Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement
The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.
Activation of Scleroderma-Like Signaling Pathway: Importance of PDGFR-NADPH Oxidase Complex and Receptor Integrity
Spadoni1, Tatiana, Svegliati1, Silvia, De Gennaro1, Lucia, Moroncini1, Gianluca, Avvedimento2, Enrico, Gabrielli1, Armando
Systemic sclerosis (SSc) is an autoimmune disease characterized by widespread vascular changes and progressive fibrosis of the skin and internal organs. We have demonstrated the presence of stimulatory immunoglobulins binding to PDGF receptor in serum of SSc patients. These autoantibodies from SSc patients show functional agonistic activity as demonstrated by induction of tyrosine phosphorylation and production of reactive oxygen species (ROS). Moreover isolated IgG from SSc patients induced myofibroblast conversion and type I collagen expression in normal human fibroblasts. The scope of this study is to elucidate the cellular and molecular changes elicited by the PDGFR autoantibodies in normal cells and to assess the molecules engaged in the membrane complex recognised by SSc IgG and their role in the generation of PDGFR signalling and ROS.
The interaction between SSc IgG, PDGFR and the subunits of the NADPH oxidase complex was evaluated by immunoprecipitation of extracts from stimulated and unstimulated fibroblasts and HeLa cells, constitutively devoid of PDGFR, stably transfected with different alpha and beta PDGFR recombinant DNA constructs, with purified SSc IgG and monoclonal anti-PDGFR antibodies. Immunocomplexes were characterized by specific immunoblotting with anti PDGFR, Nox-2 and Ha-Ras antibodies. The stably trasfected cell lines were used to determine the regions of PDGFR recognized by the different IgG and the importance of receptor integrity on signalling transduction.
We have found that SSc IgGs from several different patients selectively immunoprecipitate gp91 phox, the NADPH oxidase Nox-2 subunit, in addition to PDGFR. SSc IgG stabilized a membrane-associated complex made of PDGFR and NADPH oxidase with the consequence of lengthening ROS/Ras activation. The recombinant receptors devoid of the cytoplasmatic domain are bound to gp91 but the lack of tyrosine phosphorylation sites impairs the transduction of the signalling.
SSc IgGs interact with the extracellular part of the PDGFR and prolong the formation of a stable PDGFR/NADPH oxidase complex on the cell membrane, leading to a persistent ROS production and appearance of the disease pathological signatures.
To cite this abstract, please use the following information:
Spadoni, Tatiana, Svegliati, Silvia, De Gennaro, Lucia, Moroncini, Gianluca, Avvedimento, Enrico, Gabrielli, Armando; Activation of Scleroderma-Like Signaling Pathway: Importance of PDGFR-NADPH Oxidase Complex and Receptor Integrity [abstract]. Arthritis Rheum 2009;60 Suppl 10 :1816