FZD5 — Frizzled Class Receptor 5

FZD5 — Frizzled Class Receptor 5

Introduction

FZD5 (Frizzled Class Receptor 5) encodes a seven-transmembrane receptor that serves as a key Wnt ligand receptor in the central nervous system. FZD5 is one of the most widely expressed Frizzled receptors in the brain and plays critical roles in neural development, synaptic plasticity, and neuronal survival[@daniele2014]. Given the well-established involvement of Wnt signaling dysregulation in Alzheimer's disease (AD), FZD5 has emerged as a gene of significant interest in neurodegeneration research.

<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">FZD5</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>FZD5</td></tr>
<tr><td><strong>Full Name</strong></td><td>Frizzled Class Receptor 5</td></tr>
<tr><td><strong>Chromosome</strong></td><td>2q33.3</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td><a href="https://www.ncbi.nlm.nih.gov/gene/7852">7852</a></td></tr>
<tr><td><strong>OMIM</strong></td><td>602453</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000163235</td></tr>
<tr><td><strong>UniProt ID</strong></td><td><a href="https://www.uniprot.org/uniprot/Q9ULW1">Q9ULW1</a></td></tr>
<tr><td><strong>Protein Name</strong></td><td>Frizzled-5</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>Alzheimer's Disease, Retinal Degeneration, Cancer</td></tr>
</table>
</div>

Overview

FZD5 — Frizzled Class Receptor 5

Introduction

FZD5 (Frizzled Class Receptor 5) encodes a seven-transmembrane receptor that serves as a key Wnt ligand receptor in the central nervous system. FZD5 is one of the most widely expressed Frizzled receptors in the brain and plays critical roles in neural development, synaptic plasticity, and neuronal survival[@daniele2014]. Given the well-established involvement of Wnt signaling dysregulation in Alzheimer's disease (AD), FZD5 has emerged as a gene of significant interest in neurodegeneration research.

<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">FZD5</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>FZD5</td></tr>
<tr><td><strong>Full Name</strong></td><td>Frizzled Class Receptor 5</td></tr>
<tr><td><strong>Chromosome</strong></td><td>2q33.3</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td><a href="https://www.ncbi.nlm.nih.gov/gene/7852">7852</a></td></tr>
<tr><td><strong>OMIM</strong></td><td>602453</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000163235</td></tr>
<tr><td><strong>UniProt ID</strong></td><td><a href="https://www.uniprot.org/uniprot/Q9ULW1">Q9ULW1</a></td></tr>
<tr><td><strong>Protein Name</strong></td><td>Frizzled-5</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>Alzheimer's Disease, Retinal Degeneration, Cancer</td></tr>
</table>
</div>

Overview

FZD5 is a member of the Frizzled family of Wnt receptors, characterized by a seven-transmembrane domain structure resembling G-protein-coupled receptors. Unlike canonical Frizzled receptors that primarily signal through β-catenin, FZD5 can activate both canonical and non-canonical Wnt pathways depending on the cellular context and available ligands[@vassilieva2003].

In the nervous system, FZD5 is critically involved in:

• Neural tube patterning and brain development
• Neuronal polarization and axon guidance
• Synapse formation and plasticity
• Neuroprotection against toxic insults

Molecular Function

Wnt Signal Transduction

FZD5 functions as a receptor for multiple Wnt ligands, with particular affinity for Wnt1, Wnt2, Wnt3, Wnt3A, and Wnt5A. Upon ligand binding, FZD5 activates downstream signaling cascades[@chen2021]:

Canonical Wnt/β-catenin pathway:

• Activation of Dishevelled (DVL) proteins
• Inhibition of glycogen synthase kinase-3β (GSK-3β)
• Stabilization of β-catenin
• Transcriptional activation of target genes

• Wnt5a/Fzd5 activates planar cell polarity (PCP) signaling
• Modulates calcium signaling
• Regulates cytoskeletal dynamics

Neuroprotective Signaling

FZD5-mediated neuroprotection involves several mechanisms[@liu2018]:

