Gelatinaseassociated

Gelatinase-associated lipocalin, commonly abbreviated NGAL and also known as lipocalin-2, is a small secreted protein that is a member of the lipocalin protein family. It is named for its historical association with the neutrophil enzyme matrix metalloproteinase-9 (MMP-9), a gelatinase, from which it was first isolated as a tightly bound complex.

NGAL is encoded by the LCN2 gene in humans. It is produced by neutrophils and various epithelial cells, including renal tubular cells, and its secretion is upregulated by inflammatory signals. The protein adopts the typical lipocalin fold with a beta-barrel that forms a hydrophobic binding pocket capable of binding small hydrophobic molecules, including bacterial siderophores.

Functional roles include innate immune defense through iron sequestration from bacteria via siderophore binding, thus inhibiting bacterial growth. NGAL also interacts with MMP-9, forming a complex that can modulate gelatinase activity and may influence extracellular matrix remodeling. In the kidney, tubular cells release NGAL in response to injury, making it one of the most studied early biomarkers of acute kidney injury.

Clinically, NGAL is measured in blood and urine to assess kidney function and injury. Elevated levels are observed in AKI and sepsis, and NGAL levels have been studied as prognostic markers in various cancers and inflammatory diseases. The specificity of NGAL for different conditions is limited, but it remains a widely used biomarker in research and some clinical settings.