A novel view on the mechanisms of action of insulin and other insulin superfamily peptides: involvement of adenylyl cyclase signaling system

A new signaling mechanism common to mammalian insulin, insulin-like growth factor I, relaxin and mollusc insulin-like peptide, and involving receptor-tyrosine kinase==>G(i) protein (betagamma)==>phosphatidylinositol-3-kinase==>protein kinase Czeta==>adenylyl cyclase==>protein kinase A was discovered in the muscles and some other tissues of vertebrates and invertebrates. The authors' data were used to reconsider the problem of participation of the adenylyl cyclase-cAMP system in the regulatory effects of insulin superfamily peptides. A hypothesis has been put forward according to which the adenylyl cyclase signaling mechanism producing cAMP has a triple co-ordinating role in the regulatory action of insulin superfamily peptides on the main cell processes, inducing the mitogenic and antiapoptotic effects and inhibitory influence on some metabolic effects of the peptides. It is suggested that cAMP is a key regulator responsible for choosing the transduction pathway by concerted launching of one (proliferative) program and switching off (suppression) of two others, which lead to cell death and to the predomination of anabolic processes in a cell. The original data obtained give grounds to conclude that the adenylyl cyclase signaling system is a mechanism of signal transduction not only of hormones with serpentine receptors, but also of those with receptors of the tyrosine kinase type (insulin superfamily peptides and some growth factors).     

Serpentine type receptors and heterotrimeric G-proteins in yeasts: Structural-functional organization and molecular mechanisms of action

The signal systems of the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, coupled to heterotrimeric G-proteins and sensitive to pheromones and alimentary molecules, are prototypes of hormonal signal systems of the higher vertebrate animals and are widely used in studies on molecular mechanisms of their functioning. This review summarizes and analyzes data on structural-functional organization of the first two components of these systems—receptors of the serpentine type and heterotrimeric G-proteins; mechanisms of functional coupling of receptors and G-proteins both between each other and to other signal proteins are discussed. It has been shown that at the early stages of evolution of signaling systems, at the yeast level, various models of transduction of signals into the cell were tested; many of them differ essentially from the classic model of the three-component, G-protein-coupled signal system of the higher vertebrates.     

Receptors of the serpentine type and heterotrimeric G-proteins of the yeasts: structural-functional organization and molecular action mechanisms

The signal systems of the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, coupled to heterotrimeric G-proteins and sensitive to pheromones and alimentary molecules, are prototypes of hormonal signal systems of the higher vertebrate animals and are widely used in studies on molecular mechanisms of their functioning. This review summarizes and analyzes data on structural-functional organization of the first two components of these systems - receptors of the serpentine type and heterotrimeric G-proteins; mechanisms of functional coupling of receptors and G-proteins both between each other and to other signal proteins are discussed. It has been shown that at the early stages of evolution of signal systems, at the yeast level, various models of transduction of signals into the cell were tested; many of them differ essentially from the classic model of the three-component, G-protein-coupled signal system of the higher vertebrates.     

Study of structural-functional arrangement of the adenylyl cyclase signaling mechanism of action of insulin-like growth factor 1 revealed in muscle tissue of representatives of vertebrates and invertebrates

Based on the earlier discovered by the authors adenylyl cyclase signaling mechanisms (ACSM) of action of insulin and relaxin, a study was performed of the existence of a similar action mechanism of another representative of the insulin superfamily-the insulin—like growth factor 1 (IGF-1) in the muscle tissue of vertebrates (rat) and invertebrates (mollusc). For the first time there was detected participation of ACSM in the IGF-1 action, including the six-component signaling cascade: receptor tyrosine kinase → Gi-protein (βγ-dimer) → phosphatidylinositol-3-kinase (PI-3K) → protein kinase Cζ (PKCζ) → Gs-protein → adenylyl cyclase. By structural-functional organization at postreceptor stages, it coincides completely with that of insulin and relaxin, which we revealed in rat skeletal muscle. In smooth muscle of the mollusc Anodonta cygnea this ACSM of action of IGF-1 has only one difference-the protein kinase C included in this mechanism is represented not by the PKCζ isoform, but by another isoform close to PKCε of the vertebrate brain. Earlier we revealed the same differences in muscles of this mollusc in the ACSM of action of insulin and relaxin.     

