High Temperature Requirement Factor A1 (HTRA1)

HTRA1 encodes a member of the trypsin family of serine proteases. This protein is a secreted enzyme that is proposed to regulate the availability of insulin-like growth factors (IGFs) by cleaving IGF-binding proteins. It has also been suggested to be a regulator of cell growth.The deduced 480-amino acid protein is 98% identical to the cow, guinea pig, and rabbit proteins. It contains an N terminus homologous to MAC25 (IGFBP7) with a conserved Kazal-type serine protease inhibitor motif, as well as a C-terminal PDZ domain. Semiquantitative RT-PCR and immunoblot analyses showed an approximately 7-fold increase of PRSS11 in osteoarthritis cartilage compared with controls. Functional and mutational analyses indicated that PRS11 is a serine protease dependent on the presence of a serine at position 328.