Negative feedback couples Hippo pathway activation with Kibra degradation independent of Yorkie-mediated transcription

The Hippo (Hpo) pathway regulates tissue growth in many animals. Multiple upstream components promote Hpo pathway activity, but the organization of these different inputs, the degree of crosstalk between them, and whether they are regulated in a distinct manner is not well understood. Kibra (Kib) activates the Hpo pathway by recruiting the core Hpo kinase cassette to the apical cortex. Here, we show that the Hpo pathway downregulates Drosophila Kib levels independently of Yorkie-mediated transcription. We find that Hpo signaling complex formation promotes Kib degradation via SCFSlimb-mediated ubiquitination, that this effect requires Merlin, Salvador, Hpo, and Warts, and that this mechanism functions independently of other upstream Hpo pathway activators. Moreover, Kib degradation appears patterned by differences in mechanical tension across the wing. We propose that Kib degradation mediated by Hpo pathway components and regulated by cytoskeletal tension serves to control Kib-driven Hpo pathway activation and ensure optimally scaled and patterned tissue growth.

Download Full-text

Yorkie-independent negative feedback couples Hippo pathway activation with Kibra degradation

10.1101/2020.07.08.192765 ◽

2020 ◽

Author(s):

Sherzod A. Tokamov ◽

Ting Su ◽

Anne Ullyot ◽

Richard G. Fehon

Keyword(s):

Negative Feedback ◽

Feedback Loop ◽

Hippo Pathway ◽

Tissue Growth ◽

Hippo Signaling ◽

Hippo Signaling Pathway ◽

The Core ◽

Pathway Activation ◽

The Hippo Pathway ◽

Transcriptional Output

AbstractThe Hippo signaling pathway regulates tissue growth in many animals. Multiple upstream components are known to promote Hippo pathway activity, but the organization of these different inputs, the degree of crosstalk between them, and whether they are regulated in a distinct manner is not well understood. Kibra activates the Hippo pathway by recruiting the core Hippo kinase cassette to the apical cortex. Here we show that the Hippo pathway downregulates Kibra levels independently of Yorkie-mediated transcriptional output. We find that the Hippo pathway promotes Kibra degradation via SCFSlimb-mediated ubiquitination, that this effect requires the core kinases Hippo and Warts, and that this mechanism functions independently of other upstream Hippo pathway activators including Crumbs and Expanded. Moreover, Kibra degradation appears patterned across tissue. We propose that Kibra degradation by the Hippo pathway serves as a negative feedback loop to tightly control Kibra-mediated Hippo pathway activation and ensure optimally scaled and patterned tissue growth.

Download Full-text

The palmitoyltransferase Approximated promotes growth via the Hippo pathway by palmitoylation of Fat

The Journal of Cell Biology ◽

10.1083/jcb.201609094 ◽

2016 ◽

Vol 216 (1) ◽

pp. 265-277 ◽

Cited By ~ 14

Author(s):

Hitoshi Matakatsu ◽

Seth S. Blair ◽

Richard G. Fehon

Keyword(s):

Posttranslational Modification ◽

Hippo Pathway ◽

Growth Control ◽

Tissue Growth ◽

Negative Regulator ◽

Pathway Activity ◽

Protein Association ◽

Junctional Region ◽

Growth Loss ◽

The Hippo Pathway

The large protocadherin Fat functions to promote Hippo pathway activity in restricting tissue growth. Loss of Fat leads to accumulation of the atypical myosin Dachs at the apical junctional region, which in turn promotes growth by inhibiting Warts. We previously identified Approximated (App), a DHHC domain palmitoyltransferase, as a negative regulator of Fat signaling in growth control. We show here that App promotes growth by palmitoylating the intracellular domain of Fat, and that palmitoylation negatively regulates Fat function. Independently, App also recruits Dachs to the apical junctional region through protein–protein association, thereby stimulating Dachs’s activity in promoting growth. Further, we show that palmitoylation by App functions antagonistically to phosphorylation by Discs-overgrown, which activates Fat. Together, these findings suggest a model in which App promotes Dachs activity by simultaneously repressing Fat via posttranslational modification and recruiting Dachs to the apical junctional region, thereby promoting tissue growth.

