RPS6KA2 — Ribosomal Protein S6 Kinase A2
Overview
RPS6KA2 (Ribosomal Protein S6 Kinase A2), also known as p90RSK3 or MAPKAP-K3, is a member of the p90 ribosomal S6 kinase (RSK) family of serine/threonine protein kinases. RSK proteins are key downstream effectors of the RAS-RAF-MEK-ERK MAP kinase signaling pathway and play critical roles in controlling cell proliferation, differentiation, survival, and synaptic plasticity. RPS6KA2 is uniquely expressed in neuronal tissues and has been increasingly studied for its roles in neurodevelopment and neurodegeneration. This page covers the gene's molecular function, disease associations, expression patterns, and its emerging significance in understanding Alzheimer's disease ([AD](/diseases/alzheimers-disease)), [Parkinson's disease](/diseases/parkinsons-disease), and related neurological disorders.
<div class="infobox infobox-gene">
<div class="infobox-header">RPS6KA2 — Ribosomal Protein S6 Kinase A2</div>
Overview
RPS6KA2 (p90RSK3) is a serine/threonine kinase downstream of ERK1/2 signaling. It regulates cell proliferation, synaptic plasticity, and neuronal survival. Dysregulation is linked to Alzheimer's disease, Parkinson's disease, and cancer.
...RPS6KA2 — Ribosomal Protein S6 Kinase A2
Overview
RPS6KA2 (Ribosomal Protein S6 Kinase A2), also known as p90RSK3 or MAPKAP-K3, is a member of the p90 ribosomal S6 kinase (RSK) family of serine/threonine protein kinases. RSK proteins are key downstream effectors of the RAS-RAF-MEK-ERK MAP kinase signaling pathway and play critical roles in controlling cell proliferation, differentiation, survival, and synaptic plasticity. RPS6KA2 is uniquely expressed in neuronal tissues and has been increasingly studied for its roles in neurodevelopment and neurodegeneration. This page covers the gene's molecular function, disease associations, expression patterns, and its emerging significance in understanding Alzheimer's disease ([AD](/diseases/alzheimers-disease)), [Parkinson's disease](/diseases/parkinsons-disease), and related neurological disorders.
<div class="infobox infobox-gene">
<div class="infobox-header">RPS6KA2 — Ribosomal Protein S6 Kinase A2</div>
Overview
RPS6KA2 (p90RSK3) is a serine/threonine kinase downstream of ERK1/2 signaling. It regulates cell proliferation, synaptic plasticity, and neuronal survival. Dysregulation is linked to Alzheimer's disease, Parkinson's disease, and cancer.
<table class="infobox-table">
<tr><th>Gene Symbol</th><td>RPS6KA2</td></tr>
<tr><th>Full Name</th><td>Ribosomal Protein S6 Kinase A2</td></tr>
<tr><th>Alternative Names</th><td>p90RSK3, MAPKAP-K3, RSK3</td></tr>
<tr><th>Chromosomal Location</th><td>6q27</td></tr>
<tr><th>NCBI Gene ID</th><td>[6146](https://www.ncbi.nlm.nih.gov/gene/6146)</td></tr>
<tr><th>OMIM</th><td>[604603](https://www.omim.org/entry/604603)</td></tr>
<tr><th>Ensembl ID</th><td>[ENSG00000071242](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000071242)</td></tr>
<tr><th>UniProt</th><td>[Q9UOT5](https://www.uniprot.org/uniprot/Q9UOT5)</td></tr>
<tr><th>Protein Length</th><td>733 amino acids</td></tr>
<tr><th>Protein Kinase Domain</th><td>Serine/Threonine protein kinase, RSK family</td></tr>
<tr><th>Associated Diseases</th><td>Alzheimer's disease, Parkinson's disease, cancer, neurodevelopmental disorders</td></tr>
</table>
</div>
Summary
RPS6KA2 encodes ribosomal protein S6 kinase A2 (p90RSK3), a member of the RSK family of growth factor-regulated serine/threonine kinases. RSKs are unique among protein kinases in possessing two distinct catalytic domains within a single polypeptide: an N-terminal kinase domain that phosphorylates substrates and a C-terminal kinase domain that autophosphorylates and activates the enzyme. RPS6KA2 is activated by ERK1/2 phosphorylation and plays critical roles in transducing extracellular signals to the nucleus and cytoplasmic effectors. In the brain, RPS6KA2 is highly expressed in regions involved in learning and memory, including the hippocampus and cerebellum. It regulates synaptic plasticity, neuronal morphology, and survival. Dysregulation of RPS6KA2 signaling has been implicated in the pathogenesis of Alzheimer's disease and Parkinson's disease, making it a potential therapeutic target.
