| Aspect | Summary |
|---|---|
| Identity/domains | Rat **Egfr** (UniProt **G3V6K6**) matches the canonical epidermal growth factor receptor/ErbB1 receptor tyrosine kinase. EGFR is a single-pass transmembrane receptor with an extracellular ligand-binding region containing cysteine-rich subdomains, a transmembrane helix, and an intracellular tyrosine kinase domain with a C-terminal phosphotyrosine tail for adaptor docking. (pqac-00000000, pqac-00000004) |
| Enzymatic activity | EGFR is a **receptor protein-tyrosine kinase** that increases intrinsic kinase activity upon ligand-induced dimerization and catalyzes autophosphorylation on cytoplasmic tyrosines, generating SH2/PTB docking sites for signaling proteins such as GRB2, GAB1, and PLCγ. Key tail phosphosites discussed in recent literature include Y1045, Y1068, Y1086, Y1148, and Y1173; rat phosphoproteomics detected regulated EGFR Y1091 and Y1171. (pqac-00000001, pqac-00000030, pqac-00000028) |
| Activation mechanism | Ligand binding to the extracellular domain induces a conformational change that exposes the dimerization arm, promotes receptor dimerization, and enables asymmetric kinase-domain activation followed by tail autophosphorylation. Recent live-cell studies also show ligand bias: EGF and epiregulin trigger distinct potency/efficacy patterns, with epiregulin at least ~100-fold less potent than EGF for SH2-effector recruitment in one biosensor system. (pqac-00000000, pqac-00000025) |
| Key downstream pathways | Core downstream outputs are **RAS-RAF-MEK-ERK**, **PI3K-AKT-mTOR**, and **PLCγ/IP3-Ca2+** signaling. In native rat IMCD, EGF-responsive phosphoproteomics strongly enriched ErbB, PI3K-Akt, mTOR, endocytosis, and MAPK pathways, supporting conserved pathway usage in rat tissue. (pqac-00000001, pqac-00000027, pqac-00000029) |
| Trafficking regulation | EGFR signaling is shaped by endocytosis and ubiquitin-dependent sorting. **Cbl** and **Cbl-b** are principal E3 ligases for EGFR, but are not fully redundant: Cbl-b preferentially engages pY1045, while Cbl relies more on a GRB2-dependent route; altered ubiquitination affects degradation and endosomal sorting more strongly than initial clathrin-mediated internalization. Ligands also bias fate, with HB-EGF/BTC favoring lysosomal degradation and AREG/TGFα/EPGN favoring recycling. (pqac-00000008, pqac-00000009, pqac-00000011, pqac-00000013) |
| Subcellular localization | EGFR functions primarily at the **plasma membrane** and remains signaling-competent in **early endosomes**; receptors can then recycle or progress to lysosomal degradation. In rat collecting duct, EGFR is reported at the **basolateral plasma membrane**; additional noncanonical trafficking to ER/nuclear membranes and the nucleus has been described in broader EGFR literature. (pqac-00000001, pqac-00000000, pqac-00000003) |
| Rat-specific evidence | In ex vivo native rat IMCD, EGF treatment activated canonical EGFR signaling and altered 254 phosphosites, consistent with a physiological signaling role in epithelial transport regulation. In an in vivo rat 5/6 nephrectomy CKD model, EGFR inhibition with erlotinib reduced proteinuria, serum creatinine, glomerulosclerosis, tubulointerstitial injury, inflammation, and phospho-Akt, supporting functional importance of rat Egfr in renal pathophysiology. (pqac-00000022, pqac-00000019, pqac-00000020) |
| Quantitative data points 2024-2025 | Rat IMCD phosphoproteomics quantified **29,881** phosphosites across **5,457** proteins, with **135 increased** and **119 decreased** after EGF; ErbB signaling showed **p = 8×10^-7** and **5.48-fold enrichment**. EGFR pY1091 increased from about **100 ± 15** to **183 ± 13** by immunoblot, and phosphoproteomics measured EGFR **Y1091 log2 +0.643 (p=0.003)** and **Y1171 log2 +0.473 (p=0.011)**. In 2024 biosensor assays, gefitinib reversed one EGFR SHIP1 readout with **IC50 ~20 nM**, and SH2(Grb2) recruitment occurred within ~4 min and reversed within ~3 min after inhibitor addition. (pqac-00000026, pqac-00000027, pqac-00000028, pqac-00000029, pqac-00000024, pqac-00000032) |
| Applications | Rat Egfr biology is already used in **preclinical pharmacology** and **functional phosphoproteomics**. Erlotinib treatment in rats improved CKD-associated phenotypes, while recent phosphoproteomic/network resources in native rat IMCD provide actionable datasets for pathway modeling, biomarker discovery, and interpreting EGFR-targeted interventions. More broadly, current EGFR research is informing next-generation inhibitors and degraders for resistance biology. (pqac-00000016, pqac-00000022, pqac-00000006) |


*Table: This table summarizes core functional annotation for rat Egfr/EGFR, integrating identity, mechanism, signaling, trafficking, localization, and rat-specific evidence. It is useful as a compact evidence-backed reference for narrative gene-function reporting.*