Napsin-A antibody

Background of Napsin-A antibody

Napsin A gene codes for two aspartic proteinases precursor generally expressed in lungs and kidneys and its translational product is fully functional, glycosylated aspartic proteinase containing a RGF motif and an additional 18 residues at its C-terminal end. The Napsin B gene is expressed in exclusively in cells of the immune system and is expressed in several polymorphic form (1). Members of the aspartic protease family have been implicated in cancer progression. The aspartic protease napsin A is expressed in type II cells of the lung, where it is involved in the processing of surfactant protein B (SP-B). Napsin A expression in kidney is decrease in adenocarcinomas this result is consistent with earlier observations of loss of napsin A in high grade lung carcinomas (2). Mutation in the aspartic acid residue resulted in complete loss of enzymatic activity but it did not influence glycosylation, processing and intracellur localization.
Re-expression of napsin A in HEK-293 cells inhibit the tumor growth by mechanism independent of aspartic proteinase activity (2).
Interstitial lung disease (ILD) ail lung in children represent a rare heterogeneous group of respiratory disorders characterized by restrictive lung disease and diffuse infiltrates. Mutations in the surfactant proteins (SP-A, SP-B, SP-C and SP-D) and in the ABC binding cassette protein A3 (ABCA3) are found to be associated with pediatric ILD (3). While SP-A and SP-D play essential roles in the pulmonary immune defense, SP-B and SP-C lower the surface-tension and facilitate formation and stabilization of the surfactant film in young lungs. SP-B is expressed in type II non-ciliated bronchiolar epithelial cells in pre-pro-protein of 381 amino acids. After removal of 23amio acids form N-terminal end the pro-protein is proteolytically processed at the amino and carboxy terminal ends to mature SP-B protein of 79 amino acids by a cystein protease, cathapsin H and aspartylprotease Napsin (4). Napsin A is highly expressed in type II non-ciliated epithelial cells and is implicated in processing of the SP-B and SP-C pro-peptides (4).