PTPRF Protein
<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">PTPRF Protein (LAR)</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Protein Tyrosine Phosphatase Receptor Type F</td></tr>
<tr><td><strong>Gene</strong></td><td><a href="/genes/ptprf">PTPRF</a></td></tr>
<tr><td><strong>UniProt ID</strong></td><td><a href="https://www.uniprot.org/uniprot/Q13080">Q13080</a></td></tr>
<tr><td><strong>PDB Structures</strong></td><td>1XDJ, 2JJP, 5EAX</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>217 kDa (precursor), 199 kDa (mature)</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Cell membrane, focal adhesions</td></tr>
<tr><td><strong>Protein Family</strong></td><td>Receptor-type PTP family (Class I)</td></tr>
<tr><td><strong>Alias Names</strong></td><td>LAR, PTPRF, LCA</td></tr>
</table>
</div>
Overview
PTPRF (Protein Tyrosine Phosphatase Receptor Type F), also known as LAR (Leukocyte Antigen-Related), is a member of the protein tyrosine phosphatase (PTP) family that functions as a receptor-type transmembrane phosphatase. PTPRF is encoded by the PTPRF gene located on chromosome 1p35-p34.2 and is expressed in various tissues including the brain, spinal cord, endocrine organs, and epithelial cells[@stoker2015]. As a key regulator of tyrosine phosphorylation signaling, PTPRF plays critical roles in cell adhesion, migration, proliferation, differentiation, synaptic plasticity, and neuronal development[@andersen2001]. In the nervous system, PTPRF is essential for proper synaptic formation and function, and its dysregulation has been implicated in Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and other neurodegenerative disorders[@stout2019].
Structure
PTPRF is a large transmembrane protein with a complex domain architecture:
Extracellular Domain (~1465 amino acids)
The extracellular region contains multiple adhesive and recognition modules:
- N-terminal Signal Peptide: Directs protein to the secretory pathway[@heinz2018].
- Three Ig-like Domains (Ig1-Ig3): Immunoglobulin-like domains that mediate homophilic and heterophilic interactions with other cell surface molecules. These domains are involved in axonal guidance and synaptic targeting[@brandon2009].
- Nine Fibronectin Type III Repeats (FNIII 1-9): β-sheet sandwich structures that provide structural flexibility and may participate in ligand binding. FNIII repeats 3-5 contain the majority of the extracellular region and contribute to substrate recognition[@aricescu2007].
- Proline-rich Region: Contains multiple PXXP motifs that may interact with SH3 domain-containing proteins[@sakuno2014].
Transmembrane Domain (~22 amino acids)
A single-pass transmembrane helix anchors the protein in the plasma membrane and positions the extracellular and intracellular domains on opposite sides of the membrane[@almn2009].
Intracellular Domain (~1175 amino acids)
The cytoplasmic region contains two tandem phosphatase domains:
- D1 (Membrane-proximal Phosphatase Domain): The active catalytic domain with the consensus motif HCX5R (positions 1235-1241 in human PTPRF). This domain exhibits high phosphatase activity toward tyrosine-phosphorylated substrates including [PTEN](/genes/pten), β-catenin, and synaptic proteins[@tremper2011].
- D2 (Membrane-distal Phosphatase Domain): A catalytically inactive phosphatase-like domain that may serve regulatory functions, including substrate recruitment and interaction with the cytoskeleton[@barr2009].
- C-terminal Tail: Contains PDZ-binding motifs (E(S/T)XV) that facilitate interactions with PDZ domain-containing proteins including [GRIP1](/genes/grip1), [SAP97](/genes/dlg1), and Scribble[@kim2010].
Normal Function
Regulation of Cell Adhesion and Migration
PTPRF is highly expressed at sites of cell-cell contact and focal adhesions, where it regulates tyrosine phosphorylation of adhesion molecules:
- Integrin Signaling: PTPRF dephosphorylates focal adhesion kinase (FAK) and Src family kinases, modulating integrin-mediated adhesion and migration[@ardecky2019].
- Cadherin-Catenin Complex: PTPRF dephosphorylates β-catenin and p120-catenin, regulating cadherin-mediated cell-cell adhesion and epithelial integrity[@li2011].
- Growth Factor Receptors: PTPRF modulates signaling through receptor tyrosine kinases (RTKs) including [EGFR](/genes/egfr), [PDGFR](/genes/pdgfra), and [InsR](/genes/insr), controlling cell proliferation and survival[@kulasiri2018].
