Lipopeptides are effective stimulators of tyrosine phosphorylation in human myeloid cells

Abstract

Synthetic lipopeptide analogues of the N-terminus of bacterial lipoprotein are effective activators of macrophages neutrophils and lymphocytes. We studied the effect of the lipopeptide N-palmitoyl-S-[2, 3-bis(palmitoyloxy)-(2RS)-propyl]-(R)-cysteinyl-(S)-seryl- (S)-lysyl-(S)-lysyl-(S)-lysyl-(S)-lysine [Pam3Cys-Ser-(Lys)4] on tyrosine phospholylation in dibutyryl-cyclic-AMP-differentiated HL-60 cells using anti-phosphotyrosine antibodies. Pam3Cys-Ser-(Lys)4 concentration-dependently stimulated tyrosine phosphorylation of 100/110 kDa and 60 kDa proteins and, to a lesser extent of 55 kDa and 70/75 kDa proteins. Half-maximal and maximal effects were observed at concentrations of 1-6 and 5-50 μg/ml respectively. The lipopeptide-induced increase in phosphorylation was rapid and transient with a peak response after 30-60 s. The lipopeptide (2S)-2-palmitoylamino-6-palmitoyloxymethyl-7-palmitoyloxyheptanoyl-Ser-(Lys)4 [Pam3Ahh-Ser-(Lys)4] was as potent as Pam3Cys-Ser(Lys)4 whereas (2S,6S)-2-palmitoylamino-6,7-bis(palmitoyloxy)heptanoyl-Ser-(Lys)4] [Pam3Adh-Ser-(Lys)4] and Pam3Cys-Ser-Gly did not induce tyrosine phosphorylation. Lipopeptide-induced tyrosine phosphorylation was not affected by treatment of cells with pertussis toxin. Neither phorbol 12-myristate 13-acetate nor A23187 induced tyrosine phosphorylation in dibutyryl-cyclic-AMP-differentiated HL-60 cells. In HL-60 promyelocytes Pam3Cys-Ser-(Lys)4 had no effect on tyrosine phosphorylation whereas the lipopeptide also induced tyrosine phosphorylation in 1,25-dihydroxyvitamin-D3-differentiated HL-60 cells and in human neutrophils. These results show that lipopeptides are effective stimulators of tyrosine phosphorylation in mature human myeloid cells.