{"uniprot":"Q8TD55","gene":"PLEKHO2","name":"Pleckstrin homology domain-containing family O member 2","organism":"Homo sapiens (Human)","status":"dark","length":490,"sequence":"MEEEGVKEAGEKPRGAQMVDKAGWIKKSSGGLLGFWKDRYLLLCQAQLLVYENEDDQKCVETVELGSYEKCQDLRALLKRKHRFILLRSPGNKVSDIKFQAPTGEEKESWIKALNEGINRGKNKAFDEVKVDKSCALEHVTRDRVRGGQRRRPPTRVHLKEVASAASDGLLRLDLDVPDSGPPVFAPSNHVSEAQPRETPRPLMPPTKPFLAPETTSPGDRVETPVGERAPTPVSASSEVSPESQEDSETPAEEDSGSEQPPNSVLPDKLKVSWENPSPQEAPAAESAEPSQAPCSETSEAAPREGGKPPTPPPKILSEKLKASMGEMQASGPPAPGTVQVSVNGMDDSPEPAKPSQAEGTPGTPPKDATTSTALPPWDLPPQFHPRCSSLGDLLGEGPRHPLQPRERLYRAQLEVKVASEQTEKLLNKVLGSEPAPVSAETLLSQAVEQLRQATQVLQEMRDLGELSQEAPGLREKRKELVTLYRRSAP","function_summary":"A human cytoplasmic scaffold that uses a pleckstrin homology module to dock onto phosphoinositide-rich membrane sites and assemble multiprotein complexes that tune survival pathways in myeloid lineages. By cycling between cytosol and membrane-proximal assemblies, it modulates apoptotic thresholds and interfaces with secretory pathways characteristic of neutrophil and monocyte biology, including trafficking through ficolin-1–rich granules and occasional extracellular exposure via regulated secretion.","plain_language":"PLEKHO2 has barely been studied. The model's best guess: A human cytoplasmic scaffold that uses a pleckstrin homology module to dock onto phosphoinositide-rich membrane sites and assemble multiprotein complexes that tune survival pathways in myeloid lineages. By cycling between cytosol and membrane-proximal assemblies, it modulates apoptotic thresholds and interfaces with secretory pathways characteristic of neutrophil and monocyte biology, including trafficking through ficolin-1–rich granules and occasional extracellular exposure via regulated secretion.","uniprot_summary":"May be involved in myeloid cell apoptosis.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"}],"biological_process":[{"id":"GO:0033028","label":"myeloid cell apoptotic process"}],"cellular_component":[{"id":"GO:0005737","label":"cytoplasm"},{"id":"GO:0030141","label":"secretory granule"},{"id":"GO:1904813","label":"ficolin-1-rich granule lumen"},{"id":"GO:0005576","label":"extracellular region"}]},"interpro":[{"id":"IPR011993","name":"PH-like domain superfamily","type":"homologous_superfamily","start":4,"end":117},{"id":"IPR001849","name":"Pleckstrin homology domain","type":"domain","start":18,"end":121},{"id":"IPR043448","name":"Pleckstrin homology domain-containing family O member 1/2","type":"family","start":1,"end":490}],"reasoning":"I begin with the InterPro architecture. The N-terminus harbors IPR011993 (PH-like domain superfamily, residues 4–117), within which sits a canonical IPR001849 Pleckstrin homology (PH) domain spanning residues 18–121. This tandem of a PH core embedded in a broader PH-like scaffold is followed by a long family-specific region annotated as IPR043448 (Pleckstrin homology domain-containing family O member 1/2, residues 1–490), which covers essentially the full length and signals a conserved, non-enzymatic module specialized for membrane- and signaling-associated interactions. PH domains create a basic, β-sandwich pocket that binds phosphoinositides and often recruits protein partners; this architecture causes avid membrane association and multivalent protein binding rather than catalysis. Consequently, the primary molecular function is mediated through GO:0005515 protein binding, with lipid-anchored scaffolding as the mechanistic basis.\n\nFrom this scaffolded PH platform, I infer the biological role. PH-driven assemblies typically tune receptor and cytoskeletal pathways that govern survival and death decisions in hematopoietic lineages. The family-level signature (IPR043448) ties the protein to a cohort implicated in myeloid signaling. Such scaffolds can bias signaling thresholds that trigger or suppress programmed cell death. This causal chain—PH-mediated membrane recruitment and complex assembly leading to fate-control—aligns with the process formalized as GO:0033028 myeloid cell apoptotic process.\n\nCellular location follows from the same architecture and lineage context. PH-mediated membrane affinity and soluble scaffolding predict a cytosolic pool and peripheral membrane association, consistent with a cytoplasmic residency. In myeloid cells, secretory pathways and specialized granules store and release proteins; the presence of GO:0030141 secretory granule and GO:1904813 ficolin-1-rich granule lumen indicates trafficking through, or cargo within, ficolin-1–rich granules characteristic of neutrophil/monocyte lineages. Such granules can transiently expose their luminal cargo to the extracellular milieu; thus GO:0005576 extracellular region is explained by granule-mediated secretion or surface deposition during inflammatory responses. Together, these compartments situate the protein primarily in the cytoplasm with regulated access to secretory granules and occasional extracellular exposure.\n\nMechanistically, I hypothesize that the PH domain targets phosphoinositide-enriched membrane microdomains, where the protein nucleates complexes that modulate receptor signaling and cytoskeletal dynamics to tune apoptosis in myeloid cells. It likely cycles between cytosol and membrane-adjacent assemblies, and in myeloid lineages it traffics through ficolin-1-rich granules. Likely partners include phosphoinositide-metabolic enzymes and membrane adaptors that together set apoptotic thresholds and coordinate secretion.\n\nTo hypothesize interaction partners: the PH scaffold favors transient complexes with phosphoinositide kinases/phosphatases and membrane adaptors. Candidates include PI3K regulatory subunits and PTEN as lipid-node partners; small GTPases and actin regulators that couple signaling to morphology; and myeloid-specific granule proteins whose luminal pathways route through ficolin-1-rich compartments. These assemblies would causally connect membrane identity to apoptotic control and secretory trafficking in hematopoietic cells.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q8TD55.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q8TD55"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q8TD55/entry","atlas":"/p/Q8TD55"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}