Disease relevance of Act88F

• Transgenic flies that express Act88F with either a 6x histidine tag or an 11-residue peptide derived from vesicular stomatitis virus G protein at the C terminus were flightless [1].
• ADP-ribosylation of Drosophila indirect-flight-muscle actin and arthrin by Clostridium botulinum C2 toxin and Clostridium perfringens iota toxin [2].
• Defining the genome-wide transcriptional response to muscle hypercontraction in Drosophila has revealed candidate loci that may participate in the pathogenesis of muscular dystrophy and in compensatory muscle repair pathways through modulation of the actin cytoskeleton [3].
• Mutations in Myosin ID completely reverse the left-right axis (situs inversus), a phenotype that is dependent on an intact actin cytoskeleton [4].
• Here, wild-type (WT) human alpha-cardiac actin and a mutant E99K actin have been expressed and purified from the baculovirus/insect cell expression system [5].

Psychiatry related information on Act88F

• Thus Myo31DF is a dextral gene with actin-based motor activity controlling situs choice [6].

High impact information on Act88F

• However, DmIKK epsilon-mediated degradation of DIAP1 does not regulate apoptosis as might be predicted but instead regulates actin dynamics, cell morphology, and the differentiation of sensory organ precursor cells [7].
• Here, we use a new RNA anchoring assay in living Drosophila blastoderm embryos to show that apical anchoring of mRNA after completion of dynein transport does not depend on actin or on continuous active transport by the motor [8].
• Arthrin reacts with an anti-ubiquitin antibody, which demonstrates that its extra mass results from ubiquitin ligation [9].
• Utilizing the germ-line transformation technique we demonstrate that one genetic lesion associated with the raised phenotype resides within the act88F actin gene, which, as a result, fails to specify normal mRNA accumulation during thoracic muscle differentiation [10].
• We also provide evidence for a distinct second genetic lesion, which apparently eliminates proper posttranslational modification of two myofibrillar proteins, one of which is actin [10].

Biological context of Act88F

• Two missense mutations of the flight muscle-specific actin gene of Drosophila melanogaster, Act88F, assemble into normally structured myofibrils but affect the flight ability of flies and the mechanical kinetics of isolated muscle fibers [11].
• Actomyosin kinetics and in vitro motility of wild-type Drosophila actin and the effects of two mutations in the Act88F gene [11].
• Twenty-five mutations were created in the Drosophila melanogaster Act88F actin gene by in vitro mutagenesis and the mutant actins expressed in vitro [12].
• Using null and antimorphic mutants to show decreased walking ability and delayed/reduced oviposition we demonstrated that Act88F expression is functionally important in multiple muscle groups [13].
• We have confirmed endogenous Act88F gene expression in these other muscles by in situ hybridisation studies [13].

Anatomical context of Act88F

• In contrast, expression of N-terminally tagged Act88F at amounts comparable with that of wild-type flies yielded fairly normal-looking myofibrils and partially reconstituted flight ability in the transformants [1].
• Despite having different charges as determined by two-dimensional (2D) gel electrophoresis, Act88F expressed in vivo and in vitro in rabbit reticulocyte lysate bind to DNase I with equal affinity and are able to copolymerise with bulk rabbit actin equally well [14].
• We show in this paper that neither sarcomeric myosin nor actin are required for myoblast fusion or the subsequent morphogenesis of muscle fibres, i.e. fibre morphogenesis does not depend on myofibrillogenesis [15].
• Kettin is a high molecular mass protein of insect muscle that in the sarcomeres binds to actin and alpha-actinin [16].
• Using a quantitative in vitro motility assay we have found that the wild type Drosophila ACT88F actin behaved like rabbit skeletal muscle actin when tropomyosin and troponin were added at pCa5 and pCa9 [17].

Associations of Act88F with chemical compounds

• Whereas the gene products of various C-terminal mutants of Act88F translated in vitro (E334K, V339I, E364K, G368E, R372H) were substrates for ADP-ribosylation by C. botulinum C2 toxin and by C. perfringens iota toxin, neither toxin modified the N-terminal O-12 deletion mutant [2].
• Actin from the R177Q mutant of Act88F translated in vivo was not ADP-ribosylated confirming Arg-177 as the ADP-ribose acceptor [2].
• A single G greater than A transition converts a tryptophan (TGG) codon to an opal (TGA) terminator, thus deleting the carboxy-terminal 20 amino acids of an actin isoform that accumulates only in thoracic flight muscles [18].
• However, the NH2-terminal 12 residues show similarity to the NH2-terminal sequence of actin, a region that interacts with myosin [19].
• Myosin VIIa moves along actin filaments as a processive, double-headed single molecule when dimerized by the inclusion of a leucine zipper at the C terminus of the coiled-coil domain [20].

Physical interactions of Act88F

• The second site suppression is due to a leucine to phenylalanine change within a heptameric leucine string motif adjacent to the actin binding domain of TnI [21].
• In the absence of Ca2+, tropomyosin was in a position that blocked the myosin-binding sites on actin, as previously found with wild-type filaments [22].
• As a result, myosin VIIB will be predominantly strongly bound to actin during steady-state ATP hydrolysis (its duty ratio will be at least 80%) [23].
• Zygotic activity of the nullo locus is required to stabilize the actin-myosin network during cellularization in Drosophila [24].

Regulatory relationships of Act88F

• In addition, we identified previously uncharacterized proteins with putative actin-interaction domains that are up-regulated in Mhc mutants and differentially expressed in muscles [3].
• DRhoGEF2 regulates actin organization and contractility in the Drosophila blastoderm embryo [25].

Other interactions of Act88F

• Drosophila projectin is an extremely large protein found within the muscle sarcomeric unit, parallel with the actin and myosin filaments [26].
• Flight muscle contraction is regulated by both stretch and Ca(2+)-induced thin filament (actin + tropomyosin + troponin complex) activation [27].
• The human (beta)-cytoplasmic actin differs by only 15 amino acids from Act88F actin which is the only actin expressed in the indirect flight muscle (IFM) of Drosophila melanogaster [28].
• These features suggest a role for flightin in the regulation of contraction, possibly by modulating actin-myosin interaction [19].
• Drosophila genomic DNAs containing a chromosomal locus 87C1 70,000-dalton heat shock protein gene, the locus 79B actin gene, and the 88F actin gene have been used as templates in an in vitro HeLa transcription system [29].

Analytical, diagnostic and therapeutic context of Act88F

• Immunoblotting demonstrated the presence of kettin isoforms in normal Drosophila IFM myofibrils and in myofibrils from an actin-null mutant [16].
• Here we survey for the presence of arthrin in 63 species of insect across nine orders using Western blotting [30].
• We used polymerase chain reaction to amplify a portion of the Act88F actin gene that includes 1420 nucleotides of flanking DNA, the transcription start, first intron, and initiator codon, incorporating the fragment into the Drosophila germ line transformation vector pCaSpeR [31].
• Electron microscopy of isolated thick filaments and of myosin molecules suggests that the molecules are flexible, but myosin fragments and crossbridges have been reported not to interact with inappropriately oriented actin filaments [32].
• We studied cyclic reorganizations of filamentous actin, myosin II and microtubules in syncytial Drosophila blastoderms using drug treatments, time-lapse movies and laser scanning confocal microscopy of fixed stained embryos (including multiprobe three-dimensional reconstructions) [33].

References