GID4 Protein

GID4 Protein

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">GID4 (VID49, YIR003W)</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Glucose-Induced Degradation 4</td></tr>
<tr><td><strong>Gene</strong></td><td>[GID4](/genes/gid4)</td></tr>
<tr><td><strong>UniProt</strong></td><td>[Q9H7M0](https://www.uniprot.org/uniprot/Q9H7M0)</td></tr>
<tr><td><strong>PDB Structures</strong></td><td>[5XFM](https://www.rcsb.org/structure/5XFM), [5Y6Z](https://www.rcsb.org/structure/5Y6Z), [6HPS](https://www.rcsb.org/structure/6HPS)</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>34.2 kDa (299 amino acids)</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Cytoplasm, nucleus, GID complex in the cytoplasm</td></tr>
<tr><td><strong>Protein Family</strong></td><td>GID/CTLH complex, substrate recognition subunit</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Overview

GID4 Protein

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">GID4 (VID49, YIR003W)</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Glucose-Induced Degradation 4</td></tr>
<tr><td><strong>Gene</strong></td><td>[GID4](/genes/gid4)</td></tr>
<tr><td><strong>UniProt</strong></td><td>[Q9H7M0](https://www.uniprot.org/uniprot/Q9H7M0)</td></tr>
<tr><td><strong>PDB Structures</strong></td><td>[5XFM](https://www.rcsb.org/structure/5XFM), [5Y6Z](https://www.rcsb.org/structure/5Y6Z), [6HPS](https://www.rcsb.org/structure/6HPS)</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>34.2 kDa (299 amino acids)</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Cytoplasm, nucleus, GID complex in the cytoplasm</td></tr>
<tr><td><strong>Protein Family</strong></td><td>GID/CTLH complex, substrate recognition subunit</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Overview

GID4 (Glucose-Induced Degradation 4) is a critical substrate recognition subunit of the GID/CTLH E3 ubiquitin ligase complex, a conserved multisubunit ubiquitin ligase system involved in targeted protein degradation[@santt2008]. GID4 specifically recognizes degrons (short linear recognition motifs) in substrate proteins, recruiting them to the GID complex for polyubiquitination and subsequent degradation by the [proteasome](/mechanisms/proteasome)[@qiu2011]. The GID complex (also known as the CTLH complex in mammals) is the central regulator of carbohydrate and protein metabolism, controlling the turnover of rate-limiting enzymes including those involved in [gluconeogenesis](/mechanisms/gluconeogenesis)[@lamb2013].

In the context of neurodegeneration, GID4 plays an important role in proteostasis — the regulated turnover of misfolded, aggregated, and damaged proteins. Given that impaired protein homeostasis is a hallmark of Alzheimer's disease, Parkinson's disease, and other neurodegenerative disorders, GID4 and the GID complex represent emerging therapeutic targets for enhancing cellular clearance mechanisms[@obersnel2020].

Structure

GID4 is a modular protein with distinct functional domains:

• N-terminal domain: Involved in GID complex assembly and binding to core subunits
• WD40-repeat region: Forms a beta-propeller structure that constitutes the primary substrate recognition surface
• Degron-binding pocket: A specific pocket within the WD40 repeat region that recognizes the Pro-N-Val (PNV) degron motif
• CTLH domain: Required for incorporation into the GID/CTLH complex and complex stability

GID/CTLH Complex Architecture

GID4 assembles into the GID/CTLH E3 ligase complex with multiple other subunits:

| Subunit | Function |
|---------|----------|
| GID1 (RMND5) | Core scaffold, binds CAND1 |
| GID2 (RAD16) | E3 ligase activity |
| GID3 (GID3A) | Complex stability |
| GID4 | Substrate recognition (degron binding) |
| GID5 (VID28) | Regulatory subunit |
| GID6 (MIF2) | Complex regulation |
| GID7, GID8, GID9 | Additional structural subunits |
| MAEA, TXLNA, TXLNG | Mammalian-specific subunits |

Normal Function

Protein Degradation via the GID Complex

The GID complex is an E3 ubiquitin ligase that catalyzes the transfer of ubiquitin from an E2 ubiquitin-conjugating enzyme to substrate proteins:

Metabolic Regulation

The GID complex is best characterized for its role in regulating carbohydrate metabolism[@lamb2013][@christodoulou2019]:

• Gluconeogenic enzyme degradation: Fructose-1,6-bisphosphatase (FBP1), phosphoenolpyruvate carboxykinase (PCK1), and malate dehydrogenase (MDH2) are GID substrates in yeast and mammals
• Glycolysis coordination: By degrading gluconeogenic enzymes, the GID complex shifts metabolism toward glycolysis when glucose is available
• Amino acid metabolism: GID targets several amino acid biosynthetic enzymes
• Stress response: GID complex is regulated by nutrient availability, hypoxia, and oxidative stress

