Microtubules restrict F-actin polymerization to the immune synapse via GEF-H1 to maintain polarity in lymphocytes

Abstract

Immune synapse formation is a key step for lymphocyte activation. In B lymphocytes, the immune synapse controls the production of high-affinity antibodies, thereby defining the efficiency of humoral immune responses. While the key roles played by both the actin and microtubule cytoskeletons in the formation and function of the immune synapse have become increasingly clear, how the different events involved in synapse formation are coordinated in space and time by actin-microtubule interactions is not understood. Using a microfluidic pairing device, we studied with unprecedented resolution the dynamics of the various events leading to immune synapse formation and maintenance. Our results identify two groups of events, local and global dominated, respectively, by actin and microtubules dynamics. They further highlight an unexpected role for microtubules and the GEF-H1-RhoA axis in restricting F-actin polymerization at the immune synapse to define the cell polarity axis, allowing the formation and maintenance of a unique competent immune synapse.

Phenotyping Polarization Dynamics of Immune Cells Using a Lipid Droplet - Cell Pairing Microfluidic Platform

“…We could not access whether there is antigen internalization from the droplets. However, in a recent work we show that there is, at least on stiff droplets, exocysts enrichment at the synapse, a signature of proteases release (44). Future efforts will be directed to make droplets where mechanical extraction is possible.…”

Plasma membrane topography governs the 3D dynamic localization of IgM B cell antigen receptor clusters

“…In our experiments, LatA did not induce the formation of the static protrusive structure when the microtubule cytoskeleton was depolymerized priorly, an observation in line with Obino et al (2016). Microtubule‐mediated polarity cues for protrusion formation could involve regulating the phosphoinositide content of the plasma membrane (Golub & Caroni, 2005; Sugiyama et al , 2015), asymmetrically activating Rho signaling (Pineau et al , 2022) or providing direct interaction with membrane‐bending factors (Kelley et al , 2015). We think that, once these factors, likely to belong to the BAR protein superfamily, stably bind and bend membranes in the absence of actin cytoskeleton, subsequent microtubule depolymerization is no longer effective.…”