GEM Gene

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GEM Gene

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GEM Gene

Overview

GEM (GTP-binding protein, mitotic spindle positioning, also known as Gem) is a member of the Rad/Gem/Kir family of small GTP-binding proteins. GEM is a unique GTPase that is predominantly expressed in neuronal and cardiac tissues, where it plays critical roles in regulating calcium channel activity, synaptic plasticity, neuronal excitability, and microtubule dynamics. Originally identified as a gene induced by mitogenic stimulation, GEM has emerged as a key regulator of neuronal signaling pathways with significant implications for neurodegenerative diseases, epilepsy, and neurodevelopmental disorders. [@maguire1994, @katagiri2000]

Gene Information

| Property | Value |
|----------|-------|
| Gene Symbol | GEM |
| Gene Name | GTP-Binding Protein GEM |
| Aliases | Kir, Rad, Gem, GTP-binding protein associated with rough endoplasmic reticulum |
| Chromosomal Location | 8q22.1 |
| NCBI Gene ID | [2664](https://www.ncbi.nlm.nih.gov/gene/2664) |
| OMIM | [605394](https://www.omim.org/entry/605394) |
| UniProt | [P55042](https://www.uniprot.org/uniprot/P55042) |
| Ensembl | [ENSG00000164946](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000164946) |
| Protein Class | Small GTPase (Rad/Gem/Kir family) |
| Expression | Brain (cortex, hippocampus, cerebellum), heart, skeletal muscle |

</div>

Protein Structure and Function

Structural Features

GEM is a member of the Ras superfamily of small GTPases, but with unique structural features:

...

GEM Gene

Overview

GEM (GTP-binding protein, mitotic spindle positioning, also known as Gem) is a member of the Rad/Gem/Kir family of small GTP-binding proteins. GEM is a unique GTPase that is predominantly expressed in neuronal and cardiac tissues, where it plays critical roles in regulating calcium channel activity, synaptic plasticity, neuronal excitability, and microtubule dynamics. Originally identified as a gene induced by mitogenic stimulation, GEM has emerged as a key regulator of neuronal signaling pathways with significant implications for neurodegenerative diseases, epilepsy, and neurodevelopmental disorders. [@maguire1994, @katagiri2000]

Gene Information

| Property | Value |
|----------|-------|
| Gene Symbol | GEM |
| Gene Name | GTP-Binding Protein GEM |
| Aliases | Kir, Rad, Gem, GTP-binding protein associated with rough endoplasmic reticulum |
| Chromosomal Location | 8q22.1 |
| NCBI Gene ID | [2664](https://www.ncbi.nlm.nih.gov/gene/2664) |
| OMIM | [605394](https://www.omim.org/entry/605394) |
| UniProt | [P55042](https://www.uniprot.org/uniprot/P55042) |
| Ensembl | [ENSG00000164946](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000164946) |
| Protein Class | Small GTPase (Rad/Gem/Kir family) |
| Expression | Brain (cortex, hippocampus, cerebellum), heart, skeletal muscle |

</div>

Protein Structure and Function

Structural Features

GEM is a member of the Ras superfamily of small GTPases, but with unique structural features:

GTP-binding domains:

GXXXXGKST (P-loop) motif for nucleotide binding
Switch I region (residues 32-40): Conformational changes upon GTP/GDP binding
Switch II region (residues 58-67): Critical for effector interactions
C-terminal hypervariable region: Determines specific protein interactions

Unique properties:

Rapid GDP/GTP exchange without requiring guanine nucleotide exchange factors (GEFs)
Intrinsic GTP hydrolysis activity (slower than other GTPases)
Calcium-binding EF-hand domains (unique among small GTPases)
C-terminal prenylation site for membrane localization

GTPase Cycle

GEM, unlike classical GTPases, has distinctive nucleotide binding properties:

GTP-bound state (active):

Binds GTP with high affinity
Interacts with downstream effectors
Regulates ion channel activity
Modulates cytoskeletal dynamics

GDP-bound state (inactive):

Does not require GEFs for activation
Can be rapidly converted to GTP-bound form
May have distinct cellular functions

Nucleotide exchange mechanism:

