CDK5 interacts with STK3

Passi, Mehak (2023): CDK5 interacts with STK3: a consequence to the Hippo signaling. Dissertation, LMU München: Fakultät für Chemie und Pharmazie

Abstract

The Hippo-YAP/TAZ pathway is the most prevalent evolutionary conserved pathway from Drosophila to mammals and plays a key role in controlling organ size, cell growth, self-renewal, and tissue homeostasis. Hippo pathway consists of MST/LATS kinase module and YAP/TAZ-TEAD transcription module and is generally regulated by transcriptional activity of YAP and TAZ. YAP and TAZ are mechanosensory proteins that read a broad range of mechanical clues from shear stress of cell shape, contact, extracellular matrix rigidity and stiffness. In general, the Hippo pathway kinases are generally considered tumour suppressors while YAP/TAZ are considered Oncoproteins. Activation of transcription co-activators YAP/TAZ is inhibited by phosphorylation caused by LATS1/2 and MST1/2 kinases which results in cytoplasmic sequestration and degradation of YAP/TAZ. While unphosphorylated, YAP/TAZ translocate to the nucleus and bind to TEAD family transcription factors to induce gene expression. Hippo pathway is widely dysregulated in cancer and mechano-transduction of YAP and TAZ is critical for driving expression of genes involved in cancer progression and growth. Cyclin-dependent kinase 5 is an unusual member of the family of cyclin-dependent kinases, which is activated upon binding to non-cyclin p35 and p39 proteins. It is known to be widely involved in tumorigenic processes. Through yeast two hybrid system we found a novel interaction between MST2 (STK3) and CDK5 which was further confirmed by co-immunoprecipitation experiments. In the current study, we aim to shed a light on the involvement of CDK5 in the Hippo pathway via interaction with MST2. We try to understand the relationship between CDK5 and Hippo kinases and how CDK5 influences the Hippo pathway cascade without being directly involved in it. We show how active YAP activity changes with CDK5 knockdown and overexpression. CDK5 also influences the expression of phosphorylated levels of upstream kinases of Hippo Pathway especially pLATS1 (thr1079). Expression of YAP target genes also get influenced where cells find a way to compensate for the reduced YAP activity by upregulating other mechanosensory pathways such as MRTF/.SRF. Our findings illustrate that it is not the kinase activity of CDK5 that is involved in the process. However, it does act like a scaffold bringing the other proteins together and providing a platform for Hippo pathway cascade. Phosphoproteomics analysis brings the same picture out and shed light to the overall phospho changes with CDK5 knockdown and overexpression. Further phosphoproteomics results also reveal that CDK5 interact with DLG5 another upstream kinase and regulates the Hippo pathway via cross talk with several other signalling pathways especially MAPK signalling. Finally, CDK5 not only acts as a scaffold protein but also is involved assisting cross talk of Hippo pathway with other signalling cascades. Our findings might be useful for developing novel drugs which can target CDK5 and regulate Hippo signalling.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: CDK5, Hippo pathway, YAP/TAZ, MST1/2, LATS1/2, kinases, overexpression, knockdown, MAPK
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 540 Chemie
• Fakultäten: Fakultät für Chemie und Pharmazie
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 15. März 2023
• 1. Bericht­erstatter:in: Zahler, Stefan