Activation of human platelets by mastoparan

Wheeler‐Jones, Caroline P.D.; Særmark, T.; Kakkar, Vijay V.; Authi, Kalwant S.

doi:10.1042/bst019114s

Cited by 3 publications

(1 citation statement)

References 5 publications

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“…Mastoparan forms an amphiphilic α‐helix, and its carboxyl terminus is amidated. Mastoparan is a potent stimulator of exocytosis from diverse mammalian cells such as β‐cells, platelets, neutrophils, and pneumocytes [34–40]. For the release of histamine from mast cells, mastoparan interacts directly with G protein and receptor‐independently induces exocytosis, whereas no direct evidence has yet been reported that mastoparan enters the intracellular space through the lipid bilayer membrane [41,42].…”

Section: Discussionmentioning

confidence: 99%

An antimicrobial peptide tachyplesin acts as a secondary secretagogue and amplifies lipopolysaccharide‐induced hemocyte exocytosis

Ozaki¹,

Ariki²,

Kawabata

2005

The FEBS Journal

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In the horseshoe crab, bacterial lipopolysaccharide (LPS) induces exocytosis by granular hemocytes, resulting in the secretion of various defense molecules, such as lectins and antimicrobial peptides, via a G protein‐mediating signaling pathway. This response is a key component of the horseshoe crab innate immune response against infectious microorganisms. Here, we report an endogenous amplification mechanism for LPS‐induced hemocytes exocytosis. The concentration of LPS required for maximal secretion decreased in proportion to the density of hemocytes, suggesting the presence of a positive feedback mechanism for secretion via a mediator secreted from hemocytes. The exocytosed fluid of hemocytes was found able to induce hemocyte exocytosis in the absence of LPS. Furthermore, tachyplesin, a major antimicrobial peptide of hemocytes, was able to trigger exocytosis in an LPS‐independent manner, which was inhibited by a phospholipase C inhibitor, U‐73122, and a G protein inhibitor, pertussis toxin. Surface plasmon resonance analysis showed that tachyplesin directly interacts with bovine G protein. These findings suggest that the tachyplesin‐induced hemocyte exocytosis also occurs via a G protein‐mediating signaling pathway. We concluded that tachyplesin functions not only as an antimicrobial substance, but also as a secondary secretagogue of LPS‐induced hemocyte exocytosis, leading to the amplification of the innate immune reaction at sites of injury.

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Section: Discussionmentioning

confidence: 99%

An antimicrobial peptide tachyplesin acts as a secondary secretagogue and amplifies lipopolysaccharide‐induced hemocyte exocytosis

Ozaki¹,

Ariki²,

Kawabata

2005

The FEBS Journal

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A phospholipase A1 platelet activator from the wasp venom of Vespa magnifica (Smith)

Yang

et al. 2008

Toxicon

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The Heterotrimeric G-protein Gi Is Localized to the Insulin Secretory Granules of β-Cells and Is Involved in Insulin Exocytosis

Konrad

Young

Record

et al. 1995

Journal of Biological Chemistry

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Mastoparan, a tetradecapeptide found in wasp venom that stimulates G-proteins, increases insulin secretion from beta-cells. In this study, we have examined the role of heterotrimeric G-proteins in mastoparan-induced insulin secretion from the insulin-secreting beta-cell line beta-TC3. Mastoparan stimulated insulin secretion in a dose-dependent manner from digitonin-permeabilized beta-TC3 cells. Active mastoparan analogues mastoparan 7, mastoparan 8, and mastoparan X also stimulated secretion. Mastoparan 17, an inactive analogue of mastoparan, did not increase insulin secretion from permeabilized beta-TC3 cells. Mastoparan-induced insulin secretion from permeabilized beta-TC3 cells was inhibited by pretreatment of the cells with pertussis toxin, suggesting that mastoparan-induced insulin secretion is mediated through a pertussis toxin-sensitive G-protein present distally in exocytosis. Enriched insulin secretory granules (ISG) were prepared by sucrose/nycodenz ultracentrifugation. Western immunoblotting performed on beta-TC3 homogenate and ISG demonstrated that G alpha i was dramatically enriched in ISG. Levels of G alpha o and G alpha q were comparable in homogenate and ISG. Mastoparan stimulated ISG GTPase activity in a pertussis toxin-sensitive manner. Mastoparan 7 and mastoparan 8 also stimulated GTPase activity in the ISG, while the inactive analogue mastoparan 17 had no effect. Selective localization of G alpha i to ISG was confirmed with electron microscopic immunocytochemistry in beta-TC3 cells and beta-cells from rat pancreas. In contrast to G alpha o and G alpha q, G alpha was clearly localized to the ISG. Together, these data suggest that mastoparan may act through the heterotrimeric G-protein G alpha i located in the ISG of beta-cells to stimulate insulin secretion.

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Activation of human platelets by mastoparan

Cited by 3 publications

References 5 publications

An antimicrobial peptide tachyplesin acts as a secondary secretagogue and amplifies lipopolysaccharide‐induced hemocyte exocytosis

An antimicrobial peptide tachyplesin acts as a secondary secretagogue and amplifies lipopolysaccharide‐induced hemocyte exocytosis

A phospholipase A1 platelet activator from the wasp venom of Vespa magnifica (Smith)

The Heterotrimeric G-protein Gi Is Localized to the Insulin Secretory Granules of β-Cells and Is Involved in Insulin Exocytosis

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