Hspa8 and ICAM-1 as damage-induced mediators of γδ T cell activation

Tissue-resident γδ T cells form the first line of defense at barrier surfaces where they survey host tissue for signs of stress or damage. Following recognition of injury, γδ T cells play a crucial role in the wound-healing response through the production of growth factors and cytokines that promote proliferation in surrounding epithelial cells. To initiate this response, γδ T cells require interactions with a variety of epithelial-expressed costimulatory molecules in addition to primary signaling through their TCR. In the epidermis these signals include the coxsackie and adenovirus receptor (CAR), histocompatibility antigen 60c (H60c), and plexin B2, which interact with γδ T cell-expressed junctional adhesion molecule-like protein (JAML), NKG2D, and CD100, respectively. Here we identify heat shock protein family A member 8 (Hspa8) and ICAM-1 as two additional keratinocyte-expressed costimulatory molecules for epidermal resident γδ T cells (termed DETC). These molecules were rapidly up-regulated in the epidermis following wounding in both mouse and human tissue. Both Hspa8 and ICAM-1 had a costimulatory effect on DETC, inducing proliferation, CD25 up-regulation, and IL-2 production. We also provide evidence that DETC can be activated through the potential ICAM-1 and Hspa8 receptors LFA-1 and CD316. Finally, knockdown of Hspa8 in keratinocytes reduced their ability to activate DETC in culture and ICAM-1-/- mice exhibited impaired rates of healing in skin-organ culture suggesting a role for these proteins in the DETC-mediated damage response. Together with previous work on CAR, H60c, and plexin B2, these results add to a picture of a complex keratinocyte wound signature that is required for efficient DETC activation.

ENTPD1 (CD39) Expression Inhibits UVR-Induced DNA Damage Repair through Purinergic Signaling and Is Associated with Metastasis in Human Cutaneous Squamous Cell Carcinoma

UVR and immunosuppression are major risk factors for cutaneous squamous cell carcinoma (cSCC). Regulatory T cells promote cSCC carcinogenesis, and in other solid tumors, infiltrating regulatory T cells and CD8⁺ T cells express ectonucleoside triphosphate diphosphohydrolase 1 (ENTPD1) (also known as CD39), an ectoenzyme that catalyzes the rate-limiting step in converting extracellular adenosine triphosphate (ATP) to extracellular adenosine (ADO). We previously showed that extracellular purine nucleotides influence DNA damage repair. In this study, we investigate whether DNA damage repair is modulated through purinergic signaling in cSCC. We found increased ENTPD1 expression on T cells within cSCCs when compared with the expression on T cells from blood or nonlesional skin, and accordingly, concentrations of derivative extracellular adenosine diphosphate (ADP), adenosine monophosphate (AMP), and ADO are increased in tumors compared with those in normal skin. Importantly, ENTPD1 expression is significantly higher in human cSCCs that metastasize than in those that are nonmetastatic. We also identify in a mouse model that ENTPD1 expression is induced by UVR in an IL-27-dependent manner. Finally, increased extracellular ADO is shown to downregulate the expression of NAP1L2, a nucleosome assembly protein we show to be important for DNA damage repair secondary to UVR. Together, these data suggest a role for ENTPD1 expression on skin-resident T cells to regulate DNA damage repair through purinergic signaling to promote skin carcinogenesis and metastasis.

[Management of multiresistant bacteria in urology]

Contamination and infection with extensive drug resistant (XDR) bacteria are increasing in urology with the exception of methicillin resistant Staphylococcus aureus (MRSA) (stabilization). They often lead to logistic and therapeutical problems. Only 30-50% of XDR cases are of exogenous origin. To slow this trend, screening, hygiene programs, isolation, decontamination, targeted therapy of symptomatic infections, education programs, and success controls should be applied. Furthermore, all regulatory and legal instructions should be followed. Local hygiene networks help to find apt measures for XDR control. It is important to balance hygiene measures against hygiene hysteria. To prepare urological instruments, a local instrument preparation plan that takes into consideration all legal instructions should be followed. The efforts in health system general prophylactic measures should be supported. Only with consistent implementation in all areas of daily life (health care, local environment, animal husbandry, and soil contaminated within the framework of animal husbandry) can a substantial reduction of XDR bacteria be achieved in the long term.

