Identification of further important residues within the Glut4 carboxy-terminal tail which regulate subcellular trafficking.
The insulin-responsive glucose transporter, Glut4, exhibits a unique subcellular distribution such that in the absence of insulin >95% of the protein is stored within intracellular membranes. In response to insulin, Glut4 exhibits a large mobilisation to the plasma membrane. Studies of the amino acid motifs which regulate the unique trafficking of Glut4 have identified several key residues within the soluble cytoplasmic N- and C-terminal domains of Glut4. Of particular note is a Leu-498Leu-499 motif within the C-terminal domain that has been proposed to regulate both internalisation from the plasma membrane and sorting to an insulin-sensitive compartment. In this study, we have examined the role of the adjacent amino acids (Glu-491, Gln-492 and Glu-493) by their sequential replacement with Ala. Our results are consistent with the notion that Glu-491 and Glu-493 play an important role in the sub-endosomal trafficking of Glut4, as substitution of these residues with Ala results in increased levels of these proteins at the cell surface, reduced insulin-stimulated translocation and increased susceptibility to endosomal ablation. These residues, together with other identified sequences within the C-terminus of Glut4, are likely to be crucial targeting elements that regulate Glut4 subcellular distribution.
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Division of Biochemistry and Molecular Biology, Davidson Building, Institute of Biomedical and Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK.
Lee
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Melvin
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Gould
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D016475:3T3 Cells; D019943:Amino Acid Substitution / Q000235:genetics; D000596:Amino Acids / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects / Q000235:genetics; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000494:pharmacology; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000502:physiology*; D009124:Muscle Proteins; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000235:genetics; D011994:Recombinant Proteins / Q000138:chemical synthesis / Q000235:genetics / Q000494:pharmacology; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology
D000596:Amino Acids; D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; C495693:Slc2a4 protein, mouse; D005947:Glucose