Dia- and Rok-dependent enrichment of capping proteins in a cortical region.

Anja Schmidt,Jörg Großhans,Long Li,Zhiyi Lv,Shuling Yan

doi:10.1242/jcs.258973

Abstract

ABSTRACTRho signaling with its major targets the formin Dia, Rho kinase (Rok) and non-muscle myosin II (MyoII, encoded by zip in flies) control turnover, amount and contractility of actomyosin. Much less investigated has been a potential function for the distribution of F-actin plus and minus ends. In syncytial Drosophila embryos, Rho1 signaling is high between actin caps, i.e. the cortical intercap region. Capping protein binds to free plus ends of F-actin to prevent elongation of the filament. Capping protein has served as a marker to visualize the distribution of F-actin plus ends in cells and in vitro. In the present study, we probed the distribution of plus ends with capping protein in syncytial Drosophila embryos. We found that capping proteins are specifically enriched in the intercap region similar to Dia and MyoII but distinct from overall F-actin. The intercap enrichment of Capping protein was impaired in dia mutants and embryos, in which Rok and MyoII activation was inhibited. Our observations reveal that Dia and Rok-MyoII control Capping protein enrichment and support a model that Dia and Rok-MyoII control the organization of cortical actin cytoskeleton downstream of Rho1 signaling. This article has an associated First Person interview with the first authors of the paper.

Highlights

Underlying the plasma membrane of cells, a thin layer of cortical F-actin fulfills manifold functions such as playing a central role in cell polarity, providing a scaffold for membrane associated proteins, and ensuring mechanical stiffness, among others
Rho signaling with its major targets the formin Dia, Rho kinase (Rok) and non-muscle myosin II control turnover, amount and contractility of actomyosin
In syncytial Drosophila embryos Rho1 signaling is high between actin caps, i. e. the cortical intercap region

Summary

Introduction

Underlying the plasma membrane of cells, a thin layer of cortical F-actin fulfills manifold functions such as playing a central role in cell polarity, providing a scaffold for membrane associated proteins, and ensuring mechanical stiffness, among others. Linker proteins belonging to the ERM protein family mediate attachment of cortical F-actin to the plasma membrane. The F-actin cortex contributes to segregation of proteins and establishment of cortical domains, including polarity proteins that are crucial for formation and maintenance of cell polarity (Honigmann and Pralle, 2016; Schmidt and Grosshans, 2018). Two cortical domains mark the cap region above the nuclei and intercap region in between caps (Karr and Alberts, 1986; Warn et al, 1984). Three distinct cortical domains are observed during this process, namely apical, lateral and basal regions (Mavrakis et al, 2009)

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Discussion

Conclusion