Roles of the AP-2 and AP-1 complexes in apical cargo sorting, endocytosis and polar growth in fungi

Filamentous fungi provide excellent systems for investigating the role of the AP complexes in polar growth. Using Aspergillus nidulans, we recently showed that AP-2 and AP-1 are essential for polarity maintenance and growth. Surprisingly, the role of AP-2 is clathrin-independent and this is in line with a sequence analysis showing that the AP-2 β subunit (β2) lacks a clathrin-binding domain. AP-2 interacts with endocytic markers SlaB and SagA and the lipid flippases DnfA and DnfB in the sub-apical collar region of hyphae. AP-2 was also shown to be critical for proper apical membrane lipid and cell wall composition. Our findings supported that the AP-2 complex of dikarya has acquired, in the course of evolution, a specialized clathrin-independent function necessary for fungal polar growth. In ECFG14 we will present most recent findings concerning the specific roles of AP-1 in apical cargo sorting and fungal growth.