Structural and functional organization of the adenylyl cyclase signaling mechanism of insulin-like growth factor 1 revealed in the muscle tissue in vertabrates and invertebrates

Based on the earlier discovered by the authors adenylyl cyclase signaling mechanisms (ACSM) of action of insulin and relaxin, the study was performed of the presence a similar action mechanism of another representative of the insulin superfamily--the insulin-like growth factor 1 (IGF-1) in the muscle tissues of vertebrates (rat) and invertebrates (mollusc). For the first time there was detected participation of ACSM in the IGF-1 action, including the six component signaling cascade: receptor tyrosine kinase --> G(i)-protein (betagamma-dimer) --> phosphatidylinositol-3-kinase (PI-3-K) --> protein kinase Czeta (PKCzeta) --> G(-)protein --> adenylyl cyclase. By this mechanism structural-functional organization at postreceptor stages, in coincides completely with the mechanism of insulin and relaxin, which we revealed in rat skeletal muscle. In smooth muscle of the mollusc Anodonta cygnea this ACSM of action of IGF-1 has only one difference--the protein kinase C included in this mechanism is represented not by PKCzeta isoform, but by another isoform close to PKCepsilon of the vertabrate brain. Earlier we revealed the same differences in muscle of this mollusc in the ACSM of action of insulin and relaxin.     

Using paleogenomics to study the evolution of gene families: origin and duplication history of the relaxin family hormones and their receptors

Recent progress in the analysis of whole genome sequencing data has resulted in the emergence of paleogenomics, a field devoted to the reconstruction of ancestral genomes. Ancestral karyotype reconstructions have been used primarily to illustrate the dynamic nature of genome evolution. In this paper, we demonstrate how they can also be used to study individual gene families by examining the evolutionary history of relaxin hormones (RLN/INSL) and relaxin family peptide receptors (RXFP). Relaxin family hormones are members of the insulin superfamily, and are implicated in the regulation of a variety of primarily reproductive and neuroendocrine processes. Their receptors are G-protein coupled receptors (GPCR's) and include members of two distinct evolutionary groups, an unusual characteristic. Although several studies have tried to elucidate the origins of the relaxin peptide family, the evolutionary origin of their receptors and the mechanisms driving the diversification of the RLN/INSL-RXFP signaling systems in non-placental vertebrates has remained elusive. Here we show that the numerous vertebrate RLN/INSL and RXFP genes are products of an ancestral receptor-ligand system that originally consisted of three genes, two of which apparently trace their origins to invertebrates. Subsequently, diversification of the system was driven primarily by whole genome duplications (WGD, 2R and 3R) followed by almost complete retention of the ligand duplicates in most vertebrates but massive loss of receptor genes in tetrapods. Interestingly, the majority of 3R duplicates retained in teleosts are potentially involved in neuroendocrine regulation. Furthermore, we infer that the ancestral AncRxfp3/4 receptor may have been syntenically linked to the AncRln-like ligand in the pre-2R genome, and show that syntenic linkages among ligands and receptors have changed dynamically in different lineages. This study ultimately shows the broad utility, with some caveats, of incorporating paleogenomics data into understanding the evolution of gene families.     

Molecular evolution of the NF-κB signaling system

The mechanisms of innate immunity in vertebrates show certain overall resemblances to immune mechanisms of insects. Two hypotheses have been proposed to explain these resemblances. (1) According to the evolutionary continuity hypothesis, innate immune mechanisms evolved in the common ancestor of vertebrates and insects and have been conserved since that time. (2) In the independent-evolution hypothesis, the mechanisms of innate immunity in vertebrates evolved independently from invertebrate immune mechanisms. Phylogenetic analysis of five gene families (Pelle, Rel, IkappaB, Toll, and TRAF) whose members are involved in NF-kappaB signaling in vertebrates and insects were used to decide between these hypotheses. The phylogenies of the Rel and TRAF families strongly supported independent evolution of immune functions in vertebrates and invertebrates, and, except for a possible case in the Pelle family, orthologous molecules having immune functions in both vertebrates and invertebrates were not found. The results suggest that NF-kappaB represents an ancient, generalized signaling system that has been co-opted for immune system roles independently in vertebrate and insect lineages.     

