"Stapling" scFv for multispecific biotherapeutics of superior properties

Single-chain fragment variable (scFv) domains play an important role in antibody-based therapeutic modalities, such as bispecifics, multispecifics and chimeric antigen receptor T cells or natural killer cells. However, scFv domains exhibit lower stability and increased risk of aggregation due to transient dissociation ("breathing") and inter-molecular reassociation of the two domains (VL and VH). We designed a novel strategy, referred to as stapling, that introduces two disulfide bonds between the scFv linker and the two variable domains to minimize scFv breathing. We named the resulting molecules stapled scFv (spFv). Stapling increased thermal stability (Tm) by an average of 10°C. In multiple scFv/spFv multispecifics, the spFv molecules display significantly improved stability, minimal aggregation and superior product quality. These spFv multispecifics retain binding affinity and functionality. Our stapling design was compatible with all antibody variable regions we evaluated and may be widely applicable to stabilize scFv molecules for designing biotherapeutics with superior biophysical properties.

Characterization of the Pichia pastoris protein-O-mannosyltransferase gene family

The methylotrophic yeast, Pichiapastoris, is an important organism used for the production of therapeutic proteins. However, the presence of fungal-like glycans, either N-linked or O-linked, can elicit an immune response or enable the expressed protein to bind to mannose receptors, thus reducing their efficacy. Previously we have reported the elimination of β-linked glycans in this organism. In the current report we have focused on reducing the O-linked mannose content of proteins produced in P. pastoris, thereby reducing the potential to bind to mannose receptors. The initial step in the synthesis of O-linked glycans in P. pastoris is the transfer of mannose from dolichol-phosphomannose to a target protein in the yeast secretory pathway by members of the protein-O-mannosyltransferase (PMT) family. In this report we identify and characterize the members of the P. pastoris PMT family. Like Candida albicans, P. pastoris has five PMT genes. Based on sequence homology, these PMTs can be grouped into three sub-families, with both PMT1 and PMT2 sub-families possessing two members each (PMT1 and PMT5, and PMT2 and PMT6, respectively). The remaining sub-family, PMT4, has only one member (PMT4). Through gene knockouts we show that PMT1 and PMT2 each play a significant role in O-glycosylation. Both, by gene knockouts and the use of Pmt inhibitors we were able to significantly reduce not only the degree of O-mannosylation, but also the chain-length of these glycans. Taken together, this reduction of O-glycosylation represents an important step forward in developing the P. pastoris platform as a suitable system for the production of therapeutic glycoproteins.

Optimization of erythropoietin production with controlled glycosylation-PEGylated erythropoietin produced in glycoengineered Pichia pastoris

Pichia pastoris is a methylotropic yeast that has gained great importance as an organism for protein expression in recent years. Here, we report the expression of recombinant human erythropoietin (rhEPO) in glycoengineered P. pastoris. We show that glycosylation fidelity is maintained in fermentation volumes spanning six orders of magnitude and that the protein can be purified to high homogeneity. In order to increase the half-life of rhEPO, the purified protein was coupled to polyethylene glycol (PEG) and then compared to the currently marketed erythropoiesis stimulating agent, Aranesp(®) (darbepoetin). In in vitro cell proliferation assays the PEGylated protein was slightly, and the non-PEGylated protein was significantly more active than comparator. Pharmacodynamics as well as pharmacokinetic activity of PEGylated rhEPO in animals was comparable to that of Aranesp(®). Taken together, our results show that glycoengineered P. pastoris is a suitable production host for rhEPO, yielding an active biologic that is comparable to those produced in current mammalian host systems.

A novel fragment of antigen binding (Fab) surface display platform using glycoengineered Pichia pastoris

A fragment of antigen binding (Fab) surface display system was developed using a glycoengineered Pichia pastoris host strain genetically modified to secrete glycoproteins with mammalian mannose-type Man(5)GlcNAc(2) N-linked glycans. The surface display method described here takes advantage of a pair of coiled-coil peptides as the linker while using the Saccharomyces cerevisiae Sed1p GPI-anchored cell surface protein as an anchoring domain. Several Fabs were successfully displayed on the cell surface using this system and the expression level of the displayed Fabs was correlated to that of secreted Fabs from the same glycoengineered host in the absence of the cell wall anchor. Strains displaying different model Fabs were mixed and, through cell sorting, the strain displaying more expressed Fab molecule or the strain displaying the Fab with higher affinity for an antigen was effectively enriched by FACS. This novel yeast surface display system provides a general platform for the display of Fab libraries for affinity and/or expression maturation using glycoengineered Pichia.

