Endovascular Treatment of Intracranial Aneurysms: Long-Term Follow-up

Endovascular treatment of intracranial aneurysms is increasingly used and has evolved as an alternative to surgical clipping. However, its long-term efficacy has yet to be established. This retrospective hospital based (tertiary teaching hospital) study aimed to identify factors that might be important in predicting initial efficacy of this treatment and a long-term follow-up to study the clinical and angiographic results of treated aneurysms. A total of 80 aneurysms in 78 patients were treated and analyzed, and the percentage of occlusion calculated. Overall, 51/80 (64 %) cases were treated with selective endovascular coil occlusion and 29/80 (36 %) by parent artery occlusion. The shape of the aneurysm rest was noted on the immediate post treatment and follow-up angiograms. Immediate and follow-up clinical status was also noted using the Glasgow outcome scale. The clinical and radiological changes on follow-up were assessed and possible factors involved were analyzed. Of the 50 patients of intracranial aneurysms that underwent selective aneurysm coiling, good immediate outcome (Glasgow outcome scale 1 and 2) was seen in 36/50 (72 %) cases. Narrow necked aneurysms showed a good immediate result (90–100 % packing) in all cases 28/28 (100 %). Amongst the wide necked aneurysms, good packing (90–100 %) was achieved in 17/23 (73 %) cases. Amongst the cases treated with parent artery occlusion, complete occlusion was noted in 20/29 (69 %) cases. No subarachnoid hemorrhage was seen in any of the followed up cases of coiled aneurysms. A statistically significant relationship was noted between aneurysm neck size and immediate angiographic outcome. Long-term angiographic recurrences were found more often in large aneurysms. Endovascular treatment of intracranial aneurysms is a safe and effective treatment modality that offers protection from recurrent subarachnoid hemorrhage.

‘Torch Fire Sign’: A New MR Sign in Profound Hypoxic Ischemic Brain Injury in a Term Infant

Hypoxic-ischemic injury can produce diverse patterns of brain damage detected on MR imaging which mainly depend on the severity of brain ischemia and the maturity of the brain at the time of insult1. In a term infant severe ischemia produces maximum damage in the lateral thalami, posteromedial putamen, hippocampi and the dorsal brain stem in addition to the perirolandic cortex2. This is because these areas are the most metabolically active sites in the neonate3.

Acute subdural effusion in vasculitis

We report a 29-year-old man with a unique presentation of vasculitis as acute unilateral subdural effusion and meningoencephalitis. Magnetic resonance imaging showed a brainstem lesion that spread to the thalamus over time. There were no systemic features of vasculitis other than a positive pathergy test. Histopathological examination from the pathergy site showed neutrophilic infiltrate and leucocytoclastic vasculitis. The condition was steroid responsive and he remained in remission at two years' follow-up. The anatomy of the brainstem lesion, absence of other inflammatory and infective conditions on evaluation suggests a vasculitic pathology either as primary central nervous system angiitis or as neurological presentation of systemic vasculitis like Behetaet's disease although the international diagnostic criteria for Behetaet's were not fulfilled.

Fluoroscopic-guided balloon dilatation and stenting in tracheal stenosis with metallic self-expandable stents and long-term follow-up results

The purpose of this study was to assess the safety and long-term efficacy of self-expandable stents in the treatment of benign tracheal stenosis. Nine patients (seven men) with tracheal stenosis (including one with fistula) of varied cause were treated by fluoroscopically guided balloon dilatation and stenting with self-expandable metallic stents. The procedure was carried out under topical spray in eight patients and under general anaesthesia in one patient. The patients were followed up for a period ranging between 13 and 60 months. In eight of the nine patients, satisfactory positioning of the stent was achieved at the first instance, with immediate relief of dyspnoea. One patient with innominate artery aneurysm died 16 days after the procedure because of renal failure. At 1 month of follow up, six out of eight (75%) of our live patients were without any respiratory embarrassment. This dyspnoea-free result reached almost 90% by the end of 1 year especially so in the fibrous strictures. Four out of the eight live patients (50%) had cough for 2 months and two (25%) had mild blood-tinged sputum treated by inhalation and mucolytic agents. Secondary intervention was required in one patient at 1 month because of recurrent symptoms. The patient with tracheo-oesophageal fistula required surgical intervention because of fracture of the stent. Fluoroscopically guided balloon dilatation and stenting of the tracheal stenosis is an effective non-surgical therapy resulting in cure of fibrous strictures and palliation in cases of malignancy.

