Biology subjects

Glotzer, M.

Publications and source records attributed to Glotzer, M..

3 recordsLinked to original sources

bioRxiv2018

PLK1 plays dual roles in centralspindlin regulation during cytokinesis

Cytokinesis starts in anaphase with the formation of an actomyosin-based contractile ring at the equatorial cortex, which is governed by the local activation of the small GTPase RhoA. Here we delineated the contributions of PLK1 and Aurora B to RhoA activation and cytokinesis initiation in human cells. Knock-down of PRC1, which disrupts the spindle midzone, revealed the existence of two pathways that can initiate cleavage furrow ingression. One pathway depends on a well-organized spindle midzone and PLK1, while the other depends on Aurora B activity and centralspindlin oligomerization at the equatorial cortex and can operate independently of PLK1. We further show that PLK1 inhibition sequesters centralspindlin onto the spindle midzone making it unavailable for Aurora B-dependent oligomerization at the equatorial cortex. We propose that PLK1 activity promotes the release of centralspindlin from the spindle midzone through inhibition of PRC1, allowing centralspindlin to function as a regulator of spindle midzone formation and as an activator of RhoA at the equatorial cortex.

cell biology↗

bioRxiv2017

Cell cycle entry triggers a switch between two modes of Cdc42 activation during yeast polarization

Cell polarization underlies many cellular and organismal functions. The GTPase Cdc42 orchestrates polarization in many contexts. In budding yeast, polarization is associated with a focus of Cdc42*GTP which is thought to self sustain by recruiting a complex containing Cla4, a Cdc42-binding effector, Bem1, a scaffold and Cdc24, a Cdc42 GEF. Using optogenetics, we probe yeast polarization and find that local recruitment of Cdc24 or Bem1 is sufficient to induce polarization by triggering self-sustaining Cdc42 activity. However, the response to these perturbations depends on the recruited molecule, the cell cycle stage, and existing polarization sites. Before cell cycle entry, recruitment of Cdc24, but not Bem1, induces a metastable pool of Cdc42 that is sustained by positive feedback. Upon Cdk1 activation, recruitment of either Cdc24 or Bem1 creates a stable site of polarization that induces budding and inhibits formation of competing sites. Local perturbations have therefore revealed unexpected features of polarity establishment.

cell biology↗

bioRxiv2017

Harnessing optogenetics to probe sub-cellular mechanics

The mechanics of the actin cytoskeleton regulates cell morphogenesis during essential physiological processes. While cellular contractility is known to be largely RhoA-dependent, the process by which localized biochemical signals are translated into cell-level responses is not well understood. Here we combine optogenetic control of RhoA in space and time, live cell imaging and traction force microscopy to investigate the dynamics of actomyosin-based force generation in adherent fibroblasts. Local activation of RhoA not only stimulates local recruitment of actin and myosin, but also leads to increased traction forces outside the activation region that rapidly propagate across the cell via stress fibers and drive actin flow towards the region of heightened RhoA. Surprisingly, the flow reverses direction when local RhoA activation stops. We identify zyxin as a regulator of stress fiber mechanics, as stress fibers are fluid-like without flow reversal in its absence. These experimental data are used to constrain a physical model, which demonstrates that stress fibers are elastic-like, even at time scales exceeding turnover of constituent proteins. Such molecular control of actin mechanics likely plays critical roles in regulation of morphogenic events.

biophysics↗