ABSTRACT
Disruption of the transcriptional activity of the Hippo pathway members YAP1 and TAZ has become a major target for cancer treatment. However, detailed analysis of the effectiveness and networks affected by YAP1/TAZ transcriptional targeting is limited. In this study, we utilize TEAD inhibitor, an inhibitor of the binding of YAP1 and TAZ with their main transcriptional target TEAD in a mouse model of basal cell carcinoma, to unveil the consequences of YAP1/TAZ transcriptional blockage in cancer cells. Both TEAD inhibitor and YAP1/TAZ knockdown lead to reduced proliferation and increased differentiation of mouse basal cell carcinoma driven by oncogenic hedgehog-smoothened (SmoM2) activity. Although TEAD-transcriptional networks were essential to inactivate differentiation, this inactivation was found to be indirect and potentially mediated through the repression of KLF4 by SNAI2. By comparing the transcriptional effects of TEAD inhibition with those caused by YAP1/TAZ depletion, we determined YAP1/TAZâTEADâindependent effects in cancer cells that impact STAT3 and NF-κB. Our results reveal the gene networks affected by targeting YAP1/TAZâTEAD in basal cell carcinoma tumors and expose the potential pitfalls for targeting TEAD transcription in cancer.
Subject(s)
Carcinoma, Basal Cell/metabolism , Hedgehogs/metabolism , TEA Domain Transcription Factors/metabolism , Transcriptional Coactivator with PDZ-Binding Motif Proteins/metabolism , YAP-Signaling Proteins/metabolism , Animals , Carcinogenesis , Carcinoma, Basal Cell/genetics , Cell Differentiation , Cell Line, Tumor , Disease Models, Animal , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , Hippo Signaling Pathway , Humans , Kruppel-Like Factor 4/metabolism , Mice , NF-kappa B/metabolism , STAT3 Transcription Factor/metabolism , Snail Family Transcription Factors/metabolism , Transcriptional Coactivator with PDZ-Binding Motif Proteins/genetics , YAP-Signaling Proteins/geneticsABSTRACT
The PKA-inhibitor (PKI) family members PKIα, PKIß, and PKIγ bind with high affinity to PKA and block its kinase activity, modulating the extent, and duration of PKA-mediated signaling events. While PKA is a well-known regulator of physiological and oncogenic events, the role of PKI proteins in these pathways has remained elusive. Here, by measuring activation of the MAPK pathway downstream of GPCR-Gαs-cAMP signaling, we show that the expression levels of PKI proteins can alter the balance of activation of two major cAMP targets: PKA and EPAC. Our results indicate that PKA maintains repressive control over MAPK signaling as well as a negative feedback on cAMP concentration. Overexpression of PKI and its subsequent repression of PKA dysregulates these signaling pathways, resulting in increased intracellular cAMP, and enhanced activation of EPAC and MAPK. We also find that amplifications of PKIA are common in prostate cancer and are associated with reduced progression free survival. Depletion of PKIA in prostate cancer cells leads to reduced migration, increased sensitivity to anoikis and reduced tumor growth. By altering PKA activity PKI can act as a molecular switch, driving GPCR-Gαs-cAMP signaling toward activation of EPAC-RAP1 and MAPK, ultimately modulating tumor growth.
Subject(s)
Acetylcysteine/analogs & derivatives , Erythromycin/analogs & derivatives , Intracellular Signaling Peptides and Proteins/metabolism , MAP Kinase Signaling System , Prostatic Neoplasms/metabolism , Acetylcysteine/metabolism , Animals , Cell Line, Tumor , Cyclic AMP/metabolism , Cyclic AMP-Dependent Protein Kinases/metabolism , Erythromycin/metabolism , Extracellular Signal-Regulated MAP Kinases/metabolism , Feedback, Physiological , Female , GTP-Binding Protein alpha Subunits/metabolism , HEK293 Cells , Humans , Intracellular Signaling Peptides and Proteins/genetics , Male , Mice , Mice, Nude , Prostatic Neoplasms/genetics , Prostatic Neoplasms/pathologyABSTRACT
G-protein coupled receptors (GPCRs) and their associated heterotrimeric G proteins impinge on pathways that control epithelial cell self-renewal and differentiation. Although it is known that Gαs protein signaling regulates skin homeostasis in vivo, the role of GPCR-coupled Gαi proteins in the skin is unclear. Here, by using a chemogenetic approach, we demonstrate that GPCR-Gαi activation can regulate keratinocyte proliferation and differentiation and that overactivation of Gαi-signaling in the basal compartment of the mouse skin can lead to epidermal hyperplasia. Our results expand our understanding of the role of GPCR-cAMP signaling in skin homeostasis and reveal overlapping and divergent roles of the cAMP-regulating heterotrimeric Gαs and Gαi proteins in keratinocytes.
