RasGRP1 and RasGRP3 expression in lymphocytes of rheumatoid arthritis patients
Authors: ML Potier, T Vandhuick, M Hiron, C Derambure, O Boyer, X Le Loët, O Vittecoq, T Lequerré
Journal: Annals of the Rheumatic Diseases (2012)

<h3>Introduction</h3> RasGRP is a member of the CDC25 family of Ras guanyl nucleotide exchange factors. RasGRP1 is expressed in T and B cells whereas RasGRP3 is only expressed in B cells. These proteins are involved in T cell receptor and B cell receptor signalling. Indeed, Ras activation stimulates various effector systems, leading to changes in genes expression which are critical for T or B cell development and activation during the cellular immune response. In previous studies, it has been shown that <i>RasGRP1</i> and <i>RasGRP3</i> were dysregulated in peripheral blood mononuclear cells (PBMC) and synovium from rheumatoid arthritis (RA) patients leading to the question of <i>RasGRP1</i> and <i>RasGRP3</i> involvement in RA pathophysiology. <h3>Objectives</h3> To measure <i>RasGRP1</i> and <i>RasGRP3</i> gene expression level in B and T cells from both RA and spondylarthropathy (SpA) patients compared to healthy controls (HC) in order to confirm their dysregulation in RA. <h3>Methods</h3> PBMC were isolated from whole venous blood of 24 RA patients (53±15 years old (yo)) with active disease (DAS28=4.98±1.32), 18 patients with active SpA (45±12 yo; BASDAI=55.2±16.1/100) and 19 HC (32±9 yo). After negative cell selection, total RNA from B ant T cells were extracted. Immunofluorescence staining was performed to check the cell purity by flow cytometry. <i>RasGRP1</i> and <i>RasGRP3</i> expression levels were measured by qRT-PCR and their transcripts were compared by PCR. <h3>Results</h3> <i>RasGRP1</i> was more expressed in T cells than in B cells (x 3.5; p&lt;0.0001) while <i>RasGRP3</i> was more expressed in B cells than in T cells (x 8; p&lt;0.0001). Moreover, <i>RasGRP1</i> was significantly overexpressed in T cells from RA (p&lt;0.05) and SpA (p&lt;0.005) patients in comparison with those from HC. Surprisingly, <i>RasGRP1</i> was also significantly overexpressed in B cells from RA patients (p&lt;0.05) in comparison with those from HC. <i>RasGRP3</i> expression level was similar in RA or SpA patients and HC whatever the cellular lineage (B and T cells). Moreover, <i>RasGRP1</i> expression level in T cells was inversely correlated with the disease activity measured by DAS28 in RA patients (p&lt;0.05). Otherwise, two <i>RasGRP1</i> variants are expressed in T cells from RA patients compared to HC. Moreover, a minority of RA patients have <i>RasGRP3</i> full length transcript in B cells. <h3>Conclusions</h3> This study has shown for the first time the overexpression, in human, of <i>RasGRP1</i> in T cells and of <i>RasGRP3</i> in B cells. Moreover, <i>RasGRP1</i> is overexpressed in T and B cells from RA patients and only in T cells from SPA patients. Furthermore, the authors identified differents <i>RasGRP1</i> variants in B and T cells from RA patients compared to HC; these variants correspond to deletions of exons. Otherwise, the inverse correlation between <i>RasGRP1</i> expression in T cells from RA patients and disease activity score confirms the hypothesis of RasGRP1 anti-inflammatory role. In addition, expression of RasGRP1 in B cells induces apoptosis of these one. Therefore, specific overexpression of <i>RasGRP1</i> in B and T cells opens broad perspectives for research and therapy.