Synthese und Kristallstruktur von Pentakis(dimethylsulfoxid)- oxo-titan(IV)chlorid / Synthesis and Crystal Structure of Pentakis(dimethylsulfoxide)-oxo-titanium(IV) Chloride

Pentakis(dimethylsulfoxide)-oxo-titanium(IV) chloride is obtained by reaction of titanium tetrachloride with a stoichiometric amount of water in dimethylsulfoxide. A single crystal structure determination (P1̄, a = 9.564(6), b = 10.504(7), c = 12.510(8) Å, α = 70.21(5), β = 83.48(5), γ = 89.82(5)°, V = 1174 Å3, Z = 2) shows a dicationic titanium(IV) complex with five dimethylsulfoxide ligands and one oxygen atom. The two chlorine anions are not bonded to the complex cation. The TiO6-fragment is a distorted octahedron, where five of the six oxygen atoms belong to the coordinated dimethylsulfoxide molecules.

Skin-resident T cells sense ultraviolet radiation-induced injury and contribute to DNA repair

Skin-resident T cells have been shown to play important roles in tissue homeostasis and wound repair, but their role in UV radiation (UVR)-mediated skin injury and subsequent tissue regeneration is less clear. In this study, we demonstrate that acute UVR rapidly activates skin-resident T cells in humans and dendritic epidermal γδ T cells (DETCs) in mice through mechanisms involving the release of ATP from keratinocytes. Following UVR, extracellular ATP leads to an increase in CD69 expression, proliferation, and IL-17 production, and to changes in DETC morphology. Furthermore, we find that the purinergic receptor P2X7 and caspase-1 are necessary for UVR-induced IL-1 production in keratinocytes, which increases IL-17 secretion by DETCs. IL-17, in turn, induces epidermal TNF-related weak inducer of apoptosis and growth arrest and DNA damage-associated gene 45, two molecules linked to the DNA repair response. Finally, we demonstrate that DETCs and human skin-resident T cells limit DNA damage in keratinocytes. Taken together, our findings establish a novel role for skin-resident T cells in the UVR-associated DNA repair response and underscore the importance of skin-resident T cells to overall skin regeneration.

[Asymptomatic Renal Stones: Do they really Exist?]

BACKGROUND

Asymptomatic renal calculi without any history of colic, hematuria or infection can be found as an incidental finding during preven-tive check-ups. The aim of our study was to eval-uate whether these stones provoke symptoms with the need for further treatment during the follow-up and whether they cause cortical defects which may consecutively affect the renal func-tion.

PATIENTS AND METHODS

In a prospective study we evaluated 104  patients with renal calculi. The -medical history, radiological findings and functional imaging as well as urine and blood analyses were recorded and evaluated. The influence of stone size and localisation on the development of acute stone-related symptoms, renal function and renal scarring were evaluated. Furthermore, we analysed whether localised pathological findings in radiographic or functional imaging may influence the creatinine level. The follow-up was be-tween 12 and 48  months (median: 25  months).

RESULTS

During the study period 27 / 104 of our patients (26 %) developed symptomatic events (renal colic, hematuria, infection) in which patients with middle pole calculi with a mean -cumulative stone diameter of 9.8  mm had the -highest risk. A localised renal scarring could be found in 36.6 %. These patients had a significantly higher risk in presenting an increased creatinine level. Increasing stone size was diagnosed in 39  cases (37.5 %).

CONCLUSIONS

Asymptomatic renal stones have to be controlled regularly in order to prevent the -patient from loss of renal function and hypertension caused by increasing stones or urinary tract infection.

The development of stimulus control with and without a lighted key

In two experiments, the effect of an illuminated response key on the acquisition of stimulus control by an airflow stimulus was assessed. In the first experiment, pigeons were given nondifferential training with airflow emerging from behind the response key in one of three conditions of illumination: trained to peck a lighted key, trained to peck an unlighted key with a houselight present, trained to peck a key in total darkness. After 10 days of training on a variable-interval schedule of reinforcement, all subjects were given a generalization test on airflow velocity. The gradients for subjects trained in the dark were sharp, while those for subjects trained in lighted conditions were shallow. In the second experiment, the effect of an irrelevant keylight on the acquisition of an airflow velocity discrimination was assessed. Two groups of pigeons were trained to discriminate two airflow velocities. One group was trained with a lighted response key and the other was trained to peck the response key in total darkness. The dark-trained subjects acquired the discrimination more rapidly. The results demonstrate that the acquisition of stimulus control by airflow with either a differential or nondifferential training procedure can be overshadowed by keylight.

Summation of punishment suppression

In two experiments, eight rats were trained to lever press with food on a variable-interval schedule. Bar pressing produced shock on a variable-interval schedule in the presence of two independently presented stimuli, a light and a tone. Two rats in each experiment received alternative presentations of the light and the tone and were consequently always in the presence of a stimulus that signalled variable-interval punishment. The other two rats in each experiment were treated similarly except that they received periods in which neither light nor tone was present. During these periods, bar pressing was not punished. The two stimuli that signalled punishment were then presented simultaneously to evaluate the effect of stimulus compounding on response suppression. The subjects trained without punishment-free periods did not show summation to the compound stimulus; the subjects trained with punishment-free periods showed summation of suppression. The major difference between the two experiments was the longer mean interval of variable-interval punishment used in the second experiment. This manipulation made the summation effect more resistant to extinction and thus increased its magnitude.

A novel TWO-STEP renaturation procedure for efficient production of recombinant BMP-2

Bone morphogenetic proteins (BMPs) stimulate bone formation and thus constitute important protein therapeutics. Here, a novel procedure is presented which allows fast and efficient production of biologically active BMP-2 via a TWO-STEP procedure: the conditions are designed such that the first step favors formation of monomeric species with the correct intramolecular disulfide bridges, the conditions of the second folding reaction stimulate the formation of the intermolecular disulfide bridge. The short processing times and increased yields compared to previously published procedures allow low-cost production of this important protein drug.

Calculation of silicone breast implant volumes using breast magnetic resonance imaging

BACKGROUND

Patients needing silicone gel-filled breast implant surgical revision often do not have information as to the size of their implants. Clinical estimates may be erroneous and an accurate, in vivo method of determining breast implant volume would be very useful in planning surgery.

OBJECTIVE

Our objective was to determine whether magnetic resonance imaging (MRI) scans of the breast in combination with a computer-assisted detection (CAD) system could provide accurate estimation of implant volumes in patients with silicone gel-filled implants, using known implant volumes for comparison.

METHODS

All MRI scans were performed for medical necessity before implant revision surgery or for follow-up. Scans and silicone implant volume calculations were performed in 20 patients (39 breasts). Fifteen patients (n = 27 breasts) had known implant volumes. The MRI images were analyzed blindly by a single radiologist using the image processing features of an MRI CAD system (DynaCAD; Invivo, Birmingham, MI) in a novel way. Computed implant volumes were compared to known implant volumes obtained from documented preoperative notes (n = 17) or following implant removal via implant markings (n = 10).

RESULTS

Average deviation of the 27 known implant volumes from those calculated by MRI DynaCAD analysis was only 0.82% (SD, 3.95%). In four of 27 breasts (14.8%), MRI calculations matched the clinical volumes exactly. The widest volume deviation range for all implants was +11.4% to -4.44%. A variety of implant types were found, with 11 confirmed ruptures.

CONCLUSIONS

The calculation of silicone gel-filled breast implant volume using breast MRI scans and a commercially-available CAD system appears to be sufficiently accurate that it may have significant clinical benefit in planning revision implant surgery. Calculations can be easily obtained in five minutes. To our knowledge, this is the first report describing this method to reliably measure silicone implant volumes preoperatively.

A role for human skin-resident T cells in wound healing

Epidermal T cells have been shown to play unique roles in tissue homeostasis and repair in mice through local secretion of distinct growth factors in the skin. Human epidermis contains both alphabeta(+) and gammadelta(+) T cells whose functional capabilities are not understood. We demonstrate that human epidermal T cells are able to produce insulin-like growth factor 1 (IGF-1) upon activation and promote wound healing in a skin organ culture model. Moreover, an analysis of the functional capabilities of T cells isolated from acute versus chronic wounds revealed a striking difference. Both alphabeta(+) and Vdelta1(+) T cells isolated from acute wounds actively produced IGF-1, demonstrating that they are activated during tissue damage to participate in wound repair. In contrast, IGF-1 production could not be detected in T cells isolated from chronic wounds. In fact, skin T cells isolated from chronic wounds were refractory to further stimulation, suggesting an unresponsive state. Collectively, these results define a novel role for human epidermis-resident T cells in wound healing and provide new insight into our understanding of chronic wound persistence.

Safety and feasibility of long-term temozolomide treatment in patients with high-grade glioma

We surveyed neuro-oncologists regarding patients treated with temozolomide for at least 12 cycles or 12 months. Patients receiving first-line temozolomide for a median 13 cycles had a median progression-free survival (PFS) of 14 months. Patients with recurrent disease receiving a median 14 cycles had a median PFS of 15.5 months. A small percentage of patients experienced grade III to IV toxicity. These results suggest that long-term treatment with temozolomide is feasible and well tolerated.

Reduction of Pacemaker Pressure Symptoms Using Nonantigenic Preserved Human Dermis Grafts

Skin pressure symptoms can occur in thin patients with pacemakers, with erosion through the skin surface a possibility. To correct this problem without device removal, two patients had nonantigenic preserved human dermis grafts placed over their pacemakers. This acellular nonantigenic human dermal substitute provided significant thickness over the devices and improvement in pressure symptoms.

Cultured pressure ulcer fibroblasts show replicative senescence with elevated production of plasmin, plasminogen activator inhibitor-1, and transforming growth factor-beta1

In a 16-patient study, cultured fibroblast populations from normal skin were able to replicate an average of 14.8 +/- 2.2 times before becoming senescent, while fibroblast populations from the ulcer bed reached the end of their replicative life span after 7.2 +/- 1.9 population doublings (p= 0.001). Fibroblast populations from 10 of 16 pressure ulcers became senescent after fewer than five population doublings, whereas when populations of fibroblasts from adjacent normal skin were studied, only 2 of 16 became senescent within this same time period. In addition, only an occasional fibroblast from normal skin stained positively for senescence-associated beta-galactosidase compared to approximately 50% of equally aged ulcer bed fibroblasts (p = 0.0060). Senescent ulcer bed fibroblasts secreted significantly more plasmin than early passage ulcer bed fibroblasts (p= 0.0237), nearly six times as much plasmin as early passage normal skin fibroblasts (p < 0.0001), three and a half times the level of normal skin fibroblasts of the same age (11.52 +/- 4.58 microg/mg protein; p= 0.0003), and more than one and a half times the level of senescent normal skin fibroblasts (p= 0.0525). Senescent pressure ulcer fibroblasts generated significantly more plasminogen activator inhibitor-1 (1179.27 +/- 25.37 ng/mg protein) than normal skin fibroblasts of the same age (132.16 +/- 16.20 ng/mg protein; p = 0.0357). Also, senescent ulcer bed fibroblasts produced higher levels of transforming growth factor-beta1, but these were not significantly different from senescent normal skin fibroblasts. Although senescent ulcer fibroblasts produce elevated levels of plasminogen activator inhibitor-1 and transforming growth factor-beta1, the ratio of these factors to plasmin levels suggests that this may have little influence on extracellular matrix synthesis or maintenance in the chronic wound. These data show that cultured fibroblasts from most patient pressure ulcers profile a wound environment that is associated with an increasing population of senescent fibroblasts; however, factors within the chronic wound environment that promote cellular senescence remain unclear. We have proposed that a prolonged inflammatory response may be a contributing factor to the chronic wound condition.

