Expert survey on management of prostate cancer in India: Real-world insights into practice patterns

To gain insights on the diverse practice patterns and treatment pathways for prostate cancer (PC) in India, the Urological Cancer Foundation convened the first Indian survey to discuss all aspects of PC, with the objective of guiding clinicians on optimizing management in PC. A modified Delphi method was used, wherein a multidisciplinary panel of oncologists treating PC across India developed a questionnaire related to screening, diagnosis and management of early, locally advanced and metastatic PC and participated in a web-based survey (WBS) (n = 62). An expert committee meeting (CM) (n = 48, subset from WBS) reviewed the ambiguous questions for better comprehension and reanalyzed the evidence to establish a revote for specific questions. The threshold for strong agreement and agreement was ≥90% and ≥75% agreement, respectively. Sixty-two questions were answered in the WBS; in the CM 31 questions were revoted and 4 questions were added. The panelists selected answers based on their best opinion and closest to their practice strategy, not considering financial constraints and access challenges. Of the 66 questions, strong agreement was reached for 17 questions and agreement was achieved for 22 questions. There were heterogeneous responses for 27 questions indicative of variegated management approaches. This is one of the first Indian survey, documenting the diverse clinical practice patterns in the management of PC in India. It aims to provide guidance in the face of technological advances, resource constraints and sparse high-level evidence.

Neuromodulation for Restoration of Urinary and Bowel Control

Control of the lower urinary tract is a complex, multilevel process that involves the peripheral and central nervous systems. Patients with spinal cord diseases or injuries present with multiple bladder and bowel problems. The commonest are urinary, urgency, frequency, urge incontinence, retention and/or fecal incontinence. Though the first reports of neurostimulation to empty bladder came in 1970s', it was only in 1988 that Schmidt and Tanagho restarted discussion and application of neuromodulation and electrical stimulation of sacral nerve in urology. In April, 1999 - FDA approved the InterStim System for treatment of symptoms of urgency-frequency and urinary retention. In October 2000, Medtronic Commercial Release for SNS-Bowel was approved. In October 2002, the Tined lead was launched and N'Vision programmer was launched in the official market in Europe. SNM is now considered the third line of management in refractory cases of OAB, chronic NOUR, frequency and urgency. Role in neuropathic bladder is still being assessed. SNM includes a thorough preoperative assessment, PNE (Percutaneous Nerve Evaluation) without any muscle relaxation and finally installation of a permanent IPG after assessing reponse. We have an experience of over 20 patients in last 11 years. These include patients of refractory OAB, chronic NOUR and Cauda Equina Syndrome. We do a two-staged procedure in view of the high cost and abide by the AUA, EAU and ICS guidelines. Our long term results for neuropathic OAB are awaited.

COVID-19 in recent kidney transplant recipients

As the coronavirus disease 2019 (COVID-19) pandemic spread across the globe, transplant programs suffered a setback. We report the first experience of COVID-19 infection within 1 month of living donor kidney transplant (LDKT). We describe 2 LDKT recipients who were detected positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection at day 19 and day 7 posttransplant. They had minimal symptoms at diagnosis and did not develop any respiratory complications or allograft dysfunction. Immunosuppression was de-escalated; however, nasopharyngeal swab real-time reverse transcription polymerase chain reaction (rRT-PCR) remained positive for SARS-CoV-2 for a prolonged time. Younger age, absence of other comorbidities, and lower dose of anti-thymocyte globulin (ATG) used as induction possibly contributed to good outcome in our recent LDKT recipients compared with earlier published cases of recent deceased donor kidney transplant recipients with COVID-19.

Long-term Survival Results following Endobronchial RF Ablation in a Healthy-Porcine Model

