Localized translation regulates cell adhesion and transendothelial migration

Abstract

Epithelial-to-mesenchymal transition (EMT) is a process by which cancer cells gain the ability to leave the primary tumor site and invade surrounding tissues. These metastatic cancer cells can further increase their plasticity by adopting an amoeboid-like morphology, by undergoing mesenchymal-to-amoeboid transition (MAT). We found that adhering cells produce spreading initiation centers (SICs), transient structures that are localized above nascent adhesion complexes, and share common biological and morphological characteristics associated with amoeboid cells. Meanwhile, spreading cells seem to return to a mesenchymal-like morphology. Thus, our results indicate that SIC-induced adhesion recapitulates events that are associated with amoeboid-to-mesenchymal transition (AMT). We found that polyadenylated RNAs are enriched within SICs, blocking their translation decreased adhesion potential of metastatic cells that progressed through EMT. These results point to a so-farunknown checkpoint that regulates cell adhesion and allows metastatic cells to alter adhesion strength to modulate their dissemination.

Morphoregulatory functions of the RNA-binding motif protein 3 in cell spreading, polarity and migration

“…We confirmed that RBM3 co-localized with the cytoskeletal protein vinculin (Fig. 1g ), a known component of SICs 31 , 32 , and that SICs contained the RNA-BP FUS as previously reported 31 , 32 (Fig. 1h ).…”

“…SICs are spherical outpouchings of the plasma membrane in which a ring of F-actin circumscribes a cytoplasmic interior containing some focal adhesion proteins, translation machinery, ribosomal and poly A RNA, and RNA-BPs 31 – 33 . They are “hot spots” of mRNA translation 32 , which is thought to promote the formation of mature focal adhesions 31 , 32 . Insofar as our prior work showed that RBM3 stimulates translation 5 , the detection of RBM3 in SICs raised the possibility that it is a regulator of cell spreading.…”

“…Several observations suggest that RBM3 has morphoregulatory functions relevant to its role in cell protection and putative involvement in development and oncogenesis. RBM3 (P98179, RNPL) was among sets of RNA-binding proteins (RNA-BPs) detected in invasive pseudopodia of mesenchymal breast cancer cells 30 , and in subcellular specializations termed spreading initiation centers (SICs) 31 that form during the initial stage of cell spreading in fibroblasts and many mesenchymal cell lines 32 . In general, several classes of RNA-BPs have been identified in SICs 31 – 33 and other cell protrusions, such as podosomes 34 , pseudopodia 30 , 35 , 36 , filopodia 37 , growth cones and dendritic spines 38 – 40 .…”

Adenoviral protein E4orf4 interacts with the polarity protein Par3 to induce nuclear rupture and tumor cell death

“…HaCaT cells are spontaneously immortalized from adult skin keratinocytes and retain full differentiation capacity, while RPE-1 cells are near-diploid human retinal pigment epithelial cells immortalized with human telomerase reverse transcriptase (hTERT; Bodnar et al, 1998;Boukamp et al, 1988). In marked contrast, E4orf4 reduced cell proliferation in several types of cancer cell lines, including triple-negative breast cancer cells with epithelial or mesenchymal properties (MDA-MB-468 and MDA-MB-231, respectively; Bergeman et al, 2016), human bone osteosarcoma epithelial cells (U2OS), prostate carcinoma epithelial cells (22Rv1), and cervix carcinoma epithelial cells (HeLa; Fig. 1 B, Proliferation).…”

“…After digestion by EcoRI, this sequence was ligated into EcoRI restriction sites of pLKO.1 vector containing shSUN1 to generate shSUN1-1/2-2 and shSUN1-2/ 2-1. Lentiviral particles were generated by transfecting 293T cells with 12 µg pLKO.1 vector, 6 µg psPAX2 packaging plasmid (Addgene; plasmid #12260), and 2 µg pMD2.G envelope plasmid (Addgene; plasmid #12259), as described previously (Bergeman et al, 2016).…”