Activation of the JAK–STAT pathway by type I interferons (IFNs) requires clathrin-dependent endocytosis of the IFN-α and -β receptor (IFNAR), indicating a role for endosomal sorting in this process. The molecular machinery that brings the selective activation of IFN-α/β-induced JAK–STAT signalling on endosomes remains unknown. Here we show that the constitutive association of STAM with IFNAR1 and TYK2 kinase at the plasma membrane prevents TYK2 activation by type I IFNs. IFN-α-stimulated IFNAR endocytosis delivers the STAM–IFNAR complex to early endosomes where it interacts with Hrs, thereby relieving TYK2 inhibition by STAM and triggering signalling of IFNAR at the endosome. In contrast, when stimulated by IFN-β, IFNAR signalling occurs independently of Hrs as IFNAR is sorted to a distinct endosomal subdomain. Our results identify the molecular machinery that controls the spatiotemporal activation of IFNAR by IFN-α and establish the central role of endosomal sorting in the differential regulation of JAK–STAT signalling by IFN-α and IFN-β.

I 型干扰素 (IFN) 激活 JAK–STAT 通路需要 IFN-α 和 -β 受体 (IFNAR) 的网格蛋白依赖性内吞作用，表明内体分选在此过程中的作用。在内体上选择性激活 IFN-α/β 诱导的 JAK-STAT 信号传导的分子机制仍然未知。在这里，我们表明 STAM 与质膜上的 IFNAR1 和 TYK2 激酶的组成型关联可防止 I 型干扰素激活 TYK2。IFN-α 刺激的 IFNAR 内吞作用将 STAM-IFNAR 复合物递送至早期内体，在那里它与 Hrs 相互作用，从而减轻 STAM 对 TYK2 的抑制并触发内体的 IFNAR 信号传导。相反，当受到 IFN-β 刺激时，IFNAR 信号传导独立于 Hrs 发生，因为 IFNAR 被分类到不同的内体亚域。