Charge and current neutralization of an ion-beam pulse propagating in a background plasma along a solenoidal magnetic field

The analytical studies show that the application of a small solenoidal magnetic field can drastically change the self-magnetic and self-electric fields of the beam pulse propagating in a background plasma. Theory predicts that when omega_{ce} approximately omega_{pe}beta_{b}, where omega_{ce} is the electron gyrofrequency, omega_{pe} is the electron plasma frequency, and beta_{b} is the ion-beam velocity relative to the speed of light, there is a sizable enhancement of the self-electric and self-magnetic fields due to the dynamo effect. Furthermore, the combined ion-beam-plasma system acts as a paramagnetic medium; i.e., the solenoidal magnetic field inside the beam pulse is enhanced.

Humanization of yeast to produce complex terminally sialylated glycoproteins

Yeast is a widely used recombinant protein expression system. We expanded its utility by engineering the yeast Pichia pastoris to secrete human glycoproteins with fully complex terminally sialylated N-glycans. After the knockout of four genes to eliminate yeast-specific glycosylation, we introduced 14 heterologous genes, allowing us to replicate the sequential steps of human glycosylation. The reported cell lines produce complex glycoproteins with greater than 90% terminal sialylation. Finally, to demonstrate the utility of these yeast strains, functional recombinant erythropoietin was produced.

Drift compression of an intense neutralized ion beam

Longitudinal compression of a velocity-tailored, intense neutralized beam at 300 keV, 25 mA has been demonstrated. The compression takes place in a 1-2 m drift section filled with plasma to provide space-charge neutralization. An induction cell produces a head-to-tail velocity ramp that longitudinally compresses the neutralized beam, enhancing the beam peak current by a factor of 50 and producing a pulse duration of about 3 ns. This measurement has been confirmed independently with two different diagnostic systems.

Effects of eplerenone versus losartan in patients with low-renin hypertension

BACKGROUND

Sodium retention and volume expansion, mediated in part by aldosterone, are prominent features in low-renin hypertension. Agents that block aldosterone at its receptor sites, therefore, should have significant clinical benefit in patients with low-renin hypertension.

METHODS

This 16-week, multicenter, double-blind, active-controlled, parallel-group, titration-to-effect trial compared the blood pressure and neurohumoral responses of the selective aldosterone blocker eplerenone (100-200 mg/d; n = 86) with those of the angiotensin receptor blocker losartan (50-100 mg/d; n = 82) in patients with low-renin hypertension (active renin < or = 25 pg/mL [< or = 42.5 mU/L]). Patients with diastolic blood pressure > or = 90 mm Hg after 8 weeks of monotherapy received add-on therapy with hydrochlorothiazide 12.5 to 25 mg daily.

RESULTS

After 8 weeks of therapy, eplerenone reduced blood pressure to a greater extent than losartan (systolic blood pressure -15.8 vs -10.1 mm Hg, P = .017; diastolic blood pressure -9.3 vs -6.7 mm Hg, P = .05). After 16 weeks of therapy, significantly fewer eplerenone-treated patients (32.5%) than losartan-treated patients (55.6%) required add-on hydrochlorothiazide as allowed per protocol for blood pressure control (P = .003). Eplerenone consistently reduced blood pressure regardless of baseline active plasma renin levels whereas losartan reduced blood pressure more effectively in patients with higher baseline active renin levels. There were no differences between treatments in adverse events (reported by 62.8% of eplerenone patients and by 72.0% of losartan patients).

CONCLUSIONS

These data show that eplerenone was more effective than losartan in reducing blood pressure in patients with low-renin hypertension. Further studies evaluating the efficacy of eplerenone in difficult-to-treat or resistant hypertension are needed.

Intact α-1,2-endomannosidase is a typical type II membrane protein

Rat endomannosidase is a glycosidic enzyme that catalyzes the cleavage of di-, tri-, or tetrasaccharides (Glc(1-3)Man), from N-glycosylation intermediates with terminal glucose residues. To date it is the only characterized member of this class of endomannosidic enzymes. Although this protein has been demonstrated to localize to the Golgi lumenal membrane, the mechanism by which this occurs has not yet been determined. Using the rat endomannosidase sequence, we identified three homologs, one each in the human, mouse, and rat genomes. Alignment of the four encoded protein sequences demonstrated that the newly identified sequences are highly conserved but differed significantly at the N-terminus from the previously reported protein. In this study we have cloned two novel endomannosidase sequences from rat and human cDNA libraries, but were unable to amplify the open reading frame of the previously reported rat sequence. Analysis of the rat genome confirmed that the 59- and 39-termini of the previously reported sequence were in fact located on different chromosomes. This, in combination with our inability to amplify the previously reported sequence, indicated that the N-terminus of the rat endomannosidase sequence previously published was likely in error (a cloning artifact), and that the sequences reported in the current study encode the intact proteins. Furthermore, unlike the previous sequence, the three ORFs identified in this study encode proteins containing a single N-terminal transmembrane domain. Here we demonstrate that this region is responsible for Golgi localization and in doing so confirm that endomannosidase is a type II membrane protein, like the majority of other secretory pathway glycosylation enzymes.

Engineering of an artificial glycosylation pathway blocked in core oligosaccharide assembly in the yeast Pichia pastoris: production of complex humanized glycoproteins with terminal galactose

A significant percentage of eukaryotic proteins contain posttranslational modifications, including glycosylation, which are required for biological function. However, the understanding of the structure-function relationships of N-glycans has lagged significantly due to the microheterogeneity of glycosylation in mammalian produced proteins. Recently we reported on the cellular engineering of yeast to replicate human N-glycosylation for the production of glycoproteins. Here we report the engineering of an artificial glycosylation pathway in Pichia pastoris blocked in dolichol oligosaccharide assembly. The PpALG3 gene encoding Dol-P-Man:Man(5)GlcNAc(2)-PP-Dol mannosyltransferase was deleted in a strain that was previously engineered to produce hybrid GlcNAcMan(5)GlcNAc(2) human N-glycans. Employing this approach, combined with the use of combinatorial genetic libraries, we engineered P. pastoris strains that synthesize complex GlcNAc(2)Man(3)GlcNAc(2) N-glycans with striking homogeneity. Furthermore, through expression of a Golgi-localized fusion protein comprising UDP-glucose 4-epimerase and beta-1,4-galactosyl transferase activities we demonstrate that this structure is a substrate for highly efficient in vivo galactose addition. Taken together, these data demonstrate that the artificial in vivo glycoengineering of yeast represents a major advance in the production of glycoproteins and will emerge as a practical tool to systematically elucidate the structure-function relationship of N-glycans.

Functional analysis of the ALG3 gene encoding the Dol-P-Man: Man5GlcNAc2-PP-Dol mannosyltransferase enzyme of P. pastoris

N-glycans are synthesized in both yeast and mammals through the ordered assembly of a lipid-linked core Glc(3)Man(9)GlcNAc(2) structure that is subsequently transferred to a nascent protein in the endoplasmic reticulum. Once folded, glycoproteins are then shuttled to the Golgi, where additional but divergent processing occurs in mammals and fungi. We cloned the Pichia pastoris homolog of the ALG3 gene, which encodes the enzyme that converts Man(5)GlcNAc(2)-Dol-PP to Man(6)GlcNAc(2)-Dol-PP. Deletion of this gene in an och1 mutant background resulted in the secretion of glycoproteins with a predicted Man(5)GlcNAc(2) structure that could be trimmed to Man(3)GlcNAc(2) by in vitro alpha-1,2-mannosidase treatment. However, several larger glycans ranging from Hex(6)GlcNAc(2) to Hex(12)GlcNAc(2) were also observed that were recalcitrant to an array of mannosidase digests. These results contrast the far simpler glycan profile found in Saccharomyces cerevisiae alg3-1 och1, indicating diverging Golgi processing in these two closely related yeasts. Finally, analysis of the P. pastoris alg3 deletion mutant in the presence and absence of the outer chain initiating Och1p alpha-1,6-mannosyltransferase activity suggests that the PpOch1p has a broader substrate specificity compared to its S. cerevisiae counterpart.

Production of complex human glycoproteins in yeast

We report the humanization of the glycosylation pathway in the yeast Pichia pastoris to secrete a human glycoprotein with uniform complex N-glycosylation. The process involved eliminating endogenous yeast glycosylation pathways, while properly localizing five active eukaryotic proteins, including mannosidases I and II, N-acetylglucosaminyl transferases I and II, and uridine 5'-diphosphate (UDP)-N-acetylglucosamine transporter. Targeted localization of the enzymes enabled the generation of a synthetic in vivo glycosylation pathway, which produced the complex human N-glycan N-acetylglucosamine2-mannose3-N-acetylglucosamine2 (GlcNAc2Man3GlcNAc2). The ability to generate human glycoproteins with homogeneous N-glycan structures in a fungal host is a step toward producing therapeutic glycoproteins and could become a tool for elucidating the structure-function relation of glycoproteins.

A MAP kinase cascade composed of cell type specific and non-specific elements controls mating and differentiation of the fungal pathogen Cryptococcus neoformans

Cryptococcus neoformans is an opportunistic fungal pathogen with a defined sexual cycle in which the alpha allele of the mating type locus is linked to virulence and haploid differentiation. Here we analysed a conserved MAP kinase cascade composed of mating-type specific (Ste11alpha, Ste12alpha) and non-specific (Ste7, Cpk1) elements. Gene disruption experiments demonstrate that this specialized MAP kinase pathway is required for both mating and cell type-specific differentiation but not for virulence. The Ste11alpha, Ste7 and Cpk1 kinases were found to act as a co-ordinate signalling module, whereas the Ste12alpha transcription factor functions with a redundant partner or in a branched or parallel signalling pathway. Our studies illustrate how MAP kinase cascades can be constructed from cell type-specific and non-specific components, yielding pathways that contribute to cell type-specific patterns of signalling and differentiation.

Use of combinatorial genetic libraries to humanize N-linked glycosylation in the yeast Pichia pastoris

The secretory pathway of Pichia pastoris was genetically re-engineered to perform sequential glycosylation reactions that mimic early processing of N-glycans in humans and other higher mammals. After eliminating nonhuman glycosylation by deleting the initiating alpha-1,6-mannosyltransferase gene from P. pastoris, several combinatorial genetic libraries were constructed to localize active alpha-1,2-mannosidase and human beta-1,2-N-acetylglucosaminyltransferase I (GnTI) in the secretory pathway. First, >32 N-terminal leader sequences of fungal type II membrane proteins were cloned to generate a leader library. Two additional libraries encoding catalytic domains of alpha-1,2-mannosidases and GnTI from mammals, insects, amphibians, worms, and fungi were cloned to generate catalytic domain libraries. In-frame fusions of the respective leader and catalytic domain libraries resulted in several hundred chimeric fusions of fungal targeting domains and catalytic domains. Although the majority of strains transformed with the mannosidase/leader library displayed only modest in vivo [i.e., low levels of mannose (Man)(5)-(GlcNAc)(2)] activity, we were able to isolate several yeast strains that produce almost homogeneous N-glycans of the (Man)(5)-(GlcNAc)(2) type. Transformation of these strains with a UDP-GlcNAc transporter and screening of a GnTI leader fusion library allowed for the isolation of strains that produce GlcNAc-(Man)(5)-(GlcNAc)(2) in high yield. Recombinant expression of a human reporter protein in these engineered strains led to the formation of a glycoprotein with GlcNAc-(Man)(5)-(GlcNAc)(2) as the primary N-glycan. Here we report a yeast able to synthesize hybrid glycans in high yield and open the door for engineering yeast to perform complex human-like glycosylation.

Cell identity and sexual development in Cryptococcus neoformans are controlled by the mating-type-specific homeodomain protein Sxi1alpha

Virulence in the human fungal pathogen Cryptococcus neoformans is associated with the alpha mating type. Studies to identify the properties of alpha cells that enhance pathogenesis have led to the identification of a mating-type locus of unusually large size and distinct architecture. Here, we demonstrate that the previously identified MATalpha components are insufficient to regulate sexual differentiation, and we identify a novel alpha-specific regulator, SXI1alpha. Our data show that SXI1alpha establishes alpha cell identity and controls progression through the sexual cycle, and we discover that ectopic expression of SXI1alpha in a cells is sufficient to drive a/alpha sexual development. SXI1alpha is the first example of a key regulator of cell identity and sexual differentiation in C. neoformans, and its identification and characterization lead to a new model of how cell fate and the sexual cycle are controlled in C. neoformans.

A PCR-based strategy to generate integrative targeting alleles with large regions of homology

Cryptococcus neoformans is an opportunistic fungal pathogen with a defined sexual cycle for which genetic and molecular techniques are well developed. The entire genome sequence of one C. neoformans strain is nearing completion. The efficient use of this sequence is dependent upon the development of methods to perform more rapid genetic analysis including gene-disruption techniques. A modified PCR overlap technique to generate targeting constructs for gene disruption that contain large regions of gene homology is described. This technique was used to disrupt or delete more than a dozen genes with efficiencies comparable to those previously reported using cloning technology to generate targeting constructs. Moreover, it is shown that disruptions can be made using this technique in a variety of strain backgrounds, including the pathogenic serotype A isolate H99 and recently characterized stable diploid strains. In combination with the availability of the complete genomic sequence, this gene-disruption technique should pave the way for higher throughput genetic analysis of this important pathogenic fungus.

