Az elsődleges immunválasz tokképző reakciójának molekuláris genetikai alapjai Drosophila melanogasterben = The molecular basis of the encapsulation reaction in Drosophila melanogaster

A Drosophila melanogaster paraziták elleni tokképző reakcióját vizsgáltuk az immunsejteken általunk korábban definiált molekulák felhasználásával. Azonosítottuk a paraziták petéit tokba záró lamellocitákon kifejeződő fehérjét kódoló atilla gént. Az Atilla fehérje egy glikozilfoszfatidilinozitol horgonyozó hellyel rendelkező transzmembrán molekula, a Ly6 szupercsalád tagja, az első olyan lipid raftokkal asszociált fehérje, mely Drosophila vérsejtjein fejeződik ki. A Drosophila melanogaster genomjában 24 atilla-szerű gént találtunk. Az atilla gén közelében azonosítottuk a minos inszerciót, mely az atilla gén lamellocita specifikus enhanszerét csapdázva egyedi eszközként szolgál a lamellociták in vivo nyomonkövetésében. A lamellocitákon kifejeződő L4 antigénről megállapítottuk, hogy az a myospheroid gén által kódolt bétaPS integrin. Genetikai sejtvonal jelöléssel azt találtuk, hogy a molekulát kifejező sejtek a tokképző reakció során morfológiai változáson mennek át, lamellocitákká alakulásuk közben elveszítik fagocitáló képességüket, alátámasztva a veleszületett immunitás sejtes elemeinek nagyfokú morfológiai és funkcionális plaszticitását. Az L2 molekula a lamellocita sejtvonal irányban véglegesen elkötelezett sejtekben feltehetőleg az aktinnal képez molekula-komplexet. A Drosophila lárva szesszilis vérsejtjeiről megállapítottuk, hogy funkcionálisan egységes szövetet képeznek, melyből származó sejtek szolgálnak a parazita darázs petéje elleni immunválasz elsődleges forrásául. | Our studies focus on the regulation of cell mediated immunity in Drosophila model organism by the aid of the molecular markers -, in particular the lamellocyte specific L1, L4 and L2 molecules - defined by us previously. The atilla gene - encoding for the L1 protein - is expressed by lamellocytes and their precursors, cells, forming multilayer capsules around parasite eggs. The atilla gene product is a glycosylphosphatidylinositol anchored cell-surface protein, a member of the Ly6 superfamily, the first molecule that has been identified as a cell surface molecule associated with lipid rafts in Drosophila blood cells. We found 24 atilla-like genes in the genome, organized in four clusters. A minos insertion discovered in the neighbourhood of the atilla gene is suitable for in vivo detection of lamellocytes. The L4 protein is an integrin betaPS encoded by the Drosophila myospheroid gene. Our genetic lineage tracing experiments showed that hemocytes expressing L4 undergo marked morphological and functional changes, the observation, that revealed the morphological and functional plasticity of cellular components of the innate immune system in Drosophila. The L2 molecule most likely forms a molecular-complex with actin at the terminal stage of lamellocyte differentiation. These molecular markers also helped us to define the sessile hemocytes as a functional hematopoietic compartment serving as the main source of lamellocytes in the course of the cell mediated immune response

Deletion of proteasomal subunit S5a/Rpn10/p54 causes lethality, multiple mitotic defects and overexpression of proteasomal genes in Drosophila melanogaster

The regulatory complex of the 26S proteasome is responsible for the selective recognition and binding of multiubiquitinated proteins. It was earlier shown that the subunit S5a/Rpn10/p54 of the regulatory complex is the only cellular protein capable of binding multiubiquitin chains in an in vitro overlay assay. The role of this subunit in substrate selection, however, is a subject of debate, following the observation that its deletion in Saccharomyces cerevisiae is not lethal and instead causes only a mild phenotype. To study the function of this subunit in higher eukaryotes, a mutant Drosophila strain was constructed by deleting the single copy gene encoding subunit S5a/Rpn10/p54. This deletion caused larval-pupal polyphasic lethality, multiple mitotic defects, the accumulation of higher multimers of ubiquitinated proteins and a huge accumulation of defective 26S proteasome particles. Deletion of the subunit S5a/Rpn10/p54 does not destabilise the regulatory complex and does not disturb the assembly of the regulatory complex and the catalytic core. The pupal lethality is a consequence of the depletion of the maternally provided 26S proteasome during the larval stages and a sudden increase in the proteasomal activity demands during the first few hours of pupal development. The huge accumulation of the fully assembled 26S proteasome in the deletion mutant and the lack of free subunits or partially assembled particles indicate that there is a highly coordinated accumulation of all the subunits of the 26S proteasome. This suggests that in higher eukaryotes, as with yeast, a feedback circuit coordinately regulates the expression of the proteasomal genes, and this adjusts the actual proteasome concentration in the cells according to the temporal and/or spatial proteolytic demand

Cell lineage tracing reveals the plasticity of the hemocyte lineages and of the hematopoietic compartments in Drosophila melanogaster

Much of our knowledge on hematopoiesis, hematopoietic compartments, hematopoietic cell lineages and immunity has been derived from studies on the vertebrate immune system. The sophisticated innate immunity of insects, the phylogenetic conservation and the power of Drosophila genetics allowed the investigation of immune cell (hemocyte) lineage relationships in Drosophila melanogaster. The development of the hemocyte lineages in Drosophila is a result of a precisely regulated succession of intracellular and intercellular events, though the nature and extent of these interactions are not known. We describe here a cell lineage tracing system set up to analyze the development of hemocyte lineages and functionally distinct hemocyte subsets. This system allowed us to distinguish two major embryonic hemocyte lineages, the crq and Dot lineages, in two, physically separated compartments, the embryonic macrophages and the embryonic lymph gland. We followed the fate and development of these lineages in the construction of the larval hematopoietic compartments and during the cell-mediated immune response, the encapsulation reaction. Our results revealed the considerable plasticity and concerted action of the hematopoietic compartments and the hemocyte lineages in the development of the innate immune system and in the course of the cell-mediated immune response in Drosophila

Variation of NimC1 expression in Drosophila stocks and transgenic strains.

