Workforce survey of PAs' genetic-genomic knowledge, attitudes, and application in practice

OBJECTIVE

This study surveyed practicing physician associates/assistants (PAs) about their genetics-genomics knowledge, attitudes, and application in practice.

METHODS

A 25-question electronic survey was emailed to each constituent organization of the American Academy of Physician Associates (AAPA) with a description of the study and a request to forward to their members. Additionally, a posting was displayed in the bulletin board section of the online AAPA Huddle.

RESULTS

Of the 420 PAs who completed the survey, few are knowledgeable (25%) about or confident (13%) in applying a genomic approach to patient care, although most (61%) think genetics-genomics is important to delivering high-quality care. Remarkably, 97% of PAs surveyed are interested in genetics-genomics continuing medical education.

CONCLUSIONS

PAs lack knowledge and confidence in integrating genetics-genomics into patient care; however, they have a positive attitude toward genetics-genomics and want to improve their knowledge and confidence through education.

Linguistic Validation of Genomic Nursing Concept Inventory to Finnish Applying Mandysova's Decision Tree Algorithm

Background and Purpose: Currently, there is no available Finnish version of the Genomic Nursing Concept Inventory tool (GNCI). This study tested the validity, reliability, and clinical usability of a Finnish translation. Methods: A decision tree algorithm was used to guide the translation, as per International Society for Pharmacoeconomics and Outcomes Research guidelines. Item-Content Validity Index (I-CVI), modified kappa (k*) statistics, and Cronbach's alpha were calculated. Results: The I-CVI and k* values were "good" to "excellent" (I-CVI = 0.63-1.00, k* = 0.52-1.00), and Cronbach's alpha value was "good" (α = 0.816; 95% confidence interval: 0.567-0.956). Conclusion: The Mandysova's decision tree algorithm provided clear and rigorous direction for the translation and validity of the Finnish GNCI.

The State of Genetics and Genomics Education in US Physician Assistant Programs

PURPOSE

This study aimed to assess the current landscape of genetics-genomics education in physician assistant (PA) student training.

METHODS

A 25-question electronic survey was emailed to program directors of the 273 accredited PA programs. Questions represented PA program demographics and 4 domains: curricular characteristics and perceived adequacy; content; curricular approaches and instructional methods; and intent, barriers, and perceived needs for an optimal curriculum.

RESULTS

A total of 115 PA program representatives (42%) returned the survey. More than two-thirds of responding programs do not require a prerequisite genetics course for matriculation. Most programs (48%) include 1 to 10 contact hours of genetics-genomics content and use various content delivery methods and approaches. Most programs (67%) use PA program faculty to teach genetics-genomics as part of one course or many courses throughout the curriculum (85%) using didactic lectures (97%). The most significant barrier to developing an optimal curriculum is an already overloaded curriculum (71%). Physician assistant educators welcome supportive resources, such as genetic case studies (96%).

CONCLUSIONS

The study findings elucidate the current state of genetics-genomics education in PA programs. Every responding program reports that genetics-genomics is integrated into their curriculum; however, no standardization exists between programs. Although medical genetics-genomics has changed and advanced rapidly since a similar survey was conducted 14 years ago, the number of contact hours is unchanged, and genetics-genomics content is less dispersed throughout PA curricula. To create genetic-competent and genomic-competent PAs, education must evolve to stay current with ongoing advancements in genomic science.

A Critical Review of the Prognostic and Predictive Implications of KRAS and STK11 Mutations and Co-Mutations in Metastatic Non-Small Lung Cancer

The Kirsten rat sarcoma viral oncogene homolog (KRAS) and serine/threonine kinase 11 (STK11) co-mutations are associated with the diverse phenotypic and heterogeneous oncogenic subtypes in non-small cell lung cancer (NSCLC). Due to extensive mixed evidence, there needs to be a review of the recent KRAS and STK11 mutation literature to better understand the potential clinical applications of these genomic biomarkers in the current treatment landscape. This critical review highlights the clinical studies that have elucidated the potential prognostic and predictive implications of KRAS mutations, STK11 mutations, or KRAS/STK11 co-mutations when treating metastatic NSCLC across various types of treatments (e.g., immune checkpoint inhibitors [ICIs]). Overall, KRAS mutations are associated with poor prognoses and have been determined to be a valid but weak prognostic biomarker among patients diagnosed with NSCLC. KRAS mutations in NSCLC have shown mixed results as a predictive clinical biomarker for immune checkpoint inhibitor treatment. Overall, the studies in this review demonstrate that STK11 mutations are prognostic and show mixed results as predictive biomarkers for ICI therapy. However, KRAS/STK11 co-mutations may predict primary resistance to ICI. Prospective KRAS/STK11-biomarker-driven randomized trials are needed to assess the predictive effect of various treatments on the outcomes for patients with metastatic NSCLC, as the majority of the published KRAS analyses are retrospective and hypothesis-generating in nature.

Sleep disturbances in Phelan-McDermid syndrome: Clinical and metabolic profiling of 56 individuals

Phelan-McDermid Syndrome (PMS) is caused by deletions at chromosome 22q13.3 or pathogenic/likely pathogenic SHANK3 variants. The clinical presentation is extremely variable and includes global developmental delay/intellectual disability (ID), seizures, neonatal hypotonia, and sleep disturbances, among others. This study investigated the prevalence of sleep disturbances, and the genetic and metabolic features associated with them, in a cohort of 56 individuals with PMS. Sleep data were collected via standardized observer/caregiver questionnaires, while genetic data from array-CGH and sequencing of 9 candidate genes within the 22q13.3 region, and metabolic profiling utilized the Biolog Phenotype Mammalian MicroArray plates. Sleep disturbances were present in 64.3% of individuals with PMS, with the most common problem being waking during the night (39%). Sleep disturbances were more prevalent in individuals with a SHANK3 pathogenic variant (89%) compared to subjects with 22q13.3 deletions of any size (59.6%). Distinct metabolic profiles for individuals with PMS with and without sleep disturbances were also identified. These data are helpful information for recognizing and managing sleep disturbances in individuals with PMS, outlining the main candidate gene for this neurological manifestation, and highlighting potential biomarkers for early identification of at-risk subjects and molecular targets for novel treatment approaches.

Genetics and Genomics Education for Physician Assistant Students: A Review of the Literature

INTRODUCTION

The purpose of this study was to critically review the literature and determine what is known about genetics-genomics education for physician assistants (PAs).

METHODS

A rapid review method was used to search CINAHL, MEDLINE, PubMed, and Web of Science databases. The review is presented historically to describe the development of genetics-genomics education in PA programs.

RESULTS

Of 594 publications retrieved, 11 articles met inclusion criteria. Retained articles include an assessment of PA programs, genetics-genomics competencies, educational efforts developed by PA programs regarding genetics-genomics, and continuing education programs for PAs.

