Regulation of proteins in the VLA cell substrate adhesion family: influence of cell growth conditions on VLA-1, VLA-2, and VLA-3 expression.
Cell quiescence resulting from culture of normal human fibroblasts in low serum (0.5%) was associated with a subsequent gradual increase in the expression of the cell-surface glycoprotein VLA-1, and a corresponding decrease in the expression of extracellular matrix adhesion receptors VLA-2 and VLA-3. Quantitation using either flow cytometry or immunoprecipitation showed that both the VLA-1/VLA-2 and VLA-1/VLA-3 ratios increased 10- to 28-fold and were still rising when cells remained quiescent for 20-30 days. Although induced by cell quiescence, changes in the levels of VLA-1, VLA-2, and VLA-3 continued to occur well after cell proliferation had stopped and thus do not directly correlate with cell cycle transition events. Despite prolonged serum deprivation resulting in elevated VLA-1/VLA-2 and VLA-1/VLA-3 ratios, growth-arrested cells remained viable and were fully capable of proliferating when restimulated. The increases in VLA-1/VLA-2 and VLA-1/VLA-3 ratios observed on quiescent cells were readily reversible, since after restimulation with 10% serum, these ratios quickly returned within 1-2 days to a level near that found on normal exponentially grown cells. Elevation of VLA-1/VLA-2 and VLA-1/VLA-3 ratios is generally associated with quiescence and is not due just to serum deprivation since density arrest of cells at confluence had similar effects on these ratios.
Fingerman
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Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
Hemler
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D000943:Antigens, Differentiation / Q000235:genetics*; D001769:Blood; D002460:Cell Line; D002470:Cell Survival; D004247:DNA / Q000096:biosynthesis; D005347:Fibroblasts / Q000166:cytology* / Q000276:immunology; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D007163:Immunosorbent Techniques; D007399:Interphase; D007700:Kinetics; D016029:Receptors, Very Late Antigen; D014357:Trypsin / Q000494:pharmacology
D000943:Antigens, Differentiation; D016029:Receptors, Very Late Antigen; D004247:DNA; D014357:Trypsin