microRNA-132 regulates dendritic growth and arborization of newborn neurons in the adult hippocampus.

Newborn neurons in the dentate gyrus of the adult hippocampus rely upon cAMP response element binding protein (CREB) signaling for their differentiation into mature granule cells and their integration into the dentate network. Among its many targets, the transcription factor CREB activates expression of a gene locus that produces two microRNAs, miR-132 and miR-212. In cultured cortical and hippocampal neurons, miR-132 functions downstream from CREB to mediate activity-dependent dendritic growth and spine formation in response to a variety of signaling pathways.

Structural rearrangements at the translocation pore of the human glutamate transporter, EAAT1.

Structure-function studies of mammalian and bacterial excitatory amino acid transporters (EAATs), as well as the crystal structure of a related archaeal glutamate transporter, support a model in which TM7, TM8, and the re-entrant loops HP1 and HP2 participate in forming a substrate translocation pathway within each subunit of a trimer. However, the transport mechanism, including precise binding sites for substrates and co-transported ions and changes in the tertiary structure underlying transport, is still not known. In this study, we used chemical cross-linking of introduced cysteine pairs in a cysteine-less version of EAAT1 to examine the dynamics of key domains associated with the translocation pore.

A hydrophobic domain in glutamate transporters forms an extracellular helix associated with the permeation pathway for substrates.

Recent work has shown that cysteine residues introduced into domain 10, a highly hydrophobic segment in the excitatory amino acid transporter 1, react readily when hydrophilic sulfhydryl-modifying reagents are applied extracellularly. To investigate the functional contributions of this region, we mutated each residue in domain 10 (Ala(446)-Gly(459)) to cysteine and assessed the transport kinetics and inhibitor sensitivities of the mutant carriers. Modification of the introduced sulfhydryl group with membrane-impermeant methanethiosulfonate derivatives inhibited substrate transport by all but one functional cysteine mutant.