Chemical cross-linking and mass spectrometry to determine the subunit interaction network in a recombinant human SAGA HAT subcomplex

Understanding the way how proteins interact with each other to form transient or stable protein complexes is a key aspect in structural biology. In this study, we combined chemical cross-linking with mass spectrometry to determine the binding stoichiometry and map the protein-protein interaction network of a human SAGA HAT subcomplex. MALDI-MS equipped with high mass detection was used to follow the cross-linking reaction using bis[sulfosuccinimidyl] suberate (BS3) and confirm the heterotetrameric stoichiometry of the specific stabilized subcomplex. Cross-linking with isotopically labeled BS3 d0-d4 followed by trypsin digestion allowed the identification of intra- and intercross-linked peptides using two dedicated search engines: pLink and xQuest. The identified interlinked peptides suggest a strong network of interaction between GCN5, ADA2B and ADA3 subunits; SGF29 is interacting with GCN5 and ADA3 but not with ADA2B. These restraint data were combined to molecular modeling and a low-resolution interacting model for the human SAGA HAT subcomplex could be proposed, illustrating the potential of an integrative strategy using cross-linking and mass spectrometry for addressing the structural architecture of multiprotein complexes.

[Aortitis after G-CSF injections]

INTRODUCTION

Aortitis consists in aortic wall inflammation from infectious or non infectious cause. It may lead to aortic aneurysm with a risk of rupture, which is life-threatening and may justify surgical procedures. The cause of the aortitis is sometimes obscure.

CASE REPORT

We report the case of a 55 years old woman who developed acute aortitis of the descending aorta after G-CSF (granulocyte-colony stimulating factor) injections for blood stem cells graft. No cause was found to the aortitis, the evolution was favorable after corticosteroid treatment, without aneurysm at six months.

CONCLUSION

The present case rises the question of G-CSF (Neupogen responsibility in aortic lesions. Neutrophilic mediated diseases (Sweet's syndrome, pyoderma gangrenosum) and leukocytoclastic vasculitis were reported after G-CSF therapy. Neutrophils induced by G-CSF injections present functional abnormalities which may play a role in the pathogenesis of these diseases.

[Subacute infectious endocarditis due to the agent of cat scratch fever: Bartonella henselae]

The diagnosis of severe mitral stenosis with left atrial thrombus was rectified at valvular replacement in a 48-year old immuno-competent man who was a cat owner. The mass in the left atrium was, in fact, a large endocarditic vegetation. Pre- and postoperative blood cultures were negative as was culture of the excised mitral valve. The diagnosis of infectious endocarditis (IE) due to Bartonella Henselae was made from a positive serological test (1600) and identification of the germ by genetic amplification. Antibiotic therapy was continued for 6 months and the patient was cured with a follow-up of 4 years. Bartonella Henselae IE is very rare (14 reported cases) and affects mainly the aortic valve, often giving rise to very large vegetations which, in half the cases, are complicated by systemic emboli. Germs like Batonella are sensitive to most antibiotics, especially the aminosides and macrolides. In Bartonella Henselae IE, valve replacement is the rule (13 out of 14 cases) and the prognosis is usually good. Sero-diagnosis of Bartonellosis should be part of the systematic investigation of all blood culture negative IE.

[Communication between the left ventricle and the right atrium in infectious endocarditis. Diagnosis using Doppler-echocardiography]

The diagnosis of a communication between the left ventricle and right atrium was made by transthoracic and transoesophageal echocardiography in a 67 year old man with a recurrence of a methicillin-resistant staphylococcus aureus infectious endocarditis complicating aortic valve replacement with a bioprosthesis seven weeks previously. This diagnosis was confirmed at surgery; the left ventricular-right atrial communication was closed by suturing its edges and a new aortic valve prosthesis was implanted. Unfortunately, the patient died 4 months later of myocardial dysfunction although the infectious endocarditis seemed to have been sterilised by antibiotic therapy. Doppler echocardiography, especially using the transoesophageal approach is the best diagnostic method for rare complications of infectious endocarditis, usually of the aortic valve, the prognosis of which is improved by early surgery and appropriate antibiotic therapy for the causal organisms.