DISCUSSION

A paucity of published literature regarding genetics-genomics education for PAs was found. The few studies retrieved describe content being taught in PA programs, the number of genetics-genomics contact hours that PA students receive, and recommendations for continuing education programs. Most of the available literature is outdated, leaving a need for more current information to inform the education of genetic- and genomic-competent PAs. Recommendations for future research include assessment of PA programs regarding genetics-genomics education; development and validation of an assessment tool to measure genetics-genomics knowledge; and utilization of the RISE2 Genomics standards to plan, implement, evaluate, and report educational interventions. These recommendations are necessary to build an evidence base regarding genomics education for PA students and practicing PAs.

Stratification of a Phelan-McDermid Syndrome Population Based on Their Response to Human Growth Hormone and Insulin-like Growth Factor

Phelan-McDermid syndrome (PMS), caused by pathogenic variants in the SHANK3 gene or 22q13 deletions, is characterized by intellectual disability, autistic features, developmental delays, and neonatal hypotonia. Insulin-like growth factor 1 (IGF-1) and human growth hormone (hGH) have been shown to reverse neurobehavioral deficits in PMS. We assessed the metabolic profiling of 48 individuals with PMS and 50 controls and determined subpopulations by taking the top and bottom 25% of responders to hGH and IGF-1. A distinct metabolic profile for individuals with PMS showed a reduced ability to metabolize major energy sources and a higher metabolism of alternative energy sources. The analysis of the metabolic response to hGH or IGF-1 highlighted a major overlap between both high and low responders, validating the model and suggesting that the two growth factors share many target pathways. When we investigated the effect of hGH and IGF-1 on the metabolism of glucose, the correlation between the high-responder subgroups showed less similarity, whereas the low-responders were still relatively similar. Classification of individuals with PMS into subgroups based on responses to a compound can allow an investigation into pathogenic mechanisms, the identification of molecular biomarkers, an exploration of in vitro responses to candidate drugs, and eventually the selection of better candidates for clinical trials.

Item and Structure Evaluation of the Genomic Nursing Concept Inventory

BACKGROUND AND PURPOSE

Genomic nursing education requires a genomic literacy assessment supported by evidence of reliability and validity. This study applied psychometric analyses to provide support for the Genomic Nursing Concept Inventory (GNCI).

METHODS

Over nine semesters, baccalaureate nursing students (N = 1,065) completed the GNCI on the first and last days of genomics instruction. Psychometric analyses assessed scale and item performance pre- and post-instruction.

RESULTS

Exploratory factor analysis supported scale unidimensionality and identified items with low pattern coefficients. Analyses supported test-retest and internal consistency reliability and criterion validity. Scale difficulty decreased by 28% from pre- to post-instruction. Underperforming items were identified for further inventory refinement.

CONCLUSIONS

Findings support use of the GNCI to measure learning needs pre-instruction and learning gains post-instruction. Data also inform planned inventory revision.

The Parent Experience of Caring for a Child with Mitochondrial Disease

Mitochondrial disease is a spectrum of progressive genetic disorders resulting from dysfunctions of cellular metabolism in the mitochondria that greatly compromise the lives of affected individuals, who are often children.

PURPOSE

This study described the parent experiences unique to caring for a child with mitochondrial disease.

METHODS

Internet surveys were made available to parents of children with a known mitochondrial disease. Surveys included demographic items and two questionnaires: Parent Experience of Child Illness (PECI) and Pediatric Inventory for Parents (PIP). Descriptive data were collected and correlations calculated to determine relationships between the parent experience and stress.

RESULTS

The majority of participants (n=231) were mothers (95%) of children with mitochondrial disease around the age of 10 years (M=9.85). Elevated scores were found in parent adjustment illness-related concerns regarding Guilt and Worry (M=2.30, SD=.650), Sorrow and Anger (M=2.09, SD=.730), Long-term Uncertainty (M=2.56, SD=.690), and Emotional Resources (M=2.36, SD=.615). Scores indicated elevated feelings of stress in terms of both difficulty and frequency. Significant correlations (p<0.01) were found between parent illness-related concerns and parenting stress.

CONCLUSIONS

The results of this study suggest that parents of a child with mitochondrial disease feel a burden of responsibility that exceeds the typical caregiver role, see their child as fragile, and have concerns about their child's future. Identification of these concerns can assist nurses to better meet the needs of these parents and families.

Randomized, placebo-controlled, phase I/IIa evaluation of the safety and immunogenicity of fowlpox virus expressing HIV gag-pol and interferon-gamma in HIV-1 infected subjects

We conducted a randomized, placebo-controlled double-blind trial to examine the safety and immunogenicity of a candidate HIV therapeutic vaccine based upon a recombinant fowl pox virus capable of coexpressing the human cytokine interferon-gamma and/or genes from HIV-1. Thirty-five eligible subjects were randomized (12 placebo, 11 fowlpox + HIV genes, 12 fowl pox + HIV genes + interferon gamma). All but one subject (placebo group) received three immunizations (by intramuscular injection on day 0, week 4 and week 12) and all completed 52 weeks of follow-up. All subjects continued to take combination antiretroviral therapy for the duration of study. There were no significant toxicity or safety concerns and the distribution of adverse events and their severity was consistent across each randomly assigned vaccine group. Comparison of placebo recipients with the combined recipients of the two vaccine constructs, in terms of anti-HIV gag ELISpot or lymphoproliferative responses, tended to favour the placebo group, but were not significantly different (difference in time-weighted mean change from baseline = 56 Spot forming units (sfu)/10(6) PBMC; p = 0.062 and 4.4 SI; p = 0.337). There were no significant changes in CTL responses by standard Cr(51) release assay. Anti-FPV antibodies were detected by week 14 in 0 placebo and 20 (87%) vaccine recipients. Although safe, neither vaccine construct appeared to possess detectable T-cell mediated anti-HIV immunogenic properties in HIV infected individuals, as measured by standard T cell assays.

The role of the distal radioulnar ligaments, interosseous membrane, and joint capsule in distal radioulnar joint stability

The individual contribution of the distal radioulnar ligaments to dorsal and palmar translational stability during forearm rotation remains controversial. Furthermore, the role of the distal radioulnar joint capsule as a restraint and contributor to stability has not been investigated. A biomechanical study was performed in 11 fresh cadaver specimens to simultaneously measure dorsal and palmar radioulnar ligament tension. Joint rotation and radial translation were measured after sequential excision of the disk, interosseous membrane, joint capsule, and radioulnar ligaments. Results confirmed that the dorsal ligament tightens during pronation while the palmar ligament becomes progressively lax; the converse occurred during supination. Translational stability remained intact at all positions throughout the sectioning sequence until one of the radioulnar ligaments was sectioned. The most significant increases in translation occurred after sectioning the dorsal radioulnar ligament in pronation and after sectioning the palmar radioulnar ligament in supination. Forearm rotation increased significantly after excising either hemicapsule.

