Glypican 4, also known as K-Glypican, is an approximately 220 kDa GPI-anchored heparan sulfate proteoglycan with a 60 kDa protein core. It is expressed in brain, kidney, adrenal gland, and fat tissue and binds to FGF basic. In the developing brain, Glypican 4 is found in lateral ventricles surrounding the telencephalon, the dentate gyrus, proliferating neuroepithelial cells, and neural precursors. It inhibits the dopaminergic differentiation of neurons. A 30 kDa cleaved form of Glypican 4 binds in cis to PTP sigma and contributes to excitatory synapse development and function. Glypican 4 is differentially expressed between adipose tissue depots. A soluble form can be released by adipocytes and circulates at elevated levels in obese patients with insulin resistance. This form binds and enhances signaling through the Insulin R, and it also supports adipocyte differentiation.