Regulation of Hedgehog signaling by ubiquitination

ZMYND8 Is a Regulator of Sonic Hedgehog Signaling in ATRA-Mediated Differentiation of Neuroblastoma Cells

Zinc Finger MYND (Myeloid, Nervy, and DEAF-1) type containing 8 (ZMYND8) is a crucial epigenetic regulator that plays a multifaceted role in governing a spectrum of vital cellular processes, encompassing proliferation, apoptosis, migration, tumor suppression, and differentiation. It has emerged as a key player in neuronal differentiation by orchestrating the expression of neuronal lineage-committed genes. The present study uncovers the role of ZMYND8 in regulating the Sonic Hedgehog (SHH) signaling axis, which is crucial for neuronal differentiation. Genetic deletion of ZMYND8 leads to a significant reduction in SHH pathway genes, GLI1, and PTCH1 expression during all-trans-retinoic acid (ATRA)-induced differentiation. ZMYND8 and RNA pol II S5P are found to co-occupy the GLI1 and PTCH1 gene promoters, positively impacting their gene transcription upon ATRA treatment. Interestingly, ZMYND8 is found to counteract the inhibitory effects of Cyclopamine that block the upstream SHH pathway protein SMO, resulting in enhanced neurite formation in neuroblastoma cells following their treatment with ATRA. These results indicate that ZMYND8 is an epigenetic regulator of the SHH signaling pathway and has tremendous therapeutic potential in ATRA-mediated differentiation of neuroblastoma.

Non-apoptotic caspase activation ensures the homeostasis of ovarian somatic stem cells

Current evidence has associated caspase activation with the regulation of basic cellular functions without causing apoptosis. Malfunction of non-apoptotic caspase activities may contribute to specific neurological disorders, metabolic diseases, autoimmune conditions and cancers. However, our understanding of non-apoptotic caspase functions remains limited. Here, we show that non-apoptotic caspase activation prevents the intracellular accumulation of the Patched receptor in autophagosomes and the subsequent Patched-dependent induction of autophagy in Drosophila follicular stem cells. These events ultimately sustain Hedgehog signalling and the physiological properties of ovarian somatic stem cells and their progeny under moderate thermal stress. Importantly, our key findings are partially conserved in ovarian somatic cells of human origin. These observations attribute to caspases a pro-survival role under certain cellular conditions.

Liraglutide limits the immunogenic cell death-mediated ROS propagation and PI3K/AKT inactivation after doxorubicin-induced gonadotoxicity in rats: Involvement of the canonical Hedgehog trajectory

Chemotherapy-accompanied reproductive dysfunction has lately begun to draw the attention of the scientific community owing to the irreversible impact on the patient's quality of life. Here we tended to investigate the potential role of liraglutide (LRG) in modulating the canonical Hedgehog (Hh) signaling in doxorubicin (DXR)-induced gonadotoxicity in rats. Female virgin Wistar rats were divided into 4 groups; control, DXR-treated (25 mg/kg, single i.p. injection), LRG-treated (150 μg/Kg/day, s.c) and itraconazole (ITC; 150 mg/kg/day, p.o)-pretreated group, as the Hh pathway inhibitor. Treatment with LRG potentiated the PI3K/AKT/p-GSK3β cascade and relieved the oxidative burden-induced by the DXR-driven immunogenic cell death (ICD). LRG also upregulated the expression of the Desert hedgehog ligand (DHh) and the patched-1 (PTCH1) receptor and augmented the protein level of Indian hedgehog (IHh) ligand, Gli1 and cyclin-D1 (CD1). Besides, hypertranscription of IHh, DHh, Ptch1, Smo, Gli1/2 and CD1 genes along with a transcriptional recession of Gli3 gene were reported in LRG-treated group. ITC pre-administration partially abrogated this positive effect of LRG, proving the implication of the examined pathway. Microscopically, LRG ameliorated the follicular atresia noticed in the DXR group; effect that was, at least partially, declined by ITC pre-treatment. These findings end to a conclusion that LRG treatment might hinder the DXR-associated reproductive toxicity, resultant from ROS generated by the cells undergoing ICD, and trigger follicular growth and repair by the PI3K/AKT- dependent switching-on of the canonical Hh pathway.

