How does the cytoskeleton drive signaling?
The powerful combination of artificial lipid bilayers and total internal reflection microscopy showed us that cells polymerize actin and form surface microclusters of BCR and antigen as they spread. BCR engagement triggers the activation of a small GTPase called Rac2, which in turn activates the adhesion molecule LFA-1—so this is a form of inside-out signaling that increases B cell adhesion. Antigen binding also initiates the recruitment of other positive regulators such as CD19, which is critical for B cell activation in vivo. The microclusters thus form a platform for the assembly of all these molecules into what we’ve named “microsignalosomes”. Some molecules, such as CD19, are dynamically recruited to the BCR. Other bulkier molecules such as CD45 are excluded. This size-dependent exclusion fits the “kinetic-segregation” mechanism postulated by Anton van der Merwe and colleagues. Are the surface changes that occur after activation different between naive cells and memory cells? And
