open access

https://hdl.handle.net/2115/47001

Adaptor protein is essential for insect cytokine signaling in hemocytes

英語

SH2/SH3 domain binding

2010-09-07

National Academy of Sciences

Proceedings of the National Academy of Sciences of the United States of America

107(36)

15862-15867

Growth-blocking peptide (GBP) is an insect cytokine that stimulates a class of immune cells called plasmatocytes to adhere to each other and foreign surfaces. Although structure-activity studies have been extensively performed on the GBP and its mutants in Lepidoptera Pseudaletia separata, the signaling pathway of GBP-dependent activation of plasmatocytes remains unknown. We identified a novel adaptor protein (P77) with a molecular mass of 77 kDa containing SH2/SH3 domain binding motifs and an immunoreceptor tyrosine-based activation motif (ITAM)-like domain in the cytoplasmic region of the C-terminus. Although P77 did not show the capacity for direct binding with GBP, its cytoplasmic tyrosine residues were specifically phosphorylated within seconds after addition of GBP to a plasmatocyte suspension. Tyrosine phosphorylation of P77 was also observed when hemocytes were incubated with Enterobactor cloacae or Micrococcus luteus, but this phosphorylation was found to be induced by GBP released from hemocytes stimulated by the pathogens. We further detected tyrosine phosphorylation of the integrin β subunit in plasmatocytes stimulated by GBP. Double-stranded RNAs targeting P77 not only decreased GBP-dependent tyrosine phosphorylation of the integrin β subunit, but also abolished GBP-induced spreading of plasmatocytes on foreign surfaces. P77 RNAi larvae also showed significantly higher mortality than control larvae following infection with Serratia marcescens, thus indicating that P77 is essential for GBP to mediate a normal innate cellular immunity in insects. These results demonstrated that GBP signaling in plasmatocytes requires the adaptor protein P77 and that active P77-assisted tyrosine phosphorylation of integrins is critical for the activation of plasmatocytes.

学術雑誌論文

Accepted Manuscript

0027-8424

1091-6490