Extracellular double-stranded RNA (dsRNA) is an important modulator in innate immunity in both vertebrates and invertebrates. In shrimp, extracellular dsRNA can trigger RNAi pathway and serves as antiviral defense mechanism. However, the mechanism of dsRNA internalization into the cells has not yet known in shrimp cells. This study identified candidate cell surface proteins from shrimp hepatopancreatic cells that could interact with dsRNA by a ligand blot assay. Among the candidate proteins, a cell-surface beta subunit of ATP synthase was shown to be capable of internalizing dsRNA into shrimp hepatopancreatic cells that could rapidly occur in just 1 min upon dsRNA challenge. Colocalization between dsRNA and ATP synthase beta subunit implied correlation between dsRNA and ATP synthase beta subunit during dsRNA internalization. Furthermore, dsRNA showed colocalization with Ras-related endocytic proteins, Rab5 and Rab7 indicating that dsRNA was internalized via the receptor-mediated endocytosis. For the above evidences as well as the reduction of dsRNA internalization by angiostatin and antibodies against ATP synthase beta subunit, we propose that dsRNA interacts with ATP synthase via a nucleotide binding site in the beta subunit prior to internalize dsRNA into cells.

细胞外双链RNA（dsRNA）是脊椎动物和无脊椎动物先天免疫的重要调节剂。在虾中，细胞外dsRNA可以触发RNAi途径并充当抗病毒防御机制。然而，在虾细胞中尚不知道dsRNA内化进入细胞的机制。这项研究从虾肝胰腺细胞中鉴定了候选细胞表面蛋白，这些蛋白可以通过配体印迹法与dsRNA相互作用。在候选蛋白质中，ATP合酶的细胞表面β亚单位显示出能够将dsRNA内在化成虾肝胰腺细胞的能力，而dsRNA攻击仅需1分钟即可迅速发生。dsRNA和ATP合酶β亚基之间的共定位意味着在dsRNA内化过程中dsRNA和ATP合酶β亚基之间的相关性。此外，dsRNA与Ras相关的内吞蛋白Rab5和Rab7共定位，表明dsRNA通过受体介导的内吞作用而被内在化。对于上述证据以及血管抑素和针对ATP合酶β亚基的抗体对dsRNA内在化的减少，我们提出，在将dsRNA内化到细胞中之前，dsRNA通过β亚基中的核苷酸结合位点与ATP合酶相互作用。