LCN2

LCN2, also known as lipocalin-2 or neutrophil gelatinase-associated lipocalin (NGAL), is a small secreted glycoprotein that belongs to the lipocalin protein family. In humans, it is encoded by the LCN2 gene. The protein is produced by neutrophils and by various epithelia in organs such as the kidney, liver, and gastrointestinal tract, and it circulates in blood and urine.

Functionally, LCN2 contributes to innate immunity by binding siderophores, iron-chelating molecules secreted by bacteria, and sequestering these siderophores to limit bacterial iron acquisition and growth. It also acts as an inflammatory mediator and can interact with matrix metalloproteinase-9 (MMP-9), forming a complex that may influence extracellular matrix remodeling. In adipose tissue, LCN2 functions as an adipokine linked to metabolic regulation, obesity, and insulin resistance.

Clinically, LCN2 is widely used as a biomarker of kidney tubular injury; urinary and plasma levels rise rapidly after ischemic or nephrotoxic damage, often preceding creatinine elevations. Elevated LCN2 has also been observed in sepsis and various cancers, and ongoing research explores its prognostic value and role in tumor biology.

Regulation and structure-wise, LCN2 expression is upregulated by inflammatory signals, including IL-1β, TNF-α, and IL-6, and is regulated in part by NF-κB. Structurally, lipocalin-2 is about 25 kDa and adopts a typical lipocalin β-barrel fold; it can exist as a monomer and form a heterodimer with MMP-9.