AKAL

AKAL (PF3D7_0512900) is an atypical AKAP-like protein of Plasmodium falciparum expressed in mature asexual stages, merozoites, and gametocytes (PMID:27129434). Despite its AKAP-like designation, AKAL does not anchor the PKA regulatory subunit directly; instead it binds Pf14-3-3I, which in turn associates with PfPKA-R, placing AKAL only indirectly within the PKA signaling network (PMID:27129434). AKAL is itself not a PKA substrate in vitro, whereas its partners Pf14-3-3I and PfPKA-R are phosphorylated by PKA, indicating that regulation of this assembly acts on the partners rather than on AKAL (PMID:27129434). Consistent with a non-canonical role, AKAL harbors a conserved nucleotide-binding pocket that binds AMP and cAMP, pointing toward a function in cAMP/AMP-related metabolism or signaling rather than classical PKA anchoring (PMID:27129434). Beyond these interaction and biochemical observations, no functional phenotype or in vivo role for AKAL has been characterized in the available corpus.

1. 2016 Medium

   Establishing where and when AKAL is present was needed before any functional role could be assigned; expression was mapped across parasite life-cycle stages.

   Evidence RT-qPCR and immunofluorescence in P. falciparum 3D7

   PMID:27129434

   Open questions at the time

   • No functional consequence tied to the observed stage expression or localization
   • Subcellular localization not resolved to a specific compartment
2. 2016 Medium

   The central question was whether an AKAP-like protein anchors PKA in P. falciparum; interaction studies showed AKAL does not bind PfPKA-R directly but connects via Pf14-3-3I, redefining it as an atypical, indirect participant in PKA signaling.

   Evidence Reciprocal pull-downs with recombinant AKAL, proteomic identification, and IFA colocalization in P. falciparum 3D7

   PMID:27129434

   Open questions at the time

   • Functional significance of the AKAL–Pf14-3-3I interaction in vivo not tested
   • Stoichiometry and interface of the AKAL–Pf14-3-3I–PfPKA-R assembly unresolved
3. 2016 Medium

   To probe how the complex is regulated, phosphorylation was tested; AKAL is not a PKA substrate whereas Pf14-3-3I and PfPKA-R are, implying control acts on the partners rather than AKAL itself.

   Evidence Radiolabel in vitro kinase assay

   PMID:27129434

   Open questions at the time

   • In vitro result not confirmed in cellular context
   • Whether AKAL is modified by other kinases untested
4. 2016 Low

   Whether AKAL has an intrinsic biochemical activity beyond scaffolding was addressed by identifying a nucleotide-binding pocket that binds AMP and cAMP, hinting at a role in cAMP/AMP metabolism or signaling.

   Evidence Qualitative nucleotide-binding experiments supported by a computational structural model

   PMID:27129434

   Open questions at the time

   • Qualitative binding not validated by quantitative affinity or enzymatic assays
   • No demonstrated catalytic or signaling output from nucleotide binding
   • Structural pocket inferred from modeling, not an experimental structure

• The in vivo role of AKAL, the functional consequence of its AMP/cAMP binding, and its contribution to parasite biology remain unresolved.
• No genetic knockout or knockdown phenotype for AKAL reported
• No demonstrated link between nucleotide binding and a metabolic or signaling pathway
• No experimental structure of AKAL or its complexes