The ubiquity of the insulin superfamily across the eukaryotes detected using a bioinformatics approach

The insulin superfamily is composed of a diverse group of proteins that share a common structural design whose most notable feature is a set of disulfide bonds. There is now sufficient experimental and bioinformatics evidence that it is represented in at least a number of well-investigated invertebrates, where they have been found to intervene mainly in complex processes such as mitosis, cell growth, castes differentiation, and fertility. In this article we automated a methodology first proposed elsewhere-that combines sequence similarity with assessing membership to the superfamily by conservation of structuraly key residues-to identify putative insulin-like peptides (ILPs) in completely sequenced genomes, and applied it as a pipeline to a group of 46 organisms both vertebrates and invertebrates. As a result, we were able to identify 1,653 putative members of the insulin superfamily, from 17 putative members in C. savigny to 58 in X. tropicalis. Moreover, we found that structural distinctions-such as peptides length-between functionally diverse members of the superfamily found in vertebrates, that is, insulins, IGFs, and relaxins, are not equally represented in invertebrates genomes, suggesting that such divergence has occurred only recently in the evolutionary history of vertebrates.     

Perspective: Research Activity of Enteropancreatic and Brain/Central Nervous System Hormones Across Invertebrates and Vertebrates

During the past two decades there have been rapid advances inour knowledge of the structure and function of the protein hormonesin the brain and gastroenteropancreatic system (GEP). Many publishedarticles have highlighted the superfamily of hormonal peptides,specifically, the mechanisms and control of peptide synthesisin neural and non-neural tissues, and gene structure. Here wepresent an analysis of the annual trends, between 1980 and 1997,of research emphasis on six protein/peptide hormones, as reflectedby their individual frequency of publication per year. Althoughthis symposium is focused on the GEP hormones, we provide hereina perspective on the level of research activity of the hormonesinsulin, glucagon, cholecystokinin, insulin-like growth factor-Iand -II, neuropeptide Y and somatostatin in the brain/gut systemsthroughout the vertebrates and invertebrates. Many publicationsdeal with the evolution of these peptides and their superfamilies,yet as noted in this review, there are relatively few referencesto these peptides in invertebrates and non-mammalian species.Typically in invertebrates, the number of citations is low andmostly focused on three phyla, the arthropods, mollusks andhelminths. Generally, in the vertebrates the smallest numberof citations is in the cyclostomes and elasmobranchs. Becausemost groups of invertebrates and vertebrates have received scantattention, phylogenetic comparisons are limited. Evolutionaryinformation concerning important groups of animals, such ashelminths, mollusks, protochordates and cyclostomes, is essentialto establish the phylogenetic histories of the hormonal peptides.The challenge to comparative endocrinologists is to examinespecies in key evolutionary positions in order to gain an understandingof the diversity and function of the hormones and to determinethe molecular features that form clues to their phyletic interrelationshipsand progression.     

The binding ability of insulin-related peptides as the clue to the search for their functional role in phylogenesis. Introduction to the problem

The common plan of structure of the main peptides of the vertebrate insulin family—insulin itself, IGF-I, IGF-II, and relaxin—has distinct structural formations. Each of the peptides performs its characteristic function. However, overlapping of insulin and IGF-I actions and its stability in the vertebrate phylogenesis have formed the concept of their regulation of growth and metabolism as a function fixed in phylogenesis for a certain type of structures. At the same time, study of insulin-related peptides in invertebrates has revealed the wider spectrum, than in vertebrates, of biological effects; this indicated that the similarity of the total structure design is not sufficient for judging about their functional role. Functional possibilities of a regulatory peptide depend fundamentally on its capability for binding to the receptor realizing its biological action. However, the binding ability has a wider significance than merely transmission of biological signals. Thus, IGF-II when interacting with receptors realizing its biological effects also binds to the IGF-2 receptor limiting its action and, besides, to the binding proteins (BP) modulating its action. The entire cycle of interactions occurs in the body at different affinity levels. Meanwhile, insulin interacts neither with IGF-2 receptor nor with BP. In this case, specificity and sequence of interaction with each of receptors or with protein are due not to the general design of the peptide structure, but rather to structure of individual submolecular determinants—binding domains. The leading role in disclosure of composition and structure of these domains is played by the “mutant-ligand” approach evaluating affinity of modified analogs. To analyze role of structural elements of the binding domains, the author proposes the system of estimation of affinity of the studied analogs. The present work, alongside with consideration of methodical aspects of the forthcoming analysis, is an introduction to the problem of organization of the binding domains connected directly with functional role of peptides of the insulin type. The proposed analysis is due to necessity of specification of this organization both in one molecule and in different molecules with a similar plan of structure on the basis of not always unanimous literature data and of clarification of principles of structure of these domains.     

