This study was supported in part by the Sixth Research Framework Programme of the European Union, Project INCA (LSHC-CT-2005-018704) and a Leukemia and Lymphoma Society Scholarship to G. M. Conflict of interest: The authors declare no financial or commercial conflict Etoposide in vitro of interest. Detailed facts of importance to
specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. “
“Loss of ζ-associated protein 70 (Zap70) results in severe immunodeficiency in humans and mice because of the critical role of Zap70 in T-cell receptor (TCR) signalling. Here we describe a novel mouse strain generated by N-ethyl-N-nitrosourea mutagenesis, with the reduced protein stability (rps) mutation in Zap70. The A243V rps mutation resulted in decreased Zap70 protein and a reduced duration of TCR-induced calcium responses, equivalent to that induced by a 50% decrease in catalytically active Zap70. The reduction of signalling through Zap70 was insufficient to substantially perturb thymic differentiation of conventional CD4 and CD8 T cells, although Foxp3+ regulatory T cells demonstrated altered thymic production and peripheral homeostasis. Despite the mild phenotype, the Zap70A243V variant lies just above the functional threshold for TCR signalling competence, as T cells relying on only a single copy of the Zap70rps allele for
TCR signalling demonstrated no intracellular calcium response to TCR find more stimulation. This addition
to the Zap70 allelic series indicates that a rate-limiting threshold for Zap70 protein levels exists at which signalling capacity switches from nearly intact to effectively null. “
“Leishmania are protozoan parasites that infect macrophages and their survival is partially achieved Etomidate through inhibition of the cellular oxidative burst by parasite lipophosphoglycan (LPG). PKCα is the predominant PKC isoenzyme required for macrophage oxidative burst, yet it is not known if different susceptibility of BALB/c and C57BL/6 mice to Leishmania mexicana could be related to PKCα. We analysed the effect of L. mexicana promastigotes and parasite LPG on expression of PKCα and on its activity in macrophages of both mouse strains. Our data show that expression of the isoenzyme was not altered either by LPG or by L. mexicana promastigotes. Yet LPG exerted opposing effects on PKCα activity of macrophages between both strains: in susceptible BALB/c cells, it inhibited PKCα activity, whereas in the more resistant strain it augmented enzymatic activity 2·8 times. In addition, LPG inhibited oxidative burst only in susceptible BALB/c macrophages and the degree of inhibition correlated with parasite survival. Promastigotes also inhibited PKCα activity and oxidative burst in macrophages of BALB/c mice, whereas in C57BL/6, they enhanced PKCα activity and oxidative burst inhibition was less severe.