Rectified directional sensing in long-range cell migration

Chemotaxis, the directional migration of cells in a chemical gradient, is robust to fluctuations associated with low chemical concentrations and dynamically changing gradients as well as high saturating chemical concentrations. Although a number of reports have identified cellular behavior consistent with a directional memory that could account for behavior in these complex environments, the quantitative and molecular details of such a memory process remain unknown. Using microfluidics to confine cellular motion to a 1D channel and control chemoattractant exposure, we observed directional memory in chemotactic neutrophil-like cells. We modeled this directional memory as a long-lived intracellular asymmetry that decays slower than observed membrane phospholipid signaling. Measurements of intracellular dynamics revealed that moesin at the cell rear is a longlived element that when inhibited, results in a reduction of memory. Inhibition of ROCK (Rho-associated protein kinase), downstream of RhoA (Ras homolog gene family, member A), stabilized moesin and directional memory while depolymerization of microtubules (MTs) disoriented moesin deposition and also reduced directional memory. Our study reveals that long-lived polarized cytoskeletal structures, specifically moesin, actomyosin, and MTs, provide a directional memory in neutrophil-like cells even as they respond on short time scales to external chemical cues. . In particular, chemical cues activate signaling at the cell surface and are integrated within the cell cytoplasm to give rise to a polarization in the direction of the local gradient. Although these processes have been the subject of detailed experimental study and theoretical and computational modeling, the mechanisms by which this orientation is achieved and maintained in the face of environmental noise remains incomplete.Although migration might be thought of as being very sensitive to the variations in the external environment, instead, we see robust migration in a variety of fluctuating environments. These observations all point to the existence of a directional memory in chemotactic cells-a biochemical pathway that stores information about cellular orientation and prevents the loss of orientation in the face of fluctuations, transient loss of polarization, or saturation of the receptors. For example, recent work has demonstrated memory-based behavior in Dictyostelium amoebae under fluctuating waves of chemoattractant (6, 7), although the authors do not identify potential molecular elements that store this information.Here, we use microchannel-based microfluidic devices to observe cell polarization and movement in confined mammalian neutrophil-like cells. Cells in this environment exhibit a strong bias to repolarize in the previous direction of motion after a period of depolarization. This memory is time-dependent and decays when the cell is unstimulated. To describe these results, we construct a minimal phenomenological model coupling membrane and cytoskeletal polarization lifetimes and show that thi...

Section: Resultsmentioning

confidence: 87%

mentioning

confidence: 99%

Directional memory arises from long-lived cytoskeletal asymmetries in polarized chemotactic cells

Prentice-Mott

Meroz

Carlson

et al. 2016

“…In general, a response to a step stimulus may not necessarily have the same propensity as that for a slowly varying stimulus. Moreover, directional migration is induced by a traveling-wave stimulus (17,18) and thus may affect the cAMP relay owing to a large overlap in the signal transduction network (16,31,32). To test relevance of the fold-change response property for natural cAMP wave, we used a microfluidics lighthouse (33)-a gradient-generating platform capable of delivering traveling-wave stimulus of various amplitude, frequencies, and speed.…”

Section: Resultsmentioning

confidence: 99%

“…This tendency for the extracellular cAMP level to rise when it is lowered, and to be lowered when it is raised, essentially renders extracellular cAMP level unstable and oscillatory. The emerging oscillatory waves of extracellular cAMP in the cell population provide a temporal guidance cue for directional cell migration (17,18). Both cAMP oscillations and cell aggregation are known to occur at a wide range of cell densities spanning at least two to three orders of magnitude (19)(20)(21)(22).…”

mentioning

confidence: 99%

Fold-change detection and scale invariance of cell–cell signaling in social amoeba

