Elucidation of the glucose transport pathway in glucose transporter 4 via steered molecular dynamics simulations.
BACKGROUND
GLUT4 is a predominant insulin regulated glucose transporter expressed in major glucose disposal tissues such as adipocytes and muscles. Under the unstimulated state, GLUT4 resides within intracellular vesicles. Various stimuli such as insulin translocate this protein to the plasma membrane for glucose transport. In the absence of a crystal structure for GLUT4, very little is known about the mechanism of glucose transport by this protein. Earlier we proposed a homology model for GLUT4 and performed a conventional molecular dynamics study revealing the conformational rearrangements during glucose and ATP binding. However, this study could not explain the transport of glucose through the permeation tunnel.


RESULTS
To elucidate the molecular mechanism of glucose transport and its energetic, a steered molecular dynamics study (SMD) was used. Glucose was pulled from the extracellular end of GLUT4 to the cytoplasm along the pathway using constant velocity pulling method. We identified several key residues within the tunnel that interact directly with either the backbone ring or the hydroxyl groups of glucose. A rotation of glucose molecule was seen near the sugar binding site facilitating the sugar recognition process at the QLS binding site.


CONCLUSIONS
This study proposes a possible glucose transport pathway and aids the identification of several residues that make direct interactions with glucose during glucose transport. Mutational studies are required to further validate the observation made in this study.
Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, India.
Aswathy
A
Sheena
Suma S
SS
Mohan
Nidhina Pachakkil A
NP
Haridas
Gopalakrishnapillai
G
Anilkumar
D000596:Amino Acids / Q000378:metabolism; D001665:Binding Sites; D001692:Biological Transport; D004734:Energy Metabolism; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D010539:Permeability
D000596:Amino Acids; D051275:Glucose Transporter Type 4; D005947:Glucose