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Among 14 peripheral blood samples obtained from patients affected by B chronic lymphocytic leukemia (B-CLL) at initial stages (Rai 0–1) of the disease, 6 showed intermediate/high levels of Zap-70 while 8 displayed low/absent levels of Zap-70. Although Zap-70high and Zap-70low B-CLL samples displayed similar levels of surface death receptor TRAIL-R2, recombinant TRAIL induced cytotoxicity only in a subset of Zap-70low B-CLL samples while Zap-70high were completely resistant to TRAIL. The gene expression profiling was next analyzed in all B-CLL samples treated with either chlorambucil or recombinant TRAIL. While chlorambucil up-regulated the steady-state mRNA levels of known p53 target genes, such as PUMA, Fas/CD95 and MDM2 in all B-CLL samples examined, it significantly down-regulated survivin in Zap-70low but not in Zap-70high. On the other hand, recombinant TRAIL up-regulated the expression of several cytokines (IL-1β, IL-1α, IL-8), which have been involved in promoting B-CLL cell survival. In particular, TRAIL selectively up-regulated IL-1β in Zap-70low B-CLL samples, while it markedly and selectively up-regulated its own mRNA and that of cyclooxigenase-2 (COX-2) in Zap-70high. Taken together, our findings suggest that a significant expression of Zap-70 modulate the response of B-CLL to TRAIL, which might represents an initial step in the pathogenesis of B-CLL. J. Cell. Physiol. 213: 229–236, 2007. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Pro- and mature brain-derived neurotrophic factor (BDNF) activate two distinct receptors: p75 neurotrophin receptor (p75NTR) and TrkB. Mature BDNF facilitates hippocampal synaptic potentiation through TrkB. Here we report that proBDNF, by activating p75NTR, facilitates hippocampal long-term depression (LTD). Electron microscopy showed that p75NTR localized in dendritic spines, in addition to afferent terminals, of CA1 neurons. Deletion of p75NTR in mice selectively impaired the NMDA receptor–dependent LTD, without affecting other forms of synaptic plasticity. p75NTR−/− mice also showed a decrease in the expression of NR2B, an NMDA receptor subunit uniquely involved in LTD. Activation of p75NTR by proBDNF enhanced NR2B-dependent LTD and NR2B-mediated synaptic currents. These results show a crucial role for proBDNF-p75NTR signaling in LTD and its potential mechanism, and together with the finding that mature BDNF promotes synaptic potentiation, suggest a bidirectional regulation of synaptic plasticity by proBDNF and mature BDNF. [ABSTRACT FROM AUTHOR]

Abstract The cellular distribution of GABAC receptor ρ1 and ρ2 subunits in the rat central nervous system remains controversial. We investigated how these subunits were distributed in cerebellum, hippocampus and spinal cord at postnatal day 1, 7 or in adult life. We found that in the adult cerebellum ρ1 and ρ2 mRNAs were expressed in Purkinje cells and basket-like cells only. In the hippocampus both subunits were expressed throughout the CA1 pyramidal layer, dentate gyrus and scattered interneurons with maximum staining intensity at P7. In the adult hippocampus in situ staining was predominantly found on interneurons. GABAC antibody labelling in P7 and adult hippocampus was largely overlapping with the in situ staining. Western blot analysis showed GABAC receptor in retina, ovary and testis. In the spinal cord the ρ2 signal was consistently stronger than ρ1 with overlapping expression patterns. At P1, the most intensely labelled cells were the motoneurons while on P7 and adult sections, interneurons and motoneurons were likewise labelled. On spinal neurons both ρ1 and ρ2 mRNAs showed somatodendritic localization, extending out for >100 µm with punctate appearance especially in adult cells. A similar spinal distribution pattern was provided with polyclonal antibody labelling, suggesting close correspondence between mRNA and protein compartmentalization. Electrophysiological experiments indicated that P1 spinal motoneurons did possess functional GABAC receptors even though GABAC receptors played little role in evoked synaptic transmission. Our results suggest a pattern of ρ1 and ρ2 subunit distribution more widespread than hitherto suspected with strong developmental regulation of subunit occurrence. [ABSTRACT FROM AUTHOR]