The NimC1 molecule has been described as a phagocytosis receptor, and is being used as a marker for professional phagocytes, the plasmatocytes, in Drosophila melanogaster. In studies including tumor-biology, developmental biology, and cell mediated immunity, monoclonal antibodies (P1a and P1b) to the NimC1 antigen are used. As we observed that these antibodies did not react with plasmatocytes of several strains and genetic combinations, a molecular analysis was performed on the structure of the nimC1 gene. In these strains we found 2 deletions and an insertion within the nimC1 gene, which may result in the production of a truncated NimC1 protein. The NimC1 positivity was regained by recombining the mutation with a wild-type allele or by using nimC1 mutant lines under heterozygous conditions. By means of these procedures or using the recombined stock, NimC1 can be used as a marker for phagocytic cells in the majority of the possible genetic backgrounds

Innate immunity

In this review, we discuss how studying the Drosophila immune system contributes to a better understanding of the basic principles of innate immunity. We describe the homologies between the insect and the vertebrate immune-regulatory mechanisms and convergent evolutionary traits of the Drosophila and the vertebrate immune system

A vérsejtképzés és a veleszületett immunitás funkcionális genomikai analízise Drosophilában = Functional genomic analysis of the hematopoiesis and the innate immunity in Drosophila

A Pályázat adta keretek lehetővé tették a Drosophila melanogaster veleszületett immunitásának vizsgálatában kapott korábbi eredményeink értelmezését, valamint a vizsgálatok új irányokba történő kiterjesztését. Meghatároztuk több, korábban vérsejtantigénként jellemzett molekula kódoló génjét. Jellemeztük több, általunk korábban azonosított Drosophila vérsejtantigén funkcióját, azonosítottunk több, az embrióban, a lárvában és a kifejlett rovarban megnyilvánuló vérsejtantigént, és genomszintű genetikai screent kezdtünk "in vivo", melynek segítségével a vérsejtdifferenciálódást szabályozó géneket azonosítottunk. A vérsejtantigének jellemzése, "in vivo" használható genetikai konstruktok létrehozása és a genetikai screen során kapott előzetes eredmények alapján egy eddig nem azonosított immunológiai kompartmentum létét feltételeztük. | The Grant made possible the assessment and the extension of our earlier results and observations on the innate immunity of Drosophila melanogaster. We identified the coding genes for molecules, identified earlier as blood cell antigens in Drosophila, and determined their function and involvement in the regulation of blood cell development. Furthermore, we identified novel markers for embryonic and larval hemocytes and those of the adult Drosophila. We initiated a genome-wide genetic screen 'in vivo' and identified genes regulating blood cell development. Preliminary results obtained in the course of the genetic screen and the development of genetic constructs allowed us to postulate the presence of a so far unidentified 'niche' for blood cell development in Drosophila

Definition of Drosophila hemocyte subsets by cell-type specific antigens.

We analyzed the heterogeneity of Drosophila hemocytes on the basis of the expression of cell-type specific antigens. The antigens characterize distinct subsets which partially overlap with those defined by morphological criteria. On the basis of the expression or the lack of expression of blood cell antigens the following hemocyte populations have been defined: crystal cells, plasmatocytes, lamellocytes and precursor cells. The expression of the antigens and thus the different cell types are developmentally regulated. The hemocytes are arranged in four main compartments: the circulating blood cells, the sessile tissue, the lymph glands and the posterior hematopoietic tissue. Each hemocyte compartment has a specific and characteristic composition of the various cell types. The described markers represent the first successful attempt to define hemocyte lineages by immunological markers in Drosophila and help to define morphologically, functionally, spatially and developmentally distinct subsets of hemocytes

A systems biological view of life-and-death decision with respect to endoplasmic reticulum stress—The role of PERK pathway

Accumulation of misfolded/unfolded proteins in the endoplasmic reticulum (ER) leads to the activation of three branches (Protein kinase (RNA)-like endoplasmic reticulum kinase [PERK], Inositol requiring protein 1 [IRE-1] and Activating trascription factor 6 [ATF6], respectively) of unfolded protein response (UPR). The primary role of UPR is to try to drive back the system to the former or a new homeostatic state by self-eating dependent autophagy, while excessive level of ER stress results in apoptotic cell death. Our study focuses on the role of PERK- and IRE-1-induced arms of UPR in life-or-death decision. Here we confirm that silencing of PERK extends autophagy-dependent survival, whereas the IRE-1-controlled apoptosis inducer is downregulated during ER stress. We also claim that the proper order of surviving and self-killing mechanisms is controlled by a positive feedback loop between PERK and IRE-1 branches. This regulatory network makes possible a smooth, continuous activation of autophagy with respect to ER stress, while the induction of apoptosis is irreversible and switch-like. Using our knowledge of molecular biological techniques and systems biological tools we give a qualitative description about the dynamical behavior of PERK- and IRE-1-controlled life-or-death decision. Our model claims that the two arms of UPR accomplish an altered upregulation of autophagy and apoptosis inducers during ER stress. Since ER stress is tightly connected to aging and age-related degenerative disorders, studying the signaling pathways of UPR and their role in maintaining ER proteostasis have medical importance. © 2017 by the authors; licensee MDPI, Basel, Switzerland