Role of proteoglycans and cytoskeleton in the effects of TGF-beta 1 on renal proximal tubule cells

Kidney Int. 1993 Mar;43(3):575-84. doi: 10.1038/ki.1993.85.


Transforming growth factor-beta (TGF-beta) is a critical cell regulatory protein which influences cell growth, cell differentiation and cell chemotaxis. TGF-beta 1 has been previously shown to promote a migratory and adherent transformation of monolayers of renal proximal tubule cells in primary culture to form solid clusters of cells. To better understand the cellular basis of this TGF-beta 1 effect, these studies evaluated the influence of TGF-beta 1 on the synthesis of proteoglycans and on cytoskeleton rearrangement in rabbit renal proximal tubule cells in primary culture, and their role in this transformation effect of TGF-beta 1. Biosynthetic labeling of proteoglycans with 35S sulfate and enzyme digestion studies demonstrated that TGF-beta 1 promoted the synthesis of heparan sulfate proteoglycans in these cells. The importance of proteoglycan synthesis induced by TGF-beta 1 in this migration and aggregation process was demonstrated with the use of two chemically-dissimilar proteoglycan synthesis inhibitors: xyloside and galactosamine. Both compounds inhibited TGF-beta 1 stimulation of proteoglycan synthesis and diminished TGF-beta 1 promoted transformation of proximal tubule cells as assessed by quantitative morphometry. Further experiments evaluated the influence of TGF-beta 1 on actin microfilaments with the use of rhodamine conjugated phalloidin staining and immunofluorescent microscopy, and demonstrated that TGF-beta 1 provoked a dramatic rearrangement of actin microfilaments into stress fibers. The use of actin microfilament disrupting agents, cytochalasin B and D, attenuated the stress fiber formation promoted by TGF-beta 1 and inhibited the TGF-beta 1-induced morphologic transformation of these cells. Further studies evaluated these effects on the rate of DNA synthesis in these cells, as assessed with 3H-thymidine incorporation. Proteoglycan synthesis inhibitors significantly diminished the maximal proliferative response of these epithelial cells to epidermal growth factor (EGF). In contrast, actin microfilament disaggregation with cytochalasin B or D did not change the rate of DNA synthesis in response to EGF but did attenuate the antiproliferative effect of TGF-beta 1 on EGF-induced DNA synthesis cells. These studies demonstrate that the TGF-beta 1 promoted synthesis cells. These studies demonstrate that the TGF-beta 1 promoted an increase in the production of proteoglycans and a higher ordered structure of the cytoskeleton. Both effects were instrumental in the adhesive migratory response of proximal tubule cells to TGF-beta 1 as well as the DNA synthesis rate response to both EGF and TGF-beta 1.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / metabolism
  • Animals
  • Cells, Cultured
  • Cytochalasin B / pharmacology
  • Cytoskeleton / metabolism*
  • DNA / biosynthesis
  • Fibronectins / biosynthesis
  • Glycosides / pharmacology
  • Kidney Tubules, Proximal / drug effects*
  • Kidney Tubules, Proximal / metabolism
  • Kidney Tubules, Proximal / ultrastructure
  • Phenotype
  • Proteoglycans / biosynthesis*
  • Rabbits
  • Transforming Growth Factor beta / pharmacology*


  • Actins
  • Fibronectins
  • Glycosides
  • Proteoglycans
  • Transforming Growth Factor beta
  • xylosides
  • Cytochalasin B
  • DNA