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Mammalian antizyme (mAz) is a central element of a feedback circuit regulating cellular polyamines by accelerating ornithine decarboxylase (ODC) degradation and inhibiting polyamine uptake. Although yeast antizyme (yAz) stimulates the degradation of yeast ODC (yODC), we show here that it has only a minor effect on polyamine uptake by yeast cells. A segment of yODC that parallels the Az binding segment of mammalian ODC (mODC) is required for its binding to yAz. Although demonstrating minimal homology to mAz, our results suggest that yAz stimulates yODC degradation via a similar mechanism of action. We demonstrate that interaction with yAz provokes degradation of yODC by yeast but not by mammalian proteasomes. This differential recognition may serve as a tool for investigating proteasome functions.

Protein phosphorylation plays a major role in regulating cellular functions. We have previously demonstrated that Sky1p, the SR protein kinase of the budding yeast Saccharomyces cerevisiae, is a regulator of polyamine transport and ion homeostasis. Since its kinase activity was demonstrated essential for fulfilling these roles, we assumed that Sky1p function via substrates phosphorylation. Using an in vitro phosphorylation assay, we have identified Hrb1p as a putative Sky1p substrate. However, phosphorylation analysis in WT and sky1Delta cells and localization studies disproved Hrb1p as a true Sky1p substrate, although a segment of the RS domain is required for determining its subcellular localization. Furthermore, we demonstrate that Hrb1p and additional putative Sky1p substrates, identified by computational approach, are not involved in mediating the spermine tolerant phenotype of sky1Delta cells.

After an injury to the central nervous system (CNS), activated microglia have been shown to contribute to the ongoing destructive processes leading to secondary neuronal degeneration. They can, however, also express neuroprotective activity. Studies from our laboratory point to the existence of a physiological T cell-mediated neuroprotective mechanism (adaptive immunity) that is amenable to boosting. We postulate that the beneficial or destructive outcome of the local microglial (innate) response is determined by a well-controlled dialog between the innate and the adaptive immune players. Here, we show that spontaneous or exogenously boosted T cell-mediated neuroprotection is correlated with early activation of microglia as antigen-presenting cells. We suggest that such microglial activity, if well controlled, is a crucial step in determining the fate of the neurons in a hostile environment.

We recently reported that the posttraumatic spread of degeneration in the damaged optic nerve can be attenuated by the adoptive transfer of autoimmune T cells specific to myelin basic protein. However, it would be desirable to obtain immune neuroprotection free of any possible autoimmune disease. In an attempt to obtain disease-free immune neuroprotection, we used the synthetic four-amino acid polymer copolymer 1 (Cop-1), which is known not to be encephalitogenic despite its cross-reactivity with myelin basic protein. We show here that active immunization with Cop-1 administered in adjuvant, as well as adoptive transfer of T cells reactive to Cop-1, can inhibit the progression of secondary degeneration after crush injury of the rat optic nerve. These results have implications for the treatment of optic neuropathies.

Definitions of automaticity imply insensitivity of the Stroop effect to conscious perceiving of the word. Subjects in the Stroop task reported the meaning of the stimulus word (in addition to its color) in 7% of the trials. The magnitude of the Stroop effect in these trials was correlated with subjects' ability to report the stimulus meaning. Furthermore, the effect was absent when subjects failed to report the stimulus meaning. These findings challenge the assumption that automatic processing is unconscious. A distinction between automatic and non-automatic processing in terms of modes of consciousness is discussed.