EF-1alpha

PBANKA_1133400 encodes elongation factor 1-alpha (EF-1alpha), which in Plasmodium is present as two identical head-to-head gene copies co-expressed throughout erythrocytic development, consistent with a gene-dosage rather than divergence effect (PMID:9719506). Its expression depends on a conserved GCATAT hexanucleotide cis-element in the intergenic promoter region, whose mutation reduces reporter output in P. berghei (PMID:17313673). Beyond its role in the parasite's own biology, EF-1alpha functions as a secreted immunomodulator: in P. berghei NK65 it is exported via blood-stage extracellular vesicles and directly suppresses host CD4+ T cell responses, promoting dephosphorylation of the TCR signalling molecules PLCγ1, Akt, and ERK; genetic knockout abolishes this immunosuppressive activity in vitro and in vivo, and immunisation with EF-1alpha alone confers durable antiparasite protection (PMID:30835870). No enzymatic translation-elongation role for the Plasmodium protein has been directly characterized in the available corpus.

1. 1998 Medium

   Established the genomic organization and expression pattern of the parasite EF-1alpha locus, showing it exists as duplicated, co-expressed copies rather than a single or divergent gene.

   Evidence Genomic Southern blotting, gene sequencing, RNA expression and codon-usage analysis across Plasmodium species

   PMID:9719506

   Open questions at the time

   • Whether the two copies are functionally redundant was inferred, not tested by copy-specific knockout
   • The promoter architecture (two promoters vs one bidirectional) was proposed but not resolved
   • No protein-level function assigned
2. 2003 Low

   Tested whether EF-1alpha contributes to chloroquine action by asking if it binds the drug-target metabolite FPIX, addressing a candidate antimalarial mechanism.

   Evidence FPIX-affinity extraction from P. falciparum cytosol followed by mass-spectrometry identification

   PMID:12669348

   Open questions at the time

   • Single biochemical pulldown with no mutagenesis or activity assay specific to EF-1alpha; binding judged likely inconsequential by the authors
   • No demonstration that FPIX binding alters any EF-1alpha function
   • Physiological relevance to parasite killing not established
3. 2007 Medium

   Identified the cis-regulatory basis of EF-1alpha expression, defining a conserved promoter motif required for full transcriptional activity.

   Evidence Luciferase reporter transfection with site-directed mutagenesis of the GCATAT motif in the P. berghei EF-1alpha promoter

   PMID:17313673

   Open questions at the time

   • Trans-acting factors binding the GCATAT element were not identified
   • Contribution to endogenous EF-1alpha levels versus reporter output not quantified
4. 2019 High

   Defined a non-canonical, host-directed function for EF-1alpha as a secreted immunosuppressant, explaining how the parasite dampens CD4+ T cell responses and revealing vaccine potential.

   Evidence Genetic knockout in P. berghei NK65 with EV isolation and functional readouts (T cell proliferation, delayed-type hypersensitivity in vivo, phospho-Western for PLCγ1/Akt/ERK), plus vaccination challenge

   PMID:30835870

   Open questions at the time

   • The direct T-cell target or phosphatase-recruiting mechanism driving PLCγ1/Akt/ERK dephosphorylation is not resolved
   • How EF-1alpha is loaded into extracellular vesicles is unknown
   • Whether the P. falciparum ortholog behaves identically was not tested

• The molecular mechanism by which secreted EF-1alpha triggers dephosphorylation of host TCR signalling components, and whether it retains any canonical translation-elongation activity in the parasite, remain open.
• No identified host receptor or phosphatase partner
• No structural basis for the immunosuppressive activity
• No direct assay of translation-elongation function for the Plasmodium protein