Assessment of cytological criteria for diagnosing osteosarcoma in dogs

OBJECTIVES

To evaluate the specific cytological criteria of osteosarcomas in dogs.

METHODS

Significant cytological characteristics of osteosarcoma and benign mesenchymal bone proliferations were determined from imprint smears of 25 dogs with osteosarcoma (group 1) and 20 dogs admitted for removal of surgical bone implants after uncomplicated healing of bone fractures (group 2).

RESULTS

Mild to moderate cellular necrosis occurred frequently in patients with osteosarcoma. The cytoplasm of osteoblasts was pale blue to blue with a more pronounced basophilia in group 2. In 48 per cent of the patients in group 1, but none in group 2, osteoblasts showed a slight to moderate eosinophilic cytoplasmic granulation. In both groups, osteoblasts contained one red to pale blue nucleus with one or two grey-red to blue nucleoli in group 2. Forty-four per cent of animals in group 1 had osteoblasts with more than two nucleoli per nucleus. The median nuclear:cytoplasmic ratio was higher in group 1 (1:2.0) than in group 2 (1:3.5). Osteoblasts in group I were frequently seen to have a clumped chromatin pattern and showed significantly more criteria of malignancy (median six criteria per patient) than those in group 2 (median two criteria per patient). In group 1, mitoses of osteoblasts were detectable in 23 of 25 dogs, whereas only one dog in group 2 had evidence of mitotic osteoblasts.

CLINICAL SIGNIFICANCE

Cytological criteria can be helpful in the diagnosis of canine osteosarcoma.

Squamous Cell Carcinoma of the Skin

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Identify the subtypes of squamous cell carcinoma of the skin. 2. Identify factors that affect recurrence and/or metastasis. 3. Develop a surgical management plan for treating high-risk squamous cell carcinoma of the skin. In treating squamous cell carcinoma of the skin, a key concept in proper management is understanding why certain tumors are more prone to both recurrence and metastasis. When developing a surgical management plan, an understanding of "high risk" is essential. This article concentrates on identifying those tumor subtypes and factors that may serve as predictors of high-risk status as well as on providing management suggestions.

Alterations in fibroblast alpha1beta1 integrin collagen receptor expression in keloids and hypertrophic scars

Keloids and hypertrophic scars are significant symptomatic clinical problems characterized by excess collagen. Although extensive research has focused on fibroblasts and collagen turnover in these aberrant scars, little work has been done on the expression of integrins (cell membrane structures that link cells to extracellular matrix) within these lesions. Integrin-mediated regulation of collagen synthesis has previously been observed in explanted fibroblasts from normal and fibrotic dermis, and integrin alpha1 knockout mice maintain increased collagen synthesis consistent with a role for alpha1beta1 in providing negative feedback on collagen synthesis. These findings suggested the need to evaluate integrin roles in keloids and hypertrophic scars. In this study we examined integrin expression in keloids (n = 11), hypertrophic scars (n = 5), radiation ulcers (n = 2), and normal skin specimens (n = 8). We used a novel approach to analysis by isolating dermal fibroblasts directly from tissue (without explant culture) and determining surface integrin expression by flow cytometry. We found that keloids and hypertrophic scars have marked alterations in fibroblast integrin expression and contain several distinct populations of fibroblasts. One of these populations expresses high levels of alpha1 integrin, and the proportion of these cells is higher in keloids (63% +/- 3.6% SEM) and hypertrophic scars (45% +/- 2.7% SEM) than in normal skin tissues (28% +/- 4.7% SEM). The different populations of fibroblasts defined by integrin expression merge, however, when the cells are serially cultured, suggesting that there may be aspects of the dermal microenvironment that maintain the integrin phenotypic heterogeneity in dermal fibroblasts.

