OSCAR Human

The Osteoclast Associated, Immunoglobulin-Like Receptor (OSCAR) is a protein encoded by the OSCAR gene in humans. This receptor is a member of the leukocyte receptor complex (LRC) protein family, which plays a crucial role in the regulation of both innate and adaptive immune responses . OSCAR is specifically expressed in preosteoclasts and mature osteoclasts, making it an important regulator in bone homeostasis and osteoclast differentiation .

Osteoclasts are multinucleated cells responsible for bone resorption, a process essential for bone remodeling and homeostasis. These cells break down bone tissue, releasing minerals such as calcium into the bloodstream. The balance between bone resorption by osteoclasts and bone formation by osteoblasts is critical for maintaining healthy bone density and structure .

OSCAR functions as a costimulatory receptor that is vital for osteoclast differentiation. It interacts with collagen and other ligands to activate signaling pathways, including the nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) pathway, which is essential for the formation and function of osteoclasts . This receptor’s expression is highly conserved across different species, highlighting its importance in bone biology .

Beyond its role in bone metabolism, OSCAR is also involved in the immune system. It contributes to the regulation of immune responses by interacting with other immune cells. This dual function underscores the receptor’s significance in both osteoimmunology and bone health .

Mutations or dysregulation of the OSCAR gene can lead to various bone disorders and diseases. For instance, abnormal OSCAR activity has been associated with conditions such as osteoporosis, where excessive bone resorption leads to weakened bones . Understanding the mechanisms of OSCAR can aid in developing therapeutic strategies for such bone-related diseases.