Spatial and temporal organization of Interleukin-1 receptor and Toll-like receptor signalling

通过白介素1受体(IL-1RI)和Toll样受体(TLRs)传递的信号对于先天免疫系统的病原体检测是至关重要的。IL-1RI/TLR信号受白细胞介素1受体相关激酶(IRAK)家族蛋白激酶的调节。我们最近证实了IRAK1的修饰带有一条不寻常的多泛素链，该链通过泛素的赖氨酸63(K63)连接，这是依赖IL-1激活转录因子核因子κB(NFκB)的关键。此外，我们还证实了IL-1刺激IRAK1降解的机制未知。最近令人惊讶的发现表明，IRAK1降解具有新的调节作用。IL-1RI/TLR介导的信号转导可分为早期IRAK1依赖阶段(1h)和晚期IRAK2依赖阶段(4~16h)。我们推测，IRAK1的降解是从早期向晚期过渡的关键调控机制。为了验证这一假设，我们将确定并抑制IRAK1的降解机制。IRAK2依赖的信号转导的分子机制完全不清楚。我们将确定IRAK2的相互作用伙伴和潜在的激酶底物。由于IL-1RI和TLR4都是在配体结合时内化的，我们假设IRAK1依赖的早期信号发生在质膜上，而IRAK2依赖的信号事件在晚期从细胞内室启动。为了验证这一假设，我们将分析IRAK1和IRAK2在细胞内的定位和运输。

Signalling through Interleukin 1 receptor (IL-1RI) and Toll-like receptors (TLRs) is pivotal for pathogen detection by the innate immune system. IL-1RI/TLR signalling is regulated by protein kinases of the Interleukin-1 receptor associated kinase (IRAK) family. We recently demonstrated the modification of IRAK1 with an unusual polyubiquitin chain that is linked via Lysine 63 (K63) of ubiquitin, which is key for the IL-1-dependent activation of the transcription factor nuclear factor κB (NFκB). Furthermore, we demonstrated the IL-1-stimulated degradation of IRAK1 by an unknown mechanism. Surprising recent discoveries suggest a novel regulatory role for IRAK1 degradation. IL-1RI/TLR-mediated signal transduction appears to be divided into an early IRAK1-dependent phase of (<1 h) and a late IRAK2-dependent phase (4-16 h). We postulate that the IRAK1 degradation is a key regulatory mechanism for the transition from the early to the late phase. To test this hypothesis we will identify and inhibit the machinery for IRAK1 degradation. The molecular mechanisms of the IRAK2-dependent signal transduction are completely unknown. We will identify interaction partners and potential kinase substrates of IRAK2. Since both IL-1RI and TLR4 are internalized upon ligand binding, we hypothesize that the IRAK1-dependent early phase signalling takes place at the plasma membrane, whereas the IRAK2-dependent signalling events are initiated in the late phase from an intracellular compartment. To test this hypothesis, we will analyse the intracellular localization and trafficking of IRAK1 and IRAK2.