UC San Diego

It was previously shown by the Bottini Lab that PTP4A1 promotes TGFβ signaling and fibrosis in Systemic Sclerosis (SSc) via its interaction with SRC kinase (1). This thesis aims at further characterizing this interaction and looking for any factors potentially affecting it. Recombinant proteins were purified from Escherichia coli. Two in vitro co-precipitation assays were established and optimized to look at the interaction reliably and reproducibly, and the effect of various factors was examined with the assistance of the Surface Plasmon Resonance (SPR) assay. The characterization led us to propose an interaction mechanism between PTP4A1 and SRC which results in the enhancement of the pro-fibrotic signaling triggered by TGFβ. The relevance of the interaction was also confirmed in SSc dermal fibroblasts and mouse tissue using Proximity Ligation Assay (PLA) performed by other Bottini lab members. Together, these data further demonstrate the critical role of the PTP4A1/SRC interaction in SSc and indicate that PTP4A1 might serve as a therapeutic target.