Lipocalin-2/LCN2 (LCN2) Active Protein

LCN2: Iron-trafficking protein involved in multiple processes such as apoptosis, innate immunity and renal development. Binds iron through association with 2,5-dihydroxybenzoic acid (2,5- DHBA), a siderophore that shares structural similarities with bacterial enterobactin, and delivers or removes iron from the cell, depending on the context. Iron-bound form (holo-24p3) is internalized following binding to the SLC22A17 (24p3R) receptor, leading to release of iron and subsequent increase of intracellular iron concentration. In contrast, association of the iron-free form (apo-24p3) with the SLC22A17 (24p3R) receptor is followed by association with an intracellular siderophore, iron chelation and iron transfer to the extracellular medium, thereby reducing intracellular iron concentration. Involved in apoptosis due to interleukin-3 (IL3) deprivation: iron-loaded form increases intracellular iron concentration without promoting apoptosis, while iron-free form decreases intracellular iron levels, inducing expression of the proapoptotic protein BCL2L11/BIM, resulting in apoptosis. Involved in innate immunity, possibly by sequestrating iron, leading to limit bacterial growth. Belongs to the calycin superfamily. Lipocalin family. 2 isoforms of the human protein are produced by alternative splicing.

Protein type: Secreted; Secreted, signal peptide

Chromosomal Location of Human Ortholog: 9q34

Cellular Component: extracellular space; extracellular region; cytosol

Molecular Function: protein homodimerization activity; protease binding; transporter activity; iron ion binding

Biological Process: response to drug; cellular response to nutrient levels; cellular iron ion homeostasis; response to virus; positive regulation of cell projection organization and biogenesis; siderophore transport; innate immune response; ion transport; response to herbicide; transmembrane transport