IκBζ is an essential mediator of immunity to oropharyngeal candidiasis

Fungal infections are a global threat; yet, there are no licensed vaccines to any fungal pathogens. Th17 cells mediate immunity to Candida albicans, particularly oropharyngeal candidiasis (OPC), but essential downstream mechanisms remain unclear. In the murine model of OPC, IκBζ (Nfkbiz, a non-canonical NF-κB transcription factor) was upregulated in an interleukin (IL)-17-dependent manner and was essential to prevent candidiasis. Deletion of Nfkbiz rendered mice highly susceptible to OPC. IκBζ was dispensable in hematopoietic cells and acted partially in the suprabasal oral epithelium to control OPC. One prominent IκBζ-dependent gene target was β-defensin 3 (BD3) (Defb3), an essential antimicrobial peptide. Human oral epithelial cells required IκBζ for IL-17-mediated induction of BD2 (DEFB4A, human ortholog of mouse Defb3) through binding to the DEFB4A promoter. Unexpectedly, IκBζ regulated the transcription factor Egr3, which was essential for C. albicans induction of BD2/DEFB4A. Accordingly, IκBζ and Egr3 comprise an antifungal signaling hub mediating mucosal defense against oral candidiasis.

SARS-CoV-2 ORF8 Mediates Signals in Macrophages and Monocytes through MyD88 Independently of the IL-17 Receptor

SARS-CoV-2 has caused an estimated 7 million deaths worldwide to date. A secreted SARS-CoV-2 accessory protein, known as open reading frame 8 (ORF8), elicits inflammatory pulmonary cytokine responses and is associated with disease severity in COVID-19 patients. Recent reports proposed that ORF8 mediates downstream signals in macrophages and monocytes through the IL-17 receptor complex (IL-17RA, IL-17RC). However, generally IL-17 signals are found to be restricted to the nonhematopoietic compartment, thought to be due to rate-limiting expression of IL-17RC. Accordingly, we revisited the capacity of IL-17 and ORF8 to induce cytokine gene expression in mouse and human macrophages and monocytes. In SARS-CoV-2-infected human and mouse lungs, IL17RC mRNA was undetectable in monocyte/macrophage populations. In cultured mouse and human monocytes and macrophages, ORF8 but not IL-17 led to elevated expression of target cytokines. ORF8-induced signaling was fully preserved in the presence of anti-IL-17RA/RC neutralizing Abs and in Il17ra-/- cells. ORF8 signaling was also operative in Il1r1-/- bone marrow-derived macrophages. However, the TLR/IL-1R family adaptor MyD88, which is dispensable for IL-17R signaling, was required for ORF8 activity yet MyD88 is not required for IL-17 signaling. Thus, we conclude that ORF8 transduces inflammatory signaling in monocytes and macrophages via MyD88 independently of the IL-17R.

A gut-oral microbiome-driven axis controls oropharyngeal candidiasis through retinoic acid

A side effect of antibiotics is outgrowth of the opportunistic fungus Candida albicans in the oropharynx (oropharyngeal candidiasis, OPC). IL-17 signaling is vital for immunity to OPC, but how the microbiome impacts antifungal immunity is not well understood. Mice in standard specific pathogen-free (SPF) conditions are resistant to OPC, whereas we show that germ-free (GF) or antibiotic-treated mice are susceptible. Oral type 17 cells and IL-17-dependent responses were impaired in antibiotic-treated and GF mice. Susceptibility could be rescued in GF mice by mono-colonization with segmented filamentous bacterium (SFB), an intestine-specific constituent of the microbiota. SFB protection was accompanied by restoration of oral IL-17+CD4+ T cells and gene signatures characteristic of IL-17 signaling. Additionally, RNA-Seq revealed induction of genes in the retinoic acid (RA) and RA receptor-α (RARα) pathway. Administration of RA rescued immunity to OPC in microbiome-depleted or GF mice, while RAR inhibition caused susceptibility in immunocompetent animals. Surprisingly, immunity to OPC was independent of serum amyloids. Moreover, RAR inhibition did not alter oral type 17 cytokine levels. Thus, mono-colonization with a component of the intestinal microflora confers protection against OPC by type 17 and RA/RARα, which act in parallel to promote antifungal immunity. In principle, manipulation of the microbiome could be harnessed to maintain antifungal immunity.

