Improved Purification of Human Granzyme A/B and Granulysin Using a Mammalian Expression System

Cytotoxic lymphocytes release proteins contained within the cytoplasmic cytolytic granules after recognition of infected or tumor target cells. These cytotoxic granular proteins (namely granzymes, granulysin, and perforin) are key immunological mediators within human cellular immunity. The availability of highly purified cytotoxic proteins has been fundamental for understanding their function in immunity and mechanistic involvement in sepsis and autoimmunity. Methods for recovery of native cytotoxic proteins can be problematic leading to: 1) the co-purification of additional proteins, confounding interpretation of function, and 2) low yields of highly purified proteins. Recombinant protein expression of individual cytolytic components can overcome these challenges. The use of mammalian expression systems is preferred for optimal post-translational modifications and avoidance of endotoxin contamination. Some of these proteins have been proposed for host directed human therapies (e.g. - granzyme A), or treatment of systemic infections or tumors as in granulysin. We report here a novel expression system using HEK293T cells for cost-effective purification of high yields of human granzymes (granzyme A and granzyme B) and granulysin with enhanced biological activity than previous reports. The resulting proteins are free of native contaminants, fold correctly, and remain enzymatically active. Importantly, these improvements have also led to the first purification of biologically active recombinant human granulysin in high yields from a mammalian system. This method can be used as a template for purification of many other secreted cellular proteins and may lead to advances for human medicine.

A Profound Membrane Reorganization Defines Susceptibility of Plasmodium falciparum Infected Red Blood Cells to Lysis by Granulysin and Perforin

Malaria remains one of the most serious health problems in developing countries. The causative agent of malaria, Plasmodium spp., have a complex life cycle involving multiple developmental stages as well as different morphological, biochemical and metabolic requirements. We recently found that γδ T cells control parasite growth using pore-forming proteins to deliver their cytotoxic proteases, the granzymes, into blood residing parasites. Here, we follow up on the molecular mechanisms of parasite growth inhibition by human pore-forming proteins. We confirm that Plasmodium falciparum infection efficiently depletes the red blood cells of cholesterol, which renders the parasite surrounding membranes susceptible to lysis by prokaryotic membrane disrupting proteins, such as lymphocytic granulysin or the human cathelicidin LL-37. Interestingly, not the cholesterol depletion but rather the simultaneous exposure of phosphatidylserine, a negatively charged phospholipid, triggers resistance of late stage parasitized red blood cells towards the eukaryotic pore forming protein perforin. Overall, by revealing the molecular events we establish here a pathogen-host interaction that involves host cell membrane remodeling that defines the susceptibility towards cytolytic molecules.

Granzyme B Attenuates Bacterial Virulence by Targeting Secreted Factors

Pathogenic bacteria secrete virulence factors that interact with the human host to establish infections. The human immune system evolved multiple mechanisms to fight bacterial invaders, including immune proteases that were demonstrated to contribute crucially to antibacterial defense. Here we show that granzyme B degrades multiple secreted virulence mediators from Listeria monocytogenes, Salmonella typhimurium, and Mycobacteria tuberculosis. Pathogenic bacteria, when infected in the presence of granzyme B or granzyme-secreting killer cells, fail to grow in human macrophages and epithelial cells owing to their crippled virulence. A granzyme B-uncleavable mutant form of the major Listeria virulence factor, listeriolysin O, rescued the virulence defect in response to granzyme treatment. Hence, we link the degradation of a single factor with the observed decrease in virulent bacteria growth. Overall, we reveal here an innate immune barrier function of granzyme B by disrupting bacterial virulence to facilitate bacteria clearance by bystander immune and non-immune cells.

Short-term functional adaptation of aquaporin-1 surface expression in the proximal tubule, a component of glomerulotubular balance

Transepithelial water flow across the renal proximal tubule is mediated predominantly by aquaporin-1 (AQP1). Along this nephron segment, luminal delivery and transepithelial reabsorption are directly coupled, a phenomenon called glomerulotubular balance. We hypothesized that the surface expression of AQP1 is regulated by fluid shear stress, contributing to this effect. Consistent with this finding, we found that the abundance of AQP1 in brush border apical and basolateral membranes was augmented >2-fold by increasing luminal perfusion rates in isolated, microperfused proximal tubules for 15 minutes. Mouse kidneys with diminished endocytosis caused by a conditional deletion of megalin or the chloride channel ClC-5 had constitutively enhanced AQP1 abundance in the proximal tubule brush border membrane. In AQP1-transfected, cultured proximal tubule cells, fluid shear stress or the addition of cyclic nucleotides enhanced AQP1 surface expression and concomitantly diminished its ubiquitination. These effects were also associated with an elevated osmotic water permeability. In sum, we have shown that luminal surface expression of AQP1 in the proximal tubule brush border membrane is regulated in response to flow. Cellular trafficking, endocytosis, an intact endosomal compartment, and controlled protein stability are the likely prerequisites for AQP1 activation by enhanced tubular fluid shear stress, serving to maintain glomerulotubular balance.