E3 ubiquitin ligase Wwp1 regulates ciliary dynamics of the Hedgehog receptor Smoothened

The Hedgehog pathway, critical to vertebrate development, is organized in primary cilia. Activation of signaling causes the Hedgehog receptor Ptch1 to exit cilia, allowing a second receptor, Smo, to accumulate in cilia and activate the downstream steps of the pathway. Mechanisms regulating the dynamics of these receptors are unknown, but the ubiquitination of Smo regulates its interaction with the intraflagellar transport system to control ciliary levels. A focused screen of ubiquitin-related genes identified nine required for maintaining low ciliary Smo at the basal state. These included cytoplasmic E3s (Arih2, Mgrn1, and Maea), a ciliary localized E3 (Wwp1), a ciliary localized E2 (Ube2l3), a deubiquitinase (Bap1), and three adaptors (Kctd5, Skp1a, and Skp2). The ciliary E3, Wwp1, binds Ptch1 and localizes to cilia at the basal state. Activation of signaling removes both Ptch1 and Wwp1 from cilia, thus providing an elegant mechanism for Ptch1 to regulate ciliary Smo levels.

Ubiquitin links smoothened to intraflagellar transport to regulate Hedgehog signaling

In the absence of Hedgehog ligand, patched-1 (Ptch1) localizes to cilia and prevents ciliary accumulation and activation of smoothened (Smo). Upon ligand binding, Ptch1 is removed from cilia, and Smo is derepressed and accumulates in cilia where it activates signaling. The mechanisms regulating these dynamic movements are not well understood, but defects in intraflagellar transport components, including Ift27 and the BBSome, cause Smo to accumulate in cilia without pathway activation. We find that in the absence of ligand-induced pathway activation, Smo is ubiquitinated and removed from cilia, and this process is dependent on Ift27 and BBSome components. Activation of Hedgehog signaling decreases Smo ubiquitination and ciliary removal, resulting in its accumulation. Blocking ubiquitination of Smo by an E1 ligase inhibitor or by mutating two lysine residues in intracellular loop three causes Smo to aberrantly accumulate in cilia without pathway activation. These data provide a mechanism to control Smo's ciliary level during Hedgehog signaling by regulating the ubiquitination state of the receptor.

Ubiquitin ligases and medulloblastoma: genetic markers of the four consensus subgroups identified through transcriptome datasets

The ubiquitin proteasome system regulates key cellular processes in normal and in cancer cells. Herein, we review published data on the role of ubiquitin ligases in the four major subgroups of medulloblastoma (MB). While conventional literature serves as an initial source of information on cellular pathways in MB, large publicly available datasets of gene expression can be used to add information not previously identified in the literature. By analysing the publicly available Cavalli dataset, we show that increased expression of ZNRF3 characterizes the WNT subgroup of MB. The ZNRF3 gene codes for an E3 ligase associated with WNT receptors. Loss of a copy of chromosome 6 in a subtype of the WNT group was associated with decreased expression of the gene encoding the E3 ligase RNF146. While the E3 ligase SMURF regulates SHH receptors, increased expression of the gene encoding the Cullin Ring E3 adaptor PPP2R2C was statistically a better genetic marker of the SHH group. Genes whose expression was statistically strongly related to Group 3 included the E3 ligase gene TRIM58, and the gene for the E3 ligase adaptor, PPP2R2B. Group 4 MB was associated with expression of genes encoding several E3 ligases and E3 ligase adaptors involved in ribosome biogenesis. Increased expression of the genes encoding the E3 ligase adaptors and transcription repressors ZBTB18 and ZBTB38 were also noted in subgroup 4. These data suggest that several E3 ligases and their adaptors should be investigated as therapeutic targets for subgroup specific MB brain tumors.

Whole-genome analysis of noncoding genetic variations identifies multiscale regulatory element perturbations associated with Hirschsprung disease

It is widely recognized that noncoding genetic variants play important roles in many human diseases, but there are multiple challenges that hinder the identification of functional disease-associated noncoding variants. The number of noncoding variants can be many times that of coding variants; many of them are not functional but in linkage disequilibrium with the functional ones; different variants can have epistatic effects; different variants can affect the same genes or pathways in different individuals; and some variants are related to each other not by affecting the same gene but by affecting the binding of the same upstream regulator. To overcome these difficulties, we propose a novel analysis framework that considers convergent impacts of different genetic variants on protein binding, which provides multiscale information about disease-associated perturbations of regulatory elements, genes, and pathways. Applying it to our whole-genome sequencing data of 918 short-segment Hirschsprung disease patients and matched controls, we identify various novel genes not detected by standard single-variant and region-based tests, functionally centering on neural crest migration and development. Our framework also identifies upstream regulators whose binding is influenced by the noncoding variants. Using human neural crest cells, we confirm cell stage-specific regulatory roles of three top novel regulatory elements on our list, respectively in the RET, RASGEF1A, and PIK3C2B loci. In the PIK3C2B regulatory element, we further show that a noncoding variant found only in the patients affects the binding of the gliogenesis regulator NFIA, with a corresponding up-regulation of multiple genes in the same topologically associating domain.

