Immunoproteasomes control activation of innate immune signaling and microglial function.

Microglia are the resident immune cells of the central nervous system (CNS) and play a major role in the regulation of brain homeostasis. To maintain their cellular protein homeostasis, microglia express standard proteasomes and immunoproteasomes (IP), a proteasome isoform that preserves protein homeostasis also in non-immune cells under challenging conditions. The impact of IP on microglia function in innate immunity of the CNS is however not well described. Here, we establish that IP impairment leads to proteotoxic stress and triggers the unfolded and integrated stress responses in mouse and human microglia models. Using proteomic analysis, we demonstrate that IP deficiency in microglia results in profound alterations of the ubiquitin-modified proteome among which proteins involved in the regulation of stress and immune responses. In line with this, molecular analysis revealed chronic activation of NF-κB signaling in IP-deficient microglia without further stimulus. In addition, we show that IP impairment alters microglial function based on markers for phagocytosis and motility. At the molecular level IP impairment activates interferon signaling promoted by the activation of the cytosolic stress response protein kinase R. The presented data highlight the importance of IP function for the proteostatic potential as well as for precision proteolysis to control stress and immune signaling in microglia function.

Immunoproteasome deficiency alters microglial cytokine response and improves cognitive deficits in Alzheimer's disease-like APPPS1 mice.

The immunoproteasome (iP) represents a specialized type of proteasomes, which plays an important role in the clearance of oxidant-damaged proteins under inflammatory and pathological conditions determining the outcome of various diseases. In Alzheimer's disease (AD)-like APPPS1 mice Aß-deposition is paralleled by iP upregulation, most likely mediated through type I interferon induction. To define the impact of increased iP expression we crossed APPPS1 mice with mice deficient in the iP subunit LMP7 resulting in impaired iP function. While LMP7 deficient APPPS1 mice showed no major change in cerebral Aß-pathology, we observed an altered cytokine response in microglia isolated from LMP7 deficient APPPS1 mice compared to LMP7 expressing APPPS1 control mice. The altered microglial cytokine profile upon iP deficiency in the presence of extracellular Aß-pathology was associated with an improvement of Aß-associated cognitive deficits typically present in APPPS1 mice. Our findings suggest a role for iP in the regulation of the innate immune response towards extracellular Aß-pathology and indicate that inhibition of iP function can modulate the cognitive phenotype upon overexpression of Aß.

TCF11/Nrf1-Mediated Induction of Proteasome Expression Prevents Cytotoxicity by Rotenone.

AIMS: Precise regulation of cellular protein degradation is essential for maintaining protein and redox homeostasis. The ubiquitin proteasome system (UPS) represents one of the major degradation machineries, and UPS disturbances are strongly associated with neurodegeneration. We have previously shown that the transcription factor TCF11/Nrf1 induces antioxidant response element-mediated upregulation of UPS components in response to proteotoxic stress. Knockout of TCF11/Nrf1 is embryonically lethal, and therefore, the present investigation describes the role of oxidative stress in regulating TCF11/Nrf1-dependent proteasome expression in a model system relevant to Parkinson's disease. RESULTS: Using the human dopaminergic neuroblastoma cell line SH-SY5Y and mouse nigrostriatal organotypic slice cultures, gene and protein expression analysis and functional assays revealed oxidative stress is induced by the proteasome inhibitor epoxomicin or the mitochondrial complex I inhibitor rotenone and promotes the upregulation of proteasome expression and function mediated by TCF11/Nrf1 activation. In addition, we show that these stress conditions induce the unfolded protein response. TCF11/Nrf1, thus, has a cytoprotective function in response to oxidative and proteotoxic stress. Innovation and Conclusion: We here demonstrate that adaption of the proteasome system in response to oxidative stress is dependent on TCF11/Nrf1 in this model system. We conclude that TCF11/Nrf1, therefore, plays a vital role in maintaining redox and protein homeostasis. This work provides a vital insight into the molecular mechanisms of neurodegeneration due to oxidative stress by rotenone, and further studies investigating the role of TCF11/Nrf1 in the human condition would be of considerable interest. Antioxid. Redox Signal. 25, 870-885.

Tumour angiogenesis in Epstein-Barr virus-associated post-transplant smooth muscle tumours.

