scholarly journals Gain-of-function Shh mutants activate Smo in cis independent of Ptch1/2 function

2017 ◽  
Author(s):  
Catalina Casillas ◽  
Henk Roelink
Keyword(s):  
Sonic Hedgehog ◽  
Gain Of Function ◽  
Shh Signaling ◽  
Rich Domain ◽  
Intrinsic Mechanism ◽  
Cell Autonomy ◽  
Catalytic Motif ◽  
In Cis ◽  
Cysteine Rich Domain

AbstractSonic Hedgehog (Shh) signaling is characterized by strict non-cell autonomy; cells expressing Shh do not respond to their ligand. Here, we identify several Shh mutations that gain the ability to activate the Hedgehog (Hh) pathway in cis. This activation requires the extracellular cysteine rich domain of Smoothened, but is otherwise independent of Ptch1/2. Many of the identified mutations disrupt either a highly conserved catalytic motif found in peptidases or an a-helix domain frequently mutated in holoprosencephaly-causing SHH alleles. The expression of gain-of-function mutants often results in the accumulation of unprocessed Shh pro-peptide, a form of Shh we demonstrate is sufficient to activate the Hh response cell-autonomously. Our results demonstrate that Shh is capable of activating the Hh pathway via Smo independently of Ptch1/2, and that it harbors an intrinsic mechanism that prevents cell-autonomous activation of the pathway to favor non-cell autonomous signaling.

scholarly journals Hedgehog-Interacting Protein is a multimodal antagonist of Hedgehog signalling

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Samuel C. Griffiths ◽  
Rebekka A. Schwab ◽  
Kamel El Omari ◽  
Benjamin Bishop ◽  
Ellen J. Iverson ◽  
...  
Keyword(s):  
Cell Surface ◽  
Sonic Hedgehog ◽  
High Avidity ◽  
Interacting Protein ◽  
Surface Receptors ◽  
Terminal Domain ◽  
Inhibitory Function ◽  
Rich Domain ◽  
Covalently Linked ◽  
Cysteine Rich Domain

AbstractHedgehog (HH) morphogen signalling, crucial for cell growth and tissue patterning in animals, is initiated by the binding of dually lipidated HH ligands to cell surface receptors. Hedgehog-Interacting Protein (HHIP), the only reported secreted inhibitor of Sonic Hedgehog (SHH) signalling, binds directly to SHH with high nanomolar affinity, sequestering SHH. Here, we report the structure of the HHIP N-terminal domain (HHIP-N) in complex with a glycosaminoglycan (GAG). HHIP-N displays a unique bipartite fold with a GAG-binding domain alongside a Cysteine Rich Domain (CRD). We show that HHIP-N is required to convey full HHIP inhibitory function, likely by interacting with the cholesterol moiety covalently linked to HH ligands, thereby preventing this SHH-attached cholesterol from binding to the HH receptor Patched (PTCH1). We also present the structure of the HHIP C-terminal domain in complex with the GAG heparin. Heparin can bind to both HHIP-N and HHIP-C, thereby inducing clustering at the cell surface and generating a high-avidity platform for SHH sequestration and inhibition. Our data suggest a multimodal mechanism, in which HHIP can bind two specific sites on the SHH morphogen, alongside multiple GAG interactions, to inhibit SHH signalling.

scholarly journals The Evolution of the Scavenger Receptor Cysteine-Rich Domain of the Class A Scavenger Receptors

2015 ◽  
Vol 6 ◽  
Author(s):  
Nicholas V. L. Yap ◽  
Fiona J. Whelan ◽  
Dawn M. E. Bowdish ◽  
G. Brian Golding
Keyword(s):  
Scavenger Receptor ◽  
Scavenger Receptors ◽  
Class A ◽  
Rich Domain ◽  
Cysteine Rich Domain

scholarly journals New Tricks for an Old (Hedge)Hog: Sonic Hedgehog Regulation of Astrocyte Function

