Basic amino acid residues at the carboxy-terminal eleven amino acid region of the phosphoprotein (P) are required for transcription but not for replication of vesicular stomatitis virus genome RNA

The phosphoprotein (P) of vesicular stomatitis virus (VSV) serotypes New Jersey [P(NJ)] and Indiana [P(I)] contains a highly conserved carboxy-terminal domain which is required for binding to the cognate N-RNA template as well as to form a soluble complex with the nucleocapsid protein N in vivo. We have shown that the deletion of 11 amino acids from the C terminal end of the P(I) protein abolishes both the template binding and the complex forming activity with the N protein. Within this region, there are conserved basic amino acid residues (R260 and K262) that are potential candidates for such interactions. We have generated mutant P proteins by substitution of these basic amino acid residues with alanine and studied their role in both transcription and replication. We have found that the R260A mutant failed to bind to the N-RNA template, whereas the K262A mutant bound efficiently as the wild-type protein. The R260A mutant, as expected, was unable to support mRNA synthesis in vitro in a transcription reconstitution reaction as well as transcription in vivo of a minigenome using a reverse genetic approach. However, the K262A mutant supported low level of transcription (12%) both in vitro and in vivo, suggesting that direct template binding of P protein through the C-terminal domain is necessary but not sufficient for optimal transcription. Using a two-hybrid system we have also shown that both R260A and K262A mutants interact inefficiently with the L protein, suggesting further that the two point mutants display differential phenotype with respect to binding to the template. In addition, both R260A and K262A mutants were shown to interact efficiently with the N protein in vivo, indicating that these mutants form N-P complexes which are presumably required for replication. This contention is further supported by the demonstration that these mutants support efficient replication of a DI RNA in vivo. Since the transcription defective P mutants can support efficient replication, we propose that the transcriptase and the replicase are composed of two distinct complexes containing (L-P2-3) and L-(N-P), respectively.

Phosphorylation within the amino-terminal acidic domain I of the phosphoprotein of vesicular stomatitis virus is required for transcription but not for replication

Phosphorylation by casein kinase II at three specific residues (S-60, T-62, and S-64) within the acidic domain I of the P protein of Indiana serotype vesicular stomatitis virus has been shown to be critical for in vitro transcription activity of the viral RNA polymerase (P-L) complex. To examine the role of phosphorylation of P protein in transcription as well as replication in vivo, we used a panel of mutant P proteins in which the phosphate acceptor sites in domain I were substituted with alanines or other amino acids. Analyses of the alanine-substituted mutant P proteins for the ability to support defective interfering RNA replication in vivo suggest that phosphorylation of these residues does not play a significant role in the replicative function of the P protein since these mutant P proteins supported replication at levels > or = 70% of the wild-type P-protein level. However, the transcription function of most of the mutant proteins in vivo was severely impaired (2 to 10% of the wild-type P-protein level). The level of transcription supported by the mutant P protein (P(60/62/64)) in which all phosphate acceptor sites have been mutated to alanines was at best 2 to 3% of that of the wild-type P protein. Increasing the amount of P(60/62/64) expression in transfected cells did not rescue significant levels of transcription. Substitution with other amino acids at these sites had various effects on replication and transcription. While substitution with threonine residues (P(TTT)) had no apparent effect on transcription (113% of the wild-type level) or replication (81% of the wild-type level), substitution with phenylalanine (P(FFF)) rendered the protein much less active in transcription (< 5%). Substitution with arginine residues led to significantly reduced activity in replication (6%), whereas glutamic acid substituted P protein (P(EEE)) supported replication (42%) and transcription (86%) well. In addition, the mutant P proteins that were defective in replication (P(RRR)) or transcription (P(60/62/64)) did not behave as transdominant repressors of replication or transcription when coexpressed with wild-type P protein. From these results, we conclude that phosphorylation of domain I residues plays a major role in in vivo transcription activity of the P protein, whereas in vivo replicative function of the protein does not require phosphorylation. These findings support the contention that different phosphorylated states of the P protein regulate the transcriptase and replicase functions of the polymerase protein, L.

Fluorescein as a marker for subretinal transplantation of human fetal neural retina

PURPOSE

To investigate the effect of fluorescein on human fetal neural retina and adult rat retina; and to use fluorescein to map the area of subretinal transplantation.

METHODS

In vitro: Human fetal neural retina (8 to 14 weeks gestational age) was incubated in 0.03% fluorescein in Dulbecco's Modified Eagles Medium (DMEM) or DMEM alone for 30 min. Viability was determined using the trypan blue exclusion test, and results were compared. Effects of the fluorescein on cell morphology were assessed by observation of primary cultures for 1 week. In vivo: Human fetal neural retina was mechanically dissociated in 0.03% fluorescein in DMEM and transplanted to the subretinal space of immunosuppressed rats. To control for the effect of fluorescein on the grafted tissue, transplants were also performed in DMEM only. After transplantation, indirect ophthalmoscopy and true color fundus photography were performed to document the area covered by the transplant. One month after transplantation, the appearance of grafts exposed to fluorescein was compared to those that were not, at the light microscopic level.

