Inactivation of active and latent transforming growth factor beta by free thiols: potential redox regulation of biological action.
Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine with important roles in inflammation, wound repair, and cancer. Cells secrete TGF-beta as a latent protein complex, consisting of disulfide-bonded homodimers of growth factor and latency-associated propeptide. Latency regulates extracellular TGF-beta action by controlling the levels of active growth factor available. We report here that active and latent TGF-beta were inactivated in vitro by reduction of the growth factor dimer under physiological conditions. We also demonstrate that the latency-associated propeptide has chaperone-like activity and partially protects TGF-beta from inactivation. TGF-beta inactivation occurred upon incubation with the physiological redox agents, cysteine, homocysteine, and reduced glutathione. Inactivation was temperature- and dose-dependent. While inactivation by physiological concentrations of redox agents was partial at 37 degrees C, active and latent TGF-beta were completely inactivated by raising the temperature in the presence of the redox agents. The mechanism of TGF-beta inactivation involved the generation of biologically inactive growth factor monomer and required the presence of free thiol groups, since thiol blockers protected TGF-beta from reduction. We conclude that non-enzymatic redox reactions may be involved in the regulation of extracellular TGF-beta activity. This might be of particular relevance in wound repair (e.g. in burns), as a mechanism protecting from excess TGF-beta activity, as well as in conditions involving redox dysregulation, such as reperfusion injury of the heart, Alzheimer's disease, and cancer.
Department of Cancer Research, Fachklinik Hornheide, D-48157 Münster, Germany. robert.blakytny@uni-ulm.de
Robert
R
Blakytny
Lars J
LJ
Erkell
Georg
G
Brunner
D001414:Bacitracin / Q000494:pharmacology; D015153:Blotting, Western; D003545:Cysteine / Q000378:metabolism / Q000494:pharmacology; D019281:Dimerization; D004229:Dithiothreitol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000378:metabolism / Q000494:pharmacology; D006710:Homocysteine / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D010084:Oxidation-Reduction / Q000187:drug effects; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism / Q000494:pharmacology*; D013696:Temperature; D016212:Transforming Growth Factor beta / Q000737:chemistry / Q000378:metabolism*
D011994:Recombinant Proteins; D013438:Sulfhydryl Compounds; D016212:Transforming Growth Factor beta; D006710:Homocysteine; D001414:Bacitracin; D005978:Glutathione; D003545:Cysteine; D004229:Dithiothreitol