[Myocardial infarction in the elderly. Comparison between 2 groups of patients over 75 and under 65 years of age]

To define the clinical characteristics, prognosis and treatment of myocardial infarction (MI) in the elderly, we retrospectively compared the files of 101 patients aged > or = 75 years (mean: 82 +/- 4 years) and of 120 others aged < or = 65 years (mean: 55 +/- 4.7 years). The figures corresponding to younger patients are presented in brackets. The elderly group included 60.4% women (5%: p < 0.001), 58.9% hypertensive subjects (38.3%: p = 0.005); 30.4% diabetics (11.7%: p = 0.0013) and 12.6% smokers (66.1%: p < 0.001); 20.8% of the elderly had a history of MI (10%: p = 0.002), 15.8% of arteriopathy of the lower limbs (8.3%: p = 0.001) and 6.9% of cerebrovascular accident (1.7%: p = 0.02). Elderly patients were admitted after an average of 26.6 hours (10.4 hours: p < 0.001). Only 56.4% (79.2%) reported typical MI pain, 22.8% (7.5%) had a painless form, 31.8% (4.2%) an initial left ventricular failure, 21.8% (7.5%) a global cardiac dysfunction and 20.8% (4.2%) a cardiogenic shock (p < 0.001 for all comparisons). 63.4% had an anterior MI (40.8%: p < 0.001), 40.6% a Q-form (29.6%: p = NS) and 22.2% an atrial fibrillation (0.8%: p < 0.001). Serum myoglobin and total CK concentrations were significantly lower in elderly subjects. 20.8% of them received beta-blockers (86.7%), 43.6% aspirin (80%), 14.6% oral anticoagulant (56.7%), but 63.4% were given diuretics (25.2%) and 31.7% digitalis alkaloids and positive inotropic drugs (6.7%) (p < 0.001 for all these comparisons). Heparin, nitrates, calcium channel blockers, ACE inhibitors and antiarrhythmics were prescribed as often regardless of age. Only 10 elderly patients (9.9%) were treated with thrombolytics (77: 65%: p < 0.001); 6 (5.9%) underwent coronary angiography (43: 35.8%: p < 0.001), 2 (2%) angioplasty (11: 9.2%) and one (1%) coronary bypass surgery (12: 10%). 35 elderly patients (34.7%) died while in hospital (5: 4.2%), 22 suddenly, 10 in cardiogenic shock and 3 due to arrhythmias. 38 cases (37.8%) of heart failure (21: 17.5%), 21 (20.8%) recurrences of coronary insufficiency (8: 6.7%) and 11 (10.9%) mechanical complications of MI (4: 3.3%) were also observed (p < 0.001 for all these comparisons). Due to lack of sufficient data, we could not define the status of the surviving patients discharged from hospital. The wider use of thrombolytics, angiography and angioplasty (coronary bypass surgery still having a heavy mortality and morbidity) is probably the best way to improve the prognosis of MI in the elderly.

[Value of mass dosage of the MB isoenzyme of creatinine phosphokinase in the diagnosis of recent myocardial infarction]

In 391 patients admitted 3.7 hours (h) (median) after experiencing infarct-like pain, kinetic monitoring of CK-MB "mass" (threshold: 7 micrograms/l), myoglobin (threshold: 90 micrograms/l) and total CK (threshold: 290 micrograms/l) was carried out at the time of admission and after 1.5, 3, 6, 9, 12, 24 and 48 h. When myocardial infarction (MI) was treated conventionally (102 patients). CK-MB peaked 11 h (median) after the onset of pain, later than myoglobin (9 h), but before total CK (12 h). The peak of the markers was higher in Q+ than in Q-MI (p < 0.05). When MI was treated by thrombolytic medications (44 patients), the increases in CK-MB, myoglobin and total CK were larger, and occurred sooner (peaks 9, 6 and 6 h, after the onset of pain respectively), but did not last as long. In 245 patients who had not had MI (including 123 with spontaneous angina), the levels of the three markers remained stable and well below the decision thresholds. The sensitivities of CK-MB, myoglobin and total CK were respectively 47.1, 51.8 and 34.8% at the time of admission, 67.3, 82.7 and 57.1% after 3 h and 83.1, 76.9 and 88.9% after 6 h. The combined determination of CK-MB and of myoglobin had a higher sensitivity (67.7% at the time of admission, 84.9% after 1.5% and 88.2% after 3 h: but most of this gain was due to myoglobin. The specificity of the three markers and their diagnostic accuracy are comparable. In the course of recent MI, the kinetics of CK-MB mass are thus slower than those of myoglobin, but a little faster than those of total CK. The choice of the most effective biochemical marker depends upon the interval between onset of chest pain and hospitalization of the patient. Repetition of the determinations improves the diagnostic situation.

[Ilio-femoral vein thrombosis treated with tissue plasminogen activator in a pregnant woman]

A 27-year-old woman, after 31 weeks of amenorrhoea during her second pregnancy, developed a left external iliac and femoral deep vein thrombosis, confirmed by venous ultrasonography and magnetic resonance imaging. The infusion of tissue plasminogen activator (rt-PA: 1.2 mg/kg, i.e. 80 mg over 3 hours), on the 2nd day, allowed revascularization of the femoral junction, while the external iliac vein remained occluded. The patient did not develop pulmonary embolism or haemorrhage, particularly obstetric haemorrhage. The subsequent pregnancy was uneventful until delivery, six weeks later, of a normal child. Three years later, the patient has no sequelae of her deep vein thrombosis. When required by the patient's condition, it seems that rt-PA can be used to treat severe deep vein thrombosis during pregnancy, either isolated or complicated by pulmonary embolism. Very rigorous cardiological, obstetric and laboratory surveillance is essential. A sufficient dosage, identical to that used in clinical settings other than pregnancy and a brief treatment duration (2 to 3 hours) are probably more effective and more reliable than lower doses continued for several days. However, the risk of haemorrhage remains difficult to predict and its prognosis, especially foetal, is often very poor. A larger series of cases is therefore necessary before this drug can unreservedly recommended in pregnant women.

[Cerebral embolism disclosing a left intraventricular thrombus 6 years after atypical infarction]

The authors report a case which is unusual because of the late presentation, as a cerebral embolism, of a left intraventricular thrombus six years after an infarction. This thrombus was absent at the acute stage of the infarction. The conditions surrounding the development of a thrombus after an infarction are reviewed. This is a common complication at the acute stage of an anterior infarction, notably when there is apical akinesia. The late onset of these thrombi has not been extensively studied in the literature. This would appear to be a fairly rare event but which, as shown by our case, pleads in favour of very prolonged anticoagulant treatment after certain myocardial infarctions.

[Effect of tobacco smoking on the incidence of recurrent myocardial infarction. A retrospective study of 208 cases]

Two hundred and eight patients, less than 60 years of age at the time of their first myocardial infarction (MI), which occurred between 1 July 1976 and 30 September 1982, and with a mean recurrence-free follow-up period of 3450 +/- 142 days, were included in a retrospective survey. This concerned the outcome of their coronary artery disease and the persistence of vascular risk factors, notably their tobacco consumption, the extent and forme of which was detailed. This study showed: 1) the mortality rate was 8.8%, 2) 78.4% of the patients smoked before their infarction, 3) 76% of the smokers stopped smoking after this event. The risk of recurrence of infarction was higher amongst smokers. After 5 years, 51.6 +/- 15% of the subjects who had not reduced their daily tobacco consumption had suffered another MI, versus 21.5 +/- 3% of those who had reduced it by 1 to 50%, 16.9 +/- 6% of those who had never smoked and only 10.5 +/- 6% of those who had reduced it by more than 50% or had stopped smoking (p less than 0.02). The relative risk of recurrence of infarction in persistent smokers was 4.4 times that in subjects who had stopped smoking. However, no significant difference was found between the mortality in the various subgroups. In addition to smoking, only two factors were found to significantly promote the onset of a fresh MI: an initial infarction with no Q wave (p = 0.007), and the persistence of spontaneous angina pectoris (p = 0.0009).

[Vasospastic angina with angiographically normal coronary vessels of iatrogenic origin. Apropos of 2 cases]

Two cases of angina pectoris, induced by methylergometrine (Methergin) and by an association of ergotamine tartrate (Gynergene) and methysergide (Desernil) respectively, are reported. In both patients, angiography revealed spontaneous spasm in a coronary system free from any significant atheromatous stenosis. In the second case, a test administration of i.v. Methergin, administered during calcium-channel antagonist treatment a few days after the "guilty" drugs had been stopped was found to be negative. The outcome was favorable in both cases: the angina disappeared and the base-line and exercise ECG returned to normal. The hypothesis of coronary spasm induced by the treatment was adopted in both cases. In this context, the major iatrogenic etiologies of vasospastic angina are recalled, together with the prophylactic and therapeutic measures they call for.

[Coronary insufficiency caused by atherosclerosis. Current pathogenic concepts, clinical, angio-anatomic correlations and therapeutic deductions]

The multiplicity of clinical expressions of coronary artery failure results from the interaction between three processes which varies from one patient to another and from one time to another in a given patient. The three processes involved are: atheromatous coronary stenosis, arterial spasm and the development of a fibrino-thrombocytic thrombus. In stable angina pectoris, atheromatous narrowing, with smooth, regular outlines, no endothelial injury and little likelihood of complication by thrombosis predominates. In contrast, labile angina and myocardial infarction give rise to the same lesions: usually irregular stenoses, with a narrow neck and irregular outline. They correspond histologically to the rupture of an atheroma plaque, frequently complicated by the appearance in situ of a clot. In the authors' experience, complete arterial occlusion ensues in three out of four cases. The rate at which aggravation progresses and the variable degree of collateral circulation explains why a whole range of intermediate clinical expressions are possible, ranging from labile angina to sudden death of ischemic origin, and including various forms of infarction (both with and without the Q wave). Healing of these lesions may also be observed, usually resulting in progression of the coronary stenosis and sometimes of modification of left ventricular function of variable duration (myocardial stunning or hibernation). The importance of thrombotic phenomena in triggering the most serious forms of coronary artery failure (labile angina and myocardial infarction) provides a more precise identification of the place of thrombolytic treatment. In addition, it appears that there is no point in emergency revascularization of the ischemic myocardium. However, despite recent clinical progress, coronary artery disease remains a worrying illness which calls for primary prevention measures. Such measures must be undertaken as soon as possible if they are to be effective.

