Elevated O-GlcNAcylation of Extracellular Vesicle Proteins Derived from Metastatic Colorectal Cancer Cells.

BACKGROUND: O-GlcNAcylation is a single sugar attachment of serine and/or threonine residues on intracellular proteins. Recent reports reveal that it can modify several secretory proteins; however, the underlying mechanisms are largely unexplored. MATERIALS AND METHODS: To investigate whether extracellular vesicles (EVs) carry secretory O-GlcNAc-modified proteins that were isolated from colorectal cancer (CRC) cells, two-dimensional gel electrophoresis followed with O-GlcNAc immunoblotting and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were applied. RESULTS: It was revealed that the O-GlcNAc modification of many EV proteins was increased in metastatic cells. Among these, transitional endoplasmic reticulum ATPase (TER ATPase) and RuVB-like1 were successfully confirmed for the O-GlcNAc modification in which the levels were significantly higher in EVs of metastatic CRC cell line. CONCLUSION: These data, demonstrate that proteins carried by EVs are O-GlcNAc-modified. Importantly, elevated aberrant O-GlcNAcylation of EV proteins might serve as a potential biomarker of metastatic CRC.

Identification of Palmitoylated Transitional Endoplasmic Reticulum ATPase by Proteomic Technique and Pan Antipalmitoylation Antibody.

Protein palmitoylation plays a significant role in a wide range of biological processes such as cell signal transduction, metabolism, apoptosis, and carcinogenesis. For high-throughput analysis of protein palmitoylation, approaches based on the acyl-biotin exchange or metabolic labeling of azide/alkynyl-palmitate analogs are commonly used. No palmitoylation antibody has been reported. Here, the palmitoylated proteome of human colon cancer cell lines SW480 was analyzed via a TS-6B-based method. In total, 151 putative palmitoylated sites on 92 proteins, including 100 novel sites, were identified. Except for 3 known palmitoylated transmembrane proteins, ATP1A1, ZDHHC5, and PLP2, some important proteins including kinases, ion channels, receptors, and cytoskeletal proteins were also identified, such as CLIC1, PGK1, PPIA, FKBP4, exportin-2, etc. More importantly, the pan antipalmitoylation antibody was developed and verified for the first time. Our homemade pan antipalmitoylation antiserum could differentiate well protein palmitoylation from mouse brain membrane fraction and SW480 cells, which affords a new technique for analyzing protein palmitoylation by detecting the palmitic acid moiety directly. Furthermore, the candidate protein transitional endoplasmic reticulum ATPase (VCP) identified in SW480 cells was validated to be palmitoylated by Western blotting with anti-VCP antibody and the homemade pan antipalmitoylation antibody.

Target antigens for Hs-14 monoclonal antibody and their various expression in normozoospermic and asthenozoospermic men.

BACKGROUND: Poor semen quality is one of the main causes of infertility. We have generated a set of monoclonal antibodies to human sperm and used them to investigate sperm quality. Some of these antibodies found differences in the expression of proteins between normal sperm and pathological sperm displaying severe defects. One of them was the Hs-14 antibody. The aim of this paper was to determine the target protein of the Hs-14 monoclonal antibody and to investigate the expression of the Hs-14-reacting protein on the sperm of asthenozoospermic men with sperm motility defect and of healthy normozoospermic men. METHODS: Indirect immunofluorescence, one-dimensional and two-dimensional polyacrylamide gel electrophoresis, immunoblotting and mass spectrometry. RESULTS: The Hs-14 antibody binds fibronectin, ß-tubulin and valosin-containing protein - new name for this protein is transitional endoplasmic reticulum ATPase (TERA). Since the Hs-14 reaction with TERA remained the strongest at the highest antibody dilution, and Hs-14 consistently labelled the same spot or band as the monospecific anti-TERA antibody on immunoblots, we assume that TERA is an Hs-14-specific protein. Binding of fibronectin and ß-tubulin might represent nonspecific cross-reactivity or Hs-14 reaction with similar epitopes of these proteins. A significant difference (P < 0.001) in immunofluorescence staining with Hs-14 was found between the normozoospermic and asthenozoospermic men. CONCLUSION: The Hs-14 antibody enables discrimination between sterile or subfertile asthenozoospermic and fertile normozoospermic men. Decreased levels of TERA in men can be used as a biomarker of reduced fertility.