Portal vein thrombosis after hematopoietic cell transplantation: frequency, treatment and outcome

Patients who develop veno-occlusive disease (VOD) of the liver may have low plasma levels of the natural anticoagulants protein C and antithrombin III, but large vessel thromboses are not commonly reported in these patients. We reviewed the records of 1847 consecutive patients for evidence of portal vein thrombosis. Eight patients (0.4%) developed portal vein thrombosis (PVT) at a median of day +28 (range 3-58). All patients had clinical evidence of VOD with ascites, a median total serum bilirubin 11.9 mg/dl, and median weight gain from baseline of 7.9%. Median plasma levels of antithrombin III and protein C were low (36% and 21%, respectively). Four patients with PVT died of severe VOD and multi-organ failure, but PVT did not contribute to death. We conclude that PVT is a rare complication of hematopoietic cell transplant and is associated with hepatic VOD. We speculate that PVT resulted from diminished portal venous flow (related to hepatic sinusoidal obstruction to blood flow) and a hypercoagulable state (related to low circulating antithrombin III and protein C levels). Prognosis depended on the severity of the underlying VOD and not PVT per se, suggesting that treatments directed solely toward dissolution of portal vein thrombi should be used with caution in this setting.

Assessment of cytological criteria for diagnosing basal cell tumours in the dog and cat

A retrospective study was undertaken in which cytological features of basal cell tumours from 18 dogs and 12 cats were examined. Fine-needle aspiration biopsy was performed for cytological examination and diagnosis was confirmed on histopathological examination of excised tumour specimens. Cytological smears were analysed for occurrence of cystic areas, as well as frequencies of squamous cells, fibrocytes, fibroblasts, neutrophils, lymphocytes, mast cells, melanocytes and basal cells. Basal cell aggregates were examined for indicators of malignancy, evidence of basaloid cell structure, well defined cellular borders and cell aggregation patterns. Cellularity and quality of smears was moderate to good, although, in six aspirates, cellularity was poor due to a high amount of degenerate material within the tumours. Fifteen of the smears revealed between one and three nuclear criteria of malignancy. However, despite the less well differentiated appearance of basal cells that was sometimes seen, the tumours were considered benign based on histopathological examination. Basal cell tumours are therefore likely to be underdiagnosed on cytological examination due to non-specific features. The occurrence of other cell populations and lack of cells with basaloid structures and linear aggregation patterns might further confuse the tumour diagnosis. The authors conclude that the cytological diagnosis of basal cell tumours can be based on the criteria described in the present study.

Increased production of human proinsulin in the periplasmic space of Escherichia coli by fusion to DsbA

The production of human proinsulin in its disulfide-intact, native form in Escherichia coli requires disulfide bond formation and the periplasmic space is the favourable compartment for oxidative folding. However, the secretory expression of proinsulin is limited by its high susceptibility to proteolysis and by disulfide bond formation, which is rate-limiting for proinsulin folding. In this report we describe a method for the production of high amounts of soluble, native human proinsulin in E. coli. We fused proinsulin to the C-terminus of the periplasmic disulfide oxidoreductase DsbA via a trypsin cleavage site. As DsbA is the main catalyst of disulfide bond formation in E. coli, we expected increased yields of proinsulin by intra- or intermolecular catalysis of disulfide bond formation. In the context of the fusion protein, proinsulin was found to be stabilised, probably due to an increased solubility and faster disulfide bond formation. To increase the yield of DsbA-proinsulin in the periplasm, several parameters were optimised, including host strains and cultivation conditions, and in particular growth medium composition and supplement of low molecular weight additives. We obtained a further, about three-fold increase in the amount of native DsbA-proinsulin by addition of L-arginine or ethanol to the culture medium. The maximum yield of native human proinsulin obtained from the soluble periplasmic fraction after specific cleavage of the fusion protein with trypsin was 9.2 mg g(-1), corresponding to 1.8% of the total cell protein.