Spinal angiolipoma with acute subarachnoid hemorrhage

Angiolipoma is a rare tumor of the spine commonly presenting with compressive myelopathy. We report a spinal angiolipoma in a 14-year-old patient with acute spinal subarachnoid hemorrhage (SAH). To our knowledge this is the first reported case of a spinal angiolipoma presenting with SAH, associated with post-subclavian coarctation with diffuse hypoplasia of the descending aorta. This association of coarctation of aorta, aortic hypoplasia and spinal angiolipoma has also not been reported previously.

Stroke from delayed embolization of polymerized glue following percutaneous direct injection of a carotid body tumor

A 52-year-old male with right carotid body tumor underwent direct percutaneous glue (n-butylcyanoacrylate [NBCA]) embolization. Several hours later, he developed left hemiparesis from embolization of the polymerized glue cast. Migration of glue during percutaneous tumor embolization is presumed to occur only in the liquid state, which may lead to stroke or cranial nerve deficits. To the best of our knowledge, this is the first report of delayed glue embolization from a treated hypervascular tumor of the head and neck.

Advanced MR imaging in Lhermitte-Duclos disease: moving closer to pathology and pathophysiology

INTRODUCTION

Lhermitte-Duclos disease (LDD, dysplastic gangliocytoma) is an extremely rare cerebellar lesion of uncertain etiology. The debate as to whether it constitutes a neoplastic, malformative, or hamartomatous lesion is still continuing. In this report we explore the usefulness of susceptibility-weighted imaging (SWI), diffusion weighted imaging (DWI), perfusion imaging, and chemical shift imaging (CSI) in demonstrating the pathology and pathophysiology in two patients with LDD.

METHODS

MR imaging of the brain and the cervicodorsal spine was performed on a 1.5-T scanner in a 47-year-old woman presenting with numbness and paresthesia of both upper and lower limbs, and in a 17-year-old male with right frontal headache associated with neck pain.

RESULTS

Routine imaging in the first patient showed a left-side cerebellar mass with characteristic 'tiger-striped' thick folia associated with Chiari I malformation, tonsillar herniation and cervicodorsal syringomyelia and in the second patient a right cerebellar mass with similar findings. The SWI demonstrated the characteristic deep running veins between the folia, which is thought to be the cause for vascular contrast enhancement. Diffusion showed a T2 shine-through effect with mild increased diffusivity, and perfusion showed increase in relative cerebral blood volume, relative cerebral blood flow, and mean transit time in the lesion. MR spectroscopy demonstrated reduction in metabolites and a prominent lactate peak in both the patients. The pathological and pathophysiological significance of these findings is discussed.

CONCLUSION

MRI with the newer imaging capabilities can demonstrate the pathology and pathophysiology in Lhermitte-Duclos disease better. SWI helps in detecting the veins around the thickened folia.

Disseminated necrotizing leukoencephalopathy following low-dose oral methotrexate

Leukoencephalopathy is a recognized complication with intrathecal or intravenous methotrexate (MTX). We report a 59-year-old lady who developed MTX leukoencephalopathy with long-term low-dose oral MTX. She developed posterior leukoencephalopathy (PLE) that initially was reversible on discontinuation of oral MTX. Four months later, she developed disseminated necrotizing leukoencephalopathy (DNL), and was left with devastating neurological deficits. The sequential conventional magnetic resonance imaging (MRI), diffusion weighted imaging (DWI), MR perfusion (MRP) and MR spectroscopic (MRS) changes are highlighted in this report. MRP and MRS showed more wide spread abnormalities than DWI. Stereotactic biopsy from the lesion revealed demyelination with macrophagic infiltration, pericapillary lymphomononuclear aggregation, fibrinoid changes in the capillaries and neovascularization. Of the two cases of PLE with oral MTX reported in literature, one reversed clinically and radiologically with the discontinuation of MTX. To the best of our knowledge, this is the first reported case of DNL following oral MTX in the world literature.

