cAMP-mediated regulation of proliferative kinase circuits

The diffusible second messenger cAMP either boosts or reduces cell proliferation in a cell-type specific manner. This involves the cAMP-dependent kinase PKA and their scaffolding proteins for coordinating the interplay of participating kinases. One example is the impact of cAMP on RAF kinase functions which actually is the center stage of mitogen-activated protein kinase signaling. A collection of BRAF cancer mutations decouples the kinase from the upstream regulator RAS. Clinically approved BRAF inhibitors yielded dramatic responses in malignant melanomas. However, their therapeutic benefit in melanoma patients is temporary. We assume that kinase scaffolds coordinate the interplay of RAF and PKA activities. Activation of cAMP-nanodomains in RAF vicinity may have the potential to antagonize deregulated RAF activities. First, we plan to determine and perturb macromolecular RAF:PKA complexes. Second, we aim to determine the impact of reciprocal kinase activation/inactivation on metabolic and pathological downstream signaling. Third, we plan to assign and pharmacologically modulate cAMP-linked signaling pathways for conquering aberrant BRAF signaling in melanoma cell lines.

Our research focused on two central signaling molecules, PKA and RAF, which play crucial roles in both physiological and pathological signal transduction. We identified new physiological and functional interactions of these kinases and elucidated kinase crosstalk, enhancing our understanding of cellular regulation of these central signaling hubs. Additionally, we studied the molecular mechanisms of RAF target engagement in cancer cell models, demonstrating mutations-specific effects, particularly with BRAF. These findings are significant for developing targeted therapies and provide insights into the molecular foundations of cancer. We have published several key findings. We identified novel PKA interactions, particularly with GPR161 and TAF15, expanding our knowledge of compartmentalized PKA complexes (PNAS 2016, Nat Struct Mol Biol 2024). We explored the role of PKA in regulating ciliary signaling pathways and the feedback control of the Gpr161-Gs-PKA axis in Hedgehog signaling repression (Development 2021, Cells 2020). We unveiled that TAF15 is a nuclear PKA substrate and its impact on RNA-binding dynamics (CMLS 2024). Inm the context of BRAF signaling we investigated novel mechanisms of RAF activation and regulation in cancer (Sci Adv 2019, PNAS 2020, eLife 2024). Our research explored the impact of RAF mutations on MAPK signaling dynamics, providing insights into cancer development and potential therapeutic targets (Biomolecules 2021, Cell Cyst 2022, PNAS Nexus 2023). In addition, we were able to investigate the effects of kinase functions on mitochondrial activities, among others (Cancers 2022, Bionerg. comm. 2022).These findings have enhanced our understanding of kinase regulation in both normal and pathological contexts, opening new avenues for targeted therapies in diseases such as cancer and neurodegenerative disorders.