COVID-19 social-distancing measures altered the epidemiology of facial injury: a United Kingdom-Australia comparative study

The purpose of this study was to undertake a retrospective cross-sectional analysis to compare the frequency and characteristics of facial injury presentations at a UK and an Australian tertiary referral hospital during the implementation of COVID-19 social-distancing measures. The primary predictor variables were a heterogeneous set of factors grouped into logical categories: demographics, injury mechanisms and site, and management. The primary outcome variable was the presentation of a hard or soft tissue facial injury. A descriptive statistical analysis was undertaken on the assembled data. The study found a clinical and statistically significant reduction in the frequency (absolute number) of facial injuries at each study site. In addition, a striking similarity common in both countries was an increase in the number of facial injuries due to falls and a reduction in facial injuries due to interpersonal violence. Conservative (non-operative) management of facial injury increased at both sites. The implementation of COVID-19 social-distancing public health measures, which aimed to limit community transmission of the coronavirus, had a secondary serendipitous effect of reducing the frequency of facial injury presentations and altering their epidemiological characteristics at both a UK and Australian tertiary referral hospital.

The clinical and inflammatory relationships between periodontitis and chronic obstructive pulmonary disease

AIM

To investigate associations between periodontitis and chronic obstructive pulmonary disease (COPD) with and without alpha-1 antitrypsin deficiency (AATD), including neutrophil functions implicated in tissue damage.

METHODS

The presence and severity of periodontitis (using two international criteria) and lung disease were assessed in 156 COPD patients with and without AATD accounting for common confounding factors. Saliva and systemic inflammatory markers were measured by ELISA together with neutrophil migration.

RESULTS

COPD and AATD patients exhibited higher prevalence of periodontitis (COPD 95%; AATD 88%) than reported in unselected community-dwelling populations even when risk factors (age, smoking history, socio-economic status and dental habits) were considered. Periodontitis severity associated with lung disease severity (AATD, periodontitis versus no periodontitis; FEV1 = 56% versus 99% predicted; TLCO = 59% versus 81% predicted, p < .0001 for both). Neutrophil migratory accuracy declined in stage II-IV periodontitis patients with COPD or AATD compared to COPD or AATD with no or stage I periodontitis. Improved dental habits appeared to be associated with a reduction in exacerbation frequency in COPD.

CONCLUSION

The results support shared pathophysiology between periodontitis and COPD, especially when associated with AATD. This may reflect an amplification of neutrophilic inflammation and altered neutrophil functions, already described in periodontitis, COPD and AATD.

Simvastatin Improves Neutrophil Function and Clinical Outcomes in Pneumonia. A Pilot Randomized Controlled Clinical Trial

Rationale: Population studies suggest improved sepsis outcomes with statins, but the results of randomized controlled trials in patients with sepsis and organ dysfunction in critical care settings have broadly been negative. In vitro data suggest that statins modulate age-related neutrophil functions, improving neutrophil responses to infection, but only in older patients and at high doses.Objectives: To determine if high-dose simvastatin improves neutrophil functions and is safe and tolerated in hospitalized older adults with community-acquired pneumonia with sepsis (CAP + S) not admitted to critical care.Methods: We conducted a randomized, double-blind, placebo-controlled pilot study of simvastatin 80 mg or placebo for 7 days for patients with CAP + S aged 55 years or older admitted to a secondary care hospital. The Day 4 primary endpoint was change in neutrophil extracellular trap formation (NETosis). Day 4 secondary endpoints included neutrophil chemotaxis, safety and tolerability, Sequential Organ Failure Assessment score, mortality, readmission, and markers of tissue degradation/inflammation.Measurements and Main Results: Four days of simvastatin adjuvant therapy in patients with CAP + S was associated with improvements in systemic neutrophil function (NETosis and chemotaxis), a reduction in systemic neutrophil elastase burden, and improved Sequential Organ Failure Assessment scores compared with placebo. A post hoc analysis demonstrated that simvastatin therapy was associated with improved hospitalization-free survival compared with placebo. Simvastatin was well tolerated in this elderly and multimorbid patient group with common coprescription of macrolide antibiotics.Conclusions: This pilot study supports high-dose simvastatin as an adjuvant therapy for CAP + S in an older and milder disease cohort than assessed previously. A definitive multicenter study is now warranted in this population to assess the likelihood of benefit and harm.Clinical trial registered with EudraCT (2012-00343-29).

Understanding the role of neutrophils in chronic inflammatory airway disease

Airway neutrophilia is a common feature of many chronic inflammatory lung diseases and is associated with disease progression, often regardless of the initiating cause. Neutrophils and their products are thought to be key mediators of the inflammatory changes in the airways of patients with chronic obstructive pulmonary disease (COPD) and have been shown to cause many of the pathological features associated with disease, including emphysema and mucus hypersecretion. Patients with COPD also have high rates of bacterial colonisation and recurrent infective exacerbations, suggesting that neutrophil host defence mechanisms are impaired, a concept supported by studies showing alterations to neutrophil migration, degranulation and reactive oxygen species production in cells isolated from patients with COPD. Although the role of neutrophils is best described in COPD, many of the pathological features of this disease are not unique to COPD and also feature in other chronic inflammatory airway diseases, including asthma, cystic fibrosis, alpha-1 anti-trypsin deficiency, and bronchiectasis. There is increasing evidence for immune cell dysfunction contributing to inflammation in many of these diseases, focusing interest on the neutrophil as a key driver of pulmonary inflammation and a potential therapeutic target than spans diseases. This review discusses the evidence for neutrophilic involvement in COPD and also considers their roles in alpha-1 anti-trypsin deficiency, bronchiectasis, asthma, and cystic fibrosis. We provide an in-depth assessment of the role of the neutrophil in each of these conditions, exploring recent advances in understanding, and finally discussing the possibility of common mechanisms across diseases.

Pulmonary Infections in the Elderly Lead to Impaired Neutrophil Targeting, Which Is Improved by Simvastatin

RATIONALE

Dysregulated neutrophil functions with age and sepsis are described. Statins are associated with improved infection survival in some observational studies, but trials in critically ill patients have not shown benefit. Statins also alter neutrophil responses in vitro.

OBJECTIVES

To assess neutrophil migratory accuracy with age during respiratory infections and determine if and how a statin intervention could alter these blunted responses.

METHODS

The migratory accuracy of blood neutrophils from young (aged <35 yr) and old (aged >60 yr) patients in health and during a lower respiratory tract infection, community-acquired pneumonia, and pneumonia associated with sepsis was assessed with and without simvastatin. In vitro results were confirmed in a double-blind randomized clinical trial in healthy elders. Cell adhesion markers were assessed.

MEASUREMENTS AND MAIN RESULTS

In vitro neutrophil migratory accuracy in the elderly deteriorated as the severity of the infectious pulmonary insult increased, without recovery at 6 weeks. Simvastatin rescued neutrophil migration with age and during mild to moderate infection, at high dose in older adults, but not during more severe sepsis. Confirming in vitro results, high-dose (80-mg) simvastatin improved neutrophil migratory accuracy without impeding other neutrophil functions in a double-blind randomized clinical trial in healthy elders. Simvastatin modified surface adhesion molecule expression and activity, facilitating accurate migration in the elderly.

CONCLUSIONS

Infections in older adults are associated with prolonged, impaired neutrophil migration, potentially contributing to poor outcomes. Statins improve neutrophil migration in vivo in health and in vitro in milder infective events, but not in severe sepsis, supporting their potential utility as an early intervention during pulmonary infections. Clinical trial registered with www.clinicaltrialsregister.eu (2011-002082-38).

The provision of surgical tracheostomies by maxillofacial surgeons in the UK: time for a dedicated tracheostomy team?

Surgical tracheostomy is a commonly provided service by surgical teams for patients in intensive care where percutaneous dilatational tracheostomy is contraindicated. A number of factors may interfere with its provision on shared emergency operating lists, potentially prolonging the stay in intensive care. We undertook a two-part project to examine the factors that might delay provision of surgical tracheostomy in the intensive care unit. The first part was a prospective audit of practice within the University Hospital Coventry. This was followed by a telephone survey of oral and maxillofacial surgery units throughout the UK. In the intensive care unit at University Hospital Coventry, of 39 referrals, 21 (53.8%) were delayed beyond 24 hours. There was a mean (standard deviation) time to delay of 2.2 days (0.9 days) and the most common cause of delay was surgeon decision, accounting for 13 (61.9%) delays. From a telephone survey of 140 units nationwide, 40 (28.4%) were regularly involved in the provision of surgical tracheostomies for intensive care and 17 (42.5%) experienced delays beyond 24 hours, owing to a combination of theatre availability (76.5%) and surgeon availability (47.1%). There is case for having a dedicated tracheostomy team and provisional theatre slot to optimise patient outcomes and reduce delays. We aim to implement such a move within our unit and audit the outcomes prospectively following this change.

Statin therapy in patients with community-acquired pneumonia

Community-acquired pneumonia (CAP) is the leading cause of death from infection in developed countries. There is evidence of an association between improved survival from infection and statin use. The possible beneficial effects of statins are complicated by the common use of macrolide antibiotics for pneumonia, with current guidance suggesting that concurrent macrolide and statin use is contraindicated.We conducted an observational study of statin use in patients with CAP. Of 2,067 patients with CAP, 30.4% were on statin therapy at admission. Statin users were more likely to survive the admission (p<0.001). In addition, we conducted a survey of doctors and found that knowledge regarding concurrent macrolide and statin use was lacking.These data suggest a potential role of statins in the management of CAP. Further research using high-dose statins is required to assess their safe use in subjects with mild to moderate infections.

Repurposing Treatments to Enhance Innate Immunity. Can Statins Improve Neutrophil Functions and Clinical Outcomes in COPD?

Drug classes used in the treatment of Chronic Obstructive Pulmonary Disease (COPD) have not changed for many years, and none to date have shown disease-modifying activity. Statins are used to help reduce cardiovascular risk, which is high in many patients with COPD. Their use has been associated with improvements in some respiratory manifestations of disease and reduction in all-cause mortality, with greatest reductions seen in patients with the highest inflammatory burden. The mechanism for these effects is poorly understood. Neutrophils are key effector cells in COPD, and correlate with disease severity and inflammation. Recent in vitro studies have shown neutrophil functions are dysregulated in COPD and this is thought to contribute both to the destruction of lung parenchyma and to the poor responses seen in infective exacerbations. In this article, we will discuss the potential utility of statins in COPD, with a particular emphasis on their immune-modulatory effects as well as presenting new data regarding the effects of statins on neutrophil function in vitro.

