Autophagy in the yeast cell

My first Illustration back in December 2017.
My PhD paper just got accepted and one day this idea stroke into my head. I collected paper and pencils and started to draw from the middle to the outer parts.
I drew a Cvt (Cytoplasm to Vacuole Targeting) vesicle being formed in the cytoplasm of a S. cerevisiae yeast cell. During Cvt pathway, hidrolytic enzymes synthetized in the cytoplasm of the cell are specifically delivered to the vacuole (big cisterna on the right), a degradation center where they exert their function as degradative enzymes. The Cvt vesicle consists of a double lipid membrane (yellow) that surrounds enzyme cargo-receptor complexes (blue/light violet/dark green).
Among these enzymes, there are the aminopeptidase Ape1 (light violet) complex, that had been recently imaged by microscopists and could be drawn in a close to real shape, and alphamannosidase Ams1 (dark green), involved in oligasaccharide degradation. Atg19 (light blue, where Atg stands for AuTophaGy) is the receptor for both enzymes and it binds to them at specific sites. While dodecameric Ape1 complexes form, Atg19 trimers are included in the assembly and thus cargo-receptor complexes are formed.
We discovered that Atg19 functions as a bridge to recruit other autophagy proteins that also function in Cvt and participate in the formation of these vesicles. In fact, Atg19 directly interacts with the autophagy specific E3-like ligase Atg12–Atg5/Atg16 complex (light green), an enzyme that finalizes the attachment of Atg8, a ubiquitin-like molecule hallmark of autophagy, to a phospholipid present in the vesicle membrane. Atg5 directly interacts with a short peptide motif (AIM, Atg8 Interacting Motif) in the tail of Atg19 (black line).
When the dimeric E1-like enzyme Atg7 (dark blue) with its characteristic ‘dove-shape’ is loaded with Atg8 molecules, together with the E2-like enzyme Atg3 (violet), that directly interacts with the Atg12 subunit of the E3-like ligase, get in proximity, they allow the transfer of Atg8 to the membrane.
During Cvt pathway and in most of selective types of autophagy, all these molecules (receptors and ubiquitin-like machinery) come into action to build and shape the vesicle.
Upon closure, its outer membrane fuses with that of the vacuole and the cargo-receptor complexes are delivered to destination so that the enzymes can function as resident hydrolases.
This work was conducted by graduate student Dorotea Fracchiolla, PostDoc Justyna Sawa-Makarska and colleagues in the Laboratory of Prof. Sascha Martens (Max Perutz Labs, Vienna – AT) and Prof. Claudine Kraft (now at University of Freiburg, Freiburg – DE).

To read the full research paper visit: https://elifesciences.org/articles/18544