AKIT1

AKIT1 (PF3D7_0723800) is a component of an inner kinetochore sub-complex (AKiT1-6) of apicomplexan parasites, positioned between the centromeric adaptor CENP-C and the outer kinetochore during parasite mitosis (PMID:36006241). In Toxoplasma gondii, its recruitment to kinetochores depends on CENP-C, while its depletion does not reduce levels of the outer-kinetochore marker Nuf2, indicating it is not required for outer kinetochore assembly (PMID:36006241). During male gametogenesis in Plasmodium yoelii, AKIT1 localizes laterally along spindle microtubules throughout endomitosis in an EB1-dependent manner, marking a lateral kinetochore-spindle attachment (PMID:37208365). In Plasmodium berghei, AKIT1 co-purifies with the Aurora-related kinase ARK1 in male gametocytes and schizonts, placing it within the ARK1-associated kinetochore interactome during mitosis (PMID:42323312, PMID:41748607). Beyond its membership in this inner kinetochore compartment and its physical association with CENP-C-dependent recruitment, EB1-dependent spindle localization, and ARK1, no further mechanistic detail on AKIT1 has been characterized in the available corpus.

1. 2022 Medium

   Establishing that apicomplexan kinetochores contain a previously unrecognized inner sub-complex answered where AKIT1 sits in the kinetochore architecture and how it is recruited.

   Evidence Cross-linked IP-MS interactomics plus genetic depletion with Nuf2 readout in Toxoplasma gondii and Plasmodium berghei

   PMID:36006241

   Open questions at the time

   • The molecular activity of AKIT1 within the AKiT1-6 complex is undefined
   • Direct binding interface between AKIT1 and CENP-C not resolved
   • Consequence of AKIT1 loss on chromosome segregation not measured
2. 2023 Medium

   Live/expansion imaging during male gametogenesis showed that AKIT1-marked kinetochores attach laterally to spindle microtubules, defining the mode of kinetochore-spindle coupling and its dependence on EB1.

   Evidence U-ExM and IFA with double-tagged (eb1::6HA; Akit1::4Myc) parasites and EB1 knockout in Plasmodium yoelii

   PMID:37208365

   Open questions at the time

   • Whether AKIT1 binds microtubules directly or via EB1 is not distinguished
   • Functional requirement of AKIT1 for lateral attachment not tested by AKIT1 depletion
   • Behavior in asexual (schizont) mitosis not addressed by this imaging
3. 2026 Medium

   Reciprocal tagged pulldowns placed AKIT1 within the ARK1 kinase interactome during male mitosis, linking the inner kinetochore sub-complex to Aurora-related kinase signaling.

   Evidence IP-MS of AKiT1-3xHA and ARK1-3xHA from male-only Plasmodium berghei gametocytes under native and low cross-linking conditions

   PMID:42323312

   Open questions at the time

   • Whether AKIT1 is a direct ARK1 substrate or a scaffold is unknown
   • Functional consequence of the AKIT1-ARK1 association not tested
   • Limited replicates noted for the pulldown
4. 2026 Low

   AKIT1 co-enrichment in ARK1-GFP pulldowns from both schizonts and male gametocytes extended the ARK1 association across two distinct mitotic stages.

   Evidence Anti-GFP co-IP/MS from ARK1-GFP Plasmodium berghei parasites with PCA of pulldown data

   PMID:41748607

   Open questions at the time

   • Single co-IP/MS with limited replicates (n=2) and no orthogonal validation of AKIT1 specifically
   • Direct versus indirect nature of the AKIT1-ARK1 association unresolved
   • Stage-specific functional roles of AKIT1 not distinguished

• The molecular function of AKIT1 itself — its intrinsic activity, its direct binding partners within AKiT1-6, and whether it is required for chromosome segregation — remains unresolved beyond complex membership and physical associations.
• No biochemical activity assigned to AKIT1
• No structure or defined interaction interface for AKIT1
• No AKIT1-specific loss-of-function phenotype for chromosome segregation reported