PTM confined within the nuclear, the cytosolic, and the mitochondrial compartments of eukaryotes. Recently, O-GlcNAcylation has been also detected in the close vicinity of plasma membranes particularly in lipid microdomains. The detection of this PTM can be easily done if appropriate controls and precautions are taken using a wide variety of tools including lectins, antibodies, or click-chemistry-based methods.

SILAC-based proteomic profiling of the human MDA-MB-231 metastatic breast cancer cell line in response to the two antitumoral lactoferrin isoforms: the secreted lactoferrin and the intracellular delta-lactoferrin.

Background: Lactoferrins exhibit antitumoral activities either as a secretory lactoferrin or an intracellular delta-lactoferrin isoform. These activities involve processes such as regulation of the cell cycle and apoptosis. While lactoferrin has been shown to exert its function by activating different transduction pathways, delta-lactoferrin has been proven to act as a transcription factor.

Delta-lactoferrin induces cell death via the mitochondrial death signaling pathway by upregulating bax expression.

Delta-lactoferrin (∆Lf) is a transcription factor belonging to the lactoferrin family, the expression of which inhibits cell proliferation and leads to Skp1 and DcpS gene transactivation. In this study, we showed that ∆Lf expression also induces cell death via apoptosis in HEK 293 and MCF7 cells using a cell viability assay and DNA fragmentation. Western blot analyses showed that apoptosis was caspase-9, 7 and 8 dependent.

Delta-lactoferrin, an intracellular lactoferrin isoform that acts as a transcription factor.

Delta-lactoferrin (ΔLf) is a transcription factor of which the expression is downregulated in cancer. It is a healthy tissue marker and a high expression level of its transcripts was correlated with a good prognosis in breast cancer. ΔLf results from alternative promoter usage of the hLf gene leading to the production of 2 isoforms with alternative N-termini: lactoferrin, which is secreted, and ΔLf, its nucleocytoplasmic counterpart.

O-GlcNAcylation/phosphorylation cycling at Ser10 controls both transcriptional activity and stability of delta-lactoferrin.

Delta-lactoferrin (DeltaLf) is a transcription factor that up-regulates DcpS, Skp1, and Bax genes, provoking cell cycle arrest and apoptosis. It is post-translationally modified either by O-GlcNAc or phosphate, but the effects of the O-GlcNAc/phosphorylation interplay on DeltaLf function are not yet understood. Here, using a series of glycosylation mutants, we showed that Ser(10) is O-GlcNAcylated and that this modification is associated with increased DeltaLf stability, achieved by blocking ubiquitin-dependent proteolysis, demonstrating that O-GlcNAcylation protects against polyubiquitination.

Discrimination and evaluation of lactoferrin and delta-lactoferrin gene expression levels in cancer cells and under inflammatory stimuli using TaqMan real-time PCR.

The lactoferrin gene is known to be expressed either constitutively or under inducible conditions such as hormonal stimuli or inflammation. Its transcription from alternative promoters leads to two products, lactoferrin (Lf) and delta-lactoferrin (DeltaLf) mRNAs the expressions of which are altered during oncogenesis. The comparison of the two enhancer/promoter regions revealed that the two isoforms might be differentially trans-activated.

Construction of a multi-functional helper-dependent adenovirus based system for cancer gene therapy.

Adenovirus holds great promise as a gene delivery system; it can hold large amounts of exogenous DNA and can be chemically and genetically modified to improve targeting to specific cells and tissues. A recombinant adenovirus construct expressing p53 is currently in clinical use as a cancer therapy in China. However, the use of adenovirus constructs in therapy is limited due to patients' strong immune response against these viruses and their gene products.

[Lactoferrin: a multifunctional protein].

Lactoferrin (Lf) is an iron-binding glycoprotein of the transferrin family that is expressed and secreted by glandular cells and found in the secondary granules of neutrophils from which it is released in infected tissues and blood during the inflammatory process. Initially described as an iron-binding molecule with bacteriostatic properties, Lf is now known to be a multifunctional or multi-tasking protein. It is a major component of the innate immune system of mammals.

Proteomic approach to the identification of novel delta-lactoferrin target genes: Characterization of DcpS, an mRNA scavenger decapping enzyme.

The expression of the transcription factor DeltaLf is deregulated in cancer cells. Its overexpression provokes cell cycle arrest along with antiproliferative effects and we recently showed that the Skp1 gene promoter was a target of DeltaLf. Skp1 belongs to the Skp1/Cullin-1/F-box ubiquitin ligase complex responsible for the ubiquitination and the proteosomal degradation of numerous cellular regulators.

Lactoferrin structure and functions.

Lactoferrin (Lf) is an iron binding glycoprotein of the transferrin family that is expressed in most biological fluids and is a major component of mammals' innate immune system. Its protective effect ranges from direct antimicrobial activities against a large panel of microorganisms, including bacteria, viruses, fungi, and parasites, to anti-inflammatory and anticancer activities. This plethora of activities is made possible by mechanisms of action implementing not only the capacity of Lf to bind iron but also interactions of Lf with molecular and cellular components of both host and pathogens.

Human delta-lactoferrin is a transcription factor that enhances Skp1 (S-phase kinase-associated protein) gene expression.

Delta-lactoferrin is a cytoplasmic lactoferrin isoform that can locate to the nucleus, provoking antiproliferative effects and cell cycle arrest in S phase. Using macroarrays, the expression of genes involved in the G(1)/S transition was examined. Among these, Skp1 showed 2-3-fold increased expression at both the mRNA and protein levels.

Expression and prognostic value of lactoferrin mRNA isoforms in human breast cancer.

We investigated the expression levels of human lactoferrin (Lf), a steroid hormone-inducible gene product the expression of which is often altered during oncogenesis, and of Delta-lactoferrin (DeltaLf), its alternative isoform, which has been shown to be absent from tumor cell lines in commonly used human breast epithelial cell lines, using semiquantitative RT-PCR. Both mRNAs were detected but with levels of expression lower than those found in normal breast epithelial cells. This downregulation was much more visible for DeltaLf since its expression was either significantly diminished (BT-20, MCF-7 cell lines) or practically absent (MDA-MB-231, T-47D, HBL 100 cell lines).