GPC1

Cell surface heparan sulfate proteoglycans are composed of a membrane-associated protein core substituted with a variable number of heparan sulfate chains. Members of the glypican-related integral membrane proteoglycan family (GRIPS) contain a core protein anchored to the cytoplasmic membrane via a glycosyl phosphatidylinositol linkage. These proteins may play a role in the control of cell division and growth regulation.

Full Name

glypican 1

Function

Cell surface proteoglycan that bears heparan sulfate. Binds, via the heparan sulfate side chains, alpha-4 (V) collagen and participates in Schwann cell myelination (By similarity).

May act as a catalyst in increasing the rate of conversion of prion protein PRPN(C) to PRNP(Sc) via associating (via the heparan sulfate side chains) with both forms of PRPN, targeting them to lipid rafts and facilitating their interaction. Required for proper skeletal muscle differentiation by sequestering FGF2 in lipid rafts preventing its binding to receptors (FGFRs) and inhibiting the FGF-mediated signaling.

Biological Process

Cell migration Source: GO_Central
Heparan sulfate proteoglycan catabolic process Source: UniProtKB
Myelin assembly Source: UniProtKB
Negative regulation of fibroblast growth factor receptor signaling pathway Source: UniProtKB
Positive regulation of skeletal muscle cell differentiation Source: UniProtKB
Regulation of protein localization to membrane Source: GO_Central
Schwann cell differentiation Source: UniProtKB

Cellular Location

Cell membrane; Endosome. S-nitrosylated form recycled in endosomes. Localizes to CAV1-containing vesicles close to the cell surface. Cleavage of heparan sulfate side chains takes place mainly in late endosomes. Associates with both forms of PRNP in lipid rafts. Colocalizes with APP in perinuclear compartments and with CP in intracellular compartments. Associates with fibrillar APP amyloid-beta peptides in lipid rafts in Alzheimer disease brains.
Secreted glypican-1: Extracellular space

Involvement in disease

Associates (via the heparan sulfate side chains) with fibrillar APP amyloid-beta peptides in primitive and classic amyloid plaques and may be involved in the deposition of these senile plaques in the Alzheimer disease (AD) brain (PubMed:15084524).
Misprocessing of GPC1 is found in fibroblasts of patients with Niemann-Pick Type C1 disease. This is due to the defective deaminative degradation of heparan sulfate chains (PubMed:16645004).

PTM

S-nitrosylated in a Cu2+-dependent manner. Nitric acid (NO) is released from the nitrosylated cysteines by ascorbate or by some other reducing agent, in a Cu2+ or Zn2+ dependent manner. This free nitric oxide is then capable of cleaving the heparan sulfate side chains.
N- and O-glycosylated. N-glycosylation is mainly of the complex type containing sialic acid. O-glycosylated with heparan sulfate. The heparan sulfate chains can be cleaved either by the action of heparanase or, degraded by a deaminative process that uses nitric oxide (NO) released from the S-nitrosylated cysteines. This process is triggered by ascorbate, or by some other reducing agent, in a Cu2+- or Zn2+ dependent manner. Cu2+ ions are provided by ceruloproteins such as APP, PRNP or CP which associate with GCP1 in intracellular compartments or lipid rafts.
This cell-associated glypican is further processed to give rise to a medium-released species.