Thymosin β4 and thymosin β4-derived peptides induce mast cell exocytosis

The peptide thymosin β4 (Tβ4) promotes angiogenesis and wound healing. Mast cells are involved in these processes as well and therefore we investigated the effect of Tβ4 on mast cells. Exposure to 0.2-2000 nM Tβ4 induced mediator release (up to 23%) in murine peritoneal and human HMC-1 mast cells in a concentration-dependent manner. While the peptide AcSDKP, matching the 4 N-terminal amino acid residues of Tβ4, mediated low but detectable mediator release, peptides corresponding to the Tβ4 amino acid sequences 16-38 and 17-23 stimulated mast cells mediator release on a level equal to or higher than that observed with native Tβ4. These observations and certain characteristics of Tβ4-mediated mast cell activation suggest that the actin-binding motif LKKTET present in Tβ4 (amino acid 17-22) might be implicated in this process. Thus, Tβ4 activates mediator release in mast cells by a process that possibly involves an actin-binding motif and this could be important for understanding the mechanisms of Tβ4-mediated effects in vivo.