Dark Matter in the Milky Way's Dwarf Spheroidal Satellites

The Milky Way's dwarf spheroidal satellites include the nearest, smallest and least luminous galaxies known. They also exhibit the largest discrepancies between dynamical and luminous masses. This article reviews the development of empirical constraints on the structure and kinematics of dSph stellar populations and discusses how this phenomenology translates into constraints on the amount and distribution of dark matter within dSphs. Some implications for cosmology and the particle nature of dark matter are discussed, and some topics/questions for future study are identified.Comment: A version with full-resolution figures is available at http://www.cfa.harvard.edu/~mwalker/mwdsph_review.pdf; 70 pages, 22 figures; invited review article to be published in Vol. 5 of the book "Planets, Stars, and Stellar Systems", published by Springe

A PrPC-caveolin-Lyn complex negatively controls neuronal GSK3β and serotonin 1B receptor

The cellular prion protein, PrP(C), is a glycosylphosphatidylinositol-anchored protein, abundant in lipid rafts and highly expressed in the brain. While PrP(C) is much studied for its involvement under its abnormal PrP(Sc) isoform in Transmissible Spongiform Encephalopathies, its physiological role remains unclear. Here, we report that GSK3β, a multifunctional kinase whose inhibition is neuroprotective, is a downstream target of PrP(C) signalling in serotonergic neuronal cells. We show that the PrP(C)-dependent inactivation of GSK3β is relayed by a caveolin-Lyn platform located on neuronal cell bodies. Furthermore, the coupling of PrP(C) to GSK3β potentiates serotonergic signalling by altering the distribution and activity of the serotonin 1B receptor (5-HT(1B)R), a receptor that limits neurotransmitter release. In vivo, our data reveal an increased GSK3β kinase activity in PrP-deficient mouse brain, as well as sustained 5-HT(1B)R activity, whose inhibition promotes an anxiogenic behavioural response. Collectively, our data unveil a new facet of PrP(C) signalling that strengthens neurotransmission