PIST (PDZ protein interacting specifically with TC10), also known as GOPC (golgi associated PDZ and coiled-coil motif containing), CAL or FIG, is a 462 amino acid protein that localizes to the cytoplasm, as well as to the membrane of the golgi apparatus and to the cell junction. Expressed ubiquitously and containing one PDZ (DHR) domain, PIST functions as a homooligomer that interacts with a variety of proteins and plays a role in intracellular protein trafficking and degradation. Additionally, PIST is thought to regulate ionic currents via membrane channel modification and may also play a role in autophagy. Chromosomal aberrations in the gene encoding PIST are found in glioblastoma multiform (GBM), a common and aggressive form of brain tumor, suggesting a role for mutated PIST in carcinogenesis. Three isoforms of PIST exist due to alternative splicing events.