INTEGRIN REGULATION · Functional analysis of the kinome and phosphatome as determinants of integrin phosphorylation in cancer

Integrins are key signalling molecules that mediate the complex relationship between cancer cells and their associated ECM; as such they have been implicated in every step of cancer progression. Their cytoplasmic domains are essential hubs for protein-protein interactions, where phosphorylation of key sites modulates integrin activity and oncogenic signalling. However, the regulators of integrin phosphorylation remain elusive. The proposed work will address the role of integrin beta1 in breast cancer epithelial and stromal cells, where increased expression and/or activity are correlated with poorer survival. To this end, the fellow has developed a Förster resonance energy transfer (FRET) biosensor for integrin beta1 phosphorylation, which will be applied in a kinome-/phosphatome-wide screen for regulatory kinases and/or phosphatases. This screening will be completmented with global mass spectrometry to identify phosphorylation-sensitive interactions with the integrin beta1 cytoplasmic domain. Out of these screens, the fellow will validate the identified kinases and/or phosphatases using three-dimensional functional assays, as well as standard biochemical approaches, in conjunction with live super-resolution imaging to pinpoint the subcellular localization of the interacting complex. The clinical relevance of the identified kinases and/or phosphatases will then be evaluated with immunohistochemistry staining of large breast cancer cohorts, along with functional validation using patient material from clinical collaborators. These aspects will provide an essential link from the mechanistic insights to improving patient outcomes from this work.