Actin nucleation and elongation factors: mechanisms and interplay

Chesarone, Melissa A.; Goode, Bruce L.

doi:10.1016/j.ceb.2008.12.001

Cited by 288 publications

(264 citation statements)

References 55 publications

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“…In eukaryotes, specific protein complexes act as nucleation complexes for filament formation, such as the ARP2/3 complex and formins for actin filaments and the microtubule organizing center (MTOC) microtubules (Luders and Stearns 2007;Chesarone and Goode 2009). Interestingly, evidence for a complex involved in filament capping and polymerization in bacteria has been provided for the actin-like ParM filament involved in plasmid segregation, which is stabilized by the small ParR protein in complex with a centromere-like parC DNA fragment (Salje and Lowe 2008).…”

Section: Discussionmentioning

confidence: 99%

Positive control of cell division: FtsZ is recruited by SsgB during sporulation ofStreptomyces

Willemse¹,

Borst²,

Waal³

et al. 2011

Genes Dev.

171

201

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In bacteria that divide by binary fission, cell division starts with the polymerization of the tubulin homolog FtsZ at mid-cell to form a cell division scaffold (the Z ring), followed by recruitment of the other divisome components. The current view of bacterial cell division control starts from the principle of negative checkpoints that prevent incorrect Z-ring positioning. Here we provide evidence of positive control of cell division during sporulation of Streptomyces, via the direct recruitment of FtsZ by the membrane-associated divisome component SsgB. In vitro studies demonstrated that SsgB promotes the polymerization of FtsZ. The interactions are shown in vivo by time-lapse imaging and Fö rster resonance energy transfer and fluorescence lifetime imaging microscopy (FRET-FLIM), and are corroborated independently via two-hybrid studies. As determined by fluorescence recovery after photobleaching (FRAP), the turnover of FtsZ protofilaments increased strongly at the time of Z-ring formation. The surprising positive control of Z-ring formation by SsgB implies the evolution of an entirely new way of Z-ring control, which may be explained by the absence of a mid-cell reference point in the long multinucleoid hyphae. In turn, the localization of SsgB is mediated through the orthologous SsgA, and premature expression of the latter is sufficient to directly activate multiple Z-ring formation and hyperdivision at early stages of the Streptomyces cell cycle.

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Section: Discussionmentioning

confidence: 99%

Positive control of cell division: FtsZ is recruited by SsgB during sporulation ofStreptomyces

Willemse¹,

Borst²,

Waal³

et al. 2011

Genes Dev.

171

201

View full text Add to dashboard Cite

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“…Specific protein assemblies, composed of various actin-binding proteins, operate in these processes to nucleate and elongate new actin filaments, arrange them into complex 3D arrays, and subsequently recycle them to replenish the G-actin pool (5). The only protein families known to date that actively drive the elongation of actin filaments by incorporation of actin monomers at growing barbed ends are formins and Ena/VASP proteins, albeit their modes of action are considerably different (6)(7)(8)(9).…”

mentioning

confidence: 99%

Distinct VASP tetramers synergize in the processive elongation of individual actin filaments from clustered arrays

Brühmann

Ushakov

Winterhoff

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Ena/VASP proteins act as actin polymerases that drive the processive elongation of filament barbed ends in membrane protrusions or at the surface of bacterial pathogens. Based on previous analyses of fast and slow elongating VASP proteins by in vitro total internal reflection fluorescence microscopy (TIRFM) and kinetic and thermodynamic measurements, we established a kinetic model of Ena/VASP-mediated actin filament elongation. At steady state, it entails that tetrameric VASP uses one of its arms to processively track growing filament barbed ends while three G-actin-binding sites (GABs) on other arms are available to recruit and deliver monomers to the filament tip, suggesting that VASP operates as a single tetramer in solution or when clustered on a surface, albeit processivity and resistance toward capping protein (CP) differ dramatically between both conditions. Here, we tested the model by variation of the oligomerization state and by increase of the number of GABs on individual polypeptide chains. In excellent agreement with model predictions, we show that in solution the rates of filament elongation directly correlate with the number of free GABs. Strikingly, however, irrespective of the oligomerization state or presence of additional GABs, filament elongation on a surface invariably proceeded with the same rate as with the VASP tetramer, demonstrating that adjacent VASP molecules synergize in the elongation of a single filament. Additionally, we reveal that actin ATP hydrolysis is not required for VASP-mediated filament assembly. Finally, we show evidence for the requirement of VASP to form tetramers and provide an amended model of processive VASPmediated actin assembly in clustered arrays.actin | Ena/VASP | TIRF | cluster | formin

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“…Actin-related protein 2/3 (Arp2/3), formins, and tandem-G-actin-binding proteins are the three classes of known actin nucleators in nonmuscle cells (1)(2)(3)(4)(5)(6)(7). Arp2/3-mediated actin nucleation produces branched actin networks, whereas formins and tandem-G-actin-binding nucleators result in long, unbranched actin filaments (1)(2)(3)(4)(5)(6)(7).…”

mentioning

confidence: 99%

Mechanisms of leiomodin 2-mediated regulation of actin filament in muscle cells

Chen

Kondrashkina

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Leiomodin (Lmod) is a class of potent tandem-G-actin-binding nucleators in muscle cells. Lmod mutations, deletion, or instability are linked to lethal nemaline myopathy. However, the lack of highresolution structures of Lmod nucleators in action severely hampered our understanding of their essential cellular functions. Here we report the crystal structure of the actin-Lmod2 162-495 nucleus. The structure contains two actin subunits connected by one Lmod2 162-495 molecule in a non-filament-like conformation. Complementary functional studies suggest that the binding of Lmod2 stimulates ATP hydrolysis and accelerates actin nucleation and polymerization. The high level of conservation among Lmod proteins in sequence and functions suggests that the mechanistic insights of human Lmod2 uncovered here may aid in a molecular understanding of other Lmod proteins. Furthermore, our structural and mechanistic studies unraveled a previously unrecognized level of regulation in mammalian signal transduction mediated by certain tandem-G-actin-binding nucleators.actin nucleation | nemaline myopathy | pointed-end elongation

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Actin nucleation and elongation factors: mechanisms and interplay

Cited by 288 publications

References 55 publications

Positive control of cell division: FtsZ is recruited by SsgB during sporulation ofStreptomyces

Positive control of cell division: FtsZ is recruited by SsgB during sporulation ofStreptomyces

Distinct VASP tetramers synergize in the processive elongation of individual actin filaments from clustered arrays

Mechanisms of leiomodin 2-mediated regulation of actin filament in muscle cells

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