Site-directed mutagenesis studies on the Drosophila octopamine/tyramine receptor

The cloned Drosophila octopamine/tyramine receptor can be coupled to second messenger pathways in an agonist-specific fashion by the endogenously occurring biogenic amines, octopamine and tyramine, when expressed in Chinese hamster ovary cells. We have mutated to alanine a range of receptor amino acids that could potentially form hydrogen bonds with the beta-hydroxyl group of octopamine based on homologies with alpha- and beta-adrenergic receptor subtypes. After stable expression of the mutant receptors in CHO cells we have compared the ability of octopamine and tyramine to displace [(3)H]yohimbine binding to membrane fractions from the mutant cell lines with their ability to modulate adenylyl cyclase activity in intact cells. The results suggest that none of the mutated amino acids residues, at least in isolation, are likely to be involved in interactions with the beta-hydroxyl group of the octopamine side chain. It is possible that amino acids not mutated in the present study are somehow involved in this interaction. Alternatively, it is also possible that the beta-hydroxyl group of the octopamine side chain is capable of interacting with more than one of the amino acids mutated in the present study.     

Synthesis, molecular modeling and biological evaluation of aza-proline and aza-pipecolic derivatives as FKBP12 ligands and their in vivo neuroprotective effects

Nonimmunosuppressant ligands, exemplified by GPI 1046 (1), for the peptidyl-prolyl isomerase FKBP12 have been found to unexpectedly possess powerful neuroprotective and neuroregenerative effects in vitro and in vivo. We have extensively explored the therapeutic utility of FKBP12 ligands based on analogues of proline and pipecolic acid. As part of our ongoing program to explore novel structural classes of FKBP12 ligands, we herein wish to report a new class of FKBP12 ligands containing aza-proline and aza-pipecolic acid analogues. Details of the synthetic studies, together with biological activity will be presented.     

Elimination of diaminopeptidase activity in Pichia pastoris for therapeutic protein production

Yeast are important production platforms for the generation of recombinant proteins. Nonetheless, their use has been restricted in the production of therapeutic proteins due to differences in their glycosylation profile with that of higher eukaryotes. The yeast strain Pichia pastoris is an industrially important organism. Recent advances in the glycoengineering of this strain offer the potential to produce therapeutic glycoproteins with sialylated human-like N- and O-linked glycans. However, like higher eukaryotes, yeast also express numerous proteases, many of which are either localized to the secretory pathway or pass through it en route to their final destination. As a consequence, nondesirable proteolysis of some recombinant proteins may occur, with the specific cleavage being dependent on the class of protease involved. Dipeptidyl aminopeptidases (DPP) are a class of proteolytic enzymes which remove a two-amino acid peptide from the N-terminus of a protein. In P. pastoris, two such enzymes have been identified, Ste13p and Dap2p. In the current report, we demonstrate that while the knockout of STE13 alone may protect certain proteins from N-terminal clipping, other proteins may require the double knockout of both STE13 and DAP2. As such, this understanding of DPP activity enhances the utility of the P. pastoris expression system, thus facilitating the production of recombinant therapeutic proteins with their intact native sequences.     

Effectiveness of quality improvement strategies for coordination of care to reduce use of health care services: a systematic review and meta-analysis

Background:

Frequent users of health care services are a relatively small group of patients who account for a disproportionately large amount of health care utilization. We conducted a meta-analysis of the effectiveness of interventions to improve the coordination of care to reduce health care utilization in this patient group.

Methods:

We searched MEDLINE, Embase and the Cochrane Library from inception until May 2014 for randomized clinical trials (RCTs) assessing quality improvement strategies for the coordination of care of frequent users of the health care system. Articles were screened, and data abstracted and appraised for quality by 2 reviewers, independently. Random effects meta-analyses were conducted.

Results:

We identified 36 RCTs and 14 companion reports (total 7494 patients). Significantly fewer patients in the intervention group than in the control group were admitted to hospital (relative risk [RR] 0.81, 95% confidence interval [CI] 0.72–0.91). In subgroup analyses, a similar effect was observed among patients with chronic medical conditions other than mental illness, but not among patients with mental illness. In addition, significantly fewer patients 65 years and older in the intervention group than in the control group visited emergency departments (RR 0.69, 95% CI 0.54–0.89).

