Microenvironmental control of cell migration: Myosin IIA is required for efficient migration in fibrillar environments through control of cell adhesion dynamics

Abstract

SummaryRecent evidence suggests that organization of the extracellular matrix (ECM) into aligned fibrils or fibril-like ECM topographies promotes rapid migration in fibroblasts. However, the mechanisms of cell migration that are altered by these changes in microenvironmental topography remain unknown. Here, using 1D fibrillar migration as a model system for oriented fibrillar 3D matrices, we find that fibroblast leading-edge dynamics are enhanced by 1D fibrillar micropatterns and demonstrate a dependence on the spatial positioning of cell adhesions. Although 1D, 2D and 3D matrix adhesions have similar assembly kinetics, both 1D and 3D adhesions are stabilized for prolonged periods, whereas both paxillin and vinculin show slower turnover rates in 1D adhesions. Moreover, actin in 1D adhesions undergoes slower retrograde flow than the actin that is present in 2D lamellipodia. These data suggest an increase in mechanical coupling between adhesions and protrusive machinery. Experimental reduction of contractility resulted in the loss of 1D adhesion structure and stability, with scattered small and unstable adhesions, and an uncoupling of adhesion protein-integrin stability. Genetic ablation of myosin IIA (MIIA) or myosin IIB (MIIB) isoforms revealed that MIIA is required for efficient migration in restricted environments as well as adhesion maturation, whereas MIIB helps to stabilize adhesions beneath the cell body. These data suggest that restricted cell environments, such as 1D patterns, require cellular contraction through MIIA to enhance adhesion stability and coupling to integrins behind the leading edge. This increase in mechanical coupling allows for greater leading-edge protrusion and rapid cell migration.

The Number of Lines a Cell Contacts and Cell Contractility Drive the Efficiency of Contact Guidance

“…The fastest reported 2D migration speed was ~35 m/hr. The authors argue this enhanced migration rate is most likely due to alterations in adhesion stability and mechanical coupling between the cytoskeleton and FAs (Doyle et al, 2012;Doyle et al, 2009). Our cell migration speeds on contact guidance substrates are roughly similar or…”

“…For whatever reason, different pathways might regulate polarity or cell migration speed in 2D leading to a different dependence. Indeed, the cytoskeleton and FAs operate much differently between 1D and 2D (Doyle et al, 2012;Doyle et al, 2009). …”

Myosin IIA Heavy Chain Phosphorylation Mediates Adhesion Maturation and Protrusion in Three Dimensions

“…In contrast to this variable importance of NMIIA for 2D migration, evidence is consistent (i) in that the NMIIA isoform shows strong recruitment to anterior protrusions during 2D migration and (ii) that NMIIA has a strong and isoform-specific role in stabilizing nascent focal adhesions at the anterior of cells migrating in 2D (14,30,(43)(44)(45). We hypothesized that the limited and variable impact of NMIIA depletion on migration rate in 2D studies may relate to the lack of resistance a cell encounters during 2D migration on rigid surfaces.…”

“…The three isoforms have distinct expression patterns in tissues (10) and distinct biochemical properties (11,12), suggesting unique roles in cellular processes. For example, during mesenchymal migration in 2D settings, NMIIA activity stabilizes anterior focal adhesions via unknown mechanisms, facilitating attachment of the anterior portion of the cell to the extracellular environment (13,14). In both amoeboid and mesenchymal modes of migration, as well as a recently reported "piston" mode of migration, NMII activity is critical for anterior translocation of the nucleus through tight spaces (15)(16)(17).…”

Protein conformation as a regulator of cell–matrix adhesion

“…145,170 In the context of adhesion disassembly, one needs to keep in mind that under 2D cell culture conditions the cells are able to sense many more extracellular ligands than are required for cell spreading and adhesion. 171 Furthermore, in a 3D or 1D culture system, the equilibrium between adhesion assembly and disassembly appears to be more dynamic than in 2D, 172 controlled by cellular contractility, 173 and more responsive to differential integrin adapter signaling. 174 However at this point, the amount of mechanistic data is still limited.…”