Alanine peak in central neurocytomas on proton MR spectroscopy

INTRODUCTION

We present three consecutive patients with central neurocytoma in whom proton MRS demonstrated the presence of alanine.

MATERIALS AND METHODS

Three patients in the age range 24 to 30 years underwent MRI and proton MRS using a 1.5-T system. MRS was performed with the multivoxel PRESS sequence. All three patients underwent surgery and the diagnosis of central neurocytoma was established by histopathological examination and immunostaining.

RESULTS

With an echo time of 135 ms glycine, high choline, small NAA and alanine were observed in all three patients.

CONCLUSION

Alanine may be observed in central neurocytomas as it is in meningiomas. Other spectral peaks such as those for glycine and NAA should help to identify this tumor correctly.

Reversible periictal MRI abnormalities: Clinical correlates and long-term outcome in 12 patients

Although a wide spectrum of reversible periictal magnetic resonance imaging (MRI) abnormalities (RPMA) are being increasingly identified, the clinicians are often in a dilemma about their localization significance. This prompted us to analyze the clinical, MRI, electroencephalographic (EEG) and follow-up data of 12 patients with RPMA seen in a tertiary referral epilepsy center. RPMA occurred after a single or a cluster of focal seizures with or without secondary generalization. The interictal and ictal EEG abnormalities were localized to the site of RPMA in nine patients. RPMA involved areas remote from the site of EEG abnormalities in four patients. We have developed a comprehensive classification to account for the wide spectrum of RPMA involving gray matter, white matter and leptomeninges with or without contrast enhancement or mass effect. Follow-up MRIs showed complete resolution of RPMA in all, except in four patients, who developed residual focal atrophy. During median follow-up period of 3 years, recurrence of RPMA was observed in two patients. Diffusion weighted MRI in two patients and histopathological finding in one patient favored causal role of hypoxia in the pathogenesis of RPMA. Our observations help to understand the electroclinical profile, radiological spectrum, localization significance and natural history of RPMA better.

Endovascular treatment of ruptured posterior circulation dissecting aneurysms

BACKGROUND

and aim: Dissecting aneurysms of the posterior circulation constitute a relatively uncommon subgroup of aneurysms. They account for 3-7% of cases of nontraumatic subarachnoid hemorrhage. Because of high risk, in most cases the patients require surgical or endovascular therapy. In this study we discuss the clinical efficacy of endovascular treatment with long-term follow-up in ruptured dissecting aneurysms of the posterior circulation.

MATERIALS AND METHODS

This retrospective study was conducted at our institution between January 1995 and June 2005. Eight patients (4 male; 4 females) ranging in age from 24 to 65 years (mean, 46.75 years), were included. All presented with SAH. Endovascular treatment was based on the configuration of the dissecting aneurysm. Attempt was made to occlude the dissecting aneurysm.

RESULT

A total of 8 ruptured dissecting aneurysms in the posterior circulation were treated. Out of them 5 were in the intradural vertebral artery, 2 in the basilar trunk and one in the proximal PCA. All the cases were technically successful. We have seen only two complications. The pre and post procedure (at the time of discharge) mean modified Rankin scores in the patients were 4.6 (SD 0.51) and 1.7 (SD 1.98). This improvement in Rankin score after endovascular treatment was statistically significant (Wilcoxon signed rank test, P=.017).

CONCLUSION

Endovascular management of these lesions is safe and effective mode of treatment and gives adequate protection from rebleed.

