OPN

OPN Full Name

Osteopontin

OPN Introduction

Osteopontin (OPN), also known as SPP1, is a highly phosphorylated glycoprotein that belongs to the SIBLING (Small Integrin-Binding Ligand N-linked Glycoprotein) family, playing a central role in connecting the extracellular matrix (ECM) to cell surface receptors such as integrins and CD44. Structurally, OPN contains key functional motifs, including an RGD sequence critical for cell adhesion and a thrombin cleavage site, and undergoes extensive post-translational modifications like glycosylation and phosphorylation. These modifications significantly influence its ability to mediate cell adhesion, survival, migration, and signal transduction. Beyond its structural roles, OPN acts as a multifunctional mediator in bone remodeling, dentin formation, immune regulation, and inflammatory responses, highlighting its broad biological relevance and its potential as a therapeutic target.

In the context of tissue dynamics, OPN is a pivotal regulator of extracellular matrix remodeling, interacting with key ECM components such as collagen and fibronectin. Its activity influences the balance between ECM synthesis and degradation, and it plays a crucial role in processes like epithelial-mesenchymal transition (EMT), which underlies tissue fibrosis and cancer metastasis. Overexpression of OPN can drive cells toward a migratory and invasive phenotype, while its regulation of cell adhesion molecules and matrix metalloproteinases (MMPs) contributes to pathological remodeling and fibrosis. These properties position OPN as a central "hub" in ECM-mediated tissue pathology, offering insight into mechanisms of chronic inflammatory conditions and fibrotic diseases.

OPN also has profound implications in immunology and oncology, where it modulates immune cell recruitment and polarization. By binding to integrins such as αvβ3 and CD44, OPN influences the behavior of macrophages, dendritic cells, and T cells, often promoting immunosuppressive M2 macrophage polarization in the tumor microenvironment, which supports tumor progression. Its signaling pathways—including NF-κB, STAT3, and PI3K/Akt—coordinate inflammatory responses and cell survival, while its dual immunomodulatory nature allows it to both amplify and restrain immune reactions depending on the context. Furthermore, OPN exerts complex regulatory effects on B cell responses, affecting activation, antibody production, and cytokine secretion, thereby linking it to autoimmune disorders and highlighting its potential as a biomarker and therapeutic target across a range of diseases.

Alternate Names for OPN

BNSP; Bone sialoprotein 1; BSP I; BSPI; Early T lymphocyte activation 1; ETA 1; ETA1; MGC110940; Nephropontin; OPN

• 1.Liu Y, et al.; Relationship between SPP1 (Osteopontin) and extracellular matrix dynamics: a comprehensive review. Front Med (Lausanne). 2025, 12:1700652.
  2.Panda VK, et al.; Osteopontin: A Key Multifaceted Regulator in Tumor Progression and Immunomodulation. Biomedicines. 2024, 12(7):1527.