LINKIN-associated proteins necessary for tissue integrity during collective cell migration.

Cell adhesion plays essential roles in almost every aspect of metazoan biology. Previously, using the developmental migration of the nematode male gonad as a platform, LINKIN (Human: ITFG1, C. elegans: lnkn-1 ), a relatively understudied transmembrane protein conserved across the metazoa, was found to be necessary for tissue integrity during migration. In C. elegans , loss of lnkn-1 results in the detachment of the lead migratory cell from the rest of the developing male gonad. Three interactors of ITFG1/ lnkn-1 -RUVBL1/ ruvb-1 , RUVBL2/ ruvb-2 , and alpha-tubulin were identified by proteomic analysis using the human HEK293T cells and validated in the nematode male gonad. The ITFG1-RUVBL1 interaction has since been independently validated in a breast cancer cell line model that also implicates the involvement of the pair in metastasis. In this study, we showed that epitope-tagged ITFG1 localized to the cell surface of MDA-MB-231 breast cancer cells. Using unbiased mass spectrometry-based proteomics, we identified a new list of potential interactors of ITFG1. Loss-of-function analysis of their C. elegans orthologs found that three of the interactors-ATP9A/ tat-5 , NME1/ ndk-1 , and ANAPC2/apc-2 displayed migratory detachment phenotypes similar to that of lnkn-1 . Taken together with the other genes whose reduction of function phenotype is the same as LINKIN (notably cohesion and condensin) suggests the involvement of membrane remodeling and chromosome biology in the tight adhesion dependent on LINKIN, and support the hypothesis for a structure role of chromosomes in post-mitotic cells.