FIGURE 8:

Model for hypothesized role of the Rab11a-Rab8a-Myo5B network in regulating DFV exocytosis. Newly synthesized DFVs exit the TGN, where they associate with Rab11a, which may facilitate DFV passage through the cytokeratin meshwork. In one scenario, Rab11a may promote early recruitment of the Myo5B motor. In addition, Rab11a stimulates DFV maturation by recruiting Rab8a to the vesicles. The GEF is unknown but is apparently not Rabin8, which is recruited to DFVs by Rab11a and may modulate exocytosis through other effector proteins (not shown). In turn, Rab8a recruits an unknown Rab11a GAP, which would terminate the Rab11a-dependent steps and maintain compartment identity. Myo5B may also be recruited by Rab8a, but the interaction is likely to be ephemeral and may be stabilized by other proteins, including the exocyst subunit Sec15 and SNARE proteins (not shown). An important function of Myo5B is to promote DFV transit through the subapical actin cytoskeleton before fusion.