RESULTS

In vitro: Exposure of human fetal neural retina to fluorescein had no effect on viability. Similarly, in tissue culture, the fluorescein-exposed cells exhibited the same phenotype as the controls. In vivo: Immediately after transplantation the graft site was clearly outlined within the subretinal area and fluoresced intensely. There were no traces of the dye 2 h after transplantation. Cells that were transplanted with fluorescein survived transplantation, and one month after transplantation could be seen forming subretinal grafts. No differences were noted between these and control grafts.

CONCLUSIONS

Fluorescein is an effective dye for immediate and transient localization of trans-scleral transplants to the subretinal space. It allows mapping of the area covered by the injection without interfering with the viability and differentiation of the transplanted cells. It allows unequivocal photo- and video-documentation in both the albino and pigmented fundi. It is already FDA approved for many other extra- and intraocular studies and now has directly been shown to be non-toxic to both human fetal neural retina and adult rodent retina.

Inhibition of clastogenic effects of arsenic through continued oral administration of garlic extract in mice in vivo

Crude aqueous extract of garlic bulbs (Allium sativum L. single clove variety) was administered by gavage to mice of both sexes daily for up to 30 and 60 days, in doses corresponding to 6 g for a 60 kg human body. Sodium arsenite (at 1/50 of LD50 dose) was injected subcutaneously to mice on every 7th day of the experiment. Chromosome preparations made from bone marrow following flame drying Giemsa schedule were screened for chromosomal aberrations. The clastogenic affects of prolonged exposure to sodium arsenite --a strong clastogen-- was reduced by a highly significant amount when crude garlic extract, in the dose used, was given daily to the mice by intubation for the same period.

Fluorescent Gram stain in the microbiologic diagnosis of infectious keratitis and endophthalmitis

PURPOSE

To verify the sensitivity of a recently described technique of fluorescent Gram stain (FGS) and evaluate its role in direct microscopic examination of clinical ocular samples.

METHODS

In the first part of the study, culture suspensions of 10 bacterial isolates were stained, using FGS and conventional Gram stain (CGS), and were assessed for morphology, and Gram sign. In the second part, 39 corneal scrapings and 18 vitreous biopsy materials were stained and observed by both methods.

RESULTS

Gram reaction and morphology of the bacteria, using CGS and FGS, were compared against culture. In both parts of the study, the sensitivity of CGS was significantly higher than FGS in the detection of Gram positive reaction (p = 0.01, 0.02). The specificities and predictive values of CGS and FGS were comparable in the evaluation of clinical samples. The bacterial morphology was demonstrated better (p = 0.01) with CGS. Significant quenching of fluorescence and change in Gram reaction with time were noted in FGS.

CONCLUSIONS

The low sensitivity, quenching of fluorescence and change in Gram reaction presently preclude the usage of FGS as a diagnostic tool in ocular infections.

Role of cellular kinases in the gene expression of nonsegmented negative strand RNA viruses

Nonsegmented negative strand RNA viruses package an RNA-dependent RNA polymerase composed of two subunits, a large protein L and a phosphoprotein P, for transcription and replication of their genome RNAs. The RNA polymerase activity resides within the L protein, while the P protein acts as a transcription factor or transactivator of the polymerase. Since P protein is heavily phosphorylated and phosphorylation is known to regulate function of many viral as well as cellular proteins, the role of phosphorylation of P protein in the gene expression of this group of RNA viruses has recently been investigated. Through expression in bacteria the P protein was produced in large quantity in the nonphosphorylated form and involvement of cellular kinase(s) in its phosphorylation was studied. Casein kinase II and/or protein kinase C have been shown to play a critical role in the activation of P protein in transcription. These findings have opened up a new avenue for studying an important regulatory step in virus gene expression that may lead to the development of an effective antiviral agent.

Phosphorylation of canine distemper virus P protein by protein kinase C-zeta and casein kinase II

Transcription by nonsegmented negative-strand RNA viruses is mediated by the viral RNA-dependent RNA polymerase and transcriptional cofactor P. The P protein is activated by phosphorylation, an event initiated by cellular kinases. The kinase used differs among this group of RNA viruses; vesicular stomatitis virus and respiratory syncytial virus utilize casein kinase II (CKII), whereas human parainfluenza virus type 3 utilizes PKC isoform zeta (PKC-zeta) for activation of its P protein. To identify the cellular kinase(s) involved in the phosphorylation of the canine distemper virus (CDV) P protein, we used recombinant CDV P in phosphorylation assays with native kinase activities present in CV1 cell extracts or purified CKII and PKC isoforms. Here, we demonstrate that the CDV P protein is phosphorylated by two cellular kinases, where PKC-zeta has the major and CKII the minor activities. In contrast, the P protein of another member of the morbillivirus genus, measles virus, is phosphorylated predominantly by CKII, whereas PKC-zeta has only minor activity. Selective inhibition of PKC-zeta activity within CV1 cells eliminated permissiveness to CDV replication, indicating an in vivo role for PKC-zeta in the virus replication cycle. The broad tissue expression of PKC-zeta parallels the pantropic nature of CDV infections, suggesting that PKC-zeta activity is a determinant of cellular permissiveness to CDV replication.

