A RAB35-p85/PI3K axis controls oscillatory apical protrusions required for efficient chemotactic migration

Abstract

How cells move chemotactically remains a major unmet challenge in cell biology. Emerging evidence indicates that for interpreting noisy, shallow gradients of soluble cues a system must behave as an excitable process. Here, through an RNAi-based, high-content screening approach, we identify RAB35 as necessary for the formation of growth factors (GFs)-induced waves of circular dorsal ruffles (CDRs), apically restricted actin-rich migratory protrusions. RAB35 is sufficient to induce recurrent and polarized CDRs that travel as propagating waves, thus behaving as an excitable system that can be biased to control cell steering. Consistently, RAB35 is essential for promoting directed chemotactic migration and chemoinvasion of various cells in response to gradients of motogenic GFs. Molecularly, RAB35 does so by directly regulating the activity of p85/PI3K polarity axis. We propose that RAB35 is a molecular determinant for the control of an excitable, oscillatory system that acts as a steering wheel for GF-mediated chemotaxis and chemoinvasion.

GAS6-AXL signaling triggers actin remodeling and macropinocytosis that drive cancer cell invasion

“…Two inhibitors specific for class I PI3Ks, GDC-0941 and ZSTK474, prevented the GAS6-AXL-dependent formation of CDRs in LN229 cells ( Fig 3F and G, Fig EV4C). These results are in agreement with a previous report that PDGF-induced CDRs were blocked by inhibition of PI3K but not AKT (Corallino et al, 2018).…”

“…We found two regulatory subunits of class IA PI3Ks, p85α and p85β, among AXL interactors only in GAS6-stimulated samples which indicated that they were specifically associated with activated AXL (Table EV1, Data EV1 and 2). Both subunits have been recently described as downstream effectors of RAB35, and their knockout prevented the formation of PDGF-induced CDRs (Corallino et al, 2018). Thus, to investigate their involvement in GAS6-AXL-driven CDR formation we depleted both p85 isoforms by siRNAmediated silencing in LN229 cells.…”

“…RAB35-dependent CDRs were proposed to act as a steering wheel for PDGF-and HGF-mediated chemotaxis and chemoinvasion (Corallino et al, 2018). To check whether GAS6 is a chemotactic factor, we tested migration of LN229 cells through a membrane towards GAS6 gradient in a Boyden chamber.…”

“…CDRs are enigmatic actinrich, ring-shaped structures formed transiently on the dorsal surface of cells, in response to certain growth factors. Up to date, it was demonstrated that CDRs are formed upon stimulation with platelet-derived growth factor (PDGF) in fibroblasts, hepatocyte growth factor (HGF) in HeLa and polarized epithelial MDCK cells, and epidermal growth factor (EGF) in fibroblasts and liver-derived epithelial cells (Abella et al, 2010;Azimifar et al, 2012;Chiasson-MacKenzie et al, 2018;Corallino et al, 2018;Mellstrom et al, 1988). The functions of these structures are still not fully explored, but they have been postulated to play a role in preparation of cells for motility, mesenchymal migration through ECM, and macropinocytosis (Chiasson-MacKenzie et al, 2018).…”

Endosomal spatio-temporal modulation of the cortical RhoA zone conditions epithelial cell organization

“…Whereas Rab35 functions during early step of endosomal recycling, EHD1 is required for late endosomal scission events (Kouranti et al, 2006; Klinkert and Echard, 2016; Cauvin et al, 2016). Even though Rab35 functions’ in cell migration and adhesion vary according to the cell types or migration assays, it emerges as a pivotal component during cancer progression for receptor presentation, actin dynamics and cell polarity (Shaughnessy and Echard, 2018; Corallino et al, 2018). A link between Rab35 and RhoA was mentioned previously although not clearly demonstrated nor with any apparent impact (Chevallier et al, 2009).…”