Anomalous origin of the callosomarginal artery from the A1 segment with an associated saccular aneurysm

Although anatomic variations are well known in the A1 segment of the anterior cerebral artery (ACA), anomalous origin of a cortical artery from the A1 segment is extremely rare. The only reported cortical branch to arise from the A1 segment is the fronto-orbital artery. We report a case of anomalous origin of the callosomarginal artery (CMA) in association with a saccular aneurysm from the A1 segment of the left ACA in a 35-year-old man who presented with intracerebral hemorrhage. To our knowledge, this is the first report of anomalous origin of the CMA from the A1 segment.

Variant origin of superior thyroid artery, occipital artery and ascending pharyngeal artery from a common trunk from the cervical segment of internal carotid artery

We report a case of variant origin of superior thyroid artery (STA), occipital artery (OA) and ascending pharyngeal artery (APA) from the cervical segment of internal carotid artery (ICA) in a 63-year-old male patient, who presented with acute subarachnoid hemorrhage. Four-vessel angiography showed asymptomatic occlusion of ICA giving origin to the anomalous branches. There was common origin of the STA and the OA. The APA originated from the OA. We did not find any other description in the literature on variant origin of STA from the cervical segment of ICA in the presence of a well-developed external carotid artery.

Endovascular treatment of direct carotid cavernous fistulae: a pictorial review

INTRODUCTION

Direct carotid-cavernous fistulae (CCFs) are type A fistulae according to Barrow's classification. Endovascular treatment of these lesions is challenging.

METHODS

The purpose of this review was to evaluate the endovascular treatment of direct CCFs. We also describe the technique, symptomatology and complications associated with the procedure and report on the long-term follow-up in our treated patients.

RESULTS

A total of 89 patients with a direct CCF were treated. All patients had baseline brain CT or MR imaging. Treatment comprised transarterial balloon or coil embolizations. The patients were followed up at 1 month and then every 6 months thereafter. Detachable balloons were used in 79 fistulae. In 12 fistulae the balloon could not be negotiated through the fistula and these fistulae were treated with transarterial coil occlusion. Clinical outcomes of the treated patients evaluated at 1 month were: 79 patients (88.8%) cured, 9 (10.1%) significantly improved, 1 (1.1%) remaining static.

CONCLUSION

Endovascular treatment of direct CCFs is safe and effective and results in long-term cure.

Evaluation, management, and long-term follow up of vein of Galen malformations

OBJECT

Vein of Galen malformations (VGMs) are extremely rare intracranial lesions. Clinical presentation and management strategies vary significantly in different areas of the world. The authors report their experience in evaluation, management, and long-term follow up of these lesions in India.

METHODS

Between October 1983 and June 2003, 25 patients with VGMs were referred to the authors' institution for evaluation and management. Ten children younger than 2 years of age presented with rapidly increasing head size as the chief complaint. Among 11 children 2 years of age or older, the most common presenting symptom was chronic headache. Four patients who presented during adulthood had chronic headache for many years before presentation. Angiographic evaluation of the lesion was performed in 21 patients. Fifteen patients were treated using endovascular techniques. Injection of the embolic material was performed after induction of systemic hypotension when the flow in the fistula was high. Complete occlusion of the arteriovenous shunt could be achieved in two patients with vein of Galen aneurysmal dilation (100% of patients with this type of malformation) and in five of the six patients with the mural type of malformation (83%). Among patients with the choroidal type of malformation, complete obliteration of the shunt could be achieved in three patients. In three patients with high-flow choroidal malformations, embolization carried out in a single sitting resulted in shunt reduction of nearly 90%. These patients received clinical follow up.

CONCLUSIONS

The authors' experience in evaluation and management of VGMs reveals that in areas of the world where access to dedicated specialist care is limited, the clinical presentation of VGMs can differ appreciably from the classic descriptions in the literature. Endovascular management of these lesions results in excellent angiographic and clinical results.

