Neutrophil Gelatinase Associated Lipocalin: Structure, Function and Role in Human Pathogenesis

Glycoproteins have a unique position in the pathogenesis of human diseases. Most of the commonly employed protein biomarkers are glycoproteins. Examples include CA19-9 (carbohydrate antigen 19-9) to follow-up patients with pancreatic cancer, CEA (carcinoembryonic antigen) for multiple solid tumors and CA125 (carbohydrate antigen 125) used in the diagnosis, follow-up and therapy of patients with ovarian cancer. Most of these glycoproteins are large molecules. However, there is a family of smaller, secreted glycoproteins (called lipocalins) that are important in the maintenance of health and in combating diseases effectively. A prototype of this family is a small, secreted glycoprotein called Neutrophil gelatinase associated lipocalin or NGAL. In recent years, NGAL has emerged as a novel biomarker in several benign and malignant diseases. Further, studies in cultured cells and in murine models have revealed a pivotal role for this molecule in several physiological processes and pathological conditions. In this Chapter, we review the biology of lipocalins, focusing specifically on NGAL and its role in human health and disease.