The N-terminus of gp130 is critical for the formation of the high-affinity interleukin-6 receptor complex

Interleukin-6 (IL-6) mediates its activity through binding to two cell-surface receptors. The high-affinity human IL-6 receptor complex consists of two transmembrane anchored subunits: a ligand-specific, low-affinity IL-6 receptor and the high-affinity converter and signal transducing, gp130. Previously, using recombinant forms of human IL-6 and the extracellular ('soluble') domains of the IL-6 receptor (sIL-6R) and gp130 (sgp130), we have shown that the high-affinity IL-6R complex is hexameric, consisting of two molecules each of IL-6, sIL-6R and sgp130 (Ward et al., 1994, J. Biol. Chem. 269: 23286-23289). This paper investigates the role of the N-terminal region of gp130 in the formation of the high-affinity IL-6R complex. Using recombinant sgp130 produced with a FLAG octapeptide epitope (DYKDDDDK) at the N-terminus (sgp130-FLAG), we demonstrate, using biosensor analysis and size-exclusion chromatography, that modification of the N-terminus of sgp130 interferes with the in vitro in solution formation of the stable hexameric IL-6 receptor complex. Rather, sgp130-FLAG interacts with IL-6 and sIL-6R with a much lower affinity and forms a stable lower-order ternary complex. However, this lower-order complex is inconsistent with the solution molecular weight of a trimeric complex, as measured by size-exclusion chromatography. In contrast, N-terminal modification of the sgp130 with the FLAG epitope did not interfere with the binding of leukemia inhibitory factor or oncostatin-M (other cytokines that signal through gp130) to sgp130. These data support our model of the hexameric IL-6 receptor complex, which is biased towards the association of two IL-6.IL-6R.gp130 trimers, and postulates the critical involvement of the N-terminal Ig-like domain of gp130 in tethering the two trimers to form the stable hexamer (Simpson et al., 1997, Prot. Sci. 6: 929-955).

Identification and characterization of two distinct truncated forms of gp130 and a soluble form of leukemia inhibitory factor receptor alpha-chain in normal human urine and plasma

Leukemia inhibitory factor (LIF) is a polyfunctional cytokine known to require at least two distinct receptor components (LIF receptor alpha-chain and gp130) in order to form a high affinity, functional receptor complex. In this report, we present evidence that there are two distinct truncated forms of gp130 in normal human urine and plasma: a large form with a molecular weight of approximately 100, 000, which is similar to a previously described form of soluble gp130 in human serum, and a previously undescribed small form with a molecular weight of approximately 50,000. Using a panel of monoclonal antibodies raised against the extracellular domain of human gp130, we were able to show that the small form of the urinary gp130 probably contained only the hemopoietin domain. Both forms of gp130 bound LIF specifically and were capable of forming heterotrimeric complexes with soluble human LIF receptor alpha-chain in the presence of human LIF. In addition to the soluble forms of gp130, a soluble form of LIF receptor alpha-chain was also detected in human urine and plasma.

Evidence for the formation of a heterotrimeric complex of leukaemia inhibitory factor with its receptor subunits in solution

Leukaemia inhibitory factor (LIF) is a polyfunctional cytokine that is known to require at least two distinct receptor components (LIF receptor alpha-chain and gp130) in order to form a high-affinity, functional, receptor complex. Human LIF binds with unusually high affinity to a naturally occurring mouse soluble LIF receptor alpha-chain, and this property was used to purify a stable complex of human LIF and mouse LIF receptor alpha-chain from pregnant-mouse serum. Recombinant soluble human gp130 was expressed, with a FLAG(R) epitope (DYKDDDDK) at the N-terminus, in the methylotropic yeast Pichia pastoris and purified using affinity chromatography. The formation of a trimeric complex in solution was established by native gel electrophoresis, gel-filtration chromatography, sedimentation equilibrium analysis, surface plasmon resonance spectroscopy and chemical cross-linking. The stoichiometry of this solution complex was 1:1:1, in contrast with that of the complex of interleukin-6, the interleukin-6-specific low-affinity receptor subunit and gp130, which is 2:2:2.

Roles of histidine 31 and tryptophan 34 in the structure, self-association, and folding of murine interleukin-6

Interleukin-6 (IL-6) is a multifunctional cytokine which is involved in a broad spectrum of activities such as immune defense, hematopoiesis, and the acute phase response, as well as in the pathogenesis of multiple myeloma. A series of murine IL-6 (mIL-6) mutants, H31A, W34A, and H31A/W34A, were constructed to investigate the roles of His31 and Trp34 in the structure, conformational stability, time-dependent aggregation, folding, and spectral properties of mIL-6. The characteristic pH-dependent quenching of fluorescence of mIL-6 at low pH was shown to be caused by an interaction between Trp34 and protonated His31 at low pH and not associated with Trp157. Denaturant-induced equilibrium unfolding experiments monitored by fluorescence and far-UV CD showed that the increased quantum yield and blue shift of the wavelength of the emission maximum observed for mIL-6 at moderate denaturant concentrations were also associated with Trp34, rather than Trp157. The tendency to form aggregation-prone unfolding intermediates, as judged by poor fits to a two-state unfolding mechanism, low m values (slopes of the unfolding curve in the transition region), and the range of denaturant concentrations over which these intermediates formed, was shown to be higher for H31A than mIL-6 but significantly lower for W34A and H31A/W34A. These differences were most pronounced at pH 7.4 and correlated with the tendencies of the proteins to aggregate at high protein concentrations in the absence of denaturant. As judged by the 1H NMR chemical shifts of the aromatic residues, the global conformations of H31A and W34A were not significantly different from that of mIL-6. Nuclear Overhauser effects (NOE) between the side chains of His31 and Trp34 were consistent with the indole side chain of Trp34 being oriented toward the face of the imidazolium side chain of His31, an arrangement consistent with our estimates of a low interaction energy (0.4-0.6 kcal/mol) between these side chains. A shift in the pKa of the His31 side chain in W34A (+0.3 unit) suggested that, in the absence of Trp34, His31 could interact with other residues. Further mutations in this region should yield forms of mIL-6, even less prone to aggregation, which would be more suitable for NMR studies. Mutation of His31 and Trp34 to alanine did not significantly alter the mitogenic activity of the mutants on mouse hybridoma 7TD1 cells, even though the corresponding region of human IL-6 has been shown to be important for biological activity.

Interleukin-6: structure-function relationships

Interleukin-6 (IL-6) is a multifunctional cytokine that plays a central role in host defense due to its wide range of immune and hematopoietic activities and its potent ability to induce the acute phase response. Overexpression of IL-6 has been implicated in the pathology of a number of diseases including multiple myeloma, rheumatoid arthritis, Castleman's disease, psoriasis, and post-menopausal osteoporosis. Hence, selective antagonists of IL-6 action may offer therapeutic benefits. IL-6 is a member of the family of cytokines that includes interleukin-11, leukemia inhibitory factor, oncostatin M, cardiotrophin-1, and ciliary neurotrophic factor. Like the other members of this family, IL-6 induces growth or differentiation via a receptor-system that involves a specific receptor and the use of a shared signaling subunit, gp130. Identification of the regions of IL-6 that are involved in the interactions with the IL-6 receptor, and gp130 is an important first step in the rational manipulation of the effects of this cytokine for therapeutic benefit. In this review, we focus on the sites on IL-6 which interact with its low-affinity specific receptor, the IL-6 receptor, and the high-affinity converter gp130. A tentative model for the IL-6 hexameric receptor ligand complex is presented and discussed with respect to the mechanism of action of the other members of the IL-6 family of cytokines.

