Human RNF34 blocking peptide

Background/Aims: To identify the regulator of nucleotide binding oligomerization domain-containing protein 1 (NOD1) and its regulatory function. Methods and Results: We performed a yeast two-hybrid screening assay and identified the E3 ligase RNF34 as a candidate partner of NOD1. Using co-immunoprecipitation (co-IP) and glutathione S transferase (GST)-pull down assays, we further confirmed that RNF34 is associated with NOD1. Western blotting showed that RNF34 downregulated the stability of NOD1 and promoted its ubiquitination. Functional analysis demonstrated that RNF34 overexpression inhibited NOD1-dependent activation of nuclear factor-kappa B (NF-kappa B), whereas knockdown of RNF34 using small interfering RNA increased NF-kappa B activation following stimulation from NOD1 overexpression or transfection of y-D-glutamyl-meso-diaminopimelic acid. Conclusion: These findings confirm that RNF34 is a negative regulator of the NOD1 pathway through direct interaction and ubiquitination of NOD1, and suggest a novel regulatory mechanism of NOD1. Copyright (C) 2014 S. Karger AG, Basel

Viral infection triggers the formation of mitochondrial antiviral signaling protein (MAVS) aggregates, which potently promote immune signaling. Autophagy plays an important role in controlling MAVS-mediated antiviral signaling; however, the exact molecular mechanism underlying the targeted autophagic degradation of MAVS remains unclear. Here, we investigated the mechanism by which RNF34 regulates immunity and mitophagy by targeting MAVS. RNF34 binds to MAVS in the mitochondrial compartment after viral infection and negatively regulates RIG-I-like receptor (RLR)-mediated antiviral immunity. Moreover, RNF34 catalyzes the K27-/K29-linked ubiquitination of MAVS at Lys 297, 311, 348, and 362 Arg, which serves as a recognition signal for NDP52-dependent autophagic degradation. Specifically, RNF34 initiates the K63- to K27-linked ubiquitination transition on MAVS primarily at Lys 311, which facilitates the autophagic degradation of MAVS upon RIG-I stimulation. Notably, RNF34 is required for the clearance of damaged mitochondria upon viral infection. Thus, we elucidated the mechanism by which RNF34-mediated autophagic degradation of MAVS regulates the innate immune response, mitochondrial homeostasis, and infection.