Tsc22d3 coding for glucocorticoid-induced leucine zipper (GILZ) was initially identified as a dexamethasoneresponsive gene involved in the control of T lymphocyte activation and apoptosis. However, the physiological role of this molecule and its function in the biological activity of glucocorticoids (GCs) has not been clarified. Here, we demonstrate that GILZ interacts directly with Ras in vitro and in vivo as shown by GILZ and Ras coimmunoprecipitation and colocalization upon PMA activation in primary mouse spleen T lymphocytes and thymus cells. The analysis of GILZ mutants showed that they bound Ras through the tuberous sclerosis complex box (TSC) and, depending on the Ras activation level, formed a trimeric complex with Ras and Raf, which we previously identified as a GILZ binder. As a consequence of these interactions, GILZ diminished the activation of Ras and Raf downstream targets including ERK1/2, AKT/PKB serine/threonine kinase, and retinoblastoma (Rb) phosphorylation and cyclin D1 expression, leading to inhibition of Ras-and Raf-dependent cell proliferation and Ras-induced NIH-3T3 transformation. GILZ silencing resulted in an increase in concanavalin A-induced T cell proliferation and, most notably, inhibition of dexamethasone antiproliferative effects. Together, these findings indicate that GILZ serves as a negative regulator of Ras-and Raf-induced proliferation and is an important mediator of the antiproliferative effect of GCs.

The transcription factor p53 regulates the expression of genes crucial for biological processes such as cell proliferation, metabolism, cell repair, senescence and apoptosis. Activation of p53 also suppresses neoplastic transformations, thereby inhibiting the growth of mutated and/or damaged cells. p53-binding proteins, such as mouse double minute 2 homolog (MDM2), inhibit p53 activation and thus regulate p53-mediated stress responses. Here, we found that long glucocorticoid-induced leucine zipper (L-GILZ), a recently identified isoform of GILZ, activates p53 and that the overexpression of L-GILZ in p53 þ / þ HCT116 human colorectal carcinoma cells suppresses the growth of xenografts in mice. In the presence of both p53 and MDM2, L-GILZ binds preferentially to MDM2 and interferes with p53/MDM2 complex formation, making p53 available for downstream gene activation. Consistent with this finding, L-GILZ induced p21 and p53 upregulated modulator of apoptosis (PUMA) expression only in p53 þ / þ cells, while L-GILZ silencing reversed the anti-proliferative activity of dexamethasone as well as expression of p53, p21 and PUMA. Furthermore, L-GILZ stabilizes p53 proteins by decreasing p53 ubiquitination and increasing MDM2 ubiquitination. These findings reveal L-GILZ as a regulator of p53 and a candidate for new therapeutic anti-cancer strategies for tumors associated with p53 deregulation.

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Psoriasis is a chronic inflammatory disease with a complex pathophysiology and a multigenic background. Autoimmunity and genetic hallmarks couple to confer the disease, which is characterized by chronic plaques (85-90% of all cases) and/or psoriasis arthritis (PsA), and involve the peripheral and sacro-iliac joints, nails, and skeleton. Dissecting the ethiopathogenetic mechanisms of psoriasis and PsA is a major basic research challenge. One important question is whether a single inflammatory mediator can be responsible for the interactive network that forms between immune cells and cytokines in this disease. Despite much progress, no research has yet been able to define a single model to explain the multifaceted pathogenesis of psoriasis and PsA. It is known that both the innate and adaptive immune systems are involved, antigen presenting cells and T lymphocytes play a prominent role, and that the deregulation of the T helper (Th)- 1/Th-2/Th-17/Th-23 axis is directly implicated in disease pathogenesis. Pharmacological therapy for psoriasis has evolved with the development of human knowledge of the disease pathophysiology. Thus, the first "ethiopathogenetic" drugs (e.g., methotrexate, cyclosporin, and alefacept) inhibited T-cell activation directly or targeted co-accessory molecules implicated in T-cell activation. When the mechanism underlying psoriatic inflammation was accepted as a cytokine network disorder, more specific biologics were studied in murine models and were later used clinically. Tumor necrosis factor was the first successful target of cytokine inhibition therapy for psoriasis and PsA (e.g., infliximab, adalimumab, and etanercept). With the recently discovered role for Th-17 in autoimmunity, drugs targeting interleukin-23 (ustekinumab) have become accepted for the pharmacological treatment of psoriasis. The expansion of pharmacological treatment options for psoriasis is not complete. As the knowledge of pathogenetic mechanisms increases, it may be possible to design therapeutic approaches that selectively target the ethiopathogenetic cells or cytokines while sparing the others. In this way, using a more targeted drug therapy may preserve the integrity of the immune system. Thus, one great struggle in treating this complex disease is the challenge to synthesize the "perfect" drug.

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