The Membrane Skeleton Controls Diffusion Dynamics and Signaling through the B Cell Receptor

Lymphocyte Interaction Laboratory, London Research Institute, Cancer Research UK, 44 Lincoln's Inn Fields, London WC2A 3PX, UK.
Immunity (Impact Factor: 19.75). 02/2010; 32(2):187-99. DOI: 10.1016/j.immuni.2009.12.005
Source: PubMed

ABSTRACT Early events of B cell activation after B cell receptor (BCR) triggering have been well characterized. However, little is known about the steady state of the BCR on the cell surface. Here, we simultaneously visualize single BCR particles and components of the membrane skeleton. We show that an ezrin- and actin-defined network influenced steady-state BCR diffusion by creating boundaries that restrict BCR diffusion. We identified the intracellular domain of Igbeta as important in mediating this restriction in diffusion. Importantly, alteration of this network was sufficient to induce robust intracellular signaling and concomitant increase in BCR mobility. Moreover, by using B cells deficient in key signaling molecules, we show that this signaling was most probably initiated by the BCR. Thus, our results suggest the membrane skeleton plays a crucial function in controlling BCR dynamics and thereby signaling, in a way that could be important for understanding tonic signaling necessary for B cell development and survival.

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Available from: Facundo Batista, Apr 12, 2014
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    • "The cytoskeleton was previously shown to restrict diffusion of membrane proteins, such as the BCR, Fcγ receptor, and CD36, thereby modulating their signaling. To our knowledge, this is the first demonstration that the actin cytoskeleton regulates physical contact between a membrane protease and its substrate (Treanor et al., 2010; Jaqaman et al., 2011; Jaumouille et al., 2014). Several factors could regulate such an exclusion mechanism. "
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    • "The quantification of the Fab-PLA analysis of B1-8 (Figure 4A, right panel) and TKO-MD (Figure 4B) B cells shows that in each case, the IgM:IgM and IgD:IgD Fab-PLA signal is lost upon exposure of B cells to antigen. The Fab-PLA signal is also lost when we stimulated B1-8 B cells apart from antigen with BCR-activating drugs such as pervanadate (Perv) and Lat-A (Figure 4C), which alter the phosphorylation/dephosphorylation equilibrium and inhibit actin polymerization, respectively (Secrist et al., 1993; Treanor et al., 2010). The same results were also obtained by an analysis of human peripheral blood B cells (Figure 4D). "
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    • "To further ensure that peptide internalization required the BCR and was not attributable to pinocytosis, we incubated FGD 17-mer with FluB1 MHC II GFP transnuclear stochastic optical reconstruction microscopy (STORM) allowed identification of IgM and IgD clusters on resting B cells (Mattila et al., 2013). Diffusion of the BCR and signaling depend on the actin cytoskeleton; the actin-depolymerizing agents latrunculin A and cytochalasin D promoted BCR activation and diffusion even in the absence of antigen (Treanor et al., 2010). Thus, at rest, BCR diffusion is restricted, whereas upon antigen binding the BCR diffuses more rapidly, likely disaggregates, and disperses to help capture more antigen (Fleire et al., 2006). "
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