Extracellular proteases mediate the digestion of neighboring extracellular matrix components in initial tumor growth, allow desquamation of tumor cells into the surrounding environment, provide the basis for invasion of basement membranes in targeted metastatic organs and are required for release and activation of many growth and angiogenic factors. TMPRSS5 (transmembrane protease, serine 5), also known as spinesin, is a 457 amino acid single-pass type II membrane protein that is expressed specifically in brain and is thought to play a role in hearing. A member of the peptidase S1 family, TMPRSS5 contains one peptidase S1 domain and an SRCR domain, and is encoded by a gene that maps to human chromosome 11q23.2. Defects in the gene encoding TMPRSS5 are associated with deafness.