gC1qR

gC1qR, or globular C1q receptor, is a multifunctional human protein encoded by the C1QBP gene. It is also known as HABP1 (hyaluronan-binding protein 1) and by its protein name C1QBP. The molecule was originally identified as a receptor for the globular heads of C1q, a component of the classical complement pathway, but it interacts with a range of other ligands beyond C1q, including hyaluronic acid and various extracellular matrix components. This broad ligand binding underpins its proposed involvement in immune recognition, cell adhesion, and signal transduction.

The protein is ubiquitously expressed and localizes to multiple cellular compartments, including mitochondria, cytosol, nucleus, and the cell surface. Its distribution can vary by cell type and physiological state, reflecting its diverse roles. In mitochondria, gC1qR/HABP1 is thought to contribute to mitochondrial function and possibly protein maturation or chaperone-like activities. At the cell surface and in the cytoplasm, it can act as a signaling adaptor, influencing pathways related to inflammation, apoptosis, and metabolism.

Clinical and biomedical relevance: Altered expression or function of gC1qR has been reported in various contexts, including cancer, viral infection, and autoimmune or inflammatory diseases. In cancer models, changes in gC1qR levels have been associated with differences in tumor growth or progression, though findings are often context-dependent. Some pathogens have been described as exploiting gC1qR for entry or replication, highlighting its potential role in host–pathogen interactions.

See also: C1QBP gene; complement system; hyaluronan.