title: Plasmodium vivax inhibits erythroid cell growth through altered phosphorylation of the cytoskeletal protein ezrin.
abstract: BACKGROUND
  The underlying causes of severe malarial anaemia are multifactorial. In previously reports, Plasmodium vivax was found to be able to directly inhibited erythroid cell proliferation and differentiation. The molecular mechanisms underlying the suppression of erythropoiesis by P. vivax are remarkably complex and remain unclear. In this study, a phosphoproteomic approach was performed to dissect the molecular mechanism of phosphoprotein regulation, which is involved in the inhibitory effect of parasites on erythroid cell development.
  
  
  METHODS
  This study describes the first comparative phosphoproteome analysis of growing erythroid cells (gECs), derived from human haematopoietic stem cells, exposed to lysates of infected erythrocytes (IE)/uninfected erythrocytes (UE) for 24, 48 and 72 h. This study utilized IMAC phosphoprotein isolation directly coupled with LC MS/MS analysis.
  
  
  RESULTS
  Lysed IE significantly inhibited gEC growth at 48 and 72 h and cell division resulting in the accumulation of cells in G0 phase. The relative levels of forty four phosphoproteins were determined from gECs exposed to IE/UE for 24-72 h and compared with the media control using the label-free quantitation technique. Interestingly, the levels of three phosphoproteins: ezrin, alpha actinin-1, and Rho kinase were significantly (p < 0.05) altered. These proteins display interactions and are involved in the regulation of the cellular cytoskeleton. Particularly affected was ezrin (phosphorylated at Thr567), which is normally localized to gEC cell extension peripheral processes. Following exposure to IE, for 48-72 h, the ezrin signal intensity was weak or absent. This result suggests that phospho-ezrin is important for actin cytoskeleton regulation during erythroid cell growth and division.
  
  
  CONCLUSIONS
  These findings suggest that parasite proteins are able to inhibit erythroid cell growth by down-regulation of ezrin phosphorylation, leading to ineffective erythropoiesis ultimately resulting in severe malarial anaemia. A better understanding of the mechanisms of ineffective erythropoiesis may be beneficial in the development of therapeutic strategies to prevent severe malarial anaemia.
authors.affiliation: Faculty of Science and Technology, Suan Dusit Rajabhat University, 204/3 Sirindhorn Rd. Bangplat, 10700, Bangkok, Thailand. tasanee_p@yahoo.com.
authors.forename: Tasanee
authors.initials: T
authors.lastname: Panichakul
authors.affiliation: Chulabhorn International College of Medicine, Thammasat University, 2nd Floor, Piyachart Building, Thammasat University, Rungsit campus, 12120, Patumthani, Thailand. saranyoo@tu.ac.th.
authors.forename: Saranyoo
authors.initials: S
authors.lastname: Ponnikorn
authors.affiliation: Proteomics Research Laboratory, National Center for Genetic and Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park, Phahonyothin Rd., Klong1, 12120, Klong Luang, Pathumthani, Thailand. sittiruk@biotec.or.th.
authors.forename: Sittiruk
authors.initials: S
authors.lastname: Roytrakul
authors.affiliation: Proteomics Research Laboratory, National Center for Genetic and Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park, Phahonyothin Rd., Klong1, 12120, Klong Luang, Pathumthani, Thailand. atchara@biotec.or.th.
authors.forename: Atchara
authors.initials: A
authors.lastname: Paemanee
authors.affiliation: Proteomics Research Laboratory, National Center for Genetic and Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park, Phahonyothin Rd., Klong1, 12120, Klong Luang, Pathumthani, Thailand. suthathip@biotec.or.th.
authors.forename: Suthathip
authors.initials: S
authors.lastname: Kittisenachai
authors.affiliation: Department of Pediatrics, Faculty of Medicine Ramathibodi Hospital, Mahidol University, 272 Rama VI Rd., Ratchathewi District, 10400, Bangkok, Thailand. suradej.hon@mahidol.ac.th.
authors.forename: Suradej
authors.initials: S
authors.lastname: Hongeng
authors.affiliation: Department of Pathobiology, Faculty of Science, Mahidol University, 272 Rama VI Rd., Ratchathewi District, 10400, Bangkok, Thailand. rachanee.udo@mahidol.ac.th.
authors.forename: Rachanee
authors.initials: R
authors.lastname: Udomsangpetch
mesh_terms: D049109:Cell Proliferation; D002853:Chromatography, Liquid; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D041905:Erythroid Cells / Q000737:chemistry / Q000469:parasitology*; D054884:Host-Pathogen Interactions; D006801:Humans; D010766:Phosphorylation; D010966:Plasmodium vivax / Q000502:physiology*; D011499:Protein Processing, Post-Translational; D020543:Proteome / Q000032:analysis; D053719:Tandem Mass Spectrometry; D013997:Time Factors; D000099149:Ezrin
chemical_list: D003598:Cytoskeletal Proteins; D020543:Proteome; D000099149:Ezrin