Identification of Sortilin Alternatively Spliced Variants in Mouse 3T3L1 Adipocytes
Type 2 diabetes mellitus is a metabolic disorder defined by systemic insulin resistance. Insulin resistance in adipocytes, an important regulator of glucose metabolism, results in impaired glucose uptake. The trafficking protein, sortilin, regulates major glucose transporter 4 (Glut4) movement, ther...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2021-01-01
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| Series: | International Journal of Molecular Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1422-0067/22/3/983 |
| Summary: | Type 2 diabetes mellitus is a metabolic disorder defined by systemic insulin resistance. Insulin resistance in adipocytes, an important regulator of glucose metabolism, results in impaired glucose uptake. The trafficking protein, sortilin, regulates major glucose transporter 4 (Glut4) movement, thereby promoting glucose uptake in adipocytes. Here, we demonstrate the presence of an alternatively spliced sortilin variant (Sort<sup>17b</sup>), whose levels increase with insulin resistance in mouse 3T3L1 adipocytes. Using a splicing minigene, we show that inclusion of alternative exon 17b results in the expression of Sort<sup>17b</sup> splice variant. Bioinformatic analysis indicated a novel intrinsic disorder region (IDR) encoded by exon 17b of Sort<sup>17b</sup>. Root mean square deviation (RMSD) and root mean square fluctuation (RMSF) measurements using molecular dynamics demonstrated increased flexibility of the protein backbone within the IDR. Using protein–protein docking and co-immunoprecipitation assays, we show robust binding of Glut4 to Sort<sup>17b</sup>. Further, results demonstrate that over-expression of Sort<sup>17b</sup> correlates with reduced Glut4 translocation and decreased glucose uptake in adipocytes. The study demonstrates that insulin resistance in 3T3L1 adipocytes promotes expression of a novel sortilin splice variant with thus far unknown implications in glucose metabolism. This knowledge may be used to develop therapeutics targeting sortilin variants in the management of type 2 diabetes and metabolic syndrome. |
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| ISSN: | 1661-6596 1422-0067 |