Myosin II isoforms play distinct roles in adherens junction biogenesis

Abstract

29Adherens junction (AJ) assembly under force is essential for many biological processes like 30 epithelial monolayer bending, collective cell migration, cell extrusion and wound healing. The 31 acto-myosin cytoskeleton acts as a major force-generator during the de novo formation and 32 remodelling of AJ. Here, we investigated the role of myosinII isoforms in epithelial junction 33 assembly. Myosin IIA (NMIIA) and Myosin IIB (NMIIB) differentially regulate biogenesis of 34 adherens junction through association with distinct actin networks. Analysis of junction 35 dynamics, actin organization, and mechanical forces of control and knockdown cells for 36 myosins revealed that NMIIA provides the mechanical tugging force necessary for cell-cell 37 junction reinforcement and maintenance. NMIIB is involved in E-cadherin clustering, 38 maintenance of a branched actin layer connecting E-cadherin complexes and perijunctional 39 actin fibres leading to the building-up of anisotropic stress. These data reveal unanticipated 40 complementary functions of NMIIA and NMIIB in the biogenesis and integrity of AJ. 41 42 Introduction 43 Tissue integrity and plasticity rely on cell-cell adhesion and cell contractility. The formation, 44 remodelling and disassembly of cell-cell adhesions are fundamental events accompanying all 45 stages of morphogenesis, tissue homeostasis and healing. Adherens junctions (AJ) mediated 46 by E-cadherin/catenin complexes are key elements of epithelial cell-cell adhesions and the 47 first ones to assemble upon contact initiation 1-3 . They provide strong mechanical coupling 48 between neighbouring cells through association with the acto-myosin cytoskeleton 4 . 49The assembly of de novo AJ is crucial for cell-cell rearrangement 5,6 , tissue closure 7 and the 50 maintenance of epithelial cell integrity during wound healing or cell extrusion 8-10 . During de 51 novo cell-cell contacts formation, initial contacts between facing lamellipodia induce immediate 52 clustering of cadherin molecules by trans-and cis-oligomerization [11][12][13][14] . Subsequent signalling 53 events involving RhoGTPases trigger local remodelling of the actin cytoskeleton through 54 Arp2/3-or formin-mediated actin polarization in the vicinity of AJs 15-17 . These cytoskeletal 55 rearrangements drive the expansion of cell-cell contacts and inter-cellular adhesion 56 strengthening 2,18,19 . 57Non-muscle Myosin II (NMII) has emerged as a fundamental player in force-generation and 58 force-transmission at AJ both in vitro and in vivo [20][21][22] . NMII is essential for epithelial tissue 59 architecture 23 , epithelial tissue morphogenesis 24 , tissue repair 25,26 and cell extrusion 27 . NMII 60 protects junctions from disassembly during development 28 and provides the mechanical 61 tugging force necessary for AJ reinforcement 29 . In endothelial cells, NMII is recruited early in 62 filopodia-mediated bridge bundles and its activity is required for accumulation of VE-cadherin 63 in nascent AJs 30 . In epithelial cells, NMII favours local...

Nonmuscle myosin 2 regulates cortical stability during sprouting angiogenesis

“…, 2010 ; Hoelzle and Svitkina, 2012 ). In cultured epithelial MDCK cells, NM2A and NM2B have been shown to function complementarily in the formation and maintenance of the integrity of adherens junctions ( Heuze et al. , 2019 ).…”

“…During adherens junction formation, NM2A and 2B are differentially localized to and stabilize the perijunctional contractile actin bundles and the juxtamembrane actin meshwork, respectively. NM2A provides the major tugging force for junction growth, while NM2B is required for E-cadherin clustering and coupling of perijunctional contractile actin to the plasma membrane, and provides the majority of intercellular stress ( Heuze et al. , 2019 ).…”

Non-Muscle Myosin 2A (NM2A): Structure, Regulation and Function

“…NM2 contractile forces are fundamental to power the contraction of the adherens junctions both in vitro and in vivo [ 115 , 116 ], having a key role in the establishment of polarized epithelial tissues [ 117 ]. In particular, NM2A contractile activity is required for the assembly, maturation and temporal stability of adhesion complexes [ 12 , 118 , 119 ]. In intestinal epithelial cells, depletion of NM2A by siRNA results in the disruption of cell–cell adhesion and induces profound alterations on cell morphology [ 120 ].…”

“…In intestinal epithelial cells, depletion of NM2A by siRNA results in the disruption of cell–cell adhesion and induces profound alterations on cell morphology [ 120 ]. In kidney epithelial cells, NM2A knockdown shortens adhesion contacts and disrupts stable intercellular adhesions [ 119 ]. In line, NM2A ablation in mice decreased the levels of E-cadherin and β-catenin at the adhesion sites leading to the loss of cell–cell contacts [ 89 ].…”

Multiscale morphogenesis of the mouse blastocyst by actomyosin contractility

“…The spatio-temporal regulation of contractility patterns the stresses at the surface of animal cells and drives several key cellular processes. For example, stronger contractility at the cleavage furrow cleaves cells into two during cytokinesis [23]; contractility at the back of migrating cells help them retract their cell body [24]; weaker contractility at cell-cell contacts relaxes them and promotes their spreading [25,26]. Importantly, surface stresses generated by contractility can be controlled across multiple scales: from the subcellular [27] to the tissue levels [28] and from seconds [29] to hours [17].…”