Conservation of neurogenic genes and mechanisms.

Reports from the past year have demonstrated that neural basic helix-loop-helix genes and LIM homeobox genes contribute to neuronal subtype specification in vertebrates and invertebrates, that Notch signaling specifies cell fates in the developing vertebrate inner ear, and that the organization of the central nervous system into three columns is shared by vertebrates and invertebrates. These findings pave the way for future work that will help to establish the extent to which these similarities represent evolutionary conservation.     

Conserved insulin signaling in the regulation of oocyte growth,development, and maturation

Insulin signaling regulates various aspects of physiology, such as glucose homeostasis and aging, and is a key determinant of female reproduction in metazoans. That insulin signaling is crucial for female reproductive health is clear from clinical data linking hyperinsulinemic and hypoinsulinemic condition with certain types of ovarian dysfunction, such as altered steroidogenesis, polycystic ovary syndrome, and infertility. Thus, understanding the signaling mechanisms that underlie the control of insulin‐mediated ovarian development is important for the accurate diagnosis of and intervention for female infertility. Studies of invertebrate and vertebrate model systems have revealed the molecular determinants that transduce insulin signaling as well as which biological processes are regulated by the insulin‐signaling pathway. The molecular determinants of the insulin‐signaling pathway, from the insulin receptor to its downstream signaling components, are structurally and functionally conserved across evolution, from worms to mammals—yet, physiological differences in signaling still exist. Insulin signaling acts cooperatively with gonadotropins in mammals and lower vertebrates to mediate various aspects of ovarian development, mainly owing to evolution of the endocrine system in vertebrates. In contrast, insulin signaling in Drosophila and Caenorhabditis elegans directly regulates oocyte growth and maturation. In this review, we compare and contrast insulin‐mediated regulation of ovarian functions in mammals, lower vertebrates, C. elegans, and Drosophila, and highlight conserved signaling pathways and regulatory mechanisms in general while illustrating insulin's unique role in specific reproductive processes.     

Glucagon-like and insulin-like hormones of the insect neurosecretory system.

Aqueous extracts of corpus cardiacum-corpus allatum complexes of the adult tobacco hornworm Manduca sexta produced both glycogenolysis and hypoglycaemia when injected into the larval form of the same species. Application of specific radioimmuno assays to similar extracts showed also that these gland complexes contain both glucagon-like and insulin-like peptides. Further, the partially purified immunoreactive peptides had the expected biological activities. The former decreased the glycogen content of the fatbody and the latter the circulating trehalose levels in recipient animals. These results suggest the existence of hormones in these invertebrates having both biological and structural similarities to vertebrate insulin and glucagon.     

Adenylyl cyclase signaling mechanisms of relaxin and insulin action: similarities and differences

The adenylyl cyclase signaling mechanism (ACSM) of relaxin H2 action was discovered and deciphered in mammalian muscles. A study of signaling blocks involved in ACSM of relaxin in comparison with that of insulin previously detected showed a close similarity throughout the post-receptor signaling chain of both hormones. The inhibitory action of tyrosine kinase blockers on the hormone AC activating effect indicates that the relaxin receptor involved in ACSM is likely to be of the tyrosine kinase type. However, a recent discovery of a relaxin receptor with serpentine architecture leaves open the question concerning the existence of receptor of the tyrosine kinase type. The structural-functional organization of the ACSM due to the action of relaxin-shown here for the first time-can be presented as the following signaling sequence: relaxin receptor ==>G(i) protein (betagamma-dimer) ==>phosphatidylinositol 3-kinase ==>protein kinase Czeta ==>G(s) protein ==>adenylyl cyclase. According to our hypothesis, the regulatory action of the insulin superfamily peptides on cell processes (proliferation, apoptosis, and metabolism) is mediated via ACSM.     