Pheromones stimulate mating and differentiation via paracrine and autocrine signaling in Cryptococcus neoformans

Cryptococcus neoformans is a pathogenic fungus with a defined sexual cycle involving haploid MATalpha and MATa cells. Interestingly, MATalpha strains are more common, are more virulent than congenic MATa strains, and undergo haploid fruiting in response to nitrogen limitation or MATa cells. Three genes encoding the MFalpha pheromone were identified in the MATalpha mating-type locus and shown to be transcriptionally induced by limiting nutrients and coculture with MATa cells. The MFalpha1, MFalpha2, and MFalpha3 genes were mutated, individually and in combination. MATalpha strains lacking MFalpha pheromone failed to induce morphological changes in MATa cells. Pheromoneless MATalpha mutants were fusion and mating impaired but not sterile and mated at approximately 1% the wild-type level. The pheromoneless MATalpha mutants were also partially defective in haploid fruiting, and overexpression of MFalpha pheromone enhanced haploid fruiting. Overexpression of MFa pheromone also enhanced haploid fruiting of MATalpha cells and stimulated conjugation tube formation in MATa cells. A conserved G-protein activated mitogen-activated protein kinase signaling pathway was found to be required for both induction and response to mating pheromones. The MFalpha pheromone was not essential for virulence of C. neoformans but does contribute to the overall virulence composite. These studies define paracrine and autocrine pheromone response pathways that signal mating and differentiation of this pathogenic fungus.

Screening for primary aldosteronism without discontinuing hypertensive medications: plasma aldosterone-renin ratio

The traditional workup for primary aldosteronism is cumbersome and requires discontinuing antihypertensive medications, which is inconvenient and potentially dangerous. A simple and accurate screening test that can be used without modifying medications is needed. The plasma aldosterone-renin ratio (ARR) is a valid screening assay for primary aldosteronism, but antihypertensives are usually discontinued before obtaining this ratio, limiting its utility. The present prospective study is designed to examine the validity of the ARR as a screening test for primary aldosteronism if the ratio is measured randomly while patients continue antihypertensive therapy. During the 18-month study period, 90 patients were referred to the hypertension clinic with poorly controlled hypertension. ARR was measured in random blood samples in all 90 patients while maintaining their prescribed antihypertensive medications. Those with elevated ARRs (>100 ng/dL / ng/mL/h) underwent further diagnostic workup, including adrenal computed tomography and/or magnetic resonance imaging and adrenal iodine 131 norcholesterol uptake scan. Fifteen patients (17%) had elevated ARRs greater than 100:1. Ten of 15 patients were found to have adrenal adenoma on diagnostic workup, and adenoma was later confirmed by histological examination after surgical removal in these 10 patients. Five patients were found to have adrenal hyperplasia; all 5 patients responded to antialdosterone treatment. Thus, all 15 patients had good control of blood pressure after surgery and/or antialdosterone medications. No patient showed a falsely elevated ARR. Data suggest that the ARR is a valid screening assay for primary aldosteronism in patients with poorly controlled blood pressure, and discontinuation of antihypertensive medications is not needed for this test.

Clinical and duplex ultrasound follow-up after balloon angioplasty for atherosclerotic renal artery stenosis

The purpose of this study was to investigate changes in blood pressure and renal function after percutaneous renal artery balloon angioplasty in hypertensive patients with atherosclerotic renal artery stenosis. Renal artery lesions were assessed by duplex ultrasound before and after renal artery balloon angioplasty. Renal arteries were classified as normal, < 60% stenosis, > or =60% stenosis, and occluded according to previously validated duplex criteria. Data regarding risk factors for atherosclerosis and years of hypertension were collected. Systolic and diastolic blood pressure, creatinine, and number of medications were obtained before and after intervention. The immediate technical outcome of renal artery angioplasty was classified based on the arteriographic result as follows: success (residual stenosis < or =30%), partial success (residual stenosis 31-50%), or unsuccessful (residual stenosis > 50%). For bilateral procedures, success required both renal arteries to be classified as technical successes; a technical success on one side only was classified as partial success. The blood pressure response to intervention was classified as follows: cure (diastolic blood pressure < or =95 mm Hg on no medications), improved (control of blood pressure with a significant reduction in number of medications or control of previously elevated blood pressure without a change in medications), or failed (all other responses). The study group included 28 patients (14 men, 14 women) with a mean age of 65 years. The preintervention and the first postintervention evaluations occurred within 180 days of the procedure. All patients were hypertensive, and all except one were under medical treatment. Mean duration of hypertension was 9.1 +/-8.8 years. There were 38 interventional procedures (28 unilateral, 10 bilateral) involving 41 renal arteries; seven arteries had two procedures done. Before angioplasty, all renal arteries had lesions of > or =60% diameter reduction by duplex scanning. Endovascular stents were deployed following angioplasty in 14 (34%) of the procedures. The technical result was classified as a success in 24 (63%), a partial success in 12 (32%) of the procedures, and two procedures (5%) were classed as technical failures. There were statistically significant reductions in blood pressure following successful and partially successful procedures, but cure of hypertension was achieved in only 11% of cases. There were no significant changes in creatinine in any of the technical result groups. Of the 38 renal arteries evaluated with duplex ultrasound following intervention, 39% were found to have stenosis of > or =0% involving a treated renal artery, including one postintervention occlusion. Cure of hypertension was rare in this patient population with atherosclerotic renal artery stenosis. More than one third of the treated renal arteries showed > or =0% lesions recurring after the procedure. Thirteen percent of those with technical success and 17% of those with partial technical success had creatinine improvement of at least 20% over the baseline value. Significant clinical and anatomic improvement were relatively uncommon following balloon angioplasty in this series of patients.

