CERLI1

CERLI1 (PF3D7_0210600) is a conserved protein required for erythrocyte invasion by Plasmodium falciparum merozoites, where it acts at the rhoptry to enable secretion of invasion effectors (PMID:32179747). It localizes to the cytosolic face of the rhoptry bulb membrane (PMID:32179747), and conditional knockdown blocks merozoite invasion while leaving schizogony and merozoite organelle biogenesis intact, defining a role in rhoptry function rather than organelle formation (PMID:32179747). Mechanistically, loss of CERLI1 prevents secretion of key rhoptry antigens that coordinate invasion, establishing it as a factor essential for rhoptry exocytosis (PMID:32179747). In P. berghei, transcription of the cerli1 locus is directly targeted by the SIP2 AP2 transcription factor, placing CERLI1 expression under a master regulator of merozoite formation (PMID:40117352). Beyond its rhoptry localization, invasion/secretion requirement, and transcriptional regulation, no direct molecular partners, biochemical activity, or structural detail for CERLI1 have been characterized in the available corpus.

1. 2020 High

   To place CERLI1 in the invasion machinery, its subcellular position had to be defined; localization to the cytosolic face of the rhoptry bulb membrane established it as a peripheral rhoptry-associated protein rather than a lumenal cargo.

   Evidence Biochemical fractionation and semi-quantitative super-resolution microscopy in P. falciparum merozoites

   PMID:32179747

   Open questions at the time

   • How CERLI1 is anchored or recruited to the rhoptry bulb membrane is not defined
   • No interacting membrane or complex partners identified
2. 2020 High

   Whether CERLI1 is needed for building rhoptries or for their function was unresolved; conditional knockdown blocked invasion without perturbing schizogony or organelle biogenesis, pinpointing a functional rather than biogenetic role.

   Evidence Conditional knockdown with invasion and schizogony phenotypic readouts in P. falciparum

   PMID:32179747

   Open questions at the time

   • The specific step of invasion arrested (attachment, tight junction, or entry) is not resolved
   • Single lab
3. 2020 High

   The mechanism behind the invasion block needed definition; knockdown was shown to prevent secretion of key rhoptry antigens, establishing CERLI1 as required for rhoptry exocytosis.

   Evidence Biochemical assays and semi-quantitative super-resolution microscopy following conditional knockdown in P. falciparum

   PMID:32179747

   Open questions at the time

   • The molecular step in exocytosis CERLI1 controls (docking, priming, fusion) is unknown
   • No demonstrated direct binding to secretory or fusion machinery
4. 2025 Medium

   How CERLI1 expression is timed to merozoite formation was unaddressed; ChIP-seq showed the SIP2 AP2 factor directly binds the cerli1 locus, linking its transcription to a master regulator of merozoite development.

   Evidence ChIP-seq of PbSIP2 binding sites genome-wide in P. berghei

   PMID:40117352

   Open questions at the time

   • Functional consequence of SIP2 binding on CERLI1 expression was not individually validated
   • Shown in P. berghei; not confirmed for the P. falciparum ortholog
   • Single lab, single method for this gene

• The direct molecular partners and biochemical activity by which CERLI1 promotes rhoptry secretion remain unknown.
• No interacting proteins or complex membership defined for CERLI1
• No enzymatic or biochemical activity characterized
• No structural model available