Poster Presentation Lorne Infection and Immunity 2022

Role of PHIST protein in knob formation (#208)

Mohini A Shibu 1 , Gerry J Shami 1 , Leann M Tilley 1 , Matthew W.A. Dixon 1
  1. The University of Melbourne, Parkville, VICTORIA, Australia

A key pathophysiology of malaria is the ability of infected erythrocytes to adhere to the venous endothelium of the host. An erythrocyte infected by Plasmodium falciparum develops visible protrusions on the erythrocyte membrane as the parasite develops; these structures are called “knobs”. The knob structure consists of a spiral protein scaffold of unknown composition that is closely associated with the RBC membrane skeleton. The spiral structure is supported by the knob-associated histidine-rich protein (KAHRP) which forms a ring around the base of the structure. Despite the importance of this structure to the presentation of the major virulence antigen, PfEMP1 and severe disease state, little is known about its protein composition, or the proteins required for its assembly. To investigate the composition of the knobs we performed immunoprecipitation experiments, using a cell line expressing GFP tagged KAHRP. These experiments identified several candidate genes from the PHISTb family of exported proteins including the previously uncharacterised protein PF3D7_0532300. In our work, we show that PF3D7_0532300 localises to the RBC membrane skeleton. Gene knockout experiments show that deletion of this protein leads to large extended, lobed structures and smaller vesicle structures at the RBC membrane. Examination of these abnormal structures using super-resolution microscopy show a reorganisation of RBC membrane skeleton components suggesting a possible role for PF3D7_0532300 in facilitating and organising the knob structure and its formation.