DataSheet_1_Insulin-regulated aminopeptidase contributes to setting the intensity of FcR-mediated inflammation.docx

The function of intracellular trafficking in immune-complex triggered inflammation remains poorly understood. Here, we investigated the role of Insulin-Regulated Amino Peptidase (IRAP)-positive endosomal compartments in Fc receptor (FcR)-induced inflammation. Less severe FcγR-triggered arthritis, active systemic anaphylaxis and FcεRI-triggered passive systemic anaphylaxis were observed in IRAP-deficient versus wild-type mice. In mast cells FcεRI stimulation induced rapid plasma membrane recruitment of IRAP-positive endosomes. IRAP-deficient cells exhibited reduced secretory responses, calcium signaling and activating SykY519/520 phosphorylation albeit receptor tyrosine phosphorylation on β and γ subunits was not different. By contrast, in the absence of IRAP, SHP1-inactivating phosphorylation on Ser591 that controls Syk activity was decreased. Ex-vivo cell profiling after FcγR-triggered anaphylaxis confirmed decreased phosphorylation of both SykY519/520 and SHP-1S591 in IRAP-deficient neutrophils and monocytes. Thus, IRAP-positive endosomal compartments, in promoting inhibition of SHP-1 during FcR signaling, control the extent of phosphorylation events at the plasma membrane and contribute to setting the intensity of immune-complex triggered inflammatory diseases.

细胞内运输在免疫复合物介导的炎症中的作用尚不明确。本研究旨在探讨胰岛素调节的氨基酸肽酶（IRAP）阳性内体隔室在Fc受体（FcR）诱导的炎症中的作用。与野生型小鼠相比，在IRAP缺陷型小鼠中观察到较轻的FcγR触发性关节炎、活跃的全身性过敏性休克和FcεRI触发性被动全身性过敏性休克。在肥大细胞中，FcεRI刺激导致IRAP阳性内体迅速被招募至质膜。IRAP缺陷型细胞表现出分泌反应、钙信号和SykY519/520磷酸化激活的降低，尽管β和γ亚单位的受体酪氨酸磷酸化没有差异。相反，在IRAP缺失的情况下，控制Syk活性的Ser591位点上SHP1失活的磷酸化降低。FcγR触发过敏性休克后的体外细胞分析证实，在IRAP缺陷型中性粒细胞和单核细胞中，SykY519/520和SHP-1S591的磷酸化均降低。因此，IRAP阳性内体隔室在促进FcR信号过程中SHP-1抑制的同时，调控质膜上磷酸化事件的程度，并有助于设定免疫复合物触发炎症疾病的强度。