Isoform 2 of Osteopontin

Osteopontin (SPP1) isoform 2 is a 300-amino acid secreted phosphoprotein involved in cell adhesion, migration, and immune regulation (UniProt: P10451-5). It functions as an extracellular matrix component and cytokine, playing roles in bone remodeling, wound healing, and inflammatory responses across multiple tissues.

Osteopontin is expressed in bone, kidney, immune cells, and the central nervous system, where it modulates microglial activation and neuroinflammatory pathways. The protein has been implicated in various pathological conditions involving inflammation and tissue remodeling.

In Alzheimer's disease, osteopontin isoform 2 is significantly upregulated in post-mortem AD brain tissue compared to age-matched controls (Chaparral AD proteomics), with a mean log2 fold-change of 1.39. This upregulation was detected via TMT-labeled quantitative proteomics across subcellular fractions of AD brain tissue, suggesting a potential role in AD-associated neuroinflammatory and degenerative processes.