This paper presents results from long-term survival study where healthy swine were ablated with a novel technology designed for treating early-stage non-small cell lung cancer using an endobronchial flexible catheter.Methods - The radiofrequency ablation (RFA) system has been presented previously and consisted of an ablation catheter, radiofrequency generator, irrigation pump for infusion of hypertonic saline (HS) and a laptop. The catheter carried an occlusion balloon, a 5 mm long RF electrode, with irrigation holes, and a 1 mm long electrode for bipolar impedance measurements. The outer diameter (OD) was 1.4 mm for compatibility with current bronchoscopes, navigation systems and radial EBUS. Nine swine were treated in this study with survival times of 1, 4 and 12 weeks (N=3 at each time point). In all animals, the treatment sites consisted of one location in the upper right lung (RUL) and another one in the lower right lung (RLL). CTs were taken pre-op, immediately post-op and at every 2 weeks post treatment. Ablation times ranged from 6 to 8 min and average applied power was 68 W (range 63 - 72 W).Results - At 1-week survival, large zones of necrotic tissue were observed in all respective 6 ablations. Ablation volumes had an average diameter of 3.2 cm at RUL locations and 3.8 cm in RLLs (likely due to longer RLL ablation durations). As time progressed, the necrotic tissue was gradually replaced with fibrotic tissue. At 4-week survival, the replacement was almost complete in all respective 3 animals. As a result, ablation volumes decreased to an average diameter of 1.3 cm at RUL locations and 2.3 cm in RLLs (likely due to longer RLL ablation durations). At 12-week survival, as the replacement process continued, histopathology revealed zones of residual necrotic tissue that were further reduced in size. Ablation zones had been resorbed and contracted by fibrous scar tissue. The average volume of the treatment effect decreased to 1.1 cm (RUL) and to 1.6 cm (RLL) in equivalent diameter. There were no complications in any of the nine animals.Conclusion - In healthy swine lungs, RFA with a 1.4-mm OD, radial-EBUS-sheath-compatible, endobronchial catheter was effective and safe. This system and therapeutic approach may be considered for further evaluation in minimally invasive treatment of tumorous lung nodules.

Early Preclinical Experience with a Novel Endobronchial Radiofrequency Ablation System for Lung Cancer Treatment

This paper introduces a novel technology for treating early-stage non-small cell lung cancer using an endobronchial approach via a flexible radiofrequency ablation (RFA) catheter. Methods - The RFA system consisted of an ablation catheter, radiofrequency generator, irrigation pump for infusion of hypertonic saline (HS) and a laptop. The catheter carried an occlusion balloon, a 5 mm long RF electrode, with irrigation holes, and a 1 mm long electrode for bipolar impedance measurements. The outer diameter was 1.4 mm for compatibility with current bronchoscopes, navigation systems and radial EBUS. The RFA system was extensively bench tested on fresh heart, liver and lung animal tissues using power levels of 30 - 60 W, RF energy delivery durations of 3 - 15 min and HS concentrations of 5% and 23.4%. Two swine were then treated at 60 W for 15 min per bronchus. Several bronchi were involved. For both animals and for all treatment sites, 20% HS was used. Animals were survived for six weeks. Results - Bench studies showed that 60 W, 7 - 15 min ablations can produce large ablation volumes, in excess of 3 - 4 cm diameter. In the chronic animal study, no clinically adverse events occurred. There was no evidence of hemorrhage. Animals vital signs, breathing patterns and their behavior were normal throughout the six-week period. Their appetite was normal and they gained weight according to expectations. The RF ablation created discrete volumes of thermal coagulative necrosis which were subsequently encapsulated ("walled off") by zones of organized fibrosis. The dimensions of coagulative necrotic sequestra met expectations, as at six weeks they exceeded volumes corresponding to 2 cm nodules, the size of tumors normally addressed in the peripheral lung by localized therapy. Conclusion - This therapy showed promise. Appropriate energy settings combined with suitable treatment locations safely produced large ablation volumes of uniform thermal coagulative necrosis. Further studies and optimization of treatment parameters can develop it into a mainstream therapy for treating early-stage lung tumors in humans.

A Study of the Role of 180W XPS Lithium Triborate Laser in the Treatment of Patients With Lower Urinary Tracts Symptoms Due to Benign Prostatic Hyperplasia

Introduction: Benign prostatic hyperplasia (BPH) is a disease of the prostate commonly seen in elderly males known to cause lower urinary tract symptoms (LUTS) that may require surgery as a part of treatment. Transurethral resection of the prostate (TURP) is considered the gold standard of surgical treatment, but it is not without complications. Laser photoselective vaporisation of the prostate (PVP), introduced in 1998 as an 80 W Nd:YAG laser which passed through a KTP (potassium-titanylphosphate) crystal, emerged as a safe alternative to TURP in selected cases. A recent upgrade to the Greenlight XPS 180 W powered with an LBO (lithium triborate) crystal has been available for use since 2012. Data on the use of this new upgrade is still being collected and analysed, especially in patients with large prostates or high risk cases. We analysed cases done at Jaslok Hospital over a 2-year period. Methods: A total of 34 patients who underwent Laser PVP using XPS 180W for LUTS due to BPH at Jaslok Hospital were part of this study. We analysed the pre- and postoperative variables and the intraoperative parameters of all patients. Results: The XPS 180W was found to be safe and efficacious. Eighteen patients were high-risk cases, classified as ASA (American Society of Anesthesiologists) Classes 3 and 4. Average postoperative catheter duration was 40.18 hours. In prostates of size <80 mL, an average of 229 kJ of energy was used. In large prostates (>80 mL), an average of 390 kJ of energy was used. No major complications were seen in any of the high-risk patients, classified as Clavien Dindo Class 3 and 4. The postoperative drop in IPSS (International Prostate Symptom Score) was 8.7. Conclusion: We found that Green Light Laser XPS 180W may be used for large (>80 g) prostates, hitherto an indication for open surgery, and that it may be used in high-risk patients, who were otherwise unfit for TURP. It is safe and efficacious. Further, multicenter trials are required to confirm the findings.