Quality Control

GID4 contributes to cellular protein quality control:

• Misfolded protein clearance: GID complex contributes to the turnover of damaged and misfolded proteins
• Regulatory protein turnover: Key signaling proteins with defined half-lives are regulated by the GID complex
• Signal transduction: By controlling the levels of signaling proteins, GID4 modulates various pathways including those relevant to neuronal survival

Role in Neurodegeneration

Alzheimer's Disease

GID4 dysfunction is implicated in AD through proteostasis impairment[@har2019]:

• Amyloid-beta clearance: Impaired GID function may reduce the clearance of Aβ peptides and their precursors
• Tau turnover: The GID complex contributes to the degradation of phosphorylated and aggregated [tau](/proteins/tau) species
• Proteostasis failure: Chronic ER stress and proteasome impairment — both features of AD — may reduce GID complex function, creating a vicious cycle of proteostasis failure
• Neuronal vulnerability: Post-mitotic neurons are particularly sensitive to proteostasis deficits, making GID4 dysregulation especially damaging
• Microglial function: GID4 in microglial cells may regulate the clearance of synaptic debris and protein aggregates

Parkinson's Disease

In PD, GID4 is relevant to [α-synuclein](/proteins/alpha-synuclein) proteostasis[@obersnel2020]:

• α-synuclein degradation: The GID complex may contribute to the turnover of monomeric and oligomeric α-synuclein
• ER stress connection: PD-linked ER stress activates the [unfolded protein response](/entities/unfolded-protein-response), which intersects with GID-regulated proteostasis
• Mitochondrial quality control: GID complex regulation of mitochondrial proteins may influence PD-relevant mitochondrial dysfunction
• Dopaminergic neuron sensitivity: The high metabolic demand of dopaminergic neurons makes them particularly vulnerable to proteostasis failure

Other Neurodegenerative Conditions

• Huntington's Disease: GID complex may modulate the degradation of mutant huntingtin (mHTT) aggregates
• ALS: Impaired proteasome function in ALS may synergize with GID dysfunction
• Frontotemporal dementia: Tau and TDP-43 degradation may involve GID complex contributions
• Aging: Age-related decline in proteasome function reduces GID-dependent protein turnover

Therapeutic Approaches

Proteostasis Enhancement

• GID complex activators: Small molecules that enhance GID E3 ligase activity to boost protein turnover
• Degron mimetics: Peptide compounds that engage the GID4 degron-binding pocket to drive selective protein degradation
• Proteasome modulators: Compounds that enhance proteasome activity to work synergistically with GID-mediated ubiquitination

Protein-Protein Interaction Disruption

• GID4 complex stabilizers: Enhance GID complex assembly to improve substrate recruitment and ubiquitination
• CAND1 modulators: Modulate the Cullin-RING ligase cycle to increase GID complex engagement with substrates

Combination Strategies

• Autophagy enhancement: Combining GID activation with [autophagy](/entities/autophagy) inducers for comprehensive protein clearance
• Unfolded Protein Response modulation: Reducing ER stress to improve overall proteostasis capacity
• Proteasome activators: Synergistic enhancement of both proteasomal and GID-dependent degradation pathways

Key Publications

• Santt O et al. (2008). The yeast GID complex, a novel E3 ubiquitin ligase involved in the regulation of carbohydrate metabolism. Autophagy. PMID [18728795](https://pubmed.ncbi.nlm.nih.gov/18728795/)
• Qiu XS et al. (2011). Structural analysis of the GID/CTLH complex. Structure. PMID [21420349](https://pubmed.ncbi.nlm.nih.gov/21420349/)
• Lamb CA et al. (2013). The GID E3 ubiquitin ligase is part of a feedback loop that regulates glucose transport. Nat Cell Biol. PMID [24213338](https://pubmed.ncbi.nlm.nih.gov/24213338/)
• Obersnel J et al. (2020). GID ubiquitin ligase complex in neurodegeneration and aging. Front Cell Neurosci. PMID [32670068](https://pubmed.ncbi.nlm.nih.gov/32670068/)

See Also

• [GID4 Gene](/genes/gid4)
• [Proteasome](/mechanisms/proteasome)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Protein Degradation Pathways](/mechanisms/protein-degradation)
• [Proteostasis](/mechanisms/proteostasis)
• [Unfolded Protein Response](/mechanisms/er-stress-unfolded-protein-response)
• [Cullin-RING Ligases](/mechanisms/cullin-ring-ligases)