Phosphatase of Regenerating Liver-1 (PRL-1) Regulates Actin Dynamics During Immunological Synapse Assembly and T Cell Effector Function

The regulatory role of most dual specific phosphatases during T cell activation remains unknown. Here, we have studied the expression and function of phosphatases of regenerating liver (PRLs: PRL-1, PRL-2, and PRL-3) during T cell activation, as well as, the dynamic delivery of PRL-1 to the Immunological Synapse (IS). We found that T cell activation downregulates the expression of PRL-2, resulting in an increased PRL-1/PRL-2 ratio. PRL-1 redistributed at the IS in two stages: Initially, it was transiently accumulated at scanning membranes enriched in CD3 and actin, and at later times, it was delivered at the contact site from pericentriolar, CD3ζ-containing, vesicles. Once at the established IS, PRL-1 distributed to LFA-1 and CD3ε sites. Remarkably, PRL-1 was found to regulate actin dynamics during IS assembly and the secretion of IL-2. Moreover, pharmacological inhibition of the catalytic activity of the three PRLs reduced the secretion of IL-2. These results provide evidence indicating a regulatory role of PRL-1 during IS assembly and highlight the involvement of PRLs in immune responses by mature T cells.

mRNA profiling identifies low levels of phosphatases dual‐specific phosphatase‐7 (DUSP7) and cell division cycle‐25B (CDC25B) in patients with early arthritis

Phosphotyrosine phosphatases (PTPs) control phosphorylation levels and, consequently, regulate the output of intracellular signalling networks in health and disease. Despite the high number of PTPs expressed in CD4 T cells and their involvement in autoimmunity, information about the expression profile of PTPs in these cells has not been obtained in patients diagnosed with autoimmune diseases. Here, we compare the expression profile of PTPs in CD4 T cells of healthy volunteers and patients submitted to an early arthritis clinic, due to suspicion of rheumatoid arthritis, an autoimmune disease mediated by CD4 T cells. We found lower transcript levels of the mitogen-activated protein kinase (MAPK) phosphatase dual-specific phosphatase-7 (DUSP7) and the cell division cycle-25B (CDC25B) in T cells of patients. While the low expression level of DUSP7 was restricted to patients with positive rheumatoid factor and anti-citrullinated protein antibodies, the altered expression of CDC25B correlated with the activity of the disease. Low levels of CDC25B might contribute to the progression of the autoimmune arthritis and/or might be consequence of the inflammatory environment in the active disease. The possible role of DUSP7 and CDC25B as biomarkers of the disease in clinical protocols is discussed.