Figure 8
Schematic illustration of the proposed mechanism of resorption cycle and vesicular transport during the cycle.
Actin encapsulated vacuoles filled with V-ATPase and proteases are transported to plasma membrane forming the RB area. Filamentous and dynamic branched actin forms the observed AP structures at RB during this process. The vacuoles are likely to be acidified and when fusing with plasma membrane they initiate a rapid decrease of pH in the microenvironment. The V-ATPases remain on the membrane and may maintain the acidic microenvironment for a while. During this process begins endocytosis and subsequent removal of the resorption products. This process needs both dynamin and Arp2/3 and hence, the forces driving the process seem to be generated by branched actin polymerisation. After the active phase stops V-ATPase and both low level of actin remain on the plasma membrane and the resorption may be re-initiated at the same location by fusion of more V-ATPase filled acidified vesicles. The mechanism we propose describes resorption as a dynamic process that relies bursts of acidified vesicles and explains the emergence of clusters of small RPs.
