<div class="infobox infobox-gene">
<div class="infobox-header">RAB3D — RAB3D, Member RAS Oncogene Family</div>
<div class="infobox-row"><strong>Gene Symbol:</strong> RAB3D</div>
<div class="infobox-row"><strong>Full Name:</strong> RAB3D, Member RAS Oncogene Family</div>
<div class="infobox-row"><strong>Chromosomal Location:</strong> 19p13.2</div>
<div class="infobox-row"><strong>NCBI Gene ID:</strong> 9547</div>
<div class="infobox-row"><strong>OMIM:</strong> 603677</div>
<div class="infobox-row"><strong>Ensembl ID:</strong> ENSG00000131899</div>
<div class="infobox-row"><strong>UniProt ID:</strong> O95716</div>
<div class="infobox-row"><strong>Protein Length:</strong> 220 amino acids</div>
<div class="infobox-row"><strong>Associated Diseases:</strong> Alzheimer's Disease, Parkinson's Disease, Neurodevelopmental Disorders, Regulated Secretion Defects</div>
</div>
RAB3D encodes a member of the Rab GTPase family that is predominantly expressed in neurons and neuroendocrine cells, where it plays critical roles in regulated secretion and synaptic vesicle trafficking. RAB3D is one of four RAB3 isoforms (RAB3A, RAB3B, RAB3C, RAB3D) that share overlapping but distinct functions in neurotransmitter release and hormonal secretion. Unlike the closely related RAB3A, which is highly enriched in synaptic vesicles, RAB3D shows a broader expression pattern including both neuronal and non-neuronal secretory cells, suggesting specialized functions in different secretion pathways[@schulze2019][@perez2019].
<div class="infobox infobox-gene">
<div class="infobox-header">RAB3D — RAB3D, Member RAS Oncogene Family</div>
<div class="infobox-row"><strong>Gene Symbol:</strong> RAB3D</div>
<div class="infobox-row"><strong>Full Name:</strong> RAB3D, Member RAS Oncogene Family</div>
<div class="infobox-row"><strong>Chromosomal Location:</strong> 19p13.2</div>
<div class="infobox-row"><strong>NCBI Gene ID:</strong> 9547</div>
<div class="infobox-row"><strong>OMIM:</strong> 603677</div>
<div class="infobox-row"><strong>Ensembl ID:</strong> ENSG00000131899</div>
<div class="infobox-row"><strong>UniProt ID:</strong> O95716</div>
<div class="infobox-row"><strong>Protein Length:</strong> 220 amino acids</div>
<div class="infobox-row"><strong>Associated Diseases:</strong> Alzheimer's Disease, Parkinson's Disease, Neurodevelopmental Disorders, Regulated Secretion Defects</div>
</div>
RAB3D encodes a member of the Rab GTPase family that is predominantly expressed in neurons and neuroendocrine cells, where it plays critical roles in regulated secretion and synaptic vesicle trafficking. RAB3D is one of four RAB3 isoforms (RAB3A, RAB3B, RAB3C, RAB3D) that share overlapping but distinct functions in neurotransmitter release and hormonal secretion. Unlike the closely related RAB3A, which is highly enriched in synaptic vesicles, RAB3D shows a broader expression pattern including both neuronal and non-neuronal secretory cells, suggesting specialized functions in different secretion pathways[@schulze2019][@perez2019].
The RAB3 family of small GTPases is essential for regulated secretion, controlling vesicle docking, priming, and fusion at the plasma membrane. RAB3D participates in the final stages of exocytosis, interacting with multiple effectors that coordinate membrane fusion and content release. Dysregulation of RAB3D and other RAB3 isoforms has been implicated in the synaptic dysfunction observed in [Alzheimer's Disease](/diseases/alzheimers-disease) and [Parkinson's Disease](/diseases/parkinsons-disease), where altered neurotransmitter release and impaired vesicle recycling contribute to disease pathogenesis[@martinez2018].
RAB3D was identified as a novel member of the Rab GTPase family through molecular cloning approaches in the early 1990s. The gene is located on chromosome 19p13.2 and encodes a 220 amino acid protein. The RAB3 family includes four isoforms (RAB3A, RAB3B, RAB3C, RAB3D) that arose through gene duplication and have evolved specialized functions. RAB3D is the most recently evolved of the RAB3 isoforms and shows the most restricted expression pattern, with highest levels in specialized secretory cells.
RAB3D shares the canonical Rab GTPase architecture:
| Domain | Position | Function |
|--------|----------|----------|
| Switch I region | 30-50 | Effector binding, conformational change |
| Switch II region | 60-75 | GAP interaction, GTP hydrolysis |
| RabSF motifs | Variable | Family-specific features |
| Hypervariable C-terminus | 180-220 | Prenylation, membrane targeting |
The C-terminal region contains two cysteine residues (Cys210, Cys211) that are modified by geranylgeranylation, a lipid modification that anchors the protein to synaptic vesicle membranes.
RAB3D functions as a molecular switch, cycling between active (GTP-bound) and inactive (GDP-bound) states[@matsuda2018]:
Activation (GTP-bound):
RAB3D controls multiple stages of the synaptic vesicle cycle[@raiders2018][@wang2020]:
In neuroendocrine cells, RAB3D controls[@nishimura2020]:
RAB3D contributes to synaptic plasticity[@gomez2020][@kim2020]:
RAB3D shows region-specific expression in the nervous system:
| Brain Region | Expression Level |
|--------------|-----------------|
| Hippocampus | High |
| Cortex | Moderate-high |
| Cerebellum | Moderate |
| Striatum | Moderate |
| Brainstem | Low-moderate |
RAB3D dysfunction contributes to AD pathogenesis through[@kan2018][@scheff2019]:
Synaptic deficits:
In PD, RAB3D alterations affect[@chen2021][@itoh2019]:
Dopaminergic transmission:
RAB3D is implicated in:
RAB3D interacts with multiple effectors[@tanaka2019]:
| Effector | Function |
|----------|----------|
| Synaptotagmin | Calcium sensor for fusion |
| SNAP-25 | SNARE complex component |
| Munc13 | Vesicle priming factor |
| RIM | Active zone scaffold |
| Rabphilin | Vesicle tethering |
| Granuphilin | Secretory granule regulation |
RAB3D interfaces with the SNARE machinery:
RAB3D intersects with multiple signaling systems:
| Pathway | Interaction |
|---------|-------------|
| Ca²⁺ signaling | Synaptotagmin binding |
| cAMP/PKA | Phosphorylation regulation |
| mTOR | Translation control |
| MAPK | Activity-dependent modulation |
Modulating RAB3D function may provide therapeutic benefits:
Small molecule approaches:
Biomarker potential:
RAB3D mutations are less common than RAB3A:
| Mutation Type | Effect |
|--------------|--------|
| Missense | Altered function |
| Synonymous | May affect splicing |
| Regulatory | Expression changes |
RAB3D shows conservation across species: