Identification of New, Functionally Relevant Mutations in the Coding Regions of the Human Fos and Jun Proto-Oncogenes in Rheumatoid Arthritis Synovial Tissue.

René Huber,Sandra Augsten,Peter Ahnert,Thorsten Eidner,Roland Zell,Bruno Stuhlmüller,Hansjörg Thude,Holger Kirsten,Raimund W Kinne,Axel Stelzner

doi:10.3390/life11010005

Abstract

In rheumatoid arthritis (RA), the expression of many pro-destructive/pro-inflammatory proteins depends on the transcription factor AP-1. Therefore, our aim was to analyze the presence and functional relevance of mutations in the coding regions of the AP-1 subunits of the fos and jun family in peripheral blood (PB) and synovial membranes (SM) of RA and osteoarthritis patients (OA, disease control), as well as normal controls (NC). Using the non-isotopic RNAse cleavage assay, one known polymorphism (T252C: silent; rs1046117; present in RA, OA, and NC) and three novel germline mutations of the cfos gene were detected: (i) C361G/A367G: Gln121Glu/Ile123Val, denoted as “fos121/123”; present only in one OA sample; (ii) G374A: Arg125Lys, “fos125”; and (iii) C217A/G374A: Leu73Met/Arg125Lys, “fos73/125”, the latter two exclusively present in RA. In addition, three novel somatic cjun mutations (604–606ΔCAG: ΔGln202, “jun202”; C706T: Pro236Ser, “jun236”; G750A: silent) were found exclusively in the RA SM. Tansgenic expression of fos125 and fos73/125 mutants in NIH-3T3 cells induced an activation of reporter constructs containing either the MMP-1 (matrix metalloproteinase) promoter (3- and 4-fold, respectively) or a pentameric AP-1 site (approximately 5-fold). Combined expression of these two cfos mutants with cjun wildtype or mutants (jun202, jun236) further enhanced reporter expression of the pentameric AP-1 construct. Finally, genotyping for the novel functionally relevant germline mutations in 298 RA, 288 OA, and 484 NC samples revealed no association with RA. Thus, functional cfos/cjun mutants may contribute to local joint inflammation/destruction in selected patients with RA by altering the transactivation capacity of AP-1 complexes.

Highlights

Rheumatoid arthritis (RA), the most common rheumatic disease [1], is characterized by chronic inflammation and the destruction of cartilage and bone in multiple joints [2]
activator protein (AP-)1 appears to be strongly involved in proinflammatory and pro-destructive processes [7] and represents one of the transcription factors contributing to the pathogenesis of RA [11]
3 novel mutations of cfos were identified, all located in the transactivation domain of the protein

Summary

Introduction

Rheumatoid arthritis (RA), the most common rheumatic disease [1], is characterized by chronic inflammation and the destruction of cartilage and bone in multiple joints [2]. The fos and jun family genes can be classified as “immediate-early response” genes, as they are rapidly induced by a variety of activating agents and show a very short half-life of only a few minutes [12]. They can be regarded as markers of recent cell activation, e.g., in activated RA FLS [13], with clearly different biological activities of individual fos/jun family members [14]. In specific situations, an activating capacity of JunB (e.g., in combination with Fos-related antigen 1 in collagen-induced arthritis [16]) and JunD (e.g., in macrophage activation during glumerulonephritis [17]) has been described

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Conclusion