Arid5a Mediates an IL-17-Dependent Pathway That Drives Autoimmunity but Not Antifungal Host Defense

IL-17 contributes to the pathogenesis of certain autoimmune diseases, but conversely is essential for host defense against fungi. Ab-based biologic drugs that neutralize IL-17 are effective in autoimmunity but can be accompanied by adverse side effects. Candida albicans is a commensal fungus that is the primary causative agent of oropharyngeal and disseminated candidiasis. Defects in IL-17 signaling cause susceptibility to candidiasis in mice and humans. A key facet of IL-17 receptor signaling involves RNA-binding proteins, which orchestrate the fate of target mRNA transcripts. In tissue culture models we showed that the RNA-binding protein AT-rich interaction domain 5A (Arid5a) promotes the stability and/or translation of multiple IL-17-dependent mRNAs. Moreover, during oropharyngeal candidiasis, Arid5a is elevated within the oral mucosa in an IL-17-dependent manner. However, the contribution of Arid5a to IL-17-driven events in vivo is poorly defined. In this study, we used CRISPR-Cas9 to generate mice lacking Arid5a. Arid5a -/- mice were fully resistant to experimental autoimmune encephalomyelitis, an autoimmune setting in which IL-17 signaling drives pathology. Surprisingly, Arid5a -/- mice were resistant to oropharyngeal candidiasis and systemic candidiasis, similar to immunocompetent wild-type mice and contrasting with mice defective in IL-17 signaling. Therefore, Arid5a-dependent signals mediate pathology in autoimmunity and yet are not required for immunity to candidiasis, indicating that selective targeting of IL-17 signaling pathway components may be a viable strategy for development of therapeutics that spare IL-17-driven host defense.

The m6A reader IMP2 directs autoimmune inflammation through an IL-17- and TNFα-dependent C/EBP transcription factor axis

Excessive cytokine activity underlies many autoimmune conditions, particularly through the interleukin-17 (IL-17) and tumor necrosis factor-α (TNFα) signaling axis. Both cytokines activate nuclear factor κB, but appropriate induction of downstream effector genes requires coordinated activation of other transcription factors, notably, CCAAT/enhancer binding proteins (C/EBPs). Here, we demonstrate the unexpected involvement of a posttranscriptional "epitranscriptomic" mRNA modification [N6-methyladenosine (m6A)] in regulating C/EBPβ and C/EBPδ in response to IL-17A, as well as IL-17F and TNFα. Prompted by the observation that C/EBPβ/δ-encoding transcripts contain m6A consensus sites, we show that Cebpd and Cebpb mRNAs are subject to m6A modification. Induction of C/EBPs is enhanced by an m6A methylase "writer" and suppressed by a demethylase "eraser." The only m6A "reader" found to be involved in this pathway was IGF2BP2 (IMP2), and IMP2 occupancy of Cebpd and Cebpb mRNA was enhanced by m6A modification. IMP2 facilitated IL-17-mediated Cebpd mRNA stabilization and promoted translation of C/EBPβ/δ in response to IL-17A, IL-17F, and TNFα. RNA sequencing revealed transcriptome-wide IL-17-induced transcripts that are IMP2 influenced, and RNA immunoprecipitation sequencing identified the subset of mRNAs that are directly occupied by IMP2, which included Cebpb and Cebpd Lipocalin-2 (Lcn2), a hallmark of autoimmune kidney injury, was strongly dependent on IL-17, IMP2, and C/EBPβ/δ. Imp2-/- mice were resistant to autoantibody-induced glomerulonephritis (AGN), showing impaired renal expression of C/EBPs and Lcn2 Moreover, IMP2 deletion initiated only after AGN onset ameliorated disease. Thus, posttranscriptional regulation of C/EBPs through m6A/IMP2 represents a previously unidentified paradigm of cytokine-driven autoimmune inflammation.

