Subcellular topography modulates actin dynamics and signaling in B-cells

Abstract

B-cell signaling activation is most effectively triggered by the binding of B-cell receptors (BCRs) to membrane-bound antigens. In vivo, B-cells encounter antigen on antigen-presenting cells (APC), which possess complex surfaces with convoluted topographies, a fluid membrane and deformable cell bodies. However, whether and how the physical properties of antigen presentation affect B-cell activation is not well understood. Here we use nanotopographic surfaces that allow systematic variation of geometric parameters to show that surface features on a subcellular scale influence B-cell signaling and actin dynamics. Parallel nanoridges with spacings of 3 microns or greater induce actin intensity oscillations on the ventral cell surface. Nanotopography-induced actin dynamics requires BCR signaling, actin polymerization, and myosin contractility. The topography of the stimulatory surface also modulates the distribution of BCR clusters in activated B-cells. Finally, B-cells stimulated on nanopatterned surfaces exhibit intracellular calcium oscillations with frequencies that depend on topography. Our results point to the importance of physical aspects of ligand presentation, in particular, nanotopography for B-cell activation and antigen gathering.

Quantifying topography-guided actin dynamics across scales using optical flow

“…when cells encounter obstacles 10 . It has also been established that ridges of width comparable to fibers in the extracellular matrix (ECM) can alter actin dynamics significantly 9,11,12 and bias the localization of focal adhesions 13,14 . Thus, in vivo, the topography of the ECM, such as collagen networks 15,16 , is likely to modulate actin dynamics.…”

“…In prior work we have shown that actin waves can be nucleated near, and guided along, periodic nanotopography, in a phenomenon termed esotaxis. Actin-wave guidance has been observed in cell types that exhibit distinct physiological functions and migration phenotypes, including Dictyostelium discoideum 11,12 , neutrophil-like HL60 cells 12 , B cells 9 , and breastcancer cell lines 17 . However, there are clear differences in the responses of each of these cell types to nanotopography.…”

Driving Cells with Light‐Controlled Topographies

“…[52] Large and slow scales can also be explored thanks to the possibility of obtaining stable (in our experiments, months) topography modifications over large areas, by means of irradiation with low-magnification lenses. Such features allow to employ our setup to study biological phenomena that occur on the scale of a few tens of seconds and on the spatial scale of a cell, such as calcium signaling, e.g., which has been shown to be influenced by topographies.…”

“…Small and fast scales can be reached thanks to the fast responsivity of the azopolymer and is greatly improved by two technical advantages of our approach: i) deformations occur at once and do not require laser scanning and ii) substrate stimulation and biological observation can be performed simultaneously. Such features allow to employ our setup to study biological phenomena that occur on the scale of a few tens of seconds and on the spatial scale of a cell, such as calcium signaling, e.g., which has been shown to be influenced by topographies …”

Quantifying topography-guided actin dynamics across scales using optical flow

“…Physical and chemical characteristics of the extracellular environment, such as rigidity, biochemical composition, and topography, have been shown to influence actin dynamics and associated cell behavior ( Discher et al , 2005 ; Doyle et al , 2009 ; Lu et al , 2012 ; Petrie and Yamada, 2015 ). One mechanism for this modulation is mechanosensing via focal adhesions ( Ketchum et al , 2018 ). In addition, actin waves respond when cells encounter obstacles ( Weiner et al , 2007 ).…”