Hemimegalencephalic appearance of normal hemisphere in unilateral heterotopia and absent corpus callosum

We report two patients with medically refractory epilepsy who had MRI evidence of unilateral subcortical nodular heterotopia and agenesis of corpus callosum. The abnormal hemisphere was small, whereas the contralateral normal hemisphere appeared large and crossed the midline. Although the normal hemisphere was initially mistaken for hemimegalencephaly, there were no typical radiological features. Moreover, the electroencephalographic abnormalities lateralized to the hemisphere showing heterotopia. Because contralateral hemispheric abnormalities like heterotopia, hemimicrencephaly, and hemimegalencephaly can occur in patients with hemispheric heterotopias, we emphasize the importance of careful scrutiny of the contralateral hemisphere in patients with unilateral heterotopia. Absence of typical radiological features and appropriately lateralized electroencephalographic abnormalities will help differentiate the two. This is crucial when planning epilepsy surgery.

Percutaneous laser disc decompression: clinical experience at SCTIMST and long term follow up

BACKGROUND

Low backache (LBA) is now increasing in younger population due to misdirected spinal kinetics secondary to improper posture, heavy load lifting and motorbike driving. Hence minimally invasive procedures are increasingly sought after. Among these, PLDD is currently popular and in use. We present our long term follow-up in the use of Nd:YAG laser for PLDD.

AIM

To evaluate the efficacy of PLDD in treatment of contained herniation of lumbar discs & long term follow up results.

MATERIALS AND METHODS

Forty patients with contained lumbar disc herniation on MRI and who did not respond to 6 weeks conservative treatment were subjected to PLDD. L4-5 disc was treated in 31, L5-S1 in 12 and L1-2 and L3-4 in one each. Nd:YAG laser at 1064 nm was used for the procedure. Total laser energy of 1500-2000 Joules was delivered at the disc space depending upon the size.

RESULTS

There was immediate pain relief in 32/40 (80%). According to MacNab criteria good to fair response was seen in 37/40 (92%) and 3 patients (7.5%) responded poorly to this treatment. On follow up which ranged from 1 to 7 years, 34/40 (85%) had pain relief with no need for further treatment.

COMPLICATIONS

Significant pain at local puncture site was experienced by 8 (20%), pain during lasing was experienced by one. One patient developed muscular spasm.

CONCLUSION

Percutaneous laser disc decompression is a safe, relatively noninvasive and effective treatment modality for contained, nonsequestered, herniated lumbar disc disease in carefully selected patients.

Pyogenic cerebral abscess with discharging sinus complicating an embolized arteriovenous malformation

Brain arteriovenous malformations (AVM) are treated with endovascular embolization either as a definitive treatment or as an adjunct to surgery or stereotactic radiotherapy. Complications of AVM embolization are well known but infection of the embolised AVM nidus is extremely rare. On Pubmed search we found only a single case report of an infected brain AVM after embolization. We report a case of pyogenic cerebral abscess with superior sagittal sinus extension complicating an embolised AVM and discuss the possible etiopathogenesis.

Percutaneous vertebroplasty in the management of vertebral lesions

BACKGROUND

Debilitating backache due to different types of vertebral lesions is a common cause of morbidity in all age groups. Percutaneous vertebroplasty (PV) gives substantial pain relief and stabilizes the weak vertebrae. Most of the information regarding PV comes from the Western literature. The effect of PV in our population should be studied.

AIMS

The primary objective is to assess the therapeutic benefit of PV in alleviating back pain and improving the functional status in patients with painful pathologic vertebrae. The secondary objectives are to study the technical aspects of the procedure and their relation to outcome and complications.

SETTINGS AND DESIGN

This is a retrospective hospital-based (tertiary teaching hospital) study.

MATERIALS AND METHODS

From January 2001 to December 2004, 46 patients underwent PV procedures. Sixty-five vertebroplasties were done in 13 males and 33 female patients. Twenty-four (36.92%) procedures were done for osteoporotic compression collapse, 26 (40.0%) for hemangioma, and 15 (23.07%) for different vertebral body tumors and metastasis. The Wilcoxon signed rank test was used to evaluate the statistical significance of differences between the preoperative and postoperative levels of pain, mobility and analgesic usage.