Cells ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1353
Author(s):  
A. Denise R. Garcia
Keyword(s):  
Signaling Pathway ◽  
Sonic Hedgehog ◽  
Synapse Formation ◽  
Inflammatory Responses ◽  
Molecular Signaling ◽  
Synaptic Organization ◽  
Shh Signaling ◽  
Broad Array ◽  
And Function ◽  
Molecular Signaling Pathway

The Sonic hedgehog (Shh) molecular signaling pathway is well established as a key regulator of neurodevelopment. It regulates diverse cellular behaviors, and its functions vary with respect to cell type, region, and developmental stage, reflecting the incredible pleiotropy of this molecular signaling pathway. Although it is best understood for its roles in development, Shh signaling persists into adulthood and is emerging as an important regulator of astrocyte function. Astrocytes play central roles in a broad array of nervous system functions, including synapse formation and function as well as coordination and orchestration of CNS inflammatory responses in pathological states. Neurons are the source of Shh in the adult, suggesting that Shh signaling mediates neuron–astrocyte communication, a novel role for this multifaceted pathway. Multiple roles for Shh signaling in astrocytes are increasingly being identified, including regulation of astrocyte identity, modulation of synaptic organization, and limitation of inflammation. This review discusses these novel roles for Shh signaling in regulating diverse astrocyte functions in the healthy brain and in pathology.

scholarly journals The unusual structure of the PiggyMac cysteine-rich domain reveals zinc finger diversity in PiggyBac-related transposases

Mobile DNA ◽  
2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Marc Guérineau ◽  
Luiza Bessa ◽  
Séverine Moriau ◽  
Ewen Lescop ◽  
François Bontems ◽  
...  
Keyword(s):  
Zinc Finger ◽  
Dna Cleavage ◽  
Trichoplusia Ni ◽  
Catalytic Domain ◽  
Structural Diversity ◽  
Paramecium Tetraurelia ◽  
Lysine Methylation ◽  
Unusual Structure ◽  
Rich Domain ◽  
Cysteine Rich Domain

Abstract Background Transposons are mobile genetic elements that colonize genomes and drive their plasticity in all organisms. DNA transposon-encoded transposases bind to the ends of their cognate transposons and catalyze their movement. In some cases, exaptation of transposon genes has allowed novel cellular functions to emerge. The PiggyMac (Pgm) endonuclease of the ciliate Paramecium tetraurelia is a domesticated transposase from the PiggyBac family. It carries a core catalytic domain typical of PiggyBac-related transposases and a short cysteine-rich domain (CRD), flanked by N- and C-terminal extensions. During sexual processes Pgm catalyzes programmed genome rearrangements (PGR) that eliminate ~ 30% of germline DNA from the somatic genome at each generation. How Pgm recognizes its DNA cleavage sites in chromatin is unclear and the structure-function relationships of its different domains have remained elusive. Results We provide insight into Pgm structure by determining the fold adopted by its CRD, an essential domain required for PGR. Using Nuclear Magnetic Resonance, we show that the Pgm CRD binds two Zn2+ ions and forms an unusual binuclear cross-brace zinc finger, with a circularly permutated treble-clef fold flanked by two flexible arms. The Pgm CRD structure clearly differs from that of several other PiggyBac-related transposases, among which is the well-studied PB transposase from Trichoplusia ni. Instead, the arrangement of cysteines and histidines in the primary sequence of the Pgm CRD resembles that of active transposases from piggyBac-like elements found in other species and of human PiggyBac-derived domesticated transposases. We show that, unlike the PB CRD, the Pgm CRD does not bind DNA. Instead, it interacts weakly with the N-terminus of histone H3, whatever its lysine methylation state. Conclusions The present study points to the structural diversity of the CRD among transposases from the PiggyBac family and their domesticated derivatives, and highlights the diverse interactions this domain may establish with chromatin, from sequence-specific DNA binding to contacts with histone tails. Our data suggest that the Pgm CRD fold, whose unusual arrangement of cysteines and histidines is found in all PiggyBac-related domesticated transposases from Paramecium and Tetrahymena, was already present in the ancestral active transposase that gave rise to ciliate domesticated proteins.

scholarly journals Elucidation of Binding Determinants and Functional Consequences of Ras/Raf-Cysteine-rich Domain Interactions

2000 ◽  
Vol 275 (29) ◽  
pp. 22172-22179 ◽  
Author(s):  
Jason G. Williams ◽  
Jonelle K. Drugan ◽  
Gwan-Su Yi ◽  
Geoffrey J. Clark ◽  
Channing J. Der ◽  
...  
Keyword(s):  
Rich Domain ◽  
Domain Interactions ◽  
Functional Consequences ◽  
Binding Determinants ◽  
Cysteine Rich Domain

Itraconazole Attenuates Peritoneal Fibrosis Through Its Effect on the Sonic Hedgehog Signaling Pathway in Mice

2018 ◽  
Vol 48 (6) ◽  
pp. 456-464 ◽  
Author(s):  
Jin Sug Kim ◽  
Kyung Sook Cho ◽  
Seon Hwa Park ◽  
Sang Ho Lee ◽  
Ji Hwan Lee ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Sonic Hedgehog ◽  
Transforming Growth Factor ◽  
Smooth Muscle Actin ◽  
Isotonic Saline ◽  
Control Group ◽  
Protective Effects ◽  
Peritoneal Fibrosis ◽  
Shh Signaling ◽  
Itraconazole Treatment

Background: Peritoneal fibrosis is a devastating complication of peritoneal dialysis. However, its precise mechanism is unclear, and specific treatments have not yet been established. Recent evidence suggests that the sonic hedgehog (SHH) signaling pathway is involved in tissue fibrogenesis. Drugs that inhibit this pathway are emerging in the field of anti-fibrosis therapy. Itraconazole, an anti-fungal agent, was also recently recognized as an inhibitor of the SHH signaling pathway. In this study, we used a mouse model to investigate whether the SHH signaling pathway is involved in the development of peritoneal fibrosis and the effects of itraconazole on peritoneal fibrosis. Methods: Peritoneal fibrosis was induced by intraperitoneal (IP) injection of 0.1% chlorhexidine gluconate (CG) solution every other day for 4 weeks, with or without itraconazole treatment (20 mg/kg, IP injection on a daily basis). Male C57BL/6 mice were divided into 4 groups: saline group, saline plus itraconazole group, CG group, and CG plus itraconazole group. Isotonic saline was administered intraperitoneally to the control group. The peritoneal tissues were evaluated for histological changes, expression of fibrosis markers, and the main components of the SHH signaling pathway. Results: Peritoneal thickening was evident in the CG group and was significantly decreased by itraconazole administration (80.4 ± 7.7 vs. 28.2 ± 3.8 µm, p < 0.001). The expression of the following SHH signaling pathway components was upregulated in the CG group and suppressed by itraconazole treatment: SHH, patched, smoothened, and glioma-associated oncogene transcription factor 1. The IP injection of CG solution increased the expression of fibrosis markers such as α-smooth muscle actin and transforming growth factor-β1 in the peritoneal tissues. Itraconazole treatment significantly decreased the expression of these markers. Conclusion: Our study provides the first evidence that the SHH signaling pathway may be implicated in peritoneal fibrosis. It also demonstrates that itraconazole treatment has protective effects on peritoneal fibrosis through the regulation of the SHH signaling pathway. These findings suggest that blockage of the SHH signaling pathway is a potential therapeutic strategy for peritoneal fibrosis.

scholarly journals Non-cell autonomous inhibition of the Shh pathway due to impaired cholesterol biosynthesis requires Ptch1/2

