Cell cycle-dependent fluctuation of urokinase-type plasminogen activator, its receptor, and inhibitors in cultured bovine mammary epithelial and myoepithelial cells.
Bovine mammary epithelial (BME-UV1, clone E-T and BME-UV, clone E-T2) and myoepithelial (BMM-UV, clone m-T2) cell lines were used to study the modulation of cell-associated activity of urokinase-type plasminogen activator (u-PA), as well as mRNA transcripts of u-PA, its receptor (u-PAR), and inhibitors (PAI-1 and PAI-2) during the cell cycle. After release from a growth arrest accomplished by growth factor deprivation, the length of the cell cycle was determined as 19-21 h, with G1, S, and G2+M phases of 6-7, 7-9, and 5-6 h respectively. As the cell cycle progressed, accumulated cell-associated u-PA activity increased. Maximal activity occurred at the S/G2 boundary and decreased during the G2/M phases. All cell lines tested produced plasmin-specific inhibitor(s). Accumulation of u-PA mRNA peaked 3 h after stimulation into the growth cycle for m-T2 and E-T and during 3-6 h for E-T2 cells. Maximum levels of u-PAR mRNA were observed at 3 h for the E-T cell line, 6-9 h for E-T2 cells, and 3-9 h for m-T2 cells. The cell cycle distribution of the PAI-1 mRNA was similar to that of u-PA for both epithelial cell lines, while for m-T2 cells maximal accumulation of PAI-1 mRNA was detected at 3-9 h after growth initiation. The increase of PAI-2 mRNA transcription for m-T2 and E-T cells was detected at 3-6 h. The PAI-2 mRNA in E-T2 cells was under detectable levels. The data indicate that the expression of the constituents of the PA system in bovine mammary epithelial and myoepithelial cells is not cell type-dependent but is tightly connected to the phase of the cell cycle.
Zavizion
B
B
Department of Animal and Food Sciences, University of Vermont, Burlington, VT 05405, USA. bzavizio@zoo.uvm.edu
White
J H
JH
Bramley
A J
AJ
D000818:Animals; D002417:Cattle; D002453:Cell Cycle / Q000502:physiology*; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D008321:Mammary Glands, Animal / Q000166:cytology / Q000378:metabolism*; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism*; D010958:Plasminogen / Q000378:metabolism; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D017396:Plasminogen Activator Inhibitor 2 / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D055293:Receptors, Urokinase Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
D017395:Plasminogen Activator Inhibitor 1; D017396:Plasminogen Activator Inhibitor 2; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D010958:Plasminogen; D014568:Urokinase-Type Plasminogen Activator