RNA m6A methylation guides IL-17-driven autoimmunity through IMP2-dependent regulation of C/EBP transcription factors

Dysregulated activity of IL-17 underlies many autoimmune conditions, but the molecular mechanisms by which IL-17 mediates pathogenic inflammation remain poorly understood. IL-17 regulates pathogenic inflammatory genes by two key transcription factor classes, NF-κB and CCAAT/Enhancer Binding (C/EBP) proteins. Surprisingly little is known about mechanisms that activate C/EBPs. In seeking to understand how IL-17 upregulates C/EBPs, we found that IL-17 signaling enhanced Cebpd mRNA stability, concomitant with increased levels of C/EBPδ translation. In contrast, IL-17 had only a marginal inductive effect on Cebpb mRNA, yet C/EBPβ protein was strongly upregulated. Examination of Cebpb and Cebpd noncoding sequences identified consensus sites for N6-methyladenosine (m6A) modification, an epitranscriptomic mark that influences mRNA fate. knockdown of the m6A ‘writer’ METTL3 decreased C/EBP expression, which was reversed by the ‘eraser’ FTO. Moreover, we found that loss of an unusual m6A ‘reader’ IGF2BP2 (IMP2), an RNA binding protein known to control mRNA stability, impaired IL-17 induction of C/EBPs. IMP2 bound directly to Cebps transcripts, leading to enhanced Cebpd half-life and enhanced translation of both C/EBPs. Transcriptomic analysis revealed that IMP2 regulates C/EBP-dependent genes, including IL-6 and Lcn2. Lcn2 is a biomarker of autoantibody-induced glomerulonephritis (AGN), a setting of IL-17-driven inflammatory nephritis. Imp2−/− mice were resistant to AGN, which was linked to impaired upregulation of C/EPBs and Lcn2 in kidney. Thus, IL-17-induced autoimmunity is mediated through m6A-dependent post-transcriptional regulation of C/EBP transcription factors.

Fractured lateral epicondyle with associated elbow dislocation

We describe a case series involving a very unusual injury in children, i.e. a Milch 1 fracture of the lateral condyle with an associated dislocation of the elbow. This fracture configuration is normally stable as the intact capitellotrochlear groove serves as a lateral buttress for the coronoid-olecranon ridge of the ulna. In this series, however, each patient had an associated dislocation. These injuries usually present as a clinical dislocation and if the elbow is manipulated before radiographic imaging, the fracture line can be difficult to see on the post-reduction films. We recommend that all patients with a dislocated elbow should have elbow stability assessed under general anaesthesia, because a missed lateral condylar injury can lead to abnormalities in carrying angle, epiphyseolysis or an unstable elbow.

Effect of a rigid ankle-foot orthosis on hamstring length in children with hemiplegia

Eighteen children with hemiplegia, mean age 8 years 5 months, underwent gait analysis and musculoskeletal modelling using specially designed software. The maximum lengths of the hamstrings were determined for each child walking in and out of an ankle-foot orthosis (AFO). The muscles were deemed to be short if shorter than the normal average -1SD. In bare feet 8 participants had short medial hamstrings with a higher proportion of these in the less involved individuals. All participants showed an increase in maximum hamstring length when wearing an AFO. In all but one child this was sufficient to restore hamstring length to within normal limits. These finding suggest that hamstring pathology in hemiplegic gait is usually secondary to more distal lower limb pathology.

