Conformation-Sensing Antibodies Stabilize the Oxidized Form of PTP1B and Inhibit Its Phosphatase Activity

SummaryProtein tyrosine phosphatase 1B (PTP1B) plays important roles in downregulation of insulin and leptin signaling and is an established therapeutic target for diabetes and obesity. PTP1B is regulated by reactive oxygen species (ROS) produced in response to various stimuli, including insulin. The reversibly oxidized form of the enzyme (PTP1B-OX) is inactive and undergoes profound conformational changes at the active site. We generated conformation-sensor antibodies, in the form of single-chain variable fragments (scFvs), that stabilize PTP1B-OX and thereby inhibit its phosphatase function. Expression of conformation-sensor scFvs as intracellular antibodies (intrabodies) enhanced insulin-induced tyrosyl phosphorylation of the β subunit of the insulin receptor and its substrate IRS-1 and increased insulin-induced phosphorylation of PKB/AKT. Our data suggest that stabilization of the oxidized, inactive form of PTP1B with appropriate therapeutic molecules may offer a paradigm for phosphatase drug development.

Graphical AbstractFigure optionsDownload full-size imageDownload high-quality image (354 K)Download as PowerPoint slideHighlights► Conformation-sensing antibodies recognize oxidized PTP1B (PTP1B-OX) ► The antibodies stabilize the oxidized, inactive phosphatase and inhibit reactivation ► PTP1B oxidation to the cyclic sulfenyl-amide species occurs in vivo and is reversible ► Intracellular PTP1B-OX antibodies enhance insulin signaling in an ROS-dependent manner