Search

The dysregulation of receptor tyrosine kinases (RTKs) in multiple cell types during chronic inflammation is indicative of their pathogenic role in autoimmune diseases. Among the many RTKs, vascular endothelial growth factor receptor (VEGFR) stands out for its multiple effects on immunity, vascularization, and cell migration. Herein, we examined whether VEGFR participated in the pathogenesis of type 1 diabetes (T1D) in nonobese diabetic (NOD) mice. We found that RTK inhibitors (RTKIs) and VEGF or VEGFR-2 antibodies reversed diabetes when administered at the onset of hyperglycemia. Increased VEGF expression promoted islet vascular remodeling in NOD mice, and inhibition of VEGFR activity with RTKIs abrogated the increase in islet vascularity, impairing T-cell migration into the islet and improving glucose control. Metabolic studies confirmed that RTKIs worked by preserving islet function, as treated mice had improved glucose tolerance without affecting insulin sensitivity. Finally, examination of human pancreata from patients with T1D revealed that VEGFR-2 was confined to the islet vascularity, which was increased in inflamed islets. Collectively, this work reveals a previously unappreciated role for VEGFR-2 signaling in the pathogenesis of T1D by controlling T-cell accessibility to the pancreatic islets and highlights a novel application of VEGFR-2 antagonists for the therapeutic treatment of T1D., In type 1 diabetes (T1D), genetic and environmental risk factors lead to immune dysregulation, provoking an autoimmune response directed toward insulin-producing β-cells of the islets of Langerhans. Previous investigations have [...]

Members of the TNF receptor (TNFR) superfamily are cell‐surface proteins that can be found on most cell types including lymphocytes. Although some TNFR‐related molecules are constitutively expressed, others, such as CD30 and Ox40, are induced upon activation of lymphocytes. CD30 and Ox40 are predominantly expressed on activated T helper (Th)2 cells. Both receptors can activate c‐Jun N‐terminal kinase (JNK) and nuclear factor‐κB (NF‐κB) and have been suggested to play costimulatory roles in lymphocyte activation. To gain further insight into events triggered by both TNFR‐related molecules, a detailed analysis of their expression patterns has been prformed. We found that CD30 and Ox40 were coexpressed on Th2 cells. However, in contrast to CD30, Ox40 was also expressed on Th1 cells. Although expression of both receptors is augmented by interleukin‐4, only CD30 expression is dependent on signal transducer and activator of transcription (STAT)‐6‐mediated signaling. Differences in the regulatory pathways controlling expression of CD30 and Ox40 suggest distinct, functional effects triggered by the two TNFR‐related molecules during lymphocyte activation.

Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) are involved in signaling pathways triggered by members of the TNF receptor (TNFR) family and other cell surface proteins. After recruitment to a receptor, TRAFs initiate formation of multiprotein complexes that induce downstream events, such as translocation of transcription factor nuclear factor κB (NF-κB) and activation of c-Jun N-terminal kinase (JNK). Several proteins in these complexes play important roles in regulation of apoptosis. However, the fate of TRAF-containing complexes once assembled in response to receptor multimerization is not understood. In this report, we demonstrate that crosslinking of TNFR family members or interaction of TRAF2 with the cytoplasmic protein A20 leads to intracellular translocation of TRAF2. This redistribution leads to depletion of the cytoplasmic pool of TRAF2. The ratio between soluble and insoluble TRAF2 determines the sensitivity of cells to TNF-α-induced apoptosis and may play an important role in limiting further TRAF-dependent signal transduction.

ABSTRACTMembers of the tumor necrosis factor (TNF)-nerve growth factor (NGF) receptor family have been shown to be important costimulatory molecules for cellular activation. 4-1BB and Ox40 are two recently described members of this protein family which are expressed primarily on activated T cells. To gain insight into the signaling pathways employed by these factors, yeast two-hybrid library screens were performed with the cytoplasmic domains of 4-1BB and Ox40 as baits. TNF receptor-associated factor 2 (TRAF2) was identified as an interacting protein in both screens. The ability of both 4-1BB and Ox40 to interact with TRAF2 was confirmed in mammalian cells by coimmunoprecipitation studies. When the binding of the receptors to other TRAF proteins was investigated, 4-1BB and Ox40 displayed distinct binding patterns. While 4-1BB bound TRAF2 and TRAF1, Ox40 interacted with TRAF3 and TRAF2. Using deletion and alanine scanning analysis, we defined the elements in the cytoplasmic domains of both receptors that mediate these interactions. The 4-1BB receptor was found to have two independent stretches of acidic residues that can mediate association of the TRAF molecules. In contrast, a single TRAF binding domain was identified in the cytoplasmic tail of Ox40. The cytoplasmic domains of both receptors were shown to activate nuclear factor κB in a TRAF-dependent manner. Taken together, our results indicate that 4-1BB and Ox40 bind TRAF proteins to initiate a signaling cascade leading to activation of nuclear factor κB.

ABSTRACTMembers of the tumor necrosis factor (TNF)-nerve growth factor (NGF) receptor family have been shown to be important costimulatory molecules for cellular activation. 4-1BB and Ox40 are two recently described members of this protein family which are expressed primarily on activated T cells. To gain insight into the signaling pathways employed by these factors, yeast two-hybrid library screens were performed with the cytoplasmic domains of 4-1BB and Ox40 as baits. TNF receptor-associated factor 2 (TRAF2) was identified as an interacting protein in both screens. The ability of both 4-1BB and Ox40 to interact with TRAF2 was confirmed in mammalian cells by coimmunoprecipitation studies. When the binding of the receptors to other TRAF proteins was investigated, 4-1BB and Ox40 displayed distinct binding patterns. While 4-1BB bound TRAF2 and TRAF1, Ox40 interacted with TRAF3 and TRAF2. Using deletion and alanine scanning analysis, we defined the elements in the cytoplasmic domains of both receptors that mediate these interactions. The 4-1BB receptor was found to have two independent stretches of acidic residues that can mediate association of the TRAF molecules. In contrast, a single TRAF binding domain was identified in the cytoplasmic tail of Ox40. The cytoplasmic domains of both receptors were shown to activate nuclear factor ?B in a TRAF-dependent manner. Taken together, our results indicate that 4-1BB and Ox40 bind TRAF proteins to initiate a signaling cascade leading to activation of nuclear factor ?B.