DUBs Activating the Hedgehog Signaling Pathway: A Promising Therapeutic Target in Cancer

The Hedgehog (HH) pathway governs cell proliferation and patterning during embryonic development and is involved in regeneration, homeostasis and stem cell maintenance in adult tissues. The activity of this signaling is finely modulated at multiple levels and its dysregulation contributes to the onset of several human cancers. Ubiquitylation is a coordinated post-translational modification that controls a wide range of cellular functions and signaling transduction pathways. It is mediated by a sequential enzymatic network, in which ubiquitin ligases (E3) and deubiquitylase (DUBs) proteins are the main actors. The dynamic balance of the activity of these enzymes dictates the abundance and the fate of cellular proteins, thus affecting both physiological and pathological processes. Several E3 ligases regulating the stability and activity of the key components of the HH pathway have been identified. Further, DUBs have emerged as novel players in HH signaling transduction, resulting as attractive and promising drug targets. Here, we review the HH-associated DUBs, discussing the consequences of deubiquitylation on the maintenance of the HH pathway activity and its implication in tumorigenesis. We also report the recent progress in the development of selective inhibitors for the DUBs here reviewed, with potential applications for the treatment of HH-related tumors.

Hedgehog Pathway Activation Alters Ciliary Signaling in Primary Hypothalamic Cultures

Primary cilia dysfunction has been associated with hyperphagia and obesity in both ciliopathy patients and mouse models of cilia perturbation. Neurons throughout the brain possess these solitary cellular appendages, including in the feeding centers of the hypothalamus. Several cell biology questions associated with primary neuronal cilia signaling are challenging to address in vivo. Here we utilize primary hypothalamic neuronal cultures to study ciliary signaling in relevant cell types. Importantly, these cultures contain neuronal populations critical for appetite and satiety such as pro-opiomelanocortin (POMC) and agouti related peptide (AgRP) expressing neurons and are thus useful for studying signaling involved in feeding behavior. Correspondingly, these cultured neurons also display electrophysiological activity and respond to both local and peripheral signals that act on the hypothalamus to influence feeding behaviors, such as leptin and melanin concentrating hormone (MCH). Interestingly, we found that cilia mediated hedgehog signaling, generally associated with developmental processes, can influence ciliary GPCR signaling (Mchr1) in terminally differentiated neurons. Specifically, pharmacological activation of the hedgehog-signaling pathway using the smoothened agonist, SAG, attenuated the ability of neurons to respond to ligands (MCH) of ciliary GPCRs. Understanding how the hedgehog pathway influences cilia GPCR signaling in terminally differentiated neurons could reveal the molecular mechanisms associated with clinical features of ciliopathies, such as hyperphagia-associated obesity.

Structural basis of βTrCP1-associated GLI3 processing

Controlled ubiquitin-mediated protein degradation is essential for various cellular processes. GLI family regulates the transcriptional events of the sonic hedgehog pathway genes that are implicated in almost one fourth of human tumors. GLI3 phosphorylation by Ser/Thr kinases is a primary factor for their transcriptional activity that incurs the formation of both GLI3 repressor and activator forms. GLI3 processing is triggered in an ubiquitin-dependent manner via SCF^βTrCP1 complex; however, structural characterization, mode of action based on sequence of phosphorylation signatures and induced conformational readjustments remain elusive. Here, through structural analysis and molecular dynamics simulation assays, we explored comparative binding pattern of GLI3 phosphopeptides against βTrCP1. A comprehensive and thorough analysis demarcated GLI3 presence in the binding cleft shared by inter-bladed binding grooves of β-propeller. Our results revealed the involvement of all seven WD40 repeats of βTrCP1 in GLI3 interaction. Conversely, GLI3 phosphorylation pattern at primary protein kinase A (PKA) sites and secondary casein kinase 1 (CK1) or glycogen synthase kinase 3 (GSK3) sites was carefully evaluated. Our results indicated that GLI3 processing depends on the 19 phosphorylation sites (849, 852, 855, 856, 860, 861, 864, 865, 868, 872, 873, 876, 877, 880, 899, 903, 906, 907 and 910 positions) by a cascade of PKA, GSK3β and CSKI kinases. The presence of a sequential phosphorylation in the binding induction of GLI3 and βTrCP1 may be a hallmark to authenticate GLI3 processing. We speculate that mechanistic information of the individual residual contributions through structure-guided approaches may be pivotal for the rational design of specific and more potent inhibitors against activated GLI3 with a special emphasis on the anticancer activity.

