ARP

PfARP (PF3D7_0909300), designated an apoptosis-related protein of P. falciparum, is a cytosolic protein of ~24 kDa subunit mass with a predominantly alpha-helical secondary structure (61% alpha-helix, 15% beta-sheet by CD), expressed at ring and trophozoite stages with highest abundance at the trophozoite stage and minimal expression in schizonts (PMID:17182255). Its expression is up-regulated by bilirubin-induced oxidative stress, concurrent with induction of caspase-like protease activity and loss of mitochondrial membrane potential, linking it to pro-apoptotic stress responses in the parasite (PMID:18070610). Beyond this stress-responsive expression profile and its cytosolic localization, no direct molecular function, binding partner, or substrate of PfARP has been characterized in the available corpus.

1. 2006 Medium

   Establishing whether PfARP is a real, folded protein and where it resides addressed the basic question of its physical identity and cellular compartment, prerequisites for any functional model.

   Evidence recombinant overexpression, purification, CD spectroscopy, RT-PCR and immunofluorescence in P. falciparum

   PMID:17182255

   Open questions at the time

   • no molecular activity or biochemical function demonstrated
   • no interacting partners or substrates identified
   • stage-specific role of cytosolic localization not defined
2. 2007 Low

   Whether PfARP responds to death-inducing stimuli was tested by monitoring its expression under oxidative stress, connecting the protein to a candidate parasite cell-death pathway.

   Evidence expression analysis under bilirubin treatment alongside caspase-like protease and mitochondrial membrane potential assays in P. falciparum

   PMID:18070610

   Open questions at the time

   • only expression up-regulation observed, with no direct functional or loss-of-function experiment on PfARP itself
   • causal role of PfARP in the caspase-like/mitochondrial cascade not established
   • no evidence PfARP acts within, rather than merely correlates with, the death response

• The molecular activity of PfARP and its mechanistic position in parasite cell-death signaling remain unknown.
• no biochemical activity, substrate, or binding partner identified
• no genetic loss-of-function or rescue linking PfARP to a phenotype
• no structural model beyond secondary-structure composition