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), Parkinson's disease, and related neurological disorders.
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.
| Gene Symbol | RPS6KA2 |
|---|---|
| Full Name | Ribosomal Protein S6 Kinase A2 |
| Alternative Names | p90RSK3, MAPKAP-K3, RSK3 |
| Chromosomal Location | 6q27 |
| NCBI Gene ID | [6146](https://www.ncbi.nlm.nih.gov/gene/6146) |
| OMIM | [604603](https://www.omim.org/entry/604603) |
| Ensembl ID | [ENSG00000071242](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000071242) |
| UniProt | [Q9UOT5](https://www.uniprot.org/uniprot/Q9UOT5) |
| Protein Length | 733 amino acids |
| Protein Kinase Domain | Serine/Threonine protein kinase, RSK family |
| Associated Diseases | Alzheimer's disease, Parkinson's disease, cancer, neurodevelopmental disorders |
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.
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.
RPS6KA2 activation requires:
RPS6KA2 phosphorylates diverse substrates:
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:
Once activated, RPS6KA2 phosphorylates targets affecting:
RPS6KA2 shows the most restricted expression pattern among RSK family members:
Within the central nervous system:
RPS6KA2 is predominantly cytoplasmic but can translocate to:
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.
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.
RPS6KA2 mutations have been associated with:
This suggests critical roles for RPS6KA2 in normal brain development, potentially through its functions in neuronal migration, differentiation, and circuit formation.
| 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 |
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.
Zebrafish have been used to study RPS6KA2 in neuronal development, revealing requirements for proper brain patterning and motor function.
RPS6KA2 variants have been associated with:
RPS6KA2 represents a potential therapeutic target: