Die Rolle Sentrin spezifischer Proteasen in der stabilen Aktivierung von Synovialfibroblasten bei Patienten mit Rheumatoider Arthritis

Im Rahmen dieser Dissertation wurde die Rolle von SENP5 und 7 in der stabilen Aktivierung von Rheumatoid Arthritischen Synovialfibroblasten (RASF) untersucht. Erstmalig konnte eine erhöhte Expression von SUMO-2/3 sowie der SUMO-spezifischen Protease SENP7 in Rheumatoid Arthritischen Synovialfibroblasten und Synovialfibroblasten von hTNFtg-Mäusen nachgewiesen werden. SENP5 wurde ebenfalls im RA-Synovialgewebe detektiert. Neben der nukleären Lokalisation von SENP5/7 in RASF konnte für SENP7 auch eine zytoplasmatische Lokalisation gezeigt werden. TNF-alpha wirkte in murinen wt-SF stimulierend auf die SENP7 Expression. Die Überexpression von SENP5/7 steigerte die Proliferationsraten muriner wt und hTNFtg SF sowie die FASL-induzierte Apoptose in wt SF. Zusätzlich steigerte die Überexpression von SENP7 die FASL-induzierte Apotose in RASF und induzierte die proMMP-9 Expression in wt SF. Die hier gewonnenen Erkenntnisse zeigen erstmalig Bezüge von SENP5/7 zur Rheumatoiden Arthritis

Interaction of SET domains with histones and nucleic acid structures in active chromatin

Changes in the normal program of gene expression are the basis for a number of human diseases. Epigenetic control of gene expression is programmed by chromatin modifications—the inheritable “histone code”—the major component of which is histone methylation. This chromatin methylation code of gene activity is created upon cell differentiation and is further controlled by the “SET” (methyltransferase) domain proteins which maintain this histone methylation pattern and preserve it through rounds of cell division. The molecular principles of epigenetic gene maintenance are essential for proper treatment and prevention of disorders and their complications. However, the principles of epigenetic gene programming are not resolved. Here we discuss some evidence of how the SET proteins determine the required states of target genes and maintain the required levels of their activity. We suggest that, along with other recognition pathways, SET domains can directly recognize the nucleosome and nucleic acids intermediates that are specific for active chromatin regions

Epigenetic modifications in rheumatoid arthritis

Over the last decades, genetic factors for rheumatoid diseases like the HLA haplotypes have been studied extensively. However, during the past years of research, it has become more and more evident that the influence of epigenetic processes on the development of rheumatic diseases is probably as strong as the genetic background of a patient. Epigenetic processes are heritable changes in gene expression without alteration of the nucleotide sequence. Such modifications include chromatin methylation and post-translational modification of histones or other chromatin-associated proteins. The latter comprise the addition of methyl, acetyl, and phosphoryl groups or even larger moieties such as binding of ubiquitin or small ubiquitin-like modifier. The combinatory nature of these processes forms a complex network of epigenetic modifications that regulate gene expression through activation or silencing of genes. This review provides insight into the role of epigenetic alterations in the pathogenesis of rheumatoid arthritis and points out how a better understanding of such mechanisms may lead to novel therapeutic strategies

Epigenetics and rheumatoid arthritis: The role of SENP1 in the regulation of MMP-1 expression

The aggressive phenotype of RA synovial fibroblasts (RASF) is characterised by the increased expression of matrix metalloproteinase (MMP)-1 as well as the small ubiquitin like modifier (SUMO)-1 and decreased expression of SUMO-specific protease SENP1. Since we showed an increased activity of acetyltransferases in this autoimmune disease, we wanted to analyze whether this affects the expression of MMP-1 and can be reversed by the reconstitution of SENP1. In RASF, the acetylation of histone H4 was significantly increased in the distal region of the MMP-1 promoter by 274 +/- 36% compared to OASF. Most interestingly, overexpression of SENP1 in RASF decreased acetylation specifically in this region by 51 +/- 0.5% and globally by 73 +/- 11%. Furthermore, the overexpression of SENP1 resulted in a downregulation of MMP-1 at both the mRNA (58 +/- 7%) and protein levels (28 +/- 6%), significantly reduced the invasiveness of RASF (from 34 +/- 9% to 2 +/- 2%) and led to an accumulation of histone deacetylase 4 (HDAC4) on the MMP-1 promoter (197 +/- 36%). Interestingly, SENP1 failed to modulate the expression of MMP-1 in the cells silenced for HDAC4. This is the first study linking the SUMOylation pathway and the production of MMP-1 to an epigenetic control mechanism mediated through histone acetylation which has a functional consequence for the invasiveness of RASF

Regulation of matrixmetalloproteinase-3 and matrixmetalloproteinase-13 by SUMO-2/3 through the transcription factor NF-κB

OBJECTIVE: Based on previous data that have linked the small ubiquitin-like modifier-1 (SUMO-1) to the pathogenesis of rheumatoid arthritis (RA), we have investigated the expression of the highly homologous SUMO family members SUMO-2/3 in human RA and in the human tumour necrosis factor α transgenic (hTNFtg) mouse model of RA and studied their role in regulating disease specific matrixmetalloproteinases (MMPs). METHODS: Synovial tissue was obtained from RA and osteoarthritis (OA) patients and used for histological analyses as well as for the isolation of synovial fibroblasts (SFs). The expression of SUMO-2/3 in RA and OA patients as well as in hTNFtg and wild type mice was studied by PCR, western blot and immunostaining. SUMO-2/3 was knocked down using small interfering RNA in SFs, and TNF-α induced MMP production was determined by ELISA. Activation of nuclear factor-κB (NF-κB) was determined by a luciferase activity assay and a transcription factor assay in the presence of the NF-κB inhibitor BAY 11-7082. RESULTS: Expression of SUMO-2 and to a lesser extent of SUMO-3 was higher in RA tissues and RASFs compared with OA controls. Similarly, there was increased expression of SUMO-2 in the synovium and in SFs of hTNFtg mice compared with wild type animals. In vitro, the expression of SUMO-2 but not of SUMO-3 was induced by TNF-α. The knockdown of SUMO-2/3 significantly increased the TNF-α and interleukin (IL)-1β induced expression of MMP-3 and MMP-13, accompanied by increased NF-κB activity. Induction of MMP-3 and MMP-13 was inhibited by blockade of the NF-κB pathway. TNF-α and IL-1β mediated MMP-1 expression was not regulated by SUMO-2/3. CONCLUSIONS: Collectively, we show that despite their high homology, SUMO-2/3 are differentially regulated by TNF-α and selectively control TNF-α mediated MMP expression via the NF-κB pathway. Therefore, we hypothesise that SUMO-2 contributes to the specific activation of RASF