Studies on localization and protein ligands of Galleria mellonella apolipophorin III during immune response against different pathogens.

A lipid-binding protein apolipophorin III (apoLp-III), an exchangeable component of lipophorin particles, is involved in lipid transport and immune response in insects. In Galleria mellonella, apoLp-III binding to high-density lipophorins and formation of low-density lipophorin complexes upon immune challenge was reported. However, an unanswered question remains whether apoLp-III could form different complexes in a pathogen-dependent manner. Here we report on pathogen- and time-dependent alterations in the level of apoLp-III free and lipophorin-bound form that occur in the hemolymph and hemocytes shortly after immunization of G. mellonella larvae with different pathogens, i.e. Gram-negative bacterium Escherichia coli, Gram-positive bacterium Micrococcus luteus, yeast-like fungus Candida albicans, and filamentous fungus Fusarium oxysporum. These changes were accompanied by differently persistent re-localization of apoLp-III in the hemocytes. The apoLp-III-interacting proteins were recovered from immune hemolymph by affinity chromatography on a Sepharose bed with immobilized anti-apoLp-III antibodies. ApoLp-I, apoLp-II, hexamerin, and arylphorin were identified as main components that bound to apoLp-III; the N-terminal amino acid sequences of G. mellonella apoLp-I and apoLp-II were determined for the first time. In the recovered complexes, the pathogen-dependent differences in the content of individual apolipophorins were detected. Apolipophorins may thus be postulated as signaling molecules responding in an immunogen-dependent manner in early steps of G. mellonella immune response.

[Metalloproteases and their inhibitors: role in pathogenesis of selected examples]. / Metaloproteinazy i ich inhibitory: rola w patogenezie na wybranych przykladach.

Proteolytic enzymes and their inhibitors are crucial in host-pathogen interaction. Metalloproteases secreted by pathogenic microbes play an important role in destroying not only host tissues but also their immune proteins. Metalloproteinase inhibitors, in contrast, may serve as effective therapeutic agents, which is especially important because of the increasing number of microorganisms resistant to known antibiotics. The role of metalloproteases produced by the bacterium Pseudomonas aeruginosa in the colonization of the host organism is described. Attention has also been paid to the role of inhibitors of these enzymes in defense responses and underlined their potential role in inhibiting the development of infection.

[Different faces of phenoloxidase in animals]. / Rózne oblicza oksydazy fenolowej u zwierzat.

Phenoloxidases are oxidoreducting enzymes whose main function is the oxidation of phenols. The term phenoloxidase is often used interchangeably to describe three different enzymes: tyrosinase (EC 1.14.18.1), catechol oxidase, and laccase. Of these, only tyrosinase has two activities: (1) oxygenase activity to hydroxylate monophenols to ortho-diphenols and (2) oxidase activity responsible for further oxidation of ortho-diphenols to ortho-quinones. Tyrosinase is a key enzyme involved in the melanogenesis process, resulting in the formation of black-brown eumelanin and yellow-red feomelanin. In addition to the pigmentary role, human melanin protects against harmful ultraviolet radiation, while in invertebrate animals melanin is involved in the process of cuticle hardening, wound healing, clot formation, maintenance of intestinal homeostasis and defense reactions. In invertebrates, the tyrosinase is synthesized as a proenzyme that is activated by a serine proteases' cascade known as the phenoloxidase system. This system is considered as one of the innate immunity mechanisms.