Teriflunomide attenuates immunopathological changes in the dark agouti rat model of experimental autoimmune encephalomyelitis.

Teriflunomide is an oral disease-modifying therapy recently approved in several locations for relapsing-remitting multiple sclerosis. To gain insight into the effects of teriflunomide, immunocyte population changes were measured during progression of experimental autoimmune encephalomyelitis in Dark Agouti rats. Treatment with teriflunomide attenuated levels of spinal cord-infiltrating T cells, natural killer cells, macrophages, and neutrophils. Teriflunomide also mitigated the disease-induced changes in immune cell populations in the blood and spleen suggesting an inhibitory effect on pathogenic immune responses.

Opposing effects of PKCtheta and WASp on symmetry breaking and relocation of the immunological synapse.

The immunological synapse (IS) is a junction between the T cell and antigen-presenting cell and is composed of supramolecular activation clusters (SMACs). No studies have been published on naive T cell IS dynamics. Here, we find that IS formation during antigen recognition comprises cycles of stable IS formation and autonomous naive T cell migration. The migration phase is driven by PKCtheta, which is localized to the F-actin-dependent peripheral (p)SMAC. PKCtheta(-/-) T cells formed hyperstable IS in vitro and in vivo and, like WT cells, displayed fast oscillations in the distal SMAC, but they showed reduced slow oscillations in pSMAC integrity. IS reformation is driven by the Wiscott Aldrich Syndrome protein (WASp). WASp(-/-) T cells displayed normal IS formation but were unable to reform IS after migration unless PKCtheta was inhibited. Thus, opposing effects of PKCtheta and WASp control IS stability through pSMAC symmetry breaking and reformation.

CDK/GSK-3 inhibitors as a new approach for the treatment of proliferative renal diseases.

Proliferation of specific renal cell types leads to the development of many types of kidney disease. Given the central role that both cyclin-dependent kinases (CDKs) and glycogen synthase kinase-3 (GSK-3) play in promoting aberrant proliferation within the kidney, these paralogous serine/threonine kinases are being explored as therapeutic molecular targets in proliferative renal diseases. CDK/GSK-3 inhibitors have now demonstrated efficacy in preclinical models of mesangial proliferative glomerulonephritis, crescentic glomerulonephritis, proliferative lupus nephritis and collapsing glomerulopathy. Moreover, they have recently entered human clinical trials in IgA nephropathy. Since the pathogenesis of most proliferative renal diseases is multifactorial, there is the belief that CDK/GSK-3 inhibitors, as inherently promiscuous drugs, may have several modes of action. This is supported by recent studies in systems research delineating the antiinflammatory profile of CDK/GSK-3 inhibitors compared with other immunomodulators. Thus, CDK/GSK-3 inhibitors may emerge as effective drugs for proliferative renal diseases due to their integrative properties across several aspects of disease pathogenesis. This brief mini-review will highlight these issues.

Collapsing glomerulopathy.

Collapsing glomerulopathy (CG) has become an important cause of ESRD. First delineated from other proteinuric glomerular lesions in the 1980s, CG is now recognized as a common, distinct pattern of proliferative parenchymal injury that portends a rapid loss of renal function and poor responses to empiric therapy. Notwithstanding, the rise in disorders that are associated with CG, the identification of the first susceptibility genes for CG, the remarkable increase in murine modeling of CG, and promising preclinical testing of new therapeutic strategies suggest that the outlook for CG as a poorly understood and therapeutically resistant renal disease is set to change in the future. This focused review highlights recent advances in research into the pathogenesis and treatment of CG.

PKC-theta knockout mice are protected from fat-induced insulin resistance.

