SQSTM1/p62 Protein

SQSTM1/p62 Protein

Overview

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">SQSTM1/p62 Protein</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>SQSTM1</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>SQSTM1/p62</td>
</tr>
<tr>
<td class="label">Type</td>
<td>Protein</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/?query=SQSTM1" target="_blank">Search UniProt</a></td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/ad" style="color:#ef9a9a">AD</a>, <a href="/wiki/adh" style="color:#ef9a9a">ADH</a>, <a href="/wiki/ali" style="color:#ef9a9a">ALI</a>, <a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">ALZHEIMER</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">2520 edges</a></td>
</tr>
</table>

SQSTM1 (sequestosome-1), commonly called p62, is a multifunctional scaffold protein that couples ubiquitin tagging, autophagosome recruitment, and stress-response signaling.[@pankiv2007][@itakura2011] In neurodegeneration biology, p62 is best interpreted as a flux integrator: it accumulates when degradative systems fail, but it is also required for selective cargo capture and clearance when those systems work.[@itakura2011][@komatsu2007] This dual role explains why p62 can appear protective in early stress adaptation yet still mark disease progression in advanced proteinopathy.

SQSTM1/p62 Protein

Overview

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">SQSTM1/p62 Protein</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>SQSTM1</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>SQSTM1/p62</td>
</tr>
<tr>
<td class="label">Type</td>
<td>Protein</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/?query=SQSTM1" target="_blank">Search UniProt</a></td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/ad" style="color:#ef9a9a">AD</a>, <a href="/wiki/adh" style="color:#ef9a9a">ADH</a>, <a href="/wiki/ali" style="color:#ef9a9a">ALI</a>, <a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">ALZHEIMER</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">2520 edges</a></td>
</tr>
</table>

SQSTM1 (sequestosome-1), commonly called p62, is a multifunctional scaffold protein that couples ubiquitin tagging, autophagosome recruitment, and stress-response signaling.[@pankiv2007][@itakura2011] In neurodegeneration biology, p62 is best interpreted as a flux integrator: it accumulates when degradative systems fail, but it is also required for selective cargo capture and clearance when those systems work.[@itakura2011][@komatsu2007] This dual role explains why p62 can appear protective in early stress adaptation yet still mark disease progression in advanced proteinopathy.

In [neurons](/entities/neurons) and glia, p62 participates in proteostasis triage across protein aggregation, oxidative stress, and inflammatory signaling axes.[@ichimura2013][@jain2010] Mechanistically, it intersects with pathways central to amyotrophic lateral sclerosis (ALS), frontotemporal degeneration (FTD), tauopathies, and related disorders where [autophagy](/entities/autophagy)-lysosome throughput is rate-limiting.[@menzies2015][@son2018]

Domain Architecture And Functional Consequences

SQSTM1 is a modular protein with architecture that enables simultaneous signaling and cargo trafficking.

PB1 Domain: Oligomerization And Signal Platform

The N-terminal PB1 domain mediates p62 self-assembly and higher-order complex formation. Oligomerization supports cargo clustering and concentrates autophagy machinery around ubiquitinated substrates.[@itakura2011][@komatsu2007]

LIR Motif: LC3/GABARAP Coupling

The LC3-interacting region (LIR) directly binds Atg8-family proteins, functionally docking p62-cargo complexes to autophagosomal membranes.[@pankiv2007] This step is required for efficient selective autophagy of ubiquitinated inclusions.

UBA Domain: Ubiquitin Chain Recognition

The C-terminal UBA domain binds polyubiquitin chains and enables cargo selection. Disease-associated changes in p62 function can impair this recognition-to-delivery step and produce apparent "cargo capture without clearance" states.[@pankiv2007][@le2013]

KIR Region: KEAP1-NRF2 Redox Interface

A KEAP1-interacting region allows p62 to modulate NRF2 signaling. Under stress, p62 can sequester KEAP1 and enhance antioxidant transcription programs, creating feedback between proteostasis demand and redox defense.[@ichimura2013][@jain2010]

Core Mechanisms Relevant To Neurodegeneration

1. Selective Autophagy Of Ubiquitinated Cargo

p62 is a canonical selective autophagy receptor: it links ubiquitinated proteins to autophagosomes via LC3 binding.[@pankiv2007] Experimental disruption of p62 pathways increases aggregate burden and destabilizes cellular quality control.[@komatsu2007]

2. Flux Sensing Versus Cargo Throughput

Static p62 abundance is not equivalent to increased autophagic activity. High p62 may indicate active adaptation or blocked degradation, depending on lysosomal throughput and LC3 flux context.[@itakura2011][@menzies2015] For translational studies, p62 should therefore be interpreted with orthogonal flux measurements, not as a standalone endpoint.

3. Ubiquitylation/Phosphoregulation Of Receptor Activity

p62 function is dynamically tuned by post-translational modifications. Ubiquitylation can increase receptor activity for selective autophagy under ubiquitin stress, and phosphorylation-dependent regulation influences redox-signaling crosstalk and condensate behavior under stress.[@ichimura2013][@pan2016][@sun2018]

4. Proteostasis-Inflammation Coupling

By integrating stress-signaling inputs with degradative handling, p62 sits at a proteostasis-inflammation interface. In neurodegeneration, this coupling likely contributes to self-reinforcing loops between protein accumulation and tissue injury.[@son2018][@goode2020]

Human Genetics And Disease Associations

ALS/FTD Spectrum

SQSTM1 variants have been reported in patients with FTD and FTD-ALS phenotypes.[@le2013][@rubino2014] Functional follow-up studies support a mechanism where mutation-linked p62 dysregulation impairs selective autophagy and anti-oxidative stress buffering.[@goode2020]

From an evidence-quality perspective, SQSTM1 is a contributory risk/modifier axis in many cohorts rather than a single dominant driver in most sporadic disease. That distinction matters for trial design: pathway-stratified enrollment and mechanism-proximal endpoints are more defensible than broad unselected populations.

Interaction With TBK1-Centered Autophagy Networks

ALS-linked TBK1 perturbations can reduce p62 phosphorylation dynamics and alter downstream autophagic handling, including effects on pathogenic protein clearance pathways.[@ye2020] This places SQSTM1 within a broader autophagy receptor-kinase network where upstream defects can phenocopy direct receptor dysfunction.

Tauopathy Context

Although SQSTM1 mutations are not primary monogenic causes of classic 4R-[tau](/proteins/tau) syndromes, p62 pathway behavior remains biologically relevant because [tau](/proteins/tau) aggregation and lysosomal insufficiency converge on selective-autophagy reserve.[@menzies2015][@son2018] In this framework, p62 serves as a mechanistic bridge between aggregate burden and degradative capacity.

Translational And Biomarker Implications

Interpreting p62 In Preclinical And Clinical Studies

p62 should be modeled as a state variable, not a binary marker. Interpretation is strongest when combined with:

• LC3-II dynamics and validated flux assays.[@itakura2011][@menzies2015]
• Insoluble/soluble cargo partitioning profiles.[@pan2016]
• Oxidative-stress response markers when KEAP1-NRF2 engagement is expected.[@ichimura2013][@jain2010]
• Disease-context readouts such as [TDP-43](/mechanisms/tdp-43-proteinopathy)/tau burden and neuroinflammatory metrics.[@menzies2015][@ye2020]

What A "Good" p62 Shift Looks Like

A therapeutic decrease in p62 can indicate improved clearance, but only if accompanied by evidence of restored substrate turnover. A decrease without cargo movement can also reflect reduced receptor competence. Conversely, a transient increase may occur during effective mobilization of stressed proteomes.

Patient-Selection Logic

Programs targeting p62-adjacent pathways are likely most actionable in cohorts with documented autophagy-lysosome stress signatures, ALS/FTD-related proteostasis phenotypes, or molecular evidence of receptor-kinase network disruption.[@le2013][@goode2020][@ye2020]

Therapeutic Strategy Framing

Strategy A: Improve End-To-End Autophagy Throughput

Interventions should prioritize restoration of full cargo-to-lysosome flux, not isolated reduction of p62 signal intensity.[@menzies2015][@son2018]

Strategy B: Rebalance Receptor Regulation

Targeting phosphorylation/ubiquitylation control points that tune p62 receptor activity may improve selective cargo handling in genetically sensitized contexts.[@ichimura2013][@pan2016][@ye2020]

Strategy C: Couple Proteostasis And Redox Modulation

Because p62 couples degradative stress and NRF2 biology, combination approaches that co-manage aggregate load and oxidative stress may have better mechanistic coherence than single-axis programs.[@ichimura2013][@jain2010][@goode2020]

Evidence Boundaries And Open Questions

• Which SQSTM1 variant classes map reproducibly to disease-specific phenotypes versus broad proteostasis risk?
• Which p62 post-translational states are most predictive of treatment response across ALS/FTD versus tau-first syndromes?
• How should p62-centered biomarkers be harmonized across tissue compartments (CSF, blood, and tissue/pathology endpoints)?

Pathway & Interaction Diagram

Interactive diagram showing SQSTM1 key relationships in the SciDEX knowledge graph (15 connections shown).

See Also

• [Autophagy-Lysosomal Dysfunction](/mechanisms/autophagy-lysosomal-dysfunction)
• [Amyotrophic Lateral Sclerosis (ALS)](/diseases/amyotrophic-lateral-sclerosis)
• [Frontotemporal Dementia](/diseases/frontotemporal-dementia)
• [Tauopathy](/mechanisms/tauopathy)

External Links

• [UniProt: sqstm1](https://www.uniprot.org/)
• [PubMed: sqstm1](https://pubmed.ncbi.nlm.nih.gov/?term=sqstm1+neurodegeneration)

References