Signal transduction cascades regulating fungal development and virulence

Cellular differentiation, mating, and filamentous growth are regulated in many fungi by environmental and nutritional signals. For example, in response to nitrogen limitation, diploid cells of the yeast Saccharomyces cerevisiae undergo a dimorphic transition to filamentous growth referred to as pseudohyphal differentiation. Yeast filamentous growth is regulated, in part, by two conserved signal transduction cascades: a mitogen-activated protein kinase cascade and a G-protein regulated cyclic AMP signaling pathway. Related signaling cascades play an analogous role in regulating mating and virulence in the plant fungal pathogen Ustilago maydis and the human fungal pathogens Cryptococcus neoformans and Candida albicans. We review here studies on the signaling cascades that regulate development of these and other fungi. This analysis illustrates both how the model yeast S. cerevisiae can serve as a paradigm for signaling in other organisms and also how studies in other fungi provide insights into conserved signaling pathways that operate in many divergent organisms.

Signal transduction cascades regulating fungal development and virulence

Cellular differentiation, mating, and filamentous growth are regulated in many fungi by environmental and nutritional signals. For example, in response to nitrogen limitation, diploid cells of the yeast Saccharomyces cerevisiae undergo a dimorphic transition to filamentous growth referred to as pseudohyphal differentiation. Yeast filamentous growth is regulated, in part, by two conserved signal transduction cascades: a mitogen-activated protein kinase cascade and a G-protein regulated cyclic AMP signaling pathway. Related signaling cascades play an analogous role in regulating mating and virulence in the plant fungal pathogen Ustilago maydis and the human fungal pathogens Cryptococcus neoformans and Candida albicans. We review here studies on the signaling cascades that regulate development of these and other fungi. This analysis illustrates both how the model yeast S. cerevisiae can serve as a paradigm for signaling in other organisms and also how studies in other fungi provide insights into conserved signaling pathways that operate in many divergent organisms.

Characterization of the MFalpha pheromone of the human fungal pathogen cryptococcus neoformans

Cryptococcus neoformans is an important human pathogenic fungus with a defined sexual cycle and well-developed molecular and genetic approaches. C. neoformans is predominantly haploid and has two mating types, MATa and MATalpha. Mating is known to be regulated by nutritional limitation and thought also to be regulated by pheromones. Previously, a portion of the MATalpha locus was cloned, and a presumptive pheromone gene, MFalpha1, was identified by its ability to induce conjugation tube-like filaments when introduced by transformation into MATa cells. Here, the ability of the MFalpha1 gene to induce these morphological changes in MATa cells was used as a phenotypic assay to perform a structure-function analysis of the gene. We show that the MFalpha1 open reading frame is required for the morphological response of MATa cells. We also find that the cysteine residue of the C-terminal CAAX motif is required for activity of the MFalpha1 pheromone. In addition, we use a reporter system to measure the expression levels of the MFalpha1 pheromone gene and find that two signals, nutrient starvation and the presence of factors secreted by mating partner cells, impinge on this promoter and regulate MFalpha1 expression. We identify a second pheromone gene, MFalpha2, and show phenotypically that this gene is also expressed. Finally, we have synthesized the MFalpha1 pheromone and show that only the predicted mature modified form of the alpha-factor peptide triggers morphological responses in MATa cells.

Production of halo particles by excitation of collective modes in high-intensity charged particle beams

This paper examines analytically and numerically the effects of self-consistent collective oscillations excited in a high-intensity charged particle beam on the motion of a test particle in the beam core. Even under ideal conditions, assuming a constant transverse focusing force (smooth focusing approximation), and perturbations about a uniform-density, constant radius beam, it is found that collective mode excitations, in combination with the applied focusing force and the equilibrium test fields, can eject particles from the beam core to large radii. Test particle orbits are calculated for collective oscillations with n = 1 and 2 radial mode structure, and an estimate is obtained for the range of initial conditions for which particles will be expelled from the beam interior. Resonances for meridional particles are found to be unimportant, while a class of particles with nonzero angular momentum are found to participate in resonant behavior. Once expelled from the beam, numerical solutions of the orbit equations indicate that Kolmogorov-Arnold-Moser curves, phase space spanning integrals of motion, confine particles within 1.5 times the beam radius for moderately low mode amplitudes, but are successively destabilized for higher amplitudes.

