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Cytoplasmic Actin Is an Extracellular Insect Immune Factor which Is Secreted upon Immune Challenge and Mediates Phagocytosis and Direct Killing of Bacteria, and Is a Plasmodium Antagonist

Fig 3

Actin binds to the surface of different bacteria and is externalized into the mosquito hemolymph upon immune challenge.

Analysis of actin content in the (A) 0.3 M NaCl-eluted fraction of Gram-negative (E. coli, E.c; Esp_Z, E.z.) and Gram-positive (S. aureus, S. a.; B. pumilus B. p.) bacterial species after incubation with immune-challenged cell line supernatants, or (B) 0.3–0.5 M NaCl (E3–E5)-eluted fractions and pellets (P) of Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria incubated with recombinant actin alone (Ac), or together with AgMDL1 (Ac+MDL1). (C) Mosquito hemolymph probed for actin (Ac) and AgMDL1 (MDL1) after challenge with PBS, E. coli (E.c. OD 2.8) or LPS-Pa (100 ng) for 4 hr. (D) Actin content in Moss55 cell supernatant after incubation with E. coli (E.c. MOI 1000) for 30 min, 1 hr, or 2 hr or untreated (UT).

Fig 3