Molecular characterization of a thrombospondin-related anonymous protein homologue in Neospora caninum

Jennie L. Lovett, Daniel K. Howe, L. David Sibley

Research output: Contribution to journalArticlepeer-review

65 Scopus citations


Thrombospondin-related anonymous protein (TRAP) family members participate in attachment and invasion of host cells by apicomplexan parasites. A TRAP homologue in Neospora caninum strain Nc-1 (NcMIC2) was cloned, sequenced and found to be 61% identical (75% similar) at the amino acid level to Toxoplasma gondii MIC2 (TgMIC2). Similar to TgMIC2, the predicted amino acid sequence of NcMIC2 contains one integrin-like domain (I or A domain), five thrombospondin (TSP) repeats, a putative transmembrane spanning region and intracellular C-terminus, and was localized to micronemes by cryo-immunoelectron microscopy. The secretion of NcMIC2 was temperature dependent and was induced at or above 25°C. The secreted form of NcMIC2 released into the medium was found to be proteolytically processed such that it lacked the C-terminal domain. Secretion of NcMIC2 was regulated by calcium, since several agents which raise intracellular calcium levels were shown to promote NcMIC2 secretion and chelation of [Ca2+](i) abrogated release. As a member of the growing family of apicomplexan TRAP proteins, NcMIC2 may play an important role in attachment and invasion by N. caninum into host cells. (C) 2000 Elsevier Science B.V.

Original languageEnglish
Pages (from-to)33-43
Number of pages11
JournalMolecular and Biochemical Parasitology
Issue number1
StatePublished - Mar 15 2000

Bibliographical note

Funding Information:
We thank Dr Joshua Sanes for providing monoclonal antibody clone 40-1a to β-Gal, Olivia K. Giddings for cell culture assistance, and Marilyn Levy for expert electron microscopy. JLL is partially supported by NIH training grant AI07172-19 to Washington University School of Medicine, with additional support provided by USDA grant 97-35203-4770 (LDS).


  • Adhesion
  • Apicomplexa
  • I domain
  • Microneme
  • Secretion
  • Thrombospondin

ASJC Scopus subject areas

  • Parasitology
  • Molecular Biology


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