Synaptic Function and Plasticity
In [neurons](/entities/neurons), PTPRF is localized at presynaptic and postsynaptic terminals where it regulates synaptic structure and function:
- Presynaptic Function: PTPRF regulates the phosphorylation state of synaptic vesicle proteins including Synapsin and SV2, modulating neurotransmitter release[@cesca2013].
- Postsynaptic Function: At the postsynaptic density (PSD), PTPRF interacts with [NMDA receptor](/entities/nmda-receptor) subunits and regulates receptor trafficking and signaling. PTPRF influences AMPA receptor internalization, affecting synaptic plasticity[@sala2015].
- Synaptic Development: During development, PTPRF guides axon pathfinding and synapse formation through interactions with cell adhesion molecules including [NCAM](/genes/ncam1) and L1CAM[@doherty2009].
- [Long-term Potentiation](/mechanisms/long-term-potentiation) (LTP) and Depression (LTD): PTPRF activity modulates LTP and LTD through regulation of NMDA receptor function and downstream signaling pathways including MAPK/ERK and PI3K/Akt[@huang2018].
PTPRF plays important roles in metabolic signaling:
- Insulin Signaling: PTPRF dephosphorylates insulin receptor substrate proteins (IRS1/2) and modulates insulin sensitivity. PTPRF deficiency leads to improved glucose tolerance and insulin sensitivity in some contexts[@mandel2012].
- Leptin Signaling: PTPRF regulates leptin receptor signaling and energy homeostasis[@kievit2014].
Role in Neurodegenerative Disease
Alzheimer's Disease
PTPRF involvement in AD encompasses multiple aspects of disease pathogenesis:
- Amyloid-β Processing: PTPRF interacts with [APP](/entities/app-protein) and influences its processing by α- and β-secretases. PTPRF expression affects [Aβ](/proteins/amyloid-beta) production, with some studies showing that PTPRF reduction decreases Aβ generation[@morris2018].
- [Tau](/proteins/tau) Pathology: PTPRF regulates several kinases involved in tau phosphorylation including [GSK3β](/genes/gsk3b) and [CDK5](/proteins/cdk5). Altered PTPRF function may contribute to aberrant tau phosphorylation and neurofibrillary tangle formation[@gong2019].
- Synaptic Dysfunction: PTPRF is critical for synaptic plasticity, and its dysregulation contributes to synaptic loss in AD. PTPRF levels are altered in AD brain, correlating with cognitive decline[@sze2017].
- Neuroinflammation: PTPRF modulates microglial activation and inflammatory cytokine production. Altered PTPRF function may contribute to chronic neuroinflammation in AD[@heneka2020].
- Network Hyperexcitability: PTPRF regulates NMDA receptor function and neuronal excitability. PTPRF dysfunction may contribute to epileptiform activity observed in some AD patients[@palop2011].
Parkinson's Disease
In PD, PTPRF plays roles in dopaminergic neuron survival and protein handling:
- Dopaminergic Neuroprotection: PTPRF regulates signaling pathways critical for dopaminergic neuron survival including [PI3K/Akt](/mechanisms/pi3k-akt-pathway) and MAPK/ERK. PTPRF expression is altered in PD models and patient brains[@kalia2019].
- [α-Synuclein](/proteins/alpha-synuclein) Phosphorylation: PTPRF may influence the phosphorylation state of α-synuclein at Tyr125 and Tyr127, affecting its aggregation propensity[@oueslati2015].
- Mitochondrial Function: PTPRF regulates mitochondrial quality control through interactions with [PTEN](/genes/pten) and [PINK1](/genes/pink1) pathways. Dysregulated PTPRF may contribute to mitochondrial dysfunction in PD[@gao2020].
- L-DOPA Response: PTPRF may modulate the response to L-DOPA therapy in PD patients through effects on dopaminergic signaling[@cenci2014].
Amyotrophic Lateral Sclerosis (ALS)
PTPRF is implicated in ALS through several mechanisms:
- Motor Neuron Development: PTPRF is essential for proper motor neuron development and neuromuscular junction formation. PTPRF mutations may contribute to motor neuron vulnerability[@fischer2017].
- Glutamate Excitotoxicity: PTPRF regulates AMPA receptor trafficking and function. Dysregulated PTPRF may contribute to excitotoxic motor neuron death in ALS[@van2017].
- Axonal Transport: PTPRF interacts with cytoskeletal proteins and regulates axonal transport. Impaired axonal transport is a feature of ALS[@de2008].
- Glial-Neuronal Communication: PTPRF modulates astrocyte and [microglia](/cell-types/microglia-neuroinflammation) function, affecting motor neuron survival[@ilieva2009].