Reduction in polyamine catabolism leads to spermine-mediated airway epithelial injury and induces asthma features

BACKGROUND

Airway epithelial injury is a crucial component of acute and severe asthma pathogenesis and a promising target for treatment of refractory asthma. However, the underlying mechanism of epithelial injury remains poorly explored. Although high levels of polyamines, mainly spermine, have been found in asthma and comorbidity, their role in airway epithelial injury and the cause of their altered levels in asthma have not been explored.

METHODS

We measured key polyamine metabolic enzymes in lung samples from normal and asthmatic subjects and in mice with OVA-induced allergic airway inflammation (AAI). Polyamine metabolism was modulated using pharmacologic/genetic modulators. Epithelial stress and apoptosis were measured by TSLP levels and TUNEL assay, respectively.

RESULTS

We found loss of the polyamine catabolic enzymes spermidine/spermine-N (1)-acetyltransferase-1 (SAT1) and spermine oxidase (SMOX) predominantly in bronchial epithelial cells (BECs) of human asthmatic lung samples and mice with AAI. In naïve mice, SAT1 or SMOX knockdown led to airway hyper-responsiveness, remodeling, and BEC apoptosis. Conversely, in mice with AAI, overexpression of either SAT1 or SMOX alleviated asthmatic features and reduced TSLP levels and BEC apoptosis. Similarly, while pharmacological induction of SAT1 and SMOX using the polyamine analogue bis(ethyl)norspermine (BENSPM) alleviated asthmatic features with reduced TSLP levels and BEC apoptosis, pharmacological inhibition of these enzymes using BERENIL or MDL72527, respectively, worsened them. Spermine accumulation in lungs correlated with BEC apoptosis, and spermine treatment caused apoptosis of human BEAS-2B cells in vitro.

CONCLUSIONS

Spermine induces BEC injury. Induction of polyamine catabolism may represent a novel therapeutic approach for asthma via reversing BEC stress.

Study of efficacy and safety of modified adjuvant intraperitoneal chemotherapy regimen in carcinoma ovary

OBJECTIVE

It has been demonstrated in few trials that intraperitoneal and intravenous (IP/IV) chemotherapy improves survival in advanced stage ovarian cancer (OC). However, in view of high treatment-related toxicities, various modifications in treatment schedules have been tried. In this study, response and tolerability of IP paclitaxel on day 8 with IV paclitaxel on day 1 and IV cisplatin day 2 in carcinoma ovary were evaluated.

PATIENTS AND METHODS

In this prospective observational study, from March 2013 to December 2015, the efficacy and tolerability of adjuvant IP/IV chemotherapy in optimally cytoreduced Stage III epithelial OC (EOC) patients were assessed.

RESULTS

Totally, sixty patients were enrolled. The median age of patients was 53 years (32-67 years). Out of a total of 360 IP cycles, 316 cycles (88%) were completed. Forty-five patients (76%) received all the 6 cycles by IP route. Eight out of those 45 patients had one or more adjustment including delay or dose reduction. After median follow-up of 22 months, eight patients (14%) had local or systemic recurrence. Median progression-free survival not reached yet. Catheter block was seen in five cases. Two cases had needle displacement and extravasations of drug around the port chamber. Six patients had Grade 3 abdominal pain and cramp. Grade 3/4 leukopenia was experienced by thirty patients (50%), but febrile neutropenia occurred in only 6 (10%) patients. Renal complication present in 4 (7%) patients.

CONCLUSIONS

In Indian patients, adjuvant chemotherapy with day 8 I/P paclitaxel in optimally cytoreduced EOC is associated with comparable survival outcomes, less side effects and high treatment completion rate relative to literature published from Western countries.

The Urological Society of India survey on urinary incontinence practice patterns among urologists

Introduction:

The Urological Society of India guidelines panel on urinary incontinence (UI) conducted a survey among its members to determine their practice patterns in the management of UI. The results of this survey are reported in this manuscript.

Methods:

An anonymous online survey was carried out among members of the USI to determine their practice patterns regarding UI using a predeveloped questionnaire on using SurveyMonkey^®. A second 4-question randomized telephonic survey of the nonresponders was performed after closure of the online survey. Data were analyzed by R software 3.1.3 (P < 0.05 significant).

Results:

A total of 468 of 2109 (22.2%) members responded to the online survey. Nearly 97% were urologists, 74.8% were working at a private, and 39.4% were in an academic institution. Almost all were managing UI. 84.2% had local access to a urodynamics (UDS) facility. 85.8% would check postvoid residual urine for all the patients. Voiding diary, symptom scores, quality of life scores, pad test, Q-tip test, stress test, uroflow, and cystoscopy were ordered as part of evaluation by 86.0%, 49.8%, 24.4%, 22.0%, 6.0%, 71.8%, 69.2%, and 34.7%, respectively. 47.6% would order a UDS for patients with urgency UI who fail conservative treatment. 36.9% would get UDS prior to all stress UI surgery. Seventy-five percent would make a diagnosis of intrinsic sphincter deficiency. Solifenacin was the first choice for urgency UI in general and darifenacin was preferred in elderly. Botulinum was the first choice for refractory urgency UI. Midurethral sling was the commonest procedure for surgical management of SUI (95.1%). 147 of the 1641 non responders were randomly sampled telephonically. Telephonic respondents had similar access to UDS facility but had performed fewer lifetime number of post-prostatectomy incontinence (PPI) surgeries. Combining data from both surveys, total number of artificial sphincters and PPI surgeries ever performed by USI members was estimated at 375 and 718 respectively.

Conclusion:

This survey provides important new data and elicits critical differences in management practices based on demographics.

Intersecting pentagons as surrogate for identifying the use of mini mental state examination in assessment of dementia in a largely illiterate population

Background and Rationale:

The mini-mental state evaluation (MMSE) is often used to identify patients with dementia. One component of the MMSE is the intersecting pentagon copying (IPC) test, which may be difficult to be used in an illiterate population.

Materials and Methods:

A post hoc analysis on an elderly population (60 years and above) from Himachal Pradesh was carried out. The data of only 1,513 elderly individuals out of a total of 2,000 participants with a score of more than 26 (nondemented) out of a possible score of 30 on cognitive battery available were used. The scores on the IPC were evaluated and their association with some demographic variables was also assessed.

Results:

Illiterate participants, female participants, those with greater age, and the rural/tribal population groups faced the most difficulty in drawing the intersecting pentagons and even greater difficulty in drawing them correctly.

Discussion:

The IPC presents challenges for people who are illiterate and the scoring method needs to be addressed and changed particularly when the test is used in largely illiterate populations.

Spectrum of acute kidney injury in the Himalayan region

Acute kidney injury (AKI) is common in hospitalized patients and is an important cause of mortality. This is a descriptive study of AKI in patients from Himachal Pradesh, India, located in Western Himalayan region. Over a period of 1 year, 102 patients with clinical and laboratory evidence of azotemia were included. Out of 102 patients, 84.3% had community acquired AKI and 15.7% had hospital acquired AKI. Medical causes were leading contributors (85.3%), with septicemia being the main factor (33.3%). Multiorgan failure was present in 59.8% patients. The overall mortality was 29.2%, and community acquired AKI was associated with higher mortality as compared to hospital-acquired AKI (22.5% vs 6.7%). AKI is still common in community and associated with high mortality. Septicemia, volume depletion and nephrotoxins were the leading cause of AKI in our study. Our study highlights the presence of hypotension, multiorgan failure and oliguria with mortality. Community-acquired AKI had higher mortality than hospital-acquired AKI.

Vitamin B12 deficiency presenting as pyrexia

Vitamin B12 deficiency is an uncommon cause of pyrexia. We report the case of a patient who presented with pyrexia and anaemia, which after exclusion of infective, inflammatory or endocrine causes was attributed to megaloblastic anaemia secondary to vitamin B12 deficiency. The patient's fever responded to treatment of vitamin B12 deficiency.

Marchiafava-Bignami disease

Marchiafava- Bignami disease is the symmetrical demyelination of the middle portion of the corpus callosum observed in people with chronic alcoholism. We report two male patients who had history of chronic alcoholism, different clinical presentation and MRI findings consistent with the diagnosis of Marchiafava-Bignami disease.

