RING finger protein 11 (RNF11), a negative regulator of NF-κB signaling pathway, colocalizes with α-synuclein and is sequestered in Lewy bodies in Parkinson’s disease (PD). Since persistent NF-κB activation is reported in PD, in this report we investigated if RNF11 expression level is correlated to activated NF-κB in PD. We examined RNF11 expression levels in correlation to phospho-p65, a marker for activated NF-κB, in control and PD brain tissue from cerebral cortex. In addition we performed double immunofluorescence labeling experiments to confirm this correlation. Our investigations demonstrated that the neuronal RNF11 expression was down-regulated in PD and was usually associated with increased expression of phospho-p65. Double labeling confirmed that loss of neuronal RNF11 was linked to increased phospho-p65 expression, suggesting that persistent presence of NF-κB activation could be due to decreased levels of its negative regulator. Our data exemplifies the relevance of RNF11 and persistent NF-κB activation in PD.

Activation of innate and adaptive immune responses is tightly regulated, as insufficient activation could result in defective clearance of pathogens, while excessive activation might lead to lethal systemic inflammation or autoimmunity. A20 functions as a negative regulator of innate and adaptive immunity by inhibiting NF-κB activation. A20 mediates its inhibitory function in a complex with other proteins including RNF11 and Itch, both E3 ubiquitin ligases and TAX1BP1, an adaptor protein. Since NF-κB has been strongly implicated in various neuronal functions, we predict that its inhibitor, the A20 complex, is also present in the nervous system. In efforts to better understand the role of A20 complex and NF-κB signaling pathway, we determined regional distribution of A20 mRNA as well as protein expression levels and distribution of RNF11, TAX1BP1 and Itch, in different brain regions. The distribution of TRAF6 was also investigated since TRAF6, also an E3 ligase, has an important role in NF-κB signaling pathway. Our investigations, for the first time, describe and demonstrate that the essential components of the A20 ubiquitin-editing complex are present and mainly expressed in neurons. The A20 complex components are also differentially expressed throughout the human brain. This study provides useful information about region specific expression of the A20 complex components that will be invaluable while determining the role of NF-κB signaling pathway in neuronal development and degeneration.