Frontiers in Immunology (Apr 2019)

Distinct Functions of Bombyx mori Peptidoglycan Recognition Protein 2 in Immune Responses to Bacteria and Viruses

  • Liang Jiang,
  • Liang Jiang,
  • Weiqiang Liu,
  • Huizhen Guo,
  • Huizhen Guo,
  • Yinghui Dang,
  • Tingcai Cheng,
  • Tingcai Cheng,
  • Wanying Yang,
  • Qiang Sun,
  • Bingbing Wang,
  • Yumei Wang,
  • Enyu Xie,
  • Qingyou Xia,
  • Qingyou Xia

DOI
https://doi.org/10.3389/fimmu.2019.00776
Journal volume & issue
Vol. 10

Abstract

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Peptidoglycan recognition protein (PGRP) is an important pattern recognition receptor in innate immunity that is vital for bacterial recognition and defense in insects. Few studies report the role of PGRP in viral infection. Here we cloned two forms of PGRP from the model lepidopteran Bombyx mori: BmPGRP2-1 is a transmembrane protein, whereas BmPGRP2-2 is an intracellular protein. BmPGRP2-1 bound to diaminopimelic acid (DAP)-type peptidoglycan (PGN) to activate the canonical immune deficiency (Imd) pathway. BmPGRP2-2 knockdown reduced B. mori nucleopolyhedrovirus (BmNPV) multiplication and mortality in cell lines and in silkworm larvae, while its overexpression increased viral replication. Transcriptome and quantitative PCR (qPCR) results confirmed that BmPGRP2 negatively regulated phosphatase and tensin homolog (PTEN). BmPGRP2-2 expression was induced by BmNPV, and the protein suppressed PTEN-phosphoinositide 3-kinase (PI3K)/Akt signaling to inhibit cell apoptosis, suggesting that BmNPV modulates BmPGRP2-2-PTEN-PI3K/Akt signaling to evade host antiviral defense. These results demonstrate that the two forms of BmPGRP2 have different functions in host responses to bacteria and viruses.

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