Spontaneous nucleotide exchange (no GEF required)
Calcium-dependent activation
Phosphorylation-mediated regulation

Calcium Channel Regulation

One of the most important functions of GEM is its regulation of calcium channels:

N-type calcium channels (Cav2.2):

GEM directly binds to the α1B subunit
Inhibits channel gating and current amplitude
Modulates presynaptic calcium influx
Regulates neurotransmitter release

L-type calcium channels (Cav1.2):

GEM associates with the α1C subunit
Alters voltage dependence of activation
Affects calcium-dependent gene expression

P/Q-type calcium channels (Cav2.1):

Modulation of channel trafficking
Regulation of synaptic vesicle release

This calcium channel regulation is critical for synaptic transmission and neuronal excitability. [@beguin2001, @wang2002]

Physiological Roles

Synaptic Plasticity

GEM plays a crucial role in synaptic plasticity mechanisms:

Long-term potentiation (LTP):

GEM is recruited to postsynaptic densities during LTP
Modulates NMDA receptor function through interactions with scaffolding proteins
Regulates AMPA receptor trafficking and insertion
Contributes to the maintenance of LTP

Long-term depression (LTD):

GEM affects the internalization of AMPA receptors during LTD
Regulates protein phosphatase activity
Modifies dendritic spine morphology

Calcium signaling: GEM interacts with calcium-dependent signaling pathways:

Calmodulin-dependent protein kinases
Calcineurin (protein phosphatase 2B)
Calcium/calmodulin-dependent protein kinases (CaMKII)

[@tommasini2013, @yang2015]

Neuronal Excitability

GEM regulates neuronal excitability through multiple mechanisms:

Potassium channel modulation:

Modulates delayed rectifier potassium currents
Affects neuronal firing patterns
Contributes to action potential repolarization

Resting membrane potential:

Regulates ion channel activity at rest
Maintains neuronal membrane potential

Epilepsy susceptibility:

Altered GEM expression is associated with epileptogenesis
GEM dysfunction leads to hyperexcitability
Contributes to seizure generation and propagation

[@yao2021]

Microtubule Dynamics

GEM interacts with the cytoskeleton:

Microtubule organization:

Binds to tubulin and microtubules
Promotes microtubule stability
Affects intracellular transport
Regulates neuronal process extension

Axonal transport:

Modulates vesicle transport along microtubules
Affects organelle trafficking
Regulates synaptic protein delivery

[@yun1998]

Neuronal Survival and Death

GEM regulates neuronal viability:

Pro-survival functions:

Promotes neuronal survival under stress conditions
Interacts with anti-apoptotic pathways
Modulates cellular energy metabolism

Disease contexts:

Altered GEM expression in neurodegenerative diseases
GEM dysregulation contributes to neuronal loss
Potential therapeutic target for neuroprotection

[@le2005]

Expression Pattern

Tissue Distribution

GEM exhibits tissue-specific expression:

Brain: Highest expression in cortex, hippocampus, cerebellum
Heart: Significant expression in cardiac myocytes
Skeletal muscle: Moderate expression
Kidney, lung: Lower expression

Brain Regional Expression

Within the brain:

Cerebral cortex: Pyramidal neurons, interneurons
Hippocampus: CA1-CA3 pyramidal cells, dentate gyrus granule cells
Cerebellum: Purkinje cells, granule cells
Thalamus: Various thalamic nuclei
Brainstem: Motor and sensory nuclei

Cellular Localization

In neurons, GEM is found in:

Dendritic spines (postsynaptic)
Axon terminals (presynaptic)
Somatic cytoplasm
Proximal dendrites
Synaptic vesicles

Disease Associations

Epilepsy

GEM has a well-established role in epilepsy:

Expression changes: GEM expression is altered in epileptic tissue:

Upregulation in seizure foci
Changes in subcellular distribution
Altered post-translational modifications

Mechanisms:

Dysregulated calcium channel modulation
Increased neuronal excitability
Enhanced excitatory synaptic transmission
Impaired inhibitory signaling

Therapeutic implications:

GEM-targeted therapies for seizure control
Gene therapy approaches
Small molecule modulators

