Quest for the chemical synthesis of proteins.

The chemical synthesis of proteins has been the wish of chemists since the early 19th century. There were decisive methodological steps necessary to accomplish this aim. Cornerstones were the introduction of the Z-protecting group of Bergmann and Zervas, the development of Solid-phase Peptide Synthesis of Merrifield, and the establishment of Native Chemical Ligation by Kent. Chemical synthesis of proteins has now become generally applicable technique for the synthesis of proteins with tailor made properties which can be applied not only in vitro but also in vivo .Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

From defining antigens to new therapies in multiple sclerosis: honoring the contributions of Ruth Arnon and Michael Sela.

Ruth Arnon and Michael Sela profoundly influenced the development of a model system to test new therapies in multiple sclerosis (MS). Their application of the animal model, known as experimental autoimmune encephalomyelitis (EAE), for the discovery of Copaxone, opened a new path for testing of drug candidates in MS. By measuring clinical, pathologic, and immunologic outcomes, the biological implications of new drugs could be elucidated. Using EAE they established the efficacy of Copaxone as a therapy for preventing and reducing paralysis and inflammation in the central nervous system without massive immune suppression. This had a huge impact on the field of drug discovery for MS. Much like the use of parabiosis to discover soluble factors associated with obesity, or the replica plating system to probe antibiotic resistance in bacteria, the pioneering research on Copaxone using the EAE model, paved the way for the discovery of other therapeutics in MS, including Natalizumab and Fingolimod. Future applications of this approach may well elucidate novel therapies for the neurodegenerative phase of multiple sclerosis associated with disease progression.

Proteolysis of the class II-associated invariant chain generates a peptide binding site in intracellular HLA-DR molecules. Proc. Natl. Acad. Sci. USA. 1991. 88: 3150-3154.

HLA-DR molecules are heterodimeric transmembrane glycoproteins that associate intracellularly with a polypeptide known as the invariant (I) chain. Shortly before expression of the HLA-DR αß dimer on the cell surface, however the I chain is removed from the intracellular αßI complex by a mechanism thought to involve proteolysis . In this report, we show that treatment of purified αßI with the cysteine proteinase cathepsin B results in the specific proteolysis of the HLA-DR-associated I chain in vitro. As a consequence of this, the I chain is removed and free αß dimers are released from αßI. Although αßI fails to bind an immunogenic peptide, the released αß dimers acquire the ability to bind the peptide after proteolysis of the I chain. These results suggest that the I chain inhibits immunogenic peptide binding to αßI early during intracellular transport and demonstrate that proteolysis is likely to be the in vivo mechanism of I chain removal.

Fifty years later: the disk goes to the prom.

Although age-related macular degeneration is the most prevalent macular disease in the world, numerous discoveries regarding the molecular bases of vision have been made through genetic association studies of rare inherited maculopathies. In this issue of the JCI, Yang et al. present a functional genetics study that identifies a role for prominin 1 (PROM1), best known as a stem cell and/or progenitor cell marker, in the biogenesis of retinal photoreceptor disk arrays (see the related article beginning on page 2908). This study supports an established model in which disk morphogenesis occurs through membrane evagination and extends other recent studies assigning PROM1 important functions outside of the stem cell niche.

Glatiramer acetate: evidence for a dual mechanism of action.

Glatiramer acetate is a disease-modifying drug approved for the treatment of relapsing-remitting multiple sclerosis. Since its discovery almost four decades ago, and in particular since the observation of its beneficial clinical effects in the late 1980s and early 1990s, numerous data have been generated and contribute pieces of a puzzle to help explain the mechanism of action of glatiramer acetate. Two major themes have emerged, namely (i) the induction of glatiramer acetate-reactive TH2 immunoregulatory cells, and (ii) the stimulation of neurotrophin secretion in the central nervous system that may promote neuronal repair.

Venom-derived peptides inhibiting Kir channels: Past, present, and future.

Inwardly rectifying K+ (Kir) channels play a significant role in vertebrate and invertebrate biology by regulating the movement of K+ ions involved in membrane transport and excitability. Yet unlike other ion channels including their ancestral K+-selective homologs, there are very few venom toxins known to target and inhibit Kir channels with the potency and selectivity found for the Ca2+-activated and voltage-gated K+ channel families. It is unclear whether this is simply due to a lack of discovery, or instead a consequence of the evolutionary processes that drive the development of venom components towards their targets based on a collective efficacy to 1) elicit pain for defensive purposes, 2) promote paralysis for prey capture, or 3) facilitate delivery of venom components into the circulation. The past two decades of venom screening has yielded three venom peptides with inhibitory activity towards mammalian Kir channels, including the discovery of tertiapin, a high-affinity pore blocker from the venom of the European honey bee Apis mellifera. Venomics and structure-based computational approaches represent exciting new frontiers for venom peptide development, where re-engineering peptide 'scaffolds' such as tertiapin may aid in the quest to expand the palette of potent and selective Kir channel blockers for future research and potentially new therapeutics. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'

The [pre-] history of the incretin concept.

The discoverers of secretin already thought of the existence of a chemical excitant for the internal secretion of the pancreas. Numerous experiments have been performed and published between 1906 and 1935 testing the effect of injected or ingested duodenal ("secretin") extracts on fasting or elevated blood glucose levels of normal or diabetic animals and humans with contradictory results. In 1940, after a series of negative dog experiments performed by an opinion leader, the existence of an incretin was considered questionable and further research stopped for more than 20 years. However, after the development of the radio-immunoassay, the incretin-concept has been revived in 1964, showing that significantly more insulin was released after ingestion of glucose than after intravenous injection. The possibility that nerves or one of the known gut hormones were responsible for the incretin effect could be ruled out. In 1970, glucose dependent insulinotropic polypeptide (GIP), and finally, in 1985 glucagon-like peptide 1 (GLP-1) and its truncated form GLP-1(7-36) were recognized as true incretins. Thereafter, multiple antidiabetic qualities and the therapeutic perspectives of GLP-1(7-36) and its analogues and mimetics have been demonstratred.

Peptides at the blood brain barrier: Knowing me knowing you.

When the Davis Lab was first asked to contribute to this special edition of Peptides to celebrate the career and influence of Abba Kastin on peptide research, it felt like a daunting task. It is difficult to really understand and appreciate the influence that Abba has had, not only on a generation of peptide researchers, but also on the field of blood brain barrier (BBB) research, unless you lived it as we did. When we look back at our careers and those of our former students, one can truly see that several of Abba's papers played an influential role in the development of our personal research programs.

Insights into bombesin receptors and ligands: Highlighting recent advances.

This following article is written for Prof. Abba Kastin's Festschrift, to add to the tribute to his important role in the advancement of the role of peptides in physiological, as well as pathophysiological processes. There have been many advances during the 35 years of his prominent role in the Peptide field, not only as editor of the journal Peptides, but also as a scientific investigator and editor of two volumes of the Handbook of Biological Active Peptides [146,147]. Similar to the advances with many different peptides, during this 35 year period, there have been much progress made in the understanding of the pharmacology, cell biology and the role of (bombesin) Bn receptors and their ligands in various disease states, since the original isolation of bombesin from skin of the European frog Bombina bombina in 1970 [76]. This paper will briefly review some of these advances over the time period of Prof. Kastin 35 years in the peptide field concentrating on the advances since 2007 when many of the results from earlier studies were summarized [128,129]. It is appropriate to do this because there have been 280 articles published in Peptides during this time on bombesin-related peptides and it accounts for almost 5% of all publications. Furthermore, 22 Bn publications we have been involved in have been published in either Peptides [14,39,55,58,81,92,93,119,152,216,225,226,231,280,302,309,355,361,362] or in Prof. Kastin's Handbook of Biological Active Peptides [137,138,331].

Four decades of structure determination by mass spectrometry: from alkaloids to heparin.

The early (1950's and 1960's) use of mass spectrometry in natural products chemistry and its evolution to the present significance in biochemistry is recounted. This methodology allowed the facile and speedy determination of the structure of a number of indole alkaloids, such as sarpagine, quebrachamine, and two groups isolated from the roots of Aspidosperma quebracho blanco. At the same time, the first strategy for the sequencing of small peptides by mass spectrometry was demonstrated. It slowly advanced, over a period of two decades, to an important alternative of the ubiquitous automated Edman degradation. Further advances in methodology and instrumentation established mass spectrometry as today's indispensable tool for the characterization of proteins in biochemistry and biology. A new concept of the ionization of highly acidic compounds as the protonated complexes with basic peptides, which allows the accurate determination of the molecular weights of the former, a highly sensitive method for the sequencing of heparin fragments and related sulfated glycosaminoglycans was developed more recently.

Antineoplastons: history of the research (I).

Antineoplastons are naturally-occurring peptides and amino acid derivatives which control neoplastic growth. The theory of antineoplastons was conceived through the application of the cybernetic theory of autonomous systems to studies of peptides in human blood. The original research began in 1967, when it was noticed that there were significant differences in the peptide content in the serum of cancer patients as compared with the control group. Since similar peptide fractions were isolated from urine, a research programme was established for the identification of antineoplastic peptides from urine. Medicinal use of urine and urine extracts has been known for centuries in ancient Egypt, Greece, Rome, India and North and Central America. In modern times, the first study of growth-inhibiting substances in urine was conducted in 1937. The research on urinary peptides has a long history and was initiated by a Polish researcher, S. Bondzynski, in 1897. Antineoplastons were found to be completely different from peptides and amino acid derivatives isolated from urine by other authors. Research on antineoplastons led to the isolation of different peptide fractions from urine, named Antineoplaston A1, A2, A3, A4 and A5, which possessed high anticancer activity and low toxicity. The first active component was identified as 3-phenylacetylamino-2,6-piperidinedione and was named Antineoplaston A10. Two synthetic derivatives of Antineoplaston A10 were named Antineoplaston AS2-1 and AS2-5. All antineoplaston formulations were submitted for Phase I clinical studies in advanced cancer patients. The treatment was free from significant side-effects and resulted in objective response in a number of advanced cancer cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Ghrelin: much more than a natural growth hormone secretagogue.

Ghrelin, a 28 amino acid acylated peptide predominantly produced by the stomach, displays strong growth hormone-releasing activity mediated by the hypothalamus-pituitary GH secretagogue receptors that were found to be specific for a family of synthetic, orally active GH secretagogues. The discovery of ghrelin brings us to a new understanding of the regulation of GH secretion. However, ghrelin is much more than simply a natural GH secretagogue. It also acts on other central and peripheral receptors and exhibits other actions, including stimulation of lactotroph and corticotroph secretion, orexigenic, influences gastroenteropancreatic functions, and has metabolic, cardiovascular and antiproliferative effects. Knowledge of the whole spectrum of biologic activities of this new hormone will provide new understanding of some critical aspects of neuroscience, metabolism and internal medicine. In fact, GHS were born more than 20 years ago as synthetic molecules, eliciting the hope that orally active GHS could be used to treat GH deficiency as an alternative to recombinant human GH. However, the dream did not become reality and the usefulness of GHS as an anabolic anti-aging intervention restoring the GH/IGF-I axis in somatopause is still unclear. Instead, we now face the theoretic possibility that GHS analogues acting as agonists or antagonists could become candidate drugs for the treatment of pathophysiologic conditions in internal medicine totally unrelated to disorders of GH secretion.