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Insulin-Related Peptides in Insects and Other Arthropods HPFP: Recent Advances in Insects and Other Arthropods Vol. 1 163 [19]. Although bombyxin genes are expressed mainly in the brain, they are also expressed at minute levels in other tissues, such as the silk gland, gonads, and gut [34]. In D. melanogaster, 7 insulin-like peptide (DILP) genes, dilp1 - dilp7, were found in the genome. The dilp1, dilp2, dilp3, and dilp5 transcripts of these genes were detected in the median neurosecretory cells [5, 35] and dilp4 and dilp6 transcripts were detected in the larval gut and dilp7 transcript was done in the nerve cord [5, 36]. These expressions indicate that DILPs are produced in a tissue- and stage-specific manner. The expression level of bombyxin and other insulin-like peptide genes also changes temporally during development [34, 36] and is influenced by nutrient conditions. For example, when the larvae of D. melanogaster were subjected to starvation, dilp3 and dilp5 expression levels were reduced but dilp2 expression levels remained unchanged [35]. Table 1: Tissue distribution and detection methods of insulin-like peptides Lepidoptera Diptera Other orders Species Distribution Method Manduca sexta Brain median neurosecretory cells, Frontal ganglion Anti-bovine insulin immunostaining [12, 13] Bombyx mori Brain median neurosecretory cells Purification as Samia-PTTH [3] Anti-bombyxin immunostaining [14] in situ hybridization [15] Galleria mellonella Brain median and lateral neurosecretory cells Samia cynthia ricini Brain median and lateral neurosecretory cells Anti-bombyxin immunostaining [16] Gene identification [17] Anti-Samia bombyxin immunostaining [18] Agrius convolvuli Brain median neurosecretory cells cDNA cloning, in situ hybridization [19] Spodoptera littoralis Brain median neurosecretory cells PCR-based cloning, anti-bombyxin immunostaining [20] Calliphora vomitoria Brain median neurosecretory cells Anti-bovine insulin immunostaining [21] Eristalis aeneus Brain median neurosecretory cells Anti-bovine insulin immunostaining [22] Drosophila melanogaster Brain median neurosecretory cells* Anti-bovine insulin immunostaining [23] Genome information [5] Anti-DILP immunostaining [24] Aedes aegypti Brain lateral neurosecretory cells Anti-DILP immunostaining [24] Locusta migratoria Brain median neurosecretory cells Isolation from a cDNA library of brain median neurosecretory cells [4] Purification [25] Schistocerca gregaria Brain median neurosecretory cells Purification, anti-Locusta insulin immunostaining [26] Leucophaea maderae Brain median neurosecretory cells* Anti-bovine insulin immunostaining [27] *Brain median neurosecretory cells: in addition to the median neurosecretory cells, the genes encoding DILPs are expressed in various tissue cells including neurons, gut cells, fat body cells, and ovarian cells. 3. SUGAR METABOLISM In mammals, insulin is widely accepted as a hypoglycemic hormone. The hypoglycemic effect was demonstrated when an extract from D. melanogaster was injected into mice [29], suggesting that insulinlike hormones are present in both insects and mammals. In insects, the major type of blood sugar is the non-reducing disaccharide trehalose, not glucose [37]. Normann [38] suggested that the hypertrehalosemia associated with decapitation of the blue blowfly, Calliphora erythrocephala, was due to the lack of a hypotrehalosemic hormone in the brain. In fact, when the median neurosecretory cells were ablated surgically from the brain of C. erythrocephala, the hemolymph trehalose and glucose levels were significantly elevated. After surgery, the elevated levels of both sugars were reduced by injection of the homogenate of the brain median neurosecretory cells [39]. In addition to the brain, hypotrehalosemic activity was found in the extract of the corpora allata and corpora cardiaca of M. sexta and in the fraction
