Force in Migration: The mechanism of Nuclear Force Coupling driven invasive cell migration

Cell migration is fundamental for many processes in the human body and its deregulation can lead to a vast variety of pathologies including cancer cell invasion and impaired cell locomotion in prematurely ageing cells. Cells in tissues need to sense the physical qualities -for example the stiffness or flexibility- of their environment and they can adapt their behaviour and shape accordingly. This proposal aims to investigate just how cells effectively transmit signals caused by physical cues on their outside directly to their nucleus to enable cell migration and changes in gene transcription. This will help to understand how forces applied to the nucleus can drive cancer cell invasion into surrounding tissues.

Cells migrating through 3D matrices form hybrid adhesion structures, which display hallmarks of both focal adhesions and invadopodia. We have identified an interaction between beta-PIX (ARHGEF7; COOL-1) and Myosin18A (M18A) in 3D matrix adhesion sites. Loss of beta-PIX /M18A abolished cancer cell invasion, but increased matrix degradation and pseudopod extension in collagen matrices. These seemingly contradictory results can be explained by our finding that beta-PIX is part of a betaPIX -M18A-nonmuscle myosin 2A (NM2A) recruitment cascade that is required for adhesion site turnover and nuclear-force coupling (NFC). The nucleus can act as limiting factor in 3D cell migration. Migrating cells need to actively squeeze the nucleus through matrix pores. Knockdown of nuclear envelope actin binding proteins called Nesprin-1 and -2 severely affect 3D cell migration. We have found a reciprocal regulation of Nesprin-2 and beta-PIX /M18A function. We can show using a novel nuclear membrane FRET/FLIM force biosensor, that direct force coupling from 3D adhesion sites to the nuclear membrane through beta-PIX/M18A is required for 3D cell migration. We propose that this mechanism establishes front-rear cell polarity during 3D cell migration through NM2 isoform polarisation. In addition, disruption of nuclear-force coupling inhibited the tension dependant translocation of the pro-invasive transcription factors YAP/TAZ to the nucleus. This proposal will explain how nuclear-force coupling facilitates cell invasion into extracellular matrices in three connected work packages (WP): WP1: Elucidate mechanism and function of M18A mediated NFC and NM2 isoform polarisation in 3D invasive migration. WP2: Identification of molecular signalling pathways required for and affected by mechano-transmission from adhesions to the nucleus in cancer cells. WP3: Effect of nuclear force transduction on cancer cell invasion

This project investigates the basis of a molecular mechanism that is essential for cancer cell invasion and frequently altered in genetic diseases of the nuclear lamina. The primary beneficiaries of this work will be academic and commercial scientists, that will benefit from the data and novel tools that will be made freely available after publication of the manuscripts arising from this project (for details of dissemination see pathways to impact). The network of researchers involved in this work will establish tighter links that will enable the formation of a potentially long term research collaboration on the mechanisms and function of nuclear force transduction in multiple tissues and diseases.