RESULTS

Most of the patients had pain relief within 48 h. Only minor side effects were encountered. No patient had any deficit related to the procedure. On follow up of 3-48 months, all patients had statistically significant improvement in clinical condition (P < 0.001).

CONCLUSION

Percutaneous vertebroplasty is a safe and effective procedure in relieving debilitating backache and can be used to treat vertebral lesions in selected cases.

Carotid artery stenting: Results and long-term follow-up

BACKGROUND AND PURPOSE

The role of carotid artery stenting (CAS) as an alternative to carotid endarterectomy in the treatment of for symptomatic carotid artery stenosis is investigated.

MATERIALS AND METHODS

Forty-seven patients underwent CAS over 10-year period. Forty-nine vessels were treated. Stenosis quantification was done using North American symptomatic carotid endarterectomy trial method. The mean follow-up period by clinical and Duplex examination ranged is 5.6 years.

RESULTS

The technical success rate was 100%. There were four deaths (8.1%) and two (4.1%) minor strokes within thirty days of procedure. There was no major strokes. All patients with minor stroke achieved complete recovery at 1-month follow up. Two deaths occurred probably due to hyperperfusion syndrome (HS) and two due to cardiac arrest.

CONCLUSION

CAS is an effective treatment modality of symptomatic carotid artery disease but should be carefully done in high-risk groups having severe medical ailments and those having severe bilateral stenosis of the carotid arteries.

An incidental persistent falcine sinus with dominant straight sinus and hypoplastic distal superior sagittal sinus

An incidental persistent falcine sinus was detected in an otherwise normal brain on MRI in a 12-year-old girl who underwent imaging after clinical suspicion of acute disseminated encephalomyelitis. The falcine sinus was associated with a hypoplastic posterior third of the superior sagittal sinus and a dominant straight sinus. Generally, atresia or hypoplasia of the straight sinus is associated with a persistent falcine sinus in postnatal life; otherwise, the falcine sinus disappears before birth. We discuss the embryological basis for such an association in this case.

Hyperperfusion syndrome after supraaortic vessel interventions and bypass surgery

Cerebral hyperperfusion and hemorrhage is a recognized complication of endarterectomy, aortocarotid bypass surgery or angioplasty and stenting of the carotid or vertebral artery. We performed 87 balloon angioplasty, stenting and bypass surgery of arteries supplying the brain over the last 15 years. We have found 6 cases of hyperperfusion syndrome in a total of 87 procedures. So the incidence of hyperperfusion was noted as 6.89%. Two cases occurred after two combined procedures in a single sitting. Hyperperfusion syndrome is a well-known complication of craniocervical revascularisation procedures. But with proper care, including strict post procedural control of blood pressure and staged procedure in case of multiples vessel stenosis, these complications can be largely avoided.

Percutaneous retrieval of intravascular broken catheter fragments. A novel technique using a balloon

SUMMARY

We describe a novel technique to retrieve broken catheter fragments from the vascular tree at difficult locations using a balloon. A coronary balloon can be taken over a microwire into the catheter fragment to hold it after inflation of the balloon and then the whole assembly can be gradually taken out. We used this novel technique successfully in three patients where the snare failed to retrieve the broken catheter fragment from vascular tree.

Takayasu arteritis with multiple intracranial aneurysms. A case report

SUMMARY

A rare case of multiple cerebral aneurysms associated with Takayasu aortitis is reported. Only seven cases have been reported so far, all of which are from Japan. This is the first case with this association being reported from India. A 50-year-old hypertensive woman developed sudden onset severe headache and loss of consciousness. CT scan revealed subarachnoid haemorrhage in the suprasellar cisterns and mild hydrocephalus. The patient on admission had a rebleed producing a massive subarachnoid haemorrhage. Angiogram revealed occlusion of bilateral vertebral arteries and right common carotid artery. The left carotid artery was ectatic with saccular aneurysms in the ophthalmic segment and communicating segment. Aortogram showed the radiological picture of Takayasu arteritis Type III. Surgical clipping of the aneurysms was performed. However, the patient developed a massive right cerebral infarct in the postoperative period following which she expired. Abnormal haemodynamics in the overloaded cerebral circulation rather than primary arteritic involvement of intracranial vessels appears to be the cause of aneurysm formation.