Download Full-text

Activation mechanisms of the Hippo kinase signaling cascade

Bioscience Reports ◽

10.1042/bsr20171469 ◽

2018 ◽

Vol 38 (4) ◽

Cited By ~ 20

Author(s):

Sung Jun Bae ◽

Xuelian Luo

Keyword(s):

Hippo Pathway ◽

Adaptor Proteins ◽

Tissue Growth ◽

Fine Tuning ◽

Hippo Signaling ◽

Kinase Activation ◽

The Core ◽

Activation Mechanisms ◽

Kinase Cascade ◽

The Hippo Pathway

First discovered two decades ago through genetic screens in Drosophila, the Hippo pathway has been shown to be conserved in metazoans and controls organ size and tissue homeostasis through regulating the balance between cell proliferation and apoptosis. Dysregulation of the Hippo pathway leads to aberrant tissue growth and tumorigenesis. Extensive studies in Drosophila and mammals have identified the core components of Hippo signaling, which form a central kinase cascade to ultimately control gene expression. Here, we review recent structural, biochemical, and cellular studies that have revealed intricate phosphorylation-dependent mechanisms in regulating the formation and activation of the core kinase complex in the Hippo pathway. These studies have established the dimerization-mediated activation of the Hippo kinase (mammalian Ste20-like 1 and 2 (MST1/2) in mammals), the dynamic scaffolding and allosteric roles of adaptor proteins in downstream kinase activation, and the importance of multisite linker autophosphorylation by Hippo and MST1/2 in fine-tuning the signaling strength and robustness of the Hippo pathway. We highlight the gaps in our knowledge in this field that will require further mechanistic studies.

Download Full-text

Spectrin regulates Hippo signaling by modulating cortical actomyosin activity

eLife ◽

10.7554/elife.06567 ◽

2015 ◽

Vol 4 ◽

Cited By ~ 58

Author(s):

Hua Deng ◽

Wei Wang ◽

Jianzhong Yu ◽

Yonggang Zheng ◽

Yun Qing ◽

...

Keyword(s):

Hippo Pathway ◽

Myosin Ii ◽

Tissue Growth ◽

Hippo Signaling ◽

Upstream Regulator ◽

Kinase Cascade ◽

Cytoskeletal Tension ◽

Living Tissues ◽

The Hippo Pathway ◽

Upstream Regulators

The Hippo pathway controls tissue growth through a core kinase cascade that impinges on the transcription of growth-regulatory genes. Understanding how this pathway is regulated in development remains a major challenge. Recent studies suggested that Hippo signaling can be modulated by cytoskeletal tension through a Rok-myosin II pathway. How cytoskeletal tension is regulated or its relationship to the other known upstream regulators of the Hippo pathway remains poorly defined. In this study, we identify spectrin, a contractile protein at the cytoskeleton-membrane interface, as an upstream regulator of the Hippo signaling pathway. We show that, in contrast to canonical upstream regulators such as Crumbs, Kibra, Expanded, and Merlin, spectrin regulates Hippo signaling in a distinct way by modulating cortical actomyosin activity through non-muscle myosin II. These results uncover an essential mediator of Hippo signaling by cytoskeleton tension, providing a new entry point to dissecting how mechanical signals regulate Hippo signaling in living tissues.

Download Full-text

Biophysical characterization of SARAH domain–mediated multimerization of Hippo pathway complexes in Drosophila

Journal of Biological Chemistry ◽

10.1074/jbc.ra120.012679 ◽

2020 ◽

Vol 295 (18) ◽

pp. 6202-6213 ◽

Cited By ~ 1

Author(s):

Leah Cairns ◽

Angela Patterson ◽

Kyler A. Weingartner ◽

T. J. Koehler ◽

Daniel R. DeAngelis ◽

...

