GPR78 (G protein-coupled receptor 78) is a GPCR also known as GPRC5B. It is implicated in neurodevelopment and synaptic function. This page covers the gene's normal function, disease associations, expression patterns, and key research findings relevant to neurodegeneration.
GPR78 (GPRC5B) is a member of the G protein-coupled receptor, class C, group 5, member B. It is primarily expressed in the brain and involved in synaptic transmission and neuronal development[@kroger2011]. Studies have shown GPR78 regulates dendritic spine morphology and synaptic plasticity[@thompson2013].
GPR78 (G protein-coupled receptor 78) is a GPCR also known as GPRC5B. It is implicated in neurodevelopment and synaptic function. This page covers the gene's normal function, disease associations, expression patterns, and key research findings relevant to neurodegeneration.
GPR78 (GPRC5B) is a member of the G protein-coupled receptor, class C, group 5, member B. It is primarily expressed in the brain and involved in synaptic transmission and neuronal development[@kroger2011]. Studies have shown GPR78 regulates dendritic spine morphology and synaptic plasticity[@thompson2013].
Signaling Mechanisms
GPRC5B exhibits distinct signaling properties:
Gα_i/o coupling: Primary G protein coupling inhibits adenylate cyclase
Gβγ signaling: Mediates downstream effectors through βγ subunits
ERK/MAPK pathway: Triggers cell proliferation and differentiation signals
PI3K/Akt pathway: Involved in cell survival and synaptic plasticity
Cellular Functions
Synaptic transmission: Modulates neurotransmitter release at presynaptic terminals
Dendritic spine formation: Regulates spine density and morphology
Neuronal development: Guides axonal growth and circuit formation
Dopaminergic neuron survival: Promotes viability of midbrain dopamine neurons
Protein Interactions
PSD-95: Postsynaptic scaffolding protein
GRIP1: Glutamate receptor interacting protein
RGS proteins: Modulate signaling kinetics
DARP32: Dopamine- and cAMP-regulated phosphoprotein
Disease Associations
Parkinson's Disease: GPR78 has been implicated in dopaminergic neuron survival and may play a role in PD pathogenesis[@klein2015].
Neurodevelopmental Disorders: GPR78 variants have been associated with neurodevelopmental disorders and synaptic dysfunction[@patel2017].
Parkinson's Disease Mechanisms
Dopaminergic protection: GPR78 signaling promotes survival of [substantia nigra](/brain-regions/substantia-nigra) neurons
Mitochondrial function: Modulates mitochondrial dynamics and stress response
Neuroinflammation: Modulates microglial activation states
Genetic Associations
rs769454: Associated with PD risk in genome-wide studies
rs1625727: Linked to age of onset
rs3741483: Modulates expression in brain tissues
Expression
GPR78 is highly expressed in the brain, particularly in the basal ganglia, [hippocampus](/brain-regions/hippocampus), and [cortex](/brain-regions/cortex)[@kim2018]. It is localized to synapses and dendritic processes.
Brain Regions
Basal ganglia: High expression in striatum and substantia nigra
Hippocampus: CA1-CA3 regions and dentate gyrus
Cortex: Layers V-VI pyramidal neurons
Cerebellum: Purkinje cells and granule cells
Hypothalamus: Arcuate nucleus and paraventricular nucleus
Cell Types
Dopaminergic neurons: High expression in VTA and SNc
Pyramidal neurons: Cortical and hippocampal projection neurons
Interneurons: GABAergic local circuit neurons
Astrocytes: Moderate expression in gray matter
Therapeutic Implications
Drug Development
GPR78 represents a potential therapeutic target for: