ARRDC1 and ARRDC3 act as tumor suppressors in renal cell carcinoma by facilitating YAP1 degradation.

The α-arrestins domain-containing 1 and 3 (ARRDC1 and ARRDC3) are two members of the α-arrestins family. Yes-associated protein 1 (YAP1) is a key downstream transcription co-activator of the Hippo pathway essential for cancer initiation, progression, or metastasis in clear cell renal cell carcinoma (ccRCC). The aim of this work was to elucidate the role of the α-arrestins in ccRCC tumorigenesis by identifying molecular interacting factors and exploring potential mechanisms. In this study, we identified YAP1 as a novel ARRDC3 interacting protein in RCC cells through tandem affinity purification and mass spectrometry. We confirmed that ARRDC1 and ARRDC3, but not other α-arrestin family proteins, interact with YAP1. Binding of ARRDC1/3 to YAP1 is mediated through the WW domains of YAP1 and the PPXY motifs of ARRDC1/3. Functional analysis of ARRDC1/3 by lentiviral shRNA revealed a role for ARRDC1/3 in suppression of cell growth, migration, invasion and epithelial-mesenchymal transition in ccRCC cells, and these effects were mediated, at least in part, through YAP1. Mechanically, ARRDC1/3 negatively regulates YAP1 protein stability by facilitating E3 ubiquitin ligase Itch-mediated ubiquitination and degradation of YAP1. Moreover, ARRDC1/3 mRNA levels were significantly downregulated in ccRCC specimens. A negative correlation was identified between ARRDC3 and YAP1 expression in ccRCC specimens by immunohistochemistry. This study revealed a novel mechanism for ARRDC1/3 in the regulation of YAP1 stability and provided insight in understanding the relationship between ARRDC1/3 downregulation and aberrant Hippo-YAP1 pathway activation in ccRCC.