RAB39B is a small GTPase protein belonging to the Rab family of vesicle trafficking proteins[@giannandrea2010]. Mutations in the RAB39B gene cause a rare form of autosomal recessive Parkinson's disease characterized by early-onset parkinsonism, intellectual disability, and sometimes autism spectrum disorder[@lesage2015][@wilson2014]. RAB39B plays critical roles in synaptic vesicle trafficking, [autophagy](/entities/autophagy), and mitochondrial function in dopaminergic [neurons](/entities/neurons)[@maciag2020].
RAB39B is a small GTPase protein belonging to the Rab family of vesicle trafficking proteins[@giannandrea2010]. Mutations in the RAB39B gene cause a rare form of autosomal recessive Parkinson's disease characterized by early-onset parkinsonism, intellectual disability, and sometimes autism spectrum disorder[@lesage2015][@wilson2014]. RAB39B plays critical roles in synaptic vesicle trafficking, [autophagy](/entities/autophagy), and mitochondrial function in dopaminergic [neurons](/entities/neurons)[@maciag2020].
Gene and Protein Structure
The RAB39B gene is located on chromosome Xq28 and encodes a 236-amino acid protein with characteristic Rab GTPase domains[@giannandrea2010]. It is highly expressed in the brain, particularly in the substantia nigra, [hippocampus](/brain-regions/hippocampus), and cerebral [cortex](/brain-regions/cortex)[@gautier2016].
Key Structural Features
GTP-binding domain: Essential for vesicular transport function
Hypervariable C-terminal region: Targets protein to specific membrane compartments[@pfeffer2017]
Conserved switch regions: Undergo conformational changes during GTP/GDP cycling
Normal Physiological Functions
Synaptic Vesicle Trafficking
RAB39B regulates synaptic vesicle trafficking and neurotransmitter release through:
Controlling vesicle pool size at presynaptic terminals[@matta2012]
[Giannandrea, M., et al. (2010), RAB39B and X-linked mental retardation (2010)](https://pubmed.ncbi.nlm.nih.gov/20421857/)
[Lesage, S., et al. (2015), Loss-of-function mutations in RAB39B cause an X-linked neurodevelopmental disorder (2015)](https://pubmed.ncbi.nlm.nih.gov/25920567/)
[Wilson, G.R., et al. (2014), Mutations in RAB39B cause X-linked parkinsonism (2014)](https://doi.org/10.1093/brain/awu336)