Tropomyosin isoform 3 promotes the formation of filopodia by regulating the recruitment of actin-binding proteins to actin filaments.

Tropomyosins are believed to function in part by stabilizing actin filaments. However, accumulating evidence suggests that fundamental differences in function exist between tropomyosin isoforms, which contributes to the formation of functionally distinct filament populations. We investigated the functions of the high-molecular-weight isoform Tm3 and examined the molecular properties of Tm3-containing actin filament populations.

PMD tolerance of 288 Gbit/s Coherent WDM and transmission over unrepeatered 124 km of field-installed single mode optical fiber.

Low-cost, high-capacity optical transmission systems are required for metropolitan area networks. Direct-detected multi-carrier systems are attractive candidates, but polarization mode dispersion (PMD) is one of the major impairments that limits their performance. In this paper, we report the first experimental analysis of the PMD tolerance of a 288Gbit/s NRZ-OOK Coherent Wavelength Division Multiplexing system.

Tropomyosin isoform modulation of focal adhesion structure and cell migration.

Orderly cell migration is essential for embryonic development, efficient wound healing and a functioning immune system and the dysregulation of this process leads to a number of pathologies. The speed and direction of cell migration is critically dependent on the structural organization of focal adhesions in the cell. While it is well established that contractile forces derived from the acto-myosin filaments control the structure and growth of focal adhesions, how this may be modulated to give different outcomes for speed and persistence is not well understood.

New aspects of tropomyosin-regulated neuritogenesis revealed by the deletion of Tm5NM1 and 2.

Previous studies have shown that the overexpression of tropomyosins leads to isoform-specific alterations in the morphology of subcellular compartments in neuronal cells. Here we have examined the role of the most abundant set of isoforms from the gamma-Tm gene by knocking out the alternatively spliced C-terminal exon 9d. Despite the widespread location of exon 9d-containing isoforms, mice were healthy and viable.

Internal and external paralogy in the evolution of tropomyosin genes in metazoans.

Nature contains a tremendous diversity of forms both at the organismal and genomic levels. This diversity motivates the twin central questions of molecular evolution: what are the molecular mechanisms of adaptation, and what are the functional consequences of genomic diversity. We report a 22-species comparative analysis of tropomyosin (PPM) genes, which exist in a variety of forms and are implicated in the emergence of a wealth of cellular functions, including the novel muscle functions integral to the functional diversification of bilateral animals.

Coordination complex SH2 domain proteomimetics: an alternative approach to disrupting oncogenic protein-protein interactions.

We report the first application of coordination complexes as functional proteomimetics of the Src homology 2 (SH2) phosphopeptide-binding domain. As a proof-of-concept, functionalized bis-dipicolylamine (BDPA) copper(ii) complexes are shown to disrupt oncogenic Stat3-Stat3 protein complexes and elicit promising anti-tumour activity.

Accelerated carbonation treatment of industrial wastes.

The disposal of industrial waste presents major logistical, financial and environmental issues. Technologies that can reduce the hazardous properties of wastes are urgently required. In the present work, a number of industrial wastes arising from the cement, metallurgical, paper, waste disposal and energy industries were treated with accelerated carbonation.

A novel small-molecule disrupts Stat3 SH2 domain-phosphotyrosine interactions and Stat3-dependent tumor processes.

The molecular modeling of the phosphotyrosine (pTyr)-SH2 domain interaction in the Stat3:Stat3 dimerization, combined with in silico structural analysis of the Stat3 dimerization disruptor, S3I-201, has furnished a diverse set of analogs. We present evidence from in vitro biochemical and biophysical studies that the structural analog, S3I-201.1066 directly interacts with Stat3 or the SH2 domain, with an affinity (K(D)) of 2.

Alternatively spliced N-terminal exons in tropomyosin isoforms do not act as autonomous targeting signals.

Tropomyosin (Tm) polymerises head-to-tail to form a continuous polymer located in the major groove of the actin filament. Multiple Tm isoforms are generated by alternative splicing of four genes, and individual isoforms show specific localisation patterns in many cell types, and can have differing effects on the actin cytoskeleton. Fluorescently-tagged Tm isoforms and mutants were expressed in C2C12 cells to investigate the mechanisms of alternative localisation of high molecular weight (HMW) and low molecular weight (LMW) Tms.

Novel asymmetrically functionalized bis-dipicolylamine metal complexes: peripheral decoration of a potent anion recognition scaffold.

We report the design and synthesis of a novel class of asymmetrically functionalized, ditopic bis-dipicolylamine (BDPA) ligands. A key feature of this research involved the controlled, sequential functional group decoration of a potent molecular recognition scaffold. Calorimetric screening identified a BDPA analogue as a highly potent (K(a) approximately 10(6) M(-1)) and selective sensor for inorganic phosphate.

Negative autoregulation of GTF2IRD1 in Williams-Beuren syndrome via a novel DNA binding mechanism.

The GTF2IRD1 gene is of principal interest to the study of Williams-Beuren syndrome (WBS). This neurodevelopmental disorder results from the hemizygous deletion of a region of chromosome 7q11.23 containing 28 genes including GTF2IRD1.

Diverse roles of the actin cytoskeleton in striated muscle.

