Figure 6. Model for the regulation of SV protein recycling versus SV protein degradation via the multivesicular body late endosome (MVB) pathway by AP-1 complexes AP-1/σ1A and AP-1/σ1B.

The Rab5/Vps34-dependent MVB pathway is activated by the ArfGAP1-mediated recruitment of Rabex-5 into a stable AP-1/σ1A - ArfGAP1 complex. Rabex-5 binding to σ1B prevents complex formation and thus stable Rabex-5 recruitment onto endosomes. Post-translational modifications like protein phosphorylation are likely involved in the differential regulation of the pathway by both AP-1 complexes (see also discussion). ArfGAP1 binding to the γ1 (subunit shown in red) ‘ear’-domain may support ArfGAP1 recruitment. σ1A shown in yellow, σ1B in gold, μ1A in dark grey and β1 in light grey.