GPC gene family

The GPC genes provide instructions for making proteins called glypicans. These proteins are part of a larger group of proteins (superfamily) called proteoglycans. Proteoglycans consist of a core protein attached to one or more long, straight sugar molecules called glycosaminoglycan (GAG) chains. Some functions of proteoglycans are determined by their GAG chains.

Six glypican genes (designated GPC1 through GPC6) have been identified in humans. The proteins produced from these genes are each attached to molecules of heparan sulfate, which are a type of GAG chain. Heparan sulfate allows glypicans to bind to a variety of other proteins. Because glypicans have heparan sulfate as their GAG chains, they are described as heparan sulfate proteoglycans (HSPGs).

Glypicans are anchored to the cell membrane, where they interact with growth factors, immune system proteins called cytokines, and other proteins outside the cell. Glypicans appear to play important roles in development before birth. These proteins are involved in numerous cell functions including regulating cell growth and division (cell proliferation), cell survival, cell movement (migration), and the process by which cells mature to carry out specific functions (differentiation).

Changes in glypican structure and function are associated with several human diseases. For example, mutations in the GPC3 gene underlie a condition called Simpson-Golabi-Behmel syndrome, which is characterized by overgrowth of the body and other birth defects. Additionally, increased and decreased activity of some glypican genes (including GPC1 and GPC3) have been found in certain forms of cancer.