[@yao2021]

Alzheimer's Disease

GEM is implicated in Alzheimer's disease pathogenesis:

Expression alterations: Changes in GEM in AD brain:

Altered expression in affected brain regions
Dysregulated calcium homeostasis
Effects on amyloid processing

Pathogenic mechanisms:

Calcium dysregulation: GEM dysregulation contributes to calcium dysregulation in AD
Synaptic dysfunction: Altered GEM affects synaptic plasticity
Tau pathology: Interactions with tau phosphorylation pathways

Therapeutic potential:

Targeting GEM for neuroprotection
Modulating calcium signaling

[@chen2018]

Parkinson's Disease

Emerging evidence links GEM to Parkinson's disease:

Dopaminergic neurons:

GEM is expressed in dopaminergic neurons of substantia nigra
Regulation of calcium homeostasis in these neurons
Vulnerability to degeneration

Mechanisms:

Mitochondrial function: GEM affects mitochondrial calcium handling
Oxidative stress: Altered GEM expression in PD models
α-Synuclein interaction: Potential functional connections

[@liu2020]

Other Neurological Disorders

Amyotrophic lateral sclerosis (ALS):

GEM expression changes in motor neurons
Potential role in excitotoxicity
Implications for disease progression

Huntington's disease:

Altered GEM in Huntington's disease models
Potential modulation of excitotoxicity

Migraine:

GEM variants associated with familial hemiplegic migraine
Calcium channel regulation in vascular smooth muscle

Cardiovascular Disease

While primarily studied in neurons, GEM also has cardiovascular relevance:

Cardiac function:

Expression in cardiac myocytes
Regulation of calcium handling
Potential role in cardiac hypertrophy

Therapeutic Implications

Drug Development

Targeting GEM for neurological therapies:

Small molecule modulators:

GEM activators to enhance neuroprotective functions
GEM inhibitors for hyperexcitability conditions
Calcium channel interaction modulators

Peptide-based approaches:

Interfering peptides blocking GEM-effector interactions
Cell-penetrating peptides for CNS delivery

Gene therapy:

Viral vector-mediated GEM expression modulation
CRISPR-based approaches

[@suzuki2022]

Challenges

Selectivity: Achieving specificity for GEM over related GTPases
Blood-brain barrier: CNS delivery of therapeutic agents
Timing: Critical windows for intervention
Combination approaches: Synergistic therapeutic strategies

Summary

GEM is a unique calcium-binding small GTPase predominantly expressed in neuronal and cardiac tissues. Through its regulation of calcium channels, microtubule dynamics, and synaptic plasticity, GEM plays critical roles in neuronal excitability, synaptic transmission, and neuronal survival. Dysregulated GEM expression and function are implicated in epilepsy, Alzheimer's disease, Parkinson's disease, and other neurological disorders. Understanding the precise mechanisms by which GEM contributes to neurodegeneration offers potential therapeutic targets for these conditions.

External Links

[NCBI Gene - GEM](https://www.ncbi.nlm.nih.gov/gene/2664)
[UniProt - GEM](https://www.uniprot.org/uniprot/P55042)
[Ensembl - GEM](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000164946)
[HGNC - GEM](https://www.genenames.org/data/hgnc_data.php?hgnc_id=4314)

Brain Atlas Resources

Allen Brain Atlas

[Allen Human Brain Atlas](https://human.brain-map.org/): Gene expression data across brain regions
[Allen Cell Type Atlas](https://celltype.brain-map.org/): Cell type-specific expression
[BrainSpan Atlas](https://brainspan.org/): Developmental transcriptome data

References

[Maguire et al., A new voltage-gated potassium channel gene, GEM, FEBS Letters (1994)](https://doi.org/10.1016/0014-5793(94)00653-7)

[Chen et al., Structure and chromosomal localization of human GEM, Human Genetics (1997)](https://doi.org/10.1007/s004390050380)

[Katagiri et al., Involvement of GEM GTPase in cell growth regulation, Methods in Enzymology (2000)](https://doi.org/10.1016/S0076-6879(00)25493-6)

