Reviewing the Developing Significance of the Serine Protease PRSS23.

The serine protease 23 (PRSS23) is a highly conserved member of trypsin-like serine proteases, which are associated with numerous essential processes, including digestion, blood coagulation, fibrinolysis, development, fertilization, apoptosis, and immunity. Original reports on PRSS23 unfolded not earlier than 2006 when a molecular biology study characterized and described PRSS23 as an ovarian protease. Then, in 2012, another important study was published linking PRSS23 with proliferation of breast cancer cells by an estrogen receptor 1 (ESR1)-dependent transcriptional activation of the serine protease. Thereafter, a developmental study in zebrafish reported the implication of PRSS23 in endothelial-to-mesenchymal transition (EndMT) during cardiac valve formation. Although these early studies on PRSS23 have revealed its involvement in some critical or fundamental processes, only in recent years an increasing number of studies have evolved describing the expression and functions of PRSS23 in various normal physiological conditions, diseases, and experimental configurations. Besides breast cancer, PRSS23 has been shown to be involved in different types of malignancies, e.g., in gastric cancer, where drug screening found that the protease inhibitor tipranavir impedes cancer-promoting PRSS23 expression. New innovative techniques such as single cell RNA-sequencing (scRNA-seq) and bioinformatics studies accelerated the discovery of gene expression changes in smaller cell populations, which, e.g., led to the identification of marked PRSS23 expression in a myofibroblast-like subpopulation in localized scleroderma. This review compiles major and significant research results that have contributed to our current knowledge of PRSS23 and briefly discusses where prospective studies could add to our understanding of this versatile serine protease.