Major goat sperm 105 kDa maturation antigen: purification, characterization, and effect of its antiserum on acrosin activity

A ConA binding membrane glycoantigen of 105 kDa molecular mass was purified from mature goat sperm by ion exchange and gel filtration chromatography. Of the detergents examined, the anionic deoxycholate was found to be highly effective in maximum solubilization of this sperm membrane antigen (SMA2). The analysis of the saccharide components by gas liquid chromatography revealed that the 105 kDa antigen (SMA2) contained the highest amount of mannose, followed by galactose and glucose in a ratio of 4:3:1. One amino sugar, N-acetylglucosamine, was also found to be present in the polysaccharide branching of the SMA2 antigen. The internal sulfydryl linkage is essential for the maintenance of the protein backbone of 105 kDa antigen. The antigen selectively resides on the anterior head of goat sperm. The binding of anti-SMA2 antibody to the integrated mature goat spermatozoa inhibited the release of acrosin after the induction of spermatozoa with Ca-ionophore.

Phosphorylated states of vesicular stomatitis virus P protein in vitro and in vivo

We have previously shown that the phosphoprotein (P) of vesicular stomatitis virus (VSV), New Jersey serotype (PNJ) is phosphorylated by casein kinase II, within the N-terminal domain I (P1 form), whereas the C-terminal domain II is phosphorylated by a protein kinase activity associated with the L protein (P2 form) (D. J. Chattopadhyay and A.K. Banerjee, Cell 49, 407, 1987; A.M. Takacs et al., J. Virol. 66, 5842, 1992). In the present studies, we have mapped the corresponding P1 and P2 phosphorylation sites in the P protein of the well-studied Indiana serotype (PIND) and compared that with the two previously designated NS1 and NS2 forms present in vivo. The PIND expressed in Escherichia coli in an unphosphorylated form (P0) was used as substrate for recombinant casein kinase II (CKII). By site-directed mutagenesis, the CKII-mediated phosphorylation sites in the P protein were mapped at S60, T62, and S64 within the acidic domain I in vitro. In contrast, using BHK cell extract as the source of CKII or expressing P protein in COS cells labeled with 32PI, the phosphorylation sites were mapped at S60 and S64 with no phosphorylation at T62 residue. We used a peptide mapping technique by which the phosphorylation sites within domain I and domain II were determined. Using this method we demonstrated that the P1 and P2 forms are similar, if not identical, to the previously designated NS1 and NS2 forms, respectively. The domain II phosphorylating kinase activity, associated with the L protein, is shown to be present also in the N-RNA complex, indicating that this activity is of cellular origin. By site-directed mutagenesis, we have shown that S226 and S227 are involved in phosphorylation within domain II. We also demonstrate that the P1 and P2 forms are interconvertible and arise by phosphorylation/dephosphorylation of the phosphate groups in domain II, confirming the precursor-product relationship between the two phosphorylated forms of P protein.

Presumed noninfectious endophthalmitis after cataract surgery

PURPOSE

To study the clinical features and results of conservative management in cases of presumed noninfectious endophthalmitis after cataract surgery.

SETTING

L.V. Prasad Eye Institute, Hyderabad, India.

METHODS

This retrospective study evaluated cases of presumed noninfectious endophthalmitis occurring after cataract surgery in a hospital-based population. Patients with minimal hypopyon and decreased visual acuity unassociated with pain, lid edema, conjunctival chemosis, corneal abscess, and obvious vitreous involvement were treated conservatively. The mainstays of treatment were topical and systemic steroids. Four eyes with clinical evidence of worsening required surgical intervention. Main outcome measures were resolution of inflammation and final visual acuity.

RESULTS

In 23 of 27 patients, the inflammation resolved with medical therapy alone; 21 had a final visual acuity of 20/50 or better. In 3 of the 4 eyes that had surgery, the culture was positive for low virulent organisms; all had a satisfactory outcome. One eye with preoperative glaucoma developed absolute glaucoma with resolution of inflammation.

CONCLUSION

Noninfectious endophthalmitis invariably presents with hypopyon and decreased vision unassociated with pain and lid edema. A trial of medical therapy with corticosteroids as the mainstay of treatment is often rewarding. Frequent monitoring and preparation for surgical intervention if required are key.

Pneumatic retinopexy: principles and practice

Pneumatic retinopexy (PR) is an alternative to scleral buckling for the surgical repair of selected retinal detachments. A gas bubble is injected into the vitreous cavity, and the patient is positioned so that the bubble closes the retinal break (s), allowing absorption of the subretinal fluid. Cryotherapy or laser photocoagulation is applied around the retinal break(s) to form a permanent seal. The procedure can be done in an outpatient setting, and no incisions are required. A multicenter randomized controlled clinical trial has demonstrated that the anatomic success rate is comparable to scleral buckling, but the morbidity is significantly less with PR. If the macula was detached for less than two weeks, the visual results are significantly better with PR than with scleral buckling. Cataract surgery was required significantly more often following scleral buckling than following PR. Two independent reports have shown that an attempt with PR does not disadvantage the eye; such that the results of scleral buckling after failed PR are not significantly different than primary scleral buckling. A comprehensive review of the world literature on PR revealed 27 statistical series totaling 1,274 eyes. These combined series had a single-operation success rate of 80%, and 98% were cured with reoperations. Pneumatic retinopexy should be considered in cases without inferior or extensive retinal breaks and without significant proliferative vitreoretinopathy. The cost of buckling varies from 4 to 10 times that of PR.

Inhibition of human parainfluenza virus-3 replication by interferon and human MxA

We have investigated the IFN-mediated inhibition of human parainfluenza virus-3 (HPIV-3) replication in cultured human A549 cells. IFN-alpha inhibited the virus yield significantly with concomitant reduction of viral RNA accumulation by more than 90%. Further studies indicated that the inhibitory action of IFN was at the level of primary transcription of HPIV3 replication. Since the IFN-inducible protein, MxA, has been shown to inhibit virus replication in several RNA viruses, we examined the role of MxA in HPIV-3 replication using a stably transfected human glioblastoma cell line expressing MxA. In these cells HPIV-3 replication was decreased by more than 100-fold depending on the virus dosage used with concomitant inhibition of viral RNA synthesis by about 80%. However, the viral primary transcription was not affected in this MxA-producing cell line. In contrast, in the parental cell line IFN-mediated inhibition occurred at the primary transcription step of HPIV-3 replication. These data suggest that in addition to MxA, other IFN-inducible proteins are involved in the anti-HPIV-3 effect of IFN in both the cell lines used.

Expression of the human MxA protein is associated with hyperphosphorylation of VSV P protein in human neural Cells

Constitutive expression of the type I interferon-inducible human cytoplasmic MxA protein has been shown to interfere with primary transcription of vesicular stomatitis virus (VSV) in tissue culture cells. As phosphorylation of the VSV P protein has been linked to its ability to stimulate viral transcription, we analyzed the phosphorylation status of this protein in human brain cells (U-87) stably transfected with MxA. We observed a general increase in cellular kinase activity in the presence of MxA, affecting both cellular proteins and VSV P protein. Phosphorylation of the latter was up to threefold higher both in vivo and in vitro. In vitro phosphorylation of recombinant VSV P protein could be enhanced in MxA-negative cell extracts after exogenous addition of recombinant His-MxA. Biochemical evidence and phosphorylation of a mutant P protein lacking the recognized casein kinase II (CKII) sites suggested that hyperphosphorylation of VSV P protein was not due to a stimulation of CKII. We thus propose that expression of MxA in human brain cells is associated with the stimulation of a cellular kinase that is active in phosphorylating both cellular target proteins and VSV P protein.

Studies on the platelet alpha-adrenoceptor subtypes in diabetes mellitus

Studies on the platelet alpha-adrenoceptor subtypes were carried out in 19 subjects with treated diabetes mellitus and 15 normal age and sex-matched controls. By utilising selective antagonists, it was noted that all the normal human platelets exhibited the alpha-2 adrenoceptor. 7 diabetics (37%) expressed both the alpha-1 and alpha-2 adrenoceptors and diabetic complications along with hypertension were most common in this group. Another 7 diabetics (37%) expressed the alpha-2 receptor only and diabetic complications were minimum in this group. Interestingly, 5 diabetics (26%) did not express either the alpha-1 or alpha-2 receptor and these patients occupied an intermediate position with regard to diabetic complications. Thus, it was concluded that platelet alpha-1 adrenoceptors perhaps indicated a poor prognosis in diabetes mellitus, opening up future scope for work in this area.

Dietary garlic extract in modifying clastogenic effects of inorganic arsenic in mice: two-generation studies

Mice are fed by gavage crude garlic extract (100 mg/kg b.wt.) for 30 consecutive days. One set was administered sodium arsenite (0.1 mg/kg b.wt.) simultaneously. Another set was treated with sodium arsenite only. Mice given distilled water were kept as negative control. Exposed mice from each set were sacrificed and bone marrow preparations examined for chromosomal aberrations and damaged cells. Sodium arsenite is a strong clastogen and the effects were reduced to a significant level by prolonged administration of garlic extract. For F1 studies, exposed male mice were mated with exposed female mice, and the progeny examined. In the progeny, clastogenic effects of sodium arsenite persisted in a lower degree, indicating that the metal is able to cross the transplacental barrier. There was no statistically significant difference between the effect in progeny of parents only given sodium arsenite when given simultaneously for prolonged periods in the parents; however, the effect is meagre in the next generation.

Expression of L protein of vesicular stomatitis virus Indiana serotype from recombinant baculovirus in insect cells: requirement of a host factor(s) for its biological activity in vitro

The 241-kDa large (L) protein of vesicular stomatitis virus (VSV) Indiana serotype, a multifunctional catalytic subunit of the viral RNA polymerase, has been expressed in Spodoptera frugiperda cells infected with recombinant baculovirus BacPAK6-L containing the L gene under the control of a polyhedrin promoter. The recombinant L protein was biologically active and supported viral mRNA synthesis in vitro. When the expressed L protein was purified by phosphocellulose column chromatography, it eluted in two peaks, one at 0.4 M NaCl (peak I) and the second at 0.75 M NaCl (peak II). The L protein in peak I showed significant transcriptional activity in an in vitro transcription reconstitution experiment, whereas the L protein in peak II was inactive. Interestingly, the addition of cytoplasmic extract from uninfected Sf21 cells to peak II completely restored transcription in vitro, indicating the requirement of a host factor(s) for the activity of the L protein. This factor is relatively heat stable and is dissociable from the recombinant L protein. It is also present in BHK, COS, and HeLa cells in detectable levels. The role of the putative host protein(s) in the activation of the L protein is discussed.

