TMEM59

TMEM59 is a type I transmembrane protein that operates across multiple membrane compartments to control protein trafficking, autophagy, signaling, and microglial inflammatory function (PMID:23376921, PMID:20427278, PMID:35606143). In the Golgi it inhibits complex N- and O-glycosylation of APP, retaining APP in the Golgi away from secretases and thereby reducing Abeta generation without affecting bulk Golgi secretion (PMID:20427278). On endosomes, a minimal 19-amino-acid intracellular motif binds directly to the WD-repeat domain of ATG16L1 to drive LC3 labelling and lysosomal targeting of TMEM59-containing compartments, supporting selective autophagy including the response to Staphylococcus aureus infection (PMID:23376921). At the plasma membrane it associates with Frizzled and LRP6 and promotes intramembrane clustering of Wnt-FZD assemblies that subsequently merge with LRP6 to form mature Wnt signalosomes, positively regulating Wnt/beta-catenin signaling (PMID:29632210). In microglia TMEM59 stabilizes the C1q receptor CD93 to enable synaptic pruning, with conditional knockout causing impaired synapse engulfment, increased excitatory transmission, and elevated dendritic spine density (PMID:35606143). It is functionally and physically linked to TREM2, acting downstream of TREM2 to support microglial survival, phagocytosis, and autophagic flux (PMID:32826884), and it restrains neuroinflammation by suppressing NLRP3 inflammasome-mediated pyroptosis and NF-kB activation (PMID:33517129). TMEM59 also binds LAMP2A and HSC70 to negatively regulate chaperone-mediated autophagy, with haploinsufficiency attenuating tau pathology in a transgenic model (PMID:40551290). Its expression is post-transcriptionally controlled through a HOXA5–FTO axis in which FTO-mediated m6A demethylation stabilizes TMEM59 mRNA against YTHDF2-dependent decay (PMID:40772328).

1. 2010 High

   Established a biochemical function for TMEM59 by showing it controls APP maturation, answering how a Golgi transmembrane protein could modulate amyloidogenic processing.

   Evidence Overexpression with glycosylation analysis, Golgi co-localization, secretase cleavage and Abeta ELISA assays with specificity controls

   PMID:20427278

   Open questions at the time

   • Mechanism by which TMEM59 blocks complex glycosylation not defined
   • Whether endogenous TMEM59 regulates APP under physiological levels not tested
   • No direct TMEM59-APP binding interface mapped
2. 2013 High

   Defined TMEM59 as a direct autophagy effector by identifying a minimal motif binding ATG16L1, explaining how an endosomal membrane protein recruits the LC3 machinery to its own compartment.

   Evidence Peptide mapping, mutagenesis of the ATG16L1-binding motif, endogenous Co-IP, and LC3/lysosomal targeting assays during S. aureus infection

   PMID:23376921

   Open questions at the time

   • Structural basis of the motif–WD-repeat interaction not solved
   • Range of physiological cargo targeted via this route unclear
   • Relationship to canonical autophagosome formation not delineated
3. 2018 High

   Placed TMEM59 in Wnt receptor biology by showing it mediates intramembrane Frizzled clustering, addressing how Wnt signalosomes assemble in an ordered manner.

   Evidence Tagged Wnt3a pulldown with MS of endogenous receptor complexes, reciprocal Co-IP, and Wnt reporter assays

   PMID:29632210

   Open questions at the time

   • Molecular determinants of the intramembrane interaction not mapped
   • Whether TMEM59 is required in vivo for Wnt-dependent processes untested
   • Interplay with its Golgi/autophagy roles unknown
4. 2020 Medium

   Connected TMEM59 to the TREM2 pathway in microglia, establishing it as a degradation target and downstream effector of TREM2 signaling.

   Evidence Co-IP, TREM2 overexpression/knockdown, TMEM59 silencing, and microglial functional and autophagy-flux assays

   PMID:32826884

   Open questions at the time

   • Mechanism of TREM2-driven TMEM59 degradation not defined
   • Direct vs indirect TREM2-TMEM59 interaction unresolved
   • Single-lab epistasis without in vivo confirmation
5. 2021 Medium

   Linked TMEM59 to neuroinflammatory cell death by showing it restrains NLRP3 inflammasome-driven pyroptosis and NF-kB activation in ischemic injury.

   Evidence Tmem59 knockout mice in MCAO model and microglial overexpression in OGD/R, with pyroptosis and NF-kB pathway marker analysis

   PMID:33517129

   Open questions at the time

   • No direct molecular interaction established for inflammasome suppression
   • Cell-type specificity of the in vivo effect not isolated
   • Single-lab study without independent replication
6. 2022 High

   Defined a synaptic pruning role by showing TMEM59 stabilizes the C1q receptor CD93 to enable microglial synapse engulfment.

   Evidence Reciprocal Co-IP, microglia-specific conditional knockout, in vivo/in vitro engulfment assays, electrophysiology, and spine density analysis

   PMID:35606143

   Open questions at the time

   • Mechanism by which TMEM59 stabilizes CD93 not defined
   • Whether CD93 stabilization explains all knockout phenotypes unclear
   • Relationship to TMEM59 autophagy function untested
7. 2024 Medium

   Extended TMEM59's anti-inflammatory function beyond microglia by showing a GPR161 interaction that dampens NF-kB activity in epithelial cells.

   Evidence Co-IP, CRISPR/Cas9 knockdown/overexpression, NF-kB reporter assays, and cytokine ELISA in bovine mammary cells

   PMID:38942158

   Open questions at the time

   • Pharmacological/non-neuronal context limits generalizability
   • Direct vs scaffolded GPR161 binding unresolved
   • Single-lab finding without reciprocal validation
8. 2025 Medium

   Identified TMEM59 as a negative regulator of chaperone-mediated autophagy and a modifier of tauopathy by showing it binds LAMP2A and HSC70.

   Evidence Co-IP of TMEM59 with LAMP2A and HSC70, gain/loss-of-function CMA assays, and haploinsufficiency in PS19 tau mice

   PMID:40551290

   Open questions at the time

   • How TMEM59 binding suppresses LAMP2A-mediated CMA mechanistically unclear
   • Reconciliation with TMEM59 promoting other autophagy routes unresolved
   • Single-lab disease-model evidence
9. 2025 Medium

   Revealed upstream control of TMEM59 abundance through a HOXA5–FTO–m6A axis governing mRNA stability and microglial pyroptosis.

   Evidence MeRIP, ChIP, dual luciferase, and RIP assays with MCAO/OGD-R models and flow cytometry for pyroptosis

   PMID:40772328

   Open questions at the time

   • Direct functional consequence of TMEM59 protein levels on pyroptosis effectors not mapped
   • Generality of the m6A regulation beyond stroke unclear
   • Single-lab mechanism without independent replication

• How TMEM59's distinct compartment-specific roles (Golgi glycosylation, endosomal autophagy, Wnt signalosome assembly, CMA suppression, microglial inflammation) are coordinated within one protein, and the structural basis of its membrane interactions, remain unresolved.
• No unified structural model of TMEM59 domains
• No study integrating its opposing autophagy roles
• Regulation switching between compartments unknown