Polyionic fusion peptides function as specific dimerization motifs

The de novo design of a molecular adapter for directed association and covalent linkage of two polypeptides is presented. Using peptides containing charged amino acid residues and an additional cysteine residue (AlaCysLys(8) and AlaCysGlu(8)) we demonstrate that the electrostatic interaction promotes the association of two synthetic peptides and, subsequently, disulfide bond formation. The reaction depends on both the redox potential and on the ionic strength of the buffer. Varying the redox potential, the interaction of the peptides was quantified by a Delta G(0') of 6.6 +/- 0.2 kcal/mol. Heterodimerization of the peptides is highly specific, a competition of association by other cysteine containing compounds could not be observed. Two proteins comprising cysteine-containing polyionic fusion peptides, a modified Fab fragment and an alpha-glucosidase fusion, could be specifically conjugated by directed association and subsequent disulfide bond formation. Both proteins retain their functional characteristics within the bifunctional conjugate: enzymatic activity of the alpha-glucosidase and antigen-binding capacity of the Fab fragment are equivalent to the non-conjugated components.

Binding of external ligands onto an engineered virus capsid

The development of novel delivery systems for therapeutic substances includes targeting of the carriers to a specific site or tissue within the body of the recipient. This can be accomplished by appropriate receptor-binding domains and requires linking of these domains to the carrier. We have used recombinantly expressed polyomavirus-like particles as a model system and inserted the sequence of a WW domain into different surface loops of the viral capsid protein VP1. In one variant, the WW domain maintained its highly selective binding properties of proline-rich ligands and showed an increased affinity but also an accelerated association/dissociation equilibrium compared to the isolated WW domain, thus allowing a short-term coupling of external ligands onto the surface of the virus-like particles.

Cosecretion of chaperones and low-molecular-size medium additives increases the yield of recombinant disulfide-bridged proteins

Attempts were made to engineer the periplasm of Escherichia coli to an expression compartment of heterologous proteins in their native conformation. As a first approach the low-molecular-size additive L-arginine and the redox compound glutathione (GSH) were added to the culture medium. Addition of 0.4 M L-arginine and 5 mM reduced GSH increased the yield of a native tissue-type plasminogen activator variant (rPA), consisting of the kringle-2 and the protease domain, and a single-chain antibody fragment (scFv) up to 10- and 37-fold, respectively. A variety of other medium additives also had positive effects on the yield of rPA. In a second set of experiments, the effects of cosecreted ATP-independent molecular chaperones on the yields of native therapeutic proteins were investigated. At optimized conditions, cosecretion of E. coli DnaJ or murine Hsp25 increased the yield of native rPA by a factor of 170 and 125, respectively. Cosecretion of DnaJ also dramatically increased the amount of a second model protein, native proinsulin, in the periplasm. The results of this study are anticipated to initiate a series of new approaches to increase the yields of native, disulfide-bridged, recombinant proteins in the periplasm of E. coli.

Conjugation of an antibody Fv fragment to a virus coat protein: cell-specific targeting of recombinant polyoma-virus-like particles

The development of cell-type-specific delivery systems is highly desirable for gene-therapeutic applications. Current virus-based vector systems show broad cell specificity, which results in the need to restrict the natural tropism of these viral systems. Here we demonstrate that tumour-cell-specific virus-like particles can be functionally assembled in vitro from recombinant viral coat protein expressed in Escherichia coli. The insertion of a negatively charged peptide in the HI loop of polyoma VP1 interferes with the binding of VP1 to the natural recognition site on mammalian cells and also serves as an adapter for the coupling of antibody fragments that contain complementary charged fusion peptides. A recombinant antibody fragment of the tumour-specific anti-(Lewis Y) antibody B3 could be coupled to the mutant VP1 by engineered polyionic peptides and an additional disulphide bond. With this system an entirely recombinant cell-specific delivery system assembled in vitro could be generated that transfers genes preferentially to cells presenting the tumour-specific antigen on the cell surface.