Aberrant neutrophil functions in stable chronic obstructive pulmonary disease: the neutrophil as an immunotherapeutic target

Chronic obstructive pulmonary disease (COPD) is a common, progressive and debilitating chronic inflammatory condition affecting the lungs, with significant systemic manifestations and co-morbidities. Smoking cigarettes is the main risk factor, but only a fifth of smokers have clinically significant airflow obstruction and the inflammation persists after smoking cessation. This suggests that smoking (and exposure to other inhaled toxins) may be necessary but not sufficient to cause COPD. Neutrophils are believed central to COPD and their accumulation and degranulation are associated with tissue damage, increased inflammation and disordered tissue repair. It was assumed that neutrophil activity and function were appropriate in COPD, responding to the presence of high levels of inflammation in the lung. However more recent studies of neutrophil function (including migration, reactive oxygen species generation, degranulation, phagocytosis and extracellular trap (NET) production) suggest that there is a general impairment in COPD neutrophil responses that predispose towards increased inflammation and reduced bacterial clearance. This may be amenable to correction and manipulating neutrophil intracellular pathways (such as phosphoinositide-3-kinase signalling) appears to restore some key COPD neutrophil responses. Targeting neutrophil intra-cellular signalling may provide a means to normalise neutrophil behaviour in COPD. This could lead to improvements in disease outcomes by reducing extraneous inflammatory burden. However further studies are needed to determine if these findings are relevant in vivo and whether this would impact positively upon health and disease.

Sternoclavicular joint pseudo-tumour: a case report and literature review

This case report describes the development of a post-treatment enlargement of the sternoclavicular joint, diagnosed as a pseudo-tumour, in a patient who had previously undergone radical neck dissection and post-operative radiotherapy for metastatic mucoepidermoid carcinoma. Although pseudo-tumour has been previously reported in the surgical literature, it remains an uncommonly recognized condition. We present a review of the literature and discuss the condition's pathogenesis. We also highlight its importance to both the surgeon and the oncologist when considering the differential diagnosis of a swelling in the clavicular region, typically occurring following radical surgery for malignant disease in the neck.

Osteomyelitis complicating osteopetrosis--a case report

Osteomyelitis of the jaws is uncommon but can be a complication of extraction or exposure of teeth in patients who are immunosuppressed or have undergone radiotherapy to the head and neck region. We report a case of osteomyelitis in a patient who has osteopetrosis. The initial clinical presentation was that of an infected retained root, secondary to denture trauma to the supporting tissues. Radiological interpretation was difficult owing to the increased bone density and surgical exploration revealed only a dense region of necrotic bone.

Free tissue flaps: a new way to position the pedicle

A simple and atraumatic method for passing the pedicle from a free flap through a subcutaneous tunnel using a modified Yankauer sucker tube is described.

Tritiated thymidine and bromodeoxyuridine double-labelling studies on growth factors and oral epithelial proliferation in the mouse

Mouse tongue epithelium is characterized by a circadian variation in the number of cells undergoing DNA synthesis. Groups of male BDF1 mice were followed over 48 h and a double-labelling method with tritiated thymidine and bromodeoxyuridine used to determine S-phase labelling indices, together with cell influx to and cell efflux from S, at 4-hourly time points. Control animals exhibited diurnal peaks in labelling index at 03:00 with trough activity 12 h later at 15:00. Cell influx peaked at 23:00 with troughs occurring between 11:00 to 15:00. Peak cell efflux occurred at 07:00 with trough activity at 19:00. Animals injected with epidermal growth factor at 05:00 demonstrated a significant fall in both influx and efflux throughout the 48-h period (P < 0.001), but with preservation of labelling indices, suggesting a slower transit of cells through S-phase, whereas epidermal growth factor injected at 15:00 only produced a significant rise in cell-efflux values. Adrenergic stimulation by intravenous phenylephrine/isoprenaline injection at both 05:00 and 15:00 resulted in a significant rise in cell efflux (P < 0.001), although there was also a rise in labelling index in the 15:00 group (P < 0.001). Animals injected with calmodulin at 05:00 demonstrated a significant reduction in labelling index throughout the 48-h period (P < 0.001), but maintained control values for cell influx and efflux, suggesting faster transit of cells through S. Calmodulin injection at 15:00 produced only a significant reduction in cell influx (P < 0.001). Administration of exogenous growth factors significantly alters the normal rhythmical proliferation of oral epithelial cells in a mouse model. These effects appear to be both growth factor- and time-dependent, and may have both physiological and pathological implications.

Complications of percutaneous gastrostomy in patients with head and neck cancer--an analysis of 42 consecutive patients

A total of 42 patients, who underwent insertion of a percutaneous gastrostomy tube prior to resection for oral squamous cell carcinoma, were investigated to examine the incidence and severity of complications associated with use of this technique. The team performing the procedure and the grade of operator was noted together with any subsequent complications and their outcome. Previously reported complication rates were 2.7-2.8% and 6-7.1% for major and minor complications, respectively, but, in this series, a major complication rate of 22.5% and minor complication rate of 17.5% were identified. The findings of this study have led to the introduction of a further prospective audit of this technique in the maxillofacial unit and a more selective policy of PEG prescription for patients undergoing resection for head and neck cancer.

