Members of the crustacean hyperglycemic hormone (CHH) peptide family are differentially distributed both between and within the neuroendocrine organs ofCancercrabs: implications for differential release and pleiotropic function

Abstract

Research on crustaceans has played a major role in advancing our understanding of neuroendocrine structure and control. Nearly 80 years ago, Koller (Koller, 1925;Koller, 1927) demonstrated that hemolymph-borne agents were responsible for color change in shrimp. In the decade that followed, Hanström (Hanström, 1931;Hanström, 1933;Hanström, 1935;Hanström, 1937) identified a structure located in the eyestalk, the sinus gland (SG) as the source of these substances. Later, Bliss (Bliss, 1951) and Passano (Passano, 1951) independently demonstrated the neurohemal nature of the SG, a first for any neural structure in the animal kingdom. In recent years, work from many laboratories has shown that the SG is one of the major neuroendocrine organs in crustaceans and a number of hormones contained within it have been identified, including a group of structurally related peptides that have collectively been termed the crustacean hyperglycemic hormone (CHH) family. The crustacean hyperglycemic hormone (CHH) family of peptides includes CHH, moult-inhibiting hormone (MIH) and mandibular organ-inhibiting hormone (MOIH). In the crabCancer pagurus, isoforms of these peptides, as well as CHH precursor-related peptide (CPRP), have been identified in the X-organ-sinus gland (XO-SG) system. Using peptides isolated from the C. pagurus SG, antibodies to each family member and CPRP were generated. These sera were then used to map the distributions and co-localization patterns of these peptides in the neuroendocrine organs of seven Cancer species: Cancer antennarius, Cancer anthonyi, Cancer borealis, Cancer gracilis, Cancer irroratus, Cancer magister and Cancer productus. In addition to the XO-SG, the pericardial organ (PO) and two other neuroendocrine sites contained within the stomatogastric nervous system, the anterior cardiac plexus (ACP) and the anterior commissural organ (ACO), were studied. In all species, the peptides were found to be differentially distributed between the neuroendocrine sites in conserved patterns: i.e. CHH, CPRP, MIH and MOIH in the XO-SG, CHH, CPRP and MOIH in the PO, and MOIH in the ACP (no immunolabeling was found in the ACO). Moreover, in C. productus (and probably in all species), the peptides present in the XO-SG and PO were differentially distributed between the neurons within each of these neuroendocrine organs (e.g. CHH and CPRP in one set of XO somata with MIH and MOIH co-localized in a different set of cell bodies). Taken collectively, the differential distributions of CHH family members and CPRP both between and within the neuroendocrine organs of crabs of the genus Cancer suggests that each of these peptides may be released into the circulatory system in response to varied, tissue-specific cues and that the POand/or ACP-derived isoforms may possess functions distinct from those classically ascribed to their release from the SG.

High-definition De Novo Sequencing of Crustacean Hyperglycemic Hormone (CHH)-family Neuropeptides

“…Thus, visualization of the CHHfamily peptide hormone release sites may provide insights into the neurosecretion and signal transduction pathways as well as complex hormonal integration of these processes. Many efforts have been directed to the use of immunohistochemical techniques for distribution analysis of the CHHfamily peptides in the neurosecretory system (9,14,15,45). In general, the immunoreactivities of subfamily-I peptides rarely overlap with those of subfamily-II peptides, but co-localization of individual isoforms among subfamily-II peptides has been observed.…”

“…The X-organ/sinus gland complex located in eyestalks represents a major neurodocrine structure in decapod crustaceans (10). Previous studies using immunohistochemical techniques for peptide profiling indicate that the subfamily-I peptides (CHH) rarely overlap with the subfamily-II peptides (MIH and MOIH) (9,14,15,45). However, the immunohistochemical method suffers from antibody cross-reaction problem as the epitope peptides share a high degree of sequence homology (see Fig.…”

“…However, the immunohistochemical method suffers from antibody cross-reaction problem as the epitope peptides share a high degree of sequence homology (see Fig. 6) (14). To overcome this limitation, we demonstrated the first use of MALDI MS imaging technique to map the endogenous CHH-family peptides in crustacean neurosecretory structures.…”

“…Crustacean hyperglycemic hormone (CHH) 1 family neuropeptides play a central role in energy homeostasis of crustaceans (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). Hyperglycemic response of the CHHs was first reported after injection of crude eyestalk extract in crustaceans.…”

Circadian clocks in crustaceans: identified neuronal and cellular systems

“…The Xorgan somata are located at the anterior lateral cortex of the medulla terminalis proximal to the hemiellipsoid body, and the sinus gland, which is usually situated adjacent to the medial edge between the medullae externa and interna, is formed by axonal endings of XOSG and other neurons that abut upon lacunae around the large ophthalmic artery. From these neurohaemal XOSG terminals several identified neuropeptides are released into the haemolymph, such as red pigment concentrating hormone (RPCH), crustacean hyperglycaemic hormones (CHHs), moult-inhibiting hormone (MIH), vitellogenesis/gonad-inhibiting hormone (VIH/GIH), and mandibular organ-inhibiting hormone (MOIH) (127)(128)(129)(130)(131)(132)(133). However, the sinus gland receives additional inputs from other regions of the eyestalk ganglia outside the XOSG and even from the brain (134)(135)(136).…”