1. The MrgD GPCR and the M-Current
Robert A. Crozier, Seena K. Ajit, Edward J. Kaftan, and Mark H. Pausch
The M-current, initially described by David Brown and Paul Adams in sympathetic ganglion neurons, regulates cell firing in many cell types. These potassium channels, composed of KCNQ2/3 heteromers, are low threshold and noninactivating, thus reducing action potential firing to sustained stimuli. As per the name, muscarine blocks M-current. This week, Crozier et al. examine the interaction of M-current in dorsal root ganglion (DRG) neurons with a member of a G-protein-coupled receptor family that is specifically expressed in sensory neurons. The Mas-related gene (Mrg) product, MrgD, is expressed only in nonpeptidergic, small-diameter nociceptors. Using the MrgD ligand -alanine, the authors report activation of MrgD in DRGs, leading to increased cell firing, similar to the classic effect of muscarine on the M-current. MrgD activation, and thus the blocking of M-current, appeared to involve both a pertussis toxin-sensitive pathway and activation of Gq-dependent phospholipase C.
2. Sef Regulation of Auditory Brainstem Development
Victoria E. Abraira, Naomi Hyun, Andrew F. Tucker, Donald E. Coling, M. Christian Brown, Cindy Lu, Greg Hoffman, and Lisa V. Goodrich
The large family of fibroblast growth factors contributes to multiple aspects of development. Their actions are opposed by several naturally occurring antagonists, which are in themselves FGF target genes. This pattern creates feedback regulation of FGF signaling. Abraira et al. examined the effect of one of these antagonists, Sef, on cochlear development. Sef antagonizes the MAP (microtubule-associated protein) kinase pathway that is induced by FGFs. FGF15 and FGFR1 were expressed in rhombic lip, the source of progenitor cells for the cochlear nucleus complex. Sef was expressed in cells immediately adjacent to the audito
Contact: Sara Harris
Society for Neuroscience