2020 ◽  
Author(s):  
Carian Jägers ◽  
Henk Roelink
Keyword(s):  
Sonic Hedgehog ◽  
Birth Defects ◽  
Cholesterol Synthesis ◽  
Cholesterol Biosynthesis ◽  
Shh Signaling ◽  
Shh Pathway ◽  
Opitz Syndrome ◽  
Cholesterol Precursors ◽  
G Protein Coupled ◽  
Mutant Cells

AbstractBirth defects due to congenital errors in enzymes involved cholesterol synthesis like Smith-Lemli-Opitz syndrome (SLOS) and Lathosterolosis cause an accumulation of cholesterol precursors and a deficit in cholesterol. The phenotype of both SLOS and Lathosterolosis have similarities to syndromes associated with abnormal Sonic hedgehog (Shh) signaling, consistent with the notion that impaired cholesterol signaling can cause reduced Shh signaling. Two multipass membrane proteins play central roles in Shh signal transduction, the putative Resistance, Nodulation and Division (RND) antiporters Ptch1 and Ptch2, and the G-protein coupled receptor Smoothened (Smo). Sterols have been suggested as cargo for Ptch1, while Smo activity can affected both positively and negatively by steroidal molecules. We demonstrate that mESCs mutant for 7-dehydroxycholesterol reductase (7dhcr) or sterol-C5-desaturase (sc5d) reduce the Hh response in nearby wildtype cells when grown in mosaic organoids. This non-cell autonomous inhibitory activity of the mutant cells required the presence of both Ptch1 and Ptch2. These observations support a model in which late cholesterol precursors that accumulate in cells lacking 7DHCR are the cargo for Ptch1 and Ptch2 activity that mediates the non-cell autonomous inhibition of Smo.

scholarly journals Prophylactic Activation of Shh Signaling Attenuates TBI-Induced Seizures in Zebrafish by Modulating Glutamate Excitotoxicity through Eaat2a

Biomedicines ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 32
Author(s):  
James Hentig ◽  
Leah J. Campbell ◽  
Kaylee Cloghessy ◽  
Mijoon Lee ◽  
William Boggess ◽  
...  
Keyword(s):  
Sonic Hedgehog ◽  
Cognitive Deficits ◽  
The United States ◽  
Glutamate Excitotoxicity ◽  
Ionotropic Glutamate Receptors ◽  
Chemical Signaling ◽  
Shh Signaling ◽  
Central Nervous System Damage ◽  
Weight Drop ◽  
Post Traumatic

Approximately 2 million individuals experience a traumatic brain injury (TBI) every year in the United States. Secondary injury begins within minutes after TBI, with alterations in cellular function and chemical signaling that contribute to excitotoxicity. Post-traumatic seizures (PTS) are experienced in an increasing number of TBI individuals that also display resistance to traditional anti-seizure medications (ASMs). Sonic hedgehog (Shh) is a signaling pathway that is upregulated following central nervous system damage in zebrafish and aids injury-induced regeneration. Using a modified Marmarou weight drop on adult zebrafish, we examined PTS following TBI and Shh modulation. We found that inhibiting Shh signaling by cyclopamine significantly increased PTS in TBI fish, prolonged the timeframe PTS was observed, and decreased survival across all TBI severities. Shh-inhibited TBI fish failed to respond to traditional ASMs, but were attenuated when treated with CNQX, which blocks ionotropic glutamate receptors. We found that the Smoothened agonist, purmorphamine, increased Eaat2a expression in undamaged brains compared to untreated controls, and purmorphamine treatment reduced glutamate excitotoxicity following TBI. Similarly, purmorphamine reduced PTS, edema, and cognitive deficits in TBI fish, while these pathologies were increased and/or prolonged in cyclopamine-treated TBI fish. However, the increased severity of TBI phenotypes with cyclopamine was reduced by cotreating fish with ceftriaxone, which induces Eaat2a expression. Collectively, these data suggest that Shh signaling induces Eaat2a expression and plays a role in regulating TBI-induced glutamate excitotoxicity and TBI sequelae.

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