[Value of the assay of serum myoglobin in recent myocardial infarction]

The serum myoglobin (MG) was assayed by the radio-immunological method in 30 patients, all victims of a recent myocardial infarction (MI) and in 30 tests subjects suffering (21 cases) or not (9 cases) from heart diseases, but none from myocardial infarction (MI). The blood samples have been collected on hospital admission of the patient, then every four hours during the first 48 hours and finally, every 12 hours from the 48th to 72nd hour. The normal value is less than 85 micrograms/l. The creatine-kinase (CK), the aspartate aminotransferase (ASAT), the alanine aminotransferase (ALAT) and the lactate dehydrogenase (LDH) were also assayed each time. In MI, there is a significant increase in the serum MG level (731 +/- 323 micrograms/l against 174 +/- 198 micrograms/l in the test subjects; p less than 0.001). The sensitivity of this assay reaches 97%, its specificity 80%, its positive predictive value 83% and its negative predictive value 96%. Starting from the beginning of the characteristic pain of infarction, the MG level exceeds the normal values after 3.3 +/- 1.6 hours, reaches its maximum after 9.3 +/- 3.7 hours and comes back to normal after 38 +/- 8.1 hours. On the other hand, the MG level does not enable any conclusion regarding either the transmural/not transmural nature, or the site, or the acuteness of the MI.(ABSTRACT TRUNCATED AT 250 WORDS)

[Value of echocardiography in aged patients with presumed idiopathic auricular fibrillation]

Thirty seven patients (mean age = 80.2 years with extremes from 66 to 98 years), presenting atrial fibrillation (AF), presumably idiopathic (non known heart disease, completely normal cardiac auscultation, good quality chest X-ray and electrocardiogram, no laboratory test anomaly), and paroxystic (n = 7: 19 p. cent) or permanent (n = 30: 81 p. cent), were given an electrocardiogram TM and bidimensional. In only 9 of them (24.3 p. cent), this examination is completely normal. Three other patients (8.1 p. cent) present an isolated dilatation of the left atrium. The 25 remaining patients present various cardiopericardic anomalies: valvular pathologies (n = 2: 59.4 p. cent): mitral (n = 15: 40.5 p. cent) more often than aortic (n = 7: 18.9 p. cent); myocardiopathies (n = 8: 21.6 p. cent), hypertrophic (n = 2), dilated (n = 4) or hypertrophic and dilated (n = 2); moderate pericardial effusion (n = 1: 2.7 p. cent). The mean left and right ventricular diameters, measured in TM mode, are normal as well as the mean contractility indexes (percentage of shortening of the small axis, stroke volume) and the mean filling index (mitral gradient EF) of the LV. Overall, the transverse diameter of the LA is moderately increased (41.9 +/- 9.7 mm); it is not significantly different from the AF, either paroxystic (41.5 +/- 4.9 mm) or permanent (42 +/- 9.93 mm) and whether it is (40.5 +/- 9.9 mm =) or not (42.5 +/- 8.8 mm) complicated by a systemic embolism, especially cerebral. Therefore, the sonocardiogram demonstrates a latent cardiopathy in two-thirds of the patients over 65 presenting a presumably idiopathic AF.(ABSTRACT TRUNCATED AT 250 WORDS)

[Angiographic morphology of the coronary arteries after a recent myocardial infarction treated by intravenous thrombolysis]

Thirty patients (26 men, 4 women) aged from 32 to 73 years (mean 54 years) who developed anterior (14 cases) or posterior (16 cases) myocardial infarction received intravenous streptokinase in doses of 1,500,000 units 2 to 10 hours (mean 4 hours) after the onset of infarction. Coronary angiography, performed 18.6 days on average after thrombolysis, showed a distinct predominance of asymmetrical stenosis with irregular walls and a narrow neck (10 cases, 33 p. 100) or of complete occlusion (12 cases, 40 p. 100) in the artery responsible for the infarction. Complete occlusion probably was the ultimate stage of stenosis. In contrast, the various angiographic images observed in arteries unrelated to the infarction were evenly distributed. The radiological morphology of coronary arterial lesions after a recent infarction is suggestive of ruptured atheromatous plaque, sometimes complicated by thrombosis in situ. Identical images are seen in unstable angina. These findings indicate that one single therapeutic approach should be applied to the most severe types of coronary disease due to atherosclerosis.