MSc Exit Seminar – Erin Hunt (Harris Lab)

SCAR/WAVE and Arp2/3 Complexes Associate with a Supra-Cellular Actomyosin Cable in Response to Myosin and a Cytohesin Arf-GEF

Abstract

Expansive Arp2/3 actin networks and contractile actomyosin networks were once viewed as antagonistic assemblies with spatially and temporally distinct distributions within the cell. More recently, Arp2/3 and actomyosin networks were found to closely interact during cell migration, adhesion and epithelial remodeling.  However, molecular mechanisms responsible for coordinating the networks remain unclear.  Here, I show that the Arp2/3 complex and its activator, the SCAR/WAVE complex, are enriched at cell-cell junctions of a supra-cellular actomyosin cable found at the leading edge (LE) of epidermal sheets during dorsal closure (DC) of the Drosophila embryo. Myosin activity is both necessary and sufficient for these accumulations of the SCAR/WAVE complex. Myosin has previously been shown to promote localization of the cytohesin Arf-GEF Steppke (Step) to these sites.  Strikingly, I find that Step is required for the enrichment of the SCAR/WAVE complex.  Partial SCAR loss does not dramatically alter LE actin enrichment, as might be expected, but does result in LE shape irregularities.  Genetic interactions between step mutants and those of SCAR and Arp3 further indicate a role for the SCAR/WAVE and Arp2/3 complexes in DC.  My data suggests myosin activity acts through Step to recruit the SCAR/WAVE and Arp2/3 complexes to promote actin network growth that may be important for actomyosin cable function during DC.

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Join Zoom Meeting

https://utoronto.zoom.us/j/85682403987

Meeting ID: 856 8240 3987

Host: Tony Harris (tony.harris@utoronto.ca)

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