Implications of Glucose Transporter Protein Type 1 (GLUT1)-Haplodeficiency in Embryonic Stem Cells for Their Survival in Response to Hypoxic Stress

Abstract

Glucose transporter protein type 1 (GLUT1) is a major glucose transporter of the fertilized egg and preimplantation embryo. Haploinsufficiency for GLUT1 causes the GLUT1 deficiency syndrome in humans, however the embryo appears unaffected. Therefore, here we produced heterozygous GLUT1 knockout murine embryonic stem cells (GT1؉/؊) to study the role of GLUT1 deficiency in their growth, glucose metabolism, and survival in response to hypoxic stress. GT1(؊/؊) cells were determined to be nonviable. Both the GLUT1 and GLUT3 high-affinity, facilitative glucose transporters were expressed in GT1(؉/؉) and GT1(؉/؊) embryonic stem cells. GT1(؉/؊) demonstrated 49 ؎ 4% reduction of GLUT1 mRNA. This induced a posttranscriptional, GLUT1 compensatory response resulting in 24 ؎ 4% reduction of GLUT1 protein. GLUT3 was unchanged. GLUT8 and GLUT12 were also expressed and unchanged in GT1(؉/؊). Stimulation of glycolysis by azide inhibition of oxidative phosphorylation was impaired by 44% in GT1(؉/؊), with impaired up-regulation of GLUT1 protein. Hypoxia for up to 4 hours led to 201% more apoptosis in GT1(؉/؊) than in GT1(؉/؉) controls. Caspase-3 activity was 76% higher in GT1(؉/؊) versus GT1(؉/؉) at 2 hours. Heterozygous knockout of GLUT1 led to a partial GLUT1 compensatory response protecting nonstressed cells. However, inhibition of oxidative phosphorylation and hypoxia both exposed their increased susceptibility to these stresses.

Dematin and Adducin Provide a Novel Link between the Spectrin Cytoskeleton and Human Erythrocyte Membrane by Directly Interacting with Glucose Transporter-1

“…We have not examined the neurological status of the dematin headpiece domain knock-out mice as yet. It is known that genetic inactivation of mouse GLUT1 results in embryonic lethality suggesting a critical role of this transporter in the cellular physiology of multiple tissues (49,50). As our results indicate the significance of the dematin-adducin-GLUT1 bridge in the maintenance of erythrocyte membrane stability, a possibility now exists that this novel complex could also have significant functional implications in the regulation of membrane stability and glucose homeostasis in many nonerythroid cells.…”

Modulation and Compensation of the mRNA Expression of Energy Related Transporters in the Brain of Glucose Transporter 1-Deficient Mice

“…Heilig et al (2003) have described GLUT1-deficient transgenic mice produced by antisense treatment, and the expression of antisense from the transgene varied from one tissue to another. In contrast, the insertion of the trapping vector truncated GLUT1 mRNA resulting in translation of the first 6 amino acids in the intracellular region (Fig.…”

Will the original glucose transporter isoform please stand up!

“…Furthermore, inhibition of oxidative phosphorylation led to impaired upregulation of GLUT1 protein in GLUT1 ϩ/Ϫ embryonic stem cells, which was evident in wild-type cells (50).…”