- The muscle glucose transporter 4 (GLUT4) cycles continuously to/from the cell membrane. Insulin promotes GLUT4-exocytosis, effectively augmenting surface GLUT4 levels. Such traffic must involve recognition by diverse proteins in distinct cellular domains. Here we use stable isotope labelling by amino acids in cell culture (SILAC) to identify insulin-dependent GLUT4-binding proteins by mass spectrometry. Insulin increased GLUT4 interaction with several cytoskeletal proteins, notably α-actinin-4, and reduced interaction with several proteins involved in protein degradation pathways.