| 1995 |
Rabaptin-5 (RABEP1) is a direct effector of GTP-bound Rab5 that is required for early endosome membrane docking and fusion. It is mainly cytosolic but colocalizes with Rab5 on early endosomes; Rab5 recruits it to purified early endosomes in a GTP-dependent manner, and immunodepletion of rabaptin-5 from cytosol strongly inhibits Rab5-dependent early endosome fusion. |
Co-immunoprecipitation, immunodepletion from cytosol, in vitro endosome fusion assay with purified early endosomes, overexpression with morphological readout (endosome enlargement) |
Cell |
High |
8521472
|
| 1997 |
Rabaptin-5 forms a tight physical complex with Rabex-5, a novel 60 kDa Rab5 GDP/GTP exchange factor homologous to yeast Vps9p. This complex is essential for endocytic membrane fusion; Rabex-5 displays GDP/GTP exchange activity on Rab5 upon membrane delivery, and the complex stabilizes Rab5 in the GTP-active state. |
Nanoelectrospray mass spectrometry identification, biochemical co-purification, in vitro nucleotide exchange assay, cell-free endosome fusion assay |
Cell |
High |
9323142
|
| 1997 |
Rabaptin-5 is cleaved by caspase-family proteases during apoptosis, and this selective cleavage is responsible for the block in endosome fusion observed in apoptotic cells. Cleavage was shown in a cell-free Xenopus egg-extract apoptosis system and in cellular apoptosis models; Bcl-2/Bcl-xL or caspase inhibitors prevented both cleavage and fusion inhibition. |
Cell-free Xenopus egg-extract apoptosis system, immunoblot detection of cleavage, caspase inhibitors, Bcl-2/Bcl-xL rescue, endosome fusion assay |
The EMBO journal |
High |
9321397
|
| 1998 |
Rabaptin-5 contains two distinct Rab-binding domains: a 73-residue C-terminal region necessary and sufficient for interaction with GTP-bound Rab5 and Rab5-dependent recruitment to early endosomes, and an N-terminal domain that mediates direct interaction with GTP-bound Rab4. Native cytosolic Rabaptin-5 exists as a homodimer dependent on its coiled-coil sequences. |
Deletion mutagenesis, GST pulldown assays, yeast two-hybrid, immunofluorescence colocalization, gel filtration (native complex analysis) |
The EMBO journal |
High |
9524117
|
| 1998 |
Rabaptin-5 interacts with the neuronal growth-associated protein GAP-43 in a Ca2+-dependent manner, and this interaction modulates endocytosis and synaptic vesicle recycling in neurons. |
Yeast two-hybrid, co-immunoprecipitation, endocytosis assays in neuronal cells, overexpression studies |
The Journal of neuroscience |
Medium |
9742146
|
| 2001 |
When physically associated in a complex, Rabaptin-5 increases the nucleotide exchange activity of Rabex-5 on Rab5. Rab5-dependent recruitment of Rabaptin-5 to early endosomes is completely dependent on its physical association with Rabex-5, and complex formation is essential for early endosome homotypic fusion. |
Reconstitution with recombinant proteins, in vitro GEF assay, endosome recruitment assay, cell-free endosome fusion assay |
Molecular biology of the cell |
High |
11452015
|
| 2001 |
Rabaptin-5 interacts with Rab33b (a Golgi-specific Rab) in its GTP-bound form, suggesting Rabaptin-5 functions not only in the endocytic pathway but also at the Golgi. The interaction was demonstrated by GST-Rab33b pulldown with detection by Western blot and mass spectrometry. |
GST-Rab33b (GTP-locked) pulldown, Western blot, mass spectrometry |
FEBS letters |
Low |
11718716
|
| 2001 |
Rabphilin dissociated from Rab3 promotes endocytosis through direct interaction with Rabaptin-5. The Rabphilin V61A mutant (unable to bind Rab3) interacts with Rabaptin-5 and enhances transferrin internalization, whereas Rabphilin L83A fails to bind Rabaptin-5 and does not stimulate endocytosis. |
Co-immunoprecipitation, transferrin endocytosis assay, point-mutant analysis, overexpression in secretory cells |
Journal of cell science |
Medium |
11309205
|
| 2002 |
Gamma1-adaptin (a subunit of the AP-1 clathrin adaptor complex at the TGN) directly interacts with Rabaptin-5 through its ear domain binding to the C-terminal coiled-coil region of Rabaptin-5. The two proteins colocalize on perinuclear structures (recycling endosomes) and redistribute to cytoplasm upon brefeldin A treatment. |
Yeast two-hybrid, GST pulldown, co-immunoprecipitation, immunofluorescence colocalization |
Journal of biochemistry |
Medium |
11872161
|
| 2003 |
GGAs (Arf-dependent clathrin adaptors) interact with the Rabaptin-5-Rabex-5 complex via a bipartite mechanism: GGA-GAE domains recognize the FGPLV sequence (residues 439-443) in Rabaptin-5 (also recognized by gamma1- and gamma2-adaptin ears), while GGA-GAT domains bind the C-terminal coiled-coils of Rabaptin-5. GFP-Rabaptin-5 overexpression shifts GGA1 and associated cargo to enlarged early endosomes. |
