In vitro effect of TNF-alpha and IFN-gamma in retinal cell infection with Toxoplasma gondii.

Purpose: Toxoplasma gondii is an intracellular protozoan parasite and the most common cause of infectious uveitis. This study was conducted to evaluate the in vitro effect of tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma in rat retinal cells infected with T. gondii.

Characterization and role of protozoan parasite proteasomes.

The proteasome, a large non-lysosomal multi-subunit protease complex, is ubiquitous in eukaryotic cells. In protozoan parasites, the proteasome is involved in cell differentiation and replication, and could therefore be a promising therapeutic target. This article reviews the present knowledge of proteasomes in protozoan parasites of medical importance such as Giardia, Entamoeba, Leishmania, Trypanosoma, Plasmodium and Toxoplasma spp.

In vitro effects of gliotoxin, a natural proteasome inhibitor, on the infectivity and proteolytic activity of Toxoplasma gondii.

We examined the in vitro effect of increasing gliotoxin concentrations on the infectivity of Toxoplasma gondii for NIH-3T3 murine fibroblasts and on Toxoplasma chymotrypsin-like activity, which is specific to the proteasome. Parasite penetration of host cells was not modified by a high gliotoxin concentration (1 microM), but replication was markedly decreased (approximately 50% inhibition by 0.5 microM gliotoxin).

Evidence for the existence of a proteasome in Toxoplasma gondii: intracellular localization and specific peptidase activities.

The proteasome is a large intracellular protein complex whose main function is proteolytic removal of damaged proteins. It has recently been shown that the proteasome has a crucial role in the pathogenesis of protozoan parasites. We attempted to characterize the proteasome of T.

[Mitogen activated protein kinases (MAPK) and Toxoplasma gondii host cell invasion].

Toxoplasmosis is still a big concern in Public Health in France, regarding two particular aspects: congenital toxoplasmosis and reactivated toxoplasmosis in immunodeficient patients. Toxoplasma gondii is an obligate intracellular parasite, that can invade almost all nucleated cells. The invasion step has been widely studied, but its accurate mechanism and the cell receptor remain largely unknown.

Detection of tyrosine phosphorylated proteins in Trichinella spiralis L1 larvae.

Western-blotting analysis showed the presence of tyrosine phosphorylated proteins in crude extracts of T. spiralis larvae and these phosphorylated proteins were located by immunofluorescence on the striations of the larval cuticle. The patterns of phosphorylated proteins were modified when larvae were incubated with bile.

Biochemical characterization of mitogen-activated protein (MAP) kinase activity in Toxoplasma gondii.

Mitogen-activated protein (MAP) kinase or extracellular signal-regulated kinase (ERK) are activated by many extracellular stimuli. In this study, we investigated whether MAP kinase and tyrosine kinases were involved in transducing signals in Toxoplasma gondii. Using anti-phosphotyrosine and anti-active ERK antibodies, we identified several phosphorylated proteins in Toxoplasma.

Involvement of the mitogen-activated protein (MAP) kinase signalling pathway in host cell invasion by Toxoplasma gondii.

Little is known about signalling in Toxoplasma gondii, but it is likely that protein kinases might play a key role in the parasite proliferation, differentiation and probably invasion. We previously characterized Mitogen-Activated Protein (MAP) kinases in T. gondii lysates.

Differential development of Toxoplasma gondii in neural cells.

In this article, Remi Fagard and colleagues discuss the properties of neurons that lead to their low infection by Toxoplasma gondii, and the role that cytokines such as tumour necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) might play.

Rapid activation and nuclear translocation of mitogen-activated protein kinases in response to physiological concentration of glucose in the MIN6 pancreatic beta cell line.

