![]() ![]() Actin patches are areas of a few microns enriched in branched F-actin ( Willig et al., 2014), and were suggested to serve as outgrowth points for filopodia ( Korobova and Svitkina, 2010). Apart from that, additional F-actin based structures within the shafts of dendrites have been discovered more recently: actin patches, longitudinal fibers, and rings (Figures 1A,B). F-actin arrangement within spines is very dynamic and is subject to constant activity-dependent remodeling ( Okamoto et al., 2004). Perhaps the most striking F-actin-based structures in dendrites are so-called spines, small membranous protrusions that harbor synapses. Organization of F-Actin in DendritesĪctin filaments can be arranged in linear or in branched conformations, and together with stable MT arrays and neurofilaments they form the cytoskeleton in dendrites ( Yuan et al., 2012 Sainath and Gallo, 2014). In light of novel discoveries related to the role and organization of neuronal F-actin, in this review we will focus on the mechanisms and molecular players that fine-tune the actin cytoskeleton, thereby controlling dendrite morphology and function. The process of neuronal polarization is largely driven by an intrinsic program ( Horton et al., 2006), however, this program is subject to modification by diverse environmental stimuli, including synaptic activity, that can rapidly feed back to the cytoskeleton. Their organization is spatially and temporally controlled by numerous actin binding proteins (ABPs) and microtubule associated proteins, which extensively interact and feed back to each other ( Georges et al., 2008 Coles and Bradke, 2015). F-actin and microtubules (MTs) are the main mediators of neuronal polarity. One of the critical aspects in establishment and maintenance of the dendritic structure is the well-controlled turnover of cytoskeletal elements ( Tsaneva-Atanasova et al., 2009). Dendrites can be morphologically and functionally sub-compartmentalized, particularly in pyramidal neurons ( Shah et al., 2010 Yuan et al., 2015). ![]() They integrate information from typically thousands of synaptic inputs, which is then further transmitted via the cell body to the neuron’s single axon ( Magee, 2000 Gulledge et al., 2005). Dendrites are long, highly branched extensions from the cell body that can reach hundreds of microns, forming a widespread and complex arbor. The unique ability of neurons to compute and allocate information relies on their polarized morphology, which comprises several functionally distinct compartments. In this review, we focus on recent developments regarding the role of actin in dendrite morphology, the regulation of actin dynamics by internal and external factors, and the role of F-actin in dendritic protein trafficking. So far, research has been focused on the specific roles of actin in the axon, while it is becoming more and more apparent that in the dendrite, actin is not only confined to dendritic spines, but serves many additional and important functions. Apart from that striking feature, patches of F-actin and deep actin filament bundles have been described along the lengths of neurites. With the development of super-resolution microscopy in the past few years, previously unknown structures of the actin cytoskeleton have been uncovered: a periodic lattice consisting of actin and spectrin seems to pervade not only the whole axon, but also dendrites and even the necks of dendritic spines. For a long time, the most prominent roles that were attributed to actin in neurons were the movement of growth cones, polarized cargo sorting at the axon initial segment, and the dynamic plasticity of dendritic spines, since those compartments contain large accumulations of actin filaments (F-actin) that can be readily visualized using electron- and fluorescence microscopy. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |