Shape-dependent regulation of cytoskeletal protein synthesis in anchorage-dependent and anchorage-independent cells

Abstract

We examine changes in protein synthesis that accompany suspension (i.e. shape alteration) of anchorage-dependent and anchorage-independent cells using a newly developed cell fractionation procedure based on detergent extraction. Using this procedure, a cell can be divided into four distinct and independent fractions: soluble, cytoskeleton, chromatin and nuclear matrix-intermediate filament. This fractionation procedure is used to investigate protein synthetic events associated with the release from anchorage-dependent growth, characteristic of transformed cells. Suspension results in several unexpected events in both anchorage-dependent (3T3) cells and anchorage-independent (SVPy 3T3) cells. Suspension of 3T3 cells results in a reduction of total protein synthesis; however, two proteins are enhanced in their amount of synthesis. Suspension of SVPy 3T3 results in about 20 proteins proceeding through short and long-term alterations in the rate of synthesis. The synthesis of some of these proteins is inhibited, others undergo a transient decrease in synthesis upon suspension and then increase above their rate in the anchored state, while the synthesis of others steadily increases after suspension. Suspension of anchorage-dependent cells results in a fraction specific shift in the rates of protein synthesis. Possible roles for these fraction-specific proteins are considered.