Virtual Screening of Transmembrane Serine Protease Inhibitors

The human family of type II transmembrane serine proteases includes 17 members. The defining features of these proteases are an N-terminal transmembrane domain and a C-terminal serine protease of the chymotrypsin (S1) fold, separated from each other by a variable stem region. Recently accumulated evidence suggests a critical role for these proteases in development of cancer and metastatic capacity. Both the cancer relevance and the accessibility of the extracellularly oriented catalytic domain for therapeutic and imaging agents have fueled drug discovery interest in the type II class of transmembrane serine proteases. Typically, the initial hit discovery processes aim to identify molecules with verifiable activity at the drug target and with sufficient drug-like characters. We present here protocols for structure-based virtual screening of candidate ligands for transmembrane serine protease hepsin. The methods describe use of the 3D structure of the catalytic site of hepsin for molecular docking with ZINC, which is a molecular database of > 30 million purchasable compounds. Small candidate subsets were experimentally tested with demonstrable hits, which provided meaningful cues of the ligand structures for further lead development.