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Extracellular gating of glucose transport through GLUT 1
1Department of Physics, University of Texas at San Antonio, San Antonio, TX, 78249, USA.
Biochemical and Biophysical Research Communications
|March 3, 2019
Summary
A new mechanism for glucose transporter 1 (GLUT1) function reveals an extracellular gating mechanism. This explains rapid glucose transport at physiological temperatures and altered transport at lower temperatures, differing from the alternating access theory.
Area of Science:
- Structural biology
- Biophysics
- Computational biology
Background:
- Glucose transporter 1 (GLUT1) is crucial for energy metabolism in various tissues, including the central nervous system and muscles.
- Previous molecular dynamics (MD) simulations of GLUT1 used simplified lipid bilayers, leading to theoretical inconsistencies with experimental kinetic data.
- Existing models like the alternating access theory (AAT) do not fully explain GLUT1's observed transport kinetics across different temperatures.
Purpose of the Study:
- To investigate the mechanism of glucose transport by GLUT1 using more physiologically relevant membrane models.
- To reconcile discrepancies between theoretical simulations and experimental data regarding GLUT1 kinetics.
- To propose a novel mechanism explaining GLUT1's temperature-dependent transport behavior.
Main Methods:
- Unbiased molecular dynamics (MD) simulations of GLUT1 embedded in an asymmetric lipid bilayer mimicking the erythrocyte membrane.
- Simulations were conducted at near-physiological (37°C) and sub-physiological (5°C) temperatures.
- Analysis focused on the conformational changes of GLUT1's extracellular gate and its interaction with glucose in different conditions.
Main Results:
- A novel extracellular (EC) gating mechanism for GLUT1 was identified.
- At 37°C, the EC gate widely accommodates glucopyranose.
- At 5°C, the EC gate's opening is temperature and intracellular glucose concentration-dependent, gating out glucopyranose in the absence of intracellular glucose.
Conclusions:
- The proposed EC-gating mechanism provides a simpler explanation for GLUT1 function compared to AAT.
- This mechanism accurately explains rapid glucose transport at physiological temperatures and significant trans-acceleration at sub-physiological temperatures.
- The findings resolve inconsistencies in previous simulations and experimental data, particularly regarding Arrhenius activation barriers for zero-trans uptake.
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