In vitro and in vivo evidence for shear-induced activation of latent transforming growth factor-beta1.
Transforming growth factor-beta1 (TGF-beta1) has potent physiologic and pathologic effects on a variety of cell types at subnanomolar concentrations. Platelets contain 40 times as much TGF-beta1 as other cells and secrete it as an inactive (latent) form in complex with latency-associated peptide (LAP), which is disulfide bonded via Cys33 to latent TGF-beta binding protein 1 (LTBP-1). Little is known about how latent TGF-beta1 becomes activated in vivo. Here we show that TGF-beta1 released from platelets or fibroblasts undergoes dramatic activation when subjected to stirring or shear forces, providing a potential mechanism for physiologic control. Thiol-disulfide exchange appears to contribute to the process based on the effects of thiol-reactive reagents and differences in thiol labeling of TGF-beta1 before and after stirring or shear. Activation required the presence of LTBP, as TGF-beta1 contained in complex with only LAP could not be activated by stirring when studied as either a recombinant purified protein complex or in the platelet releasates or sera of mice engineered to contain an LAP C33S mutation. Release and activation of latent TGF-beta1 in vivo was demonstrated in a mouse model 5 minutes after thrombus formation. These data potentially provide a novel mechanism for in vivo activation of TGF-beta1.
Laboratory of Blood and Vascular Biology, The Rockefeller University, New York, NY 10065, USA. jahamed@rockefeller.edu
Jasimuddin
J
Ahamed
Nathalie
N
Burg
Keiji
K
Yoshinaga
Christin A
CA
Janczak
Daniel B
DB
Rifkin
Barry S
BS
Coller
D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D001792:Blood Platelets / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism; D002341:Carotid Artery Thrombosis / Q000097:blood; D002460:Cell Line; D017077:Culture Media, Conditioned; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D053779:Latent TGF-beta Binding Proteins / Q000097:blood; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D013314:Stress, Mechanical; D013438:Sulfhydryl Compounds / Q000097:blood; D053773:Transforming Growth Factor beta1 / Q000097:blood* / Q000235:genetics / Q000378:metabolism
D001798:Blood Proteins; D017077:Culture Media, Conditioned; C509032:LTBP1 protein, human; D053779:Latent TGF-beta Binding Proteins; D013438:Sulfhydryl Compounds; D053773:Transforming Growth Factor beta1