First crystal structure of Rubisco from a green alga, Chlamydomonas reinhardtii

The crystal structure of Rubisco (ribulose 1,5-bisphosphate carboxylase/oxygenase) from the unicellular green alga Chlamydomonas reinhardtii has been determined to 1.4 A resolution. Overall, the structure shows high similarity to the previously determined structures of L8S8 Rubisco enzymes. The largest difference is found in the loop between beta strands A and B of the small subunit (betaA-betaB loop), which is longer by six amino acid residues than the corresponding region in Rubisco from Spinacia. Mutations of residues in the betaA-betaB loop have been shown to affect holoenzyme stability and catalytic properties. The information contained in the Chlamydomonas structure enables a more reliable analysis of the effect of these mutations. No electron density was observed for the last 13 residues of the small subunit, which are assumed to be disordered in the crystal. Because of the high resolution of the data, some posttranslational modifications are unambiguously apparent in the structure. These include cysteine and N-terminal methylations and proline 4-hydroxylations.

Relevance of the popliteal angle to hamstring length in cerebral palsy crouch gait

The popliteal angle is a widely used clinical means of assessing hamstring length in cerebral palsy patients. The relevance of the popliteal angle as a measure of hamstring length was assessed in this prospective study. Sixteen patients with cerebral palsy with crouch gait had their conventional and modified popliteal angles measured by nine observers on two separate occasions. With use of the conventional and modified forms of the test, 74 and 70%, respectively, of the observed variability was inter-and intraobserver related. The range of SDs for each observer using the conventional test was 7.1-13.6 degrees (average 10.9 degrees ), and with use of the modified form of the test, the range was 6.3-4.2 degrees (average 10.5 degrees ). The maximum hamstring length of each subject during gait was determined by three-dimensional modelling of their lower limbs. The modified popliteal angle measurements of the most repeatable observer demonstrated an inverse relationship between modified popliteal angle and maximum hamstring length (p < 0.01) and muscle excursion (p < 0.01). Only 10 of 32 limbs had short medial hamstrings.

Botulinum toxin A in hamstring spasticity

Hamstring injection of Botulinum toxin A (BtA) may have a role in the conservative management of flexed knee gait in cerebral palsy or in simulating the effect of surgery. Ten children who were likely to require future hamstring lengthening were injected. Short term outcome was assessed by clinical examination and 3-D gait analysis. Mean popliteal angle decreased by 16 degrees and maximum knee extension in stance increased by 8 degrees, the latter relapsing by 12 weeks. Mean pelvic tilt tended to increase suggesting that isolated hamstring weakening be approached with caution. Energy cost of walking was not significantly changed in six of the ten patients. A small increase in knee extension in stance was often associated with patient satisfaction. There are theoretical grounds for expecting an associated increased longitudinal muscle growth after BtA injection.

Scapulothoracic arthrodesis for patients with facioscapulohumeral muscular dystrophy

Ten scapulothoracic arthrodesis procedures were performed in six patients with facioscapulohumeral muscular dystrophy in order to improve considerably restricted activities of daily living. Four of these procedures were bilateral. The duration of follow-up ranged from 28 to 120 months. All patients reported improved function in activities of daily living. Active shoulder abduction was improved by an average of 44 degrees, and active flexion increased by 56 degrees. There was no deterioration in improved upper limb function with time. Complications included pneumothorax, atelectasis, pleural effusion and re-exploration for a segment of retained drain.

Botulinum toxin A compared with stretching casts in the treatment of spastic equinus: a randomised prospective trial

Conservative therapies for equinus in cerebral palsy may help to postpone calf surgery in younger children. This study reports a prospective randomised trial of intramuscular botulinum toxin A (BtA) as an alternative to serial casting in 20 children with a dynamic component to calf equinus. Outcome was assessed in the short term to show the effect of one treatment cycle. Assessments were by clinical examination, video gait analysis, and three-dimensional gait analysis. BtA was of efficacy similar to that of serial casting. Tone reduction in the BtA group allowed a more prolonged improvement in passive dorsiflexion, which may allow more opportunity for increase in muscle length. Gait analysis showed an improved mean ankle kinematic pattern in a subsection of both groups, which was maintained at 12 weeks in the BtA group, whereas the cast group relapsed. There were fewer side effects in the BtA group. Median time to reintervention was similar.