Disruption of the disulfide bonds of recombinant murine interleukin-6 induces formation of a partially unfolded state

A chemical modification approach was used to investigate the role of the two disulfide bonds of recombinant murine interleukin-6 (mIL-6) in terms of biological activity and conformational stability. Disruption of the disulfide bonds of mIL-6 by treatment with iodoacetic acid (IAA-IL-6) or iodoacetamide (IAM-IL-6) reduced the biological activity, in the murine hybridoma growth factor assay, by 500- and 200-fold, respectively. Both alkylated derivatives as well as the fully reduced (but not modified) molecule (DTT-IL-6) retained a high degree of alpha-helical structure as measured by far-UV CD (37-51%) when compared to the mIL-6 (59%). However, the intensity of the near-UV CD signal of the S-alkylated derivatives was very low relative to that of mIL-6, suggesting a reduction in fixed tertiary interactions. Both IAA-IL-6 and IAM-IL-6 exhibit native-like unfolding properties at pH 4.0, characteristic of a two-state unfolding mechanism, and are destabilized relative to mIL-6, by 0.3 +/- 1.6 and 2.4 +/- 1.2 kcal/mol, respectively. At pH 7.4, however, both modified proteins display stable unfolding intermediates. These intermediates are stable over a wide range of GdnHCl concentrations (0.5-2 M) and are characterized by increased fluorescence quantum yield and a blue shift of lambda(max) from 345 nm, for wild-type recombinant mIL-6, to 335 nm. These properties were identical to those observed for DTT-IL-6 in the absence of denaturant. DTT-IL-6 appears to form a partially unfolded and highly aggregated conformation under all conditions studied, as showed by a high propensity to self-associate (demonstrated using a biosensor employing surface plasmon resonance), and an increased ability to bind the hydrophobic probe 8-anilino-1-naphthalenesulfonic acid. The observed protein concentration dependence of the fluorescence characteristics of these mIL-6 derivatives is consistent with the aggregation of partially folded forms of DTT-IL-6, IAM-IL-6, and IAA-IL-6 during denaturant-induced unfolding. For all forms of the protein studied here, the aggregated intermediates unfold at similar denaturant concentrations (2.1-2.9 M GdnHCl), suggesting that the alpha-helical structure and nonspecific hydrophobic interprotein interactions are of similar strength in all cases.

The immediate treatment of pelvic ring disruption with the pelvic stabilizer

The management of the hemodynamically unstable patient with a severe pelvic ring disruption remains one of the most serious trauma emergencies. Standard resuscitation protocols may include attempted closure of the pelvic ring by the use of pneumatic anti-shock trousers, external fixation applied in the operating room, or a sheet wrapped around the patient in the emergency room. We report a case of pelvic ring disruption in which a successful clinical outcome was achieved with the emergent use of the Pelvic Stabilizer in the emergency room. The Pelvic Stabilizer is a device that can be effectively applied in the emergency room for the acute reduction and early stabilization of the displaced pelvis in a hemodynamically unstable patient. The use of a pelvic clamp can also be effective in the acute setting for a stable trauma patient with pelvic ring disruption. It rapidly reduces and stabilizes a potential cause for patient decompensation without obstructing access to further concomitant diagnostic or therapeutic interventions in the abdomen and perineum.

Influence of interleukin-6 (IL-6) dimerization on formation of the high affinity hexameric IL-6.receptor complex

The high affinity interleukin-6 (IL-6) signaling complex consists of IL-6 and two membrane-associated receptor components: a low affinity but specific IL-6 receptor and the affinity converter/signal transducing protein gp130. Monomeric (IL-6M) and dimeric (IL-6D) forms of Escherichia coli-derived human IL-6 and the extracellular ("soluble") portions of the IL-6 receptor (sIL-6R) and gp130 have been purified in order to investigate the effect of IL-6 dimerization on binding to the receptor complex. Although IL-6D has a higher binding affinity for immobilized sIL-6R, as determined by biosensor analysis employing surface plasmon resonance detection, IL-6M is more potent than IL-6D in a STAT3 phosphorylation assay. The difference in potency is significantly less pronounced when measured in the murine 7TD1 hybridoma growth factor assay and the human hepatoma HepG2 bioassay due to time-dependent dissociation at 37 degrees C of IL-6 dimers into active monomers. The increased binding affinity of IL-6D appears to be due to its ability to cross-link two sIL-6R molecules on the biosensor surface. Studies of the IL-6 ternary complex formation demonstrated that the reduced biological potency of IL-6D resulted from a decreased ability of the IL-6D (sIL-6R)2 complex to couple with the soluble portion of gp130. These data imply that IL-6-induced dimerization of sIL-6R is not the driving force in promoting formation of the hexameric (IL-6 IL-6R gp130)2 complex. A model is presented whereby the trimeric complex of IL-6R, gp130, and IL-6M forms before the functional hexamer. Due to its increased affinity for the IL-6R but its decreased ability to couple with gp130, we suggest that a stable IL-6 dimer may be an efficient IL-6 antagonist.

Equilibrium denaturation of recombinant murine interleukin-6: effect of pH, denaturants, and salt on formation of folding intermediates

The equilibrium denaturation of an Escherichia coli-derived recombinant murine interleukin-6 (mIL-6) was studied using fluorescence and circular dichroism spectroscopy. The urea-induced unfolding of mIL-6 at pH 4.0 can be described by a two-state unfolding mechanism based on the superimposibility of the CD and fluorescence unfolding transitions. Assuming a two-state mechanism and a linear dependence of the free energy of unfolding on denaturant concentration, a value of 6.9-9.0 kcal/mol was calculated for the free energy of unfolding in the absence of denaturant [delta GU(H2O)]. However, when GuHCl was used as a denaturant at pH 4.0, a biphasic unfolding transition was observed. This unfolding transition has a distinct midpoint occurring at 2.5 M GuHCl, which is indicative of the formation of stable folding intermediates. Similar intermediate folded species were also observed at pH 7.4 when either urea or GuHCl were used as denaturants. The intermediate folded states of mIL-6 exhibited a tendency to aggregate, as judged by the concentration dependence of their fluorescence characteristics. The fluorescence emission maximum of mIL-6 at pH 7.4 in the presence of 1.5 M GuHCl, for example, was blue-shifted from 343 nm at a protein concentration of 50 micrograms/mL to 336 nm at 500 micrograms/mL. Intermediate formation at pH 4.0, using 10 mM sodium acetate buffer and urea as the denaturant, was facilitated by the addition of 0.4 and 0.8 M salt, where the salt was either NaCl or GuHCl.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of solute multivalence on the evaluation of binding constants by biosensor technology: studies with concanavalin A and interleukin-6 as partitioning proteins