A 50 KDa protein modulates guanine nucleotide binding of transglutaminase II

Regulation of cellular response is an important mechanism for controlling cellular functions. The transmembrane signaling of the hormone receptors is regulated by GTP-binding proteins (GTPases) and their associated proteins. Our previous studies demonstrated that the bifunctional GTP-binding protein, G alpha h (transglutaminase II), consistently copurified with an approximately 50 kDa protein (G Beta h) which is dissociated from G alpha h upon activation with GTP gamma S or AlF4-. Present immunological and biochemical studies on the regulation of the GTPase cycle of G alpha h, which involves the alpha 1-adrenoceptor and 50 KDa G beta h, reveal that the 50 kDa protein is indeed a G alpha h-associated protein and down regulates functions of G alpha h. Thus, polyclonal antibody against G Beta h coimmunoprecipitates GDP-bound G alpha h but not the GDP-AlF4--bound form. The GTP gamma S binding and GTPase activity of G alpha h are inhibited in a G beta h concentration dependent manner. Supporting this notion, G beta h accelerated GTP gamma S release from G alpha h and changes the affinity of G alpha h from GTP to GDP. Moreover, the ternary complex preparation exhibits TGase activity that is inhibited in the presence of the alpha 1-agonist and GTP. The GTP gamma S binding by the ternary complex, consisting of the alpha 1-agonist, the receptor, and Gh, is also inhibited by G beta h. The inhibition of GTP gamma S binding with the ternary complex requires a > or = 2.7-fold higher concentration of G beta h than the G alpha h alone, indicating that the receptor enhances the affinity of G alpha h for GTP. In addition, G beta h copurifies with an alpha 1-agonist, adrenoceptor, and G alpha h ternary complex, showing that the complex is a heterotetramer. Our data also suggest that G beta h does not directly interact with alpha 1-adrenoceptor. These findings clearly demonstrate that G alpha h associates with a novel protein which modulates the affinity of G alpha h for guanine nucleotides and that the GDP-bound Gh is the ground state for the counterpart activator, the alpha 1-adrenoceptor, in this signaling system.

Sensitivity and predictability of vitreous cytology, biopsy, and membrane filter culture in endophthalmitis

PURPOSE

Forty-seven consecutive patients with endophthalmitis were prospectively studied to: 1) compare the undiluted vitreous biopsy culture and membrane filter culture of vitrectomy cassette fluid; 2) determine the sensitivity and specificity of initial smear examinations in relation to final culture; and 3) characterize vitreous cytology in culture positive and negative endophthalmitis.

METHODS

Examinations included smears (Gram stains, Diff Quik [Bacto Laboratories Pvt. Ltd., Liverpool, Australia] and unstained) and aerobic/anaerobic culture of undiluted vitreous biopsy specimens and diluted vitreous collected in the cassette. The cassette fluid was passed through 5-microns polycarbonate filter for cytology and a 0.22-microns polyvinylidene difluoride millipore filter for culture.

RESULTS

By either method culture results were positive in 27 (57.4%) patients. Culture positive of the vitreous biopsy alone was 44.6% and cassette fluid alone was 49% (P > 0.05). In the initial smear examination the sensitivity and specificity of the Gram stain were 66.6% and 84.2%, respectively. comparatively, Diff Quik provided lower sensitivity and specificity at 40.7% and 80.9% respectively. Examination of wet film of vitreous samples did not provide any useful information. Although polymorphs were seen in large numbers in all cultures that yielded positive results on examination, they also were seen in 80% of the sterile samples. There was no significant difference in the quantity of macrophages observed in infected and noninfected samples.

CONCLUSIONS

Initial smear examination and cytology have limited roles in the diagnosis of infectious endophthalmitis. Obtaining cultures of both an undiluted vitreous biopsy sample and the vitrectomy cassette fluid has a significant advantage compared with culture of only one sample.

Effects of crude garlic extract on mouse chromosomes in vivo

Three concentrations (25, 50 and 100 mg/kg body weight) of fresh garlic (Allium sativum L.) were administered daily by gavage to Swiss albino mice for different durations up to 60 days. These concentrations had been observed to protect significantly against effects of known clastogens. The endpoints scored were frequencies of chromosomal aberrations and damaged cells induced in bone marrow preparations. These parameters were found to be directly dose dependent and after an initial enhancement at 7 days, were reduced following prolonged exposure for 30 and 60 days to the low level observed at 24 hr. Therefore, administration of a low concentration of garlic extract daily is suggested for at least 30 days to obtain the maximum benefit of the extract in protecting against the clastogenic effects of known genotoxicants.

Role of cellular casein kinase II in the function of the phosphoprotein (P) subunit of RNA polymerase of vesicular stomatitis virus

The phosphorylation of the P protein of vesicular stomatitis virus by cellular casein kinase II (CKII) is essential for its activity in viral transcription. Recent in vitro studies have demonstrated that CKII converts the inactive unphosphorylated form of P (P0) to an active phosphorylated form P1, after phosphorylation at two serine residues, Ser-59 and Ser-61. To gain insight into the role of CKII-mediated phosphorylation in the structure and function of the P protein, we have carried out circular dichroism (CD) and biochemical analyses of both P0 and P1. The results of CD analyses reveal that phosphorylation of P0 to P1 significantly increases the predicted alpha-helical structure of the P1 protein from 27 to 48%. The phosphorylation defective double serine mutant (P59/61), which is transcriptionally inactive, possesses a secondary structure similar to that of P0. P1, at a protein concentration of 50 micrograms/ml, elutes from a gel filtration column apparently as a dimer, whereas both P0 and the double serine mutant elute as a monomer at the same concentration. Interestingly, unlike wild-type P1 protein, the P mutants in which either Ser-59 or Ser-61 is altered to alanine required a high concentration of CKII for optimal phosphorylation. We demonstrate here that phosphorylation of either Ser-59 or Ser-61 is necessary and sufficient to transactivate L polymerase although alteration of one serine residue significantly decreases its affinity for CKII. We have also shown that P1 binds to the N-RNA template more efficiently than P0 and the formation of P1 is a prerequisite for the subsequent phosphorylation by L protein-associated kinase. In addition, mutant P59/61 acts as a transdominant negative mutant when used in a transcription reconstitution assay in the presence of wild-type P protein.

