Cell surface protein aggregation triggers endocytosis to maintain plasma membrane proteostasis

How cells respond to denaturation of extracellular protein domains remained largely unknown. Here, authors describe an aggregation-dependent endocytosis pathway, facilitating uptake and degradation of antibody- and stress-induced protein aggregates. The ability of cells to manage consequences of exogenous proteotoxicity is key to cellular homeostasis. While a plethora of well-characterised machinery aids intracellular proteostasis, mechanisms involved in the response to denaturation of extracellular proteins remain elusive. Here we show that aggregation of protein ectodomains triggers their endocytosis via a macroendocytic route, and subsequent lysosomal degradation. Using ERBB2/HER2-specific antibodies we reveal that their cross-linking ability triggers specific and fast endocytosis of the receptor, independent of clathrin and dynamin. Upon aggregation, canonical clathrin-dependent cargoes are redirected into the aggregation-dependent endocytosis (ADE) pathway. ADE is an actin-driven process, which morphologically resembles macropinocytosis. Physical and chemical stress-induced aggregation of surface proteins also triggers ADE, facilitating their degradation in the lysosome. This study pinpoints aggregation of extracellular domains as a trigger for rapid uptake and lysosomal clearance which besides its proteostatic function has potential implications for the uptake of pathological protein aggregates and antibody-based therapies.

Automated summary

The study reveals an aggregation-dependent endocytosis pathway that facilitates uptake and degradation of protein aggregates. This mechanism of managing exogenous proteotoxicity is crucial for cellular homeostasis. The findings highlight the importance of the response to denaturation of extracellular proteins.