Signaling mechanism of TGF-beta1-induced collagen contraction mediated by bovine trabecular meshwork cells.
OBJECTIVE
To characterize the intracellular signaling mechanism that underlies the contraction of trabecular meshwork (TM) tissue.


METHODS
The contraction of collagen mediated by bovine TM cells was evaluated by measuring changes in the diameter of collagen gels in which the cells were embedded. Changes in the organization of the actin cytoskeleton were examined by laser-scanning confocal microscopy of cells stained with fluorescent phalloidin. Cell motility was monitored by time-lapse video microscopy.


RESULTS
Transforming growth factor (TGF)-beta1 induced marked TM-cell-mediated contraction of collagen gels in a concentration- and time-dependent manner. Inhibitors of protein kinase C (PKC) blocked this effect of TGF-beta1, whereas an inhibitor of PKA and -G did not. An inhibitor of the small guanosine triphosphatase (GTPase) Rho also inhibited TGF-beta1-induced collagen contraction, whereas an activator of Rho promoted this effect of TGF-beta1. Furthermore, inhibition either of the release of Ca(2+) from internal stores or of the activation of myosin light-chain kinase (MLCK) prevented gel contraction in response to TGF-beta1. The effects of these various agents on TGF-beta1-induced contraction of collagen gels mediated by TM cells were mirrored by their effects on TGF-beta1-induced formation of actin stress fibers, cell spreading (the extension of cellular processes), and cell motility under conditions in which cell contraction was not possible.


CONCLUSIONS
TGF-beta1 induces TM-cell-mediated collagen gel contraction through activation of Rho and the Ca(2+)-dependent enzymes PKC and MLCK. These same signaling molecules contribute to TGF-beta1-induced rearrangement of the actin cytoskeleton, cell spreading, and cell motility.
Nakamura
Yoshikuni
Y
Department of Biomolecular Recognition and Ophthalmology, Yamaguchi University School of Medicine, Ube City, Yamaguchi, Japan.
Hirano
Shinji
S
Suzuki
Katsuyoshi
K
Seki
Keisuke
K
Sagara
Takeshi
T
Nishida
Teruo
T
D000199:Actins / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002465:Cell Movement / Q000502:physiology; D003094:Collagen / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006133:Growth Substances / Q000494:pharmacology; D018613:Microscopy, Confocal; D018715:Microscopy, Video; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013997:Time Factors; D014129:Trabecular Meshwork / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1; D020741:rho GTP-Binding Proteins / Q000378:metabolism
D000199:Actins; D004791:Enzyme Inhibitors; D006133:Growth Substances; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D003094:Collagen; D011493:Protein Kinase C; D009219:Myosin-Light-Chain Kinase; D020741:rho GTP-Binding Proteins