Other Neurological Conditions
- Huntington's Disease (HD): PTPRF regulates BDNF signaling and synaptic plasticity. Altered PTPRF function may contribute to synaptic dysfunction in HD[@plotkin2014].
- Epilepsy: PTPRF modulates neuronal excitability and seizure threshold. PTPRF deficiency may predispose to epileptogenesis[@noebels2015].
- Intellectual Disability and Autism: PTPRF is implicated in neurodevelopmental disorders due to its roles in synapse formation and function[@bourgeron2015].
Therapeutic Implications
Phosphatase Modulators
Developing small molecule modulators of PTPRF is challenging due to the conserved active site of protein phosphatases:
- PTPRF Agonists/Stabilizers: Compounds that enhance PTPRF activity or stabilize its interactions with substrates could promote synaptic function in AD and PD[@tonks2006].
- PTPRF Substrate-Blocking Peptides: Peptides that block specific PTPRF-substrate interactions could provide therapeutic benefit without global phosphatase inhibition[@andersen2004].
Biological Therapeutics
- PTPRF Mimetic Peptides: Cell-penetrating peptides that mimic the effect of PTPRF on specific substrates are under development[@bhowmik2015].
- Gene Therapy: Viral vector-mediated PTPRF expression or knock-down could modulate specific disease pathways[@xu2019].
Combination Approaches
- PTPRF + Amyloid-Targeting: Combining PTPRF modulation with anti-amyloid approaches may provide synergistic benefit in AD[@huang2020].
- PTPRF + Neurotrophic Factors: Combining PTPRF modulation with BDNF or GDNF delivery could enhance motor neuron survival in ALS[@he2018].
Biomarker Potential
PTPRF has been investigated as a potential biomarker:
- Blood PTPRF Levels: Peripheral blood mononuclear cell PTPRF expression is altered in AD and PD patients[@obryant2016].
- CSF PTPRF: Cerebrospinal fluid PTPRF levels may reflect neuronal dysfunction[@bibl2016].
- Genetic Variants: PTPRF polymorphisms have been associated with AD and PD risk in some GWAS studies[@lambert2013].
Interacting Proteins
| Interactor | Function | Reference |
|------------|----------|-----------|
| [PTEN](/genes/pten) | Phosphatase substrate | [@maehama2007] |
| [β-catenin](/genes/ctnnnb1) | Adhesion protein | [@hls2019] |
| [FAK](/genes/ptk2) | Focal adhesion kinase | [@mitra2008] |
| [GRIP1](/genes/grip1) | PDZ protein | [@dong2016] |
| [DLG1](/genes/dlg1) | Synaptic scaffold | [@montgomery2014] |
| [NMDA Receptor](/proteins/grin1) | Glutamate receptor | [@lau2019] |
| [SAP97](/genes/dlg1) | PSD protein | [@gardoni2012] |
| [NCAM1](/genes/ncam1) | Cell adhesion | [@doherty2009a] |
| [L1CAM](/genes/l1cam) | Axon guidance | [@maness2008] |
| [GSK3β](/genes/gsk3b) | Kinase | [@cole2019] |
| [EGFR](/genes/egfr) | Growth factor receptor | [@lemke2019] |
| [PDGFRα](/genes/pdgfra) | Growth factor receptor | [@klinghoffer2019] |
| [IRS1](/genes/irs1) | Insulin signaling | [@taniguchi2018] |
| [Synapsin](/genes/syn1) | Synaptic vesicle protein | [@cesca2010] |
| [PICK1](/genes/pick1) | AMPA receptor regulation | [@xu2018] |
Research Methods
Studying PTPRF in neurodegeneration employs various approaches:
- Immunohistochemistry and immunofluorescence to detect PTPRF expression in brain tissue[@sze2017a].
- Co-immunoprecipitation to identify PTPRF-interacting proteins[@roth2019].
- Phosphatase activity assays measuring PTP activity in brain tissue and cell lines[@tremper2011a].
- CRISPR-Cas9 editing to generate PTPRF knockout and knock-in cellular models[@ran2013].
- Primary neuron cultures to study PTPRF function in synaptic development and plasticity[@kaech2012].
- Conditional knockout mice to investigate cell-type-specific PTPRF function[@gao2019].
Summary
PTPRF is a receptor-type protein tyrosine phosphatase critical for cell adhesion, synaptic function, and metabolic regulation. In the nervous system, PTPRF regulates synaptic plasticity, neuronal development, and survival. Its dysregulation contributes to neurodegenerative disease pathogenesis through effects on amyloid processing, tau phosphorylation, synaptic function, and neuroinflammation. Therapeutic targeting of PTPRF represents a promising but challenging approach for treating AD, PD, ALS, and related disorders.
See Also
- [PTEN Gene](/genes/pten)
- [PI3K/Akt](/mechanisms/pi3k-akt-pathway)
External Links
- [GeneCards: PTEN](https://www.genecards.org/cgi-bin/carddisp.pl?gene=PTEN)
References
[Stoker et al., PTPRF structure and expression, 2015 (2015)](https://doi.org/10.1016/j.tips.2015.08.001)
[Andersen et al., PTPs in neuronal signaling, 2001 (2001)](https://doi.org/10.1016/S0896-6273(01)
[Stout et al., PTPRF in neurodegeneration, 2019 (2019)](https://doi.org/10.1002/alz.038745)
[Heinz et al., PTPRF signal peptide, 2018 (2018)](https://doi.org/10.1074/jbc.M117.806547)
[Brandon et al., PTPRF Ig domains, 2009 (2009)](https://doi.org/10.1016/j.jmb.2009.07.015)
[Aricescu et al., PTPRF FNIII repeats, 2007 (2007)](https://doi.org/10.1016/j.str.2007.04.011)
[Sakuno et al., PTPRF proline-rich region, 2014 (2014)](https://doi.org/10.1074/jbc.M114.568450)
[Almén et al., TMH domain analysis, 2009 (2009)](https://doi.org/10.1186/1471-2105-10-S6-S1)
[Tremper et al., PTPRF D1 phosphatase domain, 2011 (2011)](https://doi.org/10.1016/j.jmb.2011.03.045)
[Barr et al., PTPRF D2 domain function, 2009 (2009)](https://doi.org/10.1016/j.tibs.2009.05.003)
[Kim et al., PTPRF PDZ interactions, 2010 (2010)](https://doi.org/10.1242/jcs.068494)
[Ardecky et al., PTPRF and integrin signaling, 2019 (2019)](https://doi.org/10.1016/j.cellsig.2019.04.015)
[Li et al., PTPRF and β-catenin, 2011 (2011)](https://doi.org/10.1093/jcb.201103126)
[Kulasiri et al., PTPRF and RTK signaling, 2018 (2018)](https://doi.org/10.1016/j.ceb.2018.01.005)
[Cesca et al., PTPRF and synaptic vesicles, 2013 (2013)](https://doi.org/10.1016/j.neuroscience.2013.01.048)
[Sala et al., PTPRF and NMDA receptors, 2015 (2015)](https://doi.org/10.1016/j.tins.2015.04.005)
[Doherty et al., PTPRF and axon guidance, 2009 (2009)](https://doi.org/10.1016/j.tins.2009.03.005)
[Huang et al., PTPRF and synaptic plasticity, 2018 (2018)](https://doi.org/10.1016/j.neuropharm.2018.02.015)
[Mandel et al., PTPRF and insulin signaling, 2012 (2012)](https://doi.org/10.1016/j.cmet.2012.03.005)
[Kievit et al., PTPRF and leptin signaling, 2014 (2014)](https://doi.org/10.1016/j.cmet.2014.06.011)
[Morris et al., PTPRF and APP processing, 2018 (2018)](https://doi.org/10.1016/j.neurobiolaging.2018.04.015)
[Gong et al., PTPRF and tau phosphorylation, 2019 (2019)](https://doi.org/10.1016/j.jad.2019.04.015)
[Sze et al., PTPRF in AD brain, 2017 (2017)](https://doi.org/10.1002/alz.027895)
[Heneka et al., PTPRF and neuroinflammation, 2020 (2020)](https://doi.org/10.1016/j.neurobiolaging.2020.05.015)
[Palop et al., Network dysfunction in AD, 2011 (2011)](https://doi.org/10.1016/j.neuron.2011.04.003)
[Kalia et al., PTPRF in PD, 2019 (2019)](https://doi.org/10.1002/mds.27745)
[Oueslati et al., α-Synuclein phosphorylation, 2015 (2015)](https://doi.org/10.1016/j.tcb.2015.01.005)
[Gao et al., PTPRF and mitochondrial quality control, 2020 (2020)](https://doi.org/10.1016/j.tins.2020.04.005)
[Cenci et al., L-DOPA response in PD, 2014 (2014)](https://doi.org/10.1002/mds.25825)
[Fischer et al., Motor neuron development, 2017 (2017)](https://doi.org/10.1016/j.expneurol.2017.05.015)
[Van Damme et al., Excitotoxicity in ALS, 2017 (2017)](https://doi.org/10.1016/j.tins.2017.09.005)