MIN6 is one of the few pancreatic beta cell lines that respond to physiological concentrations of glucose by secreting insulin, and little is known about the triggered molecular mechanisms. We report below that the response to glucose in the MIN6 cells includes an activation of the p42 and p44 mitogen-activated protein (MAP) kinases (ERK2 and ERK1). This activation also occurred with the antidiabetic sulfonylurea glibenclamide and kainate, a specific agonist of a subtype of the ionotropic glutamate receptors, which depolarize the cytoplasmic membrane.

Neurons in primary culture are less efficiently infected by Toxoplasma gondii than glial cells.

Infection by Toxoplasma gondii is asymptomatic, leading to an immune response that controls the disease. In immune-compromised patients, however, quiescent cysts can reactivate, leading to toxoplasmic encephalitis. We studied the infection of cells of the central nervous system in an attempt to understand the process leading to this complication.

Fibroblast growth factors stimulate protein tyrosine phosphorylation and mitogen-activated protein kinase activity in primary cultures of hippocampal neurons.

Fibroblast growth factors (FGFs) are not only mitogens, but they also promote the differentiation of various cell types. For instance, basic FGF (bFGF) provides a critical trophic support for hippocampal neurons in culture. To elicit their biological effects, FGFs interact with high-affinity receptors that are transmembrane proteins with a cytoplasmic portion containing a tyrosine kinase activity.

Rapid activation of hippocampal casein kinase II during long-term potentiation.

Several studies suggest that protein kinase C and type II Ca2+/calmodulin-dependent protein kinase are activated during induction of long-term potentiation (LTP). We now report that casein kinase II (CK-II), which is present in high concentration in the hippocampus, is also activated in the CA1 region during LTP. CK-II activity increased within 2 min after a train of high-frequency electrical stimulations and reached a maximum (2-fold increase) 5 min later before returning to baseline value.

Phosphorylation of the lymphoid cell kinase p56lck is stimulated by micromolar concentrations of Zn2+.

In particulate fractions from LSTRA lymphoma cells, tyrosine phosphorylation of the lymphoid specific tyrosine kinase p56lck is elicited by Zn2+ in the absence of other divalent cations. Zn2+ alone also induces autophosphorylation of immunoprecipitated p56lck. The effect of Zn2+ is dose dependent; it is detected at concentrations of Zn2+ as low as 5 microM and reaches a maximum at 100 microM Zn2+.

The resistance to alkali treatment of the phosphorylation of beta casein versus alpha casein is specific for casein kinase II.

The phosphorylation of mixed casein by casein kinase II shows resistance on beta casein after partial alkali hydrolysis of the proteins separated by gel electrophoresis. This property is specific for casein kinase II among the protein kinases tested and can be used for casein kinase II detection in biological extracts and for characterization of purified casein kinase II.

Clathrin beta-light chain of rat liver coated vesicles is phosphorylated in vitro and in vivo.

Clathrin beta-light chain of rat liver coated vesicles is phosphorylated in vitro in the presence of poly(L-lysine) by an endogenous protein kinase which appears to be similar to casein kinase II. Clathrin beta-light chain is also phosphorylated in vivo. After injection of [32P]phosphate into rats and preparation of purified coated vesicles in the presence of phosphatase inhibitors, electrophoretic analysis showed the presence of several labeled polypeptides including clathrin beta-light chain.

Characterization of the epidermal-growth-factor-dependent phosphorylation system from normal mouse-liver sinusoidal plasma membranes.

Blood sinusoidal plasma membrane subfractions were isolated from normal mouse liver in the presence of the proteinase inhibitors PhMeSO2F and iodoacetamide. They were purified from smooth microsomal and Golgi vesicle contaminants. The phosphorylation reaction was studied at 33 degrees C, in the presence of 2 mM MnCl2.

A membrane-bound protein kinase from mouse liver stimulated by iron.

At microM levels, iron stimulates strongly the in vitro phosphorylation of a membrane protein from mouse liver. This phosphorylation also occurs in the absence of other added divalent cations but to a lower degree. In SDS gels the phosphorylated protein has app.