Inactivation of protein-tyrosine phosphatases as mechanism of UV-induced signal transduction.
UV irradiation of cells causes ligand-independent activation of receptor tyrosine kinases. On the basis of dephosphorylation kinetics, UV-induced inactivation of receptor-directed tyrosine phosphatases (PTP) has been proposed as the mechanism of receptor activation (Knebel, A., Rahmsdorf, H. J., Ullrich, A., and Herrlich, P. (1996) EMBO J. 15, 5314-5325). Here we show that four defined protein-tyrosine phosphatases (PTPs), SHP-1, RPTPalpha, RPTPsigma, and DEP-1, are partially inactivated upon UV irradiation of PTP-overexpressing cells. The dephosphorylation of coexpressed platelet-derived growth factor beta (PDGFbeta) receptor by RPTPalpha is inhibited upon UV irradiation. UV converts RPTPalpha into a substrate-trapping enzyme which can coprecipitate PDGFbeta receptor, similarly to the PTP mutant at the active-center cysteine: C433S. In agreement with the proposed mechanism that inactivation of PTPs accounts for receptor tyrosine kinase activation, no evidence for a UV-induced receptor cross-linking could be obtained in PDGFbeta receptor-enriched membrane micelle preparations and in PDGFbeta receptor overexpressing 293 cells. The intrinsic activity of PDGFbeta receptor kinase was required for the UV-induced enhancement of receptor phosphorylation, but was not changed upon UV irradiation. The data support a mechanism of UV-induced signal transduction involving inactivation of PTPs through an unknown reactive intermediate that oxidizes the conserved cysteine in the active sites of PTPs.
Gross
S
S
Research Unit "Molecular Cell Biology," Klinikum der Friedrich Schiller Universität Jena, Drackendorfer Strasse 1, D-07747 Jena, Germany.
Knebel
A
A
Tenev
T
T
Neininger
A
A
Gaestel
M
M
Herrlich
P
P
Böhmer
F D
FD
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D006801:Humans; D051379:Mice; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015398:Signal Transduction / Q000528:radiation effects*; D013379:Substrate Specificity; D014466:Ultraviolet Rays
D017931:DNA Primers; D017027:Protein Tyrosine Phosphatases