The HECT E3 ubiquitin ligase NEDD4 interacts with and ubiquitinates SQSTM1 for inclusion body autophagy

Abstract

Our previous studies have shown that the HECT E3 ubiquitin ligase NEDD4 interacts with LC3 and is required for starvation and rapamycin-induced activation of autophagy. Here, we report that NEDD4 directly binds to SQSTM1 via its HECT domain and polyubiquitylates SQSTM1. This ubiquitylation is through K63 conjugation and is not involved in proteasomal degradation. Mutational analysis indicates that NEDD4 interacts with and ubiquitylates the PB1 domain of SQSTM1. Depletion of NEDD4 or overexpression of the ligase-defective mutant of NEDD4 induced accumulation of aberrant enlarged SQSTM1-positive inclusion bodies that are co-localized with the endoplasmic reticulum (ER) marker CANX, suggesting that the ubiquitylation functions in the SQSTM1-mediated biogenic process in inclusion body autophagosomes. Taken together, our studies show that NEDD4 is an autophagic E3 ubiquitin ligase that ubiquitylates SQSTM1, facilitating SQSTM1-mediated inclusion body autophagy.

Molecular mechanisms of Streptococcus pneumoniae ‐targeted autophagy via pneumolysin, Golgi‐resident Rab41, and Nedd4‐1‐mediated K63‐linked ubiquitination

“…These results suggest that the PB1 domain is involved in oligomerisation of p62 and in enhancement of p62 and LC3 recruitment to PCV (or PcAV). These data are supported by a report showing that the PB1 domain is involved in binding of Nedd4-1 to p62 and that K7 of p62 is a major NEDD4 ubiquitination site (Lin et al, 2017).…”

“…The HECT E3 ligases Nedd4-1 (Lin et al, 2017;Sun et al, 2017) and Nedd4-2 (Nedd4L) have also been associated with targeted autophagy (Lin et al, 2017;Sun et al, 2017), although Platta et al reported that Nedd4-1 ubiquitinates Beclin-1 through K11 and is involved in the suppression of autophagy (Platta, Abrahamsen, Thoresen, & Stenmark, 2012). Therefore, we investigated the roles of Nedd4-1 in the regulation of selective autophagy in S. pneumoniae-infected cells using Nedd4-1-deficient MEFs and found that Nedd4-1 plays a pivotal role in K63Ub decoration and efficient formation of PcAV.…”

PPARγ induces NEDD4 gene expression to promote autophagy and insulin action

“…NEDD4 mediates K6‐ and K27‐linked ubiquitination of BECN1, thereby sustaining the stability of BECN1 in turn to increase autophagy . In addition, NEDD4 directly interacts with the PB1 domain of SQSTM1, leading to the ubiquitination of SQSTM1 and facilitating autophagy . Moreover, LC3 functions as an activator to interact with NEDD4, thus enhancing autophagy through increased SQSTM1 ubiquitination .…”

Emerging roles of HECT‐type E3 ubiquitin ligases in autophagy regulation

“…). NEDD4‐1 polyubiquitylates p62 through K63 conjugation and is indispensable for its function in inclusion body autophagy (Lin et al ., ).…”

“…Along with its closely related homolog NEDD4‐2, NEDD4‐1 plays a crucial role in the regulation of electrolyte homeostasis by controlling the surface abundance of the epithelial Na + channel (Staub et al ., ). Though some controversial findings have been reported on the contribution of NEDD4‐1 to autophagy regulation, the majority of available experimental evidence seems to support a promoting function in basal and starvation‐induced autophagy as well as mitophagy (Table ) (Lin et al ., ; Pei et al ., ; Sun et al ., ). In addition, similarly to SMURF1, NEDD4‐1 contributes to killing of intracellular Mtb, Lm, and S. pneumoniae during bacterial infection (Pei et al ., ; Ogawa et al ., ).…”