Ketorolac and diclofenac for postoperative pain relief following oral surgery

A double-blind clinical study was designed to compare the efficacy and safety of intramuscular and oral ketorolac, a new non-steroidal anti-inflammatory analgesic with that of diclofenac and placebo for patients undergoing removal of impacted mandibular third molar teeth. Results showed that both analgesic preparations were more effective than placebo (p = 0.0029) and that ketorolac provided a similar degree of pain relief to that of diclofenac. It is concluded that ketorolac is important new addition to the available intra-muscular NSAID preparations.

Cardiopulmonary performance following changes in position and the administration of intravenous Diazemuls

Twenty healthy volunteers entered a study to assess cardiopulmonary responses, as measured by pulse oximetry, following changes in posture in the dental chair and the administration of Diazemuls (diazepam) in doses sufficient to instill sedation (up to a maximum dose of 20 mg) in the volunteers to a degree such that ptosis was seen. The results indicate that SaO2 values remained above 95 per cent throughout the study. It is concluded that although changes in SaO2 and pulse rate do occur, these differences are not important in healthy individuals, although they may be more serious in patients with pre-existing cardiopulmonary disease.

A nuclear protein is required for thyroid hormone receptor binding to an inhibitory half-site in the epidermal growth factor receptor promoter

The epidermal growth factor (EGF) receptor (EGFR) promoter is negatively regulated by thyroid hormone and retinoic acid. This regulation can be mapped to a 36-basepair GC-rich region of the promoter (EGFR P/E) that functions autonomously as a promoter and an enhancer when placed in front of the thymidine kinase gene TATA element. Direct high affinity binding of the thyroid hormone receptor (T3R) to this element requires a nuclear protein. Through ion exchange chromatography and gel filtration of HeLa nuclear extract, this activity was identified as a protein of approximately 67 kilodaltons. This protein did not bind to DNA alone, but greatly augmented T3R binding to the EGFR P/E sequence in gel mobility shift and DNA precipitation assays. When combined with the T3R auxillary protein (TRAP), the T3R migrated as a larger complex on the DNA. Chemical cross-linking identified this complex as a heterodimer between T3R and TRAP. T3R-TRAP binds to a 7-basepair site in the EGFR P/E (GGGACTC) that has weak homology to a consensus thyroid response element half-site. Thus, on this element, T3R-TRAP heterodimers contact the DNA primarily on a single site that comprises an inhibitory thyroid response element.

Fracture of the mandible in a child

If unusual injuries to the teeth are present, these should serve as a warning to practitioners that further investigations may be necessary. In the case reported here an undisplaced fracture of the jaw in a young child was only revealed by radiographic investigation.

Changes in oxygen saturation using two different sedation techniques

Pulse oximetry was used to assess the degree of hypoxia observed in patients receiving simple midazolam sedation for removal of lower third molars and compared to that seen in patients receiving a combination sedation technique using nalbuphine and midazolam. Results showed that the degree of hypoxia experienced by patients receiving the combination technique was significantly more profound in both incidence and depth than that seen in the group receiving midazolam alone (p less than 0.05).

Structural analysis of the transmembrane domain of the epidermal growth factor receptor

The ligand-binding domain of the epidermal growth factor (EGF) receptor is separated from the cytoplasmic protein tyrosine kinase domain by a predicted single transmembrane segment. Antipeptide antibodies prepared against the outer portion of the predicted transmembrane segment confirmed this area was exposed only when cells were treated with permeabilizing agents. To investigate structural requirements for signal transduction by the transmembrane domain, three types of mutant EGF receptor were prepared. The first type was designed to shorten the transmembrane domain, the second to place proline substitutions within this domain, and the third to make amino acid substitutions analogous to those present in the transforming c-erbB2/neu oncoprotein. Mutant human receptors were expressed in null recipient mouse B82L and Chinese hamster ovary cells. All receptors bound EGF and exhibited EGF-stimulated protein tyrosine kinase activity in vivo as assayed using a 125I-labeled monoclonal anti-phosphotyrosine antibody. EGF stimulated growth of cells expressing each mutant receptor with similar dose-response characteristics. In contrast to other growth factor receptors, the transmembrane domain of the EGF receptor is tolerant to a variety of changes which neither mimic EGF action by constitutive activation nor interfere with ligand-induced signal transduction.

Phosphorylation of the epidermal growth factor receptor at threonine 654 inhibits ligand-induced internalization and down-regulation

To assess the functional significance of phosphorylation of the epidermal growth factor (EGF) receptor at Thr654, we compared the effects of 12-O-tetradecanoyl-13-acetate (TPA) on ligand-induced internalization and down-regulation between wild-type and mutant receptors that contain an alanine substitution at position 654. Activation of protein kinase C with TPA blocked EGF-induced internalization and down-regulation of Thr654 receptors and inhibited in vivo tyrosine kinase activity by 80%. TPA did not inhibit transferrin receptor internalization or constitutive EGF receptor internalization, suggesting that protein kinase C activation inhibits only the ligand-induced process. Inhibition by TPA of induced internalization, down-regulation, and kinase activity required threonine at position 654 since full-length Ala654 EGF receptors were significantly resistant to TPA inhibition of these ligand-induced activities. However, C'-terminal truncation further enhanced this resistance to TPA inhibition. The EGF-dependent internalization of kinase-inactive receptors truncated at residue 1022 was also impaired by TPA in Thr654 receptors, but not in Ala654 receptors, indicating that phosphorylation at Thr654 also interferes with tyrosine kinase-independent receptor activities. We conclude that the dominant regulatory effect of protein kinase C on the EGF receptor is mediated through phosphorylation at Thr654 which effectively inactivates the receptor. The submembrane region of the EGF receptor appears to regulate transmission of conformational information from the extracellular ligand-binding site to the cytoplasmic kinase and regulatory domains.

A comparison of ibuprofen and ibuprofen-codeine combination in the relief of post-operative oral surgery pain

Non-steroidal anti-inflammatory analgesics are commonly prescribed to out-patients who have undergone oral surgical procedures, since they are said to provide excellent pain relief for mild to moderate pain, allied with minimal side-effects. One hundred patients were entered into a randomised clinical trial to compare the efficacy of a simple non-steroidal analgesic with that of a combination analgesic compound following the removal of lower third molars under local anaesthesia. Pain scores were measured for patients post-operatively by means of a verbal rating scale for 3 days and data were analysed using the Mann-Whitney U-test. Results suggest that this combination product offers no advantages (but shows definite disadvantages) when compared to an effective non-steroidal anti-inflammatory product.

Analysis of deletions of the carboxyl terminus of the epidermal growth factor receptor reveals self-phosphorylation at tyrosine 992 and enhanced in vivo tyrosine phosphorylation of cell substrates

The human epidermal growth factor receptor (EGFR) contains a large C' terminus distal to the protein tyrosine kinase domain that is conserved among members of its extended gene family. To investigate the C' terminus, a series of mutant EGFR cDNAs encoding progressive C'-terminal deletions were prepared and expressed in null recipient B82L cells. In vivo self-phosphorylation was retained in receptors truncated to residues 1052 and 1022 which lack the three identified sites of tyrosine self-phosphorylation. Receptors truncated to residue 991 did not undergo in vivo self-phosphorylation. Purified 1022 truncated receptor was self-phosphorylated to the extent of 1 mol of phosphate/mol of receptor protein. The deduced additional site of tyrosine self-phosphorylation at residue 992 was confirmed by tryptic phosphopeptide mapping and protein sequencing. EGFRs deleted to give C'-terminal residues 1052, 1022, 991, and 973 exhibited enhanced EGF-stimulated tyrosine phosphorylation of cell substrates in vivo, whereas deletion at residue 944 abolished all detectable EGF-stimulated protein tyrosine phosphorylation. These results indicate that ligand-induced self-phosphorylation is limited to the C' terminus of the EGFR and suggest that this region of the holoreceptor has an inhibitory function.

Functional independence of the epidermal growth factor receptor from a domain required for ligand-induced internalization and calcium regulation

We have located the distal boundary of the tyrosine kinase domain of the EGF receptor and have identified a distinct sequence in the C' terminus required for EGF-dependent receptor internalization, leading to receptor down-regulation and degradation. Within this receptor domain, an 18 amino acid highly negatively charged region of predicted helical structure is required both for endocytosis via a high-affinity, saturable pathway and for ligand-stimulated increases in cytosolic calcium. In contrast to kinase-inactive, internalization-competent receptors, kinase-active, internalization-defective receptors effectively signaled gene transcription, morphological transformation, and growth. These observations support the hypothesis that mitogenic responses to EGF are mediated by activation of the intrinsic protein tyrosine kinase activity of the membrane-bound receptor, with ligand-induced internalization serving to terminate the signal.

Ligand-induced endocytosis of the EGF receptor is blocked by mutational inactivation and by microinjection of anti-phosphotyrosine antibodies

Early events in ligand-induced endocytosis of the EGF receptor have been examined. A mutant EGF receptor devoid of intrinsic protein-tyrosine kinase activity bound EGF and dimerized normally yet failed to undergo ligand-induced internalization. Immunofluorescence microscopy revealed that receptors lacking kinase activity failed to undergo the ligand-induced internalization characteristic of receptors with kinase activity. Monoclonal anti-phosphotyrosine antibodies effectively inhibited phosphorylation of exogenous substrates in vitro and, when microinjected into cells containing active EGF receptors, prevented internalization of the receptor when cells were subsequently challenged with EGF. These results point to a crucial role for the kinase activity of the EGF receptor in the process of ligand-induced endocytosis of receptors, and imply that a phosphorylated substrate(s) is required.

A three-step purification procedure for protein kinase C: characterization of the purified enzyme

An efficient high yield three-step purification procedure for protein kinase C consisting of ion exchange, hydrophobic interaction, and substrate affinity chromatographies is described. Protein which appears homogeneous on sodium dodecyl sulfate-polyacrylamide gel electrophoresis contains amino acid sequences, predicted from cDNA cloning, for both the alpha and beta isoenzyme forms of the bovine brain enzyme. Both forms appear active as indicated by [3H]phorbol dibutyrate binding stoichiometry of approximately 1. Purified enzyme is active as a monomeric species, exhibits high cooperativity between Ca+2 and phosphatidylserine binding for activity, and undergoes intramolecular self-phosphorylation at both serine and threonine residues. Incubation of the enzyme with ATP, which leads to extensive self-phosphorylation, markedly stabilizes phosphotransferase activity without increasing the Vmax of the reaction.

