Expression of the Na⁺‐d‐Glucose Cotransporter SGLT1 in Neurons

Abstract

In brains of the rabbit, pig, and human, expression of the high‐affinity Na+‐d‐glucose cotransporter SGLT1 and of the protein RS1, which alters the activity of SGLT1, was demonstrated. In situ hybridization showed that SGLT1 and RS1 are transcribed in pyramidal cells of brain cortex and hippocampus and in Purkinje cells of cerebellum. In neurons of pig brain SGLT1 protein was demonstrated by western blotting with synaptosomal membranes and by immunohistochemistry, which showed SGLT1 in pyramidal and Purkinje cells. To test whether SGLT1 in neurons may be activated during increased d‐glucose consumption, an epileptic seizure was induced in rat brain, and the uptake of specific nonmetabolized substrates of SGLT1 {[14C]methyl‐α‐d‐glucopyranoside ([14C]AMG)} and of Na+‐independent transporters {2‐deoxy‐d‐[14C]glucose([14C]2‐DG)} was analyzed by autoradiography. During the seizure the uptake of AMG and 2‐DG was increased in the focus. Within two hours after the seizure 2‐DG uptake in the focus returned to normal. In contrast, the AMG uptake in the focus area was still increased 1 day later. The data show that the high‐affinity Na+‐d‐glucose cotransporter SGLT1 is expressed in neurons and can be up‐regulated.

The Plasma Membrane-associated Protein RS1 Decreases Transcription of the Transporter SGLT1 in Confluent LLC-PK1 Cells

“…2a). In control experiments, staining was abolished when the antibodies SGLT1-ab and pRS1-ab were pre-absorbed with the antigenic SGLT1 peptide or with purified pRS1 protein, respectively (29,43). Whereas no immunoreactivity for SGLT1 was observed in the cytosolic or endosomal membrane fractions, SGLT1 was detected in the PME fraction (Fig.…”

“…For antibody reaction, the blots were incubated for 2 h at 25°C with affinity-purified polyclonal rabbit antibodies against porcine SGLT1 (pSGLT1-ab) or porcine RS1 (pRS1-ab) that were diluted 1:10 or 1:2500 in blocking buffer, respectively. The antibodies have been described earlier (29,43). pSGLT1-ab are raised against the amino acids 525-542 of porcine SGLT1 and affinity-purified on the antigenic peptide fixed to Sepharose, whereas pRS1-ab was raised against recombinant pRS1 protein expressed in E. coli and affinity-purified on the recombinant protein fixed to enzyme-linked immunosorbent assay plates.…”

“…Lipofectin and prestained marker proteins for SDS-polyacrylamide gel electrophoresis (BenchMark TM ) were supplied by Life Technologies, Inc., geneticin (G418) by Calbiochem, and Bradford protein assay by Bio-Rad. All other chemicals were obtained as described earlier (26,43). 1 Cells-LLC-PK 1 cells were derived from porcine kidney and exhibited properties similar to the S3 segment of the proximal tubule (15).…”

Identification of a Novel Na+/myo-Inositol Cotransporter

“…Novel Na ϩ /myo-Inositol Cotransporter (4,35,36), but the function of the protein had never been established.…”

Physiological and Molecular Characteristics of Rat Hypothalamic Ventromedial Nucleus Glucosensing Neurons

“…Also, GLUT4 and insulin receptor (INS-R) expression overlap in brain areas involved in glucosensing (37) and thus might play a potential role in neuronal glucosensing. Finally, the high-affinity Na ϩ -Dglucose cotransporter-1 (SGLT-1) is expressed in brain (38) and its inhibition with phloridzin reduces activity in hypothalamic GE neurons (8). However, SGLT-1 has not been localized definitively on glucosensing neurons.…”