Role in Alzheimer's Disease

Wnt Signaling Dysregulation

Multiple studies have documented reduced Wnt signaling in Alzheimer's disease brains. FZD5 expression is altered in AD, contributing to the overall decline in neuroprotective Wnt signaling[@inestrosa2012]:

• Reduced FZD5 mRNA and protein in AD prefrontal cortex
• Decreased Wnt ligand availability in the AD brain microenvironment
• Impaired downstream signaling despite receptor availability

Amyloid-Beta Toxicity

FZD5 activation provides protection against amyloid-beta (Aβ) toxicity, a central pathological feature of AD. The mechanisms include[@palomer2013]:

• Prevention of Aβ-induced synaptic loss
• Reduction of tau hyperphosphorylation
• Maintenance of neuronal calcium homeostasis
• Protection against mitochondrial dysfunction

Therapeutic Potential

FZD5 represents a potential therapeutic target for AD through several approaches[@martinez2019]:

• FZD5 agonists: Small molecules or peptides that activate FZD5
• Wnt pathway modulators: Compounds that enhance overall Wnt signaling
• Gene therapy: Delivery of FZD5 or Wnt ligands to the brain

Expression Pattern

Brain Expression

FZD5 is widely expressed throughout the human brain[@martinez2019]:

• Cortex: All layers, particularly layer II pyramidal neurons
• Hippocampus: CA1-CA3 pyramidal cells, dentate gyrus granule cells
• Cerebellum: Purkinje cells and granule cells
• Basal ganglia: Striatal medium spiny neurons
• Brainstem: Various nuclear regions

Development Expression

During brain development, FZD5 expression is highest in:

• Neural tube ventricular zone
• Cortical plate during corticogenesis
• Developing retina
• Migrating neurons

Disease Associations

| Disease | Association | Mechanism |
|---------|-------------|-----------|
| Alzheimer's Disease | Risk/Modifier | Wnt dysregulation, neuroprotection loss |
| Retinal Degeneration | Risk | Essential for retinal vascularization |
| Colorectal Cancer | Oncogenic | Wnt pathway activation |
| Glioma | Oncogenic | Enhanced proliferation |

Retinal Function

FZD5 is essential for proper retinal development and maintenance[@werk2018]:

• Controls retinal angiogenesis during development
• Regulates cone photoreceptor development
• Maintains retinal pigment epithelium
• Protects against age-related macular degeneration

Interactions

FZD5 interacts with several proteins[@liu2022]:

• WNT1, WNT2, WNT3, WNT3A, Wnt5A: Primary ligands
• LRP5, LRP6: Co-receptors for canonical signaling
• DVL1, DVL2, DVL3: Intracellular signaling effectors
• RSPO1, RSPO2, RSPO3: R-spondins (potentiators)
• GSK-3β: Key downstream kinase
• β-catenin: Transcriptional co-activator

Therapeutic Targeting

Several strategies are being explored to target FZD5 in disease[@ueno2020]:

• FZD5 agonists: Activate the receptor directly
• Wnt pathway activators: Increase overall pathway activity
• Monoclonal antibodies: Target FZD5 for specific applications

See Also

• [Wnt Signaling Pathway](/mechanisms/wnt-signaling-neurodegeneration) — Wnt pathway overview
• [Alzheimer's Disease](/diseases/alzheimers-disease) — Alzheimer's disease overview
• [FZD4 Gene](/genes/fzd4) — Related Frizzled receptor
• [GSK-3β](/proteins/gsk3-beta) — Key downstream kinase
• [Beta-catenin](/proteins/beta-catenin) — Wnt pathway effector
• [Amyloid-beta](/proteins/amyloid-beta) — AD pathological protein

External Links

• [NCBI Gene: FZD5](https://www.ncbi.nlm.nih.gov/gene/7852)
• [OMIM: FZD5](https://www.omim.org/entry/602453)
• [Ensembl: FZD5](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000163235)
• [UniProt: FZD5](https://www.uniprot.org/uniprot/Q9ULW1)
• [GeneCards: FZD5](https://www.genecards.org/cgi-bin/carddisp.pl?gene=FZD5)

References