The pro-sequence facilitates folding of human nerve growth factor from Escherichia coli inclusion bodies

Nerve growth factor (beta-NGF), a neurotrophin required for the development and survival of specific neuronal populations, is translated as a prepro-protein in vivo. While the presequence mediates translocation into the endoplasmic reticulum, the function of the pro-peptide is so far unknown. As the pro-sequences of several proteins are known to promote folding of the mature part, the renaturation behaviour of recombinant human beta-NGF pro-protein was compared to that of the mature form. Expression of rh-pro-NGF in Escherichia coli led to the formation of inclusion bodies (IBs). The presence of the covalently attached pro-sequence significantly increased the yield and rate of refolding with concomitant disulfide bond formation when compared to the in vitro refolding of mature NGF (rh-NGF). Physicochemical characterization revealed that rh-pro-NGF is a dimer. The pro-peptide could be removed by limited proteolysis with trypsin yielding biologically active, mature rh-NGF. Furthermore, rh-pro-NGF exhibited biological activity in the same concentration range as rh-NGF.

Pro-sequence assisted folding and disulfide bond formation of human nerve growth factor

Nerve growth factor (NGF) is a member of the neurotrophin family. These growth factors support neuronal survival and differentiation. Neurotrophins are synthesized as pre-pro-proteins. Whereas the pre-sequences mediate secretion, the function of the pro-peptides is largely unknown. To test the role of the pro-sequence as a folding enhancer, recombinant human pro-NGF (rh-pro-NGF) was produced in Escherichia coli. The oxidative refolding of rh-pro-NGF and rh-NGF was studied using electrospray mass spectrometry (ESIMS) time-course analysis. This analysis permitted both the identification and quantification of intermediates present during the process. The disulfide bonds formed at different times of the refolding processes were characterized by proteolytic digestion followed by matrix assisted laser desorption ionization mass spectrometry (MALDIMS) analysis. Folding yields and kinetics of rh-pro-NGF were significantly enhanced when compared to the in vitro refolding of mature rh-NGF. These results suggest that the pro-sequence of NGF promotes folding of the mature part.

A hyperthermostable bacterial histone-like protein as an efficient mediator for transfection of eukaryotic cells

Gene delivery has shown potential in a variety of applications, including basic research, therapies for inborn genetic defects, cancer, AIDS, tissue engineering, and vaccination. Most available systems have serious drawbacks, such as safety hazards, inefficiency under in vivo-like conditions, and expensive production. When using naked DNA, for instance, a large amount of ultrapure DNA has to be applied as a result of degradation by nucleases. Similarly, the use of eukaryotic histones, synthetic peptides, or peptide nucleic acids may be limited by high production costs. We have demonstrated a biotechnologically feasible and economical approach for gene delivery using the histone-like protein from the hyperthermostable eubacterium Thermotoga maritima, TmHU as an efficient gene transfer reagent. HU can be easily isolated from recombinant Escherichia coli, is extraordinarily stable, and protects dsDNA from thermal denaturation. This study demonstrates its use as an inexpensive tool for gene delivery.

Fibrin encapsulated liposomes as protein delivery system. Studies on the in vitro release behavior

The efficacy of biologically active proteins in medical therapy depends on the development of suitable drug delivery systems. These delivery systems need to overcome the severe problems connected with the use of proteins such as their usually short half lives in body fluids and their susceptibility to proteolysis and denaturation. Our delivery system combines two widespread devices by encapsulating liposomes containing the model protein horseradish peroxidase (HRP) inside the biopolymer fibrin. The liposomes enable the protein to remain in its preferred aqueous environment and protect it during the polymerization process. Further encapsulation of the liposomes inside fibrin was carried out in order to achieve a depot system with sustained protein release. In vitro experiments showed that the protein filled liposomes were absolutely stable within the fibrin network. In contrast to 'free' HRP, enzyme entrapped in liposomes was completely retained by the fibrin network and wasn't released from the device unless the fibrin was degraded by plasmin.