Type V Myosin focuses the polarisome and shapes the tip of yeast cells

Abstract

<jats:title>Abstract</jats:title><jats:p>The polarisome is a cortical proteinaceous micro-compartment that organizes the growth of actin filaments and the fusion of secretory vesicles in yeasts and filamentous fungi. Polarisomes are compact, spot-like structures at the growing tips of their respective cells. The molecular forces that control form and size of this micro-compartment are not known. Here we identify a complex between the polarisome subunit Pea2 and the type V Myosin Myo2 that anchors Myo2 at the cortex of yeast cells. We discovered a point mutation in the cargo-binding domain of Myo2 that impairs the interaction with Pea2 and consequently the formation and focused localization of the polarisome. Cells carrying this mutation grow round instead of elongated buds. Further experiments and biophysical modeling suggest that polarisome nanoparticles use multiple copies of Myo2 and an actin filament polymerizing activity to drive the assembly of the polarisome and sustain its compact shape.</jats:p>

A focus on yeast mating: From pheromone signaling to cell-cell fusion

“…4A). Within the polarisome, the direct interaction of Pea2 and Myo2 [119] and condensate formation by Spa2 [120] suggest possible mechanisms for focusing the actin structure underlying vesicle clustering.…”

Transient septin sumoylation steers a Fir1-Skt5 protein complex between the split septin ring

“…The polarisome scaffold Spa2 and other subunits of the polarisome were discovered as novel interaction partners of Fir1 (Fig. 2A) (Neller et al, 2015; Tcheperegine et al, 2005; Shih et al, 2005; Dunkler et al, 2021; Valtz and Herskowitz, 1996).…”

Artificial Hsp100-mediated systems for re-localizing protein aggregates

“…S1A). In a second attempt, we instead fused Hsp104-GFP to Pea2, a protein component that is transported with Myo2 along actin cables to the polarisome protein complex at the tip of the bud ( 37 ). The HSP104-GFP-PEA2 fusion gene was integrated genomically into the MET15 locus, leaving the endogenous HSP104 and PEA2 genes unaltered (Fig.…”

“…S1A). In a second attempt, we instead fused Hsp104-GFP to Pea2, a protein component that is transported with Myo2 along actin cables to the polarisome protein complex at the tip of the bud (37).…”