Kamino

Kondo

Nakajima

et al. 2017

Self Cite

Cell-cell signaling is subject to variability in the extracellular volume, cell number, and dilution that potentially increase uncertainty in the absolute concentrations of the extracellular signaling molecules. To direct cell aggregation, the social amoebae Dictyostelium discoideum collectively give rise to oscillations and waves of cyclic adenosine 3′,5′-monophosphate (cAMP) under a wide range of cell density. To date, the systems-level mechanism underlying the robustness is unclear. By using quantitative live-cell imaging, here we show that the magnitude of the cAMP relay response of individual cells is determined by fold change in the extracellular cAMP concentrations. The range of cell density and exogenous cAMP concentrations that support oscillations at the population level agrees well with conditions that support a large fold-change-dependent response at the singlecell level. Mathematical analysis suggests that invariance of the oscillations to density transformation is a natural outcome of combining secrete-and-sense systems with a fold-change detection mechanism.fold-change detection | oscillations | collective behavior | Dictyostelium | robustness C ell-cell signaling lies at the basis of development and maintenance of multicellular forms of life. Extracellular signals are often subject to greater fluctuations in the size of extracellular space and the number of cells (Fig. 1A), not to mention nonspecific binding to other molecules, degradation, and dilution. These factors introduce an uncertainty to the detectable number of extracellular ligand molecules, thus posing a threat to the fidelity of cell-cell communication. One of the means by which cells could cope with such uncertainties is to base their behavioral decisions on temporal changes in the extracellular signals. Persistent stimuli are often ignored while their changes in time elicit transient responses-a property collectively called adaptation (1-3). Recent studies have highlighted cellular response whose magnitude appears to be dictated by the fold change in the input stimuli-a property referred to as "fold-change detection" (FCD) (4, 5). In bacterial chemotaxis, cells respond adaptively to a fold change in chemoattractant concentration (6) so that their search patterns depend only on the spatial profiles of the chemoattractant irrespective of its absolute level. Fold-change dependence is also implied in eukaryotic chemotactic response (7, 8) as well as cell fate control and gene regulation in Xenopus embryo (9), Drosophila imaginal disk (10), and mammalian cells (11). These studies have shed light on the role of FCD for a simple unidirectional signal transduction from an extracellular ligand-receptor interaction (input) to a cellular response (output). However, cell-cell signaling and multicellular systems as a whole often use secretion and sensing of the same molecules (12), whereby the output is fed back to the responding cell itself in addition to the neighboring cells, thus forming a complex bidirectional signal transduction system. Th...

“…Finally, cells with stable front and back regions, even in the absence of directional cues, exhibit a "persistent" polarity that can be augmented by chemoattractants. Such persistent polarity enhances directionality during migration, allowing cells to chemotax more efficiently in steady gradients, but impairs responsiveness to shifting gradients (15,58,59). Undoubtedly, overlapping networks of components are involved in these various events.…”

Section: Discussionmentioning

confidence: 99%

Novel protein Callipygian defines the back of migrating cells

Swaney

Borleis

Iglesias

et al. 2015

Asymmetric protein localization is essential for cell polarity and migration. We report a novel protein, Callipygian (CynA), which localizes to the lagging edge before other proteins and becomes more tightly restricted as cells polarize; additionally, it accumulates in the cleavage furrow during cytokinesis. CynA protein that is tightly localized, or "clustered," to the cell rear is immobile, but when polarity is disrupted, it disperses throughout the membrane and responds to uniform chemoattractant stimulation by transiently localizing to the cytosol. These behaviors require a pleckstrin homology-domain membrane tether and a WD40 clustering domain, which can also direct other membrane proteins to the back. Fragments of CynA lacking the pleckstrin homology domain, which are normally found in the cytosol, localize to the lagging edge membrane when coexpressed with full-length protein, showing that CynA clustering is mediated by oligomerization. Cells lacking CynA have aberrant lateral protrusions, altered leading-edge morphology, and decreased directional persistence, whereas those overexpressing the protein display exaggerated features of polarity. Consistently, actin polymerization is inhibited at sites of CynA accumulation, thereby restricting protrusions to the opposite edge. We suggest that the mutual antagonism between CynA and regions of responsiveness creates a positive feedback loop that restricts CynA to the rear and contributes to the establishment of the cell axis.chemotaxis | polarity | asymmetry | Dictyostelium | protein localization