Synthesis of transforming growth factor-beta 1 by megakaryocytes and its localization to megakaryocyte and platelet alpha-granules.
We have directly demonstrated that megakaryocytes are a major site of synthesis and storage of transforming growth factor-beta 1 (TGF/beta 1) by combined immunohistochemical, immunocytochemical, and in situ hybridization methods. The presence of TGF/beta 1 messenger RNA (mRNA) in mature megakaryocytes in adult rat spleen and bone marrow (BM) was established by in situ hybridization. Localization of TGF/beta 1 protein to intact alpha-granules of megakaryocytes, its putative storage site, was accomplished in glycol-methacrylate embedded porcine BM with an immunoperoxidase technique and light microscopy. The TGF/beta 1 was sequestered in intracytoplasmic granules in a pattern virtually identical to that of another alpha-granule marker protein, fibrinogen. This observation strongly suggests packaging of TGF/beta 1 into this organelle within megakaryocytes. That TGF/beta 1 mRNA was localized to megakaryocytes suggests that the TGF/beta 1 found in the alpha-granules in platelets originates with megakaryocyte synthesis. The alpha-granule localization of TGF/beta 1, as well as fibrinogen, was also demonstrated in isolated platelets at the ultrastructural level by electronmicroscopy (EM) and postembedding colloidal-gold immunocytochemistry, thus directly demonstrating that alpha-granules are the final storage site for TGF/beta 1 in mature platelets.
Fava
R A
RA
Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, TN.
Casey
T T
TT
Wilcox
J
J
Pelton
R W
RW
Moses
H L
HL
Nanney
L B
LB
D000818:Animals; D001792:Blood Platelets / Q000378:metabolism* / Q000648:ultrastructure; D001853:Bone Marrow / Q000378:metabolism / Q000648:ultrastructure; D001854:Bone Marrow Cells; D003594:Cytoplasmic Granules / Q000378:metabolism* / Q000648:ultrastructure; D006018:Glycols; D007106:Immune Sera / Q000276:immunology; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry / Q000379:methods; D008533:Megakaryocytes / Q000378:metabolism* / Q000648:ultrastructure; D008689:Methacrylates; D008854:Microscopy, Electron / Q000379:methods; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D013154:Spleen / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D013552:Swine; D016212:Transforming Growth Factor beta / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology
D006018:Glycols; D007106:Immune Sera; D008689:Methacrylates; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta