Polarisome assembly mediates actin remodeling during polarized yeast and fungal growth

ABSTRACTDynamic assembly and remodeling of actin is critical for many cellular processes during development and stress adaptation. In filamentous fungi and budding yeast, actin cables align in a polarized manner along the mother-to-daughter cell axis, and are essential for the establishment and maintenance of polarity; moreover, they rapidly remodel in response to environmental cues to achieve an optimal system response. A formin at the tip region within a macromolecular complex, called the polarisome, is responsible for driving actin cable polymerization during polarity establishment. This polarisome undergoes dynamic assembly through spatial and temporally regulated interactions between its components. Understanding this process is important to comprehend the tuneable activities of the formin-centered nucleation core, which are regulated through divergent molecular interactions and assembly modes within the polarisome. In this Review, we focus on how intrinsically disordered regions (IDRs) orchestrate the condensation of the polarisome components and the dynamic assembly of the complex. In addition, we address how these components are dynamically distributed in and out of the assembly zone, thereby regulating polarized growth. We also discuss the potential mechanical feedback mechanisms by which the force-induced actin polymerization at the tip of the budding yeast regulates the assembly and function of the polarisome.

Download Full-text

Investigation into Early Steps of Actin Recognition by the Intrinsically Disordered N-WASP Domain V

International Journal of Molecular Sciences ◽

10.3390/ijms20184493 ◽

2019 ◽

Vol 20 (18) ◽

pp. 4493 ◽

Cited By ~ 1

Author(s):

Maud Chan-Yao-Chong ◽

Dominique Durand ◽

Tâp Ha-Duong

Keyword(s):

Conformational Changes ◽

Actin Polymerization ◽

High Specificity ◽

Physical Factors ◽

Consensus Sequences ◽

Recognition Process ◽

Intrinsically Disordered ◽

Intrinsically Disordered Regions ◽

Dynamics Simulations ◽

Domain V

Cellular regulation or signaling processes are mediated by many proteins which often have one or several intrinsically disordered regions (IDRs). These IDRs generally serve as binders to different proteins with high specificity. In many cases, IDRs undergo a disorder-to-order transition upon binding, following a mechanism between two possible pathways, the induced fit or the conformational selection. Since these mechanisms contribute differently to the kinetics of IDR associations, it is important to investigate them in order to gain insight into the physical factors that determine the biomolecular recognition process. The verprolin homology domain (V) of the Neural Wiskott–Aldrich Syndrome Protein (N-WASP), involved in the regulation of actin polymerization, is a typical example of IDR. It is composed of two WH2 motifs, each being able to bind one actin molecule. In this study, we investigated the early steps of the recognition process of actin by the WH2 motifs of N-WASP domain V. Using docking calculations and molecular dynamics simulations, our study shows that actin is first recognized by the N-WASP domain V regions which have the highest propensity to form transient α -helices. The WH2 motif consensus sequences “LKKV” subsequently bind to actin through large conformational changes of the disordered domain V.

Download Full-text

A teamwork promotion of formin-mediated actin nucleation by Bud6 and Aip5 in Saccharomyces cerevisiae

Molecular Biology of the Cell ◽

10.1091/mbc.e21-06-0285 ◽

2021 ◽

Author(s):

Ying Xie ◽

Feng Zhou ◽

Qianqian Ma ◽

Lanyuan Lu ◽

Yansong Miao

Keyword(s):

Actin Polymerization ◽

Protein Complexes ◽

Budding Yeast ◽

Intramolecular Interactions ◽

Functional Protein ◽

Actin Nucleation ◽

Intrinsically Disordered ◽

Multiple Partners ◽

Functional Complex ◽

Actin Nucleator

Actin nucleation is achieved by collaborative teamwork of actin nucleator factors (NFs) and nucleation-promoting factors (NPFs) into functional protein complexes. Selective inter- and intramolecular interactions between the nucleation complex constituents enable diverse modes of complex assembly in initiating actin polymerization upon demand. Budding yeast has two formins, Bni1 and Bnr1, which are teamed up with different NPFs. However, the selective pairing between formin NFs and NPFs into the nucleation core for actin polymerization is not completely understood. By examining the functions and interactions of NPFs and NFs via biochemistry, genetics, and mathematical modeling approaches, we found that two NPFs, Aip5 and Bud6, showed joint teamwork effort with Bni1 and Bnr1, respectively, by interacting with the C-terminal intrinsically disordered region (IDR) of formin, in which two NPFs work together to promote formin-mediated actin nucleation. Although the C-terminal IDRs of Bni1 and Bnr1 are distinct in length, each formin IDR orchestrates the recruitment of Bud6 and Aip5 cooperatively by different positioning strategies to form a functional complex. Our study demonstrated the dynamic assembly of the actin nucleation complex by recruiting multiple partners in budding yeast, which may be a general feature for effective actin nucleation by formins. [Media: see text]

Download Full-text

Polarisome scaffolder Spa2-mediated macromolecular condensation of Aip5 for actin polymerization

Nature Communications ◽

10.1038/s41467-019-13125-1 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 5

Author(s):

Ying Xie ◽

Jialin Sun ◽

Xiao Han ◽

Alma Turšić-Wunder ◽

Joel D. W. Toh ◽

...