Differential Expression of Genes for Ubiquitin Ligases in Medulloblastoma Subtypes

Using publically available datasets on gene expression in medulloblastoma (MB) subtypes, we selected genes for ubiquitin ligases and identified statistically those that best predicted each of the four major MB subgroups as separate disease entities. We identify a gene coding for an ubiquitin ligase, ZNRF3, whose overexpression alone can predict the WNT subgroup for 100% in the Pfister dataset. For the SHH subgroup, we identify a gene for a regulatory subunit of the protein phosphatase 2A (PP2A), PPP2R2C, as the major predictor among the E3 ligases genes. The ubiquitin and ubiquitin-like conjugation database (UUCD) lists PPP2R2C as coding for a Cullin Ring ubiquitin ligase adaptor. For group 3 MBs, the best ubiquitin ligase predictor was PPP2R2B, a gene which codes for another regulatory subunit of the PP2A holoenzyme. For group 4, the best E3 gene predictors were MID2, ZBTB18, and PPP2R2A, which codes for a third PP2A regulatory subunit. Heatmap analysis of the E3 gene data shows that expression of ten genes for ubiquitin ligases can be used to classify MBs into the four major consensus subgroups. This was illustrated by analysis of gene expression of ubiquitin ligases of the Pfister dataset and confirmed in the dataset of Cavalli. We conclude that genes for ubiquitin ligases can be used as genetic markers for MB subtypes and that the proteins coded for by these genes should be investigated as subtype specific therapeutic targets for MB.

Primary Cilia as Signaling Hubs in Health and Disease

Primary cilia detect extracellular cues and transduce these signals into cells to regulate proliferation, migration, and differentiation. Here, the function of primary cilia as signaling hubs of growth factors and morphogens is in focus. First, the molecular mechanisms regulating the assembly and disassembly of primary cilia are described. Then, the role of primary cilia in mediating growth factor and morphogen signaling to maintain human health and the potential mechanisms by which defects in these pathways contribute to human diseases, such as ciliopathy, obesity, and cancer are described. Furthermore, a novel signaling pathway by which certain growth factors stimulate cell proliferation through suppression of ciliogenesis is also described, suggesting novel therapeutic targets in cancer.

Pancreatic Cell Fate Determination Relies on Notch Ligand Trafficking by NFIA

Notch is activated globally in pancreatic progenitors; however, for progenitors to differentiate into endocrine cells, they must escape Notch activation to express Neurogenin-3. Here, we find that the transcription factor nuclear factor I/A (NFIA) promotes endocrine development by regulating Notch ligand Dll1 trafficking. Pancreatic deletion of NFIA leads to cell fate defects, with increased duct and decreased endocrine formation, while ectopic expression promotes endocrine formation in mice and human pancreatic progenitors. NFIA-deficient mice exhibit dysregulation of trafficking-related genes including increased expression of Mib1, which acts to target Dll1 for endocytosis. We find that NFIA binds to the Mib1 promoter, with loss of NFIA leading to an increase in Dll1 internalization and enhanced Notch activation with rescue of the cell fate defects after Mib1 knockdown. This study reveals NFIA as a pro-endocrine factor in the pancreas, acting to repress Mib1, inhibit Dll1 endocytosis and thus promote escape from Notch activation.

Decoding Somatic Driver Gene Mutations and Affected Signaling Pathways in Human Medulloblastoma Subgroups

