Conserved role of a complement-like protein in phagocytosis revealed by dsRNA knockout in cultured cells of the mosquito, Anopheles gambiae

Cell. 2001 Mar 9;104(5):709-18. doi: 10.1016/s0092-8674(01)00267-7.


We characterize a novel hemocyte-specific acute phase glycoprotein from the malaria vector, Anopheles gambiae. It shows substantial structural and functional similarities, including the highly conserved thioester motif, to both a central component of mammalian complement system, factor C3, and to a pan-protease inhibitor, alpha2-macroglobulin. Most importantly, this protein serves as a complement-like opsonin and promotes phagocytosis of some Gram-negative bacteria in a mosquito hemocyte-like cell line. Chemical inactivation by methylamine and depletion by double-stranded RNA knockout demonstrate that this function is dependent on the internal thioester bond. This evidence of a complement-like function in a protostome animal adds substantially to the accumulating evidence of a common ancestry of immune defenses in insects and vertebrates.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Anopheles / immunology*
  • Cells, Cultured
  • Cloning, Molecular
  • Complement C3 / chemistry
  • Complement C3 / genetics*
  • Complement C3 / immunology*
  • DNA Fragmentation
  • Female
  • Gram-Negative Bacteria / immunology
  • Hemocytes / physiology
  • Insect Proteins / chemistry
  • Insect Proteins / genetics*
  • Insect Proteins / immunology*
  • Molecular Sequence Data
  • Nucleic Acid Denaturation
  • Phagocytosis / immunology*
  • Protein Structure, Tertiary
  • RNA, Double-Stranded
  • Transcription, Genetic / immunology
  • alpha-Macroglobulins / genetics
  • alpha-Macroglobulins / immunology


  • Complement C3
  • Insect Proteins
  • RNA, Double-Stranded
  • alpha-Macroglobulins

Associated data

  • GENBANK/AF291654