The 30th International Conference on Arabidopsis Research (ICAR 2019)

727 / 2019-05-09 22:18:57

AtEH/Pan1 drives autophagosome formation at ER-PM contact sites in concert with the actin cytoskeleton and the endocytic machinery

endocytosis,actin,autophagy,clathrin,ER-PM contact sites

Plenary track > Cell Biology

Modulation of cellular communication requires control over the PM proteome. Clathrin-mediated endocytosis (CME) is the predominant pathway in eukaryotes to internalize PM material and extracellular ligands. Initiation of CME relies on adaptor protein complexes, which precisely select the cargo to be internalized, recruit clathrin and facilitate membrane curvature.
The identification of the TPLATE complex (TPC) as a novel adaptor complex regulating CME in plants challenged the general belief that CME was highly conserved in eukaryotes. TPC consists out of eight proteins without obvious homologs in animal or yeast genomes. Slime molds contain a similar complex, although it appears to lack two subunits.
These two TPC subunits, AtEH1 and AtEH2, share sequence similarity with the yeast ARP2/3 complex activator, Pan1p. Here, we show that these proteins are also involved in actin cytoskeleton regulated autophagy. Both AtEH/Pan1 proteins localize to the plasma membrane and to autophagosomes. AtEH/Pan1 positive autophagosomes recruit TPC, AP-2, Clathrin, ATG and ARP2/3. Increased expression of AtEH/Pan1 boosts autophagosome formation, while reduced expression renders plants more susceptible to nutrient depleted conditions. Moreover, AtEH/Pan1 regulated autophagosomes associate with VAP27-1 at ER-PM contact sites (EPCS). In conclusion, our results suggest that AtEH/Pan1 proteins regulate an autophagosome-dependent degradation pathway between the EPCS at the PM and the vacuole.