Medulloblastoma is the most common malignant pediatric brain tumor. Prior studies have concentrated their efforts studying the four molecular subgroups: SHH, Wnt, group 3, and group 4. SHH and Wnt are driven by their canonical pathways. Groups 3 and 4 are highly metastatic and associated with aberrations in epigenetic regulators. Recent developments in the field have revealed that these subgroups are not as homogenous as previously believed. The objective of this study is to investigate the involvement of somatic driver gene mutations in these medulloblastoma subgroups. We obtained medulloblastoma data from the Catalogue of Somatic Mutations in Cancer (COSMIC), which contains distinct samples that were not previously studied in a large cohort. We identified somatic driver gene mutations and the signaling pathways affected by these driver genes for medulloblastoma subgroups using bioinformatics tools. We have revealed novel infrequent drivers in these subgroups that contribute to our understanding of tumor heterogeneity in medulloblastoma. Normally SHH signaling is activated in the SHH subgroup, however, we determined gain-of-function mutations in ubiquitin ligase (CUL1) that inhibit Gli-mediated transcription. This suggests a potential hindrance in SHH signaling for some patients. For group 3, gain-of-function in the inhibitor of proinflammatory cytokines (HIVEP3) suggests an immunosuppressive phenotype and thus a more hostile tumor microenvironment. Surprisingly, group 4 tumors possess mutations that may prompt the activation of Wnt signaling through gain-of-function mutations in MUC16 and PCDH9. These infrequent mutations detected in this study could be due to subclonal or spatially restricted alterations. The investigation of aberrant driver gene mutations can lead to the identification of new drug targets and a greater understanding of human medulloblastoma heterogeneity.

Fsh-Pc-Sce complex mediates active transcription of Cubitus interruptus (Ci)

The Hedgehog (Hh) signaling pathway plays important roles in both embryonic development and adult tissue homeostasis. Such biological functions are mediated by the transcription factor Cubitus interruptus (Ci). Yet the transcriptional regulation of the effector Ci itself is poorly investigated. Through an RNAi-based genetic screen, we identified that female sterile (1) homeotic (Fsh), a transcription co-activator, directly activates Ci transcription. Biochemistry assays demonstrated physical interactions among Fsh, Sex combs extra (Sce), and Polycomb (Pc). Functional assays further showed that both Pc and Sce are required for Ci expression, which is not likely mediated by the derepression of Engrailed (En), a repressor of Ci, in Pc or Sce mutant cells. Finally, we provide evidence showing that Pc/Sce facilitates the binding of Fsh at Ci locus and that the physical interaction between Fsh and Pc is essential for Fsh-mediated Ci transcription. Taken together, we not only uncover that Ci is transcriptionally regulated by Fsh-Pc-Sce complex but also provide evidence for the coordination between Fsh and PcG proteins in transcriptional regulation.

UbcD1 regulates Hedgehog signaling by directly modulating Ci ubiquitination and processing

The Hh pathway controls many morphogenetic processes in metazoans and plays important roles in numerous pathologies and in cancer. Hh signaling is mediated by the activity of the Gli/Ci family of transcription factors. Several studies in Drosophila have shown that ubiquitination by the ubiquitin E3 ligases Slimb and Rdx(Hib) plays a crucial role in controlling Ci stability dependent on the levels of Hh signals. If Hh levels are low, Slimb adds K11- and K48-linked poly-ubiquitin chains on Ci resulting in partial degradation. Ubiquitin E2 enzymes are pivotal in determining the topologies of ubiquitin chains. However, which E2 enzymes participate in the selective ubiquitination-degradation of Ci remains elusive. Here, we find that the E2 enzyme UbcD1 negatively regulates Hh signaling activity in Drosophila wing disks. Genetic and biochemical analyses in wing disks and in cultured cells reveal that UbcD1 directly controls Ci stability. Interestingly, UbcD1 is found to be selectively involved in Slimb-mediated Ci degradation. Finally, we show that the homologs of UbcD1 play a conserved role in modulating Hh signaling in vertebrates.

Diversifying Selection Between Pure-Breed and Free-Breeding Dogs Inferred from Genome-Wide SNP Analysis

Domesticated species are often composed of distinct populations differing in the character and strength of artificial and natural selection pressures, providing a valuable model to study adaptation. In contrast to pure-breed dogs that constitute artificially maintained inbred lines, free-ranging dogs are typically free-breeding, i.e., unrestrained in mate choice. Many traits in free-breeding dogs (FBDs) may be under similar natural and sexual selection conditions to wild canids, while relaxation of sexual selection is expected in pure-breed dogs. We used a Bayesian approach with strict false-positive control criteria to identify FST-outlier SNPs between FBDs and either European or East Asian breeds, based on 167,989 autosomal SNPs. By identifying outlier SNPs located within coding genes, we found four candidate genes under diversifying selection shared by these two comparisons. Three of them are associated with the Hedgehog (HH) signaling pathway regulating vertebrate morphogenesis. A comparison between FBDs and East Asian breeds also revealed diversifying selection on the BBS6 gene, which was earlier shown to cause snout shortening and dental crowding via disrupted HH signaling. Our results suggest that relaxation of natural and sexual selection in pure-breed dogs as opposed to FBDs could have led to mild changes in regulation of the HH signaling pathway. HH inhibits adhesion and the migration of neural crest cells from the neural tube, and minor deficits of these cells during embryonic development have been proposed as the underlying cause of "domestication syndrome." This suggests that the process of breed formation involved the same genetic and developmental pathways as the process of domestication.

