MSP7E

PBANKA_1349200 (MSRP1) is an MSP7-like merozoite surface protein whose characterized biology centers on protein-protein interactions at the host-parasite interface and on transcriptional regulation during sexual commitment (PMID:12477792, PMID:26045295, PMID:41547993). MSRP1 was first identified as an interaction partner of the amino-terminal region of MSP-1, with its expression colocalizing with the MSP-1 N-terminus on the parasite surface (PMID:12477792). In P. berghei, MSRP1 directly binds host P-selectin through its N-terminus, engaging the C-type lectin and EGF-like domains of P-selectin; the resulting complex prevents P-selectin from binding its endogenous carbohydrate ligand Sialyl-Lewis(X), implicating MSRP1 in immunomodulation (PMID:26045295). In P. falciparum, MSRP1 expression is a downstream transcriptional target of the sexual commitment factor AP2-G: a DNA-binding-deficient AP2-G mutant abolishes MSRP1 expression, and MSRP1 expression marks early sexually committed schizonts (PMID:41547993). Genetic deletion of the P. berghei MSP7 family locus encompassing MSRP1 produces no detectable blood-stage or life-cycle phenotype, indicating MSRP1 is dispensable for asexual development in that species (PMID:26222913). Beyond these interaction, regulatory, and dispensability findings, no enzymatic activity or higher-resolution structural mechanism for MSRP1 has been characterized in the available corpus.

1. 2002 Medium

   Establishing whether MSRP1 physically associates with the merozoite surface complex, this work placed MSRP1 as a binding partner of MSP-1 rather than an independent surface protein.

   Evidence Yeast two-hybrid screen, in vitro binding, and immunofluorescence colocalization with the MSP-1 N-terminus in P. yoelii and P. falciparum

   PMID:12477792

   Open questions at the time

   • Binding region on MSRP1 not mapped
   • Functional consequence of the MSP-1 interaction not tested
   • No structural model of the complex
2. 2015 Medium

   Testing whether MSRP1 engages host receptors, this work identified a direct MSRP1-P-selectin interaction that blocks the receptor's natural ligand, proposing an immunomodulatory role at the host interface.

   Evidence Systematic extracellular protein interaction screen and biochemical binding assays in P. berghei, mapping the N-terminus of MSRP1 to the C-type lectin and EGF-like domains of P-selectin

   PMID:26045295

   Open questions at the time

   • Immunomodulatory consequence not demonstrated in vivo
   • Binding stoichiometry and affinity not quantified
   • Relationship between P-selectin binding and MSP-1 association unresolved
3. 2015 Medium

   Assessing whether MSRP1 is required for parasite development, gene family deletion showed it is dispensable for asexual blood-stage growth and life-cycle progression in P. berghei.

   Evidence Triple knockout of msp7/msrp1/msrp2 with life cycle progression assay in P. berghei

   PMID:26222913

   Open questions at the time

   • Family redundancy prevents isolating MSRP1-specific role
   • Sexual-stage and transmission phenotypes not examined
   • Single-gene deletion phenotype not reported
4. 2026 Medium

   Determining how MSRP1 expression is controlled, epistasis analysis placed MSRP1 as a transcriptional target of AP2-G, tying it to the sexual commitment pathway and making it a stage marker.

   Evidence Forward and reverse AP2-G mutation editing (DNA-binding-deficient V2163L versus functional variant) with MSRP1 expression readout in P. falciparum

   PMID:41547993

   Open questions at the time

   • Direct AP2-G promoter binding to MSRP1 not shown
   • Function of MSRP1 in sexual commitment not established
   • Whether the P. berghei ortholog is similarly regulated unknown

• Whether MSRP1's surface MSP-1 association, host P-selectin engagement, and AP2-G-driven sexual-stage expression represent one integrated function or distinct stage-specific roles remains unresolved.
• No molecular activity or enzymatic function defined
• No structural characterization of MSRP1
• Species divergence in role (P. berghei vs P. falciparum) not reconciled