Insulin resistance plays a primary role in the development of type 2 diabetes and may be related to alterations in fat metabolism. Recent studies have suggested that local accumulation of fat metabolites inside skeletal muscle may activate a serine kinase cascade involving protein kinase C-theta (PKC-theta), leading to defects in insulin signaling and glucose transport in skeletal muscle. To test this hypothesis, we examined whether mice with inactivation of PKC-theta are protected from fat-induced insulin resistance in skeletal muscle. Skeletal muscle and hepatic insulin action as assessed during hyperinsulinemic-euglycemic clamps did not differ between WT and PKC-theta KO mice following saline infusion. A 5-hour lipid infusion decreased insulin-stimulated skeletal muscle glucose uptake in the WT mice that was associated with 40-50% decreases in insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) and IRS-1-associated PI3K activity. In contrast, PKC-theta inactivation prevented fat-induced defects in insulin signaling and glucose transport in skeletal muscle. In conclusion, our findings demonstrate that PKC-theta is a crucial component mediating fat-induced insulin resistance in skeletal muscle and suggest that PKC-theta is a potential therapeutic target for the treatment of type 2 diabetes.

Protein kinase C Theta inhibits insulin signaling by phosphorylating IRS1 at Ser(1101).

Obesity and stress inhibit insulin action by activating protein kinases that enhance serine phosphorylation of IRS1 and have been thus associated to insulin resistance and the development of type II diabetes. The protein kinase C (PKC) is activated by free-fatty acids, and its activity is higher in muscle from obese diabetic patients. However, a molecular link between PKC and insulin resistance has not been defined yet. Here we show that PKC phosphorylates IRS1 at serine 1101 blocking IRS1 tyrosine phosphorylation and downstream activation of the Akt pathway. Mutation of Ser(1101) to alanine makes IRS1 insensitive to the effect of PKC and restores insulin signaling in culture cells. These results provide a novel mechanism linking the activation of PKC to the inhibition of insulin signaling.

Protein kinase C theta is critical for the development of in vivo T helper (Th)2 cell but not Th1 cell responses.

The serine/threonine-specific protein kinase C (PKC)-theta is predominantly expressed in T cells and localizes to the center of the immunological synapse upon T cell receptor (TCR) and CD28 signaling. T cells deficient in PKC-theta exhibit reduced interleukin (IL)-2 production and proliferative responses in vitro, however, its significance in vivo remains unclear. We found that pkc-theta(-/-) mice were protected from pulmonary allergic hypersensitivity responses such as airway hyperresponsiveness, eosinophilia, and immunoglobulin E production to inhaled allergen. Furthermore, T helper (Th)2 cell immune responses against Nippostrongylus brasiliensis were severely impaired in pkc-theta(-/-) mice. In striking contrast, pkc-theta(-/-) mice on both the C57BL/6 background and the normally susceptible BALB/c background mounted protective Th1 immune responses and were resistant against infection with Leishmania major. Using in vitro TCR transgenic T cell-dendritic cell coculture systems and antigen concentration-dependent Th polarization, PKC-theta-deficient T cells were found to differentiate into Th1 cells after activation with high concentrations of specific peptide, but to have compromised Th2 development at low antigen concentration. The addition of IL-2 partially reconstituted Th2 development in pkc-theta(-/-) T cells, consistent with an important role for this cytokine in Th2 polarization. Taken together, our results reveal a central role for PKC-theta signaling during Th2 responses.

Protein kinase C-theta;: signaling from the center of the T-cell synapse.

The hypothesis that protein kinase C (PKC)-theta; plays an important role in T-lymphocyte activation, as indicated by numerous studies in cell lines, was recently confirmed in mice deficient in the expression of this enzyme. In response to TCR stimulation, peripheral T cells lacking PKC-theta; failed to activate NF-kappaB and AP-1, and to express IL-2. This revealed a critical function for this PKC family member in linking membrane-proximal activation cascades to transcriptional responses governing T-cell activation. Although the molecular interactions in which PKC-theta; engages have not been fully delineated, insights from a variety of recent studies have permitted new models to be formulated regarding the mechanisms through which it achieves its unique effector functions.