Structure-Based Engineering of a PTPsigma Ectodomain for Enhanced Solubility and Productivity.

Protein tyrosine phosphatase receptor sigma (PTPRS) regulates cellular signals involved in hematopoietic stem cell development, synaptic plasticity, and synovium differentiation. The soluble extracellular Ig-like domains of PTPRS have therapeutic potential by binding to a ligand, inhibiting the ligand-binding of endogenous PTPRS. However, the wild-type Ig-like domains have poor solubility, which limits their therapeutic use. In this study, we identified solvent-exposed hydrophobic residues on the surface of PTPRS and mutated the residues to hydrophilic residues for solubility-enhancing engineering. The mutagenesis screening increased its solubility up to five-fold. In addition, the expression yields were also increased by up to 14-fold. The biochemical and functional analysis of the engineered PTPRS showed that the mutant protein had comparable properties to the wild type. Thus, the engineered PTPRS has potential for therapeutic applications where modulation of PTPRS is critical.