Regulation of thrombin-induced stress fibre formation in Swiss 3T3 cells by the 70-kDa S6 kinase.
The signal transduction systems that mediate growth factor receptor-induced cellular shape change have not been fully elucidated, but are known to involve alterations in the state of actin filaments, termed stress fibres. It now appears from several studies that the GTP-binding protein, Rho, is involved. However, the mechanisms by which Rho is activated, and what effectors Rho in turn stimulates are largely matters of conjecture. The present work shows that thrombin is an effective stimulant of stress fibre formation in Swiss 3T3 cells. In addition, we show the 70 kDa form of S6 kinase (p70s6k) to colocalise with stress fibres in both unstimulated and thrombin-activated cells. Coincident with the thrombin-induced formation of stress fibres is the elevated association p70s6k with the fibres. Pretreatment of cells with rapamycin, to inhibit p70s6k activation, inhibits thrombin-induced stress fibre formation and the associated presence of p70s6k on the fibres, supporting a role for p70s6k in thrombin-stimulated stress fibre formation. Thrombin is also shown to stimulate p70s6k activity and that this is inhibited by rapamycin. Thus, the data presented show that thrombin activates stress fibre formation through stimulation of p70s6k via a non-Gi pathway.
Crouch
M F
MF
Molecular Signalling Group, John Curtin School of Medical Research, Australian National University, Canberra, ACT. michael.crouch@anu.edu.au
D016475:3T3 Cells; D000199:Actins / Q000096:biosynthesis*; D000818:Animals; D005455:Fluorescent Antibody Technique; D019204:GTP-Binding Proteins / Q000378:metabolism; D051379:Mice; D011090:Polyenes / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D019893:Ribosomal Protein S6 Kinases; D020123:Sirolimus; D013917:Thrombin / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D000199:Actins; D011090:Polyenes; D010566:Virulence Factors, Bordetella; D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; D013917:Thrombin; D019204:GTP-Binding Proteins; D020123:Sirolimus