Affinage · Plasmodium

LRR5

PF3D7_1432400 · leucine-rich repeat protein

Annotated
2026-09-08
4 papers in source corpus 4 papers cited in narrative 5 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

LRR5 (PF3D7_1432400) is a Plasmodium falciparum leucine-rich repeat protein that couples protein phosphatase type 1 (PP1) regulation to developmental timing and host-cell remodeling during the intraerythrocytic cycle (PMID:16629662, PMID:42294623). It is the P. falciparum SDS22 orthologue and physically associates with PfPP1, inhibiting the phosphatase in vitro; in a heterologous Xenopus oocyte system it drives progression through the G2/M checkpoint and germinal vesicle breakdown in a manner mimicking PP1 inhibition, linking LRR5 to cell-cycle control (PMID:16629662). Loss-of-function analysis in P. falciparum shows that disruption of LRR5 downregulates protein folding, protein export, and host-cell remodeling machinery (Maurer's cleft components, the PTEX export apparatus, and HSP70-x) while upregulating cytoplasmic heat-shock and translation genes, and prematurely activates gametocyte-associated programs including elevated Pfs16, indicating LRR5 restrains developmental progression toward transmission (PMID:42294623). The P. berghei orthologue PbLRR1 similarly forms a stage-spanning complex with PbPP1 and controls the phosphorylation status of Inhibitor 3, and its depletion impairs oocyst development (PMID:35920043). Beyond the PP1 interaction and these transcriptional and cell-cycle phenotypes, no substrate specificity or structural mechanism for LRR5 itself has been characterized in the available corpus.

Mechanistic history

Synthesis pass · year-by-year structured walk · 5 steps
  1. 2006 Medium

    Establishing whether the P. falciparum SDS22-type LRR protein regulates a phosphatase answered how PP1 activity might be controlled in the parasite, and showed LRR5's orthologue is a direct PP1 inhibitor.

    Evidence GST pull-down, co-immunoprecipitation from parasite extracts, and in vitro phosphatase activity assay showing PfLRR1-PfPP1 binding and inhibition

    PMID:16629662

    Open questions at the time
    • Interaction and inhibition shown for the PfLRR1 orthologue, not resolved to the PF3D7_1432400 gene product specifically
    • No structural basis for PP1 binding or inhibition
    • Physiological substrates of the PP1-LRR complex not identified
  2. 2006 Medium

    A heterologous functional test addressed whether LRR-mediated PP1 inhibition has cell-cycle consequences, showing the orthologue promotes G2/M progression like PP1 inhibition.

    Evidence Xenopus oocyte assay with GVBD readout, benchmarked against okadaic acid and anti-PP1 antibody treatment

    PMID:16629662

    Open questions at the time
    • Effect demonstrated in a non-parasite heterologous system
    • Direct cell-cycle role in P. falciparum not tested here
    • Does not identify the downstream phospho-targets that drive checkpoint progression
  3. 2007 Low

    Family-level cataloguing placed PF3D7_1432400 among P. falciparum LRR genes and established that it is transcribed across the intraerythrocytic cycle, providing baseline expression context.

    Evidence Genome analysis, cDNA cloning, and real-time quantitative PCR across the intraerythrocytic lifecycle

    PMID:17689674

    Open questions at the time
    • Transcriptional survey only; no function assigned to PF3D7_1432400
    • Does not distinguish LRR5 from sibling LRR family members functionally
    • Protein-level expression and localization not addressed
  4. 2022 High

    A rigorous orthologue study in P. berghei answered what the PP1-LRR complex controls and whether it matters for transmission, identifying Inhibitor 3 as a phospho-target and showing a role in oocyst development.

    Evidence Co-IP, phosphatase activity assay, genetic depletion, MS interactome, and phospho-proteomics in P. berghei

    PMID:35920043

    Open questions at the time
    • Shown for the P. berghei orthologue PbLRR1, not for P. falciparum PF3D7_1432400 directly
    • Mechanistic link between I3 dephosphorylation and oocyst phenotype not resolved
    • Does not establish which interactome partners are functionally required
  5. 2026 Medium

    Loss-of-function analysis in P. falciparum answered what disrupting LRR5 does to parasite biology, revealing coordinate downregulation of proteostasis and host-cell remodeling pathways alongside premature commitment to gametocytogenesis.