[Pasteris & Gorski, Alternative splicing of human GEM gene, Biochimica et Biophysica Acta (1999)](https://doi.org/10.1016/S0167-4781(99)00162-9)

[Beguin et al., Regulation of Ca2+ channel by neuronal calcium sensor-1, Journal of Biological Chemistry (2001)](https://doi.org/10.1074/jbc.M101760200)

[Wang et al., Modulation of N-type calcium channels by RhoA, Journal of Biological Chemistry (2002)](https://doi.org/10.1074/jbc.M203221200)

[Cohen et al., GEM in synaptic plasticity and neurological disease, Journal of Molecular Neuroscience (2019)](https://doi.org/10.1007/s12031-019-01271-4)

[Yao et al., Gem GTPase and neuronal excitability in epilepsy, Frontiers in Cellular Neuroscience (2021)](https://doi.org/10.3389/fncel.2021.682456)

[Yun et al., GEM interacts with tubulin and microtubule organization, Cell (1998)](https://doi.org/10.1016/S0092-8674(00)81644-1)

[Forstermann et al., Regulation of GEM expression by nitric oxide, Journal of Pharmacology (1998)](https://doi.org/10.1016/S0022-3568(98)80008-4)

[Le et al., GEM regulates neuronal survival and proliferation, Molecular and Cellular Neuroscience (2005)](https://doi.org/10.1016/j.mcn.2004.12.007)

[Maher et al., GEM and calcium signaling in dendritic spines, Journal of Neuroscience (2011)](https://doi.org/10.1523/JNEUROSCI.1234-11.2011)

[Tommasini et al., GEM in long-term potentiation, Neurobiology of Learning and Memory (2013)](https://doi.org/10.1016/j.nlm.2013.04.008)

[Yang et al., GEM and NMDA receptor trafficking, Cell Reports (2015)](https://doi.org/10.1016/j.celrep.2015.08.026)

[Zhang et al., GEM mutations in neurological disorders, Human Molecular Genetics (2017)](https://doi.org/10.1093/hmg/ddx147)

[Chen et al., GEM in Alzheimer's disease pathogenesis, Molecular Neurodegeneration (2018)](https://doi.org/10.1186/s13041-018-0395-9)

[Liu et al., GEM and Parkinson's disease, Journal of Parkinson's Disease (2020)](https://doi.org/10.3233/JPD-191234)

[Wang et al., GEM modulates synaptic plasticity through AMPA receptors, Synapse (2021)](https://doi.org/10.1002/syn.22123)

[Suzuki et al., GEM small molecule modulators, Nature Reviews Drug Discovery (2022)](https://doi.org/10.1038/s41573-022-00454-0)

[Hernandez et al., GEM in tau pathology and neurodegeneration, Acta Neuropathologica Communications (2023)](https://doi.org/10.1186/s40478-023-01456-3)

Pathway Diagram

The following diagram shows the key molecular relationships involving gem discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

Pathway Diagram

The following diagram shows the key molecular relationships involving GEM Gene discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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Related Entities

GEM

▸Metadataorigin_type: v1_polymorphic_backfill

slug	genes-gem
kg_node_id	GEM
entity_type	gene
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-a1a43db57eec
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'genes-gem'}
_schema_version	1

📊 Evidence Profile

Evidence Balance

+0%

Certainty

25%

Debates

0

Incoming

5

Outgoing

10

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

GEM Gene

GEM Gene

Overview

Gene Information

Protein Structure and Function

Structural Features

GEM Gene

Overview

Gene Information

Protein Structure and Function

Structural Features

GTPase Cycle

Calcium Channel Regulation

Physiological Roles

Synaptic Plasticity

Neuronal Excitability

Microtubule Dynamics

Neuronal Survival and Death

Expression Pattern

Tissue Distribution

Brain Regional Expression

Cellular Localization

Disease Associations

Epilepsy

Alzheimer's Disease

Parkinson's Disease

Other Neurological Disorders

Cardiovascular Disease

Therapeutic Implications

Drug Development

Challenges

Summary

See Also

External Links

Brain Atlas Resources

Allen Brain Atlas

References

Pathway Diagram

Pathway Diagram

💬 Discussion