SMAD4 Protein

SMAD4 Protein

Introduction

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">SMAD4 Protein</th>
</tr>
<tr>
<td class="label">Protein Name</td>
<td>SMAD4</td>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>SMAD4</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q99707</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>60 kDa</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>552 amino acids</td>
</tr>
<tr>
<td class="label">PDB Structures</td>
<td>1G1J, 1GGK, 1MR1, 1O7W, 2FLB</td>
</tr>
<tr>
<td class="label">Subcellular Localization</td>
<td>Cytoplasm, nucleus (upon signaling)</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a href="/wiki/carcinoma" style="color:#ef9a9a">Carcinoma</a>, <a href="/wiki/colorectal-cancer" style="color:#ef9a9a">Colorectal Cancer</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">111 edges</a></td>
</tr>
</table>

SMAD4 Protein

Introduction

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">SMAD4 Protein</th>
</tr>
<tr>
<td class="label">Protein Name</td>
<td>SMAD4</td>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>SMAD4</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q99707</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>60 kDa</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>552 amino acids</td>
</tr>
<tr>
<td class="label">PDB Structures</td>
<td>1G1J, 1GGK, 1MR1, 1O7W, 2FLB</td>
</tr>
<tr>
<td class="label">Subcellular Localization</td>
<td>Cytoplasm, nucleus (upon signaling)</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a href="/wiki/carcinoma" style="color:#ef9a9a">Carcinoma</a>, <a href="/wiki/colorectal-cancer" style="color:#ef9a9a">Colorectal Cancer</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">111 edges</a></td>
</tr>
</table>

SMAD4 (SMAD Family Member 4) is the central co-mediator of TGF-beta signaling in the nervous system. This protein partners with receptor-regulated SMADs (SMAD2, SMAD3) to transduce TGF-beta signals from the cell surface to the nucleus, regulating gene expression programs that control neuroinflammation, neuronal survival, and synaptic plasticity.

Overview

SMAD4 (also known as DPC4 - Deleted in Pancreatic Cancer 4) is a 552 amino acid protein that serves as the central mediator of canonical TGF-beta signaling[@massague2000]. Unlike other SMADs, SMAD4 is not a direct substrate of TGF-beta receptors; instead, it forms heteromeric complexes with phosphorylated SMAD2/SMAD3 to regulate transcription of target genes[@heldin2021].

Protein Information

Protein Structure

MH1 Domain (1-150 aa)

• DNA-binding domain: Recognizes SMAD-binding elements (SBE) with consensus sequence GTCTAGAC
• Nuclear localization signal: Contains functional NLS
• Beta-hairpin insertion: Critical for DNA binding specificity

MH2 Domain (300-550 aa)

• Heteromeric interface: Mediates complex formation with SMAD2/SMAD3
• Trimerization surface: Enables trimeric complex formation
• Transactivation domain: Interacts with transcriptional co-activators and co-repressors

Linker Region (151-299 aa)

• Regulatory sequences: Contains phosphorylation sites and protein interaction motifs
• Nuclear export signal: Controls subcellular localization

Normal Function in the Nervous System

TGF-beta Signal Transduction

Functions in CNS

• Neuroinflammation regulation: Controls microglial activation and cytokine production[@brionne2021]
• Neuronal survival: Mediates TGF-beta-induced neuroprotective effects[@kane2018]
• Synaptic plasticity: Modulates excitatory synaptic transmission[@ferguson2019]
• Transcriptional regulation: Partners with various transcription factors[@wrana2019]

Role in Disease

Alzheimer's Disease

• SMAD4 is dysregulated in AD brain tissue[@caraci2021]
• TGF-beta/SMAD4 signaling regulates amyloid processing[@wysscoray2020]
• Loss of SMAD4 function contributes to neuroinflammation[@tolar2020]

Parkinson's Disease

• SMAD4 protects dopaminergic [neurons](/entities/neurons) from oxidative stress[@rai2022]
• Altered SMAD4 expression in PD substantia nigra[@tong2019]

Amyotrophic Lateral Sclerosis

• SMAD4 signaling influences motor neuron survival[@dormann2020]
• Dysregulated TGF-beta/SMAD4 pathway in ALS[@ilieva2019]

Therapeutic Targeting

• SMAD4 modulators: Developing compounds that enhance SMAD4 signaling[@akhurst2021]
• TGF-beta agonists: Upstream activation of SMAD4 pathway[@sakauchi2021]

Key Publications

See Also

• [SMAD4 Gene](/genes/smad4)
• [SMAD2 Protein](/proteins/smad2-protein)
• [SMAD3 Protein](/proteins/smad3-protein)
• [TGFBR1 Protein](/proteins/tgfrb1-protein)
• [TGFBR2 Protein](/proteins/tgfrb2-protein)
• [TGF-beta Signaling Pathway](/mechanisms/tgf-beta-signaling-pathway)

Background

The study of Smad4 Protein 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.

External Links

• [PubMed](https://pubmed.ncbi.nlm.nih.gov/) - Biomedical literature
• [Alzheimer's Disease Neuroimaging Initiative](https://adni.loni.usc.edu/) - Research data
• [Allen Brain Atlas](https://brain-map.org/) - Brain gene expression data

References