Keyword(s):

Phase Separation ◽

Cell Growth ◽

Actin Polymerization ◽

Stress Conditions ◽

Scaffolding Protein ◽

Actin Assembly ◽

Intrinsically Disordered ◽

Actin Cables

Abstract A multiprotein complex polarisome nucleates actin cables for polarized cell growth in budding yeast and filamentous fungi. However, the dynamic regulations of polarisome proteins in polymerizing actin under physiological and stress conditions remains unknown. We identify a previously functionally unknown polarisome member, actin-interacting-protein 5 (Aip5), which promotes actin assembly synergistically with formin Bni1. Aip5-C terminus is responsible for its activities by interacting with G-actin and Bni1. Through N-terminal intrinsically disordered region, Aip5 forms high-order oligomers and generate cytoplasmic condensates under the stresses conditions. The molecular dynamics and reversibility of Aip5 condensates are regulated by scaffolding protein Spa2 via liquid-liquid phase separation both in vitro and in vivo. In the absence of Spa2, Aip5 condensates hamper cell growth and actin cable structures under stress treatment. The present study reveals the mechanisms of actin assembly for polarity establishment and the adaptation in stress conditions to protect actin assembly by protein phase separation.

Download Full-text

Roles of type II myosin and a tropomyosin isoform in retrograde actin flow in budding yeast

The Journal of Cell Biology ◽

10.1083/jcb.200609155 ◽

2006 ◽

Vol 175 (6) ◽

pp. 957-969 ◽

Cited By ~ 59

Author(s):

Thomas M. Huckaba ◽

Thomas Lipkin ◽

Liza A. Pon

Keyword(s):

Actin Polymerization ◽

Budding Yeast ◽

Type Ii ◽

Retrograde Flow ◽

Cortical Actin ◽

Actin Networks ◽

Actin Cable ◽

Intracellular Movement ◽

Actin Cables ◽

Type Ii Myosin

Retrograde flow of cortical actin networks and bundles is essential for cell motility and retrograde intracellular movement, and for the formation and maintenance of microvilli, stereocilia, and filopodia. Actin cables, which are F-actin bundles that serve as tracks for anterograde and retrograde cargo movement in budding yeast, undergo retrograde flow that is driven, in part, by actin polymerization and assembly. We find that the actin cable retrograde flow rate is reduced by deletion or delocalization of the type II myosin Myo1p, and by deletion or conditional mutation of the Myo1p motor domain. Deletion of the tropomyosin isoform Tpm2p, but not the Tpm1p isoform, increases the rate of actin cable retrograde flow. Pretreatment of F-actin with Tpm2p, but not Tpm1p, inhibits Myo1p binding to F-actin and Myo1p-dependent F-actin gliding. These data support novel, opposing roles of Myo1p and Tpm2 in regulating retrograde actin flow in budding yeast and an isoform-specific function of Tpm1p in promoting actin cable function in myosin-driven anterograde cargo transport.

Download Full-text

Tandem repeats drive variation of intrinsically disordered regions in budding yeast

10.1101/339663 ◽

2018 ◽

Cited By ~ 3

Author(s):

Michael Babokhov ◽

Bradley I. Reinfeld ◽

Kevin Hackbarth ◽

Yotam Bentov ◽

Stephen M. Fuchs

Keyword(s):

Protein Function ◽

Copy Number ◽

Tandem Repeats ◽

Budding Yeast ◽

Amino Acid Sequences ◽

Length Variation ◽

Intrinsically Disordered ◽

Intrinsically Disordered Regions ◽

Highly Correlated ◽

Disordered Regions

AbstractCopy-number variation in tandem repeat coding regions is more prevalent in eukaryotic genomes than current literature suggests. We have reexamined the genomes of nearly 100 yeast strains looking to map regions of repeat variation. From this analysis we have identified that length variation is highly correlated to intrinsically disordered regions (IDRs). Furthermore, the majority of length variation is associated with tandem repeats. These repetitive regions are rich in homopolymeric amino acid sequences but nearly half of the variation comes from longer-repeating motifs. Comparisons of repeat copy number and sequence between strains of budding yeast as well as closely related fungi suggest selection for and conservation of IDR-related tandem repeats. In some instances, repeat variation has been demonstrated to mediate binding affinity, aggregation, and protein stability. With this analysis, we can identify proteins for which repeat variation may play conserved roles in modulating protein function.

Download Full-text