Discovery of Mitocryptide-1, a Neutrophil-activating Cryptide from Healthy Porcine Heart

Hidehito Mukai,Yoshinori Hokari,Tetsuo Seki,Toshifumi Takao,Makoto Kubota,Yuko Matsuo,Hiroyuki Tsukagoshi,Masahiko Kato,Hirokazu Kimura,Yasutsugu Shimonishi,Yoshiaki Kiso,Yoshisuke Nishi,Kaori Wakamatsu,Eisuke Munekata

doi:10.1074/jbc.m803913200

Abstract

Although neutrophils are known to migrate in response to various chemokines and complement factors, the substances involved in the early stages of their transmigration and activation have been poorly characterized to date. Here we report the discovery of a peptide isolated from healthy porcine hearts that activated neutrophils. Its primary structure is H-Leu-Ser-Phe-Leu-Ile-Pro-Ala-Gly-Trp-Val-Leu-Ser-His-Leu-Asp-His-Tyr-Lys-Arg-Ser-Ser-Ala-Ala-OH, and it was indicated to originate from mitochondrial cytochrome c oxidase subunit VIII. This peptide caused chemotaxis at concentrations lower than that inducing beta-hexosaminidase release. Such responses were observed in neutrophilic/granulocytic differentiated HL-60 cells but not in undifferentiated cells, and G(i2)-type G proteins were suggested to be involved in the peptide signaling. Moreover the peptide activated human neutrophils to induce beta-hexosaminidase secretion. A number of other amphipathic neutrophil-activating peptides presumably originating from mitochondrial proteins were also found. The present results suggest that neutrophils monitor such amphipathic peptides including the identified peptide as an initiation signal for inflammation at injury sites.

Highlights

Neutrophils are a type of leukocyte involved in the innate defense system
Once tissue injury occurs because of an infection or toxic cell debris resulting from cell necrosis, these cells migrate from the bloodstream to the injury sites
Some of these substances may be present in mitochondria because the contents of disrupted mitochondria, which are thought to be released immediately after necrosis in damaged tissues, promote neutrophilic migration [4]

Summary

Introduction

Neutrophils are a type of leukocyte involved in the innate defense system. Once tissue injury occurs because of an infection or toxic cell debris resulting from cell necrosis, these cells migrate from the bloodstream to the injury sites. Peptides that activated HL-60-derived neutrophilic/granulocytic cells were purified from healthy porcine hearts (outlined in Fig. 1) by monitoring the activity of fractions that induce ␤-hexosaminidase release from the cells.

Results

Conclusion