The sodium/phosphate cotransporter is a member of the phosphate:Na⁺ symporter (PNaS) family within the

TOG Superfamily The transporter-opsin-G protein-coupled receptor (TOG) superfamily is a protein superfamily of integral membrane proteins, usually of 7 or 8 transmembrane alpha-helical segments (TMSs). It includes (1) ion-translocating microbial rhodopsins and (2) ...

of transport proteins as specified in the Transporter Classification Database (TCDB).

Nomenclature

Sodium/phosphate cotransporters are also known as: * Na⁺-P_i cotransport proteins (NaPi-2a) * Sodium-dependent phosphate transporters * Sodium-dependent phosphate symporters * Phosphate:Na⁺ symporters

PNaS family

The Phosphate:Na⁺ Symporter (PNaS) family (TC# ) includes several closely related, functionally characterized, sodium-dependent, inorganic phosphate (Pi) transporter (NPT) proteins from mammals. Other organisms that possess PNaS family members include many in eukaryotic, bacterial and archaeal phyla. Bacterial sodium:phosphate symporters, NptA of ''Vibrio cholerae''
TC#2.A.58.1.2
and YjbB of ''E. coli''
TC# 2.A.58.2.1
have been functionally characterized. The well-characterized mammalian proteins are found in renal (IIa isoform) and intestinal (IIb isoform) brush border membranes and are about 640 amino acyl residues long with 8-12 putative TMSs. The N- and C-termini both reside in the cytoplasm, and a large hydrophilic loop is localized between trans-membrane segments (TMSs) 3 and 4. While IIa isoforms are pH-dependent, IIb isoforms are pH-independent. The IIa sodium phosphate symporter isoform is a functional monomer, but it interacts with PDZ proteins which probably mediate apical sorting, parathyroid hormone-controlled endocytosis and/or lysosomal sorting of internalized transporters.

Transport reaction

The transport reaction catalyzed by the mammalian proteins is: :P_i (out) + 3 Na⁺ (out) ⇌ P_i (in) + 3 Na⁺ (in).

Human PNaS proteins

There are several known sodium-dependent phosphate transporters found in humans. For example, the protein 2A is encoded by the solute carrier family 34, member 1 (''SLC34A1'')

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

and facilitates uptake of phosphate for normal cellular functions including cellular metabolism, signal transduction, and nucleic acid and lipid synthesis. The PNaS family is also called the SLC34 family. Other known sodium-dependent phosphate transporters found in humans include (but are not limited to): * Sodium-Phosphate Cotransporter Proteins, Type I
TC# 2.A.1.14
: **

SLC17A1 Sodium-dependent phosphate transport protein 1 is a protein that in humans is encoded by the ''SLC17A1'' gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." me ...

(NPT1) ** SLC17A2 (NPT3) ** SLC17A3 (NPT4) ** SLC17A4 * Sodium-Phosphate Cotransporter Proteins, Type II
TC# 2.A.58
: **

SLC34A1 Sodium-dependent phosphate transport protein 2A, also known as Na+-Pi cotransporter 2a (NaPi-2a), is a protein in humans that is encoded by the ''SLC34A1'' gene. This gene encodes a member of the type II sodium-phosphate cotransporter family. Fu ...

(NPTIIa) **

SLC34A2 Sodium-dependent phosphate transport protein 2B (NaPi2b) is a protein that in humans is encoded by the ''SLC34A2'' gene. Clinical significance Sodium-dependent phosphate transport protein 2b (NaPi2b) is a tumor-associated antigen. See also * So ...

(NPTIIb), codes for sodium-dependent phosphate transport protein 2b ( NaPi2b), a

tumor-associated antigen Tumor antigen is an antigenic substance produced in tumor Cell (biology), cells, i.e., it triggers an immune response in the Host (biology), host. Tumor antigens are useful tumor markers in identifying tumor cells with diagnostic tests and are po ...

. **

SLC34A3 Sodium-dependent phosphate transport protein 2C is a protein that in humans is encoded by the ''SLC34A3'' gene. Function SLC34A3 contributes to the maintenance of phosphate, inorganic phosphate concentration at the kidney. Interactions SLC ...

(NPTIIc) * Sodium-Phosphate Cotransporter Proteins, Type III
TC# 2.A.20
: **

SLC20A1 Sodium-dependent phosphate transporter 1 is a protein that in humans is encoded by the ''SLC20A1'' gene. Retrovirus receptors allow infection of human and murine cells by various retroviruses. The receptors that have been identified at the molecul ...

(PIT1) **

SLC20A2 Sodium-dependent phosphate transporter 2 is a protein that in humans is encoded by the ''SLC20A2'' gene. Genomics This gene is found on the short arm of chromosome 8 (8p12-p11) on the minus (Crick) strand. It is 123,077 bases in length. The encod ...

(PIT2)

Antibody

Lifastuzumab vedotin is a

monoclonal antibody A monoclonal antibody (mAb, more rarely called moAb) is an antibody produced from a cell Lineage made by cloning a unique white blood cell. All subsequent antibodies derived this way trace back to a unique parent cell. Monoclonal antibodies ca ...

for the sodium/phosphate cotransporter that is under development for the treatment of

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

References

External links

Transporter Classification Database
* Solute carrier family {{membrane-protein-stub