Abstract: The RING domain-containing protein RING finger protein 11 (RNF11) is a member of the A20 ubiquitin-editing protein complex and modulates peripheral NF-κB signaling. RNF11 is robustly expressed in neurons and colocalizes with a population of α-synuclein-positive Lewy bodies and neurites in Parkinson disease patients. The NF-κB pathway has an important role in the vertebrate nervous system, where the absence of NF-κB activity during development can result in learning and memory deficits, whereas chronic NF-κB activation is associated with persistent neuroinflammation. We examined the functional role of RNF11 with respect to canonical NF-κB signaling in neurons to gain understanding of the tight association of inflammatory pathways, including NF-κB, with the pathogenesis of neurodegenerative diseases.
Abstract: 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.
Abstract: Restless Legs Syndrome (RLS), first chronicled by Willis in 1672 and described in more detail by Ekbom in 1945, is a prevalent sensorimotor neurological disorder (5%-10% in the population) with a circadian predilection for the evening and night. Characteristic clinical features also include a compelling urge to move during periods of rest, relief with movement, involuntary movements in sleep (viz., periodic leg movements of sleep), and fragmented sleep. Although the pathophysiology of RLS is unknown, dopaminergic neurotransmission and deficits in iron availability modulate expressivity. Genome-wide association studies have identified a polymorphism in an intronic region of the BTBD9 gene on chromosome 6 that confers substantial risk for RLS. Here, we report that loss of the Drosophila homolog CG1826 (dBTBD9) appreciably disrupts sleep with concomitant increases in waking and motor activity. We further show that BTBD9 regulates brain dopamine levels in flies and controls iron homeostasis through the iron regulatory protein-2 in human cell lines. To our knowledge, this represents the first reverse genetic analysis of a "novel" or heretofore poorly understood gene implicated in an exceedingly common and complex sleep disorder and the development of an RLS animal model that closely recapitulates all disease phenotypes.
Abstract: Microglia are resident macrophages in the central nervous system (CNS) that play a major role in neuroinflammation and pathogenesis of several neurodegenerative diseases. Upon activation, microglia releases a multitude of pro-inflammatory factors that initiate and sustain an inflammatory response by activating various signalling pathways, including the NF-κB pathway in a feed forward cycle. In microglial cells, activation of NF-κB signalling is normally transient, while sustained NF-κB activation is associated with persistent neuroinflammation. RING finger protein 11 (RNF11), in association with A20 ubiquitin-editing complex, is one of the key negative regulators of NF-κB signalling pathway in neurons. In this study, we have demonstrated and confirmed this role of RNF11 in microglia, the immune cells of the CNS. Coimmunoprecipitation experiments showed that RNF11 and A20 interact in a microglial cell line, suggesting the presence of A20 ubiquitin-editing protein complex in microglial cells. Next, using targeted short hairpin RNA (shRNA) knockdown and over-expression of RNF11, we established that RNF11 expression levels are inversely related to NF-κB activation, as evident from altered expression of NF-κB transcribed genes. Moreover our studies, illustrated that RNF11 confers protection against LPS-induced cell cytotoxicity. Thus our investigations clearly demonstrated that microglial RNF11 is a negative regulator of NF-κB signalling pathway and could be a strong potential target for modulating inflammatory responses in neurodegenerative diseases.