Co-immunoprecipitation, GST pulldown, site-directed mutagenesis of FGPLV motif, immunofluorescence relocalization assay |
The EMBO journal |
High |
12505986
|
| 2003 |
The GGA1 GAT domain binds Rabaptin-5 through a hydrophobic surface patch on its C-terminal three-helix bundle. The N284S mutation in this patch reduces Rabaptin-5 binding, and the reciprocal S293N mutation in GGA3 partially confers Rabaptin-5 binding; binding of GAT to Rabaptin-5 is independent of its interaction with ARF. |
Crystal structure of GGA1 GAT domain, site-directed mutagenesis, in vitro binding assays |
Biochemistry |
High |
14636058
|
| 2004 |
Rabaptin-5/Rabex-5 complex negatively regulates AP-1/clathrin-coated vesicle formation from endosomes in a Rab4-dependent recycling pathway. Depletion of rabaptin-5/rabex-5 from cytosol stimulated recycling vesicle production, while addition of purified protein strongly inhibited it; Rab4, but not Rab5, was required for this process. |
In vitro vesicle formation assay using surface-biotinylated receptor, immunodepletion from cytosol, add-back of purified protein, brefeldin A inhibition |
Molecular biology of the cell |
High |
15331762
|
| 2005 |
The Rabaptin-5δ isoform interacts with GTP-bound Rab5 but not with Rab4, unlike full-length Rabaptin-5 which binds both. This is due to a disrupted Rab4 binding site caused by the alternative splicing deletion, confirmed by yeast two-hybrid, GST pulldown, and immunofluorescence colocalization. |
Yeast two-hybrid, GST pulldown, immunofluorescence colocalization in BHK-21 cells |
The FEBS journal |
Medium |
15634330
|
| 2006 |
Rabaptin-5 exists as a dimer in cells, and its δ and γ isoforms also form dimers, providing the first direct evidence for Rabaptin-5 dimerization in a cellular context. Dimerization was established using biochemical cross-linking and co-immunoprecipitation approaches. |
Co-immunoprecipitation, cross-linking, biochemical fractionation |
Biochemistry. Biokhimiia |
Low |
17223781
|
| 2006 |
Rabaptin-5γ and Rabaptin-5δ isoforms are cleaved by caspase-3-related proteases in apoptotic cell extracts, and both contain an N-terminal Rab5 binding site that becomes physically separated from the C-terminal Rab5 binding site after apoptotic cleavage, providing a mechanistic model for inactivation of endosome fusion. |
In vitro cleavage by caspase-3 in cell extracts, immunoblot detection of cleavage products, mapping of Rab5 binding sites on deletion mutants |
Cell cycle (Georgetown, Tex.) |
Medium |
16861912
|
| 2007 |
Rabex-5 can target to early endosomes and activate Rab5 in vivo via an early endosomal targeting (EET) domain (residues 81-230) that is independent of its Rabaptin-5-binding domain; Rabaptin-5 is therefore not required for Rabex-5 membrane targeting and Rab5 activation in vivo, despite being required in vitro. |
Deletion mutagenesis of Rabex-5, fluorescence microscopy of GFP-tagged constructs, Rab5-GTP activation assays in cells |
Molecular biology of the cell |
Medium |
17699593
|
| 2008 |
In mast cells, Rabaptin-5 knockdown reduces surface expression of FcεRI and β1 integrin (by diminishing receptor surface stability) but does not impair FcεRI internalization or endosome fusion. This receptor surface stabilization function of Rabaptin-5 reduces mast cell sensitivity to antigen-induced mediator release and Ag-induced adhesion/migration. |
shRNA knockdown, flow cytometry for surface receptor levels, transferrin endocytosis assay, mediator release assay |
Blood |
Medium |
18698003
|
| 2010 |
The Rabex-5/Rabaptin-5 complex forms a positive feedback loop for Rab5 activation on endosomal membranes: Rabaptin-5 binding to Rab5-GTP recruits the Rabex-5/Rabaptin-5 complex to the membrane, where Rabex-5 generates more Rab5-GTP. This indirect pathway has a delayed onset ('delayed response') requiring above-endogenous levels of Rab5 or Rabex-5 to engage. |
Mathematical modeling, kinetic analysis of Rab5 activation in cells with varying Rabex-5 expression levels, fluorescence assays |
PloS one |
Medium |
20169068
|
| 2012 |
Protein kinase D (PKD) phosphorylates Rabaptin-5 at Ser407, and this phosphorylation is necessary and sufficient for PDGF-dependent short-loop recycling of αvβ3 integrin. Phosphorylated Rabaptin-5 interacts preferentially with Rab4 (not Rab5) near the front of migrating cells to deliver αvβ3 to the leading edge, driving persistent cell migration and invasion, while also inhibiting α5β1 recycling. |
