RPS6KA2 — Ribosomal Protein S6 Kinase A2

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:

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^Kip1, 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:

Expression 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:

Parkinson's Disease

RPS6KA2 involvement in PD includes:

Neurodevelopmental Implications

RPS6KA2 mutations have been associated with:

• Intellectual disability
• Developmental delay
• Autism spectrum disorders
• Neurodevelopmental syndromes

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

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:

See 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