A Comprehensive Analysis of Plasmodium Circumsporozoite Protein Binding to Hepatocytes

PLoS One. 2016 Aug 25;11(8):e0161607. doi: 10.1371/journal.pone.0161607. eCollection 2016.

Abstract

Circumsporozoite protein (CSP) is the dominant protein on the surface of Plasmodium sporozoites and plays a critical role in the invasion by sporozoites of hepatocytes. Contacts between CSP and heparin sulfate proteoglycans (HSPGs) lead to the attachment of sporozoites to hepatocytes and trigger signaling events in the parasite that promote invasion of hepatocytes. The precise sequence elements in CSP that bind HSPGs have not been identified. We performed a systematic in vitro analysis to dissect the association between Plasmodium falciparum CSP (PfCSP) and hepatocytes. We demonstrate that interactions between PfCSP and heparin or a cultured hepatoma cell line, HepG2, are mediated primarily by a lysine-rich site in the amino terminus of PfCSP. Importantly, the carboxyl terminus of PfCSP facilitates heparin-binding by the amino-terminus but does not interact directly with heparin. These findings provide insights into how CSP recognizes hepatocytes and useful information for further functional studies of CSP.

MeSH terms

  • Animals
  • Escherichia coli
  • Green Fluorescent Proteins / metabolism
  • Hep G2 Cells
  • Heparin / chemistry
  • Hepatocytes / metabolism
  • Hepatocytes / parasitology*
  • Humans
  • Liver / metabolism
  • Lysine / chemistry
  • Pichia
  • Plasmodium falciparum / metabolism*
  • Protein Binding
  • Protozoan Proteins / metabolism*
  • Signal Transduction
  • Sporozoites / metabolism*

Substances

  • Protozoan Proteins
  • circumsporozoite protein, Protozoan
  • Green Fluorescent Proteins
  • Heparin
  • Lysine

Grant support

Q. Wang is supported by startup funds from Tianjin Medical University. J. Hu is supported by the National Natural Science Foundation of China (grant 31225006), and an International Early Career Scientist grant from Howard Hughes Medical Institute.