Postsurgical endophthalmitis: diagnosis and management

Infectious endophthalmitis following intraocular surgery is a complication that could cause severe visual loss or loss of the eye. The categorisation of the event that led to intraocular infection will help the clinician to predict the infectious agent and begin appropriate therapy. Most of the cases of postsurgical endophthalmitis are seen following cataract surgery. It is important for all ophthalmologists, irrespective of specialisation and areas of interest, to be familiar with the management of endophthalmitis. This review briefly describes the facets of clinical and laboratory diagnosis, pathology, and management. While the different viewpoints in the management of endophthalmitis are mentioned in appropriate places, more attention is paid to present a rational approach to the management of endophthalmitis.

Involvement of cellular casein kinase II in the phosphorylation of measles virus P protein: identification of phosphorylation sites

The phosphoprotein P gene of measles virus (Edmonston strain) has been cloned in the Escherichia coli expression vector pET-3a with a histidine tag at the C-terminal end. The expressed protein was soluble, unphosphorylated, and constituted 10 to 20% of total cellular protein. Recombinant P protein purified by Ni-affinity chromatography was found to be efficiently phosphorylated in vitro by recombinant casein kinase II (CKII) or by the CKII activity present in the uninfected cell extract. A comparison of phosphopeptide analyses between the in vivo- and the in vitro-32P-labeled P proteins revealed that both proteins share common phosphorylation sites. In an attempt to identify the exact site of the CKII-mediated phosphorylation, we altered specific serine residues located within the CKII consensus motif to alanine by site-directed mutagenesis. The results indicate that Ser 86, Ser 151, and Ser 180 located within the N-terminal half of the P protein are involved in the CKII-mediated phosphorylation of the P protein.

Casein kinase II is the P protein phosphorylating cellular kinase associated with the ribonucleoprotein complex of purified vesicular stomatitis virus

Protein kinase activities associated with a highly purified transcriptionally active ribonucleoprotein complex from the virions of vesicular stomatitis virus (VSV) were isolated and characterized. Based upon several biochemical and immunological criteria, the protein kinase activity, which phosphorylated the bacterially expressed unphosphorylated (Po) protein, was shown to be cellular casein kinase II (CKII). These studies included inhibition of the protein kinase by specific inhibitors, phosphorylation of mutant phosphoproteins (P), immunoprecipitation by CKII antibody and Western blot analyses, and finally its ability to activate Po to synthesize RNA in a transcription-reconstitution reaction. The P protein is phosphorylated intracellularly by cellular CKII. The present study demonstrates that VSV specifically packages CKII which remains strongly associated with the ribonucleoprotein complex during morphogenesis.

Effect of fatty acid binding proteins on developing human placental malate dehydrogenase activity

Role of fatty acid binding proteins (FABPs) in modulating inhibition of human placental malate dehydrogenase by palmitoyl-CoA and oleate has been studied. Activity of human placental cytosolic malate dehydrogenase is detected throughout the gestation, showing a peak at midgestation (20-25 weeks). Inhibition (50%) of the enzyme activity is obtained by 20 microM palmitoyl-CoA or 35 microM oleate. FABPs enhance the activity of malate dehydrogenase in absence of palmitoyl-CoA or oleate and also protect against palmitoyl-CoA or oleate inhibition. Such a modulatory effect of FABP may be due to the binding of long chain fatty acyl-CoA or fatty acid rather than a direct effect of FABPs on the enzyme.

Gh: a GTP-binding protein with transglutaminase activity and receptor signaling function

The alpha 1-adrenergic receptors activate a phospholipase C enzyme by coupling to members of the large molecular size (approximately 74 to 80 kilodaltons) G alpha h family of guanosine triphosphate (GTP)-binding proteins. Rat liver G alpha h is now shown to be a tissue transglutaminase type II (TGase II). The transglutaminase activity of rat liver TGase II expressed in COS-1 cells was inhibited by the nonhydrolyzable GTP analog guanosine 5'-O-(3-thiotriphosphate) or by alpha 1-adrenergic receptor activation. Rat liver TGase II also mediated alpha 1-adrenergic receptor stimulation of phospholipase C activity. Thus, G alpha h represents a new class of GTP-binding proteins that participate in receptor signaling and may be a component of a complex regulatory network in which receptor-stimulated GTP binding switches the function of G alpha h from transglutamination to receptor signaling.

