Fig. 1.

The endomembrane system of cardiomyocytes consists of several functionally different compartments. In the translocation process (red arrows) proteins are synthesized in the endoplasmic reticulum and further modified in the Golgi apparatus. There, the budding of transport vesicles occurs and vesicles are transported to the endosomal system. GLUT4 is further transported to specific insulin-responsive GLUT4 storage vesicles (GSV). GLUT4 and CD36 can be stimulated to translocate from their compartments to the sarcolemma. In the endocytosis process (blue arrows), sarcolemmal proteins are taken up into the cell again and transported through the early endosomes and directed towards lysosomes for protein breakdown or towards the recycling endosomes for renewed use at the sarcolemma