Tyrosine protein kinase expression in long-term quiescent WI-38 cells following growth factor simulation.
We have used the WI-38 cell long-term quiescent model system to study the regulation of cell cycle progression at the molecular level. By modulating the length of time that WI-38 cells are density arrested, it is possible to proportionately alter the length of the prereplicative or G-1 phase which the cell traverses after growth factor stimulation in preparation for entry into DNA synthesis. Stimulation of long- and short-term density arrested WI-38 cells with different growth factors or higher concentrations of individual growth factors does not alter the time required by long-term cells to enter S after stimulation. However, the time during the prereplicative period for which these growth factors are needed is different. Long-term quiescent WI-38 cells require EGF to traverse the G-0/G-1 border but do not need and apparently cannot respond to IGF-1 during the first 10 h after EGF stimulation, the length of the prolongation of the prereplicative phase. This suggests that EGF stimulation of long-term quiescent WI-38 cells initiates a series of molecular events which make these cells "competent" to respond to the "progression" growth factor, IGF-1. In light of the well-established role of protein tyrosine kinases in signal transduction, we set out to identify, clone, and analyze the expression of receptor and non-receptor tyrosine kinases which potentially could play a role during the prolongation of the prereplicative phase in making the long-term quiescent WI-38 cells competent to respond to IGF-1. We obtained 49 clones representing 11 different receptor and non-receptor type protein tyrosine kinases. Analysis of expression of these clones revealed a variety of different patterns of expression. However, the most striking pattern was exhibited by IGF-1 receptor. Our results suggest that induction of IGF-1 receptor mRNA by EGF may be an important event in the establishment of competence by EGF in long-term density arrested WI-38 cells.
Korcz
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Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
Soprano
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DR
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D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D016415:Sequence Alignment
D017931:DNA Primers; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D011505:Protein-Tyrosine Kinases