In Silico Analysis of Crustacean Hyperglycemic Hormone Family

Abstract

Through multiple sequence alignment and phylogenetic analysis, the subgrouping of the crustacean hyperglycemic hormone (CHH) family was updated using the most complete, nonredundant sequence data set. All sequences from insects were clustered into a distinct subbranch with characters closer to CHH subfamily I. Several sequences that are controversial in their nomenclature and classification are discussed. The motif configuration of CHHs differs from that of molt-inhibiting hormone or gonad-inhibiting hormone in both N and C termini. These two motifs approach each other in tertiary structure models, and the motif preference reveals the critical roles of these regions in functional specificity. Two types of exon organizations of the CHH family genes were observed. Four-exon Chh genes were found in a wide range of pan-crustacean (crustacean and hexapod) taxa, except for the penaeid species, from which the 3-exon Chh genes were reported. Meanwhile, the 3-exon structure was found in the Mih gene and Moih genes from one brachyuran species. Combining gene scan skill and exon splicing rules found in this study, we define three more novel sequences from two insect genomes. The pattern of the exon-exon junction within the mature peptide segment is preserved in all CHH family members.

Circadian clocks in crustaceans: identified neuronal and cellular systems

“…However, CHHs are distinguished when looking at the simpler gene and precursor structures of the latter subfamily peptides, which e.g. lack so-called precursor-related peptides (131,158,159). CHH subfamily peptides usually consist of 72-73 amino acids (aa), show a sequence similarity exceeding 55% between species, and have at least eight different established physiological functions (131,(160)(161)(162).…”

Insect ion transport peptides are derived from alternatively spliced genes and differentially expressed in the central and peripheral nervous system

“…Comparison of genes, precursors and primary structures of ITPs and their distributions in the nervous system have revealed striking similarities to those of CHHs. The latter are major members of a large peptide family comprising CHHs with pleiotropic functions, and moult-, vitellogenesis-and gonad-inhibiting hormones with somewhat more restricted functions (Böcking et al, 2002;Chan et al, 2003;Chen et al, 2005;Keller, 1992;King et al, 1999;Lacombe et al, 1999).…”

“…(3) All CHHs and ITPs are C-terminally amidated, which may protect them from carboxypeptidase degradation. (4) N-terminal pyro-Glu, a modification known to protect peptides against aminopeptidase degradation, is a further important structural determinant that is clearly a distinctive difference between most CHHs and all hitherto known ITPs, with the exception of some shrimp CHHs (Chen et al, 2005). (5) The presence of aromatic amino acids (Phe or Tyr) in position 3 (or positions 2, 4 or 3 in dipteran ITPs) of the Nterminal putative α-helix appears to be a very conserved feature that is important for the biological activity of both CHHs and ITPs (Gu et al, 2000;Katayama et al, 2003;Katayama and Nagasawa, 2004;Mosco et al, 2008;Zhao et al, 2005).…”

“…(5) The presence of aromatic amino acids (Phe or Tyr) in position 3 (or positions 2, 4 or 3 in dipteran ITPs) of the Nterminal putative α-helix appears to be a very conserved feature that is important for the biological activity of both CHHs and ITPs (Gu et al, 2000;Katayama et al, 2003;Katayama and Nagasawa, 2004;Mosco et al, 2008;Zhao et al, 2005). (6) The highest consensus of amino acid identities or close similarities is restricted to a core structure of the first 40 or 41 amino acids, containing two out of five important characteristic structural motifs in CHHs and ITPs embraced by the probably conserved cystine-bound loops I and II (Chen et al, 2005;Drexler et al, 2007;Lacombe et al, 1999) (Fig. 1).…”

Mysid crustaceans as standard models for the screening and testing of endocrine-disrupting chemicals

“…Immunoassays have been developed to measure CHH in several decapod crustaceans (Chang, 2005;Chung and Webster, 2005), but no such assays are available for mysids. Recent molecular studies (Chen et al, 2005) have demonstrated that the amino acid sequence of CHH is highly homologous with the molt-inhibiting hormone (MIH), another product of the sinus glands in crustaceans, indicating possible involvement in the control of molting and reproduction (De Kleijn and Van Herp, 1998). While hormonal control of circulating glucose levels has been called one of the best studied subjects in the field of crustacean endocrinology (Medesani et al, 2004), its value as a biomarker of exposure to EDs in mysids needs development.…”