Identification of a mammalian H(+)-myo-inositol symporter expressed predominantly in the brain

EMBO J. 2001 Aug 15;20(16):4467-77. doi: 10.1093/emboj/20.16.4467.


Inositol 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(+)-myo- inositol 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 approximately 100 microM, and that transport activity was strongly stimulated by decreasing pH. Electrophysiological 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 H(+)-coupled myo- inositol transporter. Predominant central expression of HMIT suggests that it has a key role in the control of myo-inositol brain metabolism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Brain / metabolism*
  • Brain / physiology
  • Cell Line, Transformed
  • DNA, Complementary
  • Electrophysiology
  • Glucose Transport Proteins, Facilitative
  • Humans
  • Hydrogen-Ion Concentration
  • Inositol / metabolism*
  • Intracellular Fluid
  • Mammals
  • Membrane Proteins / biosynthesis*
  • Membrane Proteins / genetics
  • Microscopy, Fluorescence
  • Molecular Sequence Data
  • Monosaccharide Transport Proteins / biosynthesis*
  • Monosaccharide Transport Proteins / genetics
  • RNA, Messenger
  • Rats
  • Xenopus


  • DNA, Complementary
  • Glucose Transport Proteins, Facilitative
  • Membrane Proteins
  • Monosaccharide Transport Proteins
  • RNA, Messenger
  • SLC2A13 protein, human
  • Slc2a13 protein, rat
  • Inositol

Associated data

  • GENBANK/AJ315643
  • GENBANK/AJ315644