Bax-an emerging role in ectopic cell death.

During embryonic and early postnatal development the combination of cell proliferation, migration, survival and cell death is intimately regulated. In the mouse embryo, significant numbers of primordial germ cells, the founder cells of the gametes, fail to migrate correctly to the genital ridges early in histogenesis. Studies in Bcl-2 associated X protein null mice (Bax(-/-)) have shown that the pro-apoptotic Bax gene is required for the programmed cell death of germ cells left in ectopic locations during and after germ cell migration. Independent studies carried out in the central nervous system of Bax(-/-) mice have shown impaired and ectopic neuronal migration in the cerebellum and olfactory bulb during development and in the adult hippocampus. Taken together, these evidences identify Bax as a major mechanism in ectopic cell death and are the subject of this review.

Neurotrophins and neuronal migration in the developing rodent brain.

Neurotrophins are known to be key regulators of neuronal survival, differentiation, function and plasticity in the developing and adult rodent brain. A novel role for neurotrophins has been emerging from recent research, that of motogenic and chemoattractant factors for several populations of migrating neuronal precursors in the developing mouse brain. The aim of the present article is to summarize and discuss the studies that have contributed to the existing body of evidence.

Biologically active, non membrane-anchored precursors: an overview.

Peptides function as chemical signals between cells of multicellular organisms via specific receptors on target cells. Many hormones, neuromodulators and growth factors are peptides. Peptide hormones and other biologically active peptides are synthesized as higher molecular weight precursor proteins (pro-hormones), which must undergo post-translational modification to yield the bioactive peptide(s). In many instances, more than one biologically active peptide is generated from one and the same precursor. In most cases, these precursors are biologically inert and their existence is confined to the membrane-enclosed subcellular compartments where processing of the pro-hormones takes place. A class of growth factors that derive from membrane-anchored precursors which themselves are biologically active constitute an exception to this model. The list of the membrane-anchored biologically active precursors has been the subject of specialized reviews. The present review focuses on precursors other than membrane-anchored precursors, which were found to be biologically active and which often display different biological activities, and may mediate their effects via receptors independent from those of their generated peptides.

High levels of the proNGF peptides LIP1 and LIP2 in the serum and synovial fluid of rheumatoid arthritis patients: evidence for two new cytokines.

The proNGF peptides LIP1 and LIP2 display multiple biological and physiological properties several of which share common features with the nerve growth factor (NGF). The objective of this study was firstly to demonstrate the presence of these peptides in the human sera and secondly to provide evidence for their involvement in inflammatory diseases. Their levels measured by specific enzyme-linked immunosorbent assays (ELISA) were found to be more than 10-fold higher in sera of patients with rheumatoid arthritis (RA), as compared to healthy controls. High levels of LIP1 and LIP2 were also detected in the synovial fluid (SF) of RA patients. These results provide first evidence for a cytokine-like role of the LIP1 and LIP2 peptides.

Mechanisms of VIP-induced neuroprotection against neonatal excitotoxicity.

Two VIP receptors, shared with a similar affinity by pituitary adenylate cyclase-activating polypeptide (PACAP), have been cloned: VPAC1 and VPAC2. PHI binds to these receptors with a lower affinity. We previously showed that VIP protects against excitotoxic white matter damage in newborn mice. This article aimed to determine the receptor involved in VIP-induced neuroprotection. VIP effects were mimicked with a similar potency by VPAC2 agonists and PHI but not by VPAC1 agonists, PACAP 27 or PACAP 38. VIP neuroprotective effects were lost in mice lacking VPAC2 receptor. In situ hybridization confirmed the presence of VPAC2 mRNA. These data suggest that, in this model, VIP-induced neuroprotection is mediated by VPAC2 receptors. The pharmacology of this VPAC2 receptor seems unconventional as PACAP does not mimic VIP effects and PHI acts with a comparable potency.

Multiple biological activities for two peptides derived from the nerve growth factor precursor.

ProNGF can be cleaved proteolytically at dibasic residues and liberates two other peptides beside NGF, LIP1 a 29 amino acid (aa) peptide and LIP2 a 38 aa peptide. These peptides were found present in the rat intestine and shown to induce rapid phosphorylation of the Trk receptor in cell lines. The present study describes several novel biological properties for these peptides. They exert an anti-proliferative effect on the mitogenic activity of estrogen and IGF in MCF-7 cells. They protect against in vivo induction of excitotoxic lesions by the glutamatergic analogue ibotenate injected into the developing mouse brain and against in vitro NMDA-induced cell death in primary neuronal cultures. They bind to murine microglial cells and induce phosphorylation of Akt. These results suggest a role for LIP1 and LIP2 in cell survival.

Neurotensin and the neurotensin receptor-3 in microglial cells.

Microglia motility plays a crucial role in response to lesion or exocytotoxic damage of the cerebral tissue. The neuropeptide neurotensin elicited the migration of the human microglial cell line C13NJ by a mechanism dependent on both phosphatidylinositol-3 kinase (PI3 kinase) and mitogen-activated protein (MAP) kinases pathways. The effect of neurotensin on cell migration was blocked by the neurotensin receptor-3 propeptide, a selective ligand of this receptor. The type I neurotensin receptor-3 was the only known neurotensin receptor expressed in these microglial cells, and its activation led to the phosphorylation of both extracellular signaling-regulated kinases Erk1/2 and Akt. Furthermore, the effect of neurotensin on cell migration was preceded by a profound modification of the F-actin cytoskeleton, particularly by the rapid formation of numerous cell filopodia. Both the motility and the filopodia appearance induced by neurotensin were totally blocked by selective inhibitors of MAP kinases or PI3 kinase pathways. In the murine microglial cell line N11, the neurotensin receptor-3 is also the only neurotensin receptor expressed, and its activation by neurotensin leads to the phosphorylation of both Erk1/2 and Akt. In these cells, neurotensin induces the gene expression of several cytokines/chemokines, including MIP-2, MCP-1, interleukin-1beta and tumor necrosis factor-alpha. This induction is dependent on both protein kinases pathways. We observed that the effect of neurotensin on the cytokine/chemokine expression is also inhibited by the neurotensin receptor-3 propeptide. This is the demonstration that the neurotensin receptor-3 is functional and mediates both the migratory action of neurotensin and its induction of chemokines/cytokines expression.

Neurotensin receptor-3/sortilin mediates neurotensin-induced cytokine/chemokine expression in a murine microglial cell line.

We show that the type I neurotensin receptor-3 (also called sortilin) is the only known neurotensin receptor expressed in a murine microglial cell line and that its activation leads to phosphorylation of both extracellular signaling-regulated (Erk1/2) and Akt kinases. Using semiquantitative reverse-transcriptase (RT) PCR, we demonstrate that neurotensin induces gene expression of several cytokines/chemokines including macrophage inflammatory protein (MIP)-2, monocyte chemotactic protein (MCP)-1, interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha. This induction is dependent on both phosphatidylinositol 3-kinase and mitogen-activated protein kinases pathways. We observe that the effect of neurotensin on cytokine/chemokine expression is inhibited by the neurotensin receptor-3 propeptide, a selective ligand of this receptor. These results demonstrate that the neurotensin receptor-3 is functional in microglial cells where it mediates the induction of chemokines/cytokines expression by neurotensin.

Positive allosteric modulators of AMPA receptors are neuroprotective against lesions induced by an NMDA agonist in neonatal mouse brain.

Four positive modulators of AMPA-type glutamate receptors (cyclothiazide, CX614, LY404187 and S18986-1) given in acute or chronic manner exerted a neuroprotective effect in lesions induced in postnatal day 5 (P5) mice by intracerebral injection of ibotenate, an NMDA agonist. The neuroprotective effects were mediated via the MAPK pathway since coinjection of the MEK inhibitor, PD98059, blocked the neuroprotective effects. Administration of CX614 to neonatal mice was followed by upregulation of hippocampal and cortical BDNF expression.

Bacteriophage T4-directed DNA synthesis in toluene-treated cells.

DNA synthesis has been studied in T4-infected Escherichia coli cells made permeable to nucleotides by treatment with toluene. The rate of incorporation of labeled deoxyribonucleoside triphosphates into DNA at various times after infection is proportional to the in vivo rate. This in vitro incorporation is dependent on all four deoxyribonucleoside triphosphates (5-hydroxymethyldeoxy-cytidine triphosphate can substitute for dCTP) and Mg(2+). It is stimulated by rATP, partially inhibited by pancreatic DNase, and abolished by N-ethylmalei-mide and 1-beta-d-arabinofuranosylcytosine triphosphate. T4 amber DO (DNA negative) and temperature-sensitive DO mutants under nonpermissive conditions of infection fail to induce DNA synthesis in vitro. The synthesizing activity is intracellular and the DNA product is exclusively T4 DNA. The in vitro synthesis proceeds in a discontinuous manner involving synthesis and subsequent joining of small DNA fragments (about 10S in alkaline sucrose gradients) into larger molecules predominantly one-half the length of mature T4 DNA. No restriction of C-containing or nonglucosylated HMC-containing T4 DNA product is observed in this system.