Mesenchymal Chemotaxis Requires Selective Inactivation of Myosin II at the Leading Edge via a Noncanonical PLCγ/PKCα Pathway

Abstract

Summary Chemotaxis, migration towards soluble chemical cues, is critical for processes such as wound healing and immune surveillance, and is exhibited by various cell types from rapidly-migrating leukocytes to slow-moving mesenchymal cells. To interrogate the mechanisms involved in mesenchymal chemotaxis, we observed cell migration in microfluidic chambers that generate stable gradients of the chemoattractant PDGF. Surprisingly, we found that pathways implicated in amoeboid chemotaxis, such as PI3K and mTOR signaling, are dispensable for chemotaxis to PDGF. Instead, we find that local inactivation of Myosin IIA, through a non-canonical Ser1/2 phosphorylation of the regulatory light chain, is essential. This site is phosphorylated by PKCα, which is activated by an intracellular gradient of diacylglycerol generated by PLCγ. Using a combination of TIRF imaging and gradients of activators/inhibitors in the microfluidic chambers, we demonstrate that this signaling pathway and subsequent inhibition of Myosin II activity at the leading edge is required for mesenchymal chemotaxis.

Engulfed cadherin fingers are polarized junctional structures between collectively migrating endothelial cells

“…Together, a potential turning mechanism mediated by cadherin fingers and low myosin activity is reminiscent of a guidance mechanism in mesenchymal cells, where localized inactivation of myosin II at the leading edge has been shown to correlate with chemotaxis towards growth factor 34 .…”

Tumor Cell–Driven Extracellular Matrix Remodeling Drives Haptotaxis during Metastatic Progression

“…Using a recently developed microfluidic device, we studied cells migrating on FN gradients by time-lapse imaging, and quantified their forward migration index (FMI) to assess haptotaxis (Fig1A) (19,20). First, MV D7 fibroblasts, which lack all three Ena/VASP proteins (Mena, VASP and EVL(21)) migrated actively in the device, however, they failed to haptotax on the FN gradient.…”

“…The tracks obtained were analyzed using the Chemotaxis Tool ImageJ plugin (from Ibidi). This analysis tool was used to extract the FMI (Fig 1A) along with the velocity of migration and the persistence of migration using the D/T ratio (net path length/total path length) (20,44). …”

Naturally occurring PDGF receptor inhibitors with potential anti-atherosclerotic properties

“…Surprisingly, this complex is dispensable for chemotaxis toward PDGF or EGF by mesenchymal cells [48]. Indeed, PDGFR activation recruits PLCγ and generates a localized intracellular gradient of diacylglycerol (DAG) that, by regulating the function of PKCα and a Myosin II, provides the asymmetric force needed for directional migration [49]. These findings represent a new important insight on the signaling cascade, and molecular effectors, implicated in chemotaxis of mesenchymal cells including SMCs.…”