DIP2A

DIP2A is a cell-surface receptor for the secreted glycoprotein FSTL1 that transduces pro-survival and pro-angiogenic signaling while also functioning intracellularly to control protein acetylation states (PMID:20054002, PMID:31600191). At the endothelial surface, FSTL1 binding to DIP2A drives Akt phosphorylation to support endothelial cell survival, migration, and tube formation, and protects cardiac myocytes against hypoxia/reoxygenation injury (PMID:20054002); the same axis activates Smad2/3 signaling independently of TGFβR1 to induce VEGF-A and promote angiogenesis, including exercise-induced cardiac angiogenesis after myocardial infarction (PMID:33246164). In tumor cells, the FSTL1–DIP2A axis mediates immunoresistance and supports cancer progression and metastasis (PMID:30110636). DIP2A also acts in the nucleus, where it associates with the HDAC2–DMAP1 complex to promote H3K9Ac deacetylation at the MGMT promoter and repress MGMT transcription, sensitizing glioblastoma cells to temozolomide; FSTL1 competitively binds DIP2A to block its nuclear translocation, derepressing MGMT and conferring drug resistance (PMID:30542120). In neurons, DIP2A binds cortactin through PXXP-motif/SH3-domain contacts to maintain cortactin acetylation, supporting dendritic spine morphogenesis and synaptic transmission, and its loss produces autism-like phenotypes rescuable by acetylation-mimetic cortactin (PMID:31600191). DIP2A additionally supports mitochondrial integrity and antioxidant defense, sustaining SOD activity and limiting ROS in the cerebral cortex (PMID:33781892).

1. 2010 High

   Established the founding molecular identity of DIP2A as the cell-surface receptor through which FSTL1 signals, answering what receptor mediates FSTL1's cytoprotective effects.

   Evidence Co-IP from endothelial membrane fraction plus siRNA knockdown with Akt phosphorylation, survival, migration, tube formation, and apoptosis readouts across endothelial cells and cardiac myocytes

   PMID:20054002

   Open questions at the time

   • No structural basis for the FSTL1-DIP2A interaction
   • Downstream signaling beyond Akt not delineated in this study
2. 2018 High

   Defined a nuclear, chromatin-regulatory role for DIP2A and showed FSTL1 controls its subcellular partitioning, explaining how the FSTL1 axis modulates chemoresistance.

   Evidence Co-IP of DIP2A-HDAC2-DMAP1 complex, subcellular fractionation, ChIP for H3K9Ac at the MGMT promoter, and rescue with DIP2A depletion in glioblastoma models in vitro and in vivo

   PMID:30542120

   Open questions at the time

   • Mechanism of DIP2A nuclear translocation not resolved
   • Whether DIP2A directly contacts chromatin or acts only through HDAC2-DMAP1 unclear
3. 2018 Medium

   Extended the FSTL1-DIP2A axis to tumor immunoresistance, showing tumor-cell DIP2A is required for FSTL1-driven cancer progression.

   Evidence In vivo mouse tumor models with DIP2A manipulation, readouts of progression, metastasis, and immune function

   PMID:30110636

   Open questions at the time

   • Molecular signaling linking DIP2A to immunoresistance not defined
   • Single lab
4. 2019 High

   Identified DIP2A as a regulator of cortactin acetylation via direct domain-level interaction, providing a mechanistic link from DIP2A to synaptic structure and autism-like behavior.

   Evidence Co-IP with PXXP-SH3 domain mapping, Dip2a KO mouse with EM, electrophysiology, behavior, and acetylation-mimetic cortactin rescue

   PMID:31600191

   Open questions at the time

   • How DIP2A maintains cortactin acetylation enzymatically not established
   • Relationship to the surface-receptor function unclear
5. 2019 Low

   Generalized the FSTL1-DIP2A interaction to a hematologic malignancy, linking it to ICAM-1 upregulation and adhesion-mediated drug resistance.

   Evidence Interaction assay, siRNA knockdown, ICAM-1 measurement, proliferation and ADCC assays in DLBCL cells

   PMID:41616470

   Open questions at the time

   • Limited methodological detail in available record
   • Reciprocal interaction validation not described
   • Single lab, single paper
6. 2020 Medium

   Resolved a second signaling output of the FSTL1-DIP2A axis, showing Smad2/3 activation occurs independently of TGFβR1 to drive angiogenesis.

   Evidence Smad2/3 phosphorylation Western blotting, TGFβR1 inhibitor dissection, HUVEC tube formation, and in vivo rat MI model with AAV-FSTL1

   PMID:33246164

   Open questions at the time

   • How DIP2A couples to Smad2/3 without a TGFβ receptor unknown
   • Single lab
7. 2021 Medium

   Revealed a mitochondrial/antioxidant function for DIP2A, showing it sustains SOD activity and limits ROS to preserve mitochondrial integrity.

   Evidence Dip2a KO mouse cortex with SOD activity, ROS measurement, EM, metabolic profiling, and in vitro gain-of-function ROS scavenging

   PMID:33781892

   Open questions at the time

   • Molecular mechanism connecting DIP2A to SOD activity unknown
   • Whether mitochondrial role is direct or secondary unresolved
8. 2024 Medium

   Mapped DIP2A to a defined neural circuit, linking its loss to neurotransmitter metabolic dysregulation and depression-like behavior.

   Evidence Cell-type-specific Dip2a KO in basolateral amygdala excitatory neurons, targeted metabolomics, tail suspension test, and immunofluorescence localization

   PMID:39104112

   Open questions at the time

   • Causal molecular link between DIP2A and tryptophan/thyroxine metabolism not defined
   • Single lab, single paper

• How DIP2A's surface-receptor, nuclear chromatin, cortactin-regulatory, and mitochondrial functions are biochemically unified within one protein remains unresolved.
• No structural model of DIP2A
• No defined catalytic activity reconciling its diverse roles
• Mechanism of subcellular partitioning between membrane and nucleus incompletely characterized