Exogenous Helminthosporium endophthalmitis

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Selection of surgical technique for retinal detachment with coloboma of the choroid

Four eyes with rhegmatogenous retinal detachment and coloboma of the choroid were managed by conventional scleral buckling (one eye); scleral buckling combined with lensectomy, vitrectomy, and fluid-air exchange (two eyes); and vitrectomy, silicone oil injection without scleral buckling (one eye). Retinal break was seen within the coloboma in two eyes, at the periphery in one eye, and, both in the coloboma and periphery in one eye. At a follow-up of 15 months, the retina was found attached in all the patients. The success of these surgical procedures could be attributed to careful preoperative/intraoperative fundus examination and individualised surgical planning.

Evidence that the Gh protein is a signal mediator from alpha 1-adrenoceptor to a phospholipase C. I. Identification of alpha 1-adrenoceptor-coupled Gh family and purification of Gh7 from bovine heart

Our previous studies on alpha 1-adrenoceptor-mediated signaling suggested that Gh is a signal mediator. Gh consists of a 74-kDa GTP-binding alpha-subunit and a 50-kDa beta-subunit. Studies using the alpha 1-agonist-receptor-G-protein ternary complexes from various tissues and species revealed that the intensity (GTP-binding) of the [alpha-32P]GTP-labeled proteins resulting from activating the alpha 1-receptor was significantly attenuated by phentolamine. The molecular masses of GTP-binding proteins were 74 kDa in rat heart and liver, 77 kDa in dog heart, 78 kDa (Gh7 alpha) in bovine heart and liver, and 80 kDa in human heart. Supporting these observations, a specific antibody to Gh7 alpha not only recognized these GTP-binding proteins in the ternary complex preparations, but also co-immunoprecipitated alpha 1-adrenoceptors, indicating a tight association of these GTP-binding proteins with the alpha 1-adrenoceptor. These results also demonstrate that functional and structural similarities exist among these GTP-binding proteins. Additionally, one of the identified G-proteins (termed Gh7) was purified from bovine heart. Gh7 consisted of the 78-kDa GTP-binding protein and a 50-kDa protein.

Evidence that the Gh protein is a signal mediator from alpha 1-adrenoceptor to a phospholipase C. II. Purification and characterization of a Gh-coupled 69-kDa phospholipase C and reconstitution of alpha 1-adrenoceptor, Gh family, and phospholipase C

Our studies on the alpha 1-adrenoceptor signaling have demonstrated that the Gh family is a signal mediator. We report here that a 69-kDa phospholipase C (PLC) is the effector in this signal pathway. The enzyme was isolated by dissociating a Gh7-PLC complex which was induced in the bovine liver membranes incubating with (-)-epinephrine and GTP. The enzyme displayed a marked preference hydrolysis for phosphatidylinositol 4,5-bisphosphate over other phosphatidylinositides at micromolar calcium. Reconstitution of PLC with the alpha 1-adrenoceptor and Gh (Gh7) into phospholipid vesicles resulted in a lowered Ca2+ requirement for the substrate hydrolysis in the presence of guanosine 5'-3-O-(thio)triphosphate (GTP gamma S) when the receptor was activated with the alpha 1-agonist. The formation of inositol phosphate was hormone concentration dependent and reached maximal within 3 min which was faster than the formation in the presence of the alpha 1-antagonist. An Gh7 alpha antibody co-immunoprecipitated 80-85% of phospholipase C activity in the presence of GTP gamma S, but not in the presence of GDP or buffer, showing the association of PLC with the alpha-subunit of Gh family. Thus, our novel approaches to identify the effector involved in the alpha 1-adrenoceptor signaling, as well as the reconstitution studies, substantially demonstrate that the alpha 1-adrenoceptor-mediated transmembrane signaling involves the Gh family and a 69-kDa PLC.

Characterization and binding properties of human fetal lung fatty acid-binding proteins

When delipidated Mr > 10,000 cut-off human fetal lung cytosol was separated on gel filtration and ion-exchange chromatography on Auto-FPLC system, two fatty acid-binding proteins (FABPs) of pI 6.9 and pI 5.4 were purified to homogeneity. On Western blotting analysis with the anti-human fetal lung pI 6.9 FABP, these two proteins showed immunochemical cross reactivity with each other and with purified hepatic FABPs but not with cardiac or gut FABP. These two FABPs have identical molecular mass of 15.2 kDa, which is slightly higher than that of the hepatic proteins (14.2 kDa). Carbohydrate covalently linked to FABPs, that may substantially add to the molecular mass, was not detected in the purified protein preparations. Amino acid analysis revealed that both the proteins have same amino acid composition each containing one Trp residue that is lacking in hepatic FABP. Different isoforms of lung FABP exhibited different binding ability for their natural ligands. These proteins bind palmitoyl CoA with higher affinity than oleic acid. pI 6.9 FABP can more rapidly and efficiently transfer fatty acid than can pI 5.4 FABP from unilammelar liposomes. Thus these FABPs may play a critical role in fatty acid transport during human fetal lung development.

