Occurrence of l- and d-Crustacean Hyperglycemic Hormone Isoforms in the Eyestalk X-Organ/Sinus Gland Complex During the Ontogeny of the Crayfish Astacus leptodactylus

Abstract

We studied the ontogeny of the eyestalk structure and of the L-CHH and d-Phe3-CHH synthesis in the X-organ/sinus gland (XO/SG) complex by light microscopy and immunocytochemistry in the freshwater crustacean Astacus leptodactylus. The optic ganglia start to differentiate in embryos at EI 190 microm (EI: eye index; close to 410 microm at hatching). At EI 270 microm, the three medullae (externa, interna, and terminalis) and the lamina ganglionaris are present and are organized as in the adult eyestalk. The L-CHH was localized in perikarya of neuroendocrine cells, in their tracts, and in SG from the metanauplius stage to the adult. The d-Phe3-CHH was visualized in XO perikarya, in their tracts and in SG of embryos from EI 350 microm and in all later studied stages. Co-localization of both CHH stereoisomers always occurred in the d-Phe3-CHH-producing cells. These results show that the synthesis of CHH enantiomers starts during the embryonic life in A. leptodactylus, and that the d-isomer is synthesized later than its L-counterpart. We discuss the post-translational isomerization as a way to generate hormonal diversity and the putative relation between d-Phe3-CHH synthesis and the ability to osmoregulate, occurring late during the embryonic life of Astacus leptodactylus.

The Crustacean Hyperglycemic Hormone Superfamily: Progress Made in the Past Decade

“…In particular, the hyperglycemic response kinetics are delayed with d -Phe 3 -CHH (3 to 4 h instead of 2 h for the L-isoform), and the amplitude of the hyperglycemic response is increased (10x higher for d -Phe 3 -CHH). Additional functional changes for d -Phe 3 -CHH were reported as having more potent inhibitory activity on the molting gland during ecdysteroidogenesis ( 65 ) or having a higher osmoregulatory activity ( 62 , 63 ).…”

The neuroendocrine system of invertebrates: a developmental and evolutionary perspective

“…Two other neurohemal structures, called the postcommissural and the pericardial organs, receive projections from NSCs in the brain and ventral nerve cord. A large variety of neuropeptides influencing pigmentation, carbohydrate levels, osmoregulation, growth/molting, and reproduction are released from each of these sites (Bulau et al 2004, Serrano et al 2004.…”

Hyperglycemic activity of the recombinant crustacean hyperglycemic hormone B1 isoform (CHH-B1) of the Pacific white shrimp Litopenaeus vannamei

“…However, multiple functions have been reported for CHH, including regulation of lipid metabolism [31], molting [6,7], osmoregulation [33,36], reproduction [9,42] and stress response [1]. The multiple activities have been explained as being due to the existence of CHH isoforms that may originate by various mechanisms, including the transcription of multiple copies of genes [13], alternative splicing of genes [10], or by post-translational processing such as L to D isomerization [34,35], and N-terminal blocking [5]. The CHH genes are classified into two types according their exon-intron organization: the type I genes that have 4 exons and 3 introns, and the type II genes that have 3 exons and 2 introns.…”