Disease relevance of actin

• We examined the temporal order of trans- and cis-splicing by analyzing cDNAs of partially processed transcripts from an actin gene of the parasitic nematode, Onchocerca volvulus, which has five short introns [1].

High impact information on actin

• Our results suggest that UNC-73 acts cell autonomously in a protein complex to regulate actin dynamics during cell and growth cone migrations [2].
• The evidence suggests that the actin mRNA leader sequence is acquired from this novel nucleotide transcript by an intermolecular trans-splicing mechanism [3].
• The myosin binds to F actin in a polar and ATP-sensitive manner, and the Mg2+-ATPase is activated by either F actin or nematode thin filaments [4].
• We focus on asymmetric cell division as a function of the actin and microtubule cytoskeletons, emphasizing the cell biology of polarity [5].
• In hair cells of the inner ear, evidence suggests that an extracellular tip link pulls on a channel, which attached intracellularly to actin via a tension-regulating myosin 1beta [6].

Biological context of actin

• Recent insights from this system have determined the involvement in morphogenesis of key proteins, including the actin-regulating WASP and Ena proteins, potential guidance molecules such as the Eph and Robo receptors, and the cell-cell signaling proteins of the Wnt pathway [7].
• RNA interference of Ce-kettin caused weak disorganization of the actin filaments in body wall muscle [8].
• Although the model refers primarily to the locomotion of nematode sperm, it has important implications for the mechanics of actin-based cell motility [9].
• It is hypothesized that actin plays a role in the shaping of the cell and in the arrangement of its organelles during nematode spermiogenesis, when MSP is present, in an inactive state, in the fibrous bodies [10].
• In Caenorhabditis elegans and Ascaris suum, previous studies have reported that sperm motility does not involve actin, but, instead, requires a specific cytoskeletal protein, namely major-sperm-protein (MSP) [10].

Anatomical context of actin

• Given these advantages, it has been possible to use C. elegans to investigate the different ways in which the actin cytoskeleton drives the cellular rearrangements underlying morphogenesis, through regulated polymerization or actomyosin contraction [7].
• TM4SF10 colocalized with ZO1 and p120ctn in undifferentiated confluent podocytes and also colocalized with the tips of actin filaments at cell contacts [11].
• Tropomyosin shows a distinct pattern in spermatids, but is located in the MSP and actin-containing cap in spermatozoa [10].
• We have studied the localization of actin and MSP in spermatids and spermatozoa of Graphidium strigosum (Dujardin, 1845), a species which has elongate male germ cells in which organelles are easily identified [12].
• Immunocytochemical observations reveal that actin and MSP have an identical localization in precise areas of the male germ cells [12].

Associations of actin with chemical compounds

• The final step, glycerol gradient centrifugation, yielded fractions that are contaminated by, at most, 1-2% with actin, tropomyosin, or ribosome-associated proteins on the basis of Coomassie Blue staining and electron microscopy [13].
• On the other hand, anti-Ash antibody had no effect on S phase entry or actin stress fiber formation induced by either serum or lysophosphatidic acid [14].
• Removal of the C-terminal isoleucine (Ile152) by carboxypeptidase A or truncation by mutagenesis eliminated F-actin binding activity but strongly enhanced actin depolymerizing activity [15].
• Biochemical studies of talin have shown that it binds to the proteins integrin, vinculin, and actin in vitro [16].
• In this model, Mg2+ ATP is bound to a pocket between two opposing alpha/beta domains, while actin undergoes electrostatic interactions with lysine-rich surface loops on two other domains [17].

Physical interactions of actin

• However, the mechanism by which AIP1 interacts with ADF/cofilin and actin is not clearly understood [18].

Co-localisations of actin

• The Caenorhabditis elegans unc-87 gene product is essential for the maintenance of the nematode body wall muscle where it is found colocalized with actin in the I band [19].

Regulatory relationships of actin

• Actin-interacting protein 1 (AIP1) is a WD40 repeat protein that enhances actin filament disassembly in the presence of actin-depolymerizing factor (ADF)/cofilin [18].
• During neuronal development, various actin-binding proteins regulate dynamics of actin cytoskeleton in the growth cones of developing axons [20].
• Both myosin control and actin control operate simultaneously in the majority of invertebrates tested [21].
• Regulation of muscular contraction. Distribution of actin control and myosin control in the animal kingdom [21].
• Molluscs lack actin control since troponin is not present in sufficient quantities [21].

Other interactions of actin

• Sperm of the nematode, Ascaris suum, are amoeboid cells that do not require actin or myosin to crawl over solid substrata [22].
• Moreover, nematode sperm lack detectable molecular motors or the battery of actin-binding proteins that characterize actin-based motility [9].
• The increased synthesis of forms of myosin, actin and troponin in the nematode living in the rapid-responder SWR host may relate to the attempted reorganisation or repair of the cytoskeleton and/or muscle layer in the host immune initiated, increased mucus production and smooth muscle activity within intestinal environment [23].
• Here, we performed a detailed characterization of the pha-2 phenotype using cell-type-specific reporters, physical manipulation of the nuclei in pharyngeal muscle cells using "optical tweezers", electron microscopy, staining of the actin cytoskeleton as well as phenotypic rescue and ectopic expression experiments [24].
• Three different X-chromosome clones, including part of an actin gene, part of a myosin heavy chain gene, and all of two myosin light chain genes, feminize chromosomal males [25].

Analytical, diagnostic and therapeutic context of actin

• The FBs contain actin as shown by immunofluorescence using a monoclonal anti-actin antibody and by affinity cytochemistry using fluorescent phalloidin [26].
• Cytokinesis involves the concerted efforts of the microtubule and actin cytoskeletons as well as vesicle trafficking and membrane remodeling to form the cleavage furrow and complete daughter cell separation [27].
• Affinity chromatography of nematode extracts on a column of immobilized HSP25 resulted in specific binding of vinculin and alpha-actinin but not actin, as revealed by Western blotting [28].
• In addition, cryoelectron microscopy images of actomyosin VI show the two heads bound to the actin monomers with a broad distribution of distances, including some as close as a few nanometers [29].
• Immunohistochemistry shows that some actin is localized in patches in the pseudopod [30].

References