Uwamichi, M. | Search bioRxiv

bioRxiv2024

Traveling wave chemotaxis of neutrophil-like HL-60 cells

The question of how changes in chemoattractant concentration translate into the chemotactic response of immune cells serves as a paradigm for the quantitative understanding of how cells perceive and process temporal and spatial information. Here, using a microfluidic approach, we analyzed the migration of neutrophil-like HL-60 cells to a traveling wave of the chemoattractants fMLP and leukotriene B4 (LTB4). We found that under a pulsatile wave that travels at a speed of 95 and 170 {micro}m/min, cells move forward in the front of the wave but slow down and randomly orient at the back due to temporal decrease in the attractant concentration. Under a slower wave, cells re-orient and migrate at the back of the wave; thus, cell displacement is canceled out or even becomes negative as cells chase the receding wave. FRET-based analysis indicated that these patterns of movement correlated well with spatiotemporal changes in Cdc42 activity. Furthermore, pharmacological perturbations suggested that migration in front of the wave depends on Cdc42, whereas that in the back of the wave depends more on PI3K/Rac and ROCK. These results suggest that pulsatile attractant waves may recruit or disperse neutrophils, depending on their speed and degree of cell polarization. Significance statementO_LIThe way neutrophil chemotaxis is directed by attractants is thought to depend on temporal and spatial concentration changes, however the response to a transient pulsatile stimulus has not been well explored. C_LIO_LIA moderately fast traveling wave of fMLP and leukotrieneB4 (LTB4) directs unidirectional cell migration. Under slow waves, cells respond to the back of the wave; thus, cell displacement is canceled out. Cdc42, PI3K, Rac, and ROCK contributed differently to responses at the front and back of the wave. C_LIO_LIThese findings suggest that traveling waves of attractant can guide immune cell recruitment and dispersal. C_LI

cell biology↗

bioRxiv2023

Random walk and cell morphology dynamics in Naegleria gruberi

Amoeboid cell movement and migration are wide-spread across various cell types and species. Microscopy-based analysis of the model systems Dictyostelium and neutrophils over the years have uncovered generality in their overall cell movement pattern. Under no directional cues, the centroid movement can be quantitatively characterized by their persistence to move in a straight line and the frequency of re-orientation. Mathematically, the cells essentially behave as a persistent random walker with memory of two characteristic time-scale. Such quantitative characterization is important from a cellular-level ethology point of view as it has direct connotation to their exploratory and foraging strategies. Interestingly, outside the amoebozoa and metazoa, there are largely uncharacterized species in the excavate taxon Heterolobosea including amoeboflagellate Naegleria. While classical works have shown that these cells indeed show typical amoeboid locomotion on an attached surface, their quantitative features are so far unexplored. Here, we analyzed the cell movement of Naegleria gruberi by employing long-time phase contrast imaging to automatically track individual cells. We show that the cells move as a persistent random walker with two time-scales that are close to those known in Dictyostelium and neutrophils. Similarities were also found in the shape dynamics which is characterized by the appearance, splitting and annihilation of the curvature waves along the cell edge. Our analysis based on the Fourier descriptor and a neural network classifier point to importance of morphology features unique to Naegleria including complex protrusions and the transient bipolar dumbbell morphologies.

cell biology↗