Interpretation:

We found that quality improvement strategies for coordination of care reduced hospital admissions among patients with chronic conditions other than mental illness and reduced emergency department visits among older patients. Our results may help clinicians and policy-makers reduce utilization through the use of strategies that target the system (team changes, case management) and the patient (promotion of self-management).Frequent users of health care services represent a relatively small group of patients who account for a disproportionately large amount of health care utilization, including emergency department visits,^1,2 hospital admissions and clinic visits. These patients are often of low socioeconomic status,^3,4 have multiple medical, psychiatric and social disorders^5,6 and have a high mortality.⁷ Frequent use of the health care system contributes to longer wait times and affects the quality of care.^4,8Disproportionate use of health care services by a segment of the population has been identified as a challenge in many countries, including Canada.^9–12 To encourage less resource-intensive care for frequent users, many efforts have been implemented. Some of these interventions, for example, have been designed specifically to transition health care utilization away from the hospital to other settings, such as community-based clinics.¹³Much of the literature has focused on frequent users of emergency departments, with less focus on their use of the health care system in general. One systematic review identified a number of studies that assessed the effect of various interventions, including care coordination.¹⁴ The authors concluded that case management and multidisciplinary teams were likely effective interventions to reduce emergency department visits.Emergency department visits typically represent only a fraction of the cost burden on the health care system. There is a need to understand the impact of interventions aimed at reducing overall health care utilization, including hospital admissions. We conducted a systematic review and meta-analysis of the effectiveness of quality improvement strategies for care coordination for patients who are frequent users of the health care system.     

Primary hepatocytes from mice lacking cysteine dioxygenase show increased cysteine concentrations and higher rates of metabolism of cysteine to hydrogen sulfide and thiosulfate

The oxidation of cysteine in mammalian cells occurs by two routes: a highly regulated direct oxidation pathway in which the first step is catalyzed by cysteine dioxygenase (CDO) and by desulfhydration-oxidation pathways in which the sulfur is released in a reduced oxidation state. To assess the effect of a lack of CDO on production of hydrogen sulfide (H₂S) and thiosulfate (an intermediate in the oxidation of H₂S to sulfate) and to explore the roles of both cystathionine γ-lyase (CTH) and cystathionine β-synthase (CBS) in cysteine desulfhydration by liver, we investigated the metabolism of cysteine in hepatocytes isolated from Cdo1-null and wild-type mice. Hepatocytes from Cdo1-null mice produced more H₂S and thiosulfate than did hepatocytes from wild-type mice. The greater flux of cysteine through the cysteine desulfhydration reactions catalyzed by CTH and CBS in hepatocytes from Cdo1-null mice appeared to be the consequence of their higher cysteine levels, which were due to the lack of CDO and hence lack of catabolism of cysteine by the cysteinesulfinate-dependent pathways. Both CBS and CTH appeared to contribute substantially to cysteine desulfhydration, with estimates of 56 % by CBS and 44 % by CTH in hepatocytes from wild-type mice, and 63 % by CBS and 37 % by CTH in hepatocytes from Cdo1-null mice.     

Structural variants of yeast prions show conformer‐specific requirements for chaperone activity

Molecular chaperones monitor protein homeostasis and defend against the misfolding and aggregation of proteins that is associated with protein conformational disorders. In these diseases, a variety of different aggregate structures can form. These are called prion strains, or variants, in prion diseases, and cause variation in disease pathogenesis. Here, we use variants of the yeast prions [RNQ+] and [PSI+] to explore the interactions of chaperones with distinct aggregate structures. We found that prion variants show striking variation in their relationship with Hsp40s. Specifically, the yeast Hsp40 Sis1 and its human orthologue Hdj1 had differential capacities to process prion variants, suggesting that Hsp40 selectivity has likely changed through evolution. We further show that such selectivity involves different domains of Sis1, with some prion conformers having a greater dependence on particular Hsp40 domains. Moreover, [PSI+] variants were more sensitive to certain alterations in Hsp70 activity as compared to [RNQ+] variants. Collectively, our data indicate that distinct chaperone machinery is required, or has differential capacity, to process different aggregate structures. Elucidating the intricacies of chaperone‐client interactions, and how these are altered by particular client structures, will be crucial to understanding how this system can go awry in disease and contribute to pathological variation.