Rab5-regulated endocytosis plays a crucial role in apical extrusion of transformed cells

Abstract

Newly emerging transformed cells are often eliminated from epithelial tissues. Recent studies have revealed that this cancer-preventive process involves the interaction with the surrounding normal epithelial cells; however, the molecular mechanisms underlying this phenomenon remain largely unknown. In this study, using mammalian cell culture and zebrafish embryo systems, we have elucidated the functional involvement of endocytosis in the elimination of RasV12-transformed cells. First, we show that Rab5, a crucial regulator of endocytosis, is accumulated in RasV12-transformed cells that are surrounded by normal epithelial cells, which is accompanied by upregulation of clathrin-dependent endocytosis. Addition of chlorpromazine or coexpression of a dominant-negative mutant of Rab5 suppresses apical extrusion of RasV12 cells from the epithelium. We also show in zebrafish embryos that Rab5 plays an important role in the elimination of transformed cells from the enveloping layer epithelium. In addition, Rab5-mediated endocytosis of E-cadherin is enhanced at the boundary between normal and RasV12 cells. Rab5 functions upstream of epithelial protein lost in neoplasm (EPLIN), which plays a positive role in apical extrusion of RasV12 cells by regulating protein kinase A. Furthermore, we have revealed that epithelial defense against cancer (EDAC) from normal epithelial cells substantially impacts on Rab5 accumulation in the neighboring transformed cells. This report demonstrates that Rab5-mediated endocytosis is a crucial regulator for the competitive interaction between normal and transformed epithelial cells in mammals.cell competition | endocytosis | apical extrusion | Rab5 | RasV12

Prostaglandin E2 and its receptor EP2 trigger signaling that contributes to YAP‐mediated cell competition

“…We previously showed that Ras (G12V)‐expressing MDCK cells undergoing apical extrusion exhibit E‐cadherin internalization (Saitoh et al, ). To investigate whether E‐cadherin internalization was also observed during the apical extrusion of YAP (5SA) cells, we carried out E‐cadherin immunostaining and detected E‐cadherin internalization in YAP (5SA) cells surrounded by normal MDCK cells, but not in YAP (5SA) cells surrounded by YAP (5SA) cells (Figure ).…”

“…When MDCK cells expressing either of the oncogenic proteins Ras (G12V) or v‐Src are surrounded by nontransformed cells, the transformed MDCK cells are removed by apical extrusion (Hogan et al, ; Kajita et al, ; Maruyama & Fujita, ). Filamin and vimentin accumulate in the surrounding normal cells, whereas E‐cadherin is internalized in the apically extruded cells (Kajita et al, ; Saitoh et al, ). Thus, at least some mechanisms of cell competition induction are conserved from Drosophila to mammals.…”

Evolutionary rate covariation analysis of E-cadherin identifies Raskol as regulator of cell adhesion and actin dynamics inDrosophila

“…Since α- Cat has an ERC value of 0.47 relative to shg (Fig 1A), placing their ERC value in the top 0.6 % of all gene pairs, we reasoned that genes with similar or higher ERC values would represent genes with similar evolutionary histories to shg. Accordingly, the thresholded shg ERC list contains genes with described roles in AJ regulation such as Hrb98DE [32, 33], PDZ-GEF [34, 35], babo [36, 37], CG16952 [ 38, 39] and Rab5 [40–42] (Table 1). Excitingly, the majority of identified genes have not been associated with the AJ and include transcription factors, kinases, GTPase regulatory proteins and calcium channel regulators (Table 1).…”

“…Hrb98DE is an RNA-binding protein that regulates DE-Cad mRNA processing [32, 33]. Mammalian orthologs of the small GTPase Rab5 regulate E-Cad trafficking [40, 42]. The mammalian homolog of transcription factor CG16952, Btbd7, regulates E-Cad expression [38, 39].…”

Endocytosis, cadherins and tissue dynamics

“…In this review, we will therefore consider broadly how endocytosis contributes to tissue dynamics. We should say from the outset that it is not our intention to be comprehensive; in particular, while we focus on tissue‐scale events, endocytosis has also been implicated in more local morphogenetic events such as cell extrusion . We apologize in advance to our colleagues whose contributions to this area we have neglected to discuss.…”