Structure of a product complex of spinach ribulose-1,5-bisphosphate carboxylase/oxygenase

The crystal structure of an activated complex of ribulose-1,5-bisphosphate carboxylase/oxygenase from spinach and its product 3-phosphoglycerate has been determined to 2.2 A resolution. The structure is of the open form with the active site accessible to the solvent as observed in the structures of the activated ligand-free enzyme and the complex of the activated enzyme with the substrate ribulose-1,5-bisphosphate. Two molecules of 3-phosphoglycerate are bound per active site. The phosphates of both molecules bind approximately at the same position as the phosphates of ribulose-1,5-bisphosphate or the six-carbon intermediate analogue 2-carboxyarabinitol-1,5-bisphosphate, but one product molecule is swung out from the active site with its carboxylate group pointing toward solution. The present structure points to direct participation of the active site side chain of lysine 175 in later stages of catalysis. This possibility is discussed in the light of mutagenesis studies.

The structure of the complex between rubisco and its natural substrate ribulose 1,5-bisphosphate

The three-dimensional structure of the complex of ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco; EC 4.1.1.39) from spinach with its natural substrate ribulose 1,5-bisphosphate (RuBP) has been determined both under activating and non-activating conditions by X-ray crystallography to a resolution of 2.1 A and 2.4 A, respectively. Under activating conditions, the use of calcium instead of magnesium as the activator metal ion enabled us to trap the substrate in a stable complex for crystallographic analysis. Comparison of the structure of the activated and the non-activated RuBP complexes shows a tighter binding for the substrate in the non-activated form of the enzyme, in line with previous solution studies. In the non-activated complex, the substrate triggers isolation of the active site by inducing movements of flexible loop regions of the catalytic subunits. In contrast, in the activated complex the active site remains partly open, probably awaiting the binding of the gaseous substrate. By inspection of the structures and by comparison with other complexes of the enzyme we were able to identify a network of hydrogen bonds that stabilise a closed active site structure during crucial steps in the reaction. The present structure underlines the central role of the carbamylated lysine 201 in both activation and catalysis, and completes available structural information for our proposal on the mechanism of the enzyme.

A common structural basis for the inhibition of ribulose 1,5-bisphosphate carboxylase by 4-carboxyarabinitol 1,5-bisphosphate and xylulose 1,5-bisphosphate

Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the carboxylation of ribulose 1,5-bisphosphate. The reaction catalyzed by Rubisco involves several steps, some of which can occur as partial reactions, forming intermediates that can be isolated. Analogues of these intermediates are potent inhibitors of the enzyme. We have studied the interactions with the enzyme of two inhibitors, xylulose 1,5-bisphosphate and 4-carboxyarabinitol 1,5-bisphosphate, by x-ray crystallography. Crystals of the complexes were formed by cocrystallization under activating conditions. In addition, 4-carboxyarabinitol 1,5-bisphosphate was soaked into preformed activated crystals of the enzyme. The result of these experiments was the release of the activating CO2 molecule as well as the metal ion from the active site when the inhibitors bound to the enzyme. Comparison with the structure of an activated complex of the enzyme indicates that the structural basis for the release of the activator groups is a distortion of the metal binding site due to the different geometry of the C-3 hydroxyl of the inhibitors. Both inhibitors induce closure of active site loops despite the inactivated state of the enzyme. Xylulose 1,5-bisphosphate binds in a hydrated form at the active site.