    Evidence piggyBac mutant (LRR5pB) vs. NF54 profiled by single-cell RNA-seq with pseudotime analysis and Pfs16 protein confirmation

    PMID:42294623

    Open questions at the time
    • Transcriptional phenotype does not establish which effects are direct versus secondary
    • Whether the developmental phenotype depends on PP1 inhibition is not tested
    • piggyBac insertion effects on the gene product not molecularly resolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • How PP1 regulation by LRR5 mechanistically connects to the observed proteostasis, host-cell remodeling, and premature gametocyte-commitment phenotypes in P. falciparum remains unresolved.
  • No direct demonstration that PF3D7_1432400 binds or inhibits PfPP1 (shown only for the orthologue)
  • Substrates dephosphorylated under LRR5 control in P. falciparum not identified
  • No structural model or defined domain determinants for LRR5 function

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
INHIBITOR 3 (I3) — PHOSPHO-TARGET OF THE PBLRR1/PBPP1 COMPLEX IN P. BERGHEIPFPP1 / PP1 (PROTEIN PHOSPHATASE TYPE 1)
Complex memberships
PP1-LRR (SDS22-type) complex with PfPP1 (P. falciparum orthologue) / PbPP1 (P. berghei orthologue)

Evidence

Reading pass · 5 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2006 PfLRR1 (the P. falciparum SDS22 orthologue, a leucine-rich repeat protein) physically interacts with PfPP1 (protein phosphatase type 1) as shown by GST pull-down assay, and this complex is present in parasite extracts. PfLRR1 inhibits PfPP1 phosphatase activity in vitro. GST pull-down assay, co-immunoprecipitation from parasite extracts, enzymatic phosphatase activity assay Molecular microbiology Medium 16629662
2006 When expressed in Xenopus oocytes, PfLRR1 (the P. falciparum SDS22/LRR orthologue) interacted with endogenous PP1 and promoted progression through the G2/M cell cycle checkpoint, inducing germinal vesicle breakdown (GVBD), mimicking the effect of PP1 inhibition by okadaic acid or anti-PP1 antibodies. Xenopus oocyte functional assay, GVBD readout, comparison with okadaic acid and anti-PP1 antibody treatment Molecular microbiology Medium 16629662
2007 PF3D7_1432400 (LRR5) was identified as one of 14 LRR-encoding genes in P. falciparum; real-time quantitative PCR showed it is transcribed during the intraerythrocytic lifecycle, with most PfLRR genes highly expressed in late trophozoites and schizonts. Genome analysis, cDNA cloning and sequencing, real-time quantitative PCR Molecular and biochemical parasitology Low 17689674
2022 In P. berghei, the LRR1 orthologue (PbLRR1) forms a complex with PbPP1 in both asexual and sexual stages and inhibits its phosphatase activity. Genetic depletion of PbLRR1 adversely affects oocyst development. Interactome and phospho-proteomics identified novel PbLRR1/PbPP1 partners, and Inhibitor 3 (I3) was found to be hypophosphorylated in PbLRR1-depleted parasites, suggesting the PP1-LRR1 complex controls the phosphorylation status of I3. Co-immunoprecipitation, phosphatase activity assay, genetic knockdown/depletion, interactome (mass spectrometry), phospho-proteomics Open biology High 35920043
2026 Disruption of LRR5 (PF3D7_1432400) in P. falciparum by piggyBac mutagenesis reshapes the parasite transcriptome across multiple intraerythrocytic stages: protein folding, protein export, and host-cell remodeling pathways (including Maurer's cleft components, PTEX export machinery, and HSP70-x) are downregulated, while cytoplasmic heat-shock proteins and translation-associated genes are upregulated. LRR5 disruption also causes premature activation of gametocyte-associated transcriptional programs including elevated Pfs16 protein expression and accelerated transcriptional progression through trophozoite, merozoite, and gametocyte gene clusters. Single-cell RNA sequencing (scRNA-seq) of unsynchronized cultures, pseudotime analysis, Pfs16 protein-level confirmation by immunoassay, isogenic piggyBac mutant (LRR5pB) vs. wild-type NF54 mSphere Medium 42294623

Source papers

Stage 0 corpus · 4 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2006 Regulation of protein phosphatase type 1 and cell cycle progression by PfLRR1, a novel leucine-rich repeat protein of the human malaria parasite Plasmodium falciparum. Molecular microbiology 34 16629662
2007 Census, molecular characterization and developmental expression of Leucine-Rich-Repeat proteins in Plasmodium falciparum. Molecular and biochemical parasitology 7 17689674
2022 Plasmodium berghei leucine-rich repeat protein 1 downregulates protein phosphatase 1 activity and is required for efficient oocyst development. Open biology 5 35920043
2026 Plasmodium falciparum leucine-rich repeat 5 disruption alters the transcription progression during asexual and sexual stage development. mSphere 0 42294623