CEN2

CEN2 (PF3D7_1446600) is an EF-hand calcium-binding centrin that functions in Plasmodium cell division, associating with the centrosome and spindle-pole apparatus during schizogony (PMID:18693242). In P. falciparum, immunoelectron microscopy places centrin in close proximity to the nucleus of sporozoites and asexual schizonts in association with the parasite centrosome, and episomal expression of CEN2 partially rescues growth and the cytokinesis defect of a centrin-knockout Leishmania donovani line, giving functional support for a role in cell division (PMID:18693242). During cytokinesis, CEN2 partially localizes to the posterior cup subcompartment of the basal complex; conditional loss of function arrests parasite growth and replication and produces variable defects in basal complex contraction and synchrony, and free intracellular calcium is necessary but not sufficient for this contraction, implicating the EF-hand calcium-binding activity of CEN2 in the process (PMID:38829893). Beyond its centrosome/spindle-pole and basal-complex association and this contractile role, no further mechanistic detail—including direct binding partners or the calcium-transduction mechanism—has been characterized for CEN2 in the available corpus.

1. 2008 Medium

   Whether Plasmodium centrin proteins act in cell division was unresolved; localizing CEN2 to the centrosome and testing it in a functional complementation assay established a division-associated role.

   Evidence Immunoelectron microscopy and alpha-tubulin co-staining in P. falciparum sporozoites/schizonts plus growth and cytokinesis complementation in centrin-knockout Leishmania donovani

   PMID:18693242

   Open questions at the time

   • The complementation result was attributed to one of four PfCENs without specifying CEN2 as the rescuing member, limiting attribution precision
   • No direct calcium-binding or biochemical activity demonstrated for CEN2 itself
   • No binding partners at the centrosome identified
2. 2020 Low

   It was unclear where centrin-2 sits relative to the mitotic spindle during schizogony; co-localization with spindle-pole markers positioned it as a spindle-pole marker in blood-stage mitosis.

   Evidence Fixed-cell immunofluorescence co-localization with alpha-tubulin and kinesin-5-GFP during P. berghei blood-stage schizogony

   PMID:33154955

   Open questions at the time

   • Single co-localization experiment with centrin-2 used only as a reference marker, no functional manipulation of centrin-2
   • Shown in P. berghei, not P. falciparum
   • Does not establish whether spindle-pole localization is required for mitotic function
3. 2024 Medium

   Whether CEN2 contributes to cytokinesis at a specific structure was unknown; expansion microscopy and conditional knockdown placed it at the basal complex posterior cup and showed it is essential for contraction and replication.

   Evidence Ultrastructure expansion microscopy, live-cell imaging, and conditional loss-of-function with basal-complex contraction and growth phenotypes in P. falciparum

   PMID:38829893

   Open questions at the time

   • Loss-of-function produced variable rather than fully penetrant contraction defects, leaving the precise requirement unclear
   • How calcium binding by CEN2 is transduced into basal complex contraction is not defined
   • Direct molecular partners at the posterior cup remain unidentified

• The direct binding partners and the biochemical mechanism by which CEN2 calcium binding drives basal complex contraction and spindle-pole function remain unknown.
• No reconstitution or direct calcium-binding assay for CEN2 in the corpus
• No identified interaction partners at the centrosome or posterior cup
• Mechanism linking calcium flux to contraction not established