Gene disruption by biolistic transformation in serotype D strains of Cryptococcus neoformans

Gene disruption by biolistic transformation in serotype D strains of Cryptococcus neoformans. Fungal Genetics and Biology 29, 38-48. Cryptococcus neoformans is an opportunistic fungal pathogen with a defined sexual cycle and well-developed genetic and molecular approaches. Two different transformation systems have been developed, and a number of genes have been disrupted by homologous recombination. However, the frequency of homologous recombination achieved by these approaches has differed dramatically between strains of the A and D serotypes. Transformation by electroporation in serotype D strains results in homologous recombination at frequencies of 1/1000 to 1/100,000, whereas transformation by the biolistic method has resulted in gene disruption at frequencies between 2 and 50% in serotype A strains. We find that gene disruption by homologous recombination can be achieved in the congenic serotype D strain series by biolistic transformation with frequencies of approximately 1 to 4%. By this approach, we have readily disrupted the genes encoding a MAPK homolog (CPK1), the calcineurin A catalytic subunit (CNA1), and a G protein alpha subunit (GPA1). By physical and genetic methods, we show that these mutations result from targeted recombination events without ectopic integrations. Because genetic approaches can be applied in the congenic serotype D strains, our observations represent a significant advance in molecular approaches to understand the physiology and virulence of this important human pathogen.

Molecular analysis of the Cryptococcus neoformans ADE2 gene, a selectable marker for transformation and gene disruption

Cryptococcus neoformans is an important fungal pathogen of man. The incidence of cryptococcal disease has increased dramatically in patients immunocompromised because of HIV infection, organ transplantation, or treatment with cytotoxic chemotherapy or corticosteroids. This organism is an excellent model for molecular dissection of fungal pathogenesis and virulence factors. Here we report the nucleotide sequence of the C. neoformans serotype D genomic ADE2 gene, which encodes a phosphoribosylaminoimidazole carboxylase required for purine biosynthesis. Importantly, this version of the ADE2 gene has been used as the selectable marker for virtually all gene disruptions by transformation and homologous recombination in C. neoformans. We compare the nucleotide and amino acid sequences of the ADE2 gene and product to other highly related adenine biosynthetic genes and enzymes from other yeasts and fungi. We also describe a series of convenient ADE2 cassettes for gene disruption construct preparation. Finally, we have identified the ade2 mutations in strains M001 and M049, adenine auxotrophic mutants derived from the serotype A strain H99. These mutant strains have served as recipients for targeted gene disruptions using the ADE2 gene. These studies should facilitate transformation and gene disruption approaches using the ADE2 selectable marker in this important human fungal pathogen.

Blood pressure, antihypertensive medication, and atherosclerotic renal artery stenosis

The relationship between atherosclerotic renal artery stenosis (ARAS) and blood pressure control remains poorly understood. Duplex ultrasonography is a noninvasive method for detecting and grading ARAS. The purpose of this study was to characterize the relationship between the degree of ARAS, levels of blood pressure, and control of blood pressure with antihypertensive medication. A cross-sectional analysis was performed on 139 patients with ARAS. All patients had at least one diseased renal artery by duplex ultrasound. Renal arteries were classified as normal, less than 60% stenosis, or 60% or greater (high-grade) stenosis. Data regarding blood pressure, coexisting risk factors, and medications were collected. The extent of ARAS was significantly associated with progressive elevation of the systolic blood pressure, whereas the diastolic component was elevated in the case of unilateral high-grade stenosis: no high-grade stenoses, 153 +/- 22/81 +/- 10 mm Hg; unilateral high-grade stenosis, 162 +/- 22/86 +/- 9 mm Hg; and bilateral high-grade stenoses, 174 +/- 27/82 +/- 9 mm Hg (P = 0.002 systolic; P = 0.02 diastolic). Eighty-two percent of the patients were taking known antihypertensive medications. Angiotensin-converting enzyme inhibitor (ACEI) usage versus nonusage was associated with a significantly lower systolic (157 +/- 27 v 169 +/- 22 mm Hg; P = 0.03) and diastolic (79 +/- 9 v 85 +/- 9 mm Hg; P = 0.001) blood pressure. The effect of ACEI usage was observed in patients with high-grade ARAS. None of the other classes of antihypertensive medications were associated with significantly lower blood pressure. In patients with ARAS, blood pressure levels were correlated with the severity of renal artery disease. Patients taking ACEIs had significantly lower blood pressures, and the effect of ACEI usage was strongest among patients with unilateral ARAS.

Prospective study of atherosclerotic disease progression in the renal artery

BACKGROUND

The aim of this study was to determine the incidence of and the risk factors associated with progression of renal artery disease in individuals with atherosclerotic renal artery stenosis (ARAS).

