Ribosomal Protein L23a
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<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Ribosomal Protein L23a</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Ribosomal Protein L23a</td></tr>
<tr><td><strong>Gene Symbol</strong></td><td>[RPL23A](/genes/rpl23a)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[P62750](https://www.uniprot.org/uniprot/P62750)</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>17.8 kDa</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Cytoplasm (ribosome), Nucleus (extraribosomal)</td></tr>
<tr><td><strong>Protein Family</strong></td><td>Ribosomal Protein L23 Family</td></tr>
<tr><td><strong>Organism</strong></td><td>Homo sapiens</td></tr>
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<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">2 edges</a></td>
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Overview
RPL23A is a highly conserved ribosomal protein that forms part of the 60S large ribosomal subunit in eukaryotes[@dekeersmaecker2015]. Beyond its canonical role in protein synthesis, RPL23A serves critical extraribosomal functions as a regulator of the [p53 tumor suppressor](/entities/p53) pathway and as a sensor of ribosomal stress[@zhang2003]. Disruptions in RPL23A function have been linked to ribosomopathies such as Diamond-Blackfan anemia, and ribosomal stress is increasingly recognized as a contributor to neuronal death in Alzheimer's Disease and Parkinson's Disease[@bulanov2017].
Gene
The [RPL23A gene](/genes/rpl23a) is located on chromosome 17q21 and encodes a 156-amino acid protein. The gene is ubiquitously expressed, with particularly high levels in tissues undergoing active protein synthesis including bone marrow, liver, and brain. RPL23A contains a conserved zinc-finger-like domain that mediates both rRNA binding and extraribosomal protein interactions.
Structure
RPL23A adopts a characteristic ribosomal protein fold[@bulanov2017]:
- Zinc-finger-like domain at the N-terminus (~30 residues): Coordinates a zinc ion through C-X2-C-X18-C-X2-C motif, enabling nucleic acid binding and protein-protein interactions
- Globular core domain: Forms the characteristic ribosomal protein architecture with a beta-barrel structure
- Surface region: Contains binding sites for extraribosomal interactors including MDM2
The protein sits at the surface of the 60S ribosomal subunit, positioned near the polypeptide exit tunnel where it can interact with nascent polypeptides and recruited factors.
Post-Translational Modifications
RPL23A can undergo acetylation and phosphorylation, though the functional significance of these modifications in neurons remains incompletely characterized. Ribosomal proteins are increasingly recognized as targets of post-translational regulation in stress responses.
Normal Function
Role in Translation
As a component of the 60S ribosomal subunit, RPL23A participates in:
- Peptidyl transferase activity: Contributes to the catalytic center that mediates peptide bond formation
- rRNA interaction: Directly contacts 28S rRNA, stabilizing the large subunit structure
- Ribosome assembly: Essential for proper 60S biogenesis; depletion impairs ribosomal subunit joining
- Nascent chain interaction: Positioned near the exit tunnel to interact with newly synthesized polypeptides
A major extraribosomal function of RPL23A is its interaction with MDM2 (Mouse Double Minute 2)[@zhang2003]:
- Under normal conditions, ribosomal proteins including RPL23A bind to MDM2
- This interaction inhibits MDM2's E3 ubiquitin ligase activity toward p53
- When ribosome biogenesis is stressed, free RPL23A accumulates and sequesters MDM2
- MDM2 inhibition stabilizes p53, triggering cell cycle arrest or [apoptosis](/entities/apoptosis)
This pathway connects ribosome status to p53-dependent stress responses, providing a cellular surveillance mechanism for ribosomal integrity.
Ribosomal Stress Response (Integrated Stress Response)
RPL23A levels and localization are modulated during the integrated stress response (ISR):
- Eukaryotic Initiation Factor 2 alpha (eIF2alpha) phosphorylation activates ISR kinases
- ISR activation shifts translation toward stress-responsive genes
- RPL23A redistribution may contribute to altered proteostasis in stressed neurons
Role in Neurodegeneration
Alzheimer's Disease
In Alzheimer's Disease, several mechanisms link RPL23A to disease pathogenesis:
Ribosomal Dysfunction in AD: Post-mortem AD brain tissue shows decreased global translation and ribosomal integrity. RPL23A levels and modification status may be altered in affected neurons, contributing to proteostasis collapse.
p53 and Neuronal Apoptosis: Enhanced p53 activity in AD neurons promotes apoptosis. RPL23A-mediated p53 stabilization could contribute to the elevated neuronal death observed in AD. However, the net effect is complex — p53 activation may also eliminate severely damaged neurons.
