Thymosin beta 4 and its N-terminal tetrapeptide, AcSDKP, inhibit proliferation, and induce dysplastic, non-apoptotic nuclei and degranulation of mast cells.
Thymosin beta4 (Tbeta4), a 5 kDa polypeptide, is a member of the beta-thymosin family. It acts as the principal intracellular G-actin sequestering peptide and exhibits extracellular functions in angiogenesis and wound healing. The N-terminus of Tbeta4 contains a bioactive tetrapeptide, acSDKP, a negative regulator of hematopoietic stem-cell proliferation. Here, we show that both peptides inhibit mast-cell proliferation over the concentration range of 10(-6) to 10(-17) M with the maximum effect of both at 10(-14) M. Both Tbeta4 and acSDKP caused dysplastic mast-cell nuclei that were confirmed by DAPI fluorescent staining. Flow-cytometric analysis of ploidy revealed that the dysplastic nuclei were not multinucleated, but fragmented nuclei in G2 growth arrest. We could further demonstrate that 10(-8) or 10(-14) M Tbeta4 or acSDKP induce mast-cell degranulation. A concentration of 10(-8) M Tbeta4 or acSDKP caused 57 or 89% degranulation, respectively. A number of tryptic fragments of Tbeta4 were assayed beside intact Tbeta4 and the tetrapeptide, and found to be inactive.
Leeanansaksiri
Wilairat
W
Department of Microbiology and Immunology, Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia, USA.
DeSimone
Shirley K
SK
Huff
Thomas
T
Hannappel
Ewald
E
Huff
Thomas F
TF
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001854:Bone Marrow Cells / Q000166:cytology / Q000502:physiology; D015550:Cell Degranulation / Q000502:physiology*; D002467:Cell Nucleus / Q000502:physiology*; D049109:Cell Proliferation; D002478:Cells, Cultured; D006131:Growth Inhibitors / Q000737:chemistry / Q000502:physiology*; D008407:Mast Cells / Q000166:cytology* / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009842:Oligopeptides / Q000737:chemistry / Q000502:physiology*; D010446:Peptide Fragments / Q000737:chemistry / Q000502:physiology; D013947:Thymosin / Q000737:chemistry / Q000502:physiology*; D000099201:Thymosin beta(4)
D006131:Growth Inhibitors; D009842:Oligopeptides; D010446:Peptide Fragments; D013947:Thymosin; D000099201:Thymosin beta(4); C058504:goralatide