Alkaptonuria and intramedullary calcification

Alkaptonuria is a rare disorder of metabolism caused by deficiency of homogentisic acid oxidase enzyme and characterized by triad of homogentisic aciduria (dark urine), relentlessly progressive arthritis and ochronosis. We have documented a case with typical features of alkaptonuria along with intramedullary calcification which has not been reported in the literature before.

Progressive multifocal leukoencephalopathy--as a presenting manifestation of AIDS

Progressive multifocal leukoencephalopathy (PML) is an opportunistic demyelinating disease caused by the ubiquitous, usually non pathogenic JC Polyomavirus. We report a case of PML as a presenting manifestation of AIDS in a forty five year old man on the basis of clinical features and neuroradiology.

Intramolecular addition of acyl radicals to alpha-substituted vinylogous carbonates: demonstrating the effect of ring size on acyclic stereocontrol

The level of stereocontrol obtained in the reduction of the free radical derived from the intramolecular addition of an acyl radical to an alpha-branched vinylogous carbonate is dependent upon the ring-size of the cyclic ether.

Characterization of the Escherichia coli sigma E regulon

Escherichia coli responds to the accumulation of misfolded proteins by inducing the transcription of heat shock genes. Efinal sigma(E) RNA polymerase controls one of the two heat shock regulons of E. coli. This regulon is activated upon accumulation of misfolded polypeptides in the double membrane envelope of E. coli. final sigma(E) (RpoE) is a member of the extracytoplasmic function subfamily of sigma factors. Here we asked how many genes are activated by Efinal sigma(E) RNA polymerase and what is the identity of these genes. Using two independent genetic approaches, 20 E. coli promoters were identified which activate reporter gene transcription in a final sigma(E)-dependent manner. In all cases examined, a canonical final sigma(E) binding site could be revealed upon mapping transcriptional start sites. 10 identified promoters activated the transcription of previously identified genes with four genes acting directly on the folding of E. coli envelope proteins (dsbC, fkpA, skp, and surA). The remaining promoters transcribed genes that are presumed to encode hitherto unknown extracytoplasmic functions and were named ecf (ecfA-ecfM). Two of these ecf genes were found to be essential for E. coli growth.

Protein folding in the periplasm in the absence of primary oxidant DsbA: modulation of redox potential in periplasmic space via OmpL porin

Disulfide bond formation in Escherichia coli is a catalyzed reaction accomplished by DsbA. We found that null mutations in a new porin gene, ompL, allowed a total bypass of the DsbA requirement for protein oxidation. These mutations acted as extragenic null suppressors for dsbA, and restored normal folding of alkaline phosphatase and relieved sensitivity to dithiothreitol. ompL dsbA double mutants were completely like wild-type mutants in terms of motility and lack of mucoidy. This suppression was not dependent on DsbC and DsbG, since the oxidation status of these proteins was unaltered in ompL dsbA strains. Purified OmpL allowed diffusion of small solutes, including sugars, but the suppression was not dependent on the carbon sources used. Suppression by ompL null mutations required DsbB, leading us to propose a hypothesis that DsbB oxidizes yet unidentified, low-molecular-weight redox agents in the periplasm. These oxidized agents accumulate and substitute for DsbA if their leakage into the medium is prevented by the absence of OmpL, presumed to form a specific channel for their diffusion.

Comparison of analytical methods for quantitation of isolated porcine hepatocyte yields

As cell-based therapies receive approval for clinical evaluation and use, the development of reliable methods to quantify cell number and control the dose of therapy delivered is becoming increasingly important. An example is the determination of the number and volume of primary porcine hepatocytes used in an extracorporeal treatment for patients with liver disease. Conventional cell counting using optical microscopy was compared against two alternate methods to quantify isolated porcine hepatocytes: (1) automated cell counting using a commercially available particle characterization instrument, and (2) quantitation by cell mass. Methods were compared based on accuracy, precision, specificity, linear range, and ruggedness. The automated method delivered substantially improved accuracy, precision, and ruggedness when compared to the conventional optical method. It also provided valuable information about the size distribution of cell preparations, which often contained clumps of cells, and showed that processing steps such as cryopreservation can alter the size characteristics of a cell population. The automated method was also faster, and was well suited to use in a commercial manufacturing process. The mass-based method was simple and inexpensive, but suffered from nonlinearity at low cell concentrations. Automated cell quantitation using a commercially available particle characterization instrument proved to be the preferred method for obtaining accurate and consistent porcine hepatocyte counts in a timely manner.

Direct Agrobacterium tumefaciens-mediated transformation of Hyoscyamus muticus hairy roots using green fluorescent protein

Hyoscyamus muticus hairy root segments were infected with Agrobacterium tumefaciens ASE containing the binary vector pCGN1548 with a green fluorescent protein (GFP) reporter gene under the control of the CaMV 35S promoter. The roots were incubated on callus-inducing medium to generate transformed cells. Transformants were selected on medium containing 50 and 100 mg/L kanamycin and screened by visual inspection for GFP expression. Highly fluorescent cells were incubated on phytohormone-free medium for regeneration of the hairy root phenotype. This infection technique can be applied directly to existing hairy root cultures which have been previously characterized and selected for desirable physiological traits. These studies also indicate that GFP is not toxic to H. muticus plant tissue and that H. muticus hairy roots have minimal autofluorescence which allows for clear observation of GFP.

Escherichia coli tol-pal mutants form outer membrane vesicles

Mutations in the tol-pal genes induce pleiotropic effects such as release of periplasmic proteins into the extracellular medium and hypersensitivity to drugs and detergents. Other outer membrane defective strains such as tolC, lpp, and rfa mutations are also altered in their outer membrane permeability. In this study, electron microscopy and Western blot analyses were used to show that strains with mutations in each of the tol-pal genes formed outer membrane vesicles after growth in standard liquid or solid media. This phenotype was not observed in tolC and rfaD cells in the same conditions. A tolA deletion in three different Escherichia coli strains was shown to lead to elevated amounts of vesicles. These results, together with plasmid complementation experiments, indicated that the formation of vesicles resulted from the defect of any of the Tol-Pal proteins. The vesicles contained outer membrane trimeric porins correctly exposed at the cell surface. Pal outer membrane lipoprotein was also immunodetected in the vesicle fraction of tol strains. The results are discussed in view of the role of the Tol-Pal transenvelope proteins in maintaining outer membrane integrity by contributing to target or integrate newly synthesized components of this structure.

A new heat-shock gene, ppiD, encodes a peptidyl-prolyl isomerase required for folding of outer membrane proteins in Escherichia coli

We have identified a new folding catalyst, PpiD, in the periplasm of Escherichia coli. The gene encoding PpiD was isolated as a multicopy suppressor of surA, a mutation which severely impairs the folding of outer membrane proteins (OMPs). The ppiD gene was also identified based on its ability to be transcribed by the two-component system CpxR-CpxA. PpiD was purified to homogeneity and shown to have peptidyl-prolyl isomerase (PPIase) activity in vitro. The protein is anchored to the inner membrane via a single transmembrane segment, and its catalytic domain faces the periplasm. In addition, we have identified by site-directed mutagenesis some of the residues essential for its PPIase activity. A null mutation in ppiD leads to an overall reduction in the level and folding of OMPs and to the induction of the periplasmic stress response. The combination of ppiD and surA null mutations is lethal. This is the first time two periplasmic folding catalysts have been shown to be essential. Another unique aspect of PpiD is that its gene is regulated by both the Cpx two-component system and the sigma32 heat shock factor, known to regulate the expression of cytoplasmic chaperones.

The extracytoplasmic function sigma factors: role and regulation

Alternative sigma factors provide a means of regulating gene expression in response to various extracellular changes. One such class of sigma factors appears to control a variety of functions, including expression of heat-shock genes in Escherichia coli, biosynthesis of alginates and carotenoids in Pseudomonas aeruginosa and Myxococcus xanthus, respectively, iron uptake in E. coli and Pseudomonas spp., nickel and cobalt efflux in Alcaligenes europhus, plant pathogenicity in Pseudomonas syringae and synthesis of outer membrane proteins in Photobacterium sp. strain SS9. Most of these activities deal with extracytoplasmic functions, and such sigmas have been designated as ECF sigma factors. They have also been characterized in Mycobacteria as well as gram-positive bacteria such as Streptomyces coelicolor and Bacillus subtilus and the archaea Sulpholobus acidocaldarius. ECF factors belong to a subfamily of the sigma 70 class, based on their sequence conservation and function across bacterial species. The promoter consensus sequences recognized by the ECF factors are also highly conserved. In most of the cases, the activity of these factors is modulated by a cognate inner membrane protein that has been shown, both in E. coli and in P. aeruginosa, to act as an anti-sigma activity. This inner membrane protein is presumed to serve as a sensor and signalling molecule, allowing an adaptive response to specific environmental change. Presumably, an on-and-off switch of the anti-sigma activity leads to the release of the sigma factor and thereby to the co-ordinate transcription of the specific regulon it governs.

The functional properties of DsbG, a thiol-disulfide oxidoreductase from the periplasm of Escherichia coli

Genetic studies have recently identified DsbG, a new member of the dsb group of redox proteins, which catalyze protein disulfide bond formation in the periplasm of Escherichia coli. We now demonstrate that DsbG functions primarily as an oxidant during protein disulfide bond formation, which is consistent with the low stability of its active site disulfide bond. There are indications, however, that the substrate range of DsbG may be narrower than the other periplasmic oxidative enzymes, DsbA and DsbC. Our observations further elaborate the pathway of disulfide bond formation in E. coli.

Contributions of substrate binding to the catalytic activity of DsbC

DsbA and DsbC are involved in protein disulfide bond formation in the periplasm of Gram-negative bacteria. The two proteins are thought to fulfill different functions in vivo, DsbA as a catalyst of disulfide bond formation and DsbC as a catalyst of disulfide bond rearrangement. To explore the basis of this catalytic complementarity, the reaction mechanism of DsbC has been examined using unstructured model peptides that contain only one or two cysteine residues as substrates. The reactions between the various forms of the peptide and DsbC occur at rates up to 10(6)-fold faster than those that involve glutathione and DsbC, and they were constrained to occur at only one sulfur atom of disulfide bonds involving the peptide. Mixed disulfide complexes of DsbC and the peptide were 10(4)-fold more stable than the corresponding mixed disulfides with glutathione. These observations suggest that noncovalent binding interactions occur between the peptide and DsbC, which contribute to the very rapid kinetics of substrate utilization. The interactions between DsbC and the peptide appear to be more substantial than those between DsbA and the same peptide. The differences in the reaction of the peptide at the active sites of DsbA and DsbC provide insight into why DsbC is the better catalyst of disulfide bond rearrangement and how the active site chemistry of these structurally related proteins has been adapted to fulfill complementary functions.

Making and breaking disulfide bonds

It is now well established that protein folding requires the assistance of folding helpers in vivo. The formation or isomerization of disulfide bonds in proteins is a slow process requiring catalysis. In nascent polypeptide chains the cysteine residues are in the thiol form. The formation of the disulfide bonds usually occurs simultaneously with the folding of the polypeptide, which means in the endoplasmic reticulum of eukaryotes or in the periplasm of Gram-negative bacteria. In prokaryotes, the existence of redox proteins involved in the formation of disulfide bonds containing proteins has recently been revealed in the periplasm. The discovery of these redox proteins through various genetic approaches will be summarized, as well as the most recent insights regarding their biochemical and biological activities.

A new Escherichia coli gene, dsbG, encodes a periplasmic protein involved in disulphide bond formation, required for recycling DsbA/DsbB and DsbC redox proteins

We have identified and functionally characterized a new Escherichia coli gene, dsbG, whose product is involved in disulphide bond formation in the periplasm. The dsbG gene was cloned from a multicopy plasmid library lacking the dsbB redox protein-encoding gene. Multicopy dsbG-carrying clones were selected, since they allowed E. coli to grow at lethal concentrations of dithiothreitol. In a complementary genetic approach, point mutations were independently obtained and mapped to the dsbG gene. Such mutations led simultaneously to a dithiothreitol-sensitive phenotype and an increased sigmaE-dependent heat shock response, which reflects the presence of misfolded proteins in the extracytoplasm. In agreement with these observations, dsbG mutants were shown to accumulate reduced forms of a variety of disulphide bond-containing proteins in the periplasm. This DsbG defect could be rescued by addition to the growth medium of either oxidized dithiothreitol or cystine, or by overexpression of the dsbA or dsbB genes. DsbG is synthesized as a precursor form of 27.5 kDa and processed to a 25.7kDa mature species located in the periplasm. DsbG was overproduced, purified to homogeneity and shown to have redox properties of thiol-disulphide oxidoreductases in vitro. Replacement of the first Cys residue of the predicted active site, Phe-(Xaa)4-Cys-Pro-Tyr-Cys by Ala, completely inactivated DsbG protein function. Taken together, all our results demonstrate that DsbG acts in vivo as an efficient thiol-disulphide oxidase. In addition, dsbG is the first member of the dsb family for which null mutations are conditionally lethal and can be propagated only if supplemented with oxidants in the growth medium. We propose that the main role of DsbG is to maintain the proper redox balance between the DsbA/DsbB and DsbC systems.

Modulation of the Escherichia coli sigmaE (RpoE) heat-shock transcription-factor activity by the RseA, RseB and RseC proteins

The sigma(E) (RpoE) transcription factor of Escherichia coli regulates the expression of genes whose products are devoted to extracytoplasmic activities. The sigma(E) regulon is induced upon misfolding of proteins in the periplasm or the outer membrane. Similar to other alternative sigma factors, the activity of sigma(E) is tightly regulated in E. coli. We have previously shown that sigma(E) is positively autoregulated at the transcriptional level. DNA sequencing, coupled with transcriptional analyses, have shown that sigma(E) is encoded by the first gene of a four-gene operon. The second gene of this operon, rseA, encodes an anti-sigma(E) activity. This was demonstrated at both the genetic and biochemical levels. For example, mutations in rseA constitutively increase sigma(E) activity. Consistent with this, overproduction of RseA leads to an inhibitory effect on sigma(E) activity. Topological analysis of RseA suggests the existence of one transmembrane domain, with the N-terminal part localized in the cytoplasm. Overproduction of this N-terminal domain alone was shown to inhibit sigma(E) activity. These observations were confirmed in vitro, because either purified RseA or only its purified N-terminal domain inhibited transcription from Esigma(E)-dependent promoters. Furthermore, RseA and sigma(E) co-purify, and can be co-immunoprecipitated, and chemically cross-linked. The sigma(E) activity is further modulated by the products of the remaining genes in this operon, rseB and rseC. RseB is a periplasmic protein, which negatively regulates sigma(E) activity and specifically interacts with the C-terminal periplasmic domain of RseA. In contrast, RseC is an inner membrane protein that positively modulates sigma(E) activity. Most of these protein-protein interactions were verified in vivo using the yeast two-hybrid system.

Signal transduction pathways in response to protein misfolding in the extracytoplasmic compartments of E. coli: role of two new phosphoprotein phosphatases PrpA and PrpB

It is now well established that the sigmaE regulon of Escherichia coli is induced by misfolding of proteins in the periplasm and the outer membrane. htrA belongs to this regulon and encodes a periplasmic protease involved in the degradation of misfolded proteins. htrA transcription is also under the positive control of a two component signal transduction system CpxR CpxA. Closer examination of the putative signal transduction pathway modulating htrA transcription has led us to the identification of two new genes. Biochemical and genetic evidence shows that these two genes encode two phosphoprotein phosphatases, designated PrpA and PrpB. These are the first examples of typical serine/threonine and tyrosine phosphatases described in E. coli. PrpA and PrpB are involved in signaling protein misfolding via the CpxR CpxA transducing system. In addition, both PrpA and PrpB modulate the phosphorylated status of some other phosphoproteins in E. coli. Finally, we show that PrpA is a heat shock protein.

Protein misfolding in the cell envelope of Escherichia coli: new signaling pathways

Depending on their cellular localization, misfolded proteins in Escherichia coli trigger two different heat-shock responses. Cytoplasmic proteins induce the 'classical' heat-shock regulon transcribed by the E sigma 32 polymerase. By contrast, misfolding of proteins in the cell envelope induces the newly described E sigma E-dependent regulon. This implies that there is an inducible transduction machinery in the inner membrane. The response to protein misfolding in the cell envelope is a finely tuned system regulated by a cascade of phosphorylation and dephosphorylation reactions.

Identification and characterization of HsIV HsIU (ClpQ ClpY) proteins involved in overall proteolysis of misfolded proteins in Escherichia coli

Heat shock response in Escherichia coli is autoregulated. Consistent with this, mutations in certain heat shock genes, such as dnaK, dnaJ, grpE or htrC lead to a higher constitutive heat shock gene expression at low temperatures. A similar situation occurs upon accumulation of newly synthesized peptides released prematurely from the ribosomes by puromycin. We looked for gene(s) which, when present in multicopy, prevent the constitutive heat shock response associated with htrC mutant bacteria or caused by the presence of puromycin. One such locus was identified and shown to carry the recently sequenced hslV hslU (clpQ clpY) operon. HslV/ClpQ shares a very high degree of homology with members of the beta-type subunit, constituting the catalytic core of the 20S proteasome. HslU/ClpY is 50% identical to the ClpX protein of E. coli, which is known to present large polypeptides to its partner, the ATP-independent proteolytic enzyme ClpP. We show that, in vivo, HslV and HslU interact and participate in the degradation of abnormal puromycylpolypeptides. Biochemical evidence suggests that HslV/ClpQ is an efficient peptidase whose activity is enhanced by HslU/CIpY in the presence of ATP.