Mapping of interacting domains between the nucleocapsid protein and the phosphoprotein of vesicular stomatitis virus by using a two-hybrid system

Specific interaction between the nucleocapsid protein (N) and the phosphoprotein (P) of vesicular stomatitis virus (VSV), an important step in the life-cycle of the virus, was studied by using a two-hybrid system. Plasmids encoding P fused with the yeast GAL4 DNA-binding domain (pGALP) and N fused with the herpes simplex virus VP16 transactivating region (pVPN) were transfected into CHO cells along with a reporter plasmid encoding chloramphenicol acetyltransferase (CAT). The ability of N and P to associate in vivo was measured by activation of the CAT gene by the VP16 transactivating region. Transfection of plasmids pGALP and pVPN resulted in a high level of CAT activity, indicating that the N and P portions of the fusion proteins associated very strongly with each other. Progressive C-terminal deletions of the P protein revealed two regions that are important for association with the N protein: the N-terminal acidic domain and the C-terminal basic domain. Phosphorylation of P protein was not required for N-P association. Various deletions and mutations of the N protein revealed the C-terminal 5 amino acids (Val-Glu-Phe-Asp-Lys), in particular the amino acids Val-Glu-Phe, to be critical for N association with P. This two-hybrid system can be used in other viral systems to study the interaction between proteins involved in transcription and replication.

Aspergillus terreus postoperative endophthalmitis

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Guidelines for the management of rhegmatogenous retinal detachment

Current techniques of rhegmatogenous retinal detachment repair allow most detachments to be repaired successfully. The success of repair depends on a careful pre-operative examination and choice of an appropriate procedure. The surgery is usually tailored to individual needs. Improvements in surgical techniques coupled with a better understanding of the pathophysiology of rhegmatogenous retinal detachment continue to improve the anatomic and functional success of retinal detachment repair.

Expression of the vesicular stomatitis virus nucleocapsid protein gene in Escherichia coli: analysis of its biological activity in vitro

The nucleocapsid (N) protein genes of vesicular stomatitis virus, serotypes New Jersey and Indiana, were expressed in Escherichia coli BL21(DE3) transformed by the recombinant expression vector pET-3a containing N genes under the control of the T7 RNA polymerase promoter. Following induction with isopropylthiogalactopyranoside, the N protein was synthesized, representing 10 to 20% of total cellular protein. The N protein remained in a nonaggregated form in 1 M NaCl solution. The purified N protein was found to be biologically active as demonstrated by its encapsidation of preformed leader RNA as well as its synthesis of genome length RNA in an in vitro transcription-replication reaction. The availability of recombinant N protein in a sufficient amount would facilitate structure and function studies of this important viral protein.

Characterization of cardiac fatty-acid-binding protein from human placenta. Comparison with placenta hepatic types

When a 105,000 x g supernatant of human placenta was incubated with [1-14C]oleate and subjected to Sephadex G-75 gel filtration and HPLC, two fatty-acid-binding protein (FABP) peaks were obtained. One of these, when further purified by carboxymethyl-cellulose, gave one 15.3-kDa FABP with pI5.3. The other, when chromatographed on DEAE cellulose, separated into two 14.2-kDa FABP with pI6.9 and 5.4. Purity of the proteins was checked by SDS/PAGE. Molecular mass, pI, immunochemical properties and amino acid compositions all indicated that 15.3-kDa FABP was of the cardiac type, whereas both 14.2-kDa FABP were of the hepatic type. Cardiac FABP did not cross-react with hepatic proteins. When tested for the acceptor/donor properties of these FABP, hepatic types were found to be better candidates than cardiac in uptaking fatty acids from liposomes. Cardiac FABP, on the other hand, acted in a more efficient way as a donor, indicating a distinct role of these proteins in human placenta, which furnishes a multiorgan system for the developing fetus.

Modification of clastogenicity of three known clastogens by garlic extract in mice in vivo

The anticlastogenic activity of crude extract of garlic (Allium sativum L.) was studied in bone marrow cells of mice. Male laboratory-bred Swiss albino mice were given one of three concentrations of the freshly prepared extract (100 mg, 50 mg, and 25 mg/kg body weight) as a dietary supplement by gavage for 6 consecutive days. On the seventh day the mice were administered a single acute dose of two known clastogens, mitomycin C(1.5 mg/kg) and cyclophosphamide (25 mg/kg) or sodium arsenite (2.5 mg/kg), simultaneously with garlic extract. After 24 hr, chromosome preparations were made from the bone marrow cells. The endpoint studied were chromosomal aberrations and damaged cells. Garlic extract alone induced a low level of chromosomal damage. The clastogenicity of all three mutagens were reduced significantly in the animals which had been given garlic extract as dietary supplement. The extent of reduction was different for the three clastogens and may be attributed to the interaction with the different components of the extract.

Phosphorylation of specific serine residues within the acidic domain of the phosphoprotein of vesicular stomatitis virus regulates transcription in vitro

The phosphorylated state of the vesicular stomatitis virus phosphoprotein (P), an essential component of the virion-associated RNA polymerase complex, has been shown to be important for the transcriptional activity of the complex. Recent studies indicate that phosphorylation within the acidic domain of the P protein by cellular casein kinase II is necessary for its activity. In an attempt to identify the exact location of the cell kinase-mediated phosphorylation, we altered specific serine and threonine residues within the acidic domain of the New Jersey serotype of P protein by site-directed mutagenesis. The altered P proteins were then tested to determine what effect these mutations had on the phosphorylated state of the protein in vivo as well as its transcriptional activity in vitro. We report that serine residues 59 and 61 within the acidic domain of the P protein must be phosphorylated for it to be functionally active in a reconstituted transcription assay. These results demonstrate the importance of site-specific phosphorylation in the transcriptional activity of a negative-strand RNA viral phosphoprotein and the crucial role played by a cell protein kinase in this process.