Rhabdoid tumor of the thalamus

Rhabdoid tumors of the central nervous system are uncommon tumors. About 188 cases have been reported in the literature so far. In this report, we describe a case of a rhabdoid tumor of the thalamus in a 35-year-old male patient. Light microscopic and immunohistochemical features are discussed and the relevant literature reviewed.

Intracranial aneurysmal bone cyst manifesting as a cerebellar mass

A 17-year-old boy presented with symptoms of raised intracranial pressure for a month. Investigations revealed a large extra-cerebellar mass. The lesion was radically resected. It arose from the petrous bone. Histology revealed that the lesion was an aneurysmal bone cyst [ABC].

Tight binding of the phosphorylated alpha subunit of initiation factor 2 (eIF2alpha) to the regulatory subunits of guanine nucleotide exchange factor eIF2B is required for inhibition of translation initiation

Translation initiation factor 2 (eIF2) is a heterotrimeric protein that transfers methionyl-initiator tRNA(Met) to the small ribosomal subunit in a ternary complex with GTP. The eIF2 phosphorylated on serine 51 of its alpha subunit [eIF2(alphaP)] acts as competitive inhibitor of its guanine nucleotide exchange factor, eIF2B, impairing formation of the ternary complex and thereby inhibiting translation initiation. eIF2B is comprised of catalytic and regulatory subcomplexes harboring independent eIF2 binding sites; however, it was unknown whether the alpha subunit of eIF2 directly contacts any eIF2B subunits or whether this interaction is modulated by phosphorylation. We found that recombinant eIF2alpha (glutathione S-transferase [GST]-SUI2) bound to the eIF2B regulatory subcomplex in vitro, in a manner stimulated by Ser-51 phosphorylation. Genetic data suggest that this direct interaction also occurred in vivo, allowing overexpressed SUI2 to compete with eIF2(alphaP) holoprotein for binding to the eIF2B regulatory subcomplex. Mutations in SUI2 and in the eIF2B regulatory subunit GCD7 that eliminated inhibition of eIF2B by eIF2(alphaP) also impaired binding of phosphorylated GST-SUI2 to the eIF2B regulatory subunits. These findings provide strong evidence that tight binding of phosphorylated SUI2 to the eIF2B regulatory subcomplex is crucial for the inhibition of eIF2B and attendant downregulation of protein synthesis exerted by eIF2(alphaP). We propose that this regulatory interaction prevents association of the eIF2B catalytic subcomplex with the beta and gamma subunits of eIF2 in the manner required for GDP-GTP exchange.

Serine 48 in initiation factor 2 alpha (eIF2 alpha) is required for high-affinity interaction between eIF2 alpha(P) and eIF2B

Phosphorylation of the serine 51 residue in the alpha-subunit of translational initiation factor 2 in eukaryotes (eIF2 alpha) impairs protein synthesis presumably by sequestering eIF2B, a rate-limiting pentameric guanine nucleotide exchange protein which catalyzes the exchange of GTP for GDP in the eIF2-GDP binary complex. To further understand the importance of eIF2 alpha phosphorylation in the interaction between eIF2 alpha(P) and eIF2B proteins and thereby the regulation of eIF2B activity, we expressed the wild type (wt) and a mutant eIF2 alpha in which the serine 48 residue was replaced with alanine (48A mutant) in the baculovirus system. The findings reveal that the expression of both of these recombinant subunits was very efficient (15-20% of the total protein) and both proteins were recognized by an eIF2 alpha monoclonal antibody and were phosphorylated to the same extent by reticulocyte eIF2 alpha kinases. However, partially purified recombinant subunits (wt or 48A mutant) were not phosphorylated as efficiently as the eIF2 alpha subunit present in the purified reticulocyte trimeric eIF2 complex and were also found to inhibit the phosphorylation of eIF2 alpha of the trimeric complex. Furthermore, the extents of inhibition of eIF2B activity and formation of the eIF2 alpha(P)-eIF2B complex that occurs due to eIF2 alpha phosphorylation in poly(IC)-treated rabbit reticulocyte lysates were decreased significantly in the presence of insect cell extracts expressing the 48A mutant eIF2 alpha compared to those for wt. These findings support the hypothesis that the serine 48 residue is required for high-affinity interaction between eIF2 alpha(P) and eIF2B.

