CLC2 (clathrin light chain 2)-ATG8h/ATG8i interactions connect clathrin-mediated endocytosis (CME) and the autophagy pathway

Extensive interconnection has been established between clathrin-mediated endocytosis (CME) and the macroautophagy/autophagy pathway in yeast and mammals. However, the evidence that connects these two pathways in plants has been limited. Starting from the phenotypic similarities in carbon starvation and immune responses shared between the double mutant of CLC2 (clathrin light chain 2) and CLC3, clc2-1 clc3-1, and the atg2-1 mutant in Arabidopsis, we found that the autophagy pathway is compromised in the clc2-1 clc3-1 mutant. Subsequently, we demonstrated that CLC2 interacts specifically with ATG8h and ATG8i, two clade II ATG8 isoforms. The CLC2-ATG8h/ATG8i interaction depends on an Atg8-family interacting motif (AIM) present in CLC2 and an AIMs docking site (ADS) present in ATG8h, respectively. In addition, CLC2-GFP is subjected to autophagic degradation and the degradation of GFP-ATG8h is significantly reduced in the clc2-1 clc3-1 mutant. Last, simultaneously knocking out ATG8h and ATG8i enhances disease resistance, corroborating the functional relevance of the CLC2-ATG8h/8i interactions. These findings reveal that CME and the autophagy pathway are intersected via CLC2-ATG8h/8i interactions in Arabidopsis.