Localization and regulation of GLUTx1 glucose transporter in the hippocampus of streptozotocin diabetic rats

We describe the localization of the recently identified glucose transporter GLUTx1 and the regulation of GLUTx1 in the hippocampus of diabetic and con trol rats. GLUTx1 mRNA and protein exhibit a unique distribution when compa red with other glucose transporter isoforms expressed in the rat hippocampu s. In particular, GLUTx1 mRNA was detected in hippocampal pyramidal neurons and granule neurons of the dentate gyrus as well as in nonprincipal neuron s. With immunohistochemistry, GLUTx1 protein expression is limited to neuro nal cell bodies and the most proximal dendrites, unlike GLUT3 expression th at is observed throughout the neuropil. Immunoblot analysis of hippocampal membrane fractions revealed that GLUTx1 protein expression is primarily loc alized to the intracellular compartment and exhibits limited association wi th the plasma membrane. In streptozotocin diabetic rats compared with vehic le-treated controls, quantitative autoradiography showed increased GLUTx1 m RNA levels in pyramidal neurons and granule neurons; up-regulation of GLUTx 1 mRNA also was found in nonprincipal cells, as shown by single-cell emulsi on autoradiography. In contrast, diabetic and control rats expressed simila r levels of hippocampal GLUTx1 protein. These results indicate that GLUTx1 mRNA and protein have a unique expression pattern in rat hippocampus and su ggest that streptozotocin diabetes increases steady-state mRNA levels in th e absence of concomitant increases in GLUTx1 protein expression.