Immunocytochemical localization of latent transforming growth factor-beta1 activation by stimulated macrophages.
Transforming growth factor-beta1 (TGF-beta) is secreted in a latent form consisting of mature TGF-beta noncovalently associated with its amino-terminal propeptide, which is called latency associated peptide (LAP). Biological activity depends upon the release of TGF-beta from the latent complex following extracellular activation, which appears to be the key regulatory mechanism controlling TGF-beta action. We have identified two events associated with latent TGF-beta (LTGF-beta) activation in vivo: increased immunoreactivity of certain antibodies that specifically detect TGF-beta concomitant with decreased immunoreactivity of antibodies to LAP. Macrophages stimulated in vitro with interferon-gamma and lipopolysaccharide reportedly activate LTGF-beta via cell membrane-bound protease activity. We show through dual immunostaining of paraformaldehyde-fixed macrophages that such physiological TGF-beta activation is accompanied by a loss of LAP immunoreactivity with concomitant revelation of TGF-beta epitopes. The induction of TGF-beta immunoreactivity colocalized with immunoreactive betaglycan/RIII in activated macrophages, suggesting that LTGF-beta activation occurs on the cell surface. Confocal microscopy of metabolically active macrophages incubated with antibodies to TGF-beta and betaglycan/RIII prior to fixation supported the localization of activation to the cell surface. The ability to specifically detect and localize LTGF-beta activation provides an important tool for studies of its regulation.
Chong
H
H
Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley 94720, USA.
Vodovotz
Y
Y
Cox
G W
GW
Barcellos-Hoff
M H
MH
D000818:Animals; D002460:Cell Line; D006801:Humans; D007150:Immunohistochemistry; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D008264:Macrophages / Q000166:cytology / Q000502:physiology*; D051379:Mice; D008907:Mink; D011994:Recombinant Proteins / Q000096:biosynthesis; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D014407:Tumor Cells, Cultured