Immune Related Genes Underpin the Evolution of Adaptive Immunity in Jawless Vertebrates

The study of immune related genes in lampreys and hagfish provides a unique perspective on the evolutionary genetic underpinnings of adaptive immunity and the evolution of vertebrate genomes. Separated from their jawed cousins at the stem of the vertebrate lineage, these jawless vertebrates have many of the gene families and gene regulatory networks associated with the defining morphological and physiological features of vertebrates. These include genes vital for innate immunity, inflammation, wound healing, protein degradation, and the development, signaling and trafficking of lymphocytes. Jawless vertebrates recognize antigen by using leucine-rich repeat (LRR) based variable lymphocyte receptors (VLRs), which are very different from the immunoglobulin (Ig) based T cell receptor (TCR) and B cell receptor (BCR) used for antigen recognition by jawed vertebrates. The somatically constructed VLR genes are expressed in monoallelic fashion by T-like and B-like lymphocytes. Jawless and jawed vertebrates thus share many of the genes that provide the molecular infrastructure and physiological context for adaptive immune responses, yet use entirely different genes and mechanisms of combinatorial assembly to generate diverse repertoires of antigen recognition receptors.     

Using peptide strategy for study functions and structure of signal proteins with enzymatic activity

The peptide strategy, a new direction of molecular endocrinology, includes the synthesis of peptides corresponding to functional regions of signal proteins, the use of the peptides for study of the molecular mechanisms of transduction of hormonal signal into cell ant the development of selective regulators of hormonal signaling systems on the basis of these peptides. The peptide strategy is used for study a wide spectrum of the proteins, components of signal systems, the proteins possessing the catalytic activity in particular, such as tyrosine kinases receptors, the enzymes generating the second messengers, serine/threonine protein kinase, phosphatases. In the first time in the review the data concerning the synthetic peptides, derivatives of the primary structure of proteins with the enzymatic activity, their application for study of the structural-functional organization and the molecular mechanisms of action of signal proteins, and the construction of regulators of fundamental cell processes on the basis of these peptides are analyzed and summarized.     

Developmental genetic evidence for a monophyletic origin of the bilaterian brain

The widely held notion of an independent evolutionary origin of invertebrate and vertebrate brains is based on classical phylogenetic, neuroanatomical and embryological data. The interpretation of these data in favour of a polyphyletic origin of animals brains is currently being challenged by three fundamental findings that derive from comparative molecular, genetic and developmental analyses. First, modern molecular systematics indicates that none of the extant animals correspond to evolutionary intermediates between the protostomes and the deuterostomes, thus making it impossible to deduce the morphological organization of the ancestral bilaterian or its brain from living species. Second, recent molecular genetic evidence for the body axis inversion hypothesis now supports the idea that the basic body plan of vertebrates and invertebrates is similar but inverted, suggesting that the ventral nerve chord of protostome invertebrates is homologous to the dorsal nerve cord of deuterostome chordates. Third, a developmental genetic analysis of the molecular control elements involved in early embryonic brain patterning is uncovering the existence of structurally and functionally homologous genes that have comparable and interchangeable functions in key aspects of brain development in invertebrate and vertebrate model systems. All three of these findings are compatible with the hypothesis of a monophyletic origin of the bilaterian brain. Here we review these findings and consider their significance and implications for current thinking on the evolutionary origin of bilaterian brains. We also preview the impact of comparative functional genomic analyses on our understanding of brain evolution.     

Negative regulation of TGF-β signaling in development

The TGF-β superfamily members have important roles in controlling patterning and tissue formation in both invertebrates and vertebrates. Two types of signal transducers, receptors and Smads, mediate the signaling to regulate expression of their target genes. Despite of the relatively simple signal transduction pathway, many modulators have been found to contribute to a tight regulation of this pathway in a variety of mechanisms. This article reviews the negative regulation of TGF-β signaling with focus on its roles in vertebrate development.     

棘皮动物免疫学研究进展

棘皮动物属原始后口动物、无脊椎动物的最高等类群,它处于由无脊椎动物向脊椎动物开始分支进化的阶段．研究棘皮动物的免疫功能和作用机理,对从比较免疫学角度探讨动物免疫系统进化过程有承前启后的重要意义．因此,有必要对棘皮动物的免疫学研究进展作一个较全面的综述,并理清未来的研究热点和方向．棘皮动物与其他无脊椎动物一样具有先天性免疫系统,但未发现脊椎动物所具有的获得性免疫．其免疫应答是由参与免疫反应的效应细胞——体腔细胞和多种体液免疫因子共同介导的．比较免疫学分析表明,棘皮动物存在脊椎动物补体系统的替代途径和凝集素途径,但未发现经典途径和明确的终端途径．棘皮动物先天性免疫系统存在数量庞大的基因家族．今后应加强对未知免疫相关基因、蛋白质、信号传导途径及效应分子的研究,回答免疫系统的起源、功能和进化等问题．