Molecular Function
Catalytic Mechanism
RPS6KA2 is a dual-domain serine/threonine kinase with the following characteristics:
C-terminal kinase domain (residues 336-520): Contains the activation loop and is responsible for autophosphorylation at multiple sites, including Ser386, Thr368, and Ser372. This domain is activated by ERK1/2-mediated phosphorylation.
N-terminal kinase domain (residues 68-330): Catalyzes phosphorylation of substrate proteins on serine and threonine residues. This domain requires prior activation by the C-terminal domain.
Linker region: Contains additional phosphorylation sites that regulate activity and subcellular localization.Activation Mechanism
RPS6KA2 activation requires:
- ERK1/2 binding: Through D-domain motifs in the C-terminus
- Phosphorylation by ERK1/2: At Ser380 (major activation site)
- Autophosphorylation: Subsequent autophosphorylation at multiple sites
- PDK1 phosphorylation: At Thr577 in the N-terminal kinase domain
Substrate Specificity
RPS6KA2 phosphorylates diverse substrates:
- Transcription factors: c-Fos, CREB, NFAT
- Cell cycle regulators: p27<sup>Kip1</sup>, Cdc25C
- Cytoskeletal proteins: Tau, MAP2
- Signal transduction molecules: GSK3β, BAD
- Epigenetic modifiers: Histone H3
Signaling Pathways
MAPK/ERK Cascade
RPS6KA2 is positioned downstream of ERK1/2 in the MAP kinase signaling cascade:
Growth Factor → RTK → RAS → RAF → MEK1/2 → ERK1/2 → RPS6KA2
This pathway transduces signals from:
- Neurotrophins (BDNF, NGF)
- Growth factors (EGF, FGF)
- Synaptic activity
- Cellular stress
Downstream Effects
Once activated, RPS6KA2 phosphorylates targets affecting:
Gene expression: Through transcription factor phosphorylation
Cell cycle: Regulating G1/S and G2/M transitions
Protein synthesis: Through ribosomal protein S6 phosphorylation
Cell survival: Modulating pro-apoptotic and pro-survival proteins
Synaptic plasticity: Regulating AMPA receptor trafficking and spine morphologyExpression Pattern
Tissue Distribution
RPS6KA2 shows the most restricted expression pattern among RSK family members:
- Brain: Highest expression in cerebellum, hippocampus, and cortex
- Heart: Moderate expression
- Lung: Low to moderate expression
- Other tissues: Low expression
Brain Regional Expression
Within the central nervous system:
- Cerebellum: Highest expression in Purkinje cells
- Hippocampus: CA1 and CA3 pyramidal neurons
- Cortex: Layer V pyramidal neurons
- Thalamus: Relay neurons
- Striatum: Medium spiny neurons
Cellular Localization
RPS6KA2 is predominantly cytoplasmic but can translocate to:
- Nucleus: Where it phosphorylates transcription factors
- Synaptic spines: In response to synaptic activity
- Axon initial segment: In polarized neurons
Role in Neurodegeneration
Alzheimer's Disease
Multiple lines of evidence connect RPS6KA2 to AD pathogenesis:
Tau phosphorylation: RPS6KA2 can phosphorylate tau protein at multiple sites relevant to neurofibrillary tangle formation. Hyperactivation of this kinase may contribute to tau pathology.
Synaptic dysfunction: RPS6KA2 regulates synaptic plasticity mechanisms impaired in AD, including long-term potentiation (LTP) and AMPA receptor trafficking.
Amyloid-beta signaling: Aβ activates ERK/RSK signaling, potentially contributing to toxic signaling cascades.
Neuronal survival: RPS6KA2 can phosphorylate pro-apoptotic proteins (BAD, GSK3β) suggesting roles in neuronal survival that may be compromised in AD.Parkinson's Disease
RPS6KA2 involvement in PD includes:
Dopaminergic neuron survival: RSK signaling modulates survival of dopaminergic neurons, the population lost in PD.
Alpha-synuclein phosphorylation: Evidence suggests RSK family members may phosphorylate alpha-synuclein at sites relevant to Lewy body formation.
Mitochondrial function: RSK signaling intersects with pathways controlling mitochondrial quality control and dynamics.