Conserved bipartite motifs in yeast eIF5 and eIF2Bepsilon, GTPase-activating and GDP-GTP exchange factors in translation initiation, mediate binding to their common substrate eIF2

In the initiation phase of eukaryotic translation, eIF5 stimulates the hydrolysis of GTP bound to eIF2 in the 40S ribosomal pre-initiation complex, and the resultant GDP on eIF2 is replaced with GTP by the complex nucleotide exchange factor, eIF2B. Bipartite motifs rich in aromatic and acidic residues are conserved at the C-termini of eIF5 and the catalytic (epsilon) subunit of eIF2B. Here we show that these bipartite motifs are important for the binding of these factors, both in vitro and in vivo, to the beta subunit of their common substrate eIF2. We also find that three lysine-rich boxes in the N-terminal segment of eIF2beta mediate the binding of eIF2 to both eIF5 and eIF2B. Thus, eIF5 and eIF2Bepsilon employ the same sequence motif to facilitate interaction with the same segment of their common substrate. In agreement with this, archaea appear to lack eIF5, eIF2B and the lysine-rich binding domain for these factors in their eIF2beta homolog. The eIF5 bipartite motif is also important for its interaction with the eIF3 complex through the NIP1-encoded subunit of eIF3. Thus, the bipartite motif in eIF5 appears to be multifunctional, stimulating its recruitment to the 40S pre-initiation complex through interaction with eIF3 in addition to binding of its substrate eIF2.

Reducing agents mitigate protein synthesis inhibition mediated by vanadate and vanadyl compounds in reticulocyte lysates

Recently, we synthesized and characterized vanadyl saccharides to evaluate the effects of various vanadate and vanadyl complexes, which differ in their oxidation states on various biomacromolecules and cellular activities (1, 2). Here, we report that both vanadate (+V oxidation state) and different vanadyl species (+IV oxidation state) such as vanadyl D-glucose, vanadyl diascorbate, and vanadyl sulfate, impair the formation of polysomes and inhibit the initiation of protein synthesis in hemin-supplemented rabbit reticulocyte lysates. Vanadate inhibits protein synthesis more severely than vanadyl species and is consistent with the idea that vanadate is reduced to vanadyl state intracellularly. The inhibition of protein synthesis caused by low concentrations (10-20 microM) of vanadate and vanadyl species is effectively mitigated by reducing agents such as dithiothreitol, reduced glutathione (GSH), or reduced pyridine dinucleotide. A significant decrease in the protein synthesis inhibition in vanadate-treated lysates by GSH suggests that the mechanism of protein synthesis inhibition by vanadate is different than the action of other oxidants such as heavy metal ions and oxidized glutathione. This suggestion is also consistent with the findings that vanadium compounds do not stimulate phosphorylation of the alpha (alpha) subunit of initiation factor 2 (eIF2) or decrease the guanine nucleotide exchange activity of eIF2B, which is required to exchange GDP for GTP in eIF2.GDP binary complex. The reduction of vanadate to vanadyl state and the subsequent complex formation of vanadyl species with the endogenous reducing compounds or with the -SH groups of certain proteins may be the cause for protein synthesis inhibition in lysates.