Decoding Signal Transmission through Receptor Tyrosine Kinases

Abstract

The development and homeostasis of multicellular organisms requires that their comprising cells appropriately process multitudes of information within the cellular microenvironment. Receptor tyrosine kinases (RTKs) are one major class of cell-surface receptors by which cells engage with extracellular cues, thereby modulating the activity of multiple downstream signaling pathways to control cellular processes. Signaling throughout the RTK signaling network is spatiotemporally dynamic, and these dynamics play a vital role in controlling cellular processes. Yet we lack a comprehensive understanding of how RTK-dependent signaling dynamics are encoded by extracellular cues. In this work, we investigate how mammalian cells integrate multiple environmental cues to modulate signaling downstream of RTKs and present a strategy to monitor the activity of any RTK of interest in living cells. First, we systematically interrogated how the mechanical properties of mammary epithelial tissues affect RTK-dependent signaling through the Erk pathway, revealing soft microenvironments attenuate Erk signaling dynamics by disrupting interactions between RTKs and their cognate ligands. Second, we engineered a biosensing strategy to monitor the activity of RTKs in living cells, termed pYtags. Using pYtags to make unprecedented measurements of RTK signaling, we revealed modes of receptor-level signal modulation dependent on tissue morphology, ligand identity, and the composition of RTKs displayed at the cell surface. This work highlights the multiple factors that influence signaling through RTKs and paves the way to understanding how RTK signaling dynamics are encoded spatiotemporally.