Phosphorylation of high mobility group protein 14 by casein kinase II

Phosphorylation of chromosomal high mobility group (HMG) protein 14 by casein kinase II has been characterized. Two mol of 32P are incorporated per mol of bovine HMG 14. Kinetic analysis provided evidence for two distinct sites with apparent Km values of 14.5 and 134 microM and respective Vmax values of 0.17 and 0.68 mumol/min/mg casein kinase II. Tryptic peptide mapping identified two phosphorylated products, each with phosphoserine. Amino acid composition and sequence analysis demonstrate that the major high affinity phosphorylation site for casein kinase II is serine 89. This sequence located at the carboxyl-terminal of HMG 14 contains the primary sequence determinants for casein kinase II. On the basis of reverse-phase high performance liquid chromatography and amino acid analysis, HMG 14, serine 99 represents the low affinity phosphorylation site.

Thyrotropin-stimulated phosphorylation of high mobility group protein 14 in vivo at the site catalyzed by cyclic nucleotide-dependent protein kinases in vitro

Thyrotropin (TSH) treatment of bovine thyroid slices increased 32P-labeling of chromosomal high mobility group 14 (HMG) protein approximately 2-fold. Analogs of cAMP, but not cGMP, also enhanced phosphorylation of HMG 14. The sites of phosphorylation were analyzed by partial acid hydrolysis and by two-dimensional mapping of tryptic digests of 32P-labeled HMG 14 which was purified from control and TSH-treated thyroid tissue. TSH treatment enhanced phosphorylation at serine residues in four prominent tryptic phosphopeptides which were identical with those derived from HMG 14 phosphorylated in vitro with cAMP- and cGMP-dependent protein kinases. The four tryptic phosphopeptides contain serine 6, the major site of in vitro phosphorylation catalyzed by cyclic nucleotide-dependent protein kinases (Walton, G. M., Spiess, J., and Gill, G. N. (1982) J. Biol. Chem. 257, 4661-4668). TSH did not affect phosphorylation of serine 24, a minor site of phosphorylation in vitro. These studies suggest that TSH-stimulated phosphorylation of HMG 14 is catalyzed by cAMP-dependent protein kinase.

Identity of the in vivo phosphorylation site in high mobility group 14 protein in HeLa cells with the site phosphorylated by casein kinase II in vitro

The pattern and sites of phosphorylation of high mobility group (HMG) chromosomal proteins in HeLa cells labeled in vivo with [32P]orthophosphate have been compared with those of isolated HeLa HMG protein labeled in vitro by purified protein kinase enzymes. In synchronized HeLa cells there is phosphorylation of two HMG proteins designated hHMG 14 alpha 1 and alpha 2. hHMG 14 alpha 1 and alpha 2 are phosphorylated in a single identical tryptic phosphopeptide which runs toward the anode with electrophoresis at pH 4.7. The specific activity of phosphorylation at this site increased 2.5-fold in both hHMG 14 alpha 1 and alpha 2 in metaphase compared to interphase cultures. In vitro only casein kinase II specifically catalyzed phosphorylation of hHMG 14 alpha 1 and alpha 2 among a mixture of hHMG proteins; phosphorylation occurred at the site which was phosphorylated in vivo. The site of phosphorylation catalyzed by casein kinase II is distinct from sites in HMG proteins phosphorylated by cyclic nucleotide-dependent protein kinases or by casein kinase I. Casein kinase I specifically catalyzed phosphorylation of histone H1. These results indicate that casein kinase II is the enzyme which catalyzes the major phosphorylation of hHMG protein which occurs in vivo.

Phosphorylation of high mobility group 14 protein by cyclic nucleotide-dependent protein kinases

Chromosomal high mobility group (HMG) proteins have been examined as substrates for cGMP-dependent and cAMP-dependent protein kinases. Of the four HMG proteins only HMG 14 contained a major high affinity site which could be phosphorylated by both enzymes, preferentially by cGMP-dependent protein kinase. One mol of 32P was incorporated/mol of HMG 14. Kinetic analysis revealed apparent Km and Vmax of 40.5 microM and 14.7 mumol/min/mg, respectively, for cGMP-dependent protein kinase, and 123 microM and 11.1 mumol/min/mg, respectively, for cAMP-dependent protein kinase. Tryptic maps of 32P-labeled phosphopeptides of HMG 14 demonstrated phosphorylation of the same site by both enzymes. The tryptic fragment containing the major phosphorylation site was identified by amino acid composition and sequence as HMG 14 (residues 4-13): H-Lys-Val-Ser(P)-Ser-Ala-Glu-Gly-Ala-Ala-Lys-OH. HMG 14 and HMG 17 also contained minor sites which could be phosphorylated by cGMP-dependent protein kinase. Tryptic phosphopeptides mapping suggested that the same minor site was phosphorylated on both HMG 14 and 17. On the basis of amino acid composition, the tryptic peptides carrying the minor phosphorylation sites were identified as H-Leu-Ser(P)-Ala-Lys representing residues 23-26 and 27-30 of HMG 14 and HMG 17, respectively.