INTRODUCTION: La pauvre qualité de la semence est l'une des causes d'infertilité. Nous avons généré une série d'anticorps monoclonaux contre le sperme humain et nous l'avons utilisée pour examiner la qualité du sperme. Certains de ces anticorps ont montré des différences d' expression des protéines entre le sperme normal et le sperme pathologique qui a des défauts sévères. L'un d'eux a été l'anticorps Hs-14. Le but de cet article était de déterminer la protéine cible de l'anticorps monoclonal Hs-14 et d'établir l'expression de la protéine réagissant avec Hs-14 sur le sperme des hommes asthénozoospermiques qui ont des défauts de la mobilité du sperme et sur celui des hommes normozoospermiques. MÉTHODES: Immunofluorescence indirecte, electrophorèse sur gel polyacrylamide à une ou deux dimensions, immunoblotting et spectrométrie de masse. RÉSULTATS: L'anticorps Hs-14 s'attache à la fibronectine, à la ß-tubuline et à la protéine TERA (ATPase transitoire de réticulum endoplasmique). Etant donné que la réaction du Hs-14 avec TERA a été la plus forte à la dilution la plus grande de l'anticorps, et que Hs-14 marquait systématiquement la même tache ou bande que l'anticorps mono-spécifique anti-TERA sur les immunoblots, nous supposons que TERA est une protéine spécifique pour Hs-14. L'attachement à la fibronectine et à la ß-tubuline pourrait représenter une réaction croisée non spécifique ou la réaction du Hs-14 avec des épitopes similaires de ces protéines. Une différence significative (P < 0.001) en immunofluorescence avec Hs-14 a été révélée entre hommes normozoospermiques et asthénozoospermiques. CONCLUSIONS: L'anticorps Hs-14 permet de différencier les hommes stériles ou subfertiles asthénozoospermiques des hommes fertiles normozoospermiques. Les niveaux de la TERA chez les hommes pourraient être utilisés comme un marqueur biologique d'une fertilité réduite.

Proteomic Analysis Reveals Aberrant O-GlcNAcylation of Extracellular Proteins from Breast Cancer Cell Secretion.

BACKGROUND: O-GlcNAcylation is a unique intracellular protein modification; however, few extracellular O-GlcNAc-modified proteins have been discovered. We have previously demonstrated that many cellular proteins were aberrant in O-GlcNAcylation in breast cancer tissues. In the present study, therefore, we investigated whether O-GlcNAc-modified proteins were abnormally secreted from breast cancer cells. MATERIALS AND METHODS: Intracellular and extracellular proteins were prepared from cell lysates of breast cancer cells (MCF-7 and MDA-MB-231) and normal breast cells (HMEC) and from their serum-free media (SFM), respectively. O-GlcNAcylation level was examined by immunoblotting. O-GlcNAc-Modified proteins were identified using two-dimensional gel electrophoresis and Liquid Chromatography-tandem Mass Spectrometry. RESULTS: O-GlcNAcylation level was significantly increased in the extracellular compartment of both types of cancer cells compared to normal cells. Interestingly, O-GlcNAc patterns differed between intracellular and extracellular proteins. Proteomic analysis revealed that many O-GlcNAc spots in MCF-7 secretions were abnormally increased in comparison to those in HMEC secretions. Among these, transitional endoplasmic reticulum ATPase (TER ATPase) and heat-shock 70 kDa (HSP70) were confirmed to be O-GlcNAc-modified. The levels of O-GlcNAc-HSP70 and O-GlcNAc-TER ATPase were higher in SFM from MCF-7 cells than in that from HMEC. CONCLUSION: O-GlcNAcomic study of the extracellular compartments reveals aberrant O-GlcNAc-secreted proteins, which may be of interest as potential biomarkers in breast cancer.

Comparative analysis of Leishmania exoproteomes: implication for host-pathogen interactions.

Leishmaniasis is a vector-borne disease caused by the protozoa Leishmania. We have analyzed and compared the sequences of three experimental exoproteomes of Leishmania promastigotes from different species to determine their specific features and to identify new candidate proteins involved in interactions of Leishmania with the host. The exoproteomes differ from the proteomes by a decrease in the average molecular weight per protein, in disordered amino acid residues and in basic proteins. The exoproteome of the visceral species is significantly enriched in sites predicted to be phosphorylated as well as in features frequently associated with molecular interactions (intrinsic disorder, number of disordered binding regions per protein, interaction and/or trafficking motifs) compared to the other species. The visceral species might thus have a larger interaction repertoire with the host than the other species. Less than 10% of the exoproteomes contain heparin-binding and RGD sequences, and ~30% the host targeting signal RXLXE/D/Q. These latter proteins might thus be exported inside the host cell during the intracellular stage of the infection. Furthermore we have identified nine protein families conserved in the three exoproteomes with specific combinations of Pfam domains and selected eleven proteins containing at least three interaction and/or trafficking motifs including two splicing factors, phosphomannomutase, 2,3-bisphosphoglycerate-independent phosphoglycerate mutase, the paraflagellar rod protein-1D and a putative helicase. Their role in host-Leishmania interactions warrants further investigation but the putative ATP-dependent DEAD/H RNA helicase, which contains numerous interaction motifs, a host targeting signal and two disordered regions, is a very promising candidate.