GBP130

GBP130 (PF3D7_1016300) is a Plasmodium falciparum blood-stage protein that operates at the interface between the parasite and host erythrocytes and immune cells (PMID:6206188, PMID:42206825). During merozoite invasion it localizes to the merozoite surface coat and binds the erythrocyte sialoglycoprotein glycophorin in a saturable manner; antibodies against it block both glycophorin binding and invasion (PMID:6206188). Its glycophorin-binding activity is carried by a tandemly repeated 50-amino-acid sequence, and binding scales with the number of repeats, while repeat-specific antibodies inhibit erythrocyte invasion (PMID:3883491, PMID:3512098); antibodies against a defined N-terminal region (aa 111-374) likewise inhibit invasion (PMID:38863702). Transcription of GBP130 is developmentally controlled through cis-regulatory architecture on chromosome 10, including a five-base-pair promoter element that binds sequence-specific nuclear factors and a TATA box-like element bound by the P. falciparum TATA-binding protein PfTBP, with stage restriction linked to phased nucleosomal arrays over the endogenous locus (PMID:10215026, PMID:15760658, PMID:11269326). Beyond its invasion role, GBP130 is displayed on the surface of infected RBCs, where it directly binds the I-domain of the integrin LFA-1 and drives LFA-1-dependent NK cell activation, degranulation, and contact-dependent killing of infected erythrocytes (PMID:42206825). An early cautionary study showed the glycophorin-coupled AE-BioGel matrix used to define binding has intrinsic ion-exchange properties that can produce non-specific binding, qualifying the affinity-matrix data (PMID:3298526).

1. 1984 Medium

   Established that GBP130 is a merozoite-surface protein with a defined host-receptor binding activity, raising the possibility that it participates in erythrocyte invasion.

   Evidence Glycophorin-matrix affinity binding, immunoelectron microscopy, and antibody invasion-inhibition in P. falciparum

   PMID:6206188

   Open questions at the time

   • Affinity-matrix binding later shown to be subject to non-specific artifact
   • No mapping of the binding domain at this stage
2. 1986 High

   Localized the glycophorin-binding function to a tandem 50-amino-acid repeat and showed binding depends on repeat number, defining the molecular basis of receptor engagement and its inhibition.

   Evidence cDNA cloning/sequencing and recombinant expression of variable repeat numbers with glycophorin binding and repeat-specific antibody invasion inhibition in P. falciparum

   PMID:3512098 PMID:3883491

   Open questions at the time

   • Structural basis of repeat-glycophorin interaction unresolved
   • Contribution of non-repeat regions to invasion not defined here
3. 1987 Medium

   Questioned the specificity of the primary assay used to characterize GBP130 binding by showing the affinity matrix itself binds proteins non-specifically.

   Evidence Glycophorin-coupled AE-BioGel binding assay with and without glycophorin under varying ionic conditions in P. falciparum

   PMID:3298526

   Open questions at the time

   • Does not overturn the antibody-based invasion inhibition data
   • Extent of artifact for GBP130 specifically not quantified
4. 1990 Low

   Tested whether GBP130 physically partners with the major merozoite surface glycoprotein Pf200 and found no stable proximal complex under crosslinking conditions.

   Evidence Chemical crosslinking, immunoprecipitation, and immunoblotting in P. falciparum

   PMID:2404782

   Open questions at the time

   • Single method negative result; absence of crosslinking does not exclude transient association
   • No reciprocal or alternative interaction screen
5. 1992 Medium

   Defined the genomic and transcriptional context of GBP130, showing it is monocistronically transcribed within a chromosome-10 gene cluster.

   Evidence YAC mapping and nuclear run-on transcription assay in P. falciparum

   PMID:1374714

   Open questions at the time

   • Regulatory elements not yet identified
   • Functional consequence of the clustered arrangement unknown
6. 1999 Medium

   Identified cis-regulatory and chromatin determinants of GBP130 expression, linking developmental stage restriction to a discrete promoter element and to phased nucleosomal arrays.

   Evidence Promoter mutagenesis with reporter assays and EMSA, plus episomal vs chromosomal promoter comparison with nucleosome positioning in P. falciparum

   PMID:10215026 PMID:11269326

   Open questions at the time

   • Identity of the sequence-specific nuclear factor not determined
   • Mechanistic link between nucleosome phasing and stage timing not resolved
7. 2002 Low

   Proposed that 5' UTR length and poly(dA:dT) tracts tune stage-specific promoter output for GBP130.

   Evidence Promoter/5' UTR deletion CAT reporter constructs at defined developmental stages in P. falciparum

   PMID:12567560

   Open questions at the time

   • Single reporter method with limited controls
   • Endogenous relevance of 5' UTR length variation not confirmed
8. 2005 Medium

   Placed GBP130 transcription within basal machinery by demonstrating PfTBP binding to a TATA box-like element in its promoter.

   Evidence EMSA supershift, DNase I footprinting with GST-PfTBP, and ChIP in P. falciparum

   PMID:15760658

   Open questions at the time

   • Functional requirement of PfTBP occupancy for GBP130 expression not tested
   • Interplay with the five-base-pair element unresolved
9. 2017 Medium

   Dissected the unusually extended signal peptide and showed its N-terminal extension is dispensable for secretory-pathway entry.

   Evidence Signal peptide deletion mutagenesis fused to fluorescent reporters imaged in P. falciparum and mammalian cells

   PMID:28750796

   Open questions at the time

   • Alternative function of the extended N-terminus not identified
   • No effect on trafficking of native full-length GBP130 tested
10. 2024 Medium

    Identified a discrete invasion-relevant epitope region (aa 111-374) whose antibodies block invasion, supporting GBP130 as a vaccine-relevant invasion antigen.

    Evidence Mouse immunization with mRNA, DNA, and recombinant protein immunogens and in vitro growth/invasion inhibition assays for P. falciparum

    PMID:38863702

    Open questions at the time

    • Mechanism of inhibition by this region not defined
    • Receptor engaged by the aa 111-374 region not established
11. 2026 High

    Revealed a second, immune-facing role for GBP130 as an infected-RBC surface ligand for the LFA-1 integrin that triggers NK-cell killing of infected erythrocytes.

    Evidence LFA-1 alphaI-Fc pulldown with LC-MS/MS, recombinant binding assays, and NK/THP-1 co-culture activation, degranulation and neutralization assays with P. falciparum iRBCs

    PMID:42206825

    Open questions at the time

    • Structural basis of GBP130-LFA-1 alphaI binding not resolved
    • How merozoite-surface GBP130 relates to iRBC-surface display not established
    • In vivo relevance of NK-mediated killing not tested

• It remains unknown how GBP130's two receptor engagements (glycophorin during invasion versus LFA-1 on the infected-RBC surface) are structurally and temporally coordinated, and whether the tandem repeat and the aa 111-374 region contribute to each function.
• No structural model of any GBP130 domain
• No genetic knockout/knockdown phenotype in the corpus
• Domain assignment for LFA-1 binding not mapped