In vitro kinase assay (PKD phosphorylation of Rabaptin-5), phospho-specific antibodies, site-directed mutagenesis (S407A/S407D), co-immunoprecipitation with Rab4/Rab5, integrin recycling assays, 2D migration and invasion assays |
Developmental cell |
High |
22975325
|
| 2012 |
KV10.1 potassium channel physically interacts with Rabaptin-5 and colocalizes on large early endosomes induced by Rab5 hyperactivity. Silencing Rabaptin-5 reduces recycling of KV10.1 to the cell surface and decreases KV10.1 current density in cells natively expressing the channel. |
Co-immunoprecipitation, immunofluorescence colocalization, siRNA knockdown, whole-cell patch-clamp recording |
FEBS letters |
Medium |
22841712
|
| 2013 |
In Drosophila, Rabaptin-5 functions as a neoplastic tumor suppressor; loss-of-function mutants cause epithelial disruption and over-proliferation associated with upregulation of JNK and JAK/STAT signaling, without disruption of apico-basal polarity. Its ability to bind Rab5, modulate early endosomal dynamics, and interact with Rabex-5 is conserved in Drosophila. |
Genetic mosaic analysis in Drosophila (loss-of-function mutations), epistasis with JNK/JAK-STAT pathway reporters, Rab5 binding assays |
Developmental biology |
Medium |
24104056
|
| 2014 |
Rabep1 couples the polycystin complex (PC1/PC2) to a GGA1/Arl3-based ciliary trafficking module at the TGN, enabling ciliary targeting of these large transmembrane proteins. This was identified by yeast two-hybrid screening and validated with a candidate approach. |
Yeast two-hybrid screening, co-immunoprecipitation, candidate interaction validation, knockdown with ciliary localization readout |
Nature communications |
Medium |
25405894
|
| 2014 |
The Rabaptin-5γ isoform, despite its ability to interact with Rab5, is absent from early endosomes and is instead localized to the trans-Golgi network and a Rab4-positive compartment, indicating it functions in membrane transport steps other than Rab5-driven early endosome fusion. |
Immunofluorescence microscopy, subcellular fractionation, Rab5/Rab4 co-localization analysis in transfected cells |
Biochemistry. Biokhimiia |
Low |
25385014
|
| 2014 |
HDAC6 overexpression in gastric cancer inhibits rabaptin-5-mediated early endosome fusion, thereby prolonging EGFR activation and sustaining growth stimulation. HDAC6 knockdown caused inhibition of gastric cancer cell growth associated with decreased EGFR signaling. |
HDAC6 shRNA knockdown, EGFR signaling assays, endosome fusion assays, cell growth assays |
Cancer letters |
Low |
25111897
|
| 2015 |
ITSN2L (Intersectin-2Long) interacts with Rabaptin-5 (RABEP1) via its CC domain binding to the CC3 region of RABEP1. ITSN2L overexpression promotes RABEP1 degradation and represses RABEP1-enhanced endosome aggregation, functioning as a negative regulator of RABEP1 in endocytosis. |
Yeast two-hybrid, GST pulldown, co-immunoprecipitation, colocalization microscopy, overexpression with endosome morphology readout |
International journal of molecular sciences |
Medium |
26633357
|
| 2021 |
HD-PTP (PTPN23) binds directly to Rabaptin-5 between its Rabex-5- and Rab5-binding domains, at the same site that interacts with ESCRT-0/ESCRT-III. HD-PTP depletion leads to Rabaptin-5-dependent hyperactivation of Rab5 and accumulation of hyperphosphorylated Rabaptin-5, blocking cargo exit from Rab5-rich endosomes. This indicates HD-PTP coordinates MVB sorting with endosomal maturation by modulating Rabex-5-Rabaptin-5 activity. |
Co-immunoprecipitation (direct binding), siRNA depletion of HD-PTP, phosphorylation analysis of Rabaptin-5, Rab5-GTP activation assay, ESCRT-III peptide competition binding assay |
Journal of cell science |
Medium |
34657963
|
| 2025 |
RABEP1 is essential for neutrophil motility and chemotaxis. In RABEP1-deficient zebrafish and human dHL-60 cells, endosomal recycling is impaired, PAK phosphorylation (Rac activation readout) is reduced, and leading-edge F-actin polymerization is decreased, without affecting Rab5-GTP levels or chemokine-induced cell polarization. Re-expression of full-length RABEP1, but not a truncation lacking the Rab4/Rab5 binding domain, rescues motility. Dominant-negative Rab4 or Rab5 similarly inhibit neutrophil migration. |
Neutrophil-specific knockout in zebrafish, siRNA knockdown in dHL-60 cells, rescue with domain deletion mutants, dominant-negative Rab4/Rab5 expression, PAK phosphorylation assay, F-actin staining, recycling assays |
Journal of leukocyte biology |
Medium |
40463167 41701563
|