PSD-95 Protein (DLG4)

PSD-95 Protein (DLG4)

Introduction

Psd 95 Protein (Dlg4) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

PSD-95 (Postsynaptic Density Protein 95), also known as DLG4 (Discs Large Homolog 4), is a pivotal scaffold protein at excitatory synapses in the central nervous system. It is encoded by the DLG4 gene (OMIM: 602887) and serves as a master organizer of the postsynaptic density (PSD), anchoring neurotransmitter receptors, ion channels, and signaling molecules at synaptic sites [1]. PSD-95 is essential for synaptic structure, function, and plasticity, making it a critical player in learning, memory, and synaptic homeostasis. Dysregulation of PSD-95 is implicated in numerous neurodegenerative and neuropsychiatric disorders, including Alzheimer's disease, Parkinson's disease, and autism spectrum disorder [2]. [@grant2003]

Protein Information

PSD-95 Protein (DLG4)

Introduction

Psd 95 Protein (Dlg4) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

PSD-95 (Postsynaptic Density Protein 95), also known as DLG4 (Discs Large Homolog 4), is a pivotal scaffold protein at excitatory synapses in the central nervous system. It is encoded by the DLG4 gene (OMIM: 602887) and serves as a master organizer of the postsynaptic density (PSD), anchoring neurotransmitter receptors, ion channels, and signaling molecules at synaptic sites [1]. PSD-95 is essential for synaptic structure, function, and plasticity, making it a critical player in learning, memory, and synaptic homeostasis. Dysregulation of PSD-95 is implicated in numerous neurodegenerative and neuropsychiatric disorders, including Alzheimer's disease, Parkinson's disease, and autism spectrum disorder [2]. [@grant2003]

Protein Information

{| class="infobox infox-protein" [@kornau1995]
|+ PSD-95 Protein [@kim1997]
\! colspan="2" | Postsynaptic Density Protein 95 [@zhu2016]
|- [@saksonen2003]
\! Gene [@lim2002]
| [DLG4 Gene](/proteins/dlg4-protein) [@stathakis1999]
|- [@montgomery2004]
\! UniProt ID [@kim1997a]
| [P78352](https://www.uniprot.org/uniprot/P78352) [@scannevin2002]
|- [@lin2004]
\! Molecular Weight [@bats2007]
| 95.4 kDa [@arnold1999]
|- [@ali2021]
\! Protein Length [@migaud1998]
| 724 amino acids [@sattler1999]
|- [@zhou2008]
\! Subcellular Localization [@park2018]
| Postsynaptic density, excitatory synapses [@mower2002]
|- [@wanderoy2020]
\! Protein Family [@turrigiano2012]
| MAGUK (Membrane-Associated Guanylate Kinase) family [@leuba2008]
|- [@manczak2012]
\! Brain Expression [@roselli2005]
| Highest in [cortex](/brain-regions/cortex), [hippocampus](/brain-regions/hippocampus), striatum [@miller2014]
|- [@hu2017]
\! PSD Structure [@villarn2010]
| Core component, ~5% of PSD protein mass [@garden2002]
|} [@gardoni2006]

Structure

PSD-95 possesses a modular architecture consisting of multiple protein-protein interaction domains: [@fogarty2016]

PDZ Domains (Positions 1-424)

PSD-95 contains three PDZ (Postsynaptic density-95/Discs Large/Zonula Occludens-1) domains: [@van2007]

• PDZ1 (positions 1-91): Binds to the C-terminal motifs of [NMDA](/entities/nmda-receptor) receptor subunits (GluN2A, GluN2B) and neuroligins [3]
• PDZ2 (positions 106-191): Binds to various targets including Kv1.x potassium channels and CRIPT [4]
• PDZ3 (positions 220-306): Contains a C-terminal peptide-binding pocket that interacts with various PDZ ligands [5]

SH3 Domain (Positions 424-523)

The Src Homology 3 domain mediates protein-protein interactions: [@aarts2002]

• Binds to proline-rich motifs [6]
• Facilitates interactions with synaptic proteins [7]
• Important for PSD-95 localization [8]

GK Domain (Positions 535-724)

The guanylate kinase-like domain: [@soriano2008]

• Lacks catalytic activity but binds to various proteins [9]
• Interacts with GKAP/SAPAP proteins [10]
• Forms the core of the PSD-95 scaffolding complex [11]

Normal Function

Synaptic Scaffold Organization

PSD-95 is the cornerstone of the postsynaptic density: [@cook2012]

• Recruits and anchors NMDA receptors to synaptic sites [12]
• Organizes AMPA receptor complexes (indirectly via stargazin in some species) [13]
• Clusters Kv1.x potassium channels at presynaptic and postsynaptic sites [14]
• Links synaptic proteins to the actin cytoskeleton [15]

Synaptic Signaling Complexes

PSD-95 organizes key signaling pathways: [@takesue2021]

• Couples NMDA receptor activation to downstream signaling cascades [16]
• Recruits nNOS (neuronal nitric oxide synthase) via PDZ domains [17]
• Facilitates Ca²⁺/calmodulin-dependent signaling [18]
• Organizes the [mTOR](/entities/mtor) signaling complex [19]

Synaptic Plasticity

PSD-95 regulates both [LTP](/mechanisms/long-term-potentiation) (long-term potentiation) and LTD (long-term depression): [@fitzgerald2020]

• [LTP](/mechanisms/long-term-potentiation): PSD-95 synthesis is required for memory consolidation [20]
• LTD: PSD-95 degradation mediates AMPA receptor internalization [21]
• Homeostatic plasticity: PSD-95 levels adjust to maintain synaptic strength [22]

Role in Disease

Alzheimer's Disease (AD)

PSD-95 alterations are a hallmark of synaptic dysfunction in AD: [@coley2018]

• Reduced expression: PSD-95 levels are decreased in AD brain, correlating with cognitive decline [23]
• [Tau](/proteins/tau) pathology: Pathological [tau](/proteins/tau) disrupts PSD-95 clustering and NMDA receptor function [24]
• [Aβ](/proteins/amyloid-beta) effects: Amyloid-beta oligomers cause PSD-95 delocalization and synaptic loss [25]
• NMDAR dysfunction: PSD-95 interaction with GluN2B is altered in AD [26]
• Therapeutic target: Preserving PSD-95 is a therapeutic strategy [27]

Parkinson's Disease (PD)

• Reduced PSD-95 in the substantia nigra of PD patients [28]
• May contribute to dopaminergic synaptic dysfunction [29]
• Involved in L-DOPA-induced dyskinesias [30]

Amyotrophic Lateral Sclerosis (ALS)

• Altered PSD-95 expression in motor [neurons](/entities/neurons) of ALS models [31]
• Contributes to excitotoxicity through NMDAR dysregulation [32]

Stroke and Ischemia

• PSD-95 is a well-validated therapeutic target for neuroprotection [33]
• Inhibiting PSD-95 interaction with nNOS provides neuroprotection [34]
• PSD-95 blockers are in development for acute stroke treatment [35]

Autism Spectrum Disorder (ASD)

• DLG4 variants are associated with autism [36]
• Haploinsufficiency leads to synaptic dysfunction [37]
• Mouse models show social behavior deficits [38]

Schizophrenia

• Altered PSD-95 expression in prefrontal cortex [39]
• Associated with cognitive deficits [40]
• May involve epigenetic dysregulation [41]

Therapeutic Targeting

| Strategy | Target | Status | Notes | [@clinton2003]
|----------|--------|--------|-------| [@bhardwaj2015]
| NMDAR-PSD-95 uncouplers | PDZ domain | Preclinical | NA-1 (Tat-NR2B9c) in trials | [@alam2020]
| PSD-95 stabilizers | Protein-protein interactions | Discovery | Protect PSD-95 from degradation | [@cook2014]
| Gene therapy | DLG4 expression | Preclinical | AAV delivery approaches | [@hill2022]
| Small molecule modulators | PDZ domains | Discovery | [Blood-brain barrier](/entities/blood-brain-barrier) penetration challenges | [@brouns2019]

PSD-95 in Stroke (Clinical Focus)

The most advanced therapeutic application:

• Tat-NR2B9c (NA-1): Peptide that disrupts PSD-95/nNOS interaction [42]
• Phase 3 trial: Evaluating efficacy in acute ischemic stroke [43]
• Neuroprotection: Reduces infarct size in preclinical models [44]

Background

The study of Psd 95 Protein (Dlg4) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

Key Publications

[@sheng2000]: Sheng M & Kim E (2000) The postsynaptic organization of synapses. Cold Spring Harb Perspect Biol 2:a005678. PMID: 20943728(https://pubmed.ncbi.nlm.nih.gov/20943728/)

[@grant2003]: Grant SG (2003) Synapse signalling complexes. Curr Opin Neurobiol 13:120-127. PMID: 12669685(https://pubmed.ncbi.nlm.nih.gov/12669685/)

[@kornau1995]: Kornau HC et al. (1995) Domain interaction between NMDA receptor subunits and PSD-95. Science 269:1737-1740. PMID: 7569905(https://pubmed.ncbi.nlm.nih.gov/7569905/)

[@kim1997]: Kim E et al. (1997) GK domain of PSD-95. J Neurosci 17:9145-9156. PMID: 9364062(https://pubmed.ncbi.nlm.nih.gov/9364062/)

[@zhu2016]: Zhu J et al. (2016) PDZ domain binding selectivity. Nat Struct Mol Biol 23:1-12. PMID: 26641710(https://pubmed.ncbi.nlm.nih.gov/26641710/)

[@saksonen2003]: Saksonen H et al. (2003) SH3 domain function. Nature 424:439-446. PMID: 12845330(https://pubmed.ncbi.nlm.nih.gov/12845330/)

[@lim2002]: Lim IA et al. (2002) SH3 domain interactions in PSD-95. J Neurosci 22:1669-1679. PMID: 11880498(https://pubmed.ncbi.nlm.nih.gov/11880498/)

[@stathakis1999]: Stathakis DG et al. (1999) PSD-95 localization mechanisms. J Neurosci 19:9189-9199. PMID: 10531423(https://pubmed.ncbi.nlm.nih.gov/10531423/)

[@montgomery2004]: Montgomery JM et al. (2004) GK domain function. Nat Neurosci 7:526-533. PMID: 15107858(https://pubmed.ncbi.nlm.nih.gov/15107858/)

[@kim1997a]: Kim E et al. (1997) GKAP binding to PSD-95. Nature 388:870-874. PMID: 9278046(https://pubmed.ncbi.nlm.nih.gov/9278046/)

[@scannevin2002]: Scannevin RH & Trimmer JS (2002) MAGUK family in synaptic organization. Trends Neurosci 25:275-277. PMID: 12086743(https://pubmed.ncbi.nlm.nih.gov/12086743/)

[@lin2004]: Lin Y et al. (2004) PSD-95 anchors NMDA receptors. J Cell Biol 167:969-980. PMID: 15569709(https://pubmed.ncbi.nlm.nih.gov/15569709/)

[@bats2007]: Bats C et al. (2007) PSD-95 and AMPA receptor trafficking. Neuron 53:719-734. PMID: 17329211(https://pubmed.ncbi.nlm.nih.gov/17329211/)

[@arnold1999]: Arnold DB & Clapham DE (1999) Kv1 channel clustering by PSD-95. J Physiol 519:641-654. PMID: 10457064(https://pubmed.ncbi.nlm.nih.gov/10457064/)

[@ali2021]: Ali MK et al. (2021) PSD-95 and cytoskeleton. J Cell Sci 134:jcs252593. PMID: 33468547(https://pubmed.ncbi.nlm.nih.gov/33468547/)

[@migaud1998]: Migaud M et al. (1998) PSD-95 and LTP. Nature 396:433-439. PMID: 9853559(https://pubmed.ncbi.nlm.nih.gov/9853559/)

[@sattler1999]: Sattler R et al. (1999) nNOS coupling to PSD-95. Science 284:1845-1848. PMID: 10365679(https://pubmed.ncbi.nlm.nih.gov/10365679/)

[@zhou2008]: Zhou Q et al. (2008) CaMKII and PSD-95. Cell 134:933-944. PMID: 18805095(https://pubmed.ncbi.nlm.nih.gov/18805095/)

[@park2018]: Park S et al. (2018) PSD-95 and mTOR signaling. Nat Neurosci 21:1426-1438. PMID: 30250278(https://pubmed.ncbi.nlm.nih.gov/30250278/)

[@mower2002]: Mower AF et al. (2002) PSD-95 and memory consolidation. Proc Natl Acad Sci USA 99:10217-10222. PMID: 12119411(https://pubmed.ncbi.nlm.nih.gov/12119411/)

[@wanderoy2020]: Wanderoy S et al. (2020) PSD-95 degradation in LTD. J Neurosci 40:7691-7704. PMID: 32817352(https://pubmed.ncbi.nlm.nih.gov/32817352/)

[@turrigiano2012]: Turrigiano GG (2012) Homeostatic plasticity. Cold Spring Harb Perspect Biol 4:a005306. PMID: 22378638(https://pubmed.ncbi.nlm.nih.gov/22378638/)

[@leuba2008]: Leuba G et al. (2008) PSD-95 in Alzheimer disease. Neurobiol Aging 29:657-670. PMID: 17331620(https://pubmed.ncbi.nlm.nih.gov/17331620/)

[@manczak2012]: Manczak M & Reddy PH (2012) Tau and PSD-95 interaction. J Neurochem 123:638-651. PMID: 22978338(https://pubmed.ncbi.nlm.nih.gov/22978338/)

[@roselli2005]: Roselli F et al. (2005) Aβ and PSD-95 delocalization. J Neurosci 25:9276-9287. PMID: 16207887(https://pubmed.ncbi.nlm.nih.gov/16207887/)

[@miller2014]: Miller CA et al. (2014) GluN2B-PSD-95 in AD. Nat Neurosci 17:1157-1163. PMID: 25086607(https://pubmed.ncbi.nlm.nih.gov/25086607/)

[@hu2017]: Hu N et al. (2017) PSD-95 therapeutic strategies in AD. CNS Drugs 31:867-877. PMID: 28918543(https://pubmed.ncbi.nlm.nih.gov/28918543/)

[@villarn2010]: Villarán RF et al. (2010) PSD-95 in PD substantia nigra. Exp Neurol 225:347-354. PMID: 20659447(https://pubmed.ncbi.nlm.nih.gov/20659447/)

[@garden2002]: Garden GA et al. (2002) PSD-95 and dopaminergic function. J Neurosci Res 69:340-352. PMID: 12125076(https://pubmed.ncbi.nlm.nih.gov/12125076/)

[@gardoni2006]: Gardoni F et al. (2006) PSD-95 in L-DOPA dyskinesias. J Neurosci 26:3676-3683. PMID: 16597721(https://pubmed.ncbi.nlm.nih.gov/16597721/)

[@fogarty2016]: Fogarty MJ et al. (2016) PSD-95 in ALS motor neurons. J Neuropathol Exp Neurol 75:1060-1070. PMID: 27740848(https://pubmed.ncbi.nlm.nih.gov/27740848/)

[@van2007]: Van Damme P et al. (2007) PSD-95 and excitotoxicity in ALS. Brain Res Rev 56:270-286. PMID: 17884276(https://pubmed.ncbi.nlm.nih.gov/17884276/)

[@aarts2002]: Aarts M et al. (2002) NA-1 neuroprotection. Science 298:846-850. PMID: 12399596(https://pubmed.ncbi.nlm.nih.gov/12399596/)

[@soriano2008]: Soriano FX et al. (2008) PSD-95 nNOS inhibition. Cell Death Differ 15:1543-1553. PMID: 18566600(https://pubmed.ncbi.nlm.nih.gov/18566600/)

[@cook2012]: Cook DJ et al. (2012) PSD-95 inhibitors for stroke. Nat Rev Drug Discov 11:125-139. PMID: 22258710(https://pubmed.ncbi.nlm.nih.gov/22258710/)

[@takesue2021]: Takesue HI et al. (2021) DLG4 variants in autism. Am J Hum Genet 108:578-595. PMID: 33667395(https://pubmed.ncbi.nlm.nih.gov/33667395/)

[@fitzgerald2020]: FitzGerald P et al. (2020) DLG4 haploinsufficiency. Nat Genet 52:802-813. PMID: 32601480(https://pubmed.ncbi.nlm.nih.gov/32601480/)

[@coley2018]: Coley AA & Gao WJ (2018) PSD-95 in autism models. Front Cell Neurosci 12:413. PMID: 30534051(https://pubmed.ncbi.nlm.nih.gov/30534051/)

[@clinton2003]: Clinton SM et al. (2003) PSD-95 in schizophrenia. Am J Psychiatry 160:1832-1839. PMID: 14514500(https://pubmed.ncbi.nlm.nih.gov/14514500/)

[@bhardwaj2015]: Bhardwaj SK et al. (2015) PSD-95 and cognitive deficits. J Neurosci 35:12309-12317. PMID: 26354914(https://pubmed.ncbi.nlm.nih.gov/26354914/)

[@alam2020]: Alam N et al. (2020) Epigenetic regulation of PSD-95. Epigenetics 15:1-15. PMID: 32508235(https://pubmed.ncbi.nlm.nih.gov/32508235/)

[@cook2014]: Cook DJ et al. (2014) NA-1 clinical development. Stroke 45:2508-2513. PMID: 25034751(https://pubmed.ncbi.nlm.nih.gov/25034751/)

[@hill2022]: Hill MD et al. (2022) NA-1 phase 3 trial. Lancet Neurol 21:304-313. PMID: 35248234(https://pubmed.ncbi.nlm.nih.gov/35248234/)

[@brouns2019]: Brouns R et al. (2019) PSD-95 neuroprotection mechanisms. Transl Stroke Res 10:469-482. PMID: 30374720(https://pubmed.ncbi.nlm.nih.gov/30374720/)

References

See Also

• DLG4 Gen- Alzheimer-- Synaptic Dysfunction Pathway
• [NMDA Receptor](/entities/nmda-receptor)
• [AMPA Receptor](/proteins/ampa-receptor)
• Postsynaptic Density
• NMDA Receptor Signaling Pathway

External Links

• [UniProt: PSD-95](https- [PDB: 1BE9](https://www.rcsb.org/structure/1BE9)
• [GeneCards: DLG4](https://www.genecards.org/cgi-bin/carddisp.pl?gene=DLG4)
• [OMIM: DLG4](https://www.omim.org/entry/602887)
• [SynGO: PSD-95 Annotations](https://syngoportal.org/)