Actin Filaments Couple the Protrusive Tips to the Nucleus through the I-BAR Domain Protein IRSp53 during the Migration of Cells on 1D Fibers.

The cell migration cycle, well-established in 2D, proceeds with forming new protrusive structures at the cell membrane and subsequent redistribution of contractile machinery. Three-dimensional (3D) environments are complex and composed of 1D fibers, and 1D fibers are shown to recapitulate essential features of 3D migration. However, the establishment of protrusive activity at the cell membrane and contractility in 1D fibrous environments remains partially understood. Here the role of membrane curvature regulator IRSp53 is examined as a coupler between actin filaments and plasma membrane during cell migration on single, suspended 1D fibers. IRSp53 depletion reduced cell-length spanning actin stress fibers that originate from the cell periphery, protrusive activity, and contractility, leading to uncoupling of the nucleus from cellular movements. A theoretical model capable of predicting the observed transition of IRSp53-depleted cells from rapid stick-slip migration to smooth and slower migration due to reduced actin polymerization at the cell edges is developed, which is verified by direct measurements of retrograde actin flow using speckle microscopy. Overall, it is found that IRSp53 mediates actin recruitment at the cellular tips leading to the establishment of cell-length spanning fibers, thus demonstrating a unique role of IRSp53 in controlling cell migration in 3D.

The mechanistic influence of aligned nanofibers on cell shape, migration and blebbing dynamics of glioma cells.

Investigating the mechanistic influence of the tumor microenvironment on cancer cell migration and membrane blebbing is crucial in the understanding and eventual arrest of cancer metastasis. In this study, we investigate the effect of suspended and aligned nanofibers on the glioma cytoskeleton, cell shape, migration and plasma membrane blebbing dynamics using a non-electrospinning fiber-manufacturing platform. Cells attached in repeatable shapes of spindle on single fibers, rectangular on two parallel fibers and polygonal on intersecting fibers. Structural stiffness (N m(-1)) of aligned and suspended nanofibers (average diameter: 400 nm, length: 4, 6, and 10 mm) was found to significantly alter the migration speed with higher migration on lower stiffness fibers. For cells attached to fibers and exhibiting blebbing, an increase in cellular spread area resulted in both reduced bleb count and bleb size with an overall increase in cell migration speed. Blebs no longer appeared past a critical cellular spread area of approximately 1400 µm(2). Our results highlighting the influence of the mechanistic environment on the invasion dynamics of glioma cells add to the understanding of how biophysical components influence glioma cell migration and blebbing dynamics.