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1. Actin filament sliding in CaMKII-actin bundles

   https://doi.org/10.1016/j.bpj.2022.11.1051  

   Basurco, Carlos A.; Schafer, Nicholas P.; Waxham, Neal; Cheung, Margaret S.; Wolynes, Peter G. (February 2023, Biophysical Journal)
2. Actin chromobody imaging reveals sub-organellar actin dynamics

   https://doi.org/10.1038/s41592-020-0926-5  

   Schiavon, Cara R.; Zhang, Tong; Zhao, Bing; Moore, Andrew S.; Wales, Pauline; Andrade, Leonardo R.; Wu, Melissa; Sung, Tsung-Chang; Dayn, Yelena; Feng, Jasmine W.; et al (September 2020, Nature Methods)

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3. Plakophilin-3 Binds the Membrane and Filamentous Actin without Bundling F-Actin

   https://doi.org/10.3390/ijms24119458  

   Gupta, Jyoti; Rangarajan, Erumbi S.; Troyanovsky, Regina B.; Indra, Indrajyoti; Troyanovsky, Sergey M.; Izard, Tina (June 2023, International Journal of Molecular Sciences)

   Plakophilin-3 is a ubiquitously expressed protein found widely in epithelial cells and is a critical component of desmosomes. The plakophilin-3 carboxy-terminal domain harbors nine armadillo repeat motifs with largely unknown functions. Here, we report the 5 Å cryogenic electron microscopy (cryoEM) structure of the armadillo repeat motif domain of plakophilin-3, one of the smaller cryoEM structures reported to date. We find that this domain is a monomer or homodimer in solution. In addition, using an in vitro actin co-sedimentation assay, we show that the armadillo repeat domain of plakophilin-3 directly interacts with F-actin. This feature, through direct interactions with actin filaments, could be responsible for the observed association of extra-desmosomal plakophilin-3 with the actin cytoskeleton directly attached to the adherens junctions in A431 epithelial cells. Further, we demonstrate, through lipid binding analyses, that plakophilin-3 can effectively be recruited to the plasma membrane through phosphatidylinositol-4,5-bisphosphate-mediated interactions. Collectively, we report on novel properties of plakophilin-3, which may be conserved throughout the plakophilin protein family and may be behind the roles of these proteins in cell–cell adhesion. 

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4. Dissociation Mechanisms of G-actin Subunits Govern Deformation Response of Actin Filament

   https://doi.org/10.1021/acs.biomac.0c01602  

   Jaswandkar, Sharad V.; Faisal, H M; Katti, Kalpana S.; Katti, Dinesh R. (February 2021, Biomacromolecules)

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5. Actin crosslinker competition and sorting drive emergent GUV size-dependent actin network architecture

   https://doi.org/10.1038/s42003-021-02653-6  

   Bashirzadeh, Yashar; Redford, Steven A.; Lorpaiboon, Chatipat; Groaz, Alessandro; Moghimianavval, Hossein; Litschel, Thomas; Schwille, Petra; Hocky, Glen M.; Dinner, Aaron R.; Liu, Allen P. (September 2021, Communications Biology)

   Abstract The proteins that make up the actin cytoskeleton can self-assemble into a variety of structures. In vitro experiments and coarse-grained simulations have shown that the actin crosslinking proteins α-actinin and fascin segregate into distinct domains in single actin bundles with a molecular size-dependent competition-based mechanism. Here, by encapsulating actin, α-actinin, and fascin in giant unilamellar vesicles (GUVs), we show that physical confinement can cause these proteins to form much more complex structures, including rings and asters at GUV peripheries and centers; the prevalence of different structures depends on GUV size. Strikingly, we found that α-actinin and fascin self-sort into separate domains in the aster structures with actin bundles whose apparent stiffness depends on the ratio of the relative concentrations of α-actinin and fascin. The observed boundary-imposed effect on protein sorting may be a general mechanism for creating emergent structures in biopolymer networks with multiple crosslinkers. 

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