About GPC / Glypican:
Glypican has been identified in mammals. They are part of one or two families of proteoglycans. Other associated families are called syndecans. In mammals, six glypicans have been found. These are referred to as GPC1 through to GPC6. Two glypicans have been found in Drosophila, referred to as daily or daily-like.
An additional glypican has also been identified. This is thought to play an important role in developmental morphogenesis. It is believed to regulate the Wnt and Hedgehog cell signalling pathways. These have also been marked as regulators for fibroblast growth and protein signalling.
In terms of structure, the six glypican proteins thought to be similar in size, particularly in mammals. The core protein is a similar size, and the location of the amino acid sequence is conserved. They also seem to have a moderately similar amino acid structure. It is also thought the fourteen conserved cysteine residues are vital it's a three-dimensional shape.
The function of glypican proteins is not yet fully understood, but they are implicated in the Wnt and Hedgehog signalling pathways that serve as a signal for fibroblast growth factors. The proteins also have to regulate functions and contribute to specific cell growth. The regulated pathways are still not fully transparent.
Where are the Glypicans located? Well, the GPC5 and GPC6 dit next to each other on the 13q32 chromosome in humans. These are the GPC3 and GPC4 proteins. Some suggest this shows that glypicans evolved from a gene duplication event, but further investigation is needed to confirm this.