Set7 mediated Gli3 methylation plays a positive role in the activation of Sonic Hedgehog pathway in mammals

Hedgehog signaling plays very important roles in development and cancers. Vertebrates have three transcriptional factors, Gli1, Gli2 and Gli3. Among them, Gli3 is a very special transcriptional factor which closely resembles Cubitus interruptus (Ci, in Drosophila) structurally and functionally as a ‘double agent’ for Shh target gene expression. Here we show that Gli3 full-length, but not the truncated form, can be methylated at K436 and K595. This methylation is specifically catalyzed by Set7, a lysine methyltransferase (KMT). Methylation at K436 and K595 respectively increases the stability and DNA binding ability of Gli3, resulting in an enhancement of Shh signaling activation. Furthermore, functional experiments indicate that the Gli3 methylation contributes to the tumor growth and metastasis in non-small cell lung cancer in vitro and in vivo. Therefore, we propose that Set7 mediated methylation is a novel PTM of Gli3, which positively regulates the transactivity of Gli3 and the activation of Shh signaling.

DOI:http://dx.doi.org/10.7554/eLife.15690.001

Cells in mammals need to be able to communicate with each other to enable them to work together in tissues and organs. A signaling pathway called Hedgehog signaling plays a crucial role in carrying information between cells in developing embryos, but if it is active at other times it can also promote the development of cancers.

The Hedgehog signaling pathway regulates the activity of several proteins, including one called Gli3. When the Hedgehog signaling pathway is not active, Gli3 is able to switch off certain genes in the cells. On the other hand, when the signaling pathway is active, Gli3 changes shape so that it is able to activate its target genes instead. It is thought that this shape change is triggered by the addition (or removal) of chemical tags to Gli3. So far, researchers have reported that several different types of chemical tags can modify the activity of Gli3. However, it is not clear whether another type of chemical tag – known as a methyl tag – is involved in regulating Gli3.

Fu et al. studied Hedgehog signaling in mice. The experiments show that an enzyme called Set7 can modify Gli3 by adding methyl tags to certain sites in the protein. This modification makes the protein’s structure more stable and helps it to bind to the target genes. Further experiments show that these methyl groups contribute to the progression of lung cancer. Fu et al.’s findings expand our understanding of how chemical tags can alter the cells’ response to Hedgehog signaling activity. Future challenges are to understand exactly how Set7 and Gli3 interact and to develop drugs that can block this interaction, which may have the potential to treat cancer.

DOI:http://dx.doi.org/10.7554/eLife.15690.002

Smoothened regulation in response to Hedgehog stimulation

The Hedgehog (Hh) signaling pathway play critical roles in embryonic development and adult tissue homeostasis. A critical step in Hh signal transduction is how Hh receptor Patched (Ptc) inhibits the atypical G protein-coupled receptor Smoothened (Smo) in the absence of Hh and how this inhibition is release by Hh stimulation. It is unlikely that Ptc inhibits Smo by direct interaction. Here we discuss how Hh regulates the phosphorylation and ubiquitination of Smo, leading to cell surface and ciliary accumulation of Smo in Drosophila and vertebrate cells, respectively. In addition, we discuss how PI(4)P phospholipid acts in between Ptc and Smo to regulate Smo phosphorylation and activation in response to Hh stimulation.

Intravenous and oral practolol in the acute stages of myocardial infarction

The influence of routine administration of the beta adrenoceptor blocking drug practolol on the outcome of acute myocardial infarction has been studied in 94 patients. The study was restricted to patients under the age of 70 experiencing their first myocardial infarction and in whom there was no contraindication to beta blockade. In the treated group an initial dose intravenous practolol 15 mg was followed by five oral doses of practolol 200 mg at 12 h intervals. A significant reduction in heart rate and systolic blood pressure was apparent in the treated group within 2 h. No difference was detectable in the course of the acute stage of the illness between treated and control patients, apart from a significant reduction in the incidence of atrial fibrillation among those receiving practolol. Patients with inferior infarctions showed a tendency to develop potentially harmful bradycardia and hypotension on receiving practolol which lead to withdrawal of the drug in many cases. At regular review over 7 mth no detectable difference emerged between the treated and control groups in the incidence of cardiac failure, death or reinfarction.