Purification and mass spectrometric analysis of ADP-ribosylation factor proteins from Xenopus egg cytosol

The GTP analog GTP gamma S potently inhibits nuclear envelope assembly in cell-free Xenopus egg extracts. GTP gamma S does not affect vesicle binding to chromatin but blocks vesicle fusion. Fusion inhibition by GTP gamma S is mediated by a soluble factor, initially named GSF (GTP gamma S-dependent soluble factor). We previously showed that vesicles pretreated with GTP gamma S plus recombinant mammalian ARF1 were inhibited for fusion, suggesting that "GSF activity" was due to the ARF (ADP-ribosylation factor) family of small GTP-binding proteins. To ask if any soluble proteins other than ARF also inhibited vesicle fusion in the pretreatment assay, we purified GSF activity from Xenopus egg cytosol. At all steps in the purification, fractions containing ARF, but no other fractions, showed GSF activity. The purified GSF was identified as Xenopus ARF by immunoblotting and peptide sequence analysis. Reverse phase HPLC and mass spectrometry revealed that GSF contained at least three distinct ARF proteins, all of which copurified through three chromatography steps. The most abundant isoform was identified as ARF1 (62% of the total GSF), because its experimentally determined mass of 20 791 Da matched within experimental error that predicted by the sequence of the Xenopus ARF1 cDNA, which is reported here. The second-most abundant isoform (25% of GSF activity) was identified as ARF3. We concluded that ARF is most likely the only soluble protein that inhibits nuclear vesicle fusion after pretreatment with GTP gamma S.

Structural transitions during activation and ligand binding in hexadecameric Rubisco inferred from the crystal structure of the activated unliganded spinach enzyme

Activation of ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco; EC 4.1.1.39) by CO2 involves carbamylation of Lys 201 and the subsequent binding of a magnesium ion to complete the active site. The refined crystal structure of activated Rubisco shows that the magnesium ligands are Asp 203, Glu 204, the carbamate of Lys 201, and three water molecules. Structural differences between the unactivated and activated forms are minimal. Substrate binding replaces water ligands around the metal and triggers substantial structural changes in loops covering the active site. This leads to a contraction and tightening of the structure of the large subunits with the movements transmitted to and modulated by the small subunits.

Mass-spectrometric analysis of ADP-ribosylation factors from bovine brain: identification and evidence for homogeneous acylation with the C14:0 fatty acid (myristate)

The two proteins from bovine brain previously shown to be required for the guanosine 5'-[gamma-thio]triphosphate-dependent inhibition of a well-characterized intra-Golgi transport assay, termed GGBF and GGBF, have been definitively identified as members of the ADP-ribosylation factor (ARF) family by electrospray MS analysis of the intact proteins, and of their tryptic fragments. Extensive protein-sequence information obtained from this analysis identified GGBF and GGBF as bovine ARF1 and ARF3 respectively. The sequence of bovine ARF3, which had not previously been determined, appears identical to that predicted from the rat and human ARF3 cDNAs. Further analysis of the N-terminal tryptic fragments of both bovine ARFs demonstrates N-terminal acylation solely with the C14:0 fatty acid (myristate). This finding establishes that the previously reported specific-activity difference between ARF1 and ARF3 in the intra-Golgi transport assay is not due to lipid heterogeneity at the N-terminus. This finding also indicates that the heterogeneity of N-terminal fatty-acyl groups previously observed on other myristoylated proteins is not universal.

Cytosolic ADP-ribosylation factors are not required for endosome-endosome fusion but are necessary for GTP gamma S inhibition of fusion

A specific role for ADP-ribosylation factors (ARFs) in in vitro endosome-endosome fusion has been proposed (Lenhard, J. M., Kahn, R. A., and Stahl, P. D. (1992) J. Biol. Chem. 267, 13047-13052). However, in vivo studies have failed to support a function for ARFs in the endocytic pathway, since an antagonist of ARF activities, brefeldin A, does not interfere with receptor internalization (Schonhorn, J. E., and Wessling-Resnick, M. (1994) Mol. Cell. Biochem. 135, 159-164). This controversy surrounding the exact function of ARF in endocytic vesicle traffic prompted us to critically re-examine the involvement of ARFs in cell-free endosome fusion. Cytosol depleted of ARF activity was capable of supporting in vitro endocytic vesicle fusion but failed to support inhibition of this reaction in the presence of guanosine 5'-3-O-(thio)triphosphate (GTP gamma S). Addition of purified ARF1 restored the ability of the ARF-depleted cytosol to inhibit endosome fusion when incubated with GTP gamma S. Both endocytic vesicle fusion and the GTP gamma S-mediated inhibition of vesicle fusion were unaffected by brefeldin A. Moreover, the ATP requirement and kinetics of cell-free fusion are not altered by brefeldin A or depletion of cytosolic ARFs. These results suggest that cytosolic ARFs are not necessary for endosomal vesicle fusion in vitro but are responsible for inhibition of fusion in the presence of GTP gamma S and cytosolic factors in a brefeldin A-resistant manner.

Cytosolic ARFs are required for vesicle formation but not for cell-free intra-Golgi transport: evidence for coated vesicle-independent transport

We investigated the role of ADP-ribosylation factors (ARFs) in Golgi function using biochemical and morphological cell-free assays. An ARF-free cytosol produced from soluble Chinese hamster ovary (CHO) extracts supports intra-Golgi transport by a mechanism that is biochemically indistinguishable from control transport reactions: ARF-free transport reactions are NSF-dependent, remain sensitive to the donor Golgi-specific inhibitor ilimaquinone, and exhibit kinetics that are identical to that of control reactions containing ARFs. In contrast, ARF-free cytosol does not support the formation of coated vesicles on Golgi cisternae. However, vesicle formation is reconstituted upon the addition of ARF1. These data suggest that neither soluble ARFs nor coated vesicle formation are essential for transport. We conclude that cell-free intra-Golgi transport proceeds via a coated vesicle-independent mechanism regardless of vesicle formation on Golgi cisternae.

A role for ADP-ribosylation factor in nuclear vesicle dynamics

Two distinct steps in nuclear envelope assembly can be assayed in vitro: the protein-mediated binding of nuclear-specific vesicles to chromatin, and the subsequent fusion of these vesicles to enclose the chromatin within a double nuclear membrane. Nuclear vesicle fusion, like fusion in the secretory pathway, requires ATP and cytosol and is inhibited by nonhydrolysable GTP analogues. The sensitivity of nuclear vesicle fusion to GTP-gamma S requires a GTP-dependent soluble factor, the properties of which are strikingly similar to a GTP-dependent Golgi binding factor (GGBF) that inhibits Golgi vesicle fusion in the presence of GTP-gamma S and belongs to the ADP-ribosylation factor (ARF) family of small GTPases. In the presence of GTP-gamma S, ARF proteins and alpha-, beta-, gamma-, delta-COP ('coatomer') subunits are associated with Golgi transport vesicles, but the exact roles of ARF proteins in secretion are not yet understood. We report here that purified ARF1 and GGBF have GTP-dependent soluble factor activity in the nuclear vesicle fusion assay. Our results show that the function of ARF is not limited to the Golgi apparatus, and indicate that there may be a link between the formation of nuclear vesicles during mitosis and proteins involved in secretion.

Two distinct members of the ADP-ribosylation factor family of GTP-binding proteins regulate cell-free intra-Golgi transport

We have used an intra-Golgi transport assay to identify GTP-binding proteins involved in regulation of protein traffic. Two soluble proteins of 20 kd were purified by their ability to mediate GTP gamma S-dependent inhibition of transport. These GTP-dependent Golgi binding factors, or GGBFs, exhibit a 3-fold difference in activity and are differentiated by their hydrophobicity, isoelectric points, and apparent size. Removal of 80% of GGBFs from cytosol abolishes GTP gamma S sensitivity but does not affect inhibition by aluminum fluoride. We demonstrate that GGBFs are members of the ADP-ribosylation factor (ARF) family. Recombinant ARF1 exhibits GGBF activity and myristoylation is required. The distinct biochemical properties of GGBFs indicate that members of the ARF family may have related but distinct functions in intracellular transport.

