Impaired Insulin Signaling Mediated by the Small GTPase Rac1 in Skeletal Muscle of the Leptin-Deficient Obese Mouse
Insulin-stimulated glucose uptake in skeletal muscle is mediated by the glucose transporter GLUT4. The small GTPase Rac1 acts as a switch of signal transduction that regulates GLUT4 translocation to the plasma membrane following insulin stimulation. However, it remains obscure whether signaling casc...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-07-01
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| Series: | International Journal of Molecular Sciences |
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| Online Access: | https://www.mdpi.com/1422-0067/24/14/11531 |
| _version_ | 1797589077904588800 |
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| author | Man Piu Chan Nobuyuki Takenaka Takaya Satoh |
| author_facet | Man Piu Chan Nobuyuki Takenaka Takaya Satoh |
| author_sort | Man Piu Chan |
| collection | DOAJ |
| description | Insulin-stimulated glucose uptake in skeletal muscle is mediated by the glucose transporter GLUT4. The small GTPase Rac1 acts as a switch of signal transduction that regulates GLUT4 translocation to the plasma membrane following insulin stimulation. However, it remains obscure whether signaling cascades upstream and downstream of Rac1 in skeletal muscle are impaired by obesity that causes insulin resistance and type 2 diabetes. In an attempt to clarify this point, we investigated Rac1 signaling in the leptin-deficient (<i>Lep<sup>ob/ob</sup></i>) mouse model. Here, we show that insulin-stimulated GLUT4 translocation and Rac1 activation are almost completely abolished in <i>Lep<sup>ob/ob</sup></i> mouse skeletal muscle. Phosphorylation of the protein kinase Akt2 and plasma membrane translocation of the guanine nucleotide exchange factor FLJ00068 following insulin stimulation were also diminished in <i>Lep<sup>ob/ob</sup></i> mice. On the other hand, the activation of another small GTPase RalA, which acts downstream of Rac1, by the constitutively activated form of Akt2, FLJ00068, or Rac1, was partially abrogated in <i>Lep<sup>ob/ob</sup></i> mice. Taken together, we conclude that insulin-stimulated glucose uptake is impaired by two mechanisms in <i>Lep<sup>ob/ob</sup></i> mouse skeletal muscle: one is the complete inhibition of Akt2-mediated activation of Rac1, and the other is the partial inhibition of RalA activation downstream of Rac1. |
| first_indexed | 2024-03-11T01:01:13Z |
| format | Article |
| id | doaj.art-f903e46e238940d4a778957b945ab673 |
| institution | Directory Open Access Journal |
| issn | 1661-6596 1422-0067 |
| language | English |
| last_indexed | 2024-03-11T01:01:13Z |
| publishDate | 2023-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | International Journal of Molecular Sciences |
| spelling | doaj.art-f903e46e238940d4a778957b945ab6732023-11-18T19:40:57ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672023-07-0124141153110.3390/ijms241411531Impaired Insulin Signaling Mediated by the Small GTPase Rac1 in Skeletal Muscle of the Leptin-Deficient Obese MouseMan Piu Chan0Nobuyuki Takenaka1Takaya Satoh2Laboratory of Cell Biology, Department of Biological Chemistry, Graduate School of Science, Osaka Metropolitan University, Sakai 599-8531, JapanLaboratory of Cell Biology, Department of Biological Chemistry, Graduate School of Science, Osaka Metropolitan University, Sakai 599-8531, JapanLaboratory of Cell Biology, Department of Biological Chemistry, Graduate School of Science, Osaka Metropolitan University, Sakai 599-8531, JapanInsulin-stimulated glucose uptake in skeletal muscle is mediated by the glucose transporter GLUT4. The small GTPase Rac1 acts as a switch of signal transduction that regulates GLUT4 translocation to the plasma membrane following insulin stimulation. However, it remains obscure whether signaling cascades upstream and downstream of Rac1 in skeletal muscle are impaired by obesity that causes insulin resistance and type 2 diabetes. In an attempt to clarify this point, we investigated Rac1 signaling in the leptin-deficient (<i>Lep<sup>ob/ob</sup></i>) mouse model. Here, we show that insulin-stimulated GLUT4 translocation and Rac1 activation are almost completely abolished in <i>Lep<sup>ob/ob</sup></i> mouse skeletal muscle. Phosphorylation of the protein kinase Akt2 and plasma membrane translocation of the guanine nucleotide exchange factor FLJ00068 following insulin stimulation were also diminished in <i>Lep<sup>ob/ob</sup></i> mice. On the other hand, the activation of another small GTPase RalA, which acts downstream of Rac1, by the constitutively activated form of Akt2, FLJ00068, or Rac1, was partially abrogated in <i>Lep<sup>ob/ob</sup></i> mice. Taken together, we conclude that insulin-stimulated glucose uptake is impaired by two mechanisms in <i>Lep<sup>ob/ob</sup></i> mouse skeletal muscle: one is the complete inhibition of Akt2-mediated activation of Rac1, and the other is the partial inhibition of RalA activation downstream of Rac1.https://www.mdpi.com/1422-0067/24/14/11531Akt2glucose uptakeGLUT4GTPaseinsulinobesity |
| spellingShingle | Man Piu Chan Nobuyuki Takenaka Takaya Satoh Impaired Insulin Signaling Mediated by the Small GTPase Rac1 in Skeletal Muscle of the Leptin-Deficient Obese Mouse International Journal of Molecular Sciences Akt2 glucose uptake GLUT4 GTPase insulin obesity |
| title | Impaired Insulin Signaling Mediated by the Small GTPase Rac1 in Skeletal Muscle of the Leptin-Deficient Obese Mouse |
| title_full | Impaired Insulin Signaling Mediated by the Small GTPase Rac1 in Skeletal Muscle of the Leptin-Deficient Obese Mouse |
| title_fullStr | Impaired Insulin Signaling Mediated by the Small GTPase Rac1 in Skeletal Muscle of the Leptin-Deficient Obese Mouse |
| title_full_unstemmed | Impaired Insulin Signaling Mediated by the Small GTPase Rac1 in Skeletal Muscle of the Leptin-Deficient Obese Mouse |
| title_short | Impaired Insulin Signaling Mediated by the Small GTPase Rac1 in Skeletal Muscle of the Leptin-Deficient Obese Mouse |
| title_sort | impaired insulin signaling mediated by the small gtpase rac1 in skeletal muscle of the leptin deficient obese mouse |
| topic | Akt2 glucose uptake GLUT4 GTPase insulin obesity |
| url | https://www.mdpi.com/1422-0067/24/14/11531 |
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