Coordination of Actin Filament and Microtubule Dynamics during Neurite Outgrowth

Abstract

Although much evidence suggests that axon growth and guidance depend on well-coordinated cytoskeletal dynamics, direct characterization of the corresponding molecular events has remained a challenge. Here, we address this outstanding problem by examining neurite outgrowth stimulated by local application of cell adhesion substrates. During acute outgrowth, the advance of organelles and underlying microtubules into the central domain was correlated with regions of attenuated retrograde actin network flow in the periphery. Interestingly, as adhesion sites matured, contractile actin arc structures, known to be regulated by the Rho/Rho Kinase/myosin II signaling cascade, became more robust and coordinated microtubule movements in the growth cone neck. When Rho Kinase was inhibited, although growth responses occurred with less of a delay, microtubules failed to consolidate into a single axis of growth. These results reveal a new role for Rho Kinase and myosin II contractility in regulation of microtubule behavior during neuronal growth.

The contractome – a systems view of actomyosin contractility in non-muscle cells

“…The mechanical properties and shape of the new daughter cell are determined by its ability to contract and maintain tension in its cortical cytoskeleton (Bischofs et al, 2008;Martens and Radmacher, 2008;Schafer and Radmacher, 2005). In addition, the dynamic properties of the actin cytoskeleton and its organization into a variety of actin-rich structures, such as lamellipodia and stress fibers, are also affected by contractility (Hirata et al, 2008;Hotulainen and Lappalainen, 2006;Medeiros et al, 2006;Svitkina et al, 1997;Wilson et al, 2010;Yang et al, 2012), which also affect the movement and bundling of microtubules (Burnette et al, 2008;Schaefer et al, 2008).…”

Cytoplasmic Linker Proteins Regulate Neuronal Polarization through Microtubule and Growth Cone Dynamics

“…Myosin II-based retrograde transport of actin filaments toward the center of the growth cone results in the generation of actin arcs (Schaefer et al, 2002) that prevent microtubules from invading the peripheral region (Burnette et al, 2008;Lee and Suter, 2008;Schaefer et al, 2008;Lowery and Van Vactor, 2009). During active growth phases, actin arcs reorient toward the growth direction, creating an F-actin-free corridor into which microtubules protrude (Lee and Suter, 2008).…”

Permeation of Fluorophore-Conjugated Phalloidin into Live Hair Cells of the Inner Ear Is Modulated by P2Y Receptors

“…Upon permeating hair cells, it specifically labels F-actin-rich cellular structures, including stereocilia, and cuticular plates. Due to phalloidin's affinity for F-actin, it is useful for investigating retrograde F-actin flow and the coordination between the actin and microtubules cytoskeletal networks advancing growth cones and neurites (Schaefer et al 2002;Burnette et al 2007Burnette et al , 2008Schaefer et al 2008). If a low enough concentration of fluorophore-conjugated phalloidin is introduced into HCs, this could provide a new method for analyzing retrograde actin flow in HCs and treadmilling rates within stereocilia (Schneider et al 2002;Zhang et al 2012).…”

“…This provides dynamic measures of localized directions and rates of Factin flow (Lin and Forscher 1995;Waterman-Storer et al 1998;Schaefer et al 2002Schaefer et al , 2008Burnette et al 2008). …”