STOM

STOM (stomatin/EPB72) is a lipid-raft-associated, monotopic membrane protein with an SPFH domain that functions as a multi-target regulator of membrane channels, transporters, and lysosomal/membrane homeostasis (PMID:32012213, PMID:33531346, PMID:35663930). As a channel regulator, it binds the distal C-terminus of acid-sensing ion channel ASIC3 and, through its first transmembrane domain, stabilizes the channel's desensitized state to inhibit gating without altering surface expression (PMID:32012213), and in red blood cells it physically associates with Pannexin 1 to promote pore opening through a caspase-independent mechanism (PMID:36012667). STOM also restrains the glucose transporter GLUT1, with PON2 relieving this inhibition to permit glucose uptake in B-ALL cells (PMID:33531346). At lysosomes, STOM drives degradative and membrane-permeabilization programs: it interacts with Prdx1 to promote its lysosomal degradation, elevating ROS to activate osteoclastogenesis (PMID:40595453), and partners with DRAM upon fatty-acid stimulation to enhance lysosomal membrane permeabilization and exosome secretion from hepatocytes (PMID:34731006). Structurally, the SPFH domain harbors a cryptic phosphate-binding pocket and forms fibril-like assemblies whose dissolution is inhibited by phosphate, linking phosphate sensing to oligomerization (PMID:35663930). STOM ciliary localization in olfactory sensory neurons depends on STOML3 (PMID:35794236). The EPB72 gene maps to 9q34.1 and has a TATA-less, housekeeping-type promoter (PMID:8825639, PMID:8500356).

1. 1993 Medium

   Establishing the chromosomal location and genomic organization of the stomatin gene provided the molecular foundation for studying the protein and its disease associations.

   Evidence Southern blot of somatic cell hybrid panels mapping EPB72 to 9q34.1, followed by genomic cloning and promoter analysis

   PMID:8500356 PMID:8825639

   Open questions at the time

   • Promoter elements identified by sequence only, not functionally validated
   • No link to protein function established at this stage
2. 2011 Medium

   The question of whether STOM has a role in host defense was addressed by showing its loss permits intracellular bacterial growth, implicating STOM in restricting pathogen replication.

   Evidence SILAC proteomics with siRNA knockdown and intracellular Salmonella replication/microcolony imaging in epithelial cells

   PMID:21919203

   Open questions at the time

   • Molecular mechanism of restriction unknown
   • No direct STOM-pathogen interaction defined
   • Single lab, single phenotype class
3. 2020 High

   The mechanism by which STOM inhibits an ion channel was resolved, showing it binds the ASIC3 C-terminus and uses TM1 to stabilize the desensitized state rather than altering trafficking.

   Evidence Chimeric channel analysis, patch-clamp, FRET, and site-directed mutagenesis in heterologous expression

   PMID:32012213

   Open questions at the time

   • No structure of the STOM-ASIC3 complex
   • Stoichiometry of regulation undefined
   • Physiological context in native neurons not tested
4. 2021 High

   STOM was placed in glucose metabolism as a brake on GLUT1, with genetic epistasis showing PON2 relieves this inhibition in leukemia cells.

   Evidence STOM genetic deletion and epistasis rescue of PON2-deficient glucose uptake in murine and human B-ALL cells

   PMID:33531346

   Open questions at the time

   • Direct STOM-GLUT1 physical interaction not biochemically resolved
   • Mechanism of PON2-mediated release unknown
5. 2021 Medium

   STOM was connected to lysosomal membrane dynamics and inflammatory signaling through distinct partners, defining roles in exosome secretion and CD36 regulation.

   Evidence Co-IP plus DRAM knockout mouse and lysosome-inhibitor rescue for exosome secretion; RIP and CD36-overexpression rescue in LPS-treated lung epithelial cells

   PMID:34731006 PMID:34934440

   Open questions at the time

   • Mechanism by which STOM permeabilizes lysosomal membranes undefined
   • Nature of the STOM-CD36 RNA/protein interaction unclear
   • Both from single labs
6. 2022 Medium

   Structural and additional interaction studies expanded STOM's mechanistic picture, revealing a phosphate-sensitive SPFH oligomerization domain, a role in Pannexin 1 pore opening, STOML3-dependent ciliary targeting, and a candidate toxin-capture interaction.

   Evidence NMR structure with fibril/phosphate assays; PLA and loss-of-function in OHSt RBCs and K562; immunofluorescence in STOML3-deficient mice; Co-IP/pull-down with H. pylori VacA

   PMID:35663930 PMID:35794236 PMID:35912184 PMID:36012667

   Open questions at the time

   • Phosphate-binding site not validated by mutagenesis
   • Mechanism linking STOM to PANX1 opening undefined
   • VacA interaction based on single Co-IP/pull-down with speculative interpretation
7. 2025 High

   A lysosomal-degradation mechanism linking STOM to redox-driven bone resorption was established, defining Prdx1 as a STOM target and STOM as a driver of osteoclastogenesis.

   Evidence Reciprocal Co-IP, STOM-deficient mice, lysosomal pathway inhibition, ROS measurement, and osteoclast differentiation assays

   PMID:40595453

   Open questions at the time

   • How STOM routes Prdx1 to lysosomes mechanistically is unresolved
   • Whether ROS elevation is solely Prdx1-dependent untested

• It remains unknown how STOM achieves selectivity across its diverse targets (ion channels, transporters, lysosomal substrates) and whether its SPFH-domain oligomerization underlies a unified scaffolding mechanism.
• No unifying structural model of STOM target engagement
• No reconstituted system linking oligomerization state to regulatory output
• Tissue-specific partner repertoires uncharacterized