Cytokine sensitivity and N-glycan processing mutations.

The EGF and TGF-beta families of cytokines are critical regulators of cell proliferation, morphogenesis, and tissue repair. The signaling pathways downstream of EGF and TGF-beta receptors also contribute to cancer growth and metastasis. Cytokine receptors are glycoproteins, and we have recently shown that GlcNAc-branching of N-glycans enhances their cell surface residency and contributes to the growth autonomy of cancer cells. Ligand-induced dimerization of EGF receptors leads to phosphorylation of Erk1/2, whereas TGF-beta binding to its receptors stimulates phosphorylation of Smad2/3. Activated Erk1/2 and Smad2/3 translocate independently into the nucleus and regulate gene expression. Here we describe a sensitive and robust method to quantify TGF-beta and EGF signaling in cancer cells and primary cells from mice by quantitative fluorescence imaging.