The parkin-coregulated gene product PACRG promotes TNF signaling by stabilizing LUBAC

Abstract

The Parkin-coregulated gene (PACRG), which encodes a protein of unknown function, shares a bidirectional promoter with Parkin (PRKN), which encodes an E3 ubiquitin ligase. Because PRKN is important in mitochondrial quality control and protection against stress, we tested whether PACRG also affected these pathways in various cultured human cell lines and in mouse embryonic fibroblasts. PACRG did not play a role in mitophagy but did play a role in tumor necrosis factor (TNF) signaling. Similarly to Parkin, PACRG promoted nuclear factor κB (NF-κB) activation in response to TNF. TNF-induced nuclear translocation of the NF-κB subunit p65 and NF-κB–dependent transcription were decreased in PACRG-deficient cells. Defective canonical NF-κB activation in the absence of PACRG was accompanied by a decrease in linear ubiquitylation mediated by the linear ubiquitin chain assembly complex (LUBAC), which is composed of the two E3 ubiquitin ligases HOIP and HOIL-1L and the adaptor protein SHARPIN. Upon TNF stimulation, PACRG was recruited to the activated TNF receptor complex and interacted with LUBAC components. PACRG functionally replaced SHARPIN in this context. In SHARPIN-deficient cells, PACRG prevented LUBAC destabilization, restored HOIP-dependent linear ubiquitylation, and protected cells from TNF-induced apoptosis. This function of PACRG in positively regulating TNF signaling may help to explain the association of PACRG and PRKN polymorphisms with an increased susceptibility to intracellular pathogens.

Chain reactions: molecular mechanisms of RBR ubiquitin ligases

“…Interestingly, the HOIP UBA does not bind ubiquitin [ 27 ], but instead interacts with ubiquitin-like (UBL) domains from other LUBAC subunits HOIL-1L and SHARPIN, which release autoinhibition of HOIP [ 51–54 ]. Recently the parkin coregulated gene (PACRG) product was identified as a novel LUBAC component, which interacts with LUBAC via the HOIP UBA and can functionally compensate for loss of SHARPIN from the complex [ 55 ]. As PACRG does not have a UBL, it is unclear how this interaction occurs, and whether PACRG represents an additional LUBAC component or replaces one of the cofactors HOIL-1L or SHARPIN in specific sub-complexes.…”

Different methylation signatures at diagnosis in patients with high-risk myelodysplastic syndromes and secondary acute myeloid leukemia predict azacitidine response and longer survival

“…The PACRG gene encodes a protein that forms a large molecular complex with chaperones. It has recently been described that the PACRG protein plays an important role in tumor necrosis factor (TNF) signaling, and this function of PACRG in positively regulating TNF signaling may help to explain the association of PACRG polymorphisms with increased susceptibility to intracellular pathogens [45]. Agirre et al [46] studied the role of promoter hypermethylation in the regulation of PACRG expression in different tumour cell lines and primary patient samples and demonstrated that abnormal methylation resulted in downregulation of PACRG gene expression.…”

The transcriptome-wide association search for genes and genetic variants which associate with BMI and gestational weight gain in women with type 1 diabetes

“…In C. elegans PACRG mutants have reduced insulin signaling. Also, PCARG plays a key role in the regulation of mitophagy (Stephenson et al 2018 ) and ubiquitynylation (Loucks et al 2016 ), its knockout leads to defective NFκB signaling (Meschede et al 2020 ) and CHOP upregulation (Han et al 2017 ), which in adipose tissue result in increased proinflammatory macrophage polarization (M1) and insulin resistance (Suzuki et al 2017 ). Thus, we note that PACRG is also involved in ER stress.…”