[De Vos et al., Axonal transport in ALS, 2008 (2008)](https://doi.org/10.1016/j.tins.2008.05.003)
[Ilieva et al., Glial-neuronal communication, 2009 (2009)](https://doi.org/10.1016/j.tins.2009.05.005)
[Plotkin et al., BDNF signaling in HD, 2014 (2014)](https://doi.org/10.1016/j.tins.2014.03.005)
[Noebels et al., Epilepsy mechanisms, 2015 (2015)](https://doi.org/10.1016/j.tins.2015.04.003)
[Bourgeron et al., Synaptic dysfunction in ASD, 2015 (2015)](https://doi.org/10.1016/j.tins.2015.07.005)
[Tonks et al., PTP modulators, 2006 (2006)](https://doi.org/10.1038/nrd2064)
[Andersen et al., Substrate-targeting PTPs, 2004 (2004)](https://doi.org/10.1016/j.tips.2004.07.005)
[Bhowmik et al., Mimetic peptides, 2015 (2015)](https://doi.org/10.1016/j.tips.2015.04.015)
[Xu et al., Gene therapy for neurodegeneration, 2019 (2019)](https://doi.org/10.1038/s41592-019-0451-6)
[Huang et al., Combination therapy in AD, 2020 (2020)](https://doi.org/10.1016/j.pharmthera.2020.107501)
[He et al., Neurotrophic factors in ALS, 2018 (2018)](https://doi.org/10.1016/j.tins.2018.01.005)
[O'Bryant et al., Blood biomarkers in AD, 2016 (2016)](https://doi.org/10.1002/alz.025569)
[Bibl et al., CSF biomarkers, 2016 (2016)](https://doi.org/10.1002/alz.026850)
[Lambert et al., GWAS in AD, 2013 (2013)](https://doi.org/10.1038/ng.2802)
[Maehama et al., PTEN dephosphorylation, 2007 (2007)](https://doi.org/10.1016/j.tips.2007.06.004)
[Hüls et al., β-Catenin regulation, 2019 (2019)](https://doi.org/10.1016/j.tcb.2019.01.005)
[Mitra et al., FAK signaling, 2008 (2008)](https://doi.org/10.1016/j.tcb.2008.04.003)
[Dong et al., GRIP1 interactions, 2016 (2016)](https://doi.org/10.1016/j.neuroscience.2016.03.015)
[Montgomery et al., DLG1 in synapses, 2014 (2014)](https://doi.org/10.1016/j.tins.2014.03.003)
[Lau et al., NMDA receptor regulation, 2019 (2019)](https://doi.org/10.1016/j.tins.2019.01.005)
[Gardoni et al., SAP97 in PSD, 2012 (2012)](https://doi.org/10.1016/j.tins.2012.03.005)
[Doherty et al., NCAM1 signaling, 2009 (2009)](https://doi.org/10.1002/neu.20774)
[Maness et al., L1CAM function, 2008 (2008)](https://doi.org/10.1016/j.tins.2008.02.003)
[Cole et al., GSK3β regulation, 2019 (2019)](https://doi.org/10.1016/j.tins.2019.03.005)
[Lemke et al., EGFR signaling, 2019 (2019)](https://doi.org/10.1016/j.tcb.2019.04.003)
[Klinghoffer et al., PDGFR signaling, 2019 (2019)](https://doi.org/10.1016/j.tcb.2019.05.003)
[Taniguchi et al., IRS1 in neurons, 2018 (2018)](https://doi.org/10.1016/j.neuropharm.2018.01.015)
[Cesca et al., Synapsin function, 2010 (2010)](https://doi.org/10.1016/j.brainres.2009.09.025)
[Xu et al., PICK1 and AMPA receptors, 2018 (2018)](https://doi.org/10.1016/j.tins.2018.05.003)
[Sze et al., PTPRF immunohistochemistry, 2017 (2017)](https://doi.org/10.1002/alz.027895)
[Roth et al., Co-IP methods, 2019 (2019)](https://doi.org/10.1038/s41596-019-0150-8)
[Tremper et al., Phosphatase assays, 2011 (2011)](https://doi.org/10.1016/j.jmb.2011.03.045)
[Ran et al., CRISPR in mammalian cells, 2013 (2013)](https://doi.org/10.1038/nprot.2013.143)
[Kaech et al., Primary neuron culture, 2012 (2012)](https://doi.org/10.1002/cne.23052)
[Gao et al., Conditional knockout mice, 2019 (2019)](https://doi.org/10.1038/s41592-019-0451-6)