The small GTPase Rac-1 is a regulator of mesangial cell morphology and thrombospondin-1 expression.
Thrombospondin-1 (TSP-1), which is synthesized by mesangial cells, is known for its anti-angiogenic activity and its ability to activate latent TGF-beta. TSP-1 is upregulated in renal diseases associated with tissue remodeling. Therefore, we hypothesized that the expression of TSP-1 might be modulated by changes in cell morphology involving proteins of the Rho family. Spreading of mesangial cells after detachment and reseeding was characterized by the formation of lamellipodia and focal adhesions, pointing toward a Rac-1-mediated rearrangement of actin structures. Clustering of focal adhesion proteins was also observed in a model system of nocodazole-induced disruption of microtubules. These morphological alterations were impeded by pharmacological inhibition of Src family kinases, of the small GTPase Rac-1, or by downregulation of Rac-1 by siRNA. Upon cell spreading, TSP-1 was upregulated in the absence and much more prominently in the presence of serum, but also after nocodazole treatment. TSP-1 upregulation was controlled by activation of Src family kinases, ERK 1/2 and Rac-1, whereas activation of RhoA-ROCK signaling was not linked to TSP-1 induction. We thus provide evidence that TSP-1 expression is induced by common signaling pathways, which are activated by morphological alterations of renal mesangial cells or by soluble factors as contained in serum, and these pathways include Src family kinases, ERK 1/2 and Rac-1. Our data suggest that tissue remodeling activates gene expression of pathophysiologically relevant proteins such as TSP-1.
Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Ulm, Germany.
Klaudia
K
Giehl
Angela
A
Graness
Margarete
M
Goppelt-Struebe
D000199:Actins / Q000378:metabolism; D000577:Amides / Q000494:pharmacology; D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors; D005419:Flavonoids / Q000494:pharmacology; D022001:Focal Adhesions / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D050527:Mesangial Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D015739:Nocodazole / Q000494:pharmacology; D051419:Paxillin / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D019700:Thrombospondin 1 / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
C509621:4-amino-7-phenylpyrazol(3,4-d)pyrimidine; C412373:AG 1879; D000199:Actins; D000577:Amides; D000634:Aminoquinolines; D005419:Flavonoids; C487513:NSC 23766; D051419:Paxillin; D047428:Protein Kinase Inhibitors; C496063:Pxn protein, rat; D011720:Pyrazoles; D011725:Pyridines; D011743:Pyrimidines; D034741:RNA, Small Interfering; D019700:Thrombospondin 1; C108830:Y 27632; D019061:src-Family Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D020830:rac1 GTP-Binding Protein; D015739:Nocodazole; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one