RESUMO
Selective autophagy is a conserved subcellular process that maintains the health of eukaryotic cells by targeting damaged or toxic cytoplasmic components to the vacuole/lysosome for degradation. A key player in the initiation of selective autophagy in S. Cerevisiae (baker's yeast) is a large adapter protein called Atg11. Atg11 has multiple predicted coiled-coil domains and intrinsically disordered regions, is known to dimerize, and binds and organizes other essential components of the autophagosome formation machinery, including Atg1 and Atg9. We performed systematic directed mutagenesis on the coiled-coil 2 domain of Atg11 in order to map which residues were required for its structure and function. Using yeast-2-hybrid and coimmunoprecipitation, we found only three residues to be critical: I562, Y565, and I569. Mutation of any of these, but especially Y565, could interfere with Atg11 dimerization and block its interaction with Atg1 and Atg9, thereby inactivating selective autophagy.
RESUMO
The induction of bulk autophagy by nitrogen starvation in baker's yeast (S. cerevisiae) involves the upregulation of many autophagy related proteins, including Atg7. One way to investigate the importance of this upregulation is to measure the size and number of autophagosomes formed when insufficient amounts of that protein are available. Atg8 is known to affect autophagosome size, consistent with its role in phagophore expansion. Atg7 is upstream of Atg8, and might therefore be expected to affect only autophagosome size. We used electron microscopy to measure the size and number of autophagosomes formed with limiting amounts of Atg7 and found them to be both smaller and fewer than normal. This suggests that Atg7 may have an Atg8-independent role in autophagosome initiation in addition to its Atg8-dependent role in autophagosome expansion. We also present an improved simulation for estimating original autophagic body number based on the number of cross-sections observed in ultrathin sections.