The interaction of concanavalin A with immobilized carboxylmethyldextran has been characterized by means of a biosensor based on surface plasmon resonance detection. Adsorption and desorption of this bivalent lectin to/from the biosensor surface are shown to deviate markedly from pseudo-first-order kinetics, an assumption inherent in the usual kinetic approach to the characterization of interactions by biosensor technology. Similar results for the interaction of a dimeric and hence bivalent form of human interleukin-6 with its receptor immobilized on the biosensor plate support the conclusion that this deviation from pseudo-first-order kinetics originates from multivalence of the partitioning protein. Use of the kinetic approach to characterize the binding of multivalent proteins to immobilized affinity sites on the biosensor chip is therefore precluded because of nonconformity with the model on which the quantitative analysis is based. Instead, an intrinsic binding constant of 2.5 x 10(5) M-1 for the interaction of concanavalin A with the carboxymethylated dextran layer coating the biosensor chip has been obtained by interpreting the equilibrium biosensor responses in terms of expressions developed in the context of quantitative affinity chromatography of multivalent partitioning solutes.

Use of a biosensor with surface plasmon resonance detection for the determination of binding constants: measurement of interleukin-6 binding to the soluble interleukin-6 receptor

The interaction of recombinant human interleukin-6 (IL-6) with the soluble extracellular form of its receptor (sIL-6R) has been characterized by the application of expressions developed for quantitative affinity chromatography to results obtained with a biosensor based on surface plasmon resonance detection. First, the interaction of sIL-6R with IL-6 covalently attached to the biosensor-chip was characterized from the dependence of the surface plasmon resonance response upon the concentration of receptor injected into the biosensor. A binding constant for the interaction between sIL-6R and IL-6 was then determined from the biosensor response observed for mixtures of IL-6 and receptor--a procedure that is shown to provide unequivocal characterization of the competing reaction, irrespective of the model used to describe the biphasic interaction between partitioning receptor and immobilized IL-6. A binding constant of 5 x 10(7) M-1 has been obtained for the interaction of sIL-6R with two equivalent and independent sites on an essentially dimeric IL-6 preparation produced using the pUC vector system, and also for the interaction of sIL-6R with a monomeric IL-6 preparation that was univalent in its interaction with receptor.

Structure-function analysis of human IL-6: identification of two distinct regions that are important for receptor binding

Interleukin-6 (IL-6) is a multifunctional cytokine that plays an important role in host defense. It has been predicted that IL-6 may fold as a 4 alpha-helix bundle structure with up-up-down-down topology. Despite a high degree of sequence similarity (42%) the human and mouse IL-6 polypeptides display distinct species-specific activities. Although human IL-6 (hIL-6) is active in both human and mouse cell assays, mouse IL-6 (mIL-6) is not active on human cells. Previously, we demonstrated that the 5 C-terminal residues of mIL-6 are important for activity, conformation, and stability (Ward LD et al., 1993, Protein Sci 2:1472-1481). To further probe the structure-function relationship of this cytokine, we have constructed several human/mouse IL-6 hybrid molecules. Restriction endonuclease sites were introduced and used to ligate the human and mouse sequences at junction points situated at Leu-62 (Lys-65 in mIL-6) in the putative connecting loop AB between helices A and B, at Arg-113 (Val-117 in mIL-6) at the N-terminal end of helix C, at Lys-150 (Asp-152 in mIL-6) in the connecting loop CD between helices C and D, and at Leu-178 (Thr-180 in mIL-6) in helix D. Hybrid molecules consisting of various combinations of these fragments were constructed, expressed, and purified to homogeneity. The conformational integrity of the IL-6 hybrids was assessed by far-UV CD. Analysis of their biological activity in a human bioassay (using the HepG2 cell line), a mouse bioassay (using the 7TD1 cell line), and receptor binding properties indicates that at least 2 regions of hIL-6, residues 178-184 in helix D and residues 63-113 in the region incorporating part of the putative connecting loop AB through to the beginning of helix C, are critical for efficient binding to the human IL-6 receptor. For human IL-6, it would appear that interactions between residues Ala-180, Leu-181, and Met-184 and residues in the N-terminal region may be critical for maintaining the structure of the molecule; replacement of these residues with the corresponding 3 residues in mouse IL-6 correlated with a significant loss of alpha-helical content and a 200-fold reduction in activity in the mouse bioassay. A homology model of mIL-6 based on the X-ray structure of human granulocyte colony-stimulating factor is presented.

Energy transfer studies of the distances between the colchicine, ruthenium red, and bisANS binding sites on calf brain tubulin

Fluorescence energy transfer experiments were performed in order to measure the spatial separation between the colchine and Ruthenium Red binding sites, the high-affinity bisANS and Ruthenium Red sites, and the allocolchicine and high-affinity bisANS sites on calf brain tubulin. Energy transfer was observed between both colchicine and allocolchicine and Ruthenium Red, resulting in a distance of 40-45 A between these sites on the tubulin molecule. No detectable energy transfer could be observed when allocolchicine was used as fluorescence donor and bisANS as acceptor or when bisANS was used as donor and Ruthenium Red as acceptor. This indicates that the distance of separation between the allocolchicine and bisANS sites is greater than 50 A, while that between the bisANS and Ruthenium Red sites is greater than 72 A. On the basis of these and previous distance measurements (Ward & Timasheff, 1988), two triangles of binding sites have been defined (colchicine-bisANS-E-site and colchicine-bisANS-Ruthenium Red). Since the dihedral angle between them is not known, a schematic model has been drawn with all the sites located in a single plane.(ABSTRACT TRUNCATED AT 250 WORDS)

Cooperative multiple binding of bisANS and daunomycin to tubulin

The binding of daunomycin and bisANS to tubulin was studied by direct equilibrium techniques. Both ligands generated abnormal Scatchard plots. Their concave-downward nature indicated positive cooperativity. The data conform to tubulin possessing ca. 35 daunomycin binding sites with a binding constant of 570-1430 M-1. The binding of bisANS is characterized by 1 strong binding site (KA = 4.5 x 10(5) M-1) and 40-50 lower affinity sites. Hill plots of both showed low degrees of cooperativity (m = 1.8 for daunomycin and 2.3 for bisANS). A detailed analysis was carried out of the cooperativity of binding of daunomycin to tubulin. Concentration differences spectra and sedimentation velocity analysis of daunomycin showed that this molecule undergoes self-association in the drug concentration range used in the binding study. The low level of polymerization (approximately tetramer), however, indicated that this could not be the source of the observed cooperativity between 35 molecules. Both the shape and concentration dependence of the daunomycin concentration difference spectra were strikingly similar to those generated on the binding of daunomycin to tubulin, which indicates the stacking of daunomycin in both cases. The observed Scatchard plot of the binding was found to be consistent with a process that involves in part ligand-ligand interactions when complexed to tubulin. Examination of the binding of bisANS in the presence of daunomycin revealed a strong increase of bisANS binding to tubulin, which suggests a loosening of tubulin structure with the exposure of new sites as these ligands bind. The mutual interaction between the two ligands in dilute solution was demonstrated by difference spectroscopy.(ABSTRACT TRUNCATED AT 250 WORDS)