Ribosome Quality Control: RPL23A may participate in ribosome-associated quality control (RQC) pathways that monitor translational fidelity. Impaired RQC in AD contributes to proteostasis failure.
Parkinson's Disease
Dopaminergic Neuron Vulnerability: Dopaminergic neurons of the substantia nigra pars compacta show particular sensitivity to ribosomal stress. RPL23A dysregulation could contribute to their selective vulnerability.
Mitochondrial Stress and Translation: PD-linked mitochondrial toxins (e.g., rotenone, MPTP) impair translation. RPL23A may act as a sensor linking mitochondrial dysfunction to p53-mediated apoptosis in affected neurons.
LRRK2 and Translation Regulation: [LRRK2](/genes/lrrk2) mutations (common in familial PD) affect translation homeostasis. RPL23A function may intersect with LRRK2-regulated pathways.
Ribosomopathies and Neurodegeneration
Rare ribosomopathies affecting ribosomal proteins share features with neurodegenerative processes[@dekeersmaecker2015]:
- Diamond-Blackfan anemia (RPL23A mutations): Characterized by red cell aplasia, but some patients show neurological manifestations including learning disabilities and microcephaly
- 5q syndrome: RPS14 haploinsufficiency causes myelodysplastic syndrome with p53 activation
- These disorders establish that ribosomal protein dysfunction can affect the nervous system
Therapeutic Potential
Direct targeting of RPL23A for neurodegeneration therapy remains speculative. However, understanding RPL23A pathways informs several therapeutic approaches:
- p53 modulators: Selective p53 activators that avoid triggering neuronal apoptosis
- ISR kinase inhibitors: ISRIB and similar compounds that restore global translation under stress
- Ribosome biogenesis enhancers: Small molecules that support ribosomal assembly under proteotoxic stress
- Proteostasis supports: Compounds that reduce demand on translation machinery
Interacting Proteins
| Protein | Interaction Type | Functional Significance |
|---------|-----------------|------------------------|
| [MDM2](/entities/mdm2) | Physical binding | Inhibits MDM2 E3 ligase activity, stabilizing p53 |
| 28S rRNA | Structural component | Core ribosomal function |
| [p53](/entities/p53) | Indirect via MDM2 | Stress-responsive cell fate determination |
| eIF2alpha | Functional | Participates in integrated stress response |
Animal Models
- Rpl23a knockout mice: Embryonic lethal, demonstrating essential function
- Rpl23a haploinsufficient mice: Viable but show mild anemia and increased p53 activity
- Zebrafish models: Rpl23a morphants display developmental abnormalities including brain malformation
Key Publications
[De Keersmaecker K et al., Ribosomal mutations in cancer and ribosomopathies (2015)](https://pubmed.ncbi.nlm.nih.gov/26323195/) — Comprehensive review of ribosomal protein mutations in disease
[Zhang Y et al., Ribosomal protein L23 negatively regulates p53 activity (2003)](https://pubmed.ncbi.nlm.nih.gov/12890642/) — Discovery of RPL23A-MDM2-p53 axis
[Bulanova AV et al., RPL23a and its role in ribosome biogenesis (2017)](https://doi.org/10.3390/ijms18050891) — Structural and functional characterizationSee Also
- [RPL23A Gene](/genes/rpl23a)
- [Ribosomal Proteins](/proteins/ribosomal-proteins)
- [p53 Pathway](/entities/p53)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Integrated Stress Response](/entities/integrated-stress-response)
- [Proteostasis](/entities/proteostasis)
- [MDM2](/entities/mdm2)
External Links
- [UniProt P62750](https://www.uniprot.org/uniprot/P62750)
- [NCBI Gene: RPL23A](https://www.ncbi.nlm.nih.gov/gene/6147)
- [PDB: Ribosomal 60S subunit structure](https://www.rcsb.org/)
- [GeneCards: RPL23A](https://www.genecards.org/cgi-bin/carddisp.pl?gene=RPL23A)