PPIG (Peptidyl-Prolyl Isomerase G), also known as cyclophilin G, is a member of the immunophilin protein family characterized by its peptidyl-prolyl cis-trans isomerase (PPIase) activity. This enzyme facilitates protein folding by catalyzing the isomerization of proline peptide bonds, a rate-limiting step in conformational changes. PPIG shares a conserved cyclophilin-like domain but contains unique structural features, including a C-terminal serine/arginine-rich (SR) domain, implicating roles in RNA splicing and mRNA metabolism. It interacts with components of the spliceosome and may regulate pre-mRNA processing.
PPIG antibodies are essential tools for studying its expression, localization, and molecular interactions. Research has linked PPIG to cancer progression, neurodegenerative diseases, and viral infections. For instance, PPIG overexpression is observed in certain leukemias and solid tumors, where it may promote cell proliferation or chemoresistance. In neurons, PPIG has been associated with stress granule dynamics, suggesting a role in cellular stress responses. Additionally, PPIG interacts with viral proteins (e.g., HIV-1 Rev), influencing viral replication cycles. Antibodies targeting PPIG enable detection via techniques like Western blot, immunofluorescence, and immunohistochemistry, aiding mechanistic studies in disease models. Recent studies also explore PPIG's involvement in immune regulation, potentially modulating T-cell signaling pathways. Its dual functions in protein folding and RNA processing make PPIG a multifaceted protein of growing interest in cell biology and translational research.