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- Title
Identification of a mammalian H<sup>+</sup>-myo-inositol symporter expressed predominantly in the brain.
- Authors
Uldry, Marc; Ibberson, Mark; Horisberger, Jean-Daniel; Chatton, Jean-Yves; Riederer, Beat M.; Thorens, Bernard
- Abstract
Inositot and its phosphorylated derivatives play a major role in brain function, either as osmolytes, second messengers or regulators of vesicle endo- and exocytosis. Here we describe the identification and functional characterization of a novel H+-myoinositol co-transporter, HMIT, expressed predominantly in the brain. HMIT cDNA encodes a 618 amino acid polypeptide with 12 predicted transmembrane domains. Functional expression of HMIT in Xenopus oocytes showed that transport activity was specific for myo-inositol and related stereoisomers with a Michaelis-Menten constant of ∼100 μM, and that transport activity was strongly stimulated by decreasing pH. Electrophysiotogical measurements revealed that transport was electrogenic with a maximal transport activity reached at pH 5.0. In rat brain membrane preparations, HMIT appeared as a 75-90 kDa protein that could be converted to a 67 kDa band upon enzymatic deglycosylation. Immunofluorescence microscopy analysis showed HMIT expression in glial cells and some neurons. These data provide the first characterization of a mammalian H4-coupled myoinositol transporter. Predominant central expression of HMIT suggests that it has a key rote in the control of myoinositol brain metabolism.
- Publication
EMBO Journal, 2001, Vol 20, Issue 16, p4467
- ISSN
0261-4189
- Publication type
Academic Journal
- DOI
10.1093/emboj/20.16.4467