Autophagy cooperates with PDGFRA to support oncogenic growth signaling

Abstract

ABSTRACT Macroautophagy (referred to as autophagy hereafter) is a highly conserved catabolic process which sequesters intracellular substrates for lysosomal degradation. Autophagy-related proteins have been shown to be involved in various aspects of tumor development by engaging with multiple cellular substrates. We recently uncovered a novel role for autophagy in regulating the signaling and levels of PDGFRA, a receptor tyrosine kinase amplified in several cancers. We discovered that PDGFRA can be targeted to autophagic degradation by binding the autophagy cargo receptor SQSTM1. Surprisingly, PDGFRA-mediated signaling is perturbed in the absence of autophagy despite enhanced receptor levels. We show that this is due to disrupted trafficking of the receptor to late endosomes where signaling activity persists. Conversely, prolonged autophagy inhibition results in a transcriptional downregulation of Pdgfra as a result of inhibited signaling activity demonstrating that short- and long-term autophagy inhibition have opposing effects on receptor levels. We further investigated the consequence of PDGFRA regulation by autophagy using a mouse model for gliomagenesis where we observed a disruption in PDGFA-driven tumor formation when autophagy is inhibited. Activation of downstream signaling through Pten mutation overrides the need for autophagy during tumor development suggesting a genotype-specific role for autophagy during tumorigenesis. Altogether, our findings provide a novel mechanism through which autophagy can support tumor growth.