Brayford, S. | bioRxiv Science

bioRxiv2020

Nance-Horan Syndrome-like 1 protein negatively regulates Scar/WAVE-Arp2/3 activity and inhibits lamellipodia stability and cell migration.

Cell migration is important for development and its aberrant regulation contributes to many diseases. The Scar/WAVE complex is essential for Arp2/3 mediated lamellipodia formation during mesenchymal cell migration and several coinciding signals activate it. However, so far, no direct negative regulators are known. We have identified Nance-Horan Syndrome-like 1 protein (NHSL1) as a novel, direct binding partner of the Scar/WAVE complex, which co-localise at protruding lamellipodia. This interaction is mediated by the Abi SH3 domain and two binding sites in NHSL1. Furthermore, active Rac binds to NHSL1 at two regions that mediate leading edge targeting of NHSL1. Surprisingly, NHSL1 inhibits cell migration through its interaction with the Scar/WAVE complex. Mechanistically, NHSL1 may reduce cell migration efficiency by impeding Arp2/3 activity, as measured in cells using a novel Arp2/3 FRET-FLIM biosensor, resulting in reduced F-actin density of lamellipodia, and consequently impairing the stability of lamellipodia protrusions.

cell biology↗

bioRxiv2018

EphB2 and ERK signaling are required for heterotypic contact inhibition of locomotion to drive cell sorting

Interactions between different cell-types can induce distinct contact inhibition of locomotion (CIL) responses that are hypothesized to control population-wide behaviors during embryogenesis [1, 2]. However, our understanding of the signals that lead to cell-type specific repulsion, and the precise capacity of heterotypic CIL responses to drive emergent behaviors is lacking. Using a new in vitro model of heterotypic CIL between epithelial and mesenchymal cells, we show that fibrosarcoma cells (HT1080), but not fibroblasts (NIH3T3), are actively repelled by epithelial cells in culture. We show that knocking down EphB2 in fibrosarcoma cells specifically leads to disruption of the repulsion phase of CIL in response to interactions with epithelial cells. Furthermore, this heterotypic interaction requires ERK activation, downstream of EphB2 signaling. We also examine the population-wide effects when these various cell combinations, and their specific heterotypic CIL responses, are allowed to interact in culture. Mixtures of fibrosarcoma and epithelial cells - unlike fibroblasts and epithelial cells - lead to complete sorting and segregation of the two populations, and inhibiting their distinct CIL response by knocking down EphB2 or ERK in fibrosarcoma cells disrupts this emergent sorting behavior. Our understanding of the mechanisms underlying developmental behaviors such as cell sorting is lacking as predominant sorting hypotheses, such as differential adhesion, have recently been found inadequate in predicting the sorting of mesenchymal cells [3, 4]. These data suggest that heterotypic CIL responses, in conjunction with processes such as differential adhesion, may aid the sorting of cell populations during embryogenesis.

cell biology↗