polistes-mastoparan and mastoparan

Melittin is known to be a major hydrophobic peptide component in honeybee venom that can cause as much elevation of fertilization membrane of sea urchin eggs as normal fertilization. The action of melittin has been thought to be closely related with its ability to facilitate the phospholipase A2 activity on the eggs. However, another peptide "mastoparan" from wasp venom was not found here to cause any elevation of the membrane, although it can activate the enzyme as well as melittin. On the other hand, mastoparan was found to get the membrane-elevating activity only when its amino groups were modified with hydrophobic substituents. N epsilon-Substituted mastoparan with a dansyl group in Lys11 residue was most effective among the analogs examined here. Our findings indicate that the facilitation of phospholipase by the peptides have little relation with the membrane generation. Such hydrophobic moiety as the dansyl group in the peptides must cause the cortical reaction on the eggs in cooperation with peptide moiety. The dansylated peptide will be a useful tool to induce the artificial fertilization of sea urchin eggs.

Topics: Amino Acid Sequence; Animals; Dose-Response Relationship, Drug; Female; Fertilization; In Vitro Techniques; Intercellular Signaling Peptides and Proteins; Melitten; Molecular Sequence Data; Ovum; Peptides; Phospholipases A; Phospholipases A2; Sea Urchins; Structure-Activity Relationship; Wasp Venoms

In differentiated HL-60 cells the amphiphilic peptide mastoparan induces a dose-dependent stimulation of phosphoinositide breakdown with an EC50 value of 9 microM. Such stimulation can be markedly reduced by pretreatment of the cells with pertussis toxin (100 ng/ml, 2 h). In membranes obtained from differentiated HL-60 cells, guanine nucleotides stimulate the formation of IP2 and IP3. Calcium ions also induce phosphoinositide breakdown in this preparation independent of the presence of guanine nucleotides. In HL-60 cell membranes, mastoparan inhibited GTP gamma S-stimulation of phosphoinositide breakdown with an IC50 value of 3 microM. Such inhibitory activity of mastoparan also was present in membranes from cells pretreated with pertussis toxin. Calcium-induced stimulation of phosphoinositide breakdown was not significantly inhibited by mastoparan. The analogs mastoparan-X and polistes mastoparan had similar inhibitory activity, whereas the analog des-Ile1-Asn2-mastoparan was inactive. In permeabilized HL-60 cells mastoparan also inhibited phosphoinositide breakdown. Another amphiphilic peptide, melittin, was inactive in HL-60 intact cells, but similar to mastoparan, inhibited guanine nucleotide-induced phosphoinositide breakdown in HL-60 cell membranes and permeabilized cells. Thus, mastoparan peptides can stimulate phosphoinositide breakdown in intact HL-60 cells, probably through the interaction with a guanine nucleotide binding protein. In permeabilized cells and in cell membranes, mastoparan induces inhibition of guanine nucleotide-mediated phosphoinositide breakdown presumably through an interaction with an intracellular site. The inhibitory action of mastoparan and melittin is probably related to the amphiphilic character of these peptides.

Topics: Cell Membrane; Cell Membrane Permeability; Cell-Free System; Guanine Nucleotides; Humans; Intercellular Signaling Peptides and Proteins; Leukemia, Experimental; Melitten; Peptides; Phosphatidylinositols; Tumor Cells, Cultured; Type C Phospholipases; Wasp Venoms