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. Author manuscript; available in PMC: 2014 Apr 1.
Published in final edited form as: Exerc Sport Sci Rev. 2013 Apr;41(2):77–86. doi: 10.1097/JES.0b013e318275574c

Fig 4. Contraction mediated GLUT4 trafficking in mature muscle.

Fig 4

(A) Several parallel signalling pathways lead to contraction mediated GLUT4 translocation. Intravital imaging has not found any indication of differential compartmentalization in regard to calcium activated calmodulin dependent kinase (CAMKII) - or AMP activated kinase (AMPK) - activation induced GLUT4 translocation. However, any local differences in Serine/threonine kinase 11 (LKB1) or the AMPK related kinase sucrose non-fermenting AMPK related kinase (SNARK) signalling have not yet been studied. Therefore potential compartmentalization of these signals remains to be elucidated. (B) Intravital imaging of contraction mediated GLUT4-EGFP translocation in a part of a muscle fiber in situ in a living mouse (for further details see (19)). At t=0, GLUT4-EGFP is localized to larger and smaller vesicular depots throughout the muscle fiber and around the lateralized nuclei. Immediately after t=0 in situ contractions were initiated for 3×5 min periods (for further details see (19)). After each 5 min period, an image was taken at t=5, t=10 and t=15. It is seen that GLUT4-EGFP is gradually being inserted into the sarcolemma indicated by staining along the plasma membrane (horizontal arrow). Simultaneously a striated pattern is gradually emerging indicating GLUT4-EGFP translocation to t-tubules (vertical arrow). This indicates that translocation to both membrane surfaces takes place with similar kinetics (for quantification see (19). In addition, the basal GLUT4-EGFP depots have gradually been depleted with contractions. Bar = 20 μm.