| PPP1R9B (Spinophilin) | |
|---|---|
| Gene Symbol | PPP1R9B |
| Full Name | Protein Phosphatase 1 Regulatory Subunit 9B |
| Alias | Spinophilin, NSP |
| Chromosome | 17q21.33 |
| NCBI Gene ID | [5770](https://www.ncbi.nlm.nih.gov/gene/5770) |
| OMIM | [604333](https://www.omim.org/entry/604333) |
| Ensembl ID | ENSG00000127314 |
| UniProt ID | [Q9Y2J8](https://www.uniprot.org/uniprot/Q9Y2J8) |
PPP1R9B encodes Spinophilin, a neuronal-specific regulatory subunit of protein phosphatase 1 (PPP1) that plays critical roles in synaptic plasticity, dendritic spine morphology, and receptor signaling. Spinophilin is one of the most abundant proteins in dendritic spines and serves as a critical scaffold that targets PPP1 to postsynaptic sites while simultaneously binding to multiple synaptic proteins.
Spinophilin is named for its localization to dendritic spines—the postsynaptic specializations that receive excitatory synaptic input in neurons. Unlike its close relative DARPP-32 (PPP1R1A), which is enriched in striatal medium spiny neurons, spinophilin is expressed throughout the brain in most excitatory neurons.
Spinophilin serves as a dedicated PPP1 targeting subunit:
Spinophilin functions as a scaffold protein, binding multiple synaptic proteins:
| Partner | Interaction | Functional Consequence |
|---|---|---|
| NMDA receptor (GRIN1/GRIN2B) | Direct binding | Targets PPP1 to NMDA complexes |
| AMPA receptor (GRIA1-4) | Direct binding | Regulates receptor trafficking |
| DARP-32 (PPP1R1A) | Heterodimerization | Coordinates striatal signaling |
| Filamin A (FLNA) | Actin binding | Links to cytoskeleton |
| spinophilin-interacting protein (SPIN1) | Self-association | Regulatory feedback |
Spinophilin Protein Domains:
├── N-terminal F-actin binding domain
├── PPP1-binding RVxF motif (aa 11-14)
├── Multiple PP1-interacting surface sites
├── Coiled-coil dimerization domain
├── C-terminal PDZ-binding motif
Spinophilin is central to activity-dependent synaptic modification:
In striatal medium spiny neurons, spinophilin integrates dopaminergic and glutamatergic signals:
PPP1R9B is expressed primarily in:
Expression is neuron-specific and enriched in excitatory glutamatergic neurons.
Spinophilin dysfunction is strongly implicated in AD pathogenesis:
Spinophilin plays important roles in basal ganglia circuitry:
Spinophilin expression is altered in several conditions:
Recent studies link PPP1R9B mutations to early-onset neurodegeneration[4]:
| Approach | Mechanism | Status |
|---|---|---|
| PPP1 activators | Enhance spinophilin-PPP1 signaling | Preclinical |
| Spine stabilizing compounds | Protect spinophilin expression | Research |
| Gene therapy | Restore spinophilin levels | Early stage |
Small molecules targeting the spinophilin-PPP1 interface are under investigation for:
Yan et al. Spinophilin deficiency protects against amyloid-β toxicity. 2019. ↩︎
Svalbe et al. Spinophilin regulates tau pathology and memory deficits. 2021. ↩︎
Raghavachari & Zahn. Spinophilin in psychiatric disorders. 2008. ↩︎
Barda et al. PPP1R9B mutations associated with early-onset neurodegeneration. 2023. ↩︎