Glucagon Antagonists Research Articles

374-OR: Exercise Training Decreases ß-Cell Senescence in Mice and Humans

Increased β-cell senescence contributes to the development of type 2 diabetes (T2D). Exercise is critical in the treatment of T2D and can attenuate aging-associated cellular changes, but exercise effects on β-cell senescence are unknown. We tested the effects of treadmill running (1h/day for 10 days) on two insulin resistance models: high-fat diet and insulin receptor antagonist (S961). Exercise improved glucose responsiveness and decreased senescence markers (SA-βGal activity, p21Cip1 and p16Ink4a mRNA and protein levels). RNAseq from pancreatic islets of exercised mice revealed decreased expression of senescence effector genes and senescence associated secretory phenotype factors. Exercise increased AMPK activity in islets as assessed by alpha catalytic subunit phosphorylation. Islets from sedentary mice cultured for 2 days with serum from exercised mice showed decreased senescence, suggesting a circulatory factor was responsible for these effects. Pathway analysis of RNASeq revealed that exercise upregulated glucagon type ligand receptors. Glucagon treatment of mouse and human islets activated AMPK and decreased senescence in β-cells, an affect attenuated by an AMPK inhibitor (compound C). Exercised mice treated with a glucagon antagonist (adomeglivant) blocked AMPK phosphorylation and increased p21Cip1 and p16Ink4. Exercise increased nuclear translocation of the AMPK substrate NRF2 in mouse islets while downregulation of Nrf2 with siRNA in MIN6 cells increased transcription of p16Ink4a, suggesting a potential mechanism linking exercise, AMPK activation and downregulation of β-cell senescence. Treatment of human donor islets with serum obtained pre- and post-exercise training for 10 weeks in people with T2D showed that training activated AMPK and decreased senescence markers. These findings demonstrate that exercise training decreases β-cell senescence and suggest that this important response to exercise occurs through circulating factors mediating an AMPK-dependent pathway. Disclosure P.Carapeto: None. J.Kahng: None. A.T.Alves wagner: None. R.J.W.Middelbeek: Research Support; Novo Nordisk. M.F.Hirshman: Stock/Shareholder; Abbott, AbbVie Inc., Amgen Inc., Colgate-Palmolive, Eli Lilly and Company, Medtronic. G.A.Rutter: Consultant; Sun Pharmaceutical Industries Ltd. L.Goodyear: None. C.Aguayo-mazzucato: None. Funding Joslin Diabetes Center (to C.A-M.); Richard and Susan Smith Family Foundation; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-Brasil (001)

Glucagon 100 years. Important, but still enigmatic

Glucagon was discovered in 1923 as a contaminant of early insulin preparations, and its hormonal status was not established until its structure was established in the 1950 s and when the first radioimmunoassay was developed by Roger Unger, providing information about its secretion. Its role in hepatic glucose production was soon established and it was proposed as an essential factor in diabetic hyperglycemia. However, even today a number of issues remain unsolved. For instance, the assays for glucagon are not straightforward, although the development of sandwich ELISAs allowed reasonably accurate measurements also in rodents. The tools for evaluation of glucagon physiology include pancreatectomy, but studies in both humans and experimental animals pointed towards extrapancreatic sources of glucagon. It was demonstrated that glucagon receptor knockout animals do not develop diabetes upon destruction of their beta cells with streptozotocin. However, in patients with type 1 diabetes, glucagon antagonists do not normalize glucose levels; but antagonists do lower glucose levels in patients with in type 2 diabetes. Recent studies in animals and humans have confirmed the essential role of glucagon in glucose metabolism, but have suggested that it may be at least equally important for amino acid and lipid metabolism. In spite of the 100 years, glucagon research is very much alive.

Regulation of Hepatic Lipid and Glucose Metabolism by INSP3R1.

With the rising epidemics of obesity and nonalcoholic fatty liver disease (NAFLD) and its downstream consequences including steatohepatitis, cirrhosis, and type 2 diabetes in the U.S. and worldwide, new therapeutic approaches are urgently needed to treat these devastating conditions. Glucagon, known for a century to be a glucose-raising hormone and clearly demonstrated to contribute to fasting and postprandial hyperglycemia in both type 1 and type 2 diabetes, represents an unlikely target to improve health in those with metabolic syndrome. However, recent work from our group and others' identifies an unexpected role for glucagon as a potential means of treating NAFLD, improving insulin sensitivity, and improving the lipid profile. We propose a unifying, calcium-dependent mechanism for glucagon's effects both to stimulate hepatic gluconeogenesis and to enhance hepatic mitochondrial oxidation: signaling through the inositol 1,4,5-trisphosphate receptor type 1 (INSP3R1), glucagon activates phospholipase C (PKC)/protein kinase A (PKA) signaling to enhance adipose triglyceride lipase (ATGL)-dependent intrahepatic lipolysis and, in turn, increase cytosolic gluconeogenesis by allosteric activation of pyruvate carboxylase. Simultaneously in the mitochondria, calcium transferred through mitochondria-associated membranes activates several dehydrogenases in the tricarboxylic acid cycle, correlated with an increase in mitochondrial energy expenditure and reduction in ectopic lipid. This model suggests that short-term, cyclic treatment with glucagon or other INSP3R1 antagonists could hold promise as a means to reset lipid homeostasis in patients with NAFLD.

Synthesis of 2-acetal-1,3-enynes by Sonogashira reaction of bromovinyl acetals with alkynes: application to the formal synthesis of a glucagon antagonist

The preparation of functionalized 1,3-enynes bearing an acetal moiety at the 2-position has been studied through Sonogashira reaction of bromovinyl acetals with various alkyl- and aryl-substituted terminal alkynes.

Applications substituted 2-aminothiophenes in drug design

Highly substituted thiophene derivatives are important heterocycles found in numerous biologically active compounds. Title compounds are attractive derivatives because their applications in pharmaceuticals, agriculture and pesticides. They exhibit antimicrobial activity against various Gram(+) and Gram(-) bacteria and fungi. Many of these molecules act as allosteric enhancers of A1-adenosine receptor, glucagon antagonists as well as antioxidant and anti-inflammatory agents.

Perspective on diagnosis and treatment of congenital hyperinsulinism

Congenital hyperinsulinism (CHI) is the most frequent cause of persistent hypoglycemia in infancy, and it is a rare genetic disorder characterized by severe hypoglycemia caused by inappropriate insulin secretion by pancreatic β-cells.The clinical presentation, histology, genetics and response to medical treatment are of genetic heterogeneity.Appropriate treatment is critically important as profound and repeated episodes of hypoglycemia often cause severe brain damage.Based on the biochemical profiles, clinical diagnosis is relative easier to be established, however, the genetic basis is only found in approximately 45%-55% of patients.In terms of treatment, Diazoxide is recommended as first-line treatment for all patients[5-20 mg/(kg·d)]. In patients unresponsive to Diazoxide, if genetic result confirms a monoallelic, recessive paternally-inherited mutation in ABCC8 or KCNJ11, and 18F-fluorodihydroxyphenylalanine-positron emission tomography-computed tomography scan indicates the lesion is located in the body or tail of the pancreas, surgical treatment is recommended.And for the other patients, subcutaneous octreotide, intravenous glucagon, or oral calcium antagonist should be sequentially attempted in order to minimize the need for near-total/subtotal pancreatectomy. Key words: Congenital hyperinsulinism; Insulin; Hypoglycemia; Treatment; Follow-up

Studies on Glucagon Receptor and Antagonists of Glucagon Receptor for the Management of Diabetes Mellitus

Glucagon receptor plays an important role in the glucose homeostasis and thus is drug target for the management of hyperglycemia in type-2 diabetes mellitus. The suppression of glucagon secretion from the alpha-cells is the key to control hyperglycemic condition. The identification of non-peptide antagonists of glucagon receptor is an effective therapeutic approach to inhibit the glucagon secretion to achieve normal glucose index.

Balanced Coagonist of GLP-1 and Glucagon Receptors Corrects Dyslipidemia by Improving FGF21 Sensitivity in Hamster Model.

Hyperlipidemia is often associated with obesity and diabetes, and can lead to serious complications like atherosclerosis and fatty liver disease. Coagonist of GLP-1 and glucagon receptors is a therapy under clinical investigation for treatment of obesity and diabetes. In this study, we have characterized the mechanism of hypolipidemic effect of a balanced coagonist using high cholesterol-fed hamsters. Tyloxapol-induced hypertriglyceridemia, lipolysis in adipose tissue, and bile homeostasis were assessed after repeated dose treatment of the coagonist of GLP-1 and glucagon receptors (Aib2 C24 chimera 2, SC). Antagonists of GLP-1, glucagon, and FGF21 receptors were coadministered, and FGF21 sensitivity was determined in liver and adipose tissue. Repeated dose treatment of coagonist reduced cholesterol and increased FGF21 in blood and liver. Coagonist treatment reduced hepatic triglyceride secretion, increased lipolysis and reduced body weight. Antagonism of GLP-1 and glucagon receptors partially blocked the effect of the coagonist on lipid metabolism in circulation and liver, while FGF21 receptor antagonist completely abolished it. Glucagon and GLP-1 receptors antagonists blocked the action of coagonist on cholesterol excretion and bile flow in liver, but FGF21 antagonist was not effective. Treatment with the coagonist increased expression of FGF21, FGF21R and cofactor ßKlotho in liver and adipose. In conclusion, coagonist of GLP-1 and glucagon receptors improved lipid metabolism in liver of dyslipidemic hamsters. This effect is partially mediated by GLP-1 and glucagon receptors, and the improved FGF21 sensitivity could be the mechanism of hypolipidemic action of the coagonist of GLP-1/glucagon receptors.

A computer model simulating human glucose absorption and metabolism in health and metabolic disease states

A computer model designed to simulate integrated glucose-dependent changes in splanchnic blood flow with small intestinal glucose absorption, hormonal and incretin circulation and hepatic and systemic metabolism in health and metabolic diseases e.g. non-alcoholic fatty liver disease, (NAFLD), non-alcoholic steatohepatitis, (NASH) and type 2 diabetes mellitus, (T2DM) demonstrates how when glucagon-like peptide-1, (GLP-1) is synchronously released into the splanchnic blood during intestinal glucose absorption, it stimulates superior mesenteric arterial (SMA) blood flow and by increasing passive intestinal glucose absorption, harmonizes absorption with its distribution and metabolism. GLP-1 also synergises insulin-dependent net hepatic glucose uptake (NHGU). When GLP-1 secretion is deficient post-prandial SMA blood flow is not increased and as NHGU is also reduced, hyperglycaemia follows. Portal venous glucose concentration is also raised, thereby retarding the passive component of intestinal glucose absorption. Increased pre-hepatic sinusoidal resistance combined with portal hypertension leading to opening of intrahepatic portosystemic collateral vessels are NASH-related mechanical defects that alter the balance between splanchnic and systemic distributions of glucose, hormones and incretins.The model reveals the latent contribution of portosystemic shunting in development of metabolic disease. This diverts splanchnic blood content away from the hepatic sinuses to the systemic circulation, particularly during the glucose absorptive phase of digestion, resulting in inappropriate increases in insulin-dependent systemic glucose metabolism. This hastens onset of hypoglycaemia and thence hyperglucagonaemia. The model reveals that low rates of GLP-1 secretion, frequently associated with T2DM and NASH, may be also be caused by splanchnic hypoglycaemia, rather than to intrinsic loss of incretin secretory capacity. These findings may have therapeutic implications on GLP-1 agonist or glucagon antagonist usage.

The Role of Glucagon in the Pathophysiology and Management of Diabetes

There is general recognition that insulin and glucagon are the main hormones involved in the pathophysiology of diabetes, but the role of glucagon in diabetes is complex and in some circumstances controversial. The increasing appreciation of the role of glucagon in currently used hypoglycemic agents and the ongoing development of glucagon-targeted therapies underscores glucagon's important contribution in optimizing diabetes management. The current review provides a background on glucagon physiology and pathophysiology and an update for investigators, endocrinologists, and other healthcare providers on glucagon-modulating therapies. A literature review was conducted utilizing published literature in PubMed and AccessMedicine including the years 1922-2015 using the following key words: glucagon, bihormonal, diabetes mellitus, glucagon antagonists, glucagon-targeted therapies. Glucagon is a counterregulatory hormone that promotes hepatic glucose production, thus preventing hypoglycemia in normal physiology. In patients with diabetes mellitus, glucagon secretion may be unregulated, which contributes to problems with glucose homeostasis. Several of the most effective therapies for diabetes have been found to suppress glucagon secretion or action, which may contribute to their success. Additionally, glucagon-specific targeted therapies, such as glucagon receptor antagonists, are being studied at a basic and clinical level. Glucagon plays an important role in contributing to hyperglycemia in patients with diabetes. Utilizing hypoglycemic agents that decrease glucagon secretion or inhibit glucagon action can help improve glycemic control, making these agents a valuable resource in diabetes therapy.

A computer model simulating human glucose absorption and metabolism in health and metabolic disease states.

A computer model designed to simulate integrated glucose-dependent changes in splanchnic blood flow with small intestinal glucose absorption, hormonal and incretin circulation and hepatic and systemic metabolism in health and metabolic diseases e.g. non-alcoholic fatty liver disease, (NAFLD), non-alcoholic steatohepatitis, (NASH) and type 2 diabetes mellitus, (T2DM) demonstrates how when glucagon-like peptide-1, (GLP-1) is synchronously released into the splanchnic blood during intestinal glucose absorption, it stimulates superior mesenteric arterial (SMA) blood flow and by increasing passive intestinal glucose absorption, harmonizes absorption with its distribution and metabolism. GLP-1 also synergises insulin-dependent net hepatic glucose uptake (NHGU). When GLP-1 secretion is deficient post-prandial SMA blood flow is not increased and as NHGU is also reduced, hyperglycaemia follows. Portal venous glucose concentration is also raised, thereby retarding the passive component of intestinal glucose absorption. Increased pre-hepatic sinusoidal resistance combined with portal hypertension leading to opening of intrahepatic portosystemic collateral vessels are NASH-related mechanical defects that alter the balance between splanchnic and systemic distributions of glucose, hormones and incretins.The model reveals the latent contribution of portosystemic shunting in development of metabolic disease. This diverts splanchnic blood content away from the hepatic sinuses to the systemic circulation, particularly during the glucose absorptive phase of digestion, resulting in inappropriate increases in insulin-dependent systemic glucose metabolism. This hastens onset of hypoglycaemia and thence hyperglucagonaemia. The model reveals that low rates of GLP-1 secretion, frequently associated with T2DM and NASH, may be also be caused by splanchnic hypoglycaemia, rather than to intrinsic loss of incretin secretory capacity. These findings may have therapeutic implications on GLP-1 agonist or glucagon antagonist usage.

Inhibiting or antagonizing glucagon: making progress in diabetes care.

Absolute or relative hyperglucagonaemia has been recognized for years in all experimental or clinical forms of diabetes. It has been suggested that excess secretion of glucagon by the islet α cells is a direct consequence of intra-islet insulin secretory defects. Recent studies have shown that knockout of the glucagon receptor or administration of a monoclonal specific glucagon receptor antibody make insulin-deficient type 1 diabetic rodents thrive without insulin. These observations suggest that glucagon plays an essential role in the pathophysiology of diabetes and that targeting the α cell and glucagon are innovative approaches in the management of diabetes. Despite active research and identification of promising compounds, no one selective glucagon antagonist is presently used in the treatment of diabetes. Interestingly, besides insulin, several drugs used today in the management of diabetes appear to exert their effects, in part, by inhibiting glucagon secretion (glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, α-glucosidase inhibitors and, possibly, sulphonylureas) or glucagon action (metformin). The potential risks associated with total glucagon suppression include α-cell hyperplasia, increased mass of the pancreas, increased susceptibility to hepatosteatosis and hepatocellular injury and increased risk of hypoglycaemia, and these should be considered in the search and development of new compounds reducing glucagon receptor signalling. More than 40 years after its initial description, hyperglucagonaemia in diabetes can no longer be ignored or minimized, and its correction represents an attractive way to improve diabetes management.

Ablation of glucagon receptor signaling by peptide-based glucagon antagonists improves glucose tolerance in high fat fed mice

Modification to the structure of glucagon has provided a number of glucagon receptor antagonists with possible therapeutic application for diabetes. These novel peptide analogs include desHis1Pro4Glu9-glucagon and desHis1Pro4Glu9(Lys30PAL)-glucagon. This study has evaluated the metabolic benefits of once daily administration of desHis1Pro4Glu9-glucagon and desHis1Pro4Glu9(Lys30PAL)-glucagon in high fat (45%) fed mice for 15 days. Administration of desHis1Pro4Glu9-glucagon and desHis1Pro4Glu9(Lys30PAL)-glucagon had no significant effect on body weight, food intake or circulating glucose concentrations during the treatment period. However, both peptides significantly (P<0.05 to P<0.01) reduced circulating plasma insulin concentrations from day 6 onwards. Oral glucose tolerance and insulin sensitivity, as assessed by exogenous insulin administration, were significantly (P<0.01 to P<0.001) improved by both desHis1Pro4Glu9-glucagon and desHis1Pro4Glu9(Lys30PAL)-glucagon. These metabolic benefits were accompanied by significantly (P<0.01) increased pancreatic insulin stores. No significant differences in blood triacylglycerol or cholesterol levels were noted with desHis1Pro4Glu9-glucagon, however desHis1Pro4Glu9(Lys30PAL)-glucagon treatment significantly (P<0.01) increased HDL-cholesterol levels. Glucagon-mediated elevations of glucose and insulin were effectively (P<0.01 to P<0.001) annulled in both treatment groups on day 15. Interestingly, glucose levels during an intraperitoneal glucose tolerance test were not altered by either desHis1Pro4Glu9-glucagon or desHis1Pro4Glu9(Lys30PAL)-glucagon treatment. These data provide further evidence that glucagon antagonism could provide an effective means of treating T2DM.

A DPP-IV-resistant triple-acting agonist of GIP, GLP-1 and glucagon receptors with potent glucose-lowering and insulinotropic actions in high-fat-fed mice

We designed a chemically modified, enzyme-resistant peptide with triple-acting properties based on human glucagon with amino acid substitutions aligned to strategic positions in the sequence of glucose-dependent insulinotropic polypeptide (GIP). Y(1)-dA(2)-I(12)-N(17)-V(18)-I(27)-G(28,29)-glucagon (termed YAG-glucagon) was incubated with dipeptidylpeptidase IV (DPP-IV) to assess stability, BRIN-BD11 cells to evaluate insulin secretion, and receptor-transfected cells to examine cAMP production. Acute glucose-lowering and insulinotropic properties of YAG-glucagon were assessed in National Institutes of Health (NIH) Swiss mice, while longer-term actions on glucose homeostasis, insulin secretion, food intake and body weight were examined in high-fat-fed mice. YAG-glucagon was resistant to DPP-IV, increased in vitro insulin secretion (1.5-3-fold; p < 0.001) and stimulated cAMP production in GIP receptor-, glucagon-like peptide-1 (GLP-1) receptor- and glucagon receptor-transfected cells. Plasma glucose levels were significantly reduced (by 51%; p < 0.01) and insulin concentrations increased (1.2-fold; p < 0.01) after acute injection of YAG-glucagon in NIH Swiss mice. Acute actions were countered by established GIP, GLP-1 and glucagon antagonists. In high-fat-fed mice, twice-daily administration of YAG-glucagon for 14 days reduced plasma glucose (40% reduction; p < 0.01) and increased plasma insulin concentrations (1.8-fold; p < 0.05). Glycaemic responses were markedly improved (19-48% reduction; p < 0.05) and insulin secretion enhanced (1.5-fold; p < 0.05) after a glucose load, which were independent of changes in insulin sensitivity, food intake and body weight. YAG-glucagon is a DPP-IV-resistant triple agonist of GIP, GLP-1 and glucagon receptors and exhibits beneficial biological properties suggesting that it may hold promise for treatment of type 2 diabetes.

Human Monoclonal Antibodies against Glucagon Receptor Improve Glucose Homeostasis by Suppression of Hepatic Glucose Output in Diet-Induced Obese Mice

AimGlucagon is an essential regulator of hepatic glucose production (HGP), which provides an alternative therapeutic target for managing type 2 diabetes with glucagon antagonists. We studied the effect of a novel human monoclonal antibody against glucagon receptor (GCGR), NPB112, on glucose homeostasis in diet-induced obese (DIO) mice.MethodsThe glucose-lowering efficacy and safety of NPB112 were investigated in DIO mice with human GCGR for 11 weeks, and a hyperinsulinemic-euglycemic clamp study was conducted to measure HGP.ResultsSingle intraperitoneal injection of NPB112 with 5 mg/kg effectively decreased blood glucose levels in DIO mice for 5 days. A significant reduction in blood glucose was observed in DIO mice treated with NPB112 at a dose ≥5 mg/kg for 6 weeks, and its glucose-lowering effect was dose-dependent. Long-term administration of NPB112 also caused a mild 29% elevation in glucagon level, which was returned to the normal range after discontinuation of treatment. The clamp study showed that DIO mice injected with NPB112 at 5 mg/kg were more insulin sensitive than control mice, indicating amelioration of insulin resistance by treatment with NPB112. DIO mice treated with NPB112 showed a significant improvement in the ability of insulin to suppress HGP, showing a 33% suppression (from 8.3 mg/kg/min to 5.6 mg/kg/min) compared to the 2% suppression (from 9.8 mg/kg/min to 9.6 mg/kg/min) in control mice. In addition, no hypoglycemia or adverse effect was observed during the treatment.ConclusionsA novel human monoclonal GCGR antibody, NPB112, effectively lowered the glucose level in diabetic animal models with mild and reversible hyperglucagonemia. Suppression of excess HGP with NPB112 may be a promising therapeutic modality for the treatment of type 2 diabetes.

Glucagon antagonism as a potential therapeutic target in type 2 diabetes

Glucagon is a hormone secreted from the alpha cells of the pancreatic islets. Through its effect on hepatic glucose production (HGP), glucagon plays a central role in the regulation of glucose homeostasis. In patients with type 2 diabetes mellitus (T2DM), abnormal regulation of glucagon secretion has been implicated in the development of fasting and postprandial hyperglycaemia. Therefore, new therapeutic agents based on antagonizing glucagon action, and hence blockade of glucagon-induced HGP, could be effective in lowering both fasting and postprandial hyperglycaemia in patients with T2DM. This review focuses on the mechanism of action, safety and efficacy of glucagon antagonists in the treatment of T2DM and discusses the challenges associated with this new potential antidiabetic treatment modality.

PKC stimulated by glucagon decreases UT-A1 urea transporter expression in rat IMCD

It is well-known that glucagon increases fractional excretion of urea in rats after a protein intravenous infusion. This effect was investigated by using: (a) in vitro microperfusion technique to measure [(14)C]-urea permeability (Pu x 10(-5)cm/s) in inner medullary collecting ducts (IMCD) from normal rats in the presence of 10(-7)M of glucagon and in the absence of vasopressin and (b) immunoblot techniques to determine urea transporter expression in tubule suspension incubated with the same glucagon concentration. Seven groups of IMCDs (n = 47) were studied. Our results revealed that: (a) glucagon decreased urea reabsorption dose-dependently; (b) the glucagon antagonist des-His(1)-[Glu(9)], blocked the glucagon action but not vasopressin action; (c) the phorbol myristate acetate, decreased urea reabsorption but (d) staurosporin, restored its effect; e) staurosporin decreased glucagon action, and finally, (f) glucagon decreased UT-A1 expression. We can conclude that glucagon reduces UT-A1 expression via a glucagon receptor by stimulating PKC.

Expression of glucagon receptors in tetracycline‐inducible HEK293S GnT1− stable cell lines: An approach toward purification of receptor protein for structural studies

Glucagon is a 29-amino acid polypeptide hormone secreted by pancreatic A cells. Together with insulin, it is an important regulator of glucose metabolism. Type 2 diabetes is characterized by reduced insulin secretion from pancreatic B cells and increased glucose output by the liver which has been attributed to abnormally elevated levels of glucagon. The glucagon receptor (GR) is a member of family B G protein-coupled receptors, ligands for which are peptides composed of 30-40 amino acids. The impetus for studying how glucagon interacts with its membrane receptor is to gain insight into the mechanism of glucagon action in normal physiology as well as in diabetes mellitus. The principal approach toward this goal is to design and synthesize antagonists of glucagon that will bind with high affinity to the GR but will not activate it. Site-directed mutagenesis of the GR has provided some insight into the interactions between glucagon and GR. The rational design of potent antagonists has been hampered by the lack of structural information on receptor-bound glucagon. To obtain adequate amounts of receptor protein for structural studies, a tetracycline-inducible HEK293S GnT1(-) cell line that stably expresses human GR at high-levels was developed. The recombinant receptor protein was characterized, solubilized, and isolated by one-step affinity chromatography. This report describes a feasible approach for the preparation of human GR and other family B GPCRs in the quantities required for structural studies.

Merrifield laboratory: Last member standing

Merrifield laboratory: Last member standing

Bruce Merrifield's contribution to antimicrobial peptide research

Although within the scientific community at large Bruce Merrifield is and will remain celebrated for the pivotal discovery and dedicated crafting of solid phase peptide synthesis methodology, there are also other areas where his unique scientific acumen was applied to with distinctive success. Among them, those of glucagon antagonists and antimicrobial peptides are arguably the better known. Over my 25 year-long relationship with Bruce, I had occasion to work with him in both areas, but it is to the latter I will devote these brief reminiscences, as our collaboration in this fast expanding research field reached from its very dawn till relatively recently. 2006, the year of Bruce’s passing, marked the silver jubilee of antimicrobial peptide research, officially initiated with the publication of the seminal paper on the cecropins by Boman (see Figure 1) and coworkers. 1 Hans had befriended Bruce during his postdoc (1958–60) in Fritz Lipmann’s group at Rockefeller, and his logical enthusiasm over the finding of a family of eukaryotic, geneencoded peptides with remarkably potent antimicrobial activities must have been contagious for Bruce, who started to collaborate with Hans on the cecropins in late 1981. On joining Bruce’s lab in January 1982, the very first project given to me was to synthesize the putative 37-residue sequence of cecropin A, to confirm some structural assignations tentatively proposed for the C-terminal region. A previous synthetic attempt 2 had turned out an active compound, albeit nonidentical with the natural peptide. Building on that result and benefiting from several improvements emanating at the time from Bruce and Jimmy Tam’s joint research—not least the very useful high-low HF cleavage method 3 —I completed my assignment in two-and-a-half months, which at the time was regarded a reasonable time for a relative novice charged with the fully manual synthesis of a 37-residue, tritiumlabeled peptide. Our synthetic product was completely identical with the native peptide by microbiological as well as biochemical (enzyme digest + HPLC) criteria, and we were able to confirm the hitherto uncertain structure of the C-terminal end by means of plasma desorption MS, a forerunner of modern MALDI-TOF MS. In addition, our report 4 discussed the relevance of the Trp-2 residue for antimicrobial activity and thus set the basis for further analogue work. 5 In retrospect, that initial 2-year stint in the cecropin project appears as a decisive period, where Bruce’s gracious support and encouragement became the beacon blazing away the often usual angst of a nascent scientific career. A thorough and constructive draft reviewer if ever I saw one, Bruce returned each one of my versions generously endowed with pencil scribbles which, readily deciphered, brought gradual improvement to my struggling manuscripts. To Bruce I owe a great deal of any abilities I may have achieved as a (non-native) writer of English scientific texts. Those early 1980s cecropin manuscripts, first examples of the substantial contri