DRPC

TgDrpC is an Apicomplexa-specific dynamin-related protein essential for mitochondrial fission, organelle biogenesis, and parasite division in Toxoplasma gondii (PMID:30947298, PMID:30362624). It localizes adjacent to the single mitochondrion, both at its periphery and at the basal region where fission occurs, and depletion or dominant-negative expression yields interconnected mitochondria, drastic morphological defects, and parasite death (PMID:30947298). During parasite division TgDrpC redistributes from cytoplasmic puncta to the growing edge of daughter cells in a post-Golgi trafficking-dependent manner, and its conditional knockdown stalls division while causing deterioration of multiple organelles and the inner membrane complex (PMID:30362624). TgDrpC physically interacts with vesicle transport factors, including a homolog of the AP-2 complex alpha-1 subunit and an ERM-family homolog that co-localize to puncta and daughter cells (PMID:30362624). It operates through a non-canonical fission mechanism, as the conventional adaptor TgFis1 is dispensable for mitochondrial fission (PMID:30947298). Beyond these findings, the biochemical basis of its activity has not been characterized in the available corpus.

1. 2015 Low

   Establishing that drpC is an endogenous, silenceable gene provided the genetic entry point for interrogating its function.

   Evidence DiCre-mediated U1 snRNP-based conditional knockdown with rapamycin induction in T. gondii, used as proof-of-concept

   PMID:26090798

   Open questions at the time

   • No mechanistic characterization of TgDrpC function in this study
   • Used only as a technical demonstration of the silencing platform
2. 2018 Medium

   Whether TgDrpC has a division-stage role was answered by showing its dynamic redistribution to daughter cell growing edges and its essentiality for division and organelle integrity.

   Evidence Conditional knockdown, live imaging, and pharmacological inhibition of post-Golgi trafficking in T. gondii

   PMID:30362624

   Open questions at the time

   • The molecular cargo/function of TgDrpC at the daughter cell edge is undefined
   • Whether organelle deterioration is a direct or downstream consequence of division arrest is unresolved
3. 2018 Medium

   The trafficking context of TgDrpC was addressed by identifying interactions with AP-2 and ERM-family vesicle transport homologs, linking it to a membrane-trafficking machinery.

   Evidence Co-immunoprecipitation/interaction proteomics with co-localization in T. gondii

   PMID:30362624

   Open questions at the time

   • Interactions not validated reciprocally
   • Functional consequence of the AP-2 and ERM associations for fission or division not tested
4. 2019 High

   The primary organellar target of TgDrpC was defined as the mitochondrion, establishing it as essential for mitochondrial fission and biogenesis.

   Evidence Conditional knockdown, dominant-negative expression, mitochondrial morphology imaging, and viability assays in T. gondii

   PMID:30947298

   Open questions at the time

   • Direct demonstration of GTP-dependent membrane scission activity is absent
   • The mechanism recruiting TgDrpC to the fission site is unknown
5. 2019 Medium

   Whether TgDrpC uses the canonical fission adaptor was answered by showing TgFis1 is dispensable, revealing a non-canonical fission mechanism.

   Evidence Genetic loss-of-function of TgFis1 with mitochondrial morphology readout in T. gondii

   PMID:30947298

   Open questions at the time

   • The actual adaptor recruiting TgDrpC to the mitochondrion is unidentified
   • Negative result from a single lab

• The biochemical basis of TgDrpC action, including whether its atypical domain architecture supports GTPase-driven membrane scission and how it is recruited absent Fis1, remains unresolved.
• No direct biochemical validation of the functional consequence of the missing GTPase Effector Domain
• No identified mitochondrial recruitment adaptor
• No reconstitution of fission activity in vitro