Reconstruction of Par polarity in apolar cells reveals a dynamic process of cortical polarization

Abstract

1

Induction of cortical Par complex polarity by designed proteins causes cytoskeletal symmetry breaking in unpolarized mammalian cells

“…S3). Thus, our work generalizes previous pioneering work on the reconstitution of cortical polarity, which was either limited to fly cells (Johnston et al, 2009;Kono et al, 2019), or required external input via optogenetics (Okumura et al, 2018) and was thus restricted to single cells. Furthermore, a key advantage of our method is that since cortical targeting of the protein of interest is indirect via a nanobody, it allows independent control of the expression of the transmembrane segment, which controls the size of the clusters (Ben-Sasson et al, 2021), and that of the protein of interest, which is important for the stoichiometry of multiprotein complexes (Derivery and Gautreau, 2010)(Fig.…”

“…Finally, while it is well established that the Par complex clusters at cell-cell junctions in polarized cells (Pickett et al, 2019), and that Par complex caps are formed of coalesced clusters (Kono et al, 2019), the specific contribution of clustering to Par complex assembly is not understood.…”

Switching states: dynamic remodelling of polarity complexes as a toolkit for cell polarization

“…PAR-2 and Par3 form homo-oligomers [30,38], while PAR-1 and the related MARK kinases are thought to require coincident binding to plasma membrane lipids along with additional accessory factors, such as the C. elegans PAR-2 protein, to achieve maximal membrane enrichment [31]. In the case of Par3, it is precisely these higher-order, multivalent interactions that allow formation of stable, slow-diffusing, membrane-associated clusters that are segregated by cortical flows as discussed above and which likely play a role in numerous systems [38,39].…”

“…PAR-2 and Par3 form homo-oligomers [ 30 , 38 ], while PAR-1 and the related MARK kinases are thought to require coincident binding to plasma membrane lipids along with additional accessory factors, such as the C. elegans PAR-2 protein, to achieve maximal membrane enrichment [ 31 ]. In the case of Par3, it is precisely these higher-order, multivalent interactions that allow formation of stable, slow-diffusing, membrane-associated clusters that are segregated by cortical flows as discussed above and which likely play a role in numerous systems [ 38 , 39 ]. Assembly of complexes then becomes an additional point for regulating switching between fast cytoplasmic and slow membrane-associated states, with aPKC proposed to disfavor PAR-2 oligomerization [ 30 ] and PAR-1/PAR-2 heterodimer formation [ 31 ], and PAR-1 impeding PAR-3 clusters [ 28 ].…”

The apical polarity network in C. elegans larval epithelia

“…At least two mechanisms can contribute to membrane localization of Par3. First, the N-terminal conserved region (CR1) mediates homo-oligomeri- 32 33 zation of Par3/Baz, which promotes the formation of cortical Par3-Par6-aPKC clusters and has been reported to be essential for Par3 localization (Dickinson et al, 2017;Harris, 2017;Kono et al, 2019;Rodriguez et al, 2017;Wang et al, 2017). Second, a C-terminal lipid binding (LB) domain promotes membrane localization through binding to phospholipids (Claret et al, 2014;Horikoshi et al, 2011;Krahn et al, 2010a).…”