An immunochemical study of avian pancreatic polypeptide: the nature of the principal epitope

Structural features contributing to the antigenic recognition of the small globular hormone avian pancreatic polypeptide (APP) by a polyclonal antiserum have been defined using a solution phase radioimmunoassay technique. Cross-reactivity studies with PP homologues suggest that the surface residues within the alpha-helix of the peptide may be antigenic, whereas hydrophilicity and atomic mobility predictive methods implicate the molecules beta-turn region. Immunochemical data and circular dichroism measurements on a timed trypsin digest of APP indicate that the secondary structure of the alpha-helix is vital for the molecule's immunological competence. Immunoreactivities of iodinated derivatives of APP, as well as that of peptide fragments of APP and its homologues, support the importance of teritary structure involving the interaction of the polyproline and alpha helices. The highly mobile C-terminal residues 34-36 (His-Arg-Tyr-NH2) have been found by immunological analysis to be unimportant. Arginine residue 33, which has been conserved through vertebrate evolution, is a major antigenic contributor, since a large decrease in immunoreactivity, not accompanied by a significant change in conformation, was observed upon specific removal of this residue by carboxypeptidase B. These results are consistent with a "discontinuous" epitopic model for APP in which Arg-33 and exposed residues in the alpha-helix are principal components of an epitope or epitopes mediated by the secondary and tertiary structures of the molecule.

Isolated dislocation of the trapezium

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Iodinated derivatives of the hormone avian pancreatic polypeptide

Reaction of avian pancreatic polypeptide with an iodine monochloride reagent at both pH 4 and pH 7.5 results in the differential modification of the four tyrosine residues in this peptide hormone. A total of 19 distinct iodinated derivatives were isolated by reverse-phase high-performance liquid chromatography, and their sites of iodination were characterized by both tryptic mapping and leucine aminopeptidase techniques coupled with HPLC. The pH 4 reaction produced 16 derivatives which, overall, represented substantial iodination at each tyrosine residue, whereas the pH 7.5 reaction was more directed, producing only 7 derivatives. Iodination at the C-terminal tyrosineamide 36 predominated at both pH values, and diiodo-Tyr 36 was found in the majority of the pH 7.5 derivatives. The relative of the four tyrosine residues with ICl were as follows: at pH 7.5, Tyr 36 much greater than Tyr 21 much greater than Tyr 27 greater than Tyr 7; at pH 4, Tyr 36 greater than Tyr 27 greater than Tyr 7 greater than Tyr 21.

Spinal anaesthesia for surgical correction of fracture of the proximal femur

One hundred and one patients underwent surgical correction of fractures of the proximal femur under spinal anaesthesia. There were 14 deaths in the first three months following surgery. Advancing age, poor pre-anaesthetic status, reduced pre-operative mobility and deteriorating mental function were reliable prognostic indicators of fatal outcome. Spinal anaesthesia for this type of surgery may well be the technique of choice because it avoids the use of drugs which depress the respiratory, cardiac and central nervous system. It also reduces the need for potent post-operative analgesics with similar depressant effects, and may afford some protection against thromboembolic complications. The very low early mortality in this series testifies to the safety of the anaesthetic technique.

Surgical management of thoracic kyphosis in adolescents

Twenty-seven patients of a group of twenty-nine who underwent posterior spine fusion using Harrington compression instrumentation for Scheuermann's disease or postural roundback deformity were reviewed with a mean follow-up of 27.6 months. The mean curve before operation was 72 degrees and at review, 46.1 degrees. The mean loss of correction in the fusion from initial examination to final follow-up was 5.7 degrees. This procedure can achieve satisfactory correction of deformity as well as pain relief. We think that Harrington compression instrumentation and spine fusion is indicated in selected cases of roundback deformity.