High affinity interleukin-6 receptor is a hexameric complex consisting of two molecules each of interleukin-6, interleukin-6 receptor, and gp-130

The high affinity human interleukin-6 (IL-6) receptor complex consists of IL-6 and two membrane-associated receptor components, the IL-6 receptor (alpha-subunit) and the high affinity converter and signal transducing molecule, gp-130 (beta-subunit). Recombinant IL-6 and the extracellular ("soluble") components of the IL-6 receptor (sIL-6R) and gp-130 (sgp-130) have been prepared in order to investigate the stoichiometry and binding of these components in the low affinity (IL-6.sIL-6R) and high affinity (IL-6.sIL-6R.sgp-130) IL-6 receptor complexes. Using a combination of size-exclusion chromatography and analytical ultracentrifugation analysis, in the low affinity receptor complex, IL-6 was shown to bind sIL-6R in a stoichiometric ratio of 1:1, whereas the high affinity ternary complex is hexameric consisting of two molecules each of IL-6, sIL-6R, and sgp-130. This is the first direct demonstration of a higher order arrangement for receptor cytokine interactions that exhibit both high and low affinity complexes.

Two-dimensional electrophoretic analysis of proteins expressed by normal and cancerous human crypts: application of mass spectrometry to peptide-mass fingerprinting

Protein patterns of normal human colonic crypts, isolated from different regions of the large intestine, and several colorectal cancer cell lines were compared using two-dimensional electrophoresis gels (2-DE). As detected by intrinsic radiolabeling and Coomassie Brilliant Blue staining, the protein patterns for normal crypts isolated from the ascending, and descending, regions of the colon and the rectum, were almost (> 95%) identical. While 75-80% of the protein spots from normal crypts and the colorectal cancer cell line (LIM 1863), a cell line that grows as organoids and differentiates spontaneously into crypt-like structures in vitro, can be matched, the relative expression levels of a large number of proteins differ. At least two protein spots (undetectable in the protein pattern from normal cells), proteins a (M(r) approximately 18,000, pI 6.7-6.9) and b (M(r) approximately 24,000, pI 5.9-6.0), were detected in the 2-DE gel protein pattern in the three cell lines LIM 1863, LIM 1215 and LIM 1899. The identity of these proteins is not yet known and further studies are required before they can be considered as potential colon tumor markers. Approximately 60% of the cellular proteins from LIM 1215 cells, a colon carcinoma cell line that exhibits many properties associated with columnar cells, can be matched with LIM 1863 cells. The results presented here represent an initial phase in our efforts to develop a comprehensive protein database for normal human colon cells and several colorectal cancer cell lines. While our initial protein identification relied on microsequencing methodologies, we are presently evaluating peptide-mass fingerprinting, utilizing capillary reversed-phase high-performance liquid chromatography (RP-HPLC) and electrospray mass spectrometry, as a means for rapid identification of proteins at subpicomole levels. Using this approach, protein #3 (M(r) approximately 66,000, pI 6.2) was identified as heat shock protein 60 from as few as seven tryptic peptide masses when they were screened against the molecular weight search (MOWSE) peptide-mass database.

Specific covalent modification of the tryptophan residues in murine interleukin-6. Effect on biological activity and conformational stability

Modification of recombinant murine interleukin-6 (mIL-6) with the tryptophan-specific reagent 2-nitrophenylsulfenyl chloride under mild acidic conditions, 0.1 M sodium acetate, pH 3.5, yielded a derivative containing 2.02 mol 2-nitrophenylsulfenyl tryptophan/mol protein. The sites of modification were identified as Trp36 and Trp160. No detectable side reactions occurred on other amino acids in the molecule, as indicated by the combination of endoproteinase Asp-N peptide mapping, Edman degradation and electrospray mass spectrometry. Sulfenylation of the two tryptophan residues in mIL-6 caused a 50% reduction in both the biological activity in the murine-hybridoma-growth-factor assay using 7TD1 cells and receptor-binding affinity to mIL-6 receptors. Sulfenylation of mIL-6 did not significantly affect the overall conformation of the protein as measured by farultraviolet circular dichroism and binding to the neutralizing anti-mIL-6 mAb 6B4. The sulfenylated protein was, however, significantly less stable [delta delta G(H2O) = 3.98 kJ/mol] than unmodified mIL-6 as measured by urea-gradient gel electrophoresis.

Role of the C-terminus in the activity, conformation, and stability of interleukin-6

Two murine interleukin-6 (mIL-6) variants were constructed using the polymerase chain reaction (PCR), one lacking the last five residues (183-187) at the C-terminus (pMC5) and another with the last five residues of mIL-6 substituted by the corresponding residues of human IL-6 (pMC5H). The growth stimulatory activity of pMC5 on the mouse hybridoma cell line 7TD1 was < 0.05% of mIL-6, whereas pMC5H and mIL-6 were equipotent. The loss of biological activity of pMC5 correlated with its negligible receptor binding affinity on 7TD1 cells, while the binding of pMC5H was comparable to that of mIL-6. Both pMC5 and pMC5H, like mIL-6, failed to interact with recombinant soluble human IL-6 receptor when assayed by surface plasmon resonance-based biosensor analysis. These studies suggest that the C-terminal seven amino acids of human IL-6, alone, do not define species specificity for receptor binding. A variety of biophysical techniques, as well as the binding of a conformational-specific monoclonal antibody, indicated that the global fold of the mIL-6 variants was similar to that of mIL-6, although small changes in the NMR spectra, particularly for pMC5, were observed. Some of these changes involved residues widely separated in the primary structure. For instance, interactions involving Tyr-22 were influenced by the C-terminal amino acids suggesting that the N- and C-termini of mIL-6 are in close proximity. Equilibrium unfolding experiments indicated that pMC5 was 0.8 kcal/mol less stable than mIL-6, whereas pMC5H was 1.4 kcal/mol more stable. These studies emphasize the structural importance of the C-terminal amino acids of IL-6 and suggest that truncation or mutation of this region could lead to small but significant alterations in other regions of the molecule.

