Thymosin beta 4 (Fx peptide) is a potent regulator of actin polymerization in living cells.
Thymosin beta 4 (beta 4) is a 5-kDa polypeptide originally identified in calf thymus. Although numerous activities have been attributed to beta 4, its physiological role remains elusive. Recently, beta 4 was found to bind actin in human platelet extracts and to inhibit actin polymerization in vitro, raising the possibility that it may be a physiological regulator of actin assembly. To examine this potential function, we have increased the cellular beta 4 concentration by microinjecting synthetic beta 4 into living epithelial cells and fibroblasts. The injection induced a diminution of stress fibers and a dose-dependent depolymerization of actin filaments as indicated by quantitative image analysis of phalloidin binding. Our results show that beta 4 is a potent regulator of actin assembly in living cells.
Sanders
M C
MC
Cell Biology Group, Worcester Foundation for Experimental Biology, Shrewsbury, MA 01545.
Goldstein
A L
AL
Wang
Y L
YL
D016475:3T3 Cells; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D007700:Kinetics; D046911:Macromolecular Substances; D051379:Mice; D008845:Microinjections; D008856:Microscopy, Fluorescence; D051381:Rats; D013947:Thymosin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology; D000099201:Thymosin beta(4)
D000199:Actins; D046911:Macromolecular Substances; D013947:Thymosin; D000099201:Thymosin beta(4)