DENND2B

DENND2B is a multi-substrate DENN-domain guanine nucleotide exchange factor (GEF) that activates several small GTPases—Rab13, Rab10, Rab35, and RhoA—to regulate distinct vesicle trafficking and cytoskeletal processes including cell migration, ciliogenesis, EGFR recycling, and cytokinetic abscission. DENND2B activates Rab13 at the leading edge of migrating cells and interacts with the Rab13 effector MICAL-L2 to remodel the cell periphery and drive invasion (PMID:25713415); it activates Rab35 at the intercellular cytokinetic bridge, functioning as both GEF and effector for Rab35 to recruit ESCRT-III and promote abscission (PMID:37454296); and it activates Rab10 to repress primary ciliogenesis while independently activating RhoA to control cilia length (PMID:35196081). DENND2B also interacts with intersectin-s to promote ligand-free EGFR recycling, an interaction disrupted by protein kinase D phosphorylation upon EGF stimulation (PMID:29030480). Monoallelic loss-of-function variants in DENND2B cause a neurodevelopmental disorder, linking its roles in cell division and ciliogenesis to brain development (PMID:40717498).

1. 1998 Medium

   Establishing that DENND2B (then called ST5) links c-Abl signaling to MAPK/ERK2 activation resolved how this gene product could relay growth-factor signals, revealing that its p126 isoform binds c-Abl via a proline-rich domain and activates ERK2, while the p70 isoform antagonizes this activity.

   Evidence In vitro SH3 binding, transient transfection/ERK2 kinase assays, and deletion mutagenesis in COS-7 cells

   PMID:9632734

   Open questions at the time

   • No endogenous complex validation
   • Mechanism connecting p126 to RAS-ERK pathway intermediates not identified
   • Single lab, single cell type
2. 1999 Low

   Demonstrating that the p70 isoform restores contact-inhibited growth and flattened morphology in HeLa-fibroblast hybrids suggested DENND2B influences cytoskeletal organization and growth control, though without a defined molecular target.

   Evidence Stable transfection in mouse fibroblasts and HeLa-fibroblast hybrids, saturation density and morphology assays

   PMID:10229203

   Open questions at the time

   • Phenotypic readout only; no direct molecular mechanism identified
   • Overexpression system without loss-of-function corroboration
   • Relationship to GEF activity unknown
3. 2000 Medium

   Mapping the C-terminal regulatory domain of p70 as required for RAS-ERK2 inhibition—and showing its deletion converts p70 into a constitutive RAS-ERK2 activator with transforming activity—established an intramolecular autoinhibitory mechanism operating upstream of RAS.

   Evidence Deletion mutagenesis, NIH-3T3 transformation assays, epistasis with dominant-negative RAS/MEK, ERK2 kinase assays

   PMID:10692462

   Open questions at the time

   • No identification of the direct target between p70 and RAS
   • Single lab; no independent replication reported
   • Relationship to DENN-domain GEF activity unresolved
4. 2015 High

   Identifying DENND2B as the GEF for Rab13 at the leading edge of migrating cells—and showing that this activates MICAL-L2-dependent membrane remodeling to drive invasion—established its first characterized Rab substrate and placed it in a defined vesicle-trafficking pathway controlling cell motility.

   Evidence FRET-based Rab13 biosensor, Co-IP with MICAL-L2, knockdown in vitro invasion assays, xenograft in vivo models

   PMID:25713415

   Open questions at the time

   • Cargo identity of Rab13-positive vesicles at the leading edge not defined
   • Whether DENND2B GEF activity toward Rab13 requires post-translational regulation unknown
5. 2017 High

   Showing that DENND2B binds intersectin-s to recycle EGFR to the plasma membrane—and that PKD-mediated phosphorylation of DENND2B upon EGF stimulation dissociates this complex to reroute EGFR toward lysosomal degradation—revealed a phosphorylation-dependent switch controlling receptor fate.

   Evidence Reciprocal Co-IP, phosphorylation assays, EGFR trafficking by fluorescence microscopy, knockdown in multiple cell types

   PMID:29030480

   Open questions at the time

   • Phosphorylation sites on DENND2B not fully mapped
   • Whether Rab13 GEF activity is involved in EGFR recycling not tested
   • In vivo validation absent
6. 2019 Medium

   Demonstrating that DENND2B positively regulates RANKL-driven osteoclastogenesis—via Src/Syk activation, calcium oscillation, and NFATc1 nuclear translocation—extended its functional scope to bone biology, though the direct GTPase target in this context was not identified.

   Evidence siRNA knockdown and overexpression in osteoclast precursors, calcium imaging, kinase activation assays, co-localization with Src

   PMID:31707778

   Open questions at the time

   • Which Rab or GTPase mediates the osteoclast phenotype is unknown
   • Single lab without in vivo bone phenotype data
   • Relationship to DENN-domain GEF activity not tested
7. 2022 High

   A systematic GEF screen revealed that DENND2B is a multi-substrate GEF: it activates Rab10 to repress primary cilia formation and independently activates the non-Rab GTPase RhoA to control cilia length, establishing dual parallel pathways governing ciliogenesis.

   Evidence Cell-based GEF screen of 60 Rabs against DENN-domain proteins, knockdown with ciliogenesis readouts

   PMID:35196081

   Open questions at the time

   • Structural basis for RhoA recognition by a DENN domain unknown
   • Whether Rab10 and RhoA pathways converge downstream not resolved
   • In vivo ciliopathy phenotype not tested
8. 2023 High

   Identifying DENND2B as the GEF for Rab35 at the cytokinetic bridge—where it also acts as a Rab35 effector—and showing that its loss impairs ESCRT-III recruitment, causes F-actin accumulation, and activates the abscission checkpoint, established DENND2B as a central regulator of cytokinetic abscission.

   Evidence GEF activity assays, Co-IP/pulldown for dual GEF-effector interaction, knockdown with live-cell imaging, immunofluorescence for ESCRT-III/Aurora B, multinucleation quantification

   PMID:37454296

   Open questions at the time

   • How DENND2B is recruited to the intercellular bridge is unknown
   • Whether the dual GEF-effector mechanism creates a positive feedback loop not formally tested
   • Relative contributions of Rab35 vs. other substrates to the abscission phenotype not dissected
9. 2026 Medium

   Linking monoallelic loss-of-function DENND2B variants to a neurodevelopmental disorder—with zebrafish validation confirming functional loss for 9 of 10 patient variants—connected its cellular functions in cell division and ciliogenesis to human brain development.

   Evidence Patient variant identification, in silico structural modeling, zebrafish in vivo loss-of-function modeling

   PMID:40717498

   Open questions at the time

   • Specific GTPase substrate(s) responsible for the neurodevelopmental phenotype not identified
   • Mammalian in vivo model (mouse knockout) not reported
   • Whether haploinsufficiency affects ciliogenesis, cell division, or both in neural progenitors is unknown

• It remains unknown how DENND2B selects among its multiple GTPase substrates in different cellular contexts, whether its early-described RAS-ERK signaling functions operate through the same DENN-domain GEF mechanism, and what structural features enable recognition of the non-Rab substrate RhoA.
• No structural model of DENND2B DENN domain bound to any substrate
• Substrate selectivity mechanism across Rab13/Rab10/Rab35/RhoA unresolved
• Integration of GEF-independent scaffolding functions (intersectin-s, c-Abl) with GEF activity not tested