Keyword(s):

Complex Formation ◽

Hippo Pathway ◽

Coiled Coil ◽

Biophysical Characterization ◽

Pathway Activity ◽

Pulldown Assay ◽

Cell Niche ◽

The Stability ◽

Cell Growth And Proliferation ◽

Structural Levels

Hippo pathway signaling limits cell growth and proliferation and maintains the stem-cell niche. These cellular events result from the coordinated activity of a core kinase cassette that is regulated, in part, by interactions involving Hippo, Salvador, and dRassF. These interactions are mediated by a conserved coiled-coil domain, termed SARAH, in each of these proteins. SARAH domain–mediated homodimerization of Hippo kinase leads to autophosphorylation and activation. Paradoxically, SARAH domain–mediated heterodimerization between Hippo and Salvador enhances Hippo kinase activity in cells, whereas complex formation with dRassF inhibits it. To better understand the mechanism by which each complex distinctly modulates Hippo kinase and pathway activity, here we biophysically characterized the entire suite of SARAH domain–mediated complexes. We purified the three SARAH domains from Drosophila melanogaster and performed an unbiased pulldown assay to identify all possible interactions, revealing that isolated SARAH domains are sufficient to recapitulate the cellular assemblies and that Hippo is a universal binding partner. Additionally, we found that the Salvador SARAH domain homodimerizes and demonstrate that this interaction is conserved in Salvador's mammalian homolog. Using native MS, we show that each of these complexes is dimeric in solution. We also measured the stability of each SARAH domain complex, finding that despite similarities at both the sequence and structural levels, SARAH domain complexes differ in stability. The identity, stoichiometry, and stability of these interactions characterized here comprehensively reveal the nature of SARAH domain–mediated complex formation and provide mechanistic insights into how SARAH domain–mediated interactions influence Hippo pathway activity.

Download Full-text

Faculty Opinions recommendation of Peroxiredoxin 6 interferes with TRAIL-induced death-inducing signaling complex formation by binding to death effector domain caspase.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.5719961.5700059 ◽

2010 ◽

Author(s):

Kristiina Vuori ◽

Darren 'Ben' Finlay

Keyword(s):

Complex Formation ◽

Peroxiredoxin 6 ◽

Effector Domain ◽

Death Effector Domain ◽

Signaling Complex ◽

Death Effector

Download Full-text

Synergistic Interaction of MEK Kinase 2, c-Jun N-Terminal Kinase (JNK) Kinase 2, and JNK1 Results in Efficient and Specific JNK1 Activation

Molecular and Cellular Biology ◽

10.1128/mcb.20.7.2334-2342.2000 ◽

2000 ◽

Vol 20 (7) ◽

pp. 2334-2342 ◽

Cited By ~ 54

Author(s):

Jinke Cheng ◽

Jianhua Yang ◽

Ying Xia ◽

Michael Karin ◽

Bing Su

Keyword(s):

Complex Formation ◽

Molecular Basis ◽

Synergistic Interaction ◽

Specific Flow ◽

Mitogen Activated Protein Kinases ◽

Mapk Kinase ◽

Signaling Complex ◽

Mapk Cascades ◽

Mitogen Activated Protein ◽

Flow Of Information

ABSTRACT Mitogen-activated protein kinases (MAPKs) are activated through cascades or modules consisting of a MAPK, a MAPK kinase (MAPKK), and a MAPKK kinase (MAPKKK). Investigating the molecular basis of activation of the c-Jun N-terminal kinase (JNK) subgroup of MAPK by the MAPKKK MEKK2, we found that strong and specific JNK1 activation by MEKK2 was mediated by the MAPKK JNK kinase 2 (JNKK2) rather than by JNKK1 through formation of a tripartite complex consisting of MEKK2, JNKK2, and JNK1. No scaffold protein was required for the MEKK2-JNKK2-JNK1 tripartite-complex formation. Expression of JNK1, JNKK2, and MEKK2 significantly augmented the coprecipitation of, respectively, MEKK2-JNKK2, MEKK2-JNK1, and JNKK2-JNK1, indicating that the interaction of MEKK2, JNKK2, and JNK1 is synergistic. Finally, the JNK1 was activated more efficiently in the MEKK2-JNKK2-JNK1 complex than was the JNK1 excluded from the complex. Thus, formation of a signaling complex through synergistic interaction of a MAPKKK, a MAPKK, and a MAPK molecule like MEKK2-JNKK2-JNK1 is likely to be responsible for the efficient, specific flow of information via MAPK cascades.

Download Full-text