172 Hemolymph Proteins and Functional Peptides: Recent Advances in Insects and Other Arthropods Vol. 1, 2012, 172-182 ENF Peptides Manabu Kamimura * National Institute of Agrobiological Sciences, 1-2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan Muhammad Tufail and Makio Takeda (Eds) All rights reserved-© 2012 Bentham Science Publishers CHAPTER 10 Abstract: ENF peptides are a family of insect specific multifunctional peptides consisting of 23-25 amino acids. They are involved in the regulation of many important biological processes, such as immunity, development, homeostasis, hibernation, and therefore regarded as a group of insect cytokines. In this chapter, I briefly review the structure biological functions, and modes of action of the ENF peptides. Keywords: ENF peptide, growth blocking peptide, paralytic peptide, plasmatocyte spreading peptide, cardioactive peptide, immunity, development, diapause, embryogenesis, Lepidoptera, hemocyte, epidermal growth factor. 1. INTRODUCTION-DISCOVERY AND NAMING OF ENF PEPTIDES In 1990, growth blocking peptide (GBP) that retards larval growth was identified from the larval hemolymph of the armyworm, Pseudaletia separata, that was parasitized with a parasitoid wasp Apantales kariyai [1, 2]. Shortly after that, several paralytic peptides (PP), which triggered rapid, rigid paralysis in injected insects, were isolated from the hemolymph of three moth larvae [3] - two of these peptides were from Manduca sexta, three were from Spodoptera exigua, and two were from Heliothis virescens. Several years later, the plasmatocyte spreading peptide (PSP) that stimulates spreading of plasmatocyte, a hemocyte subset especially involved in the encapsulation reaction, and the cardioactive peptide that increased heartbeats were isolated from the moths Pseudoplusia includens and Spodoptera eridania, respectively [4- 5]. Paralytic peptide was also isolated from three other moths, namely Trichoplusia ni [6], Antheraea yamamai [7], and Bombyx mori [8]. Because of the high similarities in their amino acid sequences (Fig. 1) and overlapping biological activities, Strand et al. [9] named these peptides as the “ENF peptide family” after their identical N-terminal sequence, Glu-Asn-Phe- (ENF-). The ENF peptides are involved in the regulation of many important biological processes, including immunity and development, and therefore regarded as a group of insect cytokines [10, 11]. The first reported nucleotide sequence of an ENF peptide-coding cDNA was that of the P. separata GBP [12]. Thereafter, cDNA or genomic ENF peptide-coding clones were isolated from P. separata [13], Mamestra brassicae [14, 15], Spodoptera litura [14], P. includens [16], M. sexta [17], B. mori [18], Samia cynthia pryeri [19], Theretra japonica [19], and Neogurelca himachala sangaica [19]. In addition, ENF peptide-coding cDNA clones were found in the EST databases of H. virescens, Spodoptera frugiperda, Antheraea assama, Samia cynthia ricini, and Choristoneura fumiferana (Fig. 1). Thus, the ENF peptides have been found so far only in moths belonging to the Noctuidae, Sphingidae, Saturniidae, Bombycidae, and Tortricidae families. Even though the DNA sequences of a massive number of EST clones are currently being analyzed in other lepidopteran families, such as in Yponomeutidae (Plutella xylostella [20]) Crambidae (Ostrinia nubilalis [21, 22]), and Nymphalidae (Heliconius erato and Heliconius melpomene [23, 24]), no ENF peptide encoding cDNA has yet been found among the sequenced clones, suggesting that the ENF peptide may exist only in the restricted families of Lepidoptera. *Address correspondence to Manabu Kamimura: National Institute of Agrobiological Sciences, 1-2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan; Phone: +81-298-38-6073; Fax: +81-298-38-6028; Email: kamimura@affrc.go.jp.
Page 2 and 3: Hemolymph Proteins and Functional P
Page 4 and 5: CONTENTS Foreword i Preface ii List
Page 6 and 7: ii PREFACE The aim of this eBook
Page 8 and 9: iv Giancarlo Lopez-Martinez Departm
Page 12 and 13: Hemolymph Lipoproteins: Role in Ins
Page 14 and 15: Adipokinetic Hormones and Their Rol
Page 16 and 17: 32 Hemolymph Proteins and Functiona
Page 18 and 19: 34 HPFP: Recent Advances in Insects
Page 20 and 21: Immune Response of Insects and Crus
Page 22 and 23: 78 Hemolymph Proteins and Functiona
Page 24 and 25: 80 HPFP: Recent Advances in Insects
Page 26 and 27: Structures and Functions of Insect
Page 30 and 31: Neurohormones and Second Messengers
Page 32 and 33: Role of Conventional and Unconventi
Page 38 and 39: ENF Peptides HPFP: Recent Advances

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