Key Points
Protease ADAM10 cleaves the ectodomain of Dscam upon bacterial infection.
IPO5 binds and translocates Dscam intracellular domains from cytoplasm into nuclei.
Nuclear imported Dscam regulates hemocytes proliferation.
Abstract
Down syndrome cell adhesion molecule (Dscam) generates tens of thousands of isoforms by alternative splicing, thereby providing crucial functions during immune responses. In this study, a novel Dscam signaling pathway was investigated in crab, which remains poorly characterized in invertebrates. Bacterial infection induced the cytoplasmic cleavage of Dscam intracellular domains (ICDs) by γ-secretase, and then the released ICDs carrying specific alternatively spliced exons could directly interact with IPO5 to facilitate nuclear translocation. Nuclear imported ICDs thus promoted hemocyte proliferation and protect the host from bacterial infection. Protein-interaction studies revealed that the ectodomain of Dscam bound to a disintegrin and metalloprotease domain 10 (ADAM10) rather than ADAM17. Inhibition or overexpression of ADAM10 impaired or accelerated Dscam shedding activity post–bacterial stimulation, respectively. Moreover, the shedding signal then mediated Dscam with an intact cytoplasmic domain to promote the cleavage of ICDs by γ-secretase. Furthermore, the transcription of ADAM10 was regulated by Dscam-induced canonical signaling, but not nuclear imported ICDs, to serve as a feedback regulation between two different Dscam pathways. Thus, membrane-to-nuclear signaling of Dscam regulated hemocyte proliferation in response to bacterial infection.
Footnotes
This work was supported by the National Natural Science Foundation of China (31972820 to W.-W.L. and 31970490 to Q.W.), Shanghai Rising-Star Program (20QA1403000 to W.-W.L.), and Fundamental Research Funds for the Central Universities (B200202141 to X.-K.J.).
H.L., Q.W., and W.-W.L. designed research; H.L., K.-M.Z., and H.Z. performed research; X.-K.J. performed bioinformatic analyses; Y.-H.Z. contributed new reagent/analytic tools; H.L., X.-K.J., and W.-W.L. analyzed data; W.-W.L. wrote the paper; W.-W.L. supervised the study.
The RNA-sequencing data in this article have been submitted to the National Center for Biotechnology Information Sequence Read Archive (https://www.ncbi.nlm.nih.gov/bioproject/PRJNA649344) under BioProject accession code PRJNA649344.
The online version of this article contains supplemental material.
Abbreviations used in this article
- ADAM
- a disintegrin and metalloprotease domain
- Co-IP
- coimmunoprecipitation
- DEG
- differentially expressed gene
- Dscam
- Down syndrome cell adhesion molecule
- EdU
- 5-ethynyl-2′-deoxyuridine
- HA
- hemagglutinin
- HEK
- human embryonic kidney
- ICD
- intracellular domain
- IPTG
- isopropyl-β-d-thiogalactoside
- NLS
- nuclear localization signal
- PDGF
- platelet-derived growth factor
- qRT-PCR
- quantitative real-time PCR
- RNAi
- RNA interference
- RNA-seq
- RNA deep sequencing
- SH3
- Src homology 3
- siRNA
- small interfering RNA
- VEGF
- vascular endothelial growth factor
- Received June 15, 2021.
- Accepted August 27, 2021.
- Copyright © 2021 by The American Association of Immunologists, Inc.
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