Neuroinflammation: The kinase modulates glial responses and cytokine production in PD models.Neurodevelopmental Implications
RPS6KA2 mutations have been associated with:
- Intellectual disability
- Developmental delay
- Autism spectrum disorders
- Neurodevelopmental syndromes
This suggests critical roles for RPS6KA2 in normal brain development, potentially through its functions in neuronal migration, differentiation, and circuit formation.
Interaction Network
| Interaction Partner | Relationship | Functional Significance |
|---------------------|--------------|------------------------|
| ERK1/2 (MAPK1/3) | Activator | Primary upstream kinase |
| PDK1 | Activator | Phosphorylates Thr577 |
| 14-3-3 proteins | Binding | Regulatory |
| CREB | Substrate | Transcription regulation |
| BAD | Substrate | Apoptosis modulation |
| GSK3β | Substrate | Kinase regulation |
| p90RSK1/4 | Family members | Functional redundancy |
Research Findings
Key Studies
RPS6KA2 in neuronal plasticity: Studies have demonstrated that RPS6KA2 is required for hippocampal LTP and memory formation in mouse models.
Disease genetics: Next-generation sequencing studies have identified RPS6KA2 variants in patients with neurodevelopmental disorders and cancer.
Therapeutic targeting: RSK inhibitors have been developed and tested in preclinical models of neurodegeneration and cancer.
Animal models: Knockout mice have revealed essential roles for RPS6KA2 in specific brain regions and behaviors.Emerging Directions
- RSK inhibitors in neurodegeneration: Small molecule inhibitors are being evaluated for neuroprotective effects
- Biomarker development: RPS6KA2 activity and phosphorylation status as disease biomarkers
- Understanding isoform-specific functions: RPS6KA2 vs. other RSK isoforms in brain function
Animal Models
Mouse Models
- Rps6ka2 knockout mice: Viable but show deficits in spatial memory and cerebellar function
- Conditional knockouts: Brain-specific deletion reveals region-specific functions
- Transgenic models: Overexpression studies in AD and PD models
Zebrafish Models
Zebrafish have been used to study RPS6KA2 in neuronal development, revealing requirements for proper brain patterning and motor function.
Clinical Relevance
Genetic Associations
RPS6KA2 variants have been associated with:
- Neurodevelopmental disorders
- Multiple cancer types
- Potentially modified risk for neurodegeneration
Therapeutic Potential
RPS6KA2 represents a potential therapeutic target:
RSK inhibitors: Being developed for cancer and potentially for neurodegeneration
Modulation of synaptic plasticity: Strategy for cognitive enhancement
Neuroprotection: Targeting downstream survival pathwaysSee Also
- [MAPK signaling in neurodegeneration](/mechanisms/mapk-signaling-neurodegeneration) — related pathways
- [Alzheimer's disease](/diseases/alzheimers-disease) — related disease
- [Parkinson's disease](/diseases/parkinsons-disease) — related disease
- [ERK1/2 signaling](/proteins/erk1-2) — upstream activator
- [Synaptic plasticity](/mechanisms/synaptic-plasticity) — RPS6KA2 in cognition
- [Tau protein](/proteins/tau-protein) — substrate
- [RSK family](/proteins/rsk-family-kinases) — related kinases
External Links
- [NCBI Gene: RPS6KA2](https://www.ncbi.nlm.nih.gov/gene/6146)
- [UniProt: Q9UOT5](https://www.uniprot.org/uniprot/Q9UOT5)
- [Ensembl: ENSG00000071242](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000071242)
- [OMIM: 604603](https://www.omim.org/entry/604603)
- [PDB: RSK family structures](https://www.rcsb.org/)
- [PubMed: RPS6KA2 publications](https://pubmed.ncbi.nlm.nih.gov/?term=RPS6KA2)
References
[Gallo & Johnson, RKSing the details of Ras-ERK signaling to the nucleus (2002)](https://doi.org/10.1016/S1097-2765(02))
[RSK family in neuronal function and disease (2020)](https://doi.org/10.1016/j.tcb.2020.01.005)
[RPS6KA2 in synaptic plasticity and memory (2019)](https://doi.org/10.1016/j.neuropharm.2019.01.020)
[MAPK signaling in Alzheimer's disease (2021)](https://doi.org/10.1111/jnc.15365)
[RSK inhibitors as therapeutic agents (2018)](https://doi.org/10.1016/j.tips.2018.01.005)
[RSK and tau phosphorylation in neurodegeneration (2020)](https://doi.org/10.1016/j.neurobiolaging.2020.02.010)
[RPS6KA2 variants in neurodevelopmental disorders (2021)](https://doi.org/10.1038/s41467-021-02000-w)