ApiLoc - A database of published protein sub-cellular localisation in Apicomplexa

version 3 (curated until May 28, 2011)

Apical organelle discharge by Cryptosporidium parvum is temperature, cytoskeleton, and intracellular calcium dependent and required for host cell invasion.

Chen, X. M., O'Hara, S. P., Huang, B. Q., Nelson, J. B., Lin, J. J., Zhu, G., Ward, H. D., LaRusso, N. F. (2004 Dec, Infect Immun)

The apical organelles in apicomplexan parasites are characteristic secretory vesicles containing complex mixtures of molecules. While apical organelle discharge has been demonstrated to be involved in the cellular invasion of some apicomplexan parasites, including Toxoplasma gondii and Plasmodium spp., the mechanisms of apical organelle discharge by Cryptosporidium parvum sporozoites and its role in host cell invasion are unclear. Here we show that the discharge of C. parvum apical organelles occurs in a temperature-dependent fashion. The inhibition of parasite actin and tubulin polymerization by cytochalasin D and colchicines, respectively, inhibited parasite apical organelle discharge. Chelation of the parasite's intracellular calcium also inhibited apical organelle discharge, and this process was partially reversed by raising the intracellular calcium concentration by use of the ionophore A23187. The inhibition of parasite cytoskeleton polymerization by cytochalasin D and colchicine and the depletion of intracellular calcium also decreased the gliding motility of C. parvum sporozoites. Importantly, the inhibition of apical organelle discharge by C. parvum sporozoites blocked parasite invasion of, but not attachment to, host cells (i.e., cultured human cholangiocytes). Moreover, the translocation of a parasite protein, CP2, to the host cell membrane at the region of the host cell-parasite interface was detected; an antibody to CP2 decreased the C. parvum invasion of cholangiocytes. These data demonstrate that the discharge of C. parvum sporozoite apical organelle contents occurs and that it is temperature, intracellular calcium, and cytoskeleton dependent and required for host cell invasion, confirming that apical organelles play a central role in C. parvum entry into host cells.

PubMed: 15557601, full text

Localisation information

cgd6_5410 (CP2) signal peptide plus thr stretch, charged repeats, likely mucin

Experimental localisation: apical during sporozoite, dense band during sporozoite invasion, anterior vacuole during sporozoite invasion
  • Species: Cryptosporidium parvum
  • Quote inferring localisation: "Both 4E9 (a monoclonal antibody which recognizes microneme-associated gp900 and gp40 proteins) and CP2 (an antibody against membranous structures) also showed strong staining in the apical region of control sporozoites (B1 and C1, arrowheads) or those that were maintained at 4°C for 2 h (B2 and C2, arrowheads), but not in sporozoites that were maintained at 37°C for 2 h (B3 and C3, arrows)."
  • Microscopy type: light, EM
  • Microscopy method: polyclonal antibody directly to protein
  • Strain: Iowa
  • Gene model mapping comments: inferred from another publication
  • Localisation record: apical during sporozoite, dense band and anterior vacuole during sporozoite internalization