ABSTRACT
The polynucleate myotubes of vertebrates and invertebrates form by fusion of myoblasts. We report the involvement of the Drosophila melanogaster Roughest (Rst) protein as a new membrane-spanning component in this process. Rst is strongly expressed in mesodermal tissues during embryogenesis, but rst null mutants display only subtle embryonic phenotypes. Evidence is presented that this is due to functional redundancy between Rst and its paralogue Kirre. Both are highly related single-pass transmembrane proteins with five extracellular immunoglobulin domains and three conserved motifs in the intracellular domain. The expression patterns of kirre and rst overlap during embryonic development in muscle founder cells. Simultaneous deletion of both genes causes an almost complete failure of fusion between muscle founder cells and fusion-competent myoblasts. This defect can be rescued by one copy of either gene. Moreover, Rst, like Kirre is a myoblast attractant.
Subject(s)
Cell Adhesion Molecules, Neuronal/genetics , Drosophila Proteins , Drosophila melanogaster/embryology , Eye Proteins , Gene Expression Regulation, Developmental , Insect Proteins/genetics , Membrane Proteins , Muscle Proteins , Muscle, Skeletal/embryology , Amino Acid Sequence , Animals , Cell Adhesion Molecules, Neuronal/metabolism , Drosophila melanogaster/genetics , Embryo, Nonmammalian , Genes, Lethal , Insect Proteins/metabolism , Molecular Sequence Data , Muscle, Skeletal/cytology , Muscle, Skeletal/pathology , Mutation , Sequence Homology, Amino AcidABSTRACT
Synthetic lipopeptides derived from the N-terminus of bacterial lipoprotein constitute potent macrophage activators and polyclonal B-lymphocyte stimulators. They are also efficient immunoadjuvants in parenteral, oral and nasal immunization either in combination with or after covalent linkage to an antigen. Here we show how alterations in the molecular structure influence their biological properties indicating P3CSK4 as one of the most active members of a lipopentapeptide fatty acid library. This compound resulted in a most pronounced macrophage stimulation as indicated by NO release, activation of NFkappaB translocation, and enhancement of tyrosine protein phosphorylation. Furthermore, P3CSK4 activates/represses an array of at least 140 genes partly involved in signal transduction and regulation of the immune response. Finally we have evidence that P3CSK4 constitutes an effective adjuvant for DNA immunizations, especially increasing weak humoral immune responses. Our findings are of importance for further optimizing both conventional and genetic immunization, and for the development of novel synthetic vaccines.
