Intracellular enzymatic reducing systems control receptor tyrosine kinase signaling via PTP1B.

Protein tyrosine phosphatases (PTPs) counteract receptor tyrosine kinase (RTK) signaling. Inhibition of PTPs by oxidation can be reversed by cytosolic thioredoxin (TXN), but less is known about regulation of PTPs by glutathione (GSH)-driven glutaredoxins (GLRXs). Here, we thus assessed GLRX1, GLRX2, and/or TXN1 in regulation of CO(2)/bicarbonate- and H(2)O(2)-mediated oxidation of the physiologically important PTP1B. GLRXs and TXN1 synergistically maintained PTP1B activity, and modulating cellular levels of either GLRX1, GLRX2, or TXN1 gave strong effects on phosphorylation cascades triggered by epidermal growth factor (EGF) or platelet-derived growth factor (PDGF). Furthermore, transient intracellular interactions of PTP1B with GLRX1, GLRX2, and TXN1 were discovered within minutes after stimuli with either PDGF or EGF, coinciding with control of the corresponding RTK-driven phosphorylation cascades. We conclude that TXN1 and GLRXs are key regulators of PTP1B activity and thus control cellular responses to RTK stimulation.