Fibronectin synthesis by human tubular epithelial cells in culture: effects of PDGF and TGF-beta on synthesis and splicing.
BACKGROUND
Enhanced synthesis of extracellular matrix proteins including fibronectin (FN) is associated with the development of sclerosis. In this context we studied FN synthesis by tubular epithelial cells in response to transforming growth factor-beta (TGF-beta) and platelet-derived growth factor (PDGF).


METHODS
FN protein synthesis by human tubular epithelial cells in culture (TEC) was measured by biosynthetic labeling and ELISA. Splicing of FN was assessed by RT-PCR and by Northern blotting.


RESULTS
Cultivated TEC synthesized and released FN, the majority of which was deposited as an unsoluble protein and a minor portion (10 to 15%) was released into the supernatant. TGF-beta and, to a lesser degree, PDGF, up-regulated FN synthesis. All three FN splice variants (EDA, EDB, and IIICS) were produced. PDGF did not influence the splicing. TGF-beta preferentially up-regulated the EDA splice variant, but had no effect on the splicing of the other domains.


CONCLUSIONS
PDGF and TGF-beta both up-regulate FN synthesis of TEC. TGF-beta, but not PDGF, also changed the quality of the de novo synthesized FN, and thus has a different role in the development of sclerosis.
Institut für Immunologie, Medzinische Klinik, Universität Heidelberg, Germany.
A
A
Bürger
C
C
Wagner
C
C
Viedt
B
B
Reis
F
F
Hug
G M
GM
Hänsch
D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism; D005353:Fibronectins / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D007684:Kidney Tubules / Q000166:cytology / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D012326:RNA Splicing; D012333:RNA, Messenger / Q000032:analysis; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D005353:Fibronectins; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta