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PGAP3
post-GPI attachment to proteins phospholipase 3
PGAP3 is located on the long (q) arm of chromosome 17, at band 17q12. Arm ratio per GRCh38 - banding schematic.
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Overview
PGAP3 encodes post-GPI attachment to proteins phospholipase 3, an enzyme that participates in the biosynthesis and maturation of GPI anchors. These anchors are complex glycolipid structures that attach more than 150 different proteins to the cell membrane in humans, enabling proteins to function at the cell surface without spanning the membrane themselves.
GPI-anchored proteins play diverse roles in immunity, neuronal function, embryonic development, and blood cell biology. The PGAP3 enzyme specifically acts after the GPI anchor has been attached to a protein, trimming fatty acid chains to create the mature anchor form. Genetic changes affecting PGAP3 function can disrupt this maturation process, potentially altering the stability and activity of numerous cell-surface proteins.
What the gene does
The PGAP3 protein functions as a phospholipase that removes specific fatty acid chains from the inositol component of GPI anchors shortly after these anchors are attached to newly synthesised proteins. This fatty acid remodelling is thought to occur in the endoplasmic reticulum and represents one of several post-attachment modification steps required to produce fully mature GPI anchors.
By trimming particular lipid moieties, PGAP3 helps determine the final lipid composition of GPI anchors, which in turn influences how anchored proteins are sorted within the cell and transported to the plasma membrane. The enzyme works alongside other GPI-remodelling proteins in a sequential pathway. Although the precise substrate specificity and reaction mechanism remain areas of ongoing research, PGAP3 is considered essential for generating GPI structures that can properly localise anchored proteins to lipid rafts and other specialised membrane domains. Disruption of this remodelling step may compromise the surface expression or function of GPI-anchored proteins across multiple cell types.
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Chromosome location
PGAP3 is located on the long arm of chromosome 17 at position 17q12. This chromosomal region contains numerous genes involved in diverse cellular processes. The specific number of exons and precise gene structure for PGAP3 have not been extensively characterised in publicly available genomic databases, reflecting the gene's relatively recent functional annotation.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein.
Key variants
Genetic variants in PGAP3 include missense changes, deletions, and other alterations that may affect enzyme activity or protein stability. Because the gene encodes an enzyme with a specialised biochemical function, changes that reduce phospholipase activity could impair GPI anchor remodelling. The functional impact of individual variants depends on their location within the coding sequence and their effect on the enzyme's catalytic activity or cellular localisation.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.109G>T | p.Glu37Ter | Pathogenic | ★★☆☆ | Inborn genetic diseases |
c.265C>T | p.Gln89Ter | Pathogenic | ★★☆☆ | Hyperphosphatasia with intellectual disability syndrome 4 |
c.320C>T | p.Ser107Leu | Pathogenic/Likely pathogenic | ★★☆☆ | PGAP3-related disorder |
c.452dup | p.Trp152fs | Pathogenic | ★★☆☆ | Hyperphosphatasia with intellectual disability syndrome 4 |
c.558-10G>A | - | Pathogenic/Likely pathogenic | ★★☆☆ | Hyperphosphatasia with intellectual disability syndrome 4 |
c.639C>G | p.Tyr213Ter | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.694+1G>A | - | Pathogenic | ★★☆☆ | Hyperphosphatasia with intellectual disability syndrome 4 |
c.827C>T | p.Pro276Leu | Pathogenic/Likely pathogenic | ★★☆☆ | PGAP3-related disorder |
c.850C>T | p.His284Tyr | Pathogenic/Likely pathogenic | ★★☆☆ | Hyperphosphatasia with intellectual disability syndrome 4 |
c.851A>G | p.His284Arg | Pathogenic/Likely pathogenic | ★★☆☆ | Hyperphosphatasia with intellectual disability syndrome 4 |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Currently, no inherited conditions have been definitively associated with pathogenic variants in PGAP3 in major clinical databases. Research into the GPI anchor biosynthesis pathway continues, and future studies may identify specific disorders linked to PGAP3 dysfunction. GPI anchor defects in related genes have been associated with a spectrum of developmental and neurological phenotypes, suggesting that PGAP3 variants could theoretically contribute to similar clinical presentations if loss of function were to occur.
No disease links recorded for this gene in our reference set.
UK clinical status
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is a GPI anchor?
A GPI anchor is a glycolipid structure that attaches certain proteins to the outer surface of cell membranes. It allows proteins to be displayed at the cell surface without requiring the protein itself to span the membrane, and influences protein localisation and signalling.
How does PGAP3 differ from other GPI-related genes?
PGAP3 functions specifically to remodel GPI anchors after they have been attached to proteins, trimming fatty acid chains to produce the mature anchor form. Other GPI genes are involved in earlier assembly steps or different post-attachment modifications.
Is PGAP3 testing available on the NHS?
PGAP3 is not currently included in NHS Genomic Medicine Service gene panels, reflecting the limited clinical evidence linking variants in this gene to diagnosed inherited conditions at present.