METHODS AND RESULTS

Subjects with >/=1 ARAS were monitored with serial renal artery duplex scans. A total of 295 kidneys in 170 patients were monitored for a mean of 33 months. Overall, the cumulative incidence of ARAS progression was 35% at 3 years and 51% at 5 years. The 3-year cumulative incidence of renal artery disease progression stratified by baseline disease classification was 18%, 28%, and 49% for renal arteries initially classified as normal, <60% stenosis, and >/=60% stenosis, respectively (P=0.03, log-rank test). There were only 9 renal artery occlusions during the study, all of which occurred in renal arteries having >/=60% stenosis at the examination before the detection of occlusion. A stepwise Cox proportional hazards model included 4 baseline factors that were significantly associated with the risk of renal artery disease progression during follow-up: systolic blood pressure >/=160 mm Hg (relative risk [RR]=2.1; 95% CI, 1.2 to 3.5), diabetes mellitus (RR=2.0; 95% CI, 1.2 to 3.3), and high-grade (>60% stenosis or occlusion) disease in either the ipsilateral (RR=1.9; 95% CI, 1.2 to 3.0) or contralateral (RR=1.7; 95% CI, 1.0 to 2.8) renal artery.

CONCLUSIONS

Although renal artery disease progression is a frequent occurrence, progression to total renal artery occlusion is not. The risk of renal artery disease progression is highest among individuals with preexisting high-grade stenosis in either renal artery, elevated systolic blood pressure, and diabetes mellitus.

Carotid and lower extremity arterial disease in patients with renal artery atherosclerosis

BACKGROUND

Atherosclerotic lesions of the carotid and lower extremity arteries may be associated with renal artery stenosis and influence the management of patients with renal artery disease.

OBJECTIVE

To document the prevalence and clinical features of carotid and lower extremity arterial disease in patients with renal artery atherosclerosis.

METHODS

An analysis of baseline data on 149 patients enrolled in a prospective natural history study of atherosclerotic renal artery stenosis. Patients with at least 1 abnormal renal artery by duplex scanning were eligible. Carotid artery disease was evaluated by duplex scanning, and ankle/brachial indices were used to assess the lower extremity arteries. Disease at each of the 3 arterial sites was classified as mild, moderate, or severe based on the extent of involvement on both sides. Serum urea nitrogen, creatinine, and lipid levels were also measured.

RESULTS

Severe renal, carotid, or lower extremity arterial disease was present in 44%, 19%, and 21% of the patients, respectively. There was a trend for patients with increasing degrees of renal artery disease to have increasing degrees of carotid and lower extremity arterial disease. The prevalence of severe carotid artery disease increased from 7% in the mild renal artery group to 28% in the severe renal artery group. Clinical factors that were most predictive of severe disease were elevated apolipoprotein B levels for the renal arteries, high serum urea nitrogen or creatinine levels for the carotid arteries, and smoking for the lower extremity arteries.

CONCLUSIONS

There was a strong association between severe renal artery atherosclerosis and severe carotid artery disease. Patients with renal artery disease also had a high prevalence of lower extremity arterial disease. In this patient population, screening for lower extremity arterial disease can be reserved for those with signs or symptoms of peripheral ischemia. Noninvasive carotid screening is justified in patients with renal artery disease to detect asymptomatic lesions that require either immediate surgical treatment or serial follow-up for disease progression.

Risk of atrophy in kidneys with atherosclerotic renal artery stenosis

The goal of this study was to determine the incidence of and risk factors for renal atrophy among kidneys with atherosclerotic renal artery stenosis (ARAS). Participants with at least one ARAS were followed prospectively with duplex scans performed every six months. Renal atrophy was defined as a reduction in renal length of greater than 1 cm. A total of 204 kidneys in 122 subjects were followed for a mean of 33 months. The two-year cumulative incidence (CI) of renal atrophy was 5.5%, 11.7%, and 20.8% in kidneys with a baseline renal artery disease classification of normal, <60% stenosis, and > or = 60% stenosis, respectively (P = 0.009, log rank test). Other baseline factors associated with a high risk of renal atrophy included a systolic blood pressure > 180 mm Hg (2-year CL = 35%, P = 0.01), a renal artery peak systolic velocity > 400 cm/second (2-year CI = 32%, P = 0.02), and a renal cortical end diastolic velocity < or = 5 cm/second (2-year CI = 29%, P = 0.046). The number of kidneys demonstrating atrophy per participant was correlated with elevations in the serum creatinine concentration (P = 0.03). In patients with ARAS, there is a significant risk of renal atrophy among kidneys exposed to elevated systolic blood pressure and among those with high-grade ARAS and low renal cortical blood flow velocity as assessed by renal duplex scanning. The occurrence of renal atrophy is well-correlated with changes in the serum creatinine concentration.