In addition to the highly specialized contractile apparatus, it is becoming increasingly clear that there is an extensive actin cytoskeleton which underpins a wide range of functions in striated muscle. Isoforms of cytoskeletal actin and actin-associated proteins (non-muscle myosins, cytoskeletal tropomyosins, and cytoskeletal alpha-actinins) have been detected in a number of regions of striated muscle: the sub-sarcolemmal costamere, the Z-disc and the T-tubule/sarcoplasmic reticulum membranes. As the only known function of these proteins is through association with actin filaments, their presence in striated muscles indicates that there are spatially and functionally distinct cytoskeletal actin filament systems in these tissues.

Molecular disruption of oncogenic signal transducer and activator of transcription 3 (STAT3) protein.

Signal transducer and activator of transcription protein 3 (STAT3) is a latent cytosolic transcription factor that is widely recognized as being a master regulator of the cellular functions that lead to the cancer phenotype. Constitutively activated STAT3 protein activity is routinely observed in human cancers, promoting uncontrolled cell proliferation and suppressing apoptosis. Until relatively recently, inhibition of STAT3 transcriptional activity was achieved indirectly via suppression of upstream kinase activators and extracellular cytokine and (or) growth factor stimuli.

New approaches to targeting the actin cytoskeleton for chemotherapy.

The actin cytoskeleton is indispensable for normal cellular function. In particular, several actin-based structures coordinate cellular motility, a process hijacked by tumor cells in order to facilitate their propagation to distant sites. The actin cytoskeleton, therefore, represents a point for chemotherapeutic intervention.

Production of lightweight aggregate from industrial waste and carbon dioxide.

The concomitant recycling of waste and carbon dioxide emissions is the subject of developing technology designed to close the industrial process loop and facilitate the bulk-re-use of waste in, for example, construction. The present work discusses a treatment step that employs accelerated carbonation to convert gaseous carbon dioxide into solid calcium carbonate through a reaction with industrial thermal residues. Treatment by accelerated carbonation enabled a synthetic aggregate to be made from thermal residues and waste quarry fines.

A cytoskeletal tropomyosin can compromise the structural integrity of skeletal muscle.

We have identified a number of extra-sarcomeric actin filaments defined by cytoskeletal tropomyosin (Tm) isoforms. Expression of a cytoskeletal Tm (Tm3) not normally present in skeletal muscle in a transgenic mouse resulted in muscular dystrophy. In the present report we show that muscle pathology in this mouse is late onset (between 2 and 6 months of age) and is predominately in the back and paraspinal muscles.

A photostable, pH-invariant fluorescein derivative for single-molecule microscopy.

We herein report the comprehensive characterization of the spectral and single-photon fluorescence properties of a recently synthesized fluorescein derivative and its biotinylated analog. The fluorophore displays significant increases in photostability compared to the known fluorescein label fluorescein isothiocyanate (FITC), as well as superb pH independence. This fluorescein variant has two readily accessible functional groups (aniline NH2 and phenol OH) that can be activated or blocked independently and can serve, for instance, as a fluorescent bridge between two different recognition motifs.

Methylguanine DNA methyltransferase-mediated drug resistance-based selective enrichment and engraftment of transplanted stem cells in skeletal muscle.

Cell replacement therapy using stem cell transplantation holds much promise in the field of regenerative medicine. In the area of hematopoietic stem cell transplantation, O(6)-methylguanine-DNA methyltransferase MGMT (P140K) gene-mediated drug resistance-based in vivo enrichment strategy of donor stem cells has been shown to achieve up to 75%-100% donor cell engraftment in the host's hematopoietic stem cell compartment following repeated rounds of selection. This strategy, however, has not been applied in any other organ system.

Emerging issues for tropomyosin structure, regulation, function and pathology.

There is a growing awareness of the role of tropomyosin in the regulation of the actin filament. Work in the field is increasingly directed at understanding the mechanisms of function at both a molecular and atomic level and developing therapeutic strategies to treat tropomyosin-based pathology. This chapter highlights unresolved issues that cross the boundaries between individual chapters and are likely to be fertile areas of research in the future.

Isoform sorting of tropomyosins.

Cytoskeletal tropomyosin (Tm) isoforms show extensive intracellular sorting, resulting in spatially distinct actin-filament populations. Sorting of Tm isoforms has been observed in a number of cell types, including fibroblasts, epithelial cells, osteoclasts, neurons and muscle cells. Different Tm isoforms have differential impact on the activity of a number of actin-binding proteins and can therefore differentially regulate actin filament function.

Introduction and historical perspective.

Tropomyosin is a coiled coil dimer which forms a polymer along the major groove of the majority of actin filaments. It is therefore one of the two primary components of the actin filament. Our understanding of the biological function of tropomyosin has been driven almost entirely by its role in striated muscle.

Primary support cultures of hippocampal and substantia nigra neurons.

Primary cultures of rat and murine hippocampal neurons are widely used to reveal cellular mechanisms in neurobiology. Their use is limited, as culturing at low density is often not possible or is dependent on sophisticated methods. Here we present a novel method for culturing embryonic (E16.

Tropomyosin isoform expression regulates the transition of adhesions to determine cell speed and direction.

The balance of transition between distinct adhesion types contributes to the regulation of mesenchymal cell migration, and the characteristic association of adhesions with actin filaments led us to question the role of actin filament-associating proteins in the transition between adhesive states. Tropomyosin isoform association with actin filaments imparts distinct filament structures, and we have thus investigated the role for tropomyosins in determining the formation of distinct adhesion structures. Using combinations of overexpression, knockdown, and knockout approaches, we establish that Tm5NM1 preferentially stabilizes focal adhesions and drives the transition to fibrillar adhesions via stabilization of actin filaments.