14-3-3zeta Regulates Transmembrane Receptor Signaling by Binding TRAF Proteins

Abstract

Abstract Adaptor proteins are critical for signal transduction events involving cytokine signaling, host-response, and autoimmune diseases. Our laboratory is interested in understanding the immune regulatory role of 14-3-3zeta (z), an adaptor protein, in signal transductions and diseases. We examined the role of 14-3-3z in interleukin-17 (IL-17A) signaling and autoimmune inflammatory arthritis using genetically modified cells and rats. The IL-17A signal transduction requires IL-17 receptor cytoplasmic domain interactions with Act1 and several TRAF proteins. Our results show that 14-3-3z interacts with TRAF6, TRAF2, and TRAF5 upon IL-17A stimulation which has functional consequences. The interaction of 14-3-3z and TRAF protein was found to be specific, as mutation of the interacting residues resulted in the loss of binding with functional impacts. Further interaction studies show a higher affinity of 14-3-3z for TRAF6, which has two putative 14-3-3 binding sites. To examine the generality of 14-3-3z-TRAF interactions and their role in another transmembrane receptor signaling, we examined RANKL signal transduction. Similar to IL-17A, 14-3-3z-TRAF interaction was increased upon RANKL treatment and had functional consequences. While there are common domains and significant sequence conservation between the TRAF proteins, a specificity of interactions exists with 14-3-3z. Our results show that the 14-3-3z-TRAF axis is a novel regulatory mechanism underneath several transmembrane receptor-mediated signaling. Current studies target understanding the molecular basis of interactions between 14-3-3z and specific TRAF proteins.