Epstein-Barr virus (EBV)-associated post-transplant smooth muscle tumours (PTSMT), are rare complications following organ/stem cell transplantation. Despite the mainly benign behaviour of PTSMT, alternative therapies are needed for those patients with progressive tumours. In tumours not approachable by surgery or reduction of immunosuppression, the angiogenic microenvironment might be a potential target of therapy, an approach that is well utilised in other soft tissue neoplasms. In a previous study, we evaluated the expression of EBV-related genes and the microRNA profile in PTSMT, but so far the characteristics of angiogenesis in PTSMT are not known. Therefore, the aim of this study was to evaluate the expression pattern of angiogenesis-related genes in PTSMT, in order to identify potential target molecules for anti-angiogenic therapy.PTSMT (n = 5 tumours) were compared with uterine leiomyomas (n = 7). Analyses included real-time PCR of 45 angiogenesis-associated genes, immunohistochemistry (CD31, prostaglandin endoperoxide synthase 1/PTGS1) and assessment of tumour vascularisation by conventional histopathology.PTSMT showed similar or fewer vessels than leiomyomas. Of the genes under investigation, 23 were down-deregulated (pro-angiogenic and some anti-angiogenic factors) and five were up-regulated (e.g. PTGS1 which is expressed at very low levels in leiomyomas but moderately higher levels in PTSMT).In summary, no particular target molecule could be identified, because tumour angiogenesis in PTSMT is characterised by low levels of major pro-angiogenic factors and there is no prominent increase in tumour vascularisation. EBV can induce angiogenesis via its viral late membrane protein 1 (LMP1) but PTSMT frequently do not express LMP1, which could be an explanation why, despite EBV infection, PTSMT show no exaggerated tumour angiogenesis.

MicroRNA expression in Epstein-Barr virus-associated post-transplant smooth muscle tumours is related to leiomyomatous phenotype.

Epstein-Barr virus (EBV)-associated post-transplant smooth muscle tumours (PTSMT) are rare complications. In our previous molecular analysis, we have evaluated the expression of regulatory microRNA which are known to be EBV-related (miR-146a and miR-155) but found no deregulation in PTSMT. In this current analysis, we aimed to characterize the expression profiles of several hundred microRNA. Tissue samples from PTSMT and uterine leiomyomas were analysed by quantitative real-time PCR for the expression of 365 mature microRNA. PTSMT and leiomyomas share a highly similar microRNA profile, e.g. strong expression of miR-143/miR-145 cluster and low expression of miR-200c. Among EBV-related microRNA (miR-10b, miR-21, miR-29b, miR-34a, miR-127, miR-146a, miR-155, miR-200b, miR-203 and miR-429) only miR-10b and miR-203 were significantly deregulated. The expression pattern of microRNA in PTSMT is not associated with EBV infection but reflects the leiomyomatous differentiation of the tumour cells.

Congenital phimosis in patients with and without lichen sclerosus: distinct expression patterns of tissue remodeling associated genes.

PURPOSE: Lichen sclerosus is a potentially important factor in the ongoing debate concerning the pathology of persistent congenital phimosis. We assessed the molecular differences of congenital phimosis in boys with and without lichen sclerosus compared to age matched boys with fully retractable foreskins to gain more insight into the pathogenesis of fibrotic remodeling of the prepuce. MATERIALS AND METHODS: A total of 150 boys were circumcised in a prospective study between 2007 and 2009. Using target gene specific preamplification and quantitative real-time polymerase chain reaction based low density arrays, we measured the mRNA expression of 45 tissue remodeling associated genes in foreskins of boys with absolute phimosis and lichen sclerosus (8 patients) and those of an age matched group of boys with phimosis but no lichen sclerosus (8), as well as a control group with foreskins without delimitable changes (6). Complementary protein expression and inflammatory infiltrates were assessed by immunohistochemical analysis. RESULTS: Cellular composition, inflammatory infiltrate and microenvironment as seen in histologically proven lichen sclerosis differed significantly from the other groups. In particular, lichen sclerosis was characterized by over expression of bone morphogenetic protein 2 and its corresponding receptor, matrix metalloproteinases 1 and 9 and tissue inhibitor of metalloproteinases 1, cytokine chemokine ligands 5 (RANTES) and interleukin 4, and transforming growth factor-ß2 and its corresponding receptor. There were no major molecular differences between specimens from boys with congenital phimosis without signs of lichen sclerosis and controls. CONCLUSIONS: Distinct expression patterns of tissue remodeling associated genes are evident in boys with congenital phimosis and lichen sclerosis, while congenital phimosis without lichen sclerosis represents a physiological condition.