Proteins of the Golgi apparatus. Purification to homogeneity, N-terminal sequence, and unusually large Stokes radius of the membrane-bound form of UDP-galactose:N-acetylglucosamine beta 1-4galactosyltransferase from rat liver

The Golgi marker enzyme, UDP-galactose:N-acetylglucosamine beta 1-4galactosyltransferase (beta 1-4GalT) was purified 44300-fold in its intact, membrane-bound form from rat liver membranes. The protein was isolated from detergent extracts as a high-M(r) form, having a Stokes radius approximating a globular protein of M(r) 440,000. It is comprised of a single protein component as observed on SDS/polyacrylamide gels, having an M(r) near 51,000, and does not have intermolecular disulfide cross-links. N-terminal sequencing of the enzyme demonstrated that it contains an N-terminal hydrophobic stretch deduced previously from cDNA encoding for the enzyme. Previous studies have indicated that the protein may be translated at either of two AUG sites near the 5' end of the mRNA [Russo, R. N., Shaper, N. L. & Shaper, J. H. (1990) J. Biol. Chem. 265, 3324-3331], giving rise to two polypeptides, one appended with 13 amino acids. In the work described here, evidence was only found for the sequence of the short form, missing a single methionine at the N-terminus. Mild proteolytic treatment cleaved the enzyme, giving rise to low-M(r) forms which were fully catalytically active and which, upon sequencing, were missing a 66-amino-acid stretch from the N-terminus (as compared to the mouse cDNA). Proteolytic treatment was accompanied by conversion of the form having a large Stokes radius to one approximating a globular protein with M(r) near 50,000. The N-terminal stretch appears to contribute to maintenance of the form having a large Stokes radius. This may be the result of interaction with a detergent micelle, dimerization or oligomerization, or interaction with some other large, non-protein molecule, although a detergent exchange still resulted in a form having a large Stokes radius.

Effect of pH and denaturants on the folding and stability of murine interleukin-6

The conformation and stability of a recombinant mouse interleukin-6 (mIL-6) has been investigated by analytical ultracentrifugation, fluorescence spectroscopy, urea-gradient gel electrophoresis, and near- and far-ultraviolet circular dichroism. On decreasing the pH from 8.0 to 4.0, the tryptophan fluorescence of mIL-6 was quenched 40%, the midpoint of the transition occurring at pH 6.9. The change in fluorescence quantum yield was not due to unfolding of the molecule because the conformation of mIL-6, as judged by both urea-gradient gel electrophoresis and CD spectroscopy, was stable over the pH range 2.0-10.0. Sedimentation equilibrium experiments indicated that mIL-6 was monomeric, with a molecular mass of 22,500 Da over the pH range used in these physicochemical studies. Quenching of tryptophan fluorescence (20%) also occurred in the presence of 6 M guanidine hydrochloride upon going from pH 7.4 to 4.0 suggesting that an amino acid residue vicinal in the primary structure to one or both of the two tryptophan residues, Trp-36 and Trp-160, may be partially involved in the quenching of endogenous fluorescence. In this regard, similar results were obtained for a 17-residue synthetic peptide, peptide H1, which corresponds to an N-terminal region of mIL-6 (residues Val-27-Lys-43). The pH-dependent acid quenching of endogenous tryptophan fluorescence of peptide H1 was 30% in the random coil conformation and 60% in the presence of alpha-helix-promoting solvents. Replacement of His-33 with Ala-33 in peptide H1 alleviated a significant portion of the pH-dependent quenching of fluorescence suggesting that the interaction of the imidazole ring of His-33 with the indole ring of Trp-36 is a major determinant responsible for the quenching of the endogenous protein fluorescence of mIL-6.

Preparation of highly purified human myelin oligodendrocyte glycoprotein in quantities sufficient for encephalitogenicity and immunogenicity studies

Myelin oligodendrocyte glycoprotein, (MOG), a quantitatively minor central nervous system (CNS) myelin component, is a candidate target antigen for autoimmune-mediated demyelination. It is a highly hydrophobic protein present in very small amounts in CNS tissue and thereby difficult to purify. Our aim was to devise a purification procedure that would yield sufficient quantities of highly purified MOG to subsequently test its potential encephalitogenic activity, as well as investigate the humoral and cell-mediated responses to this antigen in naturally occurring and experimentally induced autoimmune demyelinating diseases. MOG was purified from human CNS white matter using immunoaffinity chromatography, a procedure that gave a final yield of MOG corresponding to 0.02% total white matter protein. The final product, which migrated as two bands of molecular weight 28 kDa and 58 kDa, was highly pure as shown also by specific reactivity with monoclonal anti-MOG antibodies on immunoblots in the absence of any detectable reactivity with antibodies specific for myelin basic protein, proteolipid protein and myelin-associated glycoprotein. Partial amino acid sequence was obtained from both MOG bands separated by SDS-PAGE and electroblotted onto PVDF. The sequence of the first 17 N-terminal amino acids had approximately 55% homology with the reported rat MOG sequence deduced from the cloned cDNA sequence; small internal sequences obtained showed also very high homology. Our purified MOG preparations have been used to investigate T cell response to MOG by peripheral blood lymphocytes of multiple sclerosis patients and to induce a relapsing remitting demyelinating disease in Lewis rats.

Epidermal growth factor induces serine phosphorylation of stathmin in a human colon carcinoma cell line (LIM 1215)

Changes in protein phosphorylation in the human colon carcinoma cell line LIM 1215 after stimulation with epidermal growth factor (EGF) have been analyzed by two-dimensional gel electrophoresis and phosphoamino acid analysis. In addition to a number of tyrosine-phosphorylated proteins, a family of small proteins (M(r) 19,000-20,000) is maximally phosphorylated on serine within 5 min of EGF stimulation. One member of the family has been purified by a combination of two-dimensional electrophoresis and reversed-phase high performance liquid chromatography and identified by amino acid sequence analysis as stathmin. Although phosphorylation of stathmin has been reported previously in leukemia cells and following stimulation of hemopoietic or lymphoid cells with several mitogenic agents, this is the first report of stathmin phosphorylation in response to EGF.

Identification of canary grass (Phalaris aquatica) pollen allergens by immunoblotting: IgE and IgG antibody-binding studies

The pollen of canary grass, which was introduced as a pasture grass from Europe, is a major allergen in the external environment of southern Australia. Seventeen allergenic fractions of canary grass pollen, ranging in mol. mass from 14 to 100 kDa, have been identified by immunoblotting, using IgE antibodies from sera of 24/30 grass-pollen-allergic subjects. The highest frequency of IgE binding (77%) was to a major 34-kDa fraction (tentatively designated Pha a I). This protein has been partially purified and identified as a group I allergen by immunodepletion experiments, with partially purified Lol p I (from rye-grass pollen), atopic serum, and Lol p I-specific MAb. In addition, microsequencing of the N-terminus of Pha a I showed an amino acid sequence identical to Lol p I. In a separate study, IgE binding to Western blots of Pha a I, Lol p I, and Cyn d I was investigated in 24 sera and found to occur in 19/24, 18/24, and 9/24, respectively. IgE binding to all three major allergens, and to both Pha a I and Lol p I, occurred in 8/24 sera. Our findings suggest that while the N-terminal sequence of Pha a I is identical to Lol p I, there may be specific allergenic epitopes exclusive to this allergen that are important for allergenicity in southern Australia.

Characterization of bovine heparin-binding neurotrophic factor (HBNF): assignment of disulfide bonds

The topology of the disulfides in native heparin-binding neurotrophic factor (HBNF) isolated from bovine brain was studied by proteolytic digestion using trypsin, Asp-N endoproteinase and chymotrypsin and peptide mapping. Disulfide-linked peptides were identified by automated Edman degradation. It has been shown that there are disulfide bonds between Cys15-Cys44, Cys23-Cys53, Cys30-Cys57, Cys67-Cys99 and Cys77-Cys109.

A major binding protein for leukemia inhibitory factor in normal mouse serum: identification as a soluble form of the cellular receptor

A protein that specifically binds leukemia inhibitory factor (LIF) has been isolated from normal mouse serum by using four successive fractionation steps: chromatography on a LIF affinity matrix, anion-exchange chromatography, size-exclusion chromatography, and preparative native gel electrophoresis. The purified LIF-binding protein (LBP) is a glycoprotein with an apparent molecular mass of 90 kDa that specifically binds 125I-labeled murine LIF with an affinity comparable to that of the low-affinity cellular LIF receptor (Kd = 600 pM). N-terminal sequencing has identified this protein as a soluble truncated form of the alpha chain of the cellular LIF receptor. LBP is present in normal mouse serum at high levels (1 microgram/ml) and these levels are elevated in pregnant mice and reduced in neonatal mice. Since normal serum concentrations of LBP can block the biological actions of LIF in culture, LBP may serve as an inhibitor of the systemic effects of locally produced LIF.

Purification and characterization of a recombinant murine interleukin-6. Isolation of N- and C-terminally truncated forms

Murine interleukin-6 (IL-6), when expressed in Escherichia coli using the pUC9 vector, accumulated as insoluble aggregates or 'inclusion bodies'. After selective urea washing of the inclusion bodies, to remove extraneous proteins, murine IL-6 was solubilized with 8 M guanidine hydrochloride and then rapidly purified to homogeneity by gel-permeation chromatography followed by reversed-phase HPLC. It was demonstrated that complete disulfide bond formation in murine IL-6 occurred during the early urea washing/guanidine hydrochloride extraction steps, so no refolding step was required. When fully reduced murine IL-6 was dissolved in 8 M guanidine hydrochloride and allowed to air-oxidize, complete disulfide bond formation, monitored by analytical reversed-phase HPLC, was shown to occur within 13 h at 6 degrees C. About 25 mg pure protein was obtained from 37 g wet cells. This recombinant murine IL-6 had a specific activity in the hybridoma growth factor assay of 2 x 10(8) U/mg, which is equivalent to that of native murine IL-6. During the purification procedure, a number of variant forms of murine IL-6 were isolated and partially characterized. Two of these forms, T1 and T3, were C-terminal deletants of murine IL-6 lacking about 60 and 20 amino acids from the C-terminus, respectively, while the other form, T2, was an N-terminal deletant lacking 37 amino acids from the N-terminus. None of these variant forms of murine IL-6 bound to the murine IL-6 receptor and, consequently, all were inactive in the hybridoma growth factor assay.

Binding of anti-human-interleukin-6 monoclonal antibodies to synthetic peptides of human interleukin-6 studied using surface plasmon resonance

Biosensor technology employing surface plasmon resonance (SPR) detection provides a highly-sensitive (sub ng), non-extrinsic labelling approach for monitoring protein interactions in real-time. We have used this approach to map the binding sites on human interleukin-6 (hIL-6) for a series of anti-hIL-6 monoclonal antibodies (mAbs). Epitopes were localised by monitoring the ability of ten synthetic peptides, spanning the sequence of hIL-6, to inhibit the binding of anti-hIL-6 mAbs to immobilised hIL-6. Peptide P8 (Pro139-Gln153) inhibited binding of anti-IL-6-mAbs 1, 2 and 7. To increase the sensitivity of detection of antibody-synthetic peptide interactions, a procedure was developed for immobilising the synthetic peptides directly to the sensor surface of the SPR instrument. From this study, association equilibrium constants of 2.1 x 10(6)M-1 and 3.6 x 10(4)M-1 were calculated for the mAb7-immobilised P8 and mAb7-free P8 interactions, respectively.

Isolation and characterization of a novel receptor-type protein tyrosine kinase (hek) from a human pre-B cell line

In this report we describe the identification and characterization of a novel tumor-associated receptor-type tyrosine kinase (hek). We produced a monoclonal antibody (III.A4) that detected a novel glycoprotein on the immunizing pre-B cell acute lymphoblastic leukemia cell line (LK63). This antigen was shown to be expressed sporadically on hemopoietic tumor cell lines and on ex vivo tumors. However, using antibody staining, the molecule was undetectable on normal tissues. Further biochemical characterization showed this molecule (hek) to be a phosphoroprotein. This observation taken together with the tumor-associated nature of hek expression suggested that hek might be a receptor-type protein tyrosine kinase. This was demonstrated by affinity purification of hek. In in vitro kinase experiments the purified hek protein was autophosphorylated on tyrosine and also mediated tyrosine phosphorylation of casein. Purified hek was subjected to N-terminal amino acid sequence analysis which showed that hek had a unique N terminus. Amino acid sequence determination of peptides from a V8 protease digest of hek yielded one 21-amino acid stretch of sequence which showed close homology with the eph subfamily of protein tyrosine kinases. These studies show hek to be a novel human tumor-associated protein tyrosine kinase, which by analogy with previously characterized protein tyrosine kinase proto-oncogenes, may have a role in tumorigenesis.

The group III allergen from the house dust mite Dermatophagoides pteronyssinus is a trypsin-like enzyme

Faecally enriched extracts of Dermatophagoides pteronyssinus were shown to contain a trypsin-like enzyme which was allergenic. Chromatofocusing studies revealed the presence of nine major isoforms in D. pteronyssinus, with pI in the range 4 to greater than 8, but only two (range 4-5) in D. farinae. Trypsin isolated from D. pteronyssinus by benzamidine-Sepharose 6B affinity chromatography and gelfiltration was found to be a 31-kDa protein which was enzymatically similar to both invertebrate and vertebrate trypsins. The N-terminal sequence obtained (IVGGEXALAGEXPYQISL) was identical to that reported for the mite allergen Der p III and showed homology with crayfish trypsin and Der f III from D. farinae. Mite trypsin underwent autolysis and the N-terminal sequences of two fragments were found to be ALAGEXPYQI and NNQVXGI respectively. Both showed homology with crayfish trypsin, and the former sequence was identical to residues 7-18 of the native enzyme and Der p III. All isoforms of mite trypsin were showed to be allergenic by radioallergosorbent assay and further studies indicated that the trypsin degradation products were also allergenic. The enzyme was compared with other mite allergens and the rank order of allergenic potency was shown to be: whole mite extract greater than Der p I greater than trypsin. However, all sera from a panel of mite allergic individuals showed IgE reactivity to trypsin, comparable to that seen using whole mite extract and Der p I. These data indicate that mite trypsin is a major allergen corresponding to the previously described allergen, Der p III.