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Nicole Zitzmann

Publications and source records attributed to Nicole Zitzmann.

26 records · Page 2Linked to original sources
PubMed2003

Differential proteome analysis of TRAP-activated platelets: involvement of DOK-2 and phosphorylation of RGS proteins.

We have applied a proteomics approach to analyze signaling cascades in human platelets stimulated by thrombin receptor activating peptide (TRAP). By analyzing basal and TRAP-activated platelets using 2-dimensional gel electrophoresis (2-DE), we detected 62 differentially regulated protein features. From these, 41 could be identified by liquid chromatography-coupled tandem mass spectrometry (LC-MS/MS) and were found to derive from 31 different genes, 8 of which had not previously been reported in platelets, including the adapter downstream of tyrosine kinase 2 (Dok-2). Further studies revealed that the change in mobility of Dok-2 was brought about by tyrosine phosphorylation. Dok-2 tyrosine phosphorylation was also found to be involved in collagen receptor, glycoprotein VI (GPVI), signaling as well as in outside-in signaling through the major platelet integrin, alpha IIIb beta 3. These studies also provided the first demonstration of posttranslational modification of 2 regulator of G protein signaling (RGS) proteins, RGS10 and 18. Phosphorylation of RGS18 was mapped to Ser49 by MS/MS analysis. This study provides a new approach for the identification of novel signaling molecules in activated platelets, providing new insights into the mechanisms of platelet activation and building the basis for the development of therapeutic agents for thrombotic diseases.

Adaptor Proteins, Signal Transducing↗
PubMed2003

The pestivirus E(rns) glycoprotein interacts with E2 in both infected cells and mature virions.

E(rns) is a pestivirus envelope glycoprotein indispensable for virus attachment and infection of target cells. Unlike the other two envelope proteins E1 and E2, E(rns) lacks a transmembrane domain and a vast quantity is secreted into the medium of infected cells. The protein is also present in fractions of pure pestivirus virions, raising the important and intriguing question regarding the mechanism of its attachment to the pestivirus envelope. In this study a direct interaction between E(rns) and E2 glycoproteins was demonstrated in both pestivirus-infected cells and mature virions. By co- and sequential immunoprecipitation we showed that an E(rns)-E2 heterodimer is assembled very early after translation of the viral polyprotein and before its processing is completed. Our results suggest that E(rns) is attached to the pestivirus envelope via a direct interaction with E2 and explain the role of E(rns) in the initial virus-target cell interaction.

Animals↗
PubMed2002

Role of disulfide bond formation in the folding and assembly of the envelope glycoproteins of a pestivirus.

Bovine viral diarrhea virus (BVDV) is a pestivirus member of the Flaviviridae family, closely related to, and used as a surrogate model for the hepatitis C virus. Its envelope contains the E1 and E2 glycoproteins, disulfide linked into homo- and heterodimers. In this study, we investigate the role of disulfide bond formation in the folding, assembly, and stability of BVDV glycoproteins. We provide molecular evidence that intact disulfide bonds are critical for the acquirement of a stable conformation of E2 monomers. Forcing the E2 glycoproteins to adopt a reduced conformation either co- or post-translationally before assembly into dimers, determines their misfolding and degradation by proteasome. In contrast, dimerization of E2 glycoproteins results in a conformation resistant to reducing agents and degradation. Furthermore, inhibition of the ER-alpha-mannosidase activity leads to impairment of misfolded E2 degradation, demonstrating the involvement of this enzyme in targeting viral proteins towards proteasomal degradation.

Animals↗
PubMed2002

Targeting glycosylation as a therapeutic approach.

Increased understanding of the role of protein- and lipid-linked carbohydrates in a wide range of biological processes has led to interest in drugs that target the enzymes involved in glycosylation. But given the importance of carbohydrates in fundamental cellular processes such as protein folding, therapeutic strategies that modulate, rather than ablate, the activity of enzymes involved in glycosylation are likely to be a necessity. Two such approaches that use imino sugars to affect glycosylation enzymes now show considerable promise in the treatment of viral infections, such as hepatitis B, and glucosphingolipid storage disorders, such as Gaucher disease.

Animals↗
PubMed2002

Antiviral effects of an iminosugar derivative on flavivirus infections.

Endoplasmic reticulum (ER) alpha-glucosidase inhibitors, which block the trimming step of N-linked glycosylation, have been shown to eliminate the production of several ER-budding viruses. Here we investigated the effects of one such inhibitor, N-nonyl-deoxynojirimycin (NN-DNJ), a 9-carbon alkyl iminosugar derivative, on infection by Japanese encephalitis virus (JEV) and dengue virus serotype 2 (DEN-2). In the presence of NN-DNJ, JEV and DEN-2 infections were suppressed in a dose-dependent manner. This inhibitory effect appeared to influence DEN-2 infection more than JEV infection, since lower concentrations of NN-DNJ substantially blocked DEN-2 replication. Secretion of the flaviviral glycoproteins E and NS1 was greatly reduced, and levels of DEN-2 viral RNA replication measured by fluorogenic reverse transcription-PCR were also decreased, by NN-DNJ. Notably, the viral glycoproteins, prM, E, and NS1 were found to associate transiently with the ER chaperone calnexin, and this interaction was affected by NN-DNJ, suggesting a potential role of calnexin in the folding of flaviviral glycoproteins. Additionally, in a mouse model of lethal challenge by JEV infection, oral delivery of NN-DNJ reduced the mortality rate. These findings show that NN-DNJ has an antiviral effect on flavivirus infection, likely through interference with virus replication at the posttranslational modification level, occurring mainly in the ER.

1-Deoxynojirimycin↗
PubMedDate not supplied

Applying proteomics technology to platelet research.

Platelets are small enucleated cells that circulate in the blood, where they play a key role in hemostasis and contribute to the formation of vascular plugs. Pathologically, they are involved in thrombosis and heart disease. Because platelets do not have a nucleus, proteomics offers a powerful way to approach their biology. Proteomics technology is based on the huge analytical power offered by mass spectrometry in combination with several separation techniques, such as two-dimensional gel electrophoresis (2DGE) or multidimensional liquid chromatography. Proteomics provides information about the complete set of proteins present in platelets, the platelet proteome, including post-translational variants. Over the last years, several research groups have applied proteomics to platelet research. A detailed analysis of the general proteome and signaling cascades in human platelets will improve our knowledge of platelet function, and thereby aid the development of new therapeutic agents to treat thrombotic diseases. This review presents the major advances in mass spectrometry-based proteomics techniques and their application to platelet research, and analyzes in detail the most relevant contributions to the field.

Biotechnology↗