Attenuation of very late antigen-5-mediated adhesion of bone marrow-derived mast cells to fibronectin by peptides with inverted hydropathy to EF-hands

Release of allergic mediators from mast cells is enhanced by very late Ag ( VLA)-5-mediated interaction of these cells with fibronectin, In this report , we show that VLA-5-mediated adhesion of bone marrow-derived mast cells to fibronectin can be induced by two different pathways: first, Fc epsilon RI clustering, which depends on calmodulin activation and extracellular Ca2+, and, second, by Mn2+ stimulation, which is independent of calmodulin activ ation and antagonized by Ca2+. Previous studies have shown the presence of several cation-binding domains in VLA-5 that are homologous to the calcium- binding EF-hands of calmodulin. To show a role for EF-hands of different pr oteins in VLA-5-mediated adhesion, we used calcium-like peptides (CALP), CA LP1 and CALP2, designed to bind to EF-hands based on inverted hydropathy, C ALP1 and, more potently, CALP2 inhibited Fc epsilon RI-induced adhesion to fibronectin via different mechanisms. The target for the effects of CALP1 a nd 2 on Fc epsilon RI-induced adhesion and degranulation was intracellular and likely involved calmodulin, Interestingly only CALP2 was able to inhibi t Mn2+-induced calmodulin-independent adhesion by interfering with an extra cellular target, which is probably VLA-5. We conclude that CALP1 and 2 can inhibit VLA-5-mediated adhesion of mast cells to fibronectin through bindin g to EF-hands of multiple proteins, and that these peptides can be used as lead compounds for the development of future therapy against allergy.