EPS8L2

EPS8L2 is an actin-binding adaptor protein that couples receptor tyrosine kinase signaling to Rac-dependent actin remodeling: it binds F-actin in vivo, interacts with Abi1 and Sos-1, activates the Rac-GEF activity of Sos-1, localizes to PDGF-induced actin-rich membrane ruffles, and restores RTK-mediated actin remodeling in eps8-/- fibroblasts (PMID:14565974). Consistent with this actin-organizing role, EPS8L2 directly interacts with the nuclear envelope phosphatase Ctdnep1 to build the dorsal actin cables that support TAN line engagement during nuclear movement in migrating fibroblasts, thereby controlling nuclear positioning and cell migration (PMID:33567288). In the inner ear, EPS8L2 localizes to stereocilia tips and is required for long-term maintenance of the staircase structure of auditory hair bundles, with its loss causing progressive late-onset hearing loss; it is functionally redundant with Eps8, as loss of both collapses the ordered hair bundle (PMID:23918390), and at the tips of shorter-row mechanotransducing stereocilia it is a component of a 'row 2 protein complex' through direct binding to BAIAP2L2 (PMID:34346063). In colorectal cancer cells, EPS8L2 drives a signaling cascade by enhancing the YBX1-S6K1 interaction to increase YBX1 phosphorylation, promoting nuclear YBX1, G3BP2 transcription, MAPK activation, and tumor cell proliferation and migration (PMID:40783393).

1. 2003 High

   Established EPS8L2's core molecular function by placing it in the RTK→Rac→actin remodeling pathway as an actin-binding adaptor that activates a Rac-GEF.

   Evidence Co-IP with Abi1 and Sos-1, in vivo actin-binding assay, Rac-GEF activity assay, and rescue in eps8-/- fibroblasts with localization to PDGF-induced ruffles

   PMID:14565974

   Open questions at the time

   • Structural basis of EPS8L2 binding to Abi1/Sos-1 not resolved
   • Degree of functional redundancy with Eps8 in fibroblasts not quantified
2. 2007 Medium

   Probed whether the EPS8L2 SH3 domain reads phosphorylation-regulated motifs at receptor complexes, showing it engages a proline-rich PxxDY motif of CD3epsilon in a phospho-switch manner.

   Evidence SH3 phage display screen, recombinant binding assay, and peptide spot filter assay with phosphorylated peptides

   PMID:17617578

   Open questions at the time

   • Binding was only modest relative to Eps8/Eps8L1
   • No cellular validation in T cells
   • Functional consequence at the TCR not established
3. 2013 High

   Defined an in vivo organismal role: EPS8L2 maintains the stereocilia staircase of auditory hair bundles, linking its actin function to hearing.

   Evidence Eps8L2 knockout mouse with auditory brainstem response testing, electron microscopy of hair bundles, and genetic epistasis with Eps8 knockout

   PMID:23918390

   Open questions at the time

   • Molecular mechanism by which EPS8L2 maintains (vs. forms) bundle architecture unresolved
   • Binding partners at the tip not identified in this study
4. 2019 Medium

   Connected EPS8L2 abundance in extracellular vesicles to exocyst and primary cilia activity, implicating it in ciliary/EV trafficking outputs.

   Evidence EXOC5 KD/OE in MDCK cells, IFT88 KO, and immunoblotting of isolated EVs plus a tubule-specific EXOC5 KO mouse

   PMID:31694916

   Open questions at the time

   • No direct test of EPS8L2 function in EVs
   • Mechanism of EPS8L2 sorting into EVs unknown
   • Causal versus correlative relationship to cilia not distinguished
5. 2021 High

   Identified a direct EPS8L2-Ctdnep1 interaction required for dorsal actin cable formation and nuclear positioning, generalizing EPS8L2's actin-organizing role to nuclear movement during migration.

   Evidence Reciprocal endogenous Co-IP, siRNA knockdown with nuclear positioning assay, live-cell imaging of actin cables/TAN lines, and migration assay

   PMID:33567288

   Open questions at the time

   • How a nuclear envelope phosphatase recruits EPS8L2 to dorsal cables mechanistically unclear
   • Whether Ctdnep1 phosphatase activity is required not established
6. 2021 Medium

   Placed EPS8L2 within a defined 'row 2 protein complex' at mechanotransducing stereociliary tips via direct binding to BAIAP2L2.

   Evidence Co-IP, immunofluorescence in cochlear hair cells, and Baiap2l2 knockout mouse with MET current recordings and FM 1-43FX uptake

   PMID:34346063

   Open questions at the time

   • Stoichiometry and architecture of the row 2 complex unresolved
   • EPS8L2's specific contribution within this complex not isolated
7. 2025 Medium

   Extended EPS8L2 beyond cytoskeletal roles into oncogenic signaling, showing it scaffolds a YBX1-S6K1-G3BP2-MAPK axis driving colorectal cancer growth.

   Evidence EPS8L2 OE/KD in CRC lines, Co-IP of EPS8L2-YBX1-S6K1, YBX1 phosphorylation and nuclear fractionation, G3BP2 reporter, AOM/DSS Eps8l2 KO mouse, and patient-derived organoids

   PMID:40783393

   Open questions at the time

   • How the actin-adaptor function relates to YBX1-S6K1 scaffolding unclear
   • Direct versus indirect role in promoting the YBX1-S6K1 interaction not dissected
   • Single lab, not independently replicated

• Whether EPS8L2's actin-remodeling activity and its signaling-scaffold functions reflect a single biochemical mechanism or context-specific partnerships remains unresolved.
• No structural model unifying its SH3/actin-binding and scaffolding roles
• No reconstitution of EPS8L2-dependent actin cable assembly
• Quantitative redundancy with Eps8/Eps8L1 across tissues not mapped