The attitude of the general public towards preoperative assessment and risks associated with general anesthesia

PURPOSE

To survey the general public's attitude towards preoperative assessment and commonly perceived fears about general anesthesia.

METHODS

A province wide telephone survey was conducted in Alberta. General and regional anesthesia were defined, a scenario involving major knee surgery was described, and participants were asked to choose between regional and general anesthesia. Respondents used a seven-point scale to rate the importance of seeing an anesthesiologist preoperatively and were questioned about the timing of such a visit. Attitudes towards commonly perceived fears associated with anesthesia were also assessed.

RESULTS

A total of 1,216 people were surveyed. Over 30% of respondents felt that it was very important to see an anesthesiologist preoperatively, with a total of over 60% attributing a high degree of importance to this. Fifty percent felt that this assessment should occur on the day prior to surgery. A preference for regional or general anesthesia was not expressed in the situation. Approximately 20% of respondents were very concerned about brain damage, waking up intraoperatively and memory loss. Twelve percent were concerned about dying intraoperatively. Nine percent expressed concern about postoperative pain, with 12% reporting being concerned about nausea and vomiting.

CONCLUSIONS

The general public considers anesthetic assessment on the day prior to surgery an important part of preoperative preparation. Fears of brain damage, death and intraoperative awareness associated with general anesthesia remain prevalent, suggesting that preoperative education of patients should address these concerns. The general population was less concerned about realistic fears such as nausea, vomiting and postoperative discomfort.

Rocuronium anaphylaxis and multiple neuromuscular blocking drug sensitivities

PURPOSE

To report a case of anaphylaxis to rocuronium and the sensitivities to multiple neuromuscular blocking drugs in a patient with no previous exposure to this group of drugs. We describe the current recommendations for both intraoperative and postoperative testing of these patients.

CLINICAL FEATURES

A 36-yr-old man was admitted for repair of a ruptured Achilles tendon. Following induction of general anesthesia with fentanyl and propofol, 60 mg of rocuronium were given to facilitate tracheal intubation. He immediately became profoundly hypotensive with impalpable pulses, and blood pressure could not be recorded. Airway pressure increased markedly, and hand ventilation of the lungs became very difficult. His airway was secured and he was successfully resuscitated with 3 mg epinephrine and three litres crystalloid and colloid intravenous fluid therapy. His recovery in the intensive care unit was uneventful and the operation was performed four days later under spinal anesthesia. Subsequent skin prick testing, performed six weeks later, demonstrated strong positive weal and flare reactions to rocuronium, vecuronium and pancuronium, and some cross-reactivity with the benzylisoquinolinium group of muscle relaxants.

CONCLUSION

Muscle relaxants are responsible for 61.6% of cases of anaphylaxis during general anesthesia. Cross-reactivity is common, as this group of drugs share a quaternary ammonium group. It is mandatory that patients be tested for both the agent responsible and cross-reactivity following an anaphylactic response. We suggest a protocol for investigation of suspected anaphylaxis.

Definition of a negative modulation domain in the human progesterone receptor

The progesterone receptor (PR) occurs in two major forms, the full-length PRB and the amino-truncated PRA, which lacks 164 amino-terminal residues. PRB functions as a strong transcriptional activator of progesterone-responsive genes, whereas PRA is inactive in several cell types where it may even act as a trans-dominant repressor of PRB and other steroid receptors, like the glucocorticoid receptor or, reportedly, the estrogen receptor. We initially observed that a PR deleted of its entire amino domain (PR538-C) is incapable of trans-repressing PRB or glucocorticoid receptor, suggesting that a negative modulation domain must be contained in the region between position 165 and 538. After testing progressive deletion mutants and chimeras, we demonstrate that this negative modulating domain is confined within 120 residues in the amino-terminal region and that it contains a subdomain of 40 residues that is crucial for intermolecular transrepression. Duplication, deletion, and transplantation of the negative modulation domain show that the negative modulation domain has only a limited functional autonomy. In our hands, transrepression of estrogen receptor could not be substantiated, and, under our conditions, at least an equimolar concentration of PRA expression plasmid is required for transrepression. Our deletion studies reveal domains that correlate with strong homology patches between the amino-terminal domains of mammalian and avian PR.