SLC34A2 — Solute Carrier Family 3 Member 4A2 (SLC34A2)

SLC34A2 — Solute Carrier Family 3 Member 4A2 (SLC34A2)

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">SLC34A2 — Solute Carrier Family 3 Member 4A2 (SLC34A2)</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td>SLC34A2</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Solute Carrier Family 34 Member 2 (Sodium-Phosphate Transporter 2)</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>4p15</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>[10568](https://www.ncbi.nlm.nih.gov/gene/10568)</td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>[604236](https://www.omim.org/entry/604236)</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000140557</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>[O75478](https://www.uniprot.org/uniprot/O75478)</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td>Pulmonary alveolar proteinosis, Hypophosphatemia, Sarcoidosis</td>
</tr>
</table>

{{.infobox .infobox-gene}}

Overview

The SLC34A2 gene encodes Sodium-Phosphate Transporter 2 (NaPi-IIb), a membrane protein that mediates phosphate uptake across epithelial cells [@napiiib]. NaPi-IIb is expressed in multiple tissues, including the lung, intestine, kidney, and brain, where it plays essential roles in phosphate homeostasis [@phosphate].

SLC34A2 — Solute Carrier Family 3 Member 4A2 (SLC34A2)

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">SLC34A2 — Solute Carrier Family 3 Member 4A2 (SLC34A2)</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td>SLC34A2</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Solute Carrier Family 34 Member 2 (Sodium-Phosphate Transporter 2)</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>4p15</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>[10568](https://www.ncbi.nlm.nih.gov/gene/10568)</td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>[604236](https://www.omim.org/entry/604236)</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000140557</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>[O75478](https://www.uniprot.org/uniprot/O75478)</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td>Pulmonary alveolar proteinosis, Hypophosphatemia, Sarcoidosis</td>
</tr>
</table>

{{.infobox .infobox-gene}}

Overview

The SLC34A2 gene encodes Sodium-Phosphate Transporter 2 (NaPi-IIb), a membrane protein that mediates phosphate uptake across epithelial cells [@napiiib]. NaPi-IIb is expressed in multiple tissues, including the lung, intestine, kidney, and brain, where it plays essential roles in phosphate homeostasis [@phosphate].

Phosphate is critical for numerous biological processes, including bone mineralization, energy metabolism (ATP), signal transduction, and nucleic acid synthesis. Proper phosphate balance is maintained through the coordinated action of intestinal absorption, renal reabsorption, and cellular uptake transporters like NaPi-IIb [@phosphatea].

Function and Mechanism

Sodium-Dependent Phosphate Transport

NaPi-IIb (SLC34A2) operates as a secondary active transporter, coupling phosphate (Pi) uptake to the inward sodium gradient. The stoichiometry is typically 3 Na⁺: 1 HPO₄²⁻ (or 2 Na⁺: 1 H₂PO₄⁻), making the transport electrogenic [@napiiiba].

Key characteristics:

• Apical membrane localization: In polarized epithelial cells
• Sodium-dependent: Driven by Na⁺ gradient
• Electrogenic: Generates inward current
• pH-sensitive: Activity affected by extracellular pH [@sodiumcoupled]

Regulation

NaPi-IIb activity is regulated by:

• Dietary phosphate: Downregulated during high-phosphate diet
• Parathyroid hormone (PTH): PTH decreases NaPi-IIb expression
• Fibroblast growth factor 23 (FGF23): Regulates phosphate metabolism
• Vitamin D: Enhances intestinal phosphate absorption (indirectly) [@regulation]

Expression Pattern

NaPi-IIb is expressed in several tissues:

• Lung: Type II alveolar epithelial cells - critical for pulmonary surfactant recycling
• Intestine: Apical membrane of enterocytes - major site of dietary phosphate absorption
• Kidney: Proximal tubules - contributes to renal phosphate reabsorption
• Liver: Hepatocytes
• Brain: [Neurons](/entities/neurons) and glial cells - relevant to neuronal phosphate metabolism [@tissue]

Role in Neurological Function

Brain Phosphate Metabolism

Phosphate is essential for neuronal function:

• ATP production: Neurons have high energy demands
• Signal transduction: Many second messengers involve phosphorylation
• Membrane lipids: Phosphate is a component of phospholipids
• Nucleic acids: DNA/RNA synthesis requires phosphate [@phosphateb]

Neurodegeneration Relevance

While not directly causative, phosphate dysregulation may contribute to:

• Alzheimer's disease: Altered phosphate metabolism affects [tau](/proteins/tau) phosphorylation
• Parkinson's disease: Energy deficits may involve phosphate handling
• Amyotrophic lateral sclerosis: Energy metabolism alterations [@phosphatec]

Pulmonary Alveolar Proteinosis

SLC34A2 mutations cause pulmonary alveolar proteinosis (PAP), a condition characterized by accumulation of surfactant in the alveoli. While primarily a lung disease, PAP can have neurological complications due to:

• Chronic hypoxia
• Impaired gas exchange
• Potential for secondary neurological complications [@slca]

Disease Associations

Pulmonary Alveolar Proteinosis

Homozygous or compound heterozygous mutations in SLC34A2 cause PAP, characterized by:

• Accumulation of surfactant proteins and lipids in alveoli
• Impaired gas exchange
• Dyspnea and hypoxia
• Increased susceptibility to infections [@pulmonary]

Sarcoidosis

SLC34A2 expression is altered in sarcoidosis, a multisystem granulomatous disorder. The transporter may play a role in the inflammatory response and granuloma formation [@napiiibb].

Hypophosphatemia

While SLC34A2 mutations are not a common cause of hypophosphatemia, the transporter's role in phosphate homeostasis means it may contribute to phosphate balance disorders [@phosphated].

Therapeutic Implications

NaPi-IIb is a therapeutic target:

• Phosphate binders: For hyperphosphatemia in chronic kidney disease
• Drug development: Small molecules to modulate NaPi-IIb activity
• Gene therapy: Potential for SLC34A2-related PAP [@napiiibc]

See Also

• [SLC34A1](/genes/slc34a1) - NaPi-IIa (kidney-specific phosphate transporter)
• [SLC34A3](/genes/slc34a3) - NaPi-IIc
• [Phosphate homeostasis](/mechanisms/phosphate-homeostasis)
• [Pulmonary alveolar proteinosis](/diseases/pulmonary-alveolar-proteinosis)

References