Comparison of the interaction of cyclic nucleotide-dependent protein kinases with mononucleosomes and free histones

Arginine-rich histones H2A, H2B, H3 and H4 contain two regions of interaction with cyclic nucleotide-dependent protein kinases: a substrate phosphorylation site and a region which noncompetitively inhibits cyclic nucleotide binding to the protein kinases. We have compared the interaction of cyclic nucleotide-dependent protein kinases with these two sites in histones which are organized in nucleosome structures with the interaction of the enzymes with free histones. Whereas histones in solution are readily phosphorylated by cyclic GMP-dependent protein kinase and the catalytic subunit of cyclic AMP-dependent protein kinase, mononucleosomes are not phosphorylated by these enzymes. Histones extracted from mononucleosomes can be phosphorylated, indicating that the lack of phosphorylation of nucleosomes is not due to covalent modification of the histones but to their organization within the nucleosome structure. Whereas histones in solution are effective noncompetitive inhibitors of cyclic GMP binding to cyclic GMP-dependent protein kinase and of cyclic AMP binding to the regulatory subunits of cyclic AMP-dependent protein kinase, mononucleosomes do not affect cyclic nucleotide binding. These studies indicate that histones which are organized in nucleosome structures are neither substrates nor modifiers of cyclic nucleotide-dependent protein kinases.

Regulation of cyclic nucleotide-dependent protein kinase activity by histones and poly(L-arginine)

Interaction of cGMP-dependent protein kinase with histones H2A, H2B, H3, and H4, or poly(L-arginine) resulted in changes in enzyme conformation such that inactivation of cGMP binding and activation of basal catalytic activity (assayed without cGMP) occurred. Total kinase activity as determined by phosphorylation of exogenous substrates subsequently decreased, but autophosphorylation of the enzyme was enhanced. The reaction was specific for nucleosome core histones and poly(L-arginine); H1, troponin, and poly(L-lysine) had no effect. Inactivation of cyclic nucleotide binding sites followed pseudo-first order kinetics and, at various histone concentrations, exhibited saturation kinetics at low ionic strength (2 mM potassium phosphate, pH 6.8), but non-saturation kinetics at higher ionic strength (37.5 mM potassium phosphate, pH 6.8, 12.5 mM MgCl2). Saturation kinetics was observed with poly(L-arginine) at both low and high ionic strength. Kinetic parameters measured under saturation conditions were determined for each core histone and poly(L-arginine). Core histones and poly(L-arginine) were noncompetitive inhibitors of cGMP binding; core histones and poly(L-arginine) interacted competitively at an enzyme site designated as the poly(L-arginine) binding site. Regulatory subunits of cAMP-dependent protein kinase contain a similar poly(L-arginine) binding site. Modulator proteins bind to poly(L-arginine) or arginyl residues in histone to prevent interaction with the poly(L-arginine) binding site on the enzymes. Through this mechanism, modulator proteins maintain cyclic nucleotide dependency and full enzyme activity.

Guanosine 3':5'-monophosphate-dependent protein kinase from bovine lung. Subunit structure and characterization of the purified enzyme

cGMP-dependent protein kinase from bovine lung has been purified to homogeneity using 8-(2-aminoethyl)-amino adenosine 3':5'-monophosphate/Sepharose. Conditions for adsorption of holoenzyme to the affinity chromatography media followed by competitive ligand elution with cGMP have been determined. The holoenzyme of 150,000 molecular weight is composed of two 74,000 molecular weight subunits which are linked in part by disulfide bridges. Two moles of cGMP are bound per mol of holoenzyme compatible with 1 mol of cGMP/monomer. Dissociation of subunits does not occur upon cGMP binding and protein kinase activation. cGMP-dependent protein kinase has an isoelectric point of 5.4 and a Stokes radius of 50 A. The enzyme is asymmetric with an f/f0 of 1.42 and an axial ratio of 7.4. Determination of enzyme activity at varying concentrations of ATP revealed that cGMP increased the Vmax for ATP without significant effect on the Km. The purified enzyme was maximally active at 5 mM Mg2+; other divalent cations could not substitute for Mg2+. In the presence of Mg2+, strong inhibitory effects of other cations were observed with Mn2+, greater than Zn2+, greater than Co2+ greater than Ca2+. Although maximal cGMP-dependence was observed at pH 5.7 to 7.0, basal activity rose at higher pH values to approach activity observed with cGMP. A molecular model comparing cGMP-dependent protein kinase with cAMP-dependnet protein kinase is presented.

Purification and characterization of 3':5'-cyclic GMP-dependent protein kinase

Guanosine 3':5'-cyclic monophosphate (cGMP)-dependent protein kinase has been purified to homogeneity from bovine lung by affinity chromatography and characterized. Partially purified protein kinase, specifically activated by low concentrations of cGMP (22 NM), was adsorbed onto 8-(2-aminoethyl)-amino-adenosine 3':5'-cyclic monophosphate-Sepharose. After washing to remove nonspecific proteins, cGMP-dependent protein kinase was specifically eluted by 0.1 mM cGMP. The purified protein contained cGMP-dependent protein kinase and specific cGMP binding activities. Purification of the holoenzyme was possible because subunit dissociation does not occur upon cyclic nucleotide binding. cGMP-dependent protein kinase holoenzyme has an apparent molecular weight of 150,000 as determined by glycerol density gradient sedimentation. On sodium dodecyl sulfate/polyacrylamide gel electrophoresis, a single protein band of 71,000 molecular weight was observed that suggested the holoenzyme is a dimer composed of subunits of identical molecular weight. cGMP-dependent protein kinase required high concentrations of Mg+2 for optimal activity; a heat-stable protein kinase modulator which inhibited adenosine 3':5'-cyclic monophosphate-dependent protein kinase activity had no effect on the activity of purified cGMP-dependent protein kinase.

The use of affinity chromatography in purification of cyclic nucleotide receptor proteins

Biospecific affinity chromatography has been used to purify specific cyclic AMP and cyclic GMP receptor proteins. Several variables are important for successful purification of the cyclic AMP receptor protein, the most critical being the length of the aliphatic spacer side arm. 8-(2-Aminoethyl)-amino-cyclic AMP coupled to the aliphatic spacer side arm. 8-(2-Aminoethyl)-amino-cyclic AMP coupled to agarose specifically retains the cyclic AMP receptor protein by interaction with the immobilized nucleotide. Binding of the cyclic AMP receptor subunit of cyclic AMP-dependent protein kinase to the immobilized nucleotide results in dissociation of the catalytic protein phosphokinase subunit which is not retained. The retained cyclic AMP receptor protein is subsequently eluted by cyclic AMP. Homogeneous cyclic AMP receptor protein prepared from rabbit skeletal muscle by affinity chromatography has been characterized. The molecular weight of the native protein as determined by analytical ultracentrifugation and polyacrylamide gel electrophoresis at varying acrylamide concentrations is 76 800 and 82 000, respectively. The protein is asymmetric with frictional and axial ratios of 1.64 and 12. SDS and urea polyacrylamide gel electrophoresis indicate that the native cyclic AMP receptor is composed of two identical subunits of 42 700 molecular weight. The native protein dimer binds 2 moles of cyclic AMP per mole of protein and is active in suppressing activity of isolated catalytic subunits of cyclic AMP-dependent protein kinase. Cyclic GMP receptor protein from bovine lung has been purified using the same affinity chromatography media. Since cyclic nucleotide binding to cyclic GMP-dependent protein kinase does not result in dissociation of regulatory receptor and catalytic phosphotransferase subunits, the cyclic GMP-dependent protein kinase holoenzyme is retained on the column and can be subsequently specifically eluted with cyclic GMP.

Preferential regulation of protein synthesis initiation complex formation by purine nucleotides

A comparison of the affinities of eukaryotic initiation factor 2 and eukaryotic elongation factor 1 for GTP and GDP, and of the responses of initiation and elongation complex formation to various GTP mol fractions indicated that the initiation reaction was more sensitive to changes in the GTP: GDP ratio. In vitro regulation of the GTP: GDP ratio by the adenylate energy charge, a sensitive control parameter, also demonstrated a preference for regulation of formation of initiation complexes when compared to elongation complexes. These studies suggest that, based on the availability of energy, initiation is the rate-limiting step in the overall protein synthetic process.

Regulation of ternary (Met-tRNAf - GTP - eukaryotic initiation factor 2) protein synthesis initiation complex formation by the adenylate energy charge

Formation of the ternary [Met-tRNAf - GTP - eukaryotic initiation factor 2] protein synthesis initiation complex in rabbit reticulocyte ribosomal eluates is dependent on the GTP: GDP ratio and on the adenylate energy charge. The elements controlling ternary initiation complex formation have been studied in a reconstituted system contianing eukaryotic initiation factor 2 and nucleoside diphosphate kinase purified from the ribosomal eluate. The concentration of GTP required for half maximal formation of the ternary initiation complex is 2.5 - 10(6) M; GDP is a potent competitive inhibitor with Ki equals 3.4 - 10(7) M. Sensitive control of ternary initiation complex formation by the adenylate energy charge occurs through nucleoside diphosphate kinase regulation of the GTP : GDP ratio. Over a wide range of GTP : GDP ratios, 50% of maximal ternary initiation complex formation is observed at an adenylate energy charge of 0.85-0.90 resembling that seen in the unfractionated system. Small changes in adenylate energy charge near this value result in significant changes in the extent of ternary initiation complex formation. Since GTP is continually hydrolyzed to GDP during protein synthesis and since GDP is a competitive inhibitor of GTP binding to several of the protein factors necessary for mRNA translation, the synthetic process provides sensitive control by product inhibition. Ribosome-associated nucleoside diphosphate kinase control of GTP regeneration in response to the adenylate energy charge provides one mechanism for linking protein synthesis to the nutrient state and energy charge of the cell.

Nucleotide regulation of a eukaryotic protein synthesis initiation complex;

Formation of a ternary initiation complex containing Met-tRNAf, GTP and eukaryotic initiation factor 2, is the first step in sequential assembly of the initiation complex. The concentration of GTP required for half maximal formation of the ternary complex is 2.5 with 10(-6) M. GDP is a potent competitive inhibitor of ternary complex formation with Ki = 3.4 with 10(-7) M. The nucleotide binding site on eukaryotic initiation factor 2 demonstrates relative specificity for GDP with KD(GDP) = 3.0 with 10(-8) M; 100-fold higher concentrations of GTP than GDP are required for displacement of either [(3)H]GDP or [(3)h]gtp from the necleotide binding site. An ATP-dependent stimulation of ternary complex formation observed in partially purified initiation factor preparations is due to nucleoside diphosphate kinase (EC 2.7.4.6) which serves to remove inhibitory levels of GDP by phosphorylation with ATP. Since GTP is hydrolyzed to GDP during protein synthesis, this provides a mechanism by which the ATP:ADP ratio may regulate the rate of initiation of protein synthesis.