Actin remodeling is required for knob formation. Sheared membranes were prepared from CS2-infected RBCs treated with or without cytochalasin D (CytoD), from 16 h post-invasion. Parasite infected RBCs were harvested at 22 h post-invasion, or cytochalasin D was removed at 22 h and cells harvested 8 h after removal at 30 h post-invasion (CytoD 8 h recovery). dSTORM images showing KAHRP distribution. Scale bar: 500 nm. While control infected RBCs assemble 2.5 ± 0.3 ring structures per μm2 by 22 h post-invasion, cytochalasin D-treated infected RBCs exhibit only 0.7 ± 0.2 ring structures per μm2 (. Accordingly, the cytochalasin D-treated cells exhibit a higher density of small KAHRP puncta, showing that cytochalasin D treatment does not affect KAHRP delivery and binding to the RBC membrane.
Looker O, Blanch AJ, Liu B, Nunez-Iglesias J, McMillan PJ, Tilley L, Dixon MWA. The knob protein KAHRP assembles into a ring-shaped structure that underpins virulence complex assembly. PLoS Pathog. 2019 May 9;15(5):e1007761.