Regulated secretion of multi-lamellar vesicles leads to formation of a tubulovesicular network in host-cell vacuoles occupied by Toxoplasma gondii

L. D. Sibley, I. R. Niesman, S. F. Parmley, M. F. Cesbron-Delauw

Research output: Contribution to journalArticlepeer-review

168 Scopus citations

Abstract

Toxoplasma gondii is an obligate intracellular parasite that actively invades virtually all types of nucleated cells, surviving within a specialized vacuole called the parasitophorous vacuole. Shortly after invasion, the parasite modifies this vacuole by secreting a variety of proteins from electron-dense storage granules. Additionally, the parasite forms a network of membranous tubules within the lumen of the vacuole and connecting with the vacuolar membrane. We have used immunolabeling and cell fractionation to examine the secretion of two dense granule proteins, GRA1 and GRA2, which are involved in formation of the intravacuolar network. Following host-cell invasion, GRA1 was secreted into the lumen of the vacuole as a soluble protein that subsequently became peripherally associated with the network. In addition to being secreted as a soluble protein from dense granules, GRA2 was secreted within multi-lamellar vesicles released from a specialized posterior invagination of the parasite. The multi-lamellar vesicles assemble to form the intravacuolar network, which contains an integral membrane form of GRA2. These findings indicate that Toxoplasma has a highly developed regulated exocytosis pathway that modifies the parasitophorous vacuole by secretion of soluble proteins and by a novel process of membrane secretion.

Original languageEnglish
Pages (from-to)1669-1677
Number of pages9
JournalJournal of cell science
Volume108
Issue number4
StatePublished - 1995

Keywords

  • Exocytosis
  • Integral membrane protein
  • Intracellular parasite
  • Membrane
  • Protozoan
  • Secretion
  • Toxoplasma

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