G-CSF is a potent hematopoietic factor that enhances survival and drives differentiation of myeloid lineage cells, resulting in the generation of neutrophilic granulocytes. Here, we show that G-CSF passes the intact blood-brain barrier and reduces infarct volume in 2 different rat models of acute stroke. G-CSF displays strong anti-apoptotic activity in mature neurons and activates multiple cell survival pathways. Both G-CSF and its receptor are widely expressed by neurons in the CNS, and their expression is induced by ischemia, which suggests an autocrine protective signaling mechanism. Surprisingly, the G-CSF receptor was also expressed by adult neural stem cells, and G-CSF induced neuronal differentiation in vitro. G-CSF markedly improved long-term behavioral outcome after cortical ischemia, while stimulating neural progenitor response in vivo, providing a link to functional recovery. Thus, G-CSF is an endogenous ligand in the CNS that has a dual activity beneficial both in counteracting acute neuronal degeneration and contributing to long-term plasticity after cerebral ischemia. We therefore propose G-CSF as a potential new drug for stroke and neurodegenerative diseases.

AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor channels mediate the fast component of excitatory postsynaptic currents in the central nervous system. Site-selective nuclear RNA editing controls the calcium permeability of these channels, and RNA editing at a second site is shown here to affect the kinetic aspects of these channels in rat brain. In three of the four AMPA receptor subunits (GluR-B, -C, and -D), intronic elements determine a codon switch (AGA, arginine, to GGA, glycine) in the primary transcripts in a position termed the R/G site, which immediately precedes the alternatively spliced modules "flip" and "flop." The extent of editing at this site progresses with brain development in a manner specific for subunit and splice form, and edited channels possess faster recovery rates from desensitization.

The monoamine oxidases play a vital role in the metabolism of biogenic amines in the central nervous system and in peripheral tissues. Using oligonucleotide probes derived from three sequenced peptide fragments, we have isolated cDNA clones that encode the A and B forms of monoamine oxidase and have determined the nucleotide sequences of these cDNAs. Comparison of the deduced amino acid sequences shows that the A and B forms have subunit molecular weights of 59,700 and 58,800, respectively, and have 70% sequence identity. Both sequences contain the pentapeptide Ser-Gly-Gly-Cys-Tyr, in which the obligatory cofactor FAD is covalently bound to cysteine. Based on differences in primary amino acid sequences and RNA gel blot analysis of mRNAs, the A and B forms of monoamine oxidase appear to be derived from separate genes.Monoamine oxidases A and B [MAO A and MAO B, respectively; amine:oxygen oxidoreductase (deaminating) (flavin-containing), EC 1.4.3.4] in the central nervous system and in peripheral tissues catalyze the oxidative deamination of neuroactive and vasoactive amines (1) and the oxidation of xenobiotics, including the parkinsonism-producing neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (2, 3). These enzymes, which are integral proteins of the outer mitochondrial membrane (4), are distinguished by differences in substrate preference (5), inhibitor specificity (6), tissue and cell distribution (7), and immunological properties (8,9). MAO A preferentially oxidizes the biogenic amine serotonin and is inactivated irreversibly by the acetylenic inhibitor clorgyline. MAO B preferentially oxidizes phenylethylamine and benzylamine and is inactivated by the irreversible inhibitors pargyline and deprenyl. The level of MAO activity in almost all human tissues consists of a mixture of both forms of the enzyme, but placental tissue contains predominantly MAO A (10), whereas platelets and lymphocytes express only MAO B (11,12). MAO A and B from several tissue sources and species appear to consist of two subunits with approximate molecular masses of 60 kDa (13,14 (15,19). Peptide maps obtained from proteinase digestion of [3H]pargyline-labeled crude or partially purified MAO A and B suggest that these enzymes differ in their amino acid sequences (17,20). Furthermore, differences in degrees of photo-dependent inactivation of these two enzymes suggest the existence of conformational or structural differences in their active sites (21-23).To clarify the molecular basis of structural and functional differences between these important enzymes, we have isolated and characterized cloned cDNAsI encoding these proteins. The nucleotide and deduced amino acid sequences for human liver MAO A and B show that these two proteins are derived from separate genes. MATERIALS AND METHODSConstruction and Screening of the Human Liver cDNA Library. A Agt1O library was constructed from poly(A)+ mRNA isolated from human liver (24). The phage library contained 2 x 106 individual clones of which 5 x 105 clones were subjected to hy...

Recently, GBR1, a seven-transmembrane domain protein with high affinity for gamma-aminobutyric acid (GABA)B receptor antagonists, was identified. Here, a GBR1-related protein, GBR2, was shown to be coexpressed with GBR1 in many brain regions and to interact with it through a short domain in the carboxyl-terminal cytoplasmic tail. Heterologously expressed GBR2 mediated inhibition of adenylyl cyclase; however, inwardly rectifying potassium channels were activated by GABAB receptor agonists only upon coexpression with GBR1 and GBR2. Thus, the interaction of these receptors appears to be crucial for important physiological effects of GABA and provides a mechanism in receptor signaling pathways that involve a heterotrimeric GTP-binding protein.

Changes of the intestinal mucosal barrier are considered to play a role in the pathogenesis of inflammatory bowel disease (IBD). Our experiments were designed to identify dysregulation of epithelial junctional molecules in the IBD intestinum and to address whether altered expression of these molecules is a primary event in IBD or a phenomenon secondary to the inflammatory process. Noninflamed and inactively and actively inflamed mucosal tissues from patients with ulcerative colitis or Crohn's disease as well as tissues from control subjects were analyzed for the expression of junctional molecules by different methods. Marked downregulation of junctional proteins and their respective mRNAs was observed in actively inflamed IBD tissues. In IBD tissues with inactive inflammation, only a few junctional molecules such as E-cadherin and α-catenin were affected, whereas expression of desmosomal or tight junction-associated proteins appeared almost unchanged. In noninflamed IBD tissues, junctional protein expression was not different from that seen in normal control subjects. In IBD, downregulation of junctional molecule expression is apparently associated with the inflammatory process and does not likely represent a primary phenomenon.