Self-organizing glycolytic waves fuel cell migration and cancer progression

Symmetry breaking, polarity establishment, and spontaneous cell protrusion formation are fundamental but poorly explained cell behaviors. Here, we demonstrate that a biochemical network, where the mutually inhibitory localization of PIP5K and Ras activities plays a central role, governs these processes. First, in resting cells devoid of cytoskeletal activity, PIP5K is uniformly elevated on the plasma membrane, while Ras activity remains minimal. Symmetry is broken by spontaneous local displacements of PIP5K, coupled with simultaneous activations of Ras and downstream signaling events, including PI3K activation. Second, knockout of PIP5K dramatically increases both the incidence and size of Ras-PI3K activation patches, accompanied by branched F-actin assembly. This leads to enhanced cortical wave formation, increased protrusive activity, and a shift in migration mode. Third, high inducible overexpression of PIP5K virtually eliminates Ras-PI3K signaling, cytoskeletal activity, and cell migration, while acute recruitment of cytosolic PIP5K to the membrane induces contraction and blebs in cancer cells. These arrested phenotypes are reversed by reducing myosin II activity, indicating myosin’s involvement in the PIP5K-Ras-centered regulatory network. Remarkably, low inducible overexpression of PIP5K unexpectedly facilitates polarity establishment, highlighting PIP5K as a highly sensitive master regulator of these processes. Simulations of a computational model combining an excitable system, cytoskeletal loops, and dynamic partitioning of PIP5K recreates the experimental observations. Taken together, our results reveal that a bistable, mutually exclusive localization of PIP5K and active Ras on the plasma membrane triggers the initial symmetry breaking. Coupled actomyosin reduction and increased actin polymerization lead to intermittently extended protrusions and, with feedback from the cytoskeleton, self-organizing, complementary gradients of PIP5K versus Ras steepen, raising the threshold of the networks at the rear and lowering it at the front to generate polarity for cell migration.

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A role for class I PAKs in the regulation of the excitability of the actin cytoskeleton

Tyler,

Davidson,

Poxon

et al. 2024

Preprint

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P21 activated kinases (PAKs) are involved in a wide range of functions from the regulation of the cytoskeleton to the control of apoptosis and proliferation. Although many PAK substrates identified are implicated in the regulation of the actin cytoskeleton, a coherent picture of the total effect of PAK activation on the state of the actin cytoskeleton is unclear. We therefore set out to observe and quantify the effect of PAK inhibition on the actin cytoskeleton in greater detail. In Mouse Embryonic Fibroblasts, inhibition of PAK kinase activity, either by treatment with small molecule inhibitors or overexpression of mutant PAK constructs leads to the constitutive production of patches of the phosphoinositide PIP3 on the ventral surface of the cell. The formation of these patches remodels the actin cytoskeleton and polarises the cell. From the overexpression of truncated and mutant PAK constructs as well as an in vitro model of PAK recruitment to small GTPases we propose that this is due to a hyper recruitment of PAK and PAK binding partners in the absence of PAK kinase activity. This aberrant production of PIP3 suggests that the kinase activity of class I PAKs acts to downregulate PI3K activity further highlighting class I PAKs as regulators of PI3K activity and therefore the excitability of the actin cytoskeleton.

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Self-organizing glycolytic waves fuel cell migration and cancer progression

Cited by 3 publications

References 59 publications

Ras suppression potentiates rear actomyosin contractility-driven cell polarization and migration

Ras suppression potentiates rear actomyosin contractility-driven cell polarization and migration

PIP5K-Ras bistability